Venice, March 2006 - Argo · Venice, March 2006 Welcome to the Second Argo Science Workshop. At the...

Venice, March 2006

Welcome to the Second Argo Science Workshop.

At the time of the fi rst Argo Science Workshop in Tokyo in November 2003, the Argo array consisted of 950 fl oats, with the great majority of them in the Northern Hemi-sphere. There were enormous gaps in coverage in all oceans. Nevertheless, that First Workshop brought together over 200 enthusiastic scientists who gave us an exciting glimpse into Argo’s enormous potential as a research tool.

In just over 2 years since the First Workshop, Argo has matured enormously. There are now over 2400 fl oats, 80% of the Argo target. More than half of these fl oats are in the Southern Hemisphere, and global coverage has been achieved. The Global Ocean has never before been observed as it is at the present time. While 10 years are needed to fully demonstrate the value of Argo, now is the time to explore the Argo array’s real capabilities (as well as its limitations).

The Second Argo Science Workshop is being held in conjunction with the symposium “15 Years of Progress in Radar Altimetry”. As Argo has now matured, it is appropriate to bring Jason and Argo together. Argo and altimetry are a powerful combination for observing the ocean surface topography and its subsurface causes. We hope the com-bined symposium and workshop mark the beginning of a long and successful partner-ship, providing critical data for climate research as well as for many other research and operational applications.

We would like to thank NOAA (USA) for providing fuding for the workshop and IOC for managing the travel funding component, to JAMSTEC (Japan) for printing the new Argo brochure that will be available in Venice and to CSIRO (Australia) for its artistic design. Webb Research Corporation kindly funded the printing of this programme.

Most importantly we thank the national Argo programmes, their funding agencies and scientists for enabling us to reach this important milestone in the development of Argo.

We wish you a pleasant stay and a scientifi cally stimulating time at the workshop.

Dean Roemmich Argo Steering Team Co-ChairmanHoward Freeland Argo steering Team Co-ChairmanJohn Gould Argo Director

Programme summary

Second Argo Science Workshop

Argo workshop presentations within the Integrated Approach session of “15years of Radar Altimetry” symposium.

Argo-related papers from this session are marked in bold type

Integrated approach - SystemsChairs J. Gould, D Roemmich

Wednesday March 15th0820 - 0840 The ECCO Near Real-Time Ocean Data Assimilation System Ichiro Fukumori, Benyang Tang, Zhangfan Xing, Dimitris Menemenlis, Ou Wang, Ichiro Fukumori, Benyang Tang, Zhangfan Xing, Dimitris Menemenlis, Ou Wang, Ichiro Fukumori Sophie Ricci 0840 - 0900 Synergy between ocean observations and numerical simulations : CLIPPER heritage and DRAKKAR perspectives Thierry PenduffThierry Penduff, Bernard Barnier, Anne-Marie Treguier, Pierre-Yves Le Traon Thierry Penduff, Bernard Barnier, Anne-Marie Treguier, Pierre-Yves Le Traon Thierry Penduff 0900 - 0920 Ocean Model Analysis and Predicition System (OceanMAPS): operational ocean forecasting based on near real-time satellite altimetry and Argo Gary BrassingtonGary Brassington,Graham Warren ,Tim Pugh ,Mikhail Entel ,Konstantin Belyaev , Eric Schulz ,Helen Beggs, Leeuwenburg Tennessee, Claire Spillman, Neville Smith 0920 - 0940 HYCOM Ocean Prediction and Altimeter Data Assimilation E. ChassignetE. Chassignet, H.E. Hurlburt, O.M. Smedstad, J. Cummings, H. Kang, C. Thacker, L. Parent, E. Chassignet, H.E. Hurlburt, O.M. Smedstad, J. Cummings, H. Kang, C. Thacker, L. Parent, E. Chassignet P. Brasseur, A. Srinivasan ,T. Chin, R. Baraille

0940 - 1000 Altimetry and Military Oceanography : a Common Destiny Didier Jourdan, Sylvie Giraud Saint-Albin, Eric Dombrowsky

1000 - 1020 The PSY3v1 GODAE/Mercator ocean forecasting system, a global eddy permitting (1/4°) ocean model assimilating altimetry data Marie Drévillon, Nicolas Ferry, Elisabeth Remy, Eric Dombrowsky, Nathalie Verbrugge, Stéphanie Guinehut, Corinne Derval, Edmée Durand, Gilles Garric, Benoit Tranchant,

, Mounir Benkiran, Eric Greiner, Jean-michel Lellouche 1020 - 1050 COFFEE

Integrated approach - DemonstrationsSession Chairs - P. Knudsen, Pierre-Yves Le Traon

1050 - 1110 Interpreting low frequency sea level signals over the last decade Rui Ponte,Sergey Vinogradov, Carl Wunsch

1110 - 1150 Mid-depth Circulation of the World’s Oceans: A First Look at the Argo Array Josh Willis, Lee-Lueng Fu 1150 - 1210 Altimetry, SST and ocean colour unveil the effects of planetary waves on phytoplankton Paolo CipolliniPaolo Cipollini 1210 - 1230 Mean surface circulation of the global ocean inferred from satellite altimeter and drifter data Nikolai Maximenko, Peter Niiler 1230 - 1250 Combining Altimetric and All Other Data with a General Circulation Model Carl Wunsch, Patrick Heimbach

1250 - 1400 LUNCH

Wednesday March 15 Morning

1

Integrated approach - DemonstrationsSession Chairs - P. Knudsen, Pierre-Yves Le Traon

1400 - 1420 Chlorophyll Bloom in the Western Equatorial Pacifi c During the 1998 El Niño / La Niña Transition: the Role of Kiribati Islands as Seen From Satellite, in-situ Data, and a High-Resolution Simulation Monique MessieMonique Messie, Marie-Hélène Radenac ,Jérôme Lefevre 1420 - 1440 Basin Scale Mass Variations in the Atlantic Ocean Saskia Esselborn, Tilo Schöne, Silvia Becker, Roland Schmidt 1440 - 1500 Results from the GOCINA project. Combining altimetric/gravimetric and ocean model mean dynamic topographies. Per Knudsen, and The GOCINA team 1500 - 1520 The MERSEA Project : Development of a European system for operational monitoring and forecasting of the ocean on global and regional scales. Yves Desaubies

1520 - 1540 Sea surface salinity from a simplifi ed ocean mixed layer model using global altimeter data Sylvain MichelSylvain Michel, Bertrand Chapron, Jean Tournadre,Nicolas ReulSylvain Michel, Bertrand Chapron, Jean Tournadre,Nicolas ReulSylvain Michel 1520 - 1540 Impact of Argo temperature and salinity measurements in the new ECMWF ocean analysis system, with focus on the interaction with altimeter data. Magdalena A. BalmasedaMagdalena A. Balmaseda, Arthur Vidard, David L.T. Anderson 1540 - 1610 COFFEE

Integrated approach - DiagnosticsSession Chairs - N Ferry and D.L.T. Anderson

1610 - 1630 Using altimeter measurements for quantitative assessment of high resolution ocean models LuAnne ThompsonLuAnne Thompson, Kathryn Kelly 1630 - 1650 Importance of TOPEX/Poseidon/Jason data to improve the coupled ocean-atmosphere modeling of El Niño Claire PerigaudClaire Perigaud, Jean-Philippe Boulanger, Serena Illig Claire Perigaud, Jean-Philippe Boulanger, Serena Illig Claire Perigaud 1650 - 1710 Ocean Surface Current Monitoring from Space: Methodology and Progress Fabrice BonjeanFabrice Bonjean, Gary Lagerloef, Eric Johnson, John Gunn, Laury Miller, Richard Legeckis ,Gary Mitchum, Nancy Soreide, Mark Bourassa 1710 - 1730 The Mercator 1992-2002 PSY1v2 ocean reanalysis for the tropical and North Atlantic Eric Greiner 1730 - 1750 Fifteen Years of Altimetry and Satellite Data: Benefi ts for Mercator-ocean Operational Forecasting System Nicolas FerryNicolas Ferry, Benoit Tranchant, Charles-Emmanuel Testut, Elisabeth Remy, Nicolas Ferry, Benoit Tranchant, Charles-Emmanuel Testut, Elisabeth Remy, Nicolas Ferry Marie Drevillon, Eric Greiner, Mounir Benkiran, Jean-Michel Lellouche, Pierre Brasseur

1800 - 1930 Integrated approach posters and cocktails

Wednesday March 15 Afternoon

2

Thursday March 16th • “15 years of Altimetry” - fi nal plenary sessions.

• Argo workshop Argo working group meetings.

Argo posters setup.

Friday March 17th

Argo Session 1 - Heat and salt

0820 - 0840 Introduction to Argo, GODAE and the WorkshopDean Roemmich, Howard Freeland, Pierre-Yves Le Traon, John Gould

0840 - 0900 Use of Argo data to detect and understand ocean climate change Richard Wood

0900 - 0920 Global heat and salt content observed with Argo profi les Fabienne Gaillard

0920 - 0940 How well is Argo measuring the steric component of global sea level? John Gilson, Dean Roemmich

0940 - 1000 How useful is Argo for investigation of interannual variability in the North Atlantic heat content? Rachel Hadfi eld,Rachel Hadfi eld, Neil Wells, Simon Josey

1000 - 1020 Decadal-Scale Temperature Trends in the Southern HemisphereSarah Gille

1020 - 1040 JASON and Argo reveal a decadal spin-up of the South Pacifi c gyreDean Roemmich,Dean Roemmich, John Gilson, Russ Davis, Phil Sutton, Susan Wijffels, Steve Riser

1040 - 1110 COFFEE

Argo Session 2 - Watermass changes

1110 - 1130 Generation and Initial Evolution of a Mode Water Theta-S Anomaly Gregory C. Johnson Gregory C. Johnson

1130 - 1150 Interannual changes in thermocline properties in the Indian Ocean B.A.KingB.A.King, E McDonagh

1150 - 1210 Observations of the Mode Water Formation and Evolution from the Kuroshio Extension System Study (KESS) Float Program Bo QiuBo Qiu, Peter Hacker, Shuiming Chen, Kathleen A. Donohue, D. Randolph Watts, Humio Mitsudera, Nelson G. Hogg, Steven R. Jayne

1210 - 1230 Study on the circulation and water masses in the Northwest Pacifi c Ocean Using Argo profi ling fl oats Xu JianpingXu Jianping, Liu Zenghong, Sun Chaohui, Zhu Bokang

1230 - 1250 The impact of profi ling fl oat data on the estimation of mean climatological temperature and salinity fi elds Tim BoyerTim Boyer, Sydney Levitus, John Antonov, Ricardo LocarniniTim Boyer, Sydney Levitus, John Antonov, Ricardo LocarniniTim Boyer 1300 - 1430 Lunch

Thursday/ Friday March 17/18

3

1430 - 1630 Posters + Coffee

Argo Session 3 - Ocean circulation

1630 - 1650 Estimating the time-averaged circulation of the North Atlantic Ocean Steven Jayne, Breck Owens, Bruce Cornuelle

1650 - 1710 Supply routes of eastern tropical Atlantic upwelling regions – shallow Argo Floats J. Fischer, F. Schott, B. RabeJ. Fischer, F. Schott, B. RabeJ. Fischer

1710 - 1730 Seasonal and interannual variability of temperature inversions in the subarctic North Pacifi c Hiromichi Ueno, Eitarou Oka, Toshio Suga, Hiroji Onishi

1730 - 1750 The circulation in the subtropical South Indian Ocean derived from Argo fl oats K. Getzlaff, H. Bryden, E. McDonagh, B. King.K. Getzlaff, H. Bryden, E. McDonagh, B. King.K. Getzlaff

1750 - 1810 The deep circulation in the Norwegian Sea from subsurface fl oats Kjell Arne MorkKjell Arne Mork, Henrik SøilandKjell Arne Mork, Henrik SøilandKjell Arne Mork

NOTES

Friday March 17 Afternoon

4

Saturday/18th

Final day of Argo Science Workshop

Session 4 Climate applications and operational use

0820 - 0840 Reconstructing estimates of ocean steric sea-level rise from sparse ocean data sets John A. Church, Catia Domingues, Neil J. White, Susan Wijffels

0840 - 0900 The impact of Argo temperature and salinity data on the NCEP Global Ocean Data Assimilation System (GODAS)

David W. BehringerDavid W. Behringer

0900 - 0920 Impact of Argo Profi les on Real-time Global Ocean Analyses for GODAE James A. CummingsJames A. Cummings

0920 - 0940 Data Assimilation Experiment of Argo fl oats to Quasi-Operational Ocean Prediction System around Korean Waters

Moon-Sik Suk, D. Bala SubrahamanyamMoon-Sik Suk, D. Bala SubrahamanyamMoon-Sik Suk

0940 - 1000 Assimilation of Argo data into ECMWF models: diagnostics of ocean transports and water mass variability Gregory C. SmithGregory C. Smith, Keith Haines, Arthur Vidard, David Anderson, Magdalena Balmaseda, Chunlei Liu, Alberto Troccoli

1000 - 1020 Role of assimilation of Argo data in the improvement of tropical Pacifi c Ocean simulationsEric Hackert, Joaquim Ballabrera-Poy, Antonio Busalacchi, Raghu MurtuguddeEric Hackert, Joaquim Ballabrera-Poy, Antonio Busalacchi, Raghu MurtuguddeEric Hackert

1020 - 1040 Observed characteristics at the eastern edge of the warm pool in the western Pacifi c Ocean C. Maes,C. Maes, K. Ando, T. Delcroix, W. S. Kessler, M. J. McPhaden,D. Roemmich

1040 - 1110 COFFEE

Session 5 The upper ocean

1110 - 1130 Argo measurements near the sea-ice margin. K. Speer, N. Wienders, C. Chien

1130 - 1150 Complementarities between ship-of-opportunity in situ surface salinity data and the Argo data Gilles Reverdin

1150 - 1210 Studying the zonal slope of thermocline using Argo and altimeter observations MM Ali,MM Ali, Uday Bhaskar, Muthulu Ravichandran

1210 - 1230 Seasonal variations of the upper ocean in the western North Pacifi c observed by an Argo fl oat Naoto Iwasaka, Fumiaki Kobashi, Yosuke Kinoshita, Yuko Ohno

1230 - 1250 What Proportion of the North Pacifi c Current fi nds its way into the Gulf of Alaska? Howard Freeland

1300 - 1430 LUNCH

5

Saturday March 18 Morning

1430 - 1630 Posters and Coffee

Session 6 New technologies and future prospects

1630 - 1650 Biogeochemical observations from profi ling fl oats - The Oxygen success story and more to come. A. KoertzingerA. Koertzinger, D. Gilbert, H. Freeland, S. RiserA. Koertzinger, D. Gilbert, H. Freeland, S. RiserA. Koertzinger

1650 - 1710 Towards an Hybrid Antarctic Float Observation System (HAFOS) Olaf Klatt, Olaf Boebel, Ismael Núñez-Riboni, Eberhard FahrbachOlaf Boebel, Ismael Núñez-Riboni, Eberhard FahrbachOlaf Boebel

1710 - 1730 Year-long measurements of rain and windspeed from Argo fl oats Stephen C. RiserStephen C. Riser

1730 - 1750 Labrador Sea convection and circulation of low-salinity waters tracked by Seagliders, Argo and Altimetry

Hjalmar HatunHjalmar Hatun, Charlie Eriksen, Peter Rhines

1750 - 1825 Discussion of the future of Argo

1825 - 1830 Closing remarks

6

Saturday March 18 Afternoon

NOTES

Studying the zonal slope of thermocline using Argo and altimeter observations

MM Ali1, Uday Bhaskar, Muthulu Ravichandran 1Oceanography Division, National Remote Sensing Agency, Balanagar, Hyderabad, India 500037

[email protected] Saturday 1150

After the onset of the Indian southwest monsoon, a jet of water fl ows from west to east along the equatorial Indian ocean (EIO) resulting in pilling up of water at the eastern end of the basin and changing the slope of the thermocline. Though slopes in SSHAs could be obtained from the accurate altimeter measurements, the associated changes in the thermo-cline could not be studied in detail due to the lack of dense in situ temperature measurements, particularly, in the EIO region. Deployment of Argo fl oats in the Indian Ocean gave an opportunity to study the seasonal changes in the thermo-cline in conjunction with altimeter observations.

Temperature profi les from Argo fl oats and the SSHAs from Jason during 2004 have been used to develop the relationship between the slopes in SSHA and the thermocline changes. A west to east upslope in SSHA is observed during May-July and again during November-December 2004, showing bimodal oscillations. The corresponding slopes in the thermocline are in the opposite direction. Up slopes (down slopes) in SSH and down slopes (up slopes) in thermocline are maximum during June (September) 2004. Variations in SSH and thermocline are large at the eastern end of the basin compared with the western end due to the pilling up of water at the eastern end and the associated changes in the thermocline. Using the relation between the two slopes, altimeter observations have been used to study the inter-annual and seasonal changes in the thermocline in relation to the monsoon phenomenon.

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Argo Workshop Abstracts submittedAlphabetical listing (ordered by submitting/presenting author)

Not all posters may be presented in Venice

Note - a small number of abstracts may be out of sequence if the presenting author changed after the programme was collated

Impact of Argo data assimilation in an Ocean General Circulation Model

Neeraj Agarwal1 , Rashmi Sharma, Sujit Basu, Abhijit Sarkar and Vijay K Agarwal1Meteorology and Oceanography Group

Space Applications Center, I.S.R.O.,Ahmedabad-380015, [email protected]

PosterIn this study global temperature and salinity profi les available from Argo have been assimilated into an Ocean General Circulation Model (OGCM). Argo is a global programme under which it is planned to deploy around 3,000 fl oats all over the globe that can provide temperature and salinity profi les at a spatial and temporal resolution of 3°X3° and 10 days respectively. OGCM used for the study is based on Modular Ocean Model –version3 (MOM-3) of Geophysical Fluid Dynamics Laborartory (GFDL), NOAA. The model is global in zonal direction and extends upto ±80° in latitude with a variable horizontal resolution from 0.5° to 2°. There are 38 vertical levels with 16 levels in top 110 meters. In the control run the model was forced with daily Quickscat derived scatterometer winds for the period Jan 2004- July 2005 and air temperature, specifc humidity, net short-wave and net long wave radiation from NCEP reanalysis. In another run called the “assimilation run” we assimilated global monthly averaged Argo temperature and salinity profi les for the period Jan 2004 – Dec 2004 in the OGCM. Since there are gaps in the Argo data therefore we used Levitus data as the background fi eld and blended the Argo data wherever available. The resultant fi eld was then assimilated into the OGCM using nudg-ing technique. Temperature and salinity from both (control and assimilation) the runs were compared with independent observations from TRITON buoys. Detailed analysis of the impact will be presented in the workshop

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7

The use of Argo fl oat data in a Bernoulli inverse of the North Atlantic

Steven Alderson, P. Challenor, S. Cunningham, P. Killworth, N. O’ReillyNational Oceanography Centre,, University of Southampton Waterfront Campus, European Way, Southampton,

SO14 3ZH, [email protected]

PosterArgo fl oat data have been used in a Bernoulli Inverse method to calculate the dynamic sea surface height of the North Atlantic at weekly intervals. The results have been tested against satellite altimeter data and model data with encouraging results. The method is currently being expanded to include altimeter data directly into the analysis. Work is also being undertaken to examine the errors involved in the scheme and to look at the possibility of the use of other conservation properties.

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Climatology and interannual variability of the North Atlantic from Coriolis re-analysis.

E. Autret1, F. Gaillard 1, T. Loubrieu 2

1Laboratoire de Physique des Océans, Ifremer, BP70, 29280 Plouzané France2Coriolis data center, Ifremer, BP70, 29280 Plouzané France

[email protected]

The Coriolis real time analysis system started operating in 2000 over the North-Atlantic. The dataset collected in real time and delayed mode during this 5 year period has been revisited and a re-analysis has been produced with the same analysis system. Temperature and salinity fi elds are reconstructed on a 1/3 degree grid, on more than 50 levels from surface down to 2000 m .From these fi elds, associated errors and datasets, we have computed a new climatology representative of the 2000-2004 period, along with updated elementary statistics. The use for those basic products is wide, ranging from automatic quality control to the tuning of numerical models.

The seasonal to interannual variability of the various region of the basin has been examined, and it appears that some long term signal is detected. Given the actual observing system, these products could easily been updated on an annual basis and extended to the world ocean. The dataset also allows estimation of higher order statistics. The large scale horizontal structure of the variability is extracted with principal component analysis while the more homogeneous meso-scale are described by the usual horizontal covariances.

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Seasonal evolution of the upper layer of the Antarctic Circumpolar Current south of Africa

Michel Arhan1, Sabrina Speich1, Isabelle Ansorge2, Sergey Gladyshev3

1 Laboratoire de Physique des Océans (Centre National de la Recherche Scientifi que, Institut Français de Recherche pour l’Exploration de la Mer, Université de Bretagne Occidentale), Brest, France.

2 Oceanography Department, University of Cape Town, Rondebosch, South Africa3 Shirshov Institute of Oceanology, Moscow, Russia

[email protected]

In the framework of the GOODHOPE project, over 30 Argo profi ling fl oats (PROVOR type) have been launched since 2004 in the oceanic region south of South Africa and to approximately 55°S. In conjunction with regular expendable bathythermograph (XBT) and Conductivity-Temperature-Depth (CTD) measurements , and in association with analyses of altimetric data, these fl oats have been launched with the aim of a better understanding and monitoring of the Indo-At-lantic oceanic exchange by both the highly turbulent fl ow of the subtropical region and the Antarctic Circumpolar Current (ACC) farther south. For the fi rst time the fl oats provide a year-round hydrographic sampling of this seasonally inacces-sible region.

The quality of the hydrographic profi les obtained by the fl oats has been compared/calibrated against available CTD mea-surements and the lateral (frontal) structure/dynamics of the ACC observed from the fl oat data are discussed in relation to the underlying bathymetry. The seasonal variations of surface and upper ocean properties have been analysed with particular emphasis on the heat and salt content of the surface mixed layer in the various ACC frontal zones.

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Delayed mode qualifi cation of Argo fl oats: CORIOLIS analysis system

E. Autret, F. GaillardLaboratoire de Physique des Océans, Ifremer, BP70, 29280 Plouzané France

[email protected]

Coriolis data center collects, checks for quality and distributes in real time a great number of global in situ data. Managed data sets are mainly temperature and salinity profi les from Argo fl oats, XBTs, CTDs, drifting and moored buoys. In order both to qualify the dataset and provide temperature and salinity analyzed fi elds a data analysis system based on optimal estimation methods has been developed. Using the measurements from the CORIOLIS data base the analysis computes temperature and salinity 3-D fi elds on 60 levels from the surface down to 2000 meters. In addition to the estimate of temperature and salinity at each grid point, the method calculates at each data point, a residual corresponding to the dif-ference between the estimate and the measurement there. A quality control tool based on the behavior of the residuals has been developed.

The operational system implemented is exploited in real time to produce global analyzed fi elds and to detect possible gross errors. In delayed mode, re-analysis are performed and a method using the statistical behavior of the residuals has been developed to detect possible sensor drifts or bias particularly for Argo fl oats. The method has been used to diagnose the behavior of the whole fl eet of Argo fl oats in the Atlantic. This test has shown that this operational method is a fast and easy mean to estimate offsets and to point out possible drifts. In this particular case, an expertise is needed to decide whether it is due to the analysis (inconsistency with climatology) or to a sensor drift and each case should be looked at individually and compared with other methods.

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8

Using Argo data to address oceanographic issues in the Eastern tropical Pacifi c

Daniel BallesteroLaboratorio de Oceanografía y Manejo Costero, Universidad Nacional, Heredia 3000, Costa Rica

[email protected]

The mainly zonal distribution of currents and properties prevailing in the central tropical Pacifi c is modifi ed in the eastern tropical Pacifi c (ETP). East of 120º W, the presence of the American continent and a wind fi eld with a strong meridional component result in complex upper layer circulations and thermal structures. The Costa Rica dome (CRD) and the gap wind jets at Tehuantepec, Papagayo and Panamá blowing on the ETP are the focus of renewed interest in the region. Two issues which are a matter of discussion are a) the role of wind forcing as a driving mechanism of the annual cycle of the CRD and b) the effect on the dome and on the structure of the upper layer of large, anticyclonic eddies generated by the Papagayo wind jet.Two autonomous ARGO profi ling fl oats were seeded in December 2005 at 9º N, 90º W (the center of the CRD) and 10º N, 87º W (the region were the wind stress curl and mixing due to the Papagayo wind jet are strongest). The data obtained from these profi lers during the 2005-2006 gap winds season are discussed.to the world ocean. The dataset also allows estimation of higher order statistics. The large scale horizontal structure of the variability is extracted with principal com-ponent analysis while the more homogeneous meso-scale are described by the usual horizontal covariances.

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Impact of Argo temperature and salinity measurements in the new ECMWF ocean analysis system, with focus on the inter-action with altimeter data.

Magdalena A. Balmaseda1, Arthur Vidard1 , David L.T. Anderson1

1ECMWF, Shinfi eld Park, Reading RG2 9AX, United [email protected]

Oral Wednesday 1610 The impact of temperature data from Argo fl oats in the ECWMF ocean analysis system was addressed in a previous study (Vidard et al 2005). No evaluation was made of the salinity information, since by the time of the study the ECMWF system did not have the capability of assimilating salinity. Besides the time period for the impact of Argo in this study was restricted to 2002-2003.

Recently, the operational ocean analysis system at ECMWF has been substantially upgraded, and both salinity data and sea level anomalies from altimeter are now assimilated together with subsurface temperature data. The new system is used to assess the impact of both temperature and salinity measurements from Argo by conducting observing system experiments (OSEs) during the period 2000-2005. The potential synergy between Argo and altimeter information is spe-cifi cally addressed in the experimental design.

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Argo fl oat observations of Antarctic Intermediate Water

Paul Barker1Paul Barker , Richard Karsten1, Howard Freeland2

1 Dept Maths and Stats, Acadia University, Wolfville, Nova Scotia, Canada.2 Fisheries and Oceans/Canada,P. O. Box 6000,Sidney, V8L 4B2, BC,Canada

[email protected]

Antarctic Intermediate Water (AAIW) is the low salinity water mass found between 800 and 1000 metres depth throughout most of the southern hemisphere and in the northern hemisphere tropics of all oceans. AAIW is primarily formed in the southeast Pacifi c, where the densest and freshest of the circumpolar deep mixed layers exist. The formation process occurs largely in the austral winter when the cool atmospheric temperatures and deep mixed layers are conducive to deep convection. Until now observations of the formation of AAIW has been extremely limited due to the prohibitive weather conditions during the austral winter. To address this shortcoming 6 Canadian fl oats were deployed off southern Chile close to the formation region of AAIW in December 2002, there are now over 100 fl oats in the Southeastern Pacifi c Ocean. In this presentation, we present our initial analysis of the data from the Southern Pacifi c Ocean fl oats. The data includes complete seasonal cycles allowing us to describe the hydrography of the region during the austral winter. And, we have also begun to identify water mass properties. We have determined the circulation pattern of AAIW in the South Pacifi c Ocean and are currently analysing how surface waters might waters might sink to depth to form AAIW.

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The impact of Argo temperature and salinity data on the NCEP Global Ocean Data Assimilation System (GODAS)

David W. BehringerNOAA/NCEP, Camp Springs, Maryland, USA


The Global Ocean Data Assimilation System (GODAS) provides near real-time operational analyses of the ocean state in at the U.S. National Centers for Environmental Prediction (NCEP) where it is used to initialize the ocean component of coupled seasonal to interan-nual climate forecasts. The GODAS is built on the GFDL Modular Ocean Model, Version 3, (MOMv3) and a three-dimensional variational assimilation scheme. In its operational confi guration, the GODAS assimilates temperature profi les from sources that provide data in near real-time (XBTs, TAO/TRITON/PIRATA moorings, Argo fl oats).

The GODAS also assimilates synthetic salinity profi les which are computed from each temperature profi le and the local T-S correlation. Here we report on the impact of the Argo fl oat network on the GODAS analyses. The Argo network has grown steadily over the last 5 years and in 2003 the number of Argo profi les used in each GODAS analysis exceeded the number of XBT profi les. With its relative freedom from the constraint of commercial ship tracks, salinity profi ling, and deep profi ling capability, the Argo network, however, is more than a simple replacement for the XBT network.

Using the standard GODAS, some reconfi gured versions of GODAS, and a CONTROL that assimilates no data, we will look at the im-pact of Argo on the GODAS in 3 ways. 1) Given the current availability of XBT profi les, what is the impact of withholding Argo profi les? Likewise, what is the impact of withholding XBT profi les? 2) What is the impact of replacing synthetic salinity profi les as used in the standard GODAS with observed Argo salinity profi les? 3) In the standard GODAS data are assimilated only into the upper 750 meters, a depth corresponding to the maximum depth of many XBT profi les. What is the impact of taking advantage of the greater depth of Argo profi les by extending the assimilation depth of GODAS to 1500 meters? All of the model results will be evaluated by cross-validation and comparisons with independent datasets.

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Distributions of mixed layer properties in North Pacifi c water mass formation areas: comparison of Argo fl oats and World Ocean Atlas 2001

Frederick M. Bingham1, Toshio Suga2

1UNC Wilmington, Center for Marine Science, 5600 Marvin K. Moss Lane, Wilmington, NC 28409, USA2Tohoku University, Department of Geophysics

[email protected]

Winter mixed layer (ML) characteristics in the North Pacifi c Ocean are examined and compared between Argo fl oats in 2004 and 2005 and the World Ocean Atlas 2001 (WOA01) climatology for a series of named water masses, North Pacifi c Tropical Water, Eastern Sub-tropical Mode Water (ESTMW), North Pacifi c Subtropical Mode Water, and Light and dense Central Mode Water (DCMW). The WOA01 is found to be in good agreement with Argo in terms of water mass volumes, average temperature-salinity (T-S) properties, and outcrop areas. The exception to this is for the central mode waters, especially DCMW, whose outcropping is shown to be much more intermittent than is apparent in the WOA01 and whose T-S properties are vary from what is shown in the WOA01. Distributions of ML T-S properties measured by fl oats are examined within the outcropping areas defi ned by the WOA01 and show some shifting of T-S characteristics. In 2005, all the water masses were warmer than climatology on average, with DCMW being highest at about 1oC. Similar results were found for the 2004 Argo data except ESTMW and DCMW which were slightly cooler than climatology. Differences between fl oat data and climatology were also examined for the entire North Pacifi c. This analysis showed the winter North Pacifi c ML to be fresher and warmer than climatology in both 2004 and 2005, with magnitudes of 0.3-0.4 degC and 0.06-0.07. This warming and freshening was apparent throughout a large area of the tropics and northeastern North Pacifi c, but in the mode water formation areas the trends were less clear.

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The impact of profi ling fl oat data on the estimation of mean climatological temperature and salinity fi elds.

Tim Boyer, Sydney Levitus, John Antonov, Ricardo LocarniniOcean Climate Laboratory/National Oceanographic Data Center, 1315 East-West Highway, Silver Spring, MD 201910, USA

[email protected]

Oral Friday 1230Profi ling fl oats have greatly expanded the spatial and temporal reach of subsurface oceanographic temperature and salinity data collection. We now have a source of data from geographic areas and seasons which were previously data sparse or never even sampled. This creates the possibility to enhance estimation of climatological fi elds for both temperature and salinity, leading to better initial and boundary conditions for models, among other benefi ts. But this also creates new problems in the estimation of climatological fi elds.All fl oat data has been collected within the last 11 years, the majority in the last 5 years. Climatologies could potentially be skewed toward values prevalent in the last 5 years, especially for salinity.Further, profi ling fl oats come with their own set of problems, including pressure hysteresis and salinity drift. The sheer amount of data coming in also presents challenges in quality assurance. We use the profi ling fl oat data from the last 11 years to perform some experi-ments to quantify the impact of profi ling fl oats on climatological mean fi elds of temperature and salinity. Further experiments use the delayed mode salinity data in climatologies to assess the impact of these data in comparison to the real time salinity. Finally, the ad-ditional quality control needed to prepare the profi ling fl oat data for use in climatological calculations is detailed. The data used are the fl oat data from the GODAE server, along with fl oat data available from the WOCE data set and from the GTSPP data set. Other data types are from the World Ocean Database.

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Ocean Model Analysis and Predicition System (OceanMAPS): operational ocean forecasting based on near real-time satellite altimetry and Argo

Gary Brassington1, Graham Warren 2 , Tim Pugh1, Mikhail Entel1 , Konstantin Belyaev1, Eric Schulz1 , Helen Beggs1 , Leeuwenburg Tennessee 2 , Claire Spillman1 , and Neville Smith1

1 Bureau of Meteorology Research Centre, 700 Collins Street, Melbourne, Australia 2Bureau of Meteorology, 700 Collins Street, Melbourne, Australia

[email protected] Wednesday 0900

BLUElink> is a joint Australian government initiative to develop Australia’s fi rst operational ocean forecasting system called OceanMAPS. The project has transitioned to the implementation and trial phase using the infrastructure of the Bureau of Meteorology. OceanMAPS has a global grid with 1/10 by 1/10 resolution in the Australian region (90E-180E, 70S-16N) and uses the Modular Ocean Model version 4 optimised for the NEC SX6. The analysis uses an ensemble based multi-variate optimal interpolation scheme where model error covariances are derived from a 72-member ensem-ble of intra-seasonal anomalies based on a 12-year ocean only model integration. The scheme has been formulated to assimilate near real-time sea level height anomalies processed from Jason-1, ENVISAT, Geosat Follow-On and Topex/Poseidon and profi le observations including Argo, XBT and the TAO array. The operational confi guration including the data management of the near real-time observations is reviewed. An analysis of the impact of altimetry and Argo on both the analysis and forecast skill of OceanMAPS during the operational trials is presented.

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Decadal-scale trend of the South Pacifi c circulation: a comparison between models and observations

Wenju CaiCSIRO Marine & Atmospheric Research, Aspendale, Vic 3195, Australia

[email protected]

Data from altimeter, Argo, and hydrographic sections reveal a spin-up of the South Pacifi c subtropical gyre circulation. The change is linked to the recent bias toward a high-index phase of the Southern Annular Mode, particularly the as-sociated trend in wind stress curl. The linkage means that the oceanic circulation change also refl ects the trends in the atmosphere circulation. This notion is explored using a well-established wind-driven circulation model. The result shows that all the major features of the ocean circulation trends are reproduced with the observed wind forcing, including a signifi cant sea surface height (SSH) rise in the west Pacifi c around New Zealand, a decreasing SSH trend in the eastern basin, and a decreasing trend in the central South Pacifi c 50°S. The reproduction of these changes suggests that the ocean measurements tell not only the oceanic circulation, but also the ocean-atmosphere coupling, the process of which is explored using a climate model. The results illustrate that thermal coupling is embedded in the wind fi elds, with a wind stress curl that is consistent with ocean-atmosphere heat exchange.

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3 Dimensional structure of the eastern South Pacifi c eddies from surface drifters, satellite altimetry and Argo profi lers

Alexis Chaigneau, Oscar Pizarro and Gérard Eldin.COPAS/PROFC, Cabina 7, Barrio Universitario, Concepcion, CHILE

[email protected]

Using distinct but complementary information from 25 years of satellite-tracked surface drifters, 12 years of altimetry measurements, and 5 years of Argo fl oats profi les, we investigate the mean structure of the mesoscale activity in the Pacifi c Ocean offshore Chile and Peru. The main eddy formation regions and their propagation modes are identifi ed through altimetry measurements. Their horizontal structure is studied combining surface Lagrangian drifters and satellite altimetry, whereas their mean vertical structure is computed from ARGO fl oats data. In particular we estimate the mean vertical temperature and salinity anomalies of the cyclonic / anticyclonic eddy cores, relatively to the surrounding water. This estimation provides useful metrics to evaluate lateral heat and salt eddy fl uxes from the coastal upwelling regions of the Eastern South Pacifi c to the ocean interior.

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Argo buoys deployments in the Eastern South-Pacifi c for the 2005-2007 period.Motivation –Technique - Deployment sites.

Alexis Chaigneau, Gérard Eldin, Osvaldo Ulloa, Oscar Pizarro and Samuel HormazabalCOPAS/PROFC, Cabina 7, Barrio Universitario, Concepcion, CHILE.

[email protected]

PosterThe Eastern South-Pacifi c (ESP) offshore Northern Chile and Peru is characterized by the presence of the most pro-nounced and extended oxygen minimum zone (OMZ) of the world ocean. Located at intermediate depths (<1000 m), this OMZ plays a crucial role on greenhouse gases (like CO

2 and N

2O) exchanges between the ocean and the atmosphere,

but also on the adaptation of the ecosystems to such an anoxic environment. The ESP also exhibits a complex three-di-mensional circulation and T-S structure, with the presence in the upper 2000 m of distinct water masses originating from equatorial, subtropical, subantarctic, and the Antarctic regions. Superimposed to these rather large-scale characteristics, the mesoscale activity is seen as an important factor for both the transfer of heat and salt from the offshore waters to the surface coastal layers, and for the offshore propagation of physical and biogeochemical properties from the coastal upwelling regions.

Despite its important physical and biogeochemical characteristics, the ESP is still relatively poorly sampled and badly known. In order to evaluate spatial distribution and variability of the OMZ and the water masses in the ESP, and to de-termine the vertical structure of the mesoscale eddies in this region, two independent but complementary international projects have led to funding of 30 Argo buoys. Some of these fl oats (16-20) will be equipped with Aanderaa optode oxy-gen sensors. The deployments will take place between the end of 2005 and 2007 at different sites offshore the Peruvian and Chilean coasts.

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Validation of numerical model in the Pacifi c Ocean with Argo data

You-Soon Chang, Chang-Woo Cho, and Yong-Hoon YounMarine Meteorology and Earthquake Research Laboratory Meteorological Research Institute,

Seoul 156-720, South [email protected]

PosterWe validated the ocean circulation model based on GFDL MOM3.1 using in-situ data including Argo fl oats. Time-lon-gitude diagram of the depth of the 20° isotherm (Z20) reasonably shows the interannual variability of the thermocline over the tropical Pacifi c. However, simulated Z20 is relatively low compared to that of observation. This result comes from the cold bias associated with the strong equatorial upwelling in the central and eastern Pacifi c. Another validation is the variability of subsurface zonal current in the equatorial ocean. Disappearance of equatorial undercurrent during the 1982-1983 strong El Niño coincides with the observation evidences. We also calculated the regional and seasonal T-S diagrams in North Pacifi c Ocean. Simulated water masses derived from T-S diagram are consistent with Argo data especially in the mid and low latitudinal areas. However, some discrepancies have been found, those are permanent low salinity (high temperature) in the mid (high) latitude regions and low salinity at surface layer around equatorial region in summer season. We will apply to various mixing schemes which were not considered in present study and higher grid resolution in order to solve the systematic model bias.

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Infl uence of Barrier Layer on Sea Surface Height Variability in Bay of Bengal

Kalyani Chikka1 , K.V Ramesh1 , and P.S Swathi1 C-MMACS, NAL Belur Campus, Wind Tunnel road, Bangalore 560 037, India

[email protected]

Studies have documented that the barrier layer formation may have signifi cant impact on air-sea interactions. The ad-vancements in the ocean in-situ observations, satellite based observations and ocean modelling provides us an opportu-nity to investigate the infl uence of barrier layer formation on the SST and heat content variability on seasonal and intran-nual time scales. The satellite altimetry has opened a new dimension for monitoring the variability of the Sea Surface Height (SSH) without the assumption of level of no motion. SSH can be used as a proxy to understand the upper ocean heat content variability. Bay of Bengal is typically marked with fresh water fl ux and heavy rainfall and also convective mixing due to surface cooling cause the fresh water to mix down to the top of thermocline, thus disturbs the barrier layer. Due to the formation of barrier layer we can observe changes in the subsurface temperature and salinity on intraseasonal to seasonal time scales.

Hence we made an attempt to understand importance of barrier layer formation on SST variability. To study these fea-tures on various scales we have analysed Topex/Poseidon derived Sea Surface Height (SSH), TMI derived SST and satellite derived precipitation. Along with the above data we have used high resolution OGCM simulations for the years 1997-2004. In this study we have observed that the barrier layer signifi cantly affects SST and the heat fl ux. These results are validated with few Argo observations.

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Delayed Mode Quality Control on Argo fl oats at the Coriolis Data Center

Coatanoan C., Galaup P. & V.ThierryCoriolis Data Center, IFREMER DOP/DCB/IDM/SISMER, Centre de Brest - BP 70, FRANCE - 29280 PLOUZANE

[email protected]

PosterA remote calibration method is required to correct salinity sensor drifts by using hydrographic reference database. At the Coriolis data center, the Wong et al method, adapted by Böhme and Send, has been applied to the North Atlantic envi-ronment to produce delayed mode dataset; a large coordination has taken place between the PI and the data center to study the results of the method. Since this application has been done on some fl oats older than two years, it appears that some of them show offsets or drifts, at least for the latest cycles. Most of them can be easily corrected from the DMQC method, but from this fi rst experience, we can mention that when the fl oat shows an irregular behaviour, specially when a signifi cant drift appears, we need to apply specifi c procedures. Some statistical results will present the ratio of correc-tions applied to the fl oat of the North Atlantic Ocean. Extrapolations of correction for the real time data will be analyzed. Complementary diagnostic plots have been also developed at the Coriolis Data Center to compare DMQC results with temperature and salinity residuals and fi elds of the objective analysis. In an other way, to be able to properly apply the Wong-Böhme method, a major point is to have a relevant reference dataset, which should be supplied by the CTD carried out during the fl oat deployment.

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Transport variation of currents in the Northwestern Pacifi c Marginal Seas

Yang-Ki Cho1 and Yong-Hoon Youn2

1. Faculty of Earth System and Environmental Sciences, Chonnam National University, Gwangju, 500-757, Korea.2. Meteorological Research Institute, Korea Meteorological Agency, Seoul, 156-720, Korea

[email protected]

Regional Ocean Model System was used to simulate water temperature, salinity and current in the Northwestern Pacifi c Marginal Seas. Model has fi ne resolution (0.1 degree by 0.1 degree) and 20 vertical sigma levels. Historical temperature and salinity data were used for initial and open boundary data. Bulk parameterization was adopted for surface heat fl ux.

Model simulated well the paths of the Kuroshio and major currents in the Northwestern Pacifi c Marginal Seas. Vertical profi les of temperature calculated by model were verifi ed by comparing those of Argo profi les and historical data. Calcu-lated volume transports of the Korea Strait, the Taiwan Strait, the Tsugaru Strait, and the Kuroshio show similar feature in temporal variation with observed transports. The transport of the Korea Strait shows two maximum. The transport of the Kuroshio drops in October. Data assimilation with Argo profi les and satellite data will be applied to improve predictive ability for the temperature and currents in the study area.

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Reconstructing estimates of ocean steric sea-level rise from sparse ocean data sets

John A. Church1,2, Catia Domingues1, Neil J. White1,2 and Susan Wijffels1

1CSIRO Marine and Atmospheric Research2Antarctic Climate and Ecosystems Cooperative Research Centre2Antarctic Climate and Ecosystems Cooperative Research Centre2


Ocean thermal expansion is an important component of sea-level rise. Estimates of ocean thermal expansion for the last fi ve decades have been produced from the comparison of individual sections, objective mapping of historical data sets and ocean reanalysis experiments. However, the combination of the available estimates of ocean thermal expansion and other contributions to sea-level rise have not adequately explained the observed sea-level rise estimated from tide gauge data.One potential explanation is that current ocean thermal expansion estimates are biased because of sparse data cov-erage, particularly in the southern hemisphere. Reduced space optimal interpolation techniques have been used for reconstructing historical sea surface temperature, atmospheric pressure and sea-level time series. We are developing procedures for applying reduced space optimal interpolation to sparse oceanographic data sets of steric height.Initial results for the post 1993 period will be presented and compared to other estimates for this period.

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Quality Control of Pre-Argo World Ocean Circulation Experiment Profi ling Float Data

Yeun-Ho Daneshzadeh 1, Elizabeth Forteza 2 and Robert Molinari 1

1 NOAA,AOML, Miami, Florida U.S.A, 2 University of Miami,CIMAS,Miami, Florida [email protected] Poster

Profi ling fl oats were deployed in the Atlantic, Pacifi c and Indian Oceans as a component of the World Ocean Circulation Experiment (WOCE). WOCE fl oat data were collected north of 6°S in the Atlantic Ocean, throughout the Indian Ocean, in all 3 ocean basins south of 30°S, and in the Northeast Pacifi c Ocean from 1994 to 2001. The majority of the fl oats were deployed in the Atlantic Ocean as part of the Atlantic Circulation and Climate Experiment (ACCE). The internationally coordinated Argo project has developed a uniform quality control procedure for the profi ling fl oat data collected during this more recent experiment. The WOCE data were edited using the Argo protocols to provide a uniformily edited data-set of profi ling fl oats beginning in 1994 andcontinuing to the present. The 44,037 WOCE profi les were fi rst reviewed using the 18 automatic quality control (QC) tests developed for Argo. There were 38,135 (87%) profi les which passed and 5,902 (13%) profi les that failed the automatic tests. The next step in the Argo quality control procedure is to have an operator inspect those profi les that failed an automatic test. There were 829 (1.9%) profi les that passed the visual quality control. Thirty fi ve percent (15,474) of the fl oat observations included both temperature and salinity profi les. Of these fl oats, 11,108 profi les were suitable for the fi nal step in the quality control applied. This step involves using a statistical compari-son of the salinity profi les to other hydrographic data to correct for any drift in measurements..

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Coriolis a French project for operational oceanography

C Coatanoan1, T Carval1, L Petit de la Villéon1, E Autret1, Y Gouriou2

1Ifremer, Brest2IRD, L Gourmelen SHOM

[email protected]

The seven French agencies concerned by ocean research are developing together a strong capability in operational oceanography based on a triad including satellite altimetry (JASON), numerical modelling with assimilation (MERCA-TOR), and in-situ data (CORIOLIS).

The CORIOLIS project aims to build a pre-operational structure to collect, validate and distribute ocean data (temperature/salinity profi les and currents) to the scientifi c community and modellers. CORIOLIS aims at four goals: • To build up a data management centre, part of the ARGO network for the GODAE experiment, able to provide quality-controlled data in real time and delay modes. • To contribute to Argo fl oats deployment mainly in the Atlantic with about 300 fl oats during the 2001-2005 period. • To develop and improve profi ling Provor fl oat as a contribution to Argo. • To integrate into CORIOLIS other data presently collected at sea by French agencies from surface drift ing buoys, PIRATA anchored buoys, oceanographic research vessels (XBT, thermosalinograph and ADCP transmitted on a daily basis).

In 2005, recommendations will be done to transform the CORIOLIS activity into a permanent, routinely contribution to ocean measurement, in accordance with international plans that will follow the Argo/GODAE experiment.

**********Impact of Argo Profi les on Real-time Global Ocean Analyses for GODAE

James A. CummingsNaval Research Laboratory, Monterey, California 93943


In the absence of in situ data at depth, subsurface properties in the ocean must be inferred from surface-only measure-ments. The most important observing system for this purpose is satellite altimetry. Assimilation of altimeter sea surface height anomalies (SSHA) in real-time systems is typically done using one of two alternative methods: (1) assimilation of temperature profi les computed using climatological relationships between SSHA and temperature at depth derived from the historical profi le archive (synthetic BT method), or (2) correction of the model forecast density fi eld using differences between the model SSHA fi eld and the SSHA fi eld measured by the altimeter (direct method based on Cooper-Haines)..

In this study, Argo profi le data are used to quantify the advantages and disadvantages of the two assimilation methods. Synthetic temperature-salinity (TS) profi les computed using Argo profi le SSHA and altimeter SSHA at the fl oat loca-tion and sampling time are compared with the Argo TS profi le to determine skill of the synthetic BT method. Skill of the direct method is investigated by comparing Argo fl oat density corrections computed using differences between SSHA from successive Argo cycles and analyzed altimeter fi elds with the TS profi le from the next cycle of the fl oat. The Argo and analyzed altimeter SSHA differences are used as proxies for model error, and the initial Argo fl oat profi le provides a perfect model forecast for the direct method. Regional and global results from the comparisons of the altimeter assimila-tion methods will be discussed. The impact of the source of the SSHA predictor variable (altimeter or in situ) is used to diagnose some limitations of altimeter SSHA to infer subsurface TS properties. These limitations are directly related to the impact of assimilating Argo profi les in real-time ocean forecast systems being implemented as part of GODAE.

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15

The MERSEA Project :Development of a European system for operational monitoring and forecasting of the ocean on global and regional scales.

Y.Desaubies and the MERSEA ConsortiumIFREMER, BP 70,, 29280 Plouzané,, France


GMES (Global Monitoring for Environment and Security) is a joint initiative of the European Commission and the European Space Agency, designed to establish a European capacity for the provision and use of op-erational information for Global Monitoring of Environment and Security. To support the development of the Ocean and Marine Applications component of GMES, the EC is funding the MERSEA integrated project.The system is based on the assimilation of remote sensing (altimetry, sea surface temperature, sea ice) and in situ obser-vations (Argoand XBT profi les) into high resolution ocean models. The project includes research and development activi-ties on data products, ocean modelling, assimilation, nesting and downscaling, ecosytems, and seasonal forecasting.The project federates the European contribution to the GODAE. It intends to contribute to the development of integrated core ocean services in Europe. The system design includes a global, as well as four regional components (Nordic, Bal-tic / North sea, North East Atlantic, and Mediterranean seas) which provide ocean analyses and forecasts in real time through assimilation of in situ and satellite data. The essential variables are the temperature, salinity and velocity fi elds, but research efforts are underway to include bio-geochemical and ecosystem variables. The input data and forcing fi elds are provided by dedicated Centres. The whole system is linked through an Information Management System.The overarching objective is to provide an integrated service of global and regional ocean monitoring and fore-casting to intermediate users and policy makers in support of safe and effi cient offshore activities, environmen-tal management, security, and sustainable use of marine resources. Some forty agencies, laboratories and institutions participate in the research and development effort of this four year project, which started in 2004.The project is oriented towards applications, and the delivery of products and services in support of marine safety and offshore industry, marine meteorology, wave forecasts and ship routing, oil drift fate prediction, seasonal forecasting, research, and reporting to public bodies. The system is also intended to deliver boundary conditions and data to coastal operational systems.Since October 2005, the system has been upgraded to its vesion V1, and an intensive pre-operational test period will be run for six months.We will present an overview of the system design and preliminary results from this Target Operational Period, from the point of view of validation and assessment of the quality of the outputs

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Monitoring the NW Mediterranean using coupled biogeochemical-physical platforms

Fabrizio D’Ortenzio1, Katarzyna Niewiadomska1, Hervé Claustre1, David Antoine1, Pierre Testor2

1. Laboratoire D’Océanographie de Villefranche, Université Pierre et Marie Curie et CNRS, Villefranche sur Mer, France 2. LOCEAN-IPSL, Université Pierre et Marie Curie et CNRS, Paris, France

Poster [email protected] The recent development of miniaturized low-energy sensors capable of retrieving several bio-geochemical or bio-optical parameters (i.e. chlorophyll, POC, CDOM, Oxygen) have been made available for integration on autonomous platforms. Future sensors could include parameters such as nutrients.In the framework of the French project PROGLO, some of these sensors will be integrated on two different autonomous systems: gliders and profi ling fl oats. These platforms will be deployed in the NW Mediterranean, where a physical and biological sampling station has been active since 1991 (DYFAMED) and a bio-optical buoy has been in operation since 2002 (BOUSSOLE).The main objectives of the observation system is the simultaneously acquisition of high temporal and spatial resolution bio-geochemical data and their derivatives for the purpose of: 1. establishing an operational monitoring system of the bio-geochemical dynamics of the area

2. evaluating the feasibility of an Argo-like system for bio-geochemical studies3. calibrating and validating Ocean Color satellite data4. determining the link between vertical distribution of biomass and its surface signature, as observed from space.

In this presentation, of the operational in situ system is described and some preliminary results obtained from pilot tests are shown

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Operational multivariate assimilation of satellite and in situ observations in the Mediterranean Forecasting System

Srdjan Dobricic,Nadia Pinardi, Marina Tonani, Claudia Fratianni, Mario Adani and Alessandro BonazziIstituto Nazionale di Geofi sica e Vulcanologia,, Via Creti 12, 40128 Bologna, Italy

Poster [email protected] Mediterranean Forecasting System (MFS) is an integrated operational activity in the Mediterranean which combines observations, data assimilation and forecasting. Since September 2004 the MFS has deployed 23 Argo fl oats in the Mediterranean. In the same period it started to use a new oceanographic model set-up based the 1/16th degree and 71 vertical layers ocean general circulation model combined with a multivariate optimal interpolation scheme. The system produces daily analysis of oceanographic parameters by assimilating satellite observations of sea surface temperature and sea level anomalies, and in situ observations of vertical profi les of temperature and salinity made by XBT and Argo fl oats. The presentation will describe the MFS assimilation system and demonstrate the impact of the multivariate as-similation of satellite and in situ observations on the quality of MFS analyses and forecasts.

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16

The PSY3v1 GODAE/Mercator ocean forecasting system, a global eddy permitting (1/4°) ocean model assimilating altimetry data

Marie Drévillon, Nicolas Ferry , Elisabeth Remy , Eric Dombrowsky, Nathalie Verbrugge, Dr. Stéphanie Guinehut , Corinne Derval, Edmée Durand, Gilles Garric, Benoit Tranchant, Mounir Benkiran, Eric Greiner, Jean-michel Lellouche

Mercator-Ocean, 8-10 rue hermès, 31520 Ramonville St Agne, [email protected]

Oral Wednesday 1000The Mercator-Ocean eddy permitting global ocean Prototype System (PSY3v1), assimilating satellite altimetry data, is

the french contribution to the GODAE project for the global ocean, and the MERSEA project for operational systems, and is operated weekly since the end of 2005 to deliver oceanic forecasts of two weeks. The system has a 1/4° horizontal resolution and 46 levels on the vertical (ORCA025), and is forced with daily surface fl uxes from ECMWF operational analyses, and constrained with JASON, ERS and GFO altimetry measurements from january 2005 up to real-time. Due to its fi ne resolution, the assimilation system provides an integrated description of the ocean with a realistic description of the meso scale features. Assimilation scores are presented, and independant in situ data of the Atlantic, Pacifi c and Antarctic ocean basins are contrasted with the simulation results in order to provide an estimation of the performances of the system. The results are also compared with the Levitus climatology, and with the 2003 ARMOR weekly products, which optimally combine satellite (SST, SLA) and in-situ (T/S profi les) near real time observations.

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Basin Scale Mass Variations in the Atlantic Ocean

Saskia Esselborn, Tilo Schöne, Silvia Becker, Roland SchmidtGFZ Potsdam, Telegrafenberg, 14473 Potsdam, Germany


Variations in oceanic mass are on the one hand related to changes in ocean dynamics and on the other hand to changes in the global freshwater-cycle. Until recently it has not been feasible to derive this quantity on large spatial scales from measurements. Nowadays it can be obtained by the reduction of steric from total sea level changes as well as by the analysis of temporal changes in the gravity fi eld. In this study space-based Altimeter (ERS-2, Topex and Jason) and in-situ Argo data (CORIOLIS project) are combined to derive monthly mass related sea level variations in the Atlantic Ocean for the period 2000 to 2005. From 2002 onward the global mass redistributions have been monitored by the GRACE sat-ellites. An independent estimate of monthly mass variations in the Atlantic Ocean is generated from the latest time series of monthly GRACE-only gravity models in the Atlantic Ocean processed at GFZ Potsdam. After adequate spatial fi ltering the two data sets are compared and the advantages and disadvantages of the two approaches are identifi ed. Typical temporal and spatial scales of these data and the relationship between steric and mass related sea level variations are further investigated for the Atlantic Ocean.

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Argo in West Africa: Implications for regional understanding of sea surface temperature and related weather patterns

Regina FolorunshoNigerian Institute for Oceanography and Marine Research,, Victoria Island, Lagos, Nigeria

[email protected]

Sea Surface Temperature (SST) variabilities in West Africa play important roles in the meteorological processes. Specifi -cally, sea surface temperatures variabilities are known to play important roles in the prevalence of upwelling and weather patterns in the dry and wet seasons however, there is paucity of SST data to allow the spatial and seasonal understand-ing of upwelling and weather parameters in West Africa. While several sea surfaces temperature observing stations like insitu moored buoys, research cruises and individual programmers have collected SST data in the region over time, most of the data lack regional and long-term series mode. The Argo programme is a new programme that could provide a long term and spatial coverage of the region and hence ensure better understanding of upwelling, weather and other related metocean processes. Such a programme could improve the paucity of data and lead to a better understanding of upwell-ing, and seasonal changes in weather parameters like rainfall and air temperature in the region.

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Supply routes of eastern tropical Atlantic upwelling regions -- shallow Argo Floats

J. Fischer, F. Schott, B. RabeLeibniz-Institut fuer Meereswissenschaften (IFM-GEOMAR), Duesternbrooker Weg 20, D-24105 Kiel, Germany

jfi [email protected] Friday 1630

The shallow circulation of the tropical Atlantic is investigated by a combination of shipboard observations (velocity and watermass characteristics), of moored current records and by using profi ling fl oats (Argo) drifting at 200m and 400m depths, respectively. The fl oats follow characteristical routes from the western boundary to the central and eastern re-gimes of the tropical Atlantic, with the off-equatorial undercurrents playing an important role. Sensor performance of the shallow fl oats will also be addressed.

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What Proportion of the North Pacifi c Current fi nds its way into the Gulf of Alaska?

Howard FreelandFisheries and Oceans/Canada,, P. O. Box 6000,, Sidney, V8L 4B2,BC, Canada


This paper builds on methods previously developed to show how the absolute (non-geostrophic method) circulation of the Gulf of Alaska can be observed using the Argo armada of fl oats. A time series of maps of the monthly circulation pat-terns in the Gulf of Alaska allows us to determine how much water is carried from the North Pacifi c Current and thence into either the Gulf of Alaska or the California Current System. This is of interest because of previous suggestions that fl uctuations in the Alaska Current and the California Current might be anti-correlated. It will be shown that roughly 60% of the water arriving off the west coast of the Americas in the N. Pacifi c Current eventually fl ows into the Gulf of Alaska, the remaining 40% fl owing into the California gyre. Fluctuations in the N. Pacifi c Current do occur, but the dominant response is a simultaneous strengthening of both the Alaska and California Currents. A signifi cantly smaller fraction of variance in N. Pacifi c Current fl ow results in a change in the fraction of water supplied to either gyre.

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Variation of the South Pacifi c Tropical Water in an ocean data assimilation system (MRI-MOVE) and its relation to ENSO.

Yosuke Fujii, Satoshi Matsumoto, Shiro Ishizaki, Tamaki Yasuda, Masafumi KamachiMeteorological Research Institute, 1-1 Nagamine, Tsukuba, Ibaraki, 305-0052 Japan.

[email protected]

Multivariate Ocean Variational Estimation (MOVE) System is an ocean data assimilation system developed in Japan Meteorological Agency/ Meteorological Research Institute (MRI). MOVE system can reproduce a faithful salinity fi eld because coupled temperature-salinity EOF modes are employed in its 3DVAR analysis scheme. In MOVE system, Argo fl oat and Satellite altimetry data, as well as in-situ observation data, are assimilated into MRI Community Ocean Model (MRI.COM). An assimilation experiment using MOVE System is performed between 1993-2004.

We examined the variation of the South Pacifi c Tropical Water (SPTW) in the NINO4 region (2S-2N, 160E-210W) us-ing the assimilation product and found that SPTW plays an important role in ENSO. The amount of SPTW increases in the cold (La Nina) phase because of intensifi ed vertical circulation induced by the equatorial upwelling. The increase of SPTW is accompanied by the increase of subsurface heat content because SPTW is relatively warm. SPTW, together with the fresh water on it, also forms a stable barrier layer and helps the rise of near-surface temperature. Then, the warm (El Nino) phase starts. In the warm phase, the opposite chain happens and, fi nally, it shifts back to the cold phase. It should be emphasized that the role of SPTW proposed here implies importance of salinity observations with Argo fl oat for understanding the ENSO mechanism.

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The ECCO Near Real-Time Ocean Data Assimilation System

Ichiro Fukumori, Benyang Tang, Zhangfan Xing, Dimitris Menemenlis, Ou Wang, Sophie RicciJPL/Caltech, M/S 300-323, Pasadena, CA 91109, United States

[email protected]

Oral Wednesday 0820Products of the ECCO Sequential Ocean Data Assimilation System (http://www.ecco-group.org/las) consists of near-global ocean state estimates from 1993 to present. These results are being utilized in diverse studies of ocean circulation and in geodetic applications. This presentation will describe the estimation system, the skill of its estimates, its latest improvements, and future outlook.

The on-going near real-time estimation system is based on an approximate Kalman fi lter and Rauch-Tung-Striebel smoother (partitioned, reduced-state, time-asymptotic approximations), and assimilates altimetric sea level and in situ temperature profi les with uncertainty in time-variable wind forcing as model control. The model is based on the MIT general circulation model with a variable 0.3 to 1-deg spatial resolution in a near global domain (73S to 73N). Estimates are statistically self-consistent and are in closer agreement with independent observations than a non-constrained model simulation.

Various improvements to the operational system are being developed. These include expansions to the model control space, such as time-invariant errors (bias) and diabatic sources of model error. A higher resolution system is also being developed to explore estimation of meso-scale variability in an eddy-permitting global circulation model.

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Canadian oxygen measurements on Argo fl oats

D. Gilbert, H. FreelandDirection des Sciences Océaniques, Institut Maurice-Lamontagne, Pêches et Océans Canada

850 route de la Mer, Mont-Joli, Québec, Canada, G5H [email protected]

PosterThe unprecedented spatial coverage of the Argo array offers the opportunity to measure other oceanographic parameters for which reliable sensors with low power requirements can be mounted on the fl oats. In 2004, Canada deployed four APEX fl oats equipped with Aanderaa’s optode oxygen sensor : one in the northwest Atlantic Slope Water, one in the Lab-rador Sea, and two in the Gulf of Alaska. We will report on nearly two years of oxygen data from these fl oats, discussing issues of sensor response time.

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Global heat and salt content observed with ARGO profi les

Fabienne GaillardIFREMER, BP 70,, 29280 Plouzané,, France

[email protected] 0900 Friday

The Argo array has now reached 2/3 of its nominal extent, giving acces to global synthetic views. We have initiated a study of the heat and salt budget. Preliminary evaluations of the time evolution of the heat and salt contentare underway. Two methods are implemented: the eulerian calculation, based on analyzed fi elds, and the lagrangian method where computations are performed along a profi ler trajectory. These in-situ observations will be compared with the surface fl uxes.

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Consistency of the delayed-mode Argo dataset

P. Galaup, V. Thierry, S. Guinehut, P.Y Le Traon, E. Autret, F. Gaillard, C. CoatanoanIfremer - Centre de Brest, DOPS/LPO, BP70, 29280 Plouzane cedex, France

[email protected]

Argo data center provide delayed-mode data in applying the delayed-mode procedure, as defi ned in the last Argo quality control manual. The procedure is based on a statistical tool that compares Argodata to hydrographic reference database. Complementary tools are used to help discriminate between real ocean events and sensor drifts and offsets. Although the correction proposed is based on an objective method, the fi nal correction may be subjective as choices have to be made by the delayed-mode operators and the PI responsible of the fl oat. Here we investigate ways to verify the consistency of the delayed-mode Argo dataset.

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The circulation in the subtropical South Indian Ocean derived from Argo fl oats

K. Getzlaff, H. Bryden, E. McDonagh, B. King,National Oceranography Centre, Southampton, SO14 3ZH, UK

[email protected] Friday 1730

This study uses CTD profi les from Argo fl oats between 2001 and 2004 to compute the circulation in the subtropical South Indian Ocean. All fl oat data have passed the Argo real-time tests and have been visually checked on the temperature-salinity relationship and changes of salinity anomaly on isotherms. Relative geostrophic transports are computed using geopotential anomalies with a zero-velocity surface (ZVS) at 2000dbar. Weighted 5degree-bin averaging represents the structure of the subtropical gyre reasonably well and the estimated strength of the relative transport is 54 +/- 12 Sv. Pre-limnary results indicate interannual oscillation in the gyre strength at 32S over the period 2002 to 2004. Additionally, mean velocity fi elds computed at the fl oats parking depth from fl oat trajectories using a linear regression highlight the strong zonal currents associated with the Subtropical Front (STF) and the Subantarctic Front (SAF) south of 38S, the western boundary current near the south-eastern tip of Africa as well as a slower northwestward return fl ow of the subtropical gyre.More appropriate mapping techniques using generalized distance weighting on varying length-scales and the combina-tion of the mean velocity fi elds from the fl oats drift at parking depth will reduce the errors and uncertainties in the velocity fi eld and enable us to compare results from different relative geostrophic transport calculations.

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18

Decadal-Scale Temperature Trends in the Southern Hemisphere

Sarah GilleScripps Institution of Oceanography, UCSD, 9500 Gilman Drive, La Jolla, CA 92014, USA


Fewer ocean temperature observations have been collected in the Southern Hemisphere than in the Northern Hemisphere during the last 50 years, which has made long-term temperature trends diffi cult to evaluate. For the Southern Hemisphere in particular, temperature profi les collected by Argo and profi ling ALACE fl oats provide an important benchmark against which temperature trends in the upper 1000 m of the ocean can be assessed. In this analysis, temperature observations collected from bottle data, CTD observations, XBTs, profi ling ALACE fl oats, and Argo fl oats are intercompared using 1990s observations as a reference. Each observation is compared with all other observations collected within a specifi ed geographic radius, and regions with no observations are assumed to have trends similar to well-sampled regions. Differ-ent temperature measurement methods are largely in agreement in the 1990s, though XBTs tend to appear slightly warm and profi ling ALACE fl oats slightly cold; these differences may refl ect biases in spatial and temporal sampling patterns. Overall, results show that the upper 1000 m of the Southern Ocean have warmed substantially since the 1930s period at all depths. Warming signals are pronounced within the Antarctic Circumpolar Current, which may indicate that the ACC has migrated southward or that heat has been input to the system.

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Eddies and Mean Flow in the Antarctic Circumpolar Current

Sarah GilleUniversity of California San Diego, 9500 Gilman Dr., MC 0230, La Jolla, CA 92037, United States

[email protected]

The Antarctic Circumpolar Current (ACC) is a multi-jet fl ow that encircles Antarctica, providing a Southern Ocean connec-tion between the Atlantic, Indian, and Pacifi c Ocean basins. Exact repeat altimeters are highly successful at identifying eddy variability, and in the Southern Ocean they have clearly demonstrated that strong eddy variability is associated with the ACC. Altimeter observations by themselves do not distinguish the time invariant geoid from time invariant features of the dynamical ocean circulation, so efforts to study the mean fl ow of the ACC have proved more diffi cult than studying the eddies themselves.

Since the fi rst altimetric studies, a number of strategies for studying mean circulation have been explored. One strategy is to assume that the ACC consists of meandering jets with Gaussian velocity profi les and to use an iterative process to reconstruct an estimated mean fl ow. This method can work well near large meandering jets but fails in places where jets do not meander and cannot capture large-scale background mean fl ows. A second strategy is to infer the mean sea surface height from hydrographic atlas data by determining dynamic topography relative to a known ``level of no motion’’. This method can prove problematic in the Southern Ocean where recent in situ estimates have suggested that bottom velocities are as large as 2 to 4 cm/s. New satellite geoid observations (from GRACE) and new dynamic topography es-timates developed from autonomous ALACE and Argo fl oats now offer alternate strategies for assessing the large-scale mean fl ow of the ACC and its interactions with eddies, although these means offer coarser spatial resolution than mean-dering jet models. Thus merged sea surface height maps may ultimately need to combine aspects of a variety of different strategies. Altimeter-derived estimates of the mean ACC have shown the current to be strongly steered by topography with enhanced eddy variability in regions of strong topography. Newer data will allow these analyses to be refi ned to demonstrate more completely the interactions between eddies and mean fl ow in the ACC

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Estimating Eddy Heat Flux from Argo and ALACE Float Data

Sarah T. Gille, Brian S. ChinnScripps Institution of Oceanography, UCSD, 9500 Gilman Drive, La Jolla, CA 92023, USA

Posters [email protected] combination of velocity and temperature information from Argo fl oats can provide an estimate of mid-depth heat transport in the ocean. Since fl oat velocities represent averages over 10 days, they do not resolve high-frequency com-ponents of eddy heat fl uxes. Here we have used acoustically-tracked fl oat data from 16 experiments carried out in the North Atlantic to evaluate the feasibility of estimating eddy heat fl uxes from fl oats.

Daily fl oat observations were bin averaged in 2° by 2° by 200 db deep geographic bins, and eddy heat fl uxes were esti-mated for each bin. Results suggest that eddy heat fl uxes can be highly variable, with substantial outliers and that fl uxes do not converge quickly. If 100 statistically independent observations are available in each bin (corresponding to 500 to 1000 fl oat days of data), then results predict that 80% of bins will have eddy heat fl uxes that are statistically different from zero.

Pop-up fl oats, such as ALACE and Argo fl oats, do not provide daily sampling and therefore underestimate eddy heat fl ux. The fraction of eddy heat fl ux resolved using pop-up fl oat sampling patterns decreases linearly with increasing intervals between fl oat tracking and can be modeled analytically. This implies that fl ux estimates from pop-up fl oats may be cor-rectable to represent true eddy heat fl ux. The results are used to obtain a preliminary global estimate of eddy heat fl ux.

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How well is Argo measuring the steric component of global sea level?

John Gilson, Dean RoemmichSIO, UCSD, 9500 Gilman Drive, La Jolla,, CA 92093, USA

Oral Friday 0920

A major challenge for global change research is to separate the steric and eustatic components of sea level variability. This decomposition is important both for understanding the present state of the climate system as well as for improving forecasts of future sea level rise. The aim of the present work is to evaluate Argoxs ability to estimate both the thermo-steric and halosteric sea level change on a month-to-month basis. The Argo array achieved sparse global coverage in early 2005, and is presently delivering about 6000 profi les per month from all of the oceans. We estimate the 2005 annual cycle and errors, for both the regional and global mean steric height of the sea surface relative to 2000 dbar. Errors are estimated in several different ways: based on subsampled datasets, on intrinsic noise levels due to mesoscale variability, and by using altimetric height to assess sampling errors. The adequacy of Argoxs present sampling and of its real-time data stream are addressed with respect to the present application and its extension to interannual variability. Finally, steric height and altimetric height annual variability are examined for consistency with published estimates of annual vari-ability in eustatic sea level from the GRACE mission.

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How altimetry can complement insitu observations in the estimation of the upper ocean heat storage.

Gustavo Goni, Claudia SchmidNOAA/AOML/PHOD, 4301 Rickenbacker Causeway, Miami, FL 33149, USA

[email protected] Poster

The main objective of this study is to improve the estimates of the upper ocean heat storage, which is key to achieve a better understanding of the heat balance in the world oceans.These estimates are necessary to improve climate forecast capabilities of coupled general circulation models. The data we use cover the years 1992 through 2005. Temperature profi les, approximately 150,000, are obtained from XBTs and profi ling fl oats. The altimeter data consist of the gridded AVISO sea height anomaly fi elds. The correlation between the sea height anomaly and the depth of the mixed layer and of selected isotherms is investigated in the upper 800m. The sea height anomaly fi elds are used to monitor the upper ocean heat storage within a two layer reduced gravity approxima-tion where these correlations are good.We present here global maps of altimeter-derived upper ocean heat storage and the errors associated with these es-timates obtained from the XBT and profi ling fl oat observations. The fi nal goal of this work will be to fi ll with altimetry estimates the spatial gaps created where profi ling fl oat coverage is not adequate. Moreover, this work will also provide information on where more in-situ observations are needed because altimetry cannot be used as a proxy to estimate the mixed layer depth or the upper ocean heat storage.

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Estimation of MLD from Argo data over the north Indian Ocean.

K C Gouda and and P Goswami,CSIR C-MMACS, NAL BELUR, Bangalore-37, India

[email protected]

The Mixed Layer Depth (MLD) at ten locations covering Arabian Sea and Bay of Bengal is estimated using the vertical temperature profi les obtained from Argo buoy data by gradient method during June 2003. The MLD so obtained is then compared with the MLD value obtained using the PWP 1D Model and it is found that the values obtained from two meth-ods are nearly equal and both maintains a good correlation.

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Assimilation of MEDARGO fl oat positions in a OPA model of the Mediterranean Sea

Annalisa Griffa, V. Taillandier, P.M. Poulain, K. BerangerCNR/ISMAR, Italy, RSMAS, Miami, FL (US)

[email protected]

The assimilation of fl oat positions is challenging mostly because of the nonlinear relationship between the observed vari-able, i.e. the positions, and the model variable to be corrected, i.e. the Eulerian velocity. This problem has been recently addressed introducing an appropriate observation operator and testing the method with synthetic data using the twin experiment approach (e.g. Molcard et al., 2003, Taillandier et al., 2005).

Here we present an improvement of the method and a fi rst example of application to in situ MEDARGO fl oats in the North Western Mediterranean Sea, using a 1/16 of a degree OPA model (Beranger et al., 2005). The velocity fi eld at the level of the fl oat drift (350m) is corrected, and the correction is statistically projected in the water column balancing the mass variables using geostrophy and mass conservation. The results show stable and signifi cant corrections of all the variables, consistent with the observations. The results are very promising, since they provide direct information on the velocity in the water column which can be considered complementary to the altimeter information.

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The Bluelink Ocean Forecast System

David Griffi n, Peter R Oke, Andreas SchillerCSIRO Marine and Atmospheric Research, GPO Box 1538, Hobart, Tas 7001, Australia

David.Griffi [email protected]

Bluelink is an Australian partnership between CSIRO, the Commonwealth Bureau of Meteorology and the Royal Australian Navy. The main objective of Bluelink is to develop an ocean forecast system for the mesoscale circulation around Australia. To this end, the Ocean Forecasting Australia Model (OFAM), a global confi guration of MOM4.0 with 0.1 degree resolution in the Australasian region (90E-180E, and 75S-16N), has been confi gured. The Bluelink Ocean Data Assimilation System (BODAS) is an ensemble optimal interpolation system that assimilates observations of sea level, temperature and salinity into OFAM. A preliminary assessment of the system’s performance has been undertaken through the Bluelink ReANalysis (BRAN) experiment that covers the period 1992-2004 and assimilates altimetric sealevel (ERS, Envisat, T/P, Jason and GFO) andtemperature and salinity profi les (Argo, WOCE, TAO and other).

Comparisons between BRAN fi elds and withheld observations demonstrate that the system can produce realistic results. Through a series of experiments, we have endeavoured to determine i) whether the present ocean observing system is suffi ciently comprehensive to adequately constrain our ocean model using our assimilation method, and ii) the relative importance of the surface and sub-surface observations. The fi rst operational forecasts using the Bluelink system are scheduled for 2006.

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Impact of the assimilation of Argo data in North Atlantic MERCATOR Ocean Forecasting System

Stephanie Guinehut, Mounir Benkiran, Gilles LarnicolCLS / Space Oceanography Division, 8-10 rue Hermes, Parc Technologique du Canal, 31520 Ramonville Saint-Agne, FRANCE

[email protected]

The North Atlantic MERCATOR Ocean Forecasting System is used to analyze and quantify the impact of the ARGO ob-serving system. The MERCATOR system is based on the OPA primitive equation OGCM with 43 levels on the vertical and a 1/3° horizontal resolution. It assimilates simultaneously altimeter sea level anomalies (Jason-1, Envisat, GFO), in-situ temperature and salinity profi les (Argo, XBT, CTD, moorings ) and sea surface temperature (RTG-SST) using a multivari-ate optimal interpolation method. The system is updated every week with the newly collected real-time observations to deliver oceanic forecasts of two weeks, since January 2004. Three experiments have been performed in order to quantify the impact of Argo data. The fi rst one assimilates all observations (satellites and in-situ), the second one assimilates only satellites observations as the third one assimilates only the in-situ profi les.

Then, global statistical analyses based on the forecast/observations misfi t have been performed in order to estimate the impact and the complementarity between the different observing systems. Additionally, the changes in circulation, mean eddy kinetic energy, heat transport and also thermohaline structure have been studied for the three experiments.

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Role of assimilation of Argo data in the improvement of tropical Pacifi c Ocean simulations

Eric Hackert, Joaquim Ballabrera-Poy, Antonio Busalacchi, and Raghu MurtuguddeEarth System Science Interdisiplinary Center, 2227 CSS BLD. (BLD 224), College Park, MD 20842-2465, United States

[email protected]

Oral Saturday 1000A series of data assimilation experiments is used to investigate the impact of Argo data to constrain tropical Pacifi c dynamics and thermodynamics of the reduced-gravity, sigma-coordinate, ocean model of Gent and Cane (1989). In these experiments, subsurface data (Tz, Sz) are assimilated with satellite-derived fi elds of sea level (SL), obtained from TOPEX/Poseidon/Jason1, and sea surface temperature (SST) from Reynolds and Smith (1994). Observations are as-similated using a Reduced-Order Kalman Filter (ROKF) algorithm method built on the multivariate EOFs of the model. These MEOFs statistically project the information of the data correction to all the variables of the model including salinity. This study focuses on the added value of Argo data with respect to conventional subsurface data (XBT, CTD, BATHY, and other instruments) from the Global Temperature-Salinity Profi le Program (GTSPP) database. In this manner, the relative contribution of Argo versus other subsurface observations (both Tz, Sz) can be isolated.

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How useful is Argo for investigation of interannual variability in the North Atlantic heat content?

Rachel Hadfi eld, Neil Wells and Simon JoseyNOC, Empress Dock, Southampton, SO14 3ZH, UK

[email protected]

Oral 0940 FridayThe usefulness of the Argo dataset for estimating the annual cycle and interannual variability in the North Atlantic Ocean Heat Content (OHC) is investigated. The work carried out involved subsampling a model temperature fi eld to the Argo sampling density and then using an optimal interpolation (OI) scheme to obtain a gridded temperature fi eld. OHC was calculated from the subsampled, interpolated and full model temperature fi elds. Comparison between the two OHCs indicates errors.

It was found that away from regions of high mesoscale activity, complex bathymetry and low sampling density, the change in mixed-layer OHC was accurate to about 2 Wm-2. However, within the Gulf Stream region, north of 50°N and south of 25°N, errors were in excess of 15 Wm-2. In these areas Argo cannot be used to investigate interannual variability in OHC since the errors are the same magnitude as expected variability. An experiment was undertaken to determine the critical number of fl oats required to reduce errors to less than 10 Wm-2 at each 2° grid point. The relationship between RMS differences and buoy numbers was found to be complicated, with dependence on length scales used in the OI and the distribution of the fl oat profi les. An additional experiment, which tested the sensitivity of the interpolated fi eld to the cor-relation parameters revealed the result was insensitive to selected parameters in areas of low errors. This suggests that in such areas we can be confi dent in the results even though the statistics of the fi eld are essentially unknown.

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Salinity variability on depth levels, isotherms and isopycnals. Statistical studies of historical and Argo data with signifi -cance for data assimilation

Keith Haines, Jean-Philippe Drecourt; Gregory SmithEnvironmental Systems Science Centre, University of Reading, 3 Earley Gate, Reading, RG6 6AL, UK

[email protected]

We look as spatial and temporal variance and covariance of salinity data from WOA2001 and recent Argo data. The variability is considerably different when referencing to depth levels, isotherms and isopycnals. This variability changes considerably in different parts of the ocean depending on the dominant factors controlling stratifi cation. The accuracy and quality control procedures for salinity data also impact on these calculations. The implications for data assimilation methods are considered.

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Direct estimation of geostrophic velocity from Argo fl oats and its verifi cation

Shigeki Hosoda, Shinya Minato, Tsuyoshi OhiraIORGC/JAMSTEC,, 2-15, Natshushima-cho, Yokosuka, Kanagawa, 237-0061,Japan

[email protected]

We have estimated geostrophic velocity refered to 2000db directly from almost simultaneous Argo fl oats triplets having temperature, salinity and pressure down to 2000db. Also the estimation error to this vector can be calculated from least square method.Each 10 days, many triangles are formed by now in the whole Pacifi c Ocean due to increasing deployment of the fl oats.The condition to make fl oat triangle will be discussed to get a suitable large scale circulation for the Pacifi c. Further, we compared the direct estimation of geostrophic velocity with that from gridded value of the mapping of the OI based on 2000db. They show good correspondence on the magnitude and direction.

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Capture of seasonal variability of temperature and its spatial distribution using Argo fl oats data

Shigeki Hosoda, Shinya Minato, Nobuyuki ShikamaIORGC/JAMSTEC,, 2-15, Natshushima-cho, Yokosuka, Kanagawa, 237-0061,Japan

[email protected]

We can capture seasonal temperature variation in the mid-depth ocean in Argo profi le data themselves and in the monthly temperature mapping of the OI with Argo fl oats, shipboard CTD and the TRITON buoy data. In some profi les of Argo fl oats, the signal like seasonal variation can be seen in the mid depth (from below the thermocline to 2000db). Further investigation of its characteristics shows that it corresponds well with the signal in the surface layer. Correlation analyses show the same results.

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Salinity impacts and balance correction of wind stress and sea surface height in MRI-MOVE system.

Shiro Ishizaki, Satoshi Matsumoto, Yosuke Fujii, Toshiyuki Sakurai, Takashi Yoshida,Tsurane Kuragano and Masafumi KamachiOffi ce of Global Environment and Marine Department, JMA,, 1-3-4 Otemachi, Chiyoda-ku, Tokyo, Japan

[email protected]

Japan Meteorological Agency/Meteorological Research Institute (MRI) has developed an ocean data assimilation system called MOVE (Multivariate Ocean Variational Estimation) System. MOVE system assimilates in-situ (ship and Argo) tem-perature and salinity, and satellite altimetry data into MRI Community Ocean Model (MRI.COM).

One of the advantages of MOVE system is that salinity as well as temperature fi elds are estimated by employing coupled temperature-salinity EOF modes in its 3DVAR analysis scheme, resulting to realistic expression of the ocean state. We implemented a reanalysis experiment in the global ocean from 1993 to 2004 using MOVE system. In the experiment, we examined the impact of the analysis of salinity fi eld to the result of the ocean data assimilation and found that salinity estimate is indispensable to reproduce realistic density and hence velocity fi eld.

The other advantage is a balance correction of wind stress fi eld. Along the equator, zonal wind stress is mainly balanced with zonal pressure gradient. In many ocean data assimilation system, however, it is often seen that zonal pressure gradient calculated from temperature and salinity fi eld after assimilation is not balanced with zonal wind stress derivedfrom atmospheric reanalysis data, and this imbalance causes spurious vertical circulation along the equator. Using MOVE system, we evaluated this balance, and corrected the zonal wind stress fi eld. We succeeded to suppress the spurious circulation and to improve the reanalysis product.

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Seasonal variations of the upper ocean in the western North Pacifi c observed by an Argo fl oat

Naoto Iwasaka, Fumiaki Kobashi, Yosuke Kinoshita, and ,Yuko OhnoTokyo University of Marine Science and Technology, Faculty of Marine Technology, Etchujima 2-1-6, Koto-ku, Tokyo 135-8533,

[email protected]

Oral Saturday 1210A seasonal evolution of surface mixed layer in the western North Pacifi c around 24°N between 143°E and 150°E was observed by using an Argo fl oat for more than 9 months, from December 2001 through August 2002. The result showed that the mixed layer was gradually deepened in the fi rst two months. It reached its maximum depth of about 130m in the end of January. Then the mixed layer varied largely and sometimes the pycnocline was very weakened until the summer mixed layer formed in late April. The thin surface mixed layer was maintained in the rest of the observation period. Heat content analysis suggested that the vertical heat advection was one of the most dominant terms in the heat balance in the upper layer. When subtracting the vertical heat advection term from the heat balance, monthly mean surface heat fl ux and the horizontal heat advection could account for the residual. It was discussed that the vertical motions that account for the major portion of the heat balance.

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Delayed Mode Correction for Argo Salinity Data in North West Pacifi c Based on WJO and BS Methods

Fengying Ji , Zhang AijunNational Marine Data and Information Service, China, 93# Liuwei Rd., Hedong District, Tianjin, China

[email protected]

Based on WJO and BS methods, the correction of Argo salinity data in North West Pacifi c are calculated. Because the historical dataset and the temperature levels, which are selected for calibration, are all different, the calibration of the sa-linity data and the calibration error are some kind of different. Based on the shipboard CTD casts near the fl oats to evalu-ate the calibrated salinity, the result shows besides the historical data are critical for the correction, the thermal-lag of the Argo fl oat must be taken into consideration for the calibration because different sampled direction between Argo fl oats and shipboard CTDs. More knowledge of the region ocean will also improve the DM correction of the Argo salinity data.

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Statistics of Property of Ocean Surface Mixing Layer

Mizuho Hoshimoto and Takashi YoshidaJapan Meteorological Agency, 1-3-4, Otemachi,, Chiyoda-ku,, Tokyo, 100-8122, Japan

[email protected]

Statistics are made from the World Ocean Database 2001 and Argo profi le data. Based on the statistics, the properties of ocean surface mixing layer for each sea area and season are described.

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Generation and Initial Evolution of a Mode Water Theta-S Anomaly

Gregory C. JohnsonNOAA/PMEL, 7600 Sand Point Way NE Bldg. 3, Seattle, WA 98115 USA


Generation and evolution of an isopycnal potential temperature-salinity (Theta-S), or spiciness, anomaly is studied around 20-23S, 110W in the austral winter of 2004. Two profi ling CTD fl oats deployed in the region in January 2004 pro-vide the observations. The anomaly (defi ned relative to water properties of the preceeding summer) is quite large (initially about 0.25 in S and 0.9C in Theta). It is associated with winter ventilation of a thick, low potential vorticity layer known as South Pacifi c Eastern Subtropical Mode Water. Regional lateral Theta and S distributions at the surface predispose the ocean to formation of this water mass, and allow signifi cant anomalies to be generated there with relative ease. The water mass is potentially important for climate in that, after northwestward advection in the South Equatorial Current, it contributes to the Equatorial Undercurrent and eventually resurfaces in the cold tongue of the eastern equatorial Pacifi c. The anomaly studies is strong enough to predispose a portion of the water column to salt fi ngering, increasing vertical mixing. While lateral processes are doubtless important in the evolution of the anomaly, the vertical mixing appear suf-fi ciently vigorous to reduce it signifi cantly within six months after its formation by spreading it to denser horizons through diapycnal fl uxes. By that time the anomaly is most likely suffi ciently diffuse so that subsequent evolution from diapyncal fl uxes is signifi cantly reduced as it makes its way toward the equator.

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Combination of Topex/Jason and Argo data in deriving Dynamic height variability of Arabian Sea - A promising approach

Sudheer Joseph1, Howard Freeland2

1 Indian National Centre for Ocean Information Services, Hyderabad, India2 Institute of Ocean Sciences, Sidney, British Columbia, Canada

[email protected],[email protected]

Satellite altimetry is able to measure the ocean surface height with an accuracy better than 5 cm, which is the sum of the marine geoid and the sea level variations due to oceanic processes. However ge-oid uncertainties hamper the accurate derivation of dynamic height form the satellite. In this paper we pro-pose a method for using Argo derived mean dynamic topography (MDT), in derivation of absolute dy-namic topography which is useful in describing the monthly circulation and major eddy fi elds of ArabianSea for the period of 2004 and 2005.

We carried out a step by step fi tting of the fi rst 20 empirical orthogonal functions derived from the Topex/ Ja-son SSH data (2000 -2005) and the Argo derived dynamic height anomalies(DHA) and used this relationship toderive the basin scale anomalies. The estimated DHA accounts for a mean 81% and maximum of 93% variance of the observed DHA for 2004 and 87% and 98% respectively for 2005, which clearly shows the improvement in the estimation due to the increased number of fl oats available in 2005. We present derived maps of dynamic topography by adding the Argo derived MDT and the estimated DHA for the period of 2004-2005 with error estimates. The maps are able to capture seasonal variability of the major eddy fi elds and circulation features of Arabian Sea.

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Clustering of Argo Float Data

Richard KarstenDepartment of Mathematics and Statistics, Acadia University

[email protected] PosterThe large amount of data that the Argo fl oats supply allows for the use of a variety of statistical tools to examine the physi-cal properties of the worlds ocean. In particular, using principle component and clustering techniques, we can identify water masses that share similar variability. For the fi rst time, the Argo data allows us to examine both geographical and temporal variability of water at intermediate depths. These techniques are used to examine the characteristics of water masses in the Southern Ocean, in particular Antarctic Intermediate Water.

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Interannual changes in thermocline properties in the subtropical Indian Ocean

B.A.King and E McDonaghNOC, Empress Dock, Southampton, SO14 3ZH, UK

[email protected] Oral Friday 1030

In March 2002, a transoceanic hydrographic cruise at 32S in the Indian Ocean revealed changes in Mode Water proper-ties since the previous occupation of the section in 1987. Salinity had increased on isotherms warmer than 10C, with a maximum salinity change exceeding 0.04 at the 13C isotherm in the western part of the basin. Argo fl oats deployed dur-ing the cruise confi rmed that the change was consistent over a large region in the SW Indian Ocean. Data reported by the fl oats during the subsequent 3 years show that fl oats are capable of monitoring the changes with interannual resolution. There was further increase in salinity during 2002 and 2003, but a levelling off during 2004

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Towards an Hybrid Antarctic Float Observation System (HAFOS)

Olaf Klatt, Olaf Boebel, Ismael Núñez-Riboni, and Eberhard FahrbachAlfred-Wegener-Institut, Bussestrasse 24, D-27570 Bremerhaven, Germany


The Argo system is expected to become the backbone of a global ocean observing system. However, it can not be easily extended into polar oceans, since the fl oats have to return to the sea surface to be located and to transmit the measured data. Since location and data transmission under the ice is only possible by acoustic means, an observation system in the deep polar oceans requires the combination of different technologies. The envisioned system comprises ice avoid-ing profi ling subsurface fl oats which are acoustically ranged by RAFOS technology. In a fi rst step they transmit the recorded data only when they are able to reach open water in real-time, in a second phase, they provide delayed mode data transfer during the ice-free season. Acoustic real-time data transmission is planned as fi nal step. Here we report on our efforts to develop an acoustically positioned, ice-sensing fl oats featuring delayed mode data transfer (iStore).

Since 1999 92 autonomous, profi ling fl oats were deployed in the Weddell gyre area. Since 2001 these fl oat have been registered with ARGO, forming a contribution of 61 fl oats in total. Since 2002, fl oats use the Ice Sensing Algorithm (ISA), which determines likeliness of ice coverage based on upper ocean temperatures. Of 18 ISA equipped fl oats 14 resur-faced after the fi rst winter season while 11 of 13 resurfaced after the fi rst and the second winter seasons. All of those sur-viving the fi rst winter survived the second winter as well. A total of 20 fl oats are equipped with RAFOS receivers. Sound coverage for the RAFOS navigation system is provided by 3 sound sources installed since 2003 (2 refurbished in 2005) and 3 sources installed in 2005. Sound coverage varies according to season, location and sound source manufacturer, though a value of 400 km can be safely assumed for planning purposes

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Circulation over the Mid-Atlantic Ridge in the North Atlantic as inferred from Argo Data.

Birgit Klein, Peter Koltermann, Gunda WieczorikBundesamt fuer Seeschifffahrt und Hydrographie (BSH), Bernhard-Nocht-Str. 78, 20359 Hamburg, Germany

[email protected]

Between 1998 and 2005 a set of Argo drifter has been deployed in the North Atlantic in the transition area between the subtropical and subpolar gyre. The drifter have mainly been deployed along the former WOCE line A2 and cover the Mid Atlantic Ridge (MAR) area. Surfacing positions of the fl oats are used to obtain the fl ow fi eld at 1500 m. The circulation on both sides of the ridge is following f/h contours closely. Over the ridge the average velocities are extremely small (< 1cm/s). Crossing of the ridge between the western and the eastern basin is restricted to the various fracture zones in the MAR. A strong interannual variability is noted in the selection of these fracture zones. Water mass properties over the ridge also show strong interannual variability in the Central and Mediterranean Water. The T/S properties from the fl oats are compared to the WOCE climatology and show negative anomalies during 1998-2000, followed by positive anomalies up to 2003. Timeseries from 3 moorings across the MAR are investigated to how these are related to changes in the position of the North Atlantic Current.

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Estimation of the average life span of Argo fl oats

Taiyo KobayashiIORGC (Institute of Observational Research for Global Change), JAMSTEC (Japan Agency for Marine-Earth Science and

Technology), 2-15 Natsushima-cho, Yokosuka, 237-0061, [email protected]

PosterThis study determined the average life span of Argo fl oats using a type of survival analysis commonly used in medical statistics. Based on data from 2839 fl oats in the Global Data Archive Center of Argo Project, the average life span of a profi ling fl oat is 110 measuring cycles. However, that average varies widely by fl oat type: Apex fl oats work through 134 cycles, Provor fl oats through 64, and Solo fl oats through 87. The longer life span of Apex fl oats is attributable to a dozen very long-lived Japanese fl oatsdrifting at shallow depths. Adjusting for these anomalies, the average Apex fl oat life span is then 120 cycles. Based on fl oat op-erations at the Japan Agency for Marine-Earth Science and Technology, an Argo-standard fl oat should last through more than 82 cycles on average. The average life span of Apex fl oats is more than 99 cycles, and Metocean-Provor fl oats last through50 cycles. Some fl oat failures have already been addressed, and as a result, a current Apex fl oat is expected to continue its operation at least through the 116th cycle, and a current Metocean-Provor fl oat is expected to operate through 54 cycles. The anticipated longer Apex life span is attributable to the completion of major mechanical repairs.

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Biogeochemical Observations from Profi ling Floats - The Oxygen Success Story and More to Come

Arne KörtzingerIFM-GEOMAR, Leibniz-Institute for Marine Sciences Kiel, Duesternbrooker Weg 20, D-24105 Kiel, Germany


Modern oceanography has to provide answers on how global change will impact on the physical and chemical environ-ment of the ocean and how this might cascade through marine ecosystems and potentially feed back into the climate system. This exciting and daunting task that major scientifi c programmes such as CLIVAR, SOLAS, and IMBER have adopted, requires innovative observational approaches that have to be used in a comprehensive and highly coordinated fashion. Special emphasis lies on the surface ocean, i.e the upper 100 m of the water column, where our long-term autonomous observational capabilities are still most severely limited. The ARGO profi ling fl oat observatory is a major success story in observational oceanography that marine biogeochemists have always been envious of. Due to the lack of suitable chemical and biological sensors they so far largely missed this great opportunity. However, new sensor and miniaturized instruments are being developed and major technological breakthroughs have been made or are to be expected soon. The recent advent of a new optode-based oceanographic oxygen sensor is such a quantum leap which allows precise and long-term stable measurements from profi ling fl oats. Examples will be shown from the Labrador Sea, the tropical Atlantic Ocean as well as the Weddell Sea which illustrate the high quality and scientifi c potential of such measurements. Furthermore, the profi ling fl oat technology provides observational capabilities that extend beyond Argo-style mission and include bi-directionality, recovery options and “virtual mooring” applications etc. Plans and ideas in this context will be shared.See also Posters by Gilbert and Riser

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Coupled air-sea interactions in the tropical Indian Ocean environment

Raghavan Krishnan, K. V. Ramesh, B.K.Samala, G. Meyers, J.M.Slingo and M.J. FennessyClimate and Global Modelling Division, Indian Institute of Tropical Meteorology, Dr. Homi Bhabha Road, NCL Post. Pashan, Pune x

411008, [email protected]

PosterSubsurface temperature measurements from Argo fl oats and XBT observations in the tropical Indian Ocean; satellite ob-servations of sea surface height anomalies from TOPEX / POSEIDON and JASON; scatterometer winds from QuikSCAT and other atmospheric data products are analyzed in order to understand interactions between the monsoon circulation and the tropical Indian Ocean on the intra-seasonal time-scale. The fi ndings reveal that ocean-atmosphere coupling is dominant on intra-seasonal time-scales. The ocean heat content and subsurface temperature anomalies in the equato-rial Indian Ocean clearly bring out the role of monsoonal wind forcing on the intra-seasonal variations of the thermocline depth. Further, it is seen that the anomalies of ocean heat content infl uence the atmospheric winds and convection pat-terns on the intra-seasonal time-scale.

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Northeastern Atlantic Current Systems Revisited

Matthias Lankhorst and Uwe SendLeibniz-Institut fuer Meereswissenschaften (IFM-GEOMAR), Duesternbrooker Weg 20, 24105 Kiel, Germany

Scripps Institution of Oceanography, La Jolla, CA, [email protected]

PosterData from Argo fl oat profi les is used to estimate means and intraannual variability of the transports of currents in the northeastern Atlantic. These currents - downstream parts of the North Atlantic Current (NAC) system - are the Irminger, North Atlantic Drift, and Azores Currents, all of which are believed to be important for the European climate system.

Time series of transports are deduced from long-distance geostrophic estimates between clusters of fl oats and across a virtual “CTD section” made of fl oat profi les available near a given line. Estimates of absolute transports are derived using satellite altimetry.

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The Global Observed Ocean Products of the French Mercator project

Gilles Larnicol, Stéphanie Guinehut, Marie-Helene Rio, Yannice Faugere, Gael NicolasCLS, 8-10 Rue Hermes, 31525 Ramonville, France

[email protected]

PosterIn the frame of the French Operational Oceanography Mercator project, satellite and in-situ measurements representing the two major complementary key components of the Global Ocean Observing System (GOOS) are combined in order to provide global observed ocean products at high temporal and spatial resolution. Two kinds of products are generated that both allow to monitor the ocean variability and to validate the MERCATOR Mercator simulations.

First, accurate but sparse in-situ T/S profi les data are merged with high resolution altimeter and SST data in order to reconstruct global instantaneous thermohaline fi elds from the surface down to 1500 m depth. The merging approach uses fi rst, a multiple linear regression method to derive synthetic T and S profi les from the satellite measurements. These synthetic profi les are then combined with the in-situ T and S profi les using an optimal interpolation method that takes into account analyzed error on the different observations. Twelve years (1993-2004) of 3-D thermohaline fi elds have been produced with this method and have been fi rst validated and compared with independent in-situ data sets in order to provide an estimation of the performances of the system over the whole ocean. Moreover, the impact of the different observing systems (Argo, SST) has been analysed. The quality of the estimated fi elds additionally allows us to study the interannual variability of the global ocean heat content as well as of the global mean sea level.Second, global instantaneous surface currents are derived from a combination of altimeter geostrophic currents, Ek-man currents derived from wind-fi elds and in-situ surface currents derived from drifting buoys. First, a two-parameter model, U= beiÉxÉ—, is used to compute the wind-driven circulation (Ekman component). b and Éx are estimated with a least square minimization method using drifting buoys and wind stress fi elds Then, the geostrophic component of the circulation is obtained by combining altimeter currents with the drifting buoys through a multivariate optimal interpolation method. Finally, the Ekman and geostrophic components are added to produce global surface currents products. Five years (1999-2004) of global 1/3° daily surface currents have been produced using QuickSCAT winds, altimeter data (Jason/ENVISAT), and drifting buoys coming from the AOML center. Impact of Ekman component, Mean Dynamic To-pography (MDT), and drifting buoys are successively analysed.Finally, the Global Observed Ocean Products (3D-thermohaline and surface currents fi elds) have been used as refer-enced fi elds for validation studies. Indeed, the comparison between MERCATOR simulations with these observed fi elds allows us to characterise the differences between observed products and simulations and to quantify the information provided by the model and its dynamic.

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GODAE and Argo

P.Y. Le Traon and the International GODAE Steering TeamIFREMER, Brest, France

Oral Friday 0820 [email protected]

The Global Ocean Data Assimilation Experiment (GODAE) is conducting its main demonstration and consolidation phase from 2003 to 2007. Operational and research institutions from Europe, Australia, Japan and the United States are per-forming global ocean data assimilation and ocean forecast in order to provide regular and comprehensive descriptions of ocean fi elds such as temperature, salinity and currents at high temporal and spatial resolution. GODAE provides an integrated description of the ocean that combines remote sensing data, in-situ data and models through data assimila-tion. One of the objectives of GODAE is to maximize the benefi ts from the data (in particular altimetry and Argo). A central issue is to effectively merge Argo data with remote sensing data for the description of the global ocean at high space and time resolution needed for most of the GODAE applications. A review of GODAE achievements and progress will be given. We will then focus the presentation on the use of Argo data by GODAE centers and the contribution of Argo data to GODAE and its applications. Important issues for the future of GODAE and Argo and for preparing the transition to operational systems will be fi nally given.

**********Decadal changes of Pacifi c salinity

Li Ren and Steve RiserBox 357940, School of Oceanography, University of Washington, Seattle, WA,98195, USA

[email protected]

The comparison between ARGO fl oat data (2003-2005) and WOCE data (1985-1994) in Pacifi c Ocean revealed a large scale freshening in both the North and South Pacifi c Oceans on potential densities between 25.5 and 26.6. The signal was a maximum at the northeast and southeast portions of the two ocean basins and became weaker following the sub-tropical gyre path. Estimation of the geostrophic velocity fi eld from the fl oats showed that water in this density range is renewed on a time scale of about 10 years. In the N. Pacifi c, the western sub-polar gyre showed increasing salinity, and the geostrophic velocity estimated from the fl oats suggested that water in western subpolar gyre near potential density of 26.6 is renewed rapidly, within 2-3 years, while in the eastern subarctic N. Pacifi c the renewal time is closer to 10 years. In the South Pacifi c, a large scale freshening of the Antarctic Intermediate Water was observed on potential density 27.1. The large scale freshening on these isopycnals in both the North and South Pacifi c suggest E-P changes at higher lati-tudes in the Pacifi c Ocean.

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Observed characteristics at the eastern edge of the warm pool in the western Pacifi c Ocean

C. Maes1, K. Ando, T. Delcroix, W. S. Kessler, M. J. McPhaden, and D. Roemmich1IRD/LEGOS Centre IRD, BP A5, 98848 Noumea New-Caledonia

[email protected] 1020 Saturday

The western Pacifi c warm pool is of fundamental importance to interannual variations associated with El Niño and the Southern Oscillation (ENSO), the strongest year-to-year climate variation on the planet. The warm pool encompasses the highest mean sea surface temperatures (SSTs) in the world ocean, intense atmospheric deep convection and heavy rainfall, and the formation of thick salt-stratifi ed barrier layers that help to sustain the high SSTs. In order to evaluate the importance of salinity variations in such dynamical relationships, three different sources of sea surface salinity (SSS) observation are jointly analyzed along with the SST, surface zonal current, rainfall and surface zonal wind. The features of the upper ocean layers are derived from the vertical profi les provided by Argo fl oats. At the surface, a salinity front of the order of 0.4 over 1-2° in longitude and a barrier layer of O(20m) thickness are persistent features during the period 2002-2004. This result contrasts with that based on historical data analyses which indicate an average SSS gradient of 0.4 over 10-15° in longitude. The analysis also reveals a tighter empirical relationship than previously observed between the eastern edge of the warm pool, high SSTs, the presence of barrier layers, and the fetch of westerly wind bursts. Our results suggest that the eastern edge of the warm pool is a critical in controlling ocean-atmosphere interactions in the western Pacifi c and highlight the importance of the upper ocean salinity in climate variability.

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Assimilating temperature and salinity profi le data together with altimeter sea surface height data in a high resolution ocean model.

Matt Martin, Adrian HinesMet Offi ce, FitzRoy Road, Exeter, EX1 3PB, UK

matthew.martin@metoffi ce.gov.ukPoster

In order to accurately forecast the state of the ocean at the mesoscale, data is required to initialise the ocean forecast model. In situ profi le data, such as those from Argo, are of insuffi cient horizontal resolution to properly initialise features such as mesoscale eddies but do provide very useful information about the larger scale ocean state. Altimeter sea sur-face height (SSH) data are available at very high along-track resolution and are accurate enough to be assimilated into ocean models. These surface measurements contain information about mesoscale features that usually extend into the deep ocean. However, methods such as the Cooper and Haines scheme which are used to infer subsurface properties from the surface altimeter data rely on the water mass properties of the background model fi eld being correct. A careful approach for combining the information from both in situ and satellite measurements is therefore required when assimi-lating the data.An identical twin framework has been set up using a 1/9 resolution confi guration of FOAM for the North Atlantic to test various aspects of the way in which the altimeter and Argo data are assimilated in the system. This framework is useful as it is possible to test the convergence of variables not normally observed. It also enables various aspects of the scheme to be tested in isolation by artifi cially adding errors into the system. It is however an easier test of the system than in the real world because the model and data are consistent with each other, as are the different data types (SSH, temperature and salinity). Results from this system and their likely impact on the operational assimilation scheme are discussed.

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A proposed Argo Data application and modeling system aimed to climate and marine risk management along Western South America

Rodney Martínez GüinglaCentro Internacional para la Investigación del Fenómeno El Niño, P.O Box Escobedo y 9 de Octubre 1204, Guayaquil - Ecuador

[email protected]

Considering the increasing lack of coherence between the Central Equatorial Pacifi c and NIÑO 1+2 SST fi elds, the gaps on the understanding of the South Eastern Pacifi c circulation and the existent observational, institutional and hu-man capabilities in Western South America countries: Venezuela, Colombia, Ecuador, Peru, Bolivia and Chile. and the Argo data currently available along the Eastern Pacifi c and the Caribbean, a regional end to end system is proposed to get SST and salinity data from Argo network to be analyzed, and used as initial conditions in existent ROM´s models in the region, forecast SST fi elds at monthly or seasonal scale and further process them to force mesoscale operational models in mentioned countries to adjust and improve rainfall forecast. These forecasts are processed within geographic information system which contains land use information and other specifi c parameters depending of the ending user requirements to generate climate risk scenarios for all the countries of Western South America. The framework to de-velop this regional integral system is the currently existent Seasonal forecast group of experts in Western South America coordinated by CIIFEN. The proposed scheme includes, Institutional coordination between National Meteorological and Oceanographic Institutions, to build a regional data base and foster the full implementation of regional ocean models available in the region in order to ensure an operational Argo data fl ux from the sensors to regional models and the further rainfall forecast in each country from the region. The fi nal forecast product will be entered in a GIS to produce monthly and seasonal climate risk scenarios to be disseminated to multiple audiences since decision makers to general public.

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On the relationship between the Antarctic Intermediate Circulation and the Argo coverage in the Southwestern Atlantic

Mauricio M. Mata1, Edmo Campos2, Vagner S. Duarte1

1 Dept. of Physics (Physical Oceanography), Federal University of Rio Grande, Rio Grande (RS), BRAZIL2 Dept. of Physical Oceanography, University of São Paulo, São Paulo (SP), BRAZIL2 Dept. of Physical Oceanography, University of São Paulo, São Paulo (SP), BRAZIL2

[email protected]

A void in the Argo coverage in the western end of the South Atlantic gyre has been often observed by the community. The formation of that void is a serious problem in the Argo main concept of semi-stationary synoptic oceanographic stations in that part of the ocean. In that region, the Argo fl oats essentially follow the westward path of the Antarctic Intermediate cir-culation along both sides of the Vitoria-Trindade Ridge, where mean current velocities as high as 15 cm/s are observed. Here, we investigate the fl ow characteristics in that area using a combination of the Argo fl oats data and the outputs of the POP Global ocean model. Most of the ARGO fl oat data come from instruments recently deployed along the VT Ridge by a joint project between Brazilian and US institutions, which also marked the onset of the Brazilian participation in the Argo Programme. Those fl oats were released along the VT Ridge and further east, to both fi ll the gap and to investigate possible mechanisms involved in the void formation. The 3-D velocity fi elds from the outputs of the POP model bring up two important factors. The fi rst suggests that the zero velocity crossing along the vertical profi les take place around 750m and 1500m in south of the VT ridge, with signifi cant zonal velocities being observed around 1000m. The second factor suggests that the barotropic component of the zonal velocities becomes quite important to the north of the VT ridge, which imposes and general westward fl ow throughout the water column.

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Using profi ling fl oats to estimate the upper layer heat budget during POMME

H. Mercier1, C. Grit1, V. Thierry1 , G. Caniaux2

1Laboratoire de Physique des Océans, CNRS, Ifremer, UBO2Centre National de Recherches Météorologiques

[email protected]

The POMME experiment was carried out in a region of the northeast Atlantic (38°N - 45°N, 13°W - 23°W) from September 2000 to October 2001. It aimed at studying the role of mesoscale eddies in the formation and subduction of northeast At-lantic mode water. In the framework of this experiment, 14 temperature profi ling fl oats were deployed. The fl oats were set up to drift at 400 m and to carry out a temperature profi le from 2000 m to the ocean surface every ten days. Knowledge of air-sea fl uxes being crucial for understanding subduction processes, accurate high resolution air-sea heat fl uxes were derived by the Centre National de Recherches Météorologiques (CNRM) from a combination of satellite products, in situ data and outputs of atmospheric models. This work is based on the profi ling fl oat data and the CNRM heat fl uxes. The upper ocean heat balance is derived by combining the change in heat content along the fl oat trajectories, which combines the time rate of change and the horizontal advection of heat, the vertical heat advection and the net air-sea heat fl ux contribution. We show that the upper ocean heat balance for POMME can be closed to better than 10 W m-2. The vertical velocity, that is needed to estimate the vertical heat advection, is estimated from the heat conservation equation in which the diffusion is neglected. At 400 m, we estimate -1.2 10-6 m s-1 for the mean vertical velocity, which indicates subduction and is remarkably close to the -1.0 10-6 m s-1 mean Ekman vertical velocity estimated from wind products.

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Sea surface salinity from a simplifi ed ocean mixed layer model using global altimeter data

Sylvain Michel, Bertrand Chaparron, Jean Tournadre and Nicolas ReulIFREMER, Technopole Brest-Iroise, 29280 Plouzané, France


A vertically integrated 2D model of the ocean mixed layer is used to estimate the anomalies of Sea Surface Salinity (SSS) caused by atmospheric heat fl uxes, evaporation-precipitation budget, wind friction and geostrophic circulation. The input parameters are the Sea Surface Temperature and air/sea fl uxes derived from ECMWF meteorological model and the geostrophic currents from SSALTO-DUACS altimetry analysis. The model is fi rst tested with a high-frequency climatologi-cal forcing dataset, in terms of variability and space distribution of SSS response. It is shown that variations in wind-in-duced transport is the fi rst cause of salinity variability, but fresh water fl ux and geostrophic transport can dominate locally. Then the analysis is performed over several recent years, using an optimal combination of space-borne observations and model outputs. The results are validated using in situ measurements from buoy arrays in the tropical Pacifi c (TAO) and Atlantic (PIRATA), then using gridded fi elds from Argo drifters over the North-Atlantic (Coriolis analysis). Finally, the interest of this method and its real-time application is examined in view of the future SMOS and Aquarius satellites, which will both be dedicated to SSS retrieval.

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Observational error and a measure of central tendency of the Argo profi le

Shinya Minato, Shigeki HosodaIORGC/JAMSTEC, 2-15, Natshushima-cho, Yokosuka, Kanagawa, 237-0061, Japan

[email protected]

As short term (several hours) fl uctuation of P-T or P-S profi le is not small compared with other seasonal or long term dynamic changes, one should be careful when he uses profi le data with observational error (noise). We have analyzed short term fl uctu-ation of the (P,T,S) profi le as internal inertia-gravity wave using ship-board CTD (Mirai, 2005) in the mid-depth of the equatorialPacifi c. Whether it can be applied to daily Argo profi les obtained in successive emergency ascent period (several days), far apart from the CTD point (date and location) will be discussed.

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The deep circulation in the Norwegian Sea from subsurface fl oats

Kjell Arne Mork, Henrik SøilandInstitute of Marine Research, Nordnesgaten 50, P.O. 1870 Nordnes, N-5817 Bergen, Norway


The deep circulation in the two basins of the Norwegian Sea, the Norwegian and the Lofoten Basin, has for the fi rst time been measured over several years with the use of subsurface fl oats, i.e. Argo fl oats. Institute of Marine Research has in total deployed nine Argo fl oats that are drifting at 1500 m depth. The fi rst three fl oats were deployed in year 2002 while the six others were deployed in 2003. The trajectories of the fl oats show a cyclonic circulation at 1500 m depth in both two basins with largest speed in the Lofoten Basin. The currents are strongest at the rims of the two basins where its speed is about 10 cm/s in the Lofoten Basin and about 5 cm/s in the Norwegian Basin. The fl oats show that the circulation is highly topographic steered and in many areas opposite directed compared to the surface fl ow. Even relatively small topographic features at 3000 m depth infl uence the circulation at 1500 m depth. The seasonal changes in the drift of the fl oats and its relation to the wind forcing have been investigated and the results will be presented.

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Forcing mechanisms for SAMW formation : role of eddies vs Ekman transport.

J.B. Sallee, R. Morrow, K. Speer, and N. WiendersCentre de Topographie des Océans et de l’Hydrosphère, LEGOS - UMR5566, 18, av. Edouard Belin,

31401 TOULOUSE Cedex 9, [email protected]

PosterThe surface layer heat budget in the region of SAMW formation in the southeast Indian Ocean is addressed using a com-bination of satellite and in-situ hydrological data including Argo fl oats. We fi nd that air-sea fl uxes dominate the seasonal variations in heat content, and the strong Ekman heat transport continually cools the region, with a maximum cooling in winter. On the large-scale, these two forcing terms are suffi cient to close the heat budget.Argo fl oat data shows that SAMW gets progressively cooler, fresher and denser along the circumpolar path. However, the heat budget calculation does not explain why the mixed layers become so deep after Kerguelen Plateau. The Argo fl oat profi les show strong interleaving between the two waters, from the surface down to the mode and intermediate wa-ter mass densities. The eddy heat diffusion term also changes sign around Kerguelen, with eddies upstream tending to warm the Subantarctic Zone (SAZ) by diffusing heat from the Agulhas Return Current, whereas around and downstream of Kerguelen, the eddies tend to cool the SAZ, by transferring cool water from the south. We suggest that the strong turbulent mixing in this region reduces the subsurface stratifi cation and preconditions the fl ow so that deep winter mixed layers can form downstream.

**********The mixed layer variations in the North Pacifi c as detected by the Argo fl oats

Yuko Ohno, Naoto Iwasaka, Eitaro Oka, and Fumiaki KobashiTokyo University of Marine Science and Technology, Etchujima 2-1-6, Koto-ku, Tokyo 135-8533, JAPAN

[email protected]

The Argo data have become available to the mixed layer (ML) studies, which have mostly depended on the data ob-served by ships in limited areas for short periods or based on climatological data. In this study, we investigate the feature of ML variation in detail especially in the period from December to May when ML changes largely.Characteristics of distribution of the ML in the North Pacifi c revealed here are as follows: the deep mixed layer depths (MLD) are concentrated in the northwestern region of the subtropical gyre in winter. Comparing the distribution of MLDs measured by the Argo fl oats to those based on the WOA01 in March, for example, the MLD detected by the fl oats in north of the Kuroshio Extension (KE) are often shallower by up to 270m than the WOA01 but south of the KE the former are deeper by up to 330m. The short period-variations of MLD with large amplitude can be found. They occurred almost coincident with the period when the sea surface cooling is weakened, the pycnocline just below the ML is weakened, and the profi les of which ML is not observed clearly appear mostly. In an area north of 20N, the profi les of which ML is not observed clearly appear mostly from December through May. This tendency is evident especially in the subarctic region and northwestern region of subtropical gyre.

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Zonal Intermediate Currents in the Equatorial Atlantic Ocean

Michel Ollitrault1, Matthias Lankhorst2, David Fratantoni3, Philip Richardson3, and Walter Zenk2

1 IFREMER, Technopole Brest-Iroise, 29280 Plouzané, France2 IFM-GEOMAR, Germany 2 IFM-GEOMAR, Germany 2 3 WHOI, USA

[email protected]

Acoustic fl oat data collected near 800 m depth, are used to map zonal mean currents within the Antarctic Intermediate Water (AAIW) tongue in the equatorial Atlantic. Alternating zonal jets of 2º latitudinal width are revealed between 6º S and 6º N. Displacements from profi ling fl oats drifting near 1000 m depth, also reveal similar zonal jets at the base of the AAIW layer. The strongest jets (15 cm s-1 peak) are found at 4ºS, 2ºS, 0º, 2ºN and 4ºN. They are coherent longitudinally over order of 3000 km and, poleward of 1ºS and 1ºN, generally coherent vertically between 800m and 1000m. Large seasonal fl uctuations exist at both levels.

**********Estimating the time-averaged circulation of the North Atlantic Ocean

Steven Jayne1, Breck Owens1, Bruce Cornuelle2

1Woods Hole Oceanographic Institution, Woods Hole, MA2Scripps Institution of Oceanography, La Jolla, CA


We begin with a variety of data sources: the time-average sea surface from satellite altimetry, the geoid from the Gravity Recovery and Climate Experiment (GRACE) mission, the historical temperature and salinity climatology, and the surface and deep ocean velocities from fl oats and drifters. We combine these observations through constrained optimal interpola-tion. Our goal is to combine data from the developing Global Ocean Observing System (GOOS)—satellite altimeters, the GRACE mission, surface drifters, and the Argo array of profi ling fl oats, to derive data-only estimates of the ocean circula-tion. The purpose of these products is to provide an independent synthesis of the data for the evaluation of numerical models and model-based ocean state estimations, as well as to utilize them for scientifi c exploration of the circulation.We discuss the ocean circulation derived from the temporal-averaged sea surface height, which is referenced to the recently released geoid (University of Texas – GGM02C) from the GRACE mission. The creation of a precise, indepen-dent geoid allows for the calculation of the reference gravitational potential undulation surface, which is associated with the resting-ocean surface height. This reference height is then removed from the temporal averaged sea surface height, leaving the dynamic ocean topography. This has previously been impracticable due to large uncertainties in previous estimates of the Earth’s geoid.Error estimates are made to assess the accuracy of the estimated dynamic ocean topography. The deep ocean pressure fi eld is also estimated by adding the calculated dynamic ocean topography to the dynamic height from hydrography to include the velocity component due to vertical shear. The derived circulation is compared to independent observations of the circulation from sea surface drifters and subsurface fl oats.Finding broad consistency between the different data types, we combine the data using inverse methods to estimate the velocity and the pressure fi elds for the North Atlantic Ocean. The various data sources have different information content, so their combination provides a better estimate than that from each alone. Furthermore, the combination of these data show where there are inconsistencies or errors in the different observations. We expand the traditional objective map-ping technique to account for the Equator. In the future, this methodology should allow the near real-time mapping of the ocean circulation through the use of Argo fl oats, surface drifters and the satellite altimeters.

**********Seasonal and Interannual Variability in the Sub-polar North Atlantic as measured by profi ling fl oats, 1997 to the present

Xingwen Li1, Breck Owens1, Kara Lavender2

1 Woods Hole Oceanographic Institution, Woods Hole, MA2 Sea Education Association, Woods Hole, MA

PosterUsing profi ling fl oat data collected as part of the WOCE ACCE and Argo fl oat programs heat and salt content for the upper 1000 m, dynamic height and potential vorticity estimates have been objectively mapped for the sub-polar North Atlantic from 1997 to the present. Time series of areal-averages over sub-regions, such as the western Labrador and Irminger Seas, have also been computed. The dynamic height fi elds have been combined with the mean reference level velocity mapped from fl oat displacements to give three dimensional velocity estimates.Due to the increase in data coverage, signatures of the mean boundary currents are much more clearly defi ned in the time-mean heat and salt content maps than those from climatology. Along the western boundary, downstream changes in temperature are consistent with surface heat loss estimates while salinity changes suggest that there is also a signifi -cant exchange with the interior of the Labrador Sea. Combining these maps with the three-dimensional velocity maps, estimates of the heat and salt advection by the major currents of the sub-polar gyre are estimated.The time series of heat and salt content in the Irminger and Labrador Seas demonstrate that there was a signifi cant in-crease in the depth of convective overturning in the late 1990’s for both of these deep convection sites. As Straneo (2005) found for the Labrador Sea, comparisons between these time series for other parts of the sub-polar gyre and adjusted NCEP (Moore and Renfrew, 2002) show that while the infl uence of the surface heat fl ux is mostly limited to the upper 200 m, there are deep changes in heat that are associated with signifi cant horizontal advection.While correlations between the altimetric measurements of sea-surface height anomaly and surface to 1000 m steric height anomaly are signifi cant, there are also high correlations between the 0-1000 m heat and salt content anomalies for all sub-regions of the sub-polar gyre, except the Labrador Sea. That is, the anomalies tend to be warm/salty or cold/fresh but also have displacements of density surfaces that produce the observed changes in the steric height anomalies.

**********31but also have displacements of density surfaces that produce the observed changes in the steric height anomalies.31

but also have displacements of density surfaces that produce the observed changes in the steric height anomalies.

HadGOA - Hadley Centre global subsurface ocean analysis of temperature and salinity

Matt Palmer, Tara Ansell and Simon Tett.Met Offi ce Hadley Centre for Climate Prediction and Research, FitzRoy Road Exeter EX1 3PB UK

matthew.palmer@metoffi ce.gov.ukPoster

HadGOA is a project to develop an ocean subsurface analysis and climatology product designed for model validation and evaluation of historical ocean variability. The project is currently in the preliminary stages, so our focus has been on the scientifi c strategy and clarifying user requirements. The product is based on quality-controlled observational data from ENACT (Enhanced Ocean Data Assimilation and Climate Prediction) and is planned to incorporate near real-time updates by its completion. The HadGOA analyses will be made freely available for use by the climate research com-munity.One of the driving forces behind this project is the communityxs need for an alternative to the NODC (National Oceano-graphic Data Center, USA) analyses. Some of the key advantages of our analyses will be: (i) averaging of properties on isotherms and/or isopycnals; (ii) a rigorous quality control procedure; and (iii) error estimates of derived quantities. The gridding and interpolation algorithms used by HadGOA will be clear and open-source. This will enable observation-model comparisons to be performed in the most meaningful way.The fi rst stage of the project will concentrate on evaluation of the historical ocean heat content. Isotherms will be used as the vertical coordinate in order to utilise all the available temperature data. This approach has the advantage over a more traditional z-level analysis of removing some of the infl uence of changes in ocean dynamics on variations in heat content.

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Validation of Argo Salinity Data from the Global Ocean with Special Reference to the Indian Ocean

Pankajakshan Thadathil, P. M. Muraleedharan, S. Prasannakumar, ,C. Revichanran*, V.V.Gopalakrishna , S. Gourish, V.S.N Murthy, G.V. Reddy, Yong-Hoon Youn and Homan Lee

National Institute of Oceanography, Dona Paula, Goa-403 004* Regional Centre, [email protected]

PosterArgo salinity data from the global ocean are validated using salinity from fl oat-to-fl oat match-ups. For the Indian Ocean, in addition to the fl oat-to-fl oat match-ups, the validation also incorporates collocated CTD data from ship observations. A time difference of less than 5 days and space difference less than 20 km have been considered for locating the col-located fl oat-to-fl oat match-ups. For validation in the Indian Ocean, involving fl oat-to-CTD data from ship observations, the time and space criteria are 10 days and 100 km, respectively. The evaluation in both the cases is done on theta (potential temperature) surfaces from deeper observations (mostly on theta of 2 or 3°C for fl oat-to-fl oat match-ups). The global ocean validation results show that except for a few match-ups from the Indian Ocean, the fl oat-to-fl oat match-ups are consistent in observing salinity data within 0.01 PSU. In the Indian Ocean, validation using fl oat-to-ship observation match-ups also show that fl oat salinity data and salinity data from ship observations are comparable within 0.01 PSU, the desired accuracy for Argo salinity.

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Seasonal and Inter-annual Variability of Barrier Layer in the Bay of Bengal: An Argo Perspective

Pankajakshan Thadathil, P. M. Muraleedharan, V.V.Gopalakrishna, C. Revichanran*, and G.V. ReddyNational Institute of Oceanography, Dona Paula, Goa-403 004

* Regional Centre, [email protected]

PosterSeasonal and inter-annual variability of barrier layer (difference between isothermal layer and mixed layer) in the Bay of Bengal has been studied using Argo data from the Bay of Bengal for the period 2002-2005. The observed seasonal variability of barrier layer thickness (BLT) has a semi-annual cycle. BLT attains its maximum thickness of 60-70 m in the northern bay during January-February. Minimum BLT of <10m is observed during April-May. A secondary maxima (25-40 m) is observed during August-September followed by a secondary minimum of 10-20 m during October – November. Shoaling of MLD due to fresh water induced buoyancy and thick isothermal layer contribute towards the observed maxi-ma of 60-70 m BLT during January-February. The inter-annual variability of BLT is found to be of the order of 10-20 m.

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32

Meridional Mass Transport across 38-40°N in the East/Japan Sea

Young-Gyu Park , Kyung-Hee Oh , and Moon-Sik SukKorea Ocean Research and Development Institute, Ansan P.O. Box 29, Seoul 425-744, Korea

Poster Poster Poster [email protected] geostrophic calculations with a quasi-zonal CTD section obtained between 38-40°N in summer 1999, and velocity estimates at 700 m level from autonomous profi ling fl oats (Argo fl oats), we investigate the structure of meridional mass and heat transports in the East/Japan Sea. In the horizontal, due to eddies and the meandering of the polar front, the fl ow changes its direction almost at every 100 km or so. In the vertical, although the fl ow becomes weaker with depth the direction of the fl ow does not change suggesting the importance of the bottom topography even at the surface. The total volume transport though the CTD section is 1.6 Sv., which is signifi cantly less than the volume transport through the Korea Strait, which is around 2.5 Sv., because the CTD section does not cover the strong and narrow current along the Japanese coast (the Near shore Branch). Water colder than 10°C is due to it own thermoha-line circulation of about 0.9 Sv. The meridional mass transport due to the surface wind stress across the CTD section is less than 10% of that due to the geostrophic fl ow.

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Global distribution of inertial energy and inertial energy fl ux

Jong Jin Park , Kuh KimSchool of Earth and Environmental Sciences, Seoul National University, Seoul, Korea

[email protected]

Statistics of inertial currents in the North Pacifi c, North Atlantic, and Southern Ocean are derived for the period 1997–2005 from surface trajectories of Argo profi ling fl oats by employing a method developed recently by Park et al. [2004]. The distri-bution of inertial amplitudes is non-Gaussian in the range 0~80 cm/sec with an average value of 13.7 cm/sec. The inertial amplitude in the mid-latitude (30°N~45°N) band exceeds those in both the low (15°N~30°N) and high (45°N~60°N) latitude bands. In three basins, the amplitude in summer is greater than that in winter by 15%~25%. The inertial energy in the mixed layer reaches approximately 1100 J/m2~1165 J/m2 globally. The spatiotemporal patterns of inertial amplitudes in the North At-lantic mostly depend on the MLD, which exhibits strong meridional gradients. However, the small meridional gradient of the MLD in the North Pacifi c does not contribute signifi cantly to the spatial distribution of inertial amplitudes [Park et al., 2005].Further, the wind stress from QuikSCAT and the inertial motion from Argo fl oats and surface drifters provide the global inertial energy fl ux from the atmosphere to the ocean. The energy fl ux into the ocean is more dominant than that out of the ocean. The averaged inertial energy fl ux in the world ocean, except for the low latitude band (20°S~20°N) and the high latitude band (higher than 60°N and 60°S), reaches 0.68 TW, which has similar order to the tidal dissipation (0.7 TW reported by Egbert and Ray, 2002). Therefore, the inertial energy could contribute signifi cantly to sustaining the meridional overturning circulation in terms of the model results reported by Munk and Wunsch (1998).

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Synergy between ocean observations and numerical simulations : CLIPPER heritage and DRAKKAR perspectives

Thierry Penduff1, Dr. Bernard Barnier1 , Dr. Anne-Marie Treguier1, and Dr. Pierre-Yves Le Traon2

1CNRS, BP53, 38041 Grenoble, France2 IFREMER, BP70, 29280 PLOUZANE, France

Oral Wednesday 0840 [email protected] on oceanic circulation, variability and underlying processes has been stimulated since the WOCE years by combined exami-nations of observations and model simulations. This synergy is achieved in data assimilation studies, but also whenever observations are used with unconstrained, high-resolution, multiyear simulations forced by atmospheric reanalyses. Between 1995 and 2003, the French CLIPPER project has developed and run Atlantic models based on the OPA8 code at 1°, 1/3° and 1/6° resolution to study vari-ous aspects of the ocean dynamics over the period 1980-2000+. Its successor DRAKKAR is a community modelling program that partly aims at improving model-observation synergies, in an extended context: European collaboration (France, Germany, Russia, Finland), wider domain (Atlantic-Nordic Seas to global), increased resolution (1/4° to 1/12°, with local grid refi nement capabilities), longer period (1950-present), richer and improved physics (OPA9+LIM sea-ice, parameterizations).The evaluation of numerical solutions against available observations is an example of model-data synergy. CLIPPER solutions were evaluated by several authors who extracted model counterparts of real data colocated in space (and possibly time) and treated both datasets identically. For example, lagrangian time/space eddy scales (Lumkin et al, 2002), deep subtropical zonal fl ows (Treguier et al, 2003a), Agulhas rings properties (Treguier et al, 2003b), interannual variations of water mass characteristics (CLIPPER Group, 2001) and of basin-scale eddy distribution (Penduff et al, 2004) were validated and studied by building and comparing colocated datasets (drifters, ADCP, BRAVO timeseries, and altimeter fi elds, respectively). More quantitative validation studies may involve model-data correlations as done by Illig et al (2004) for tropical sea level anomalies, or require the development of synthetic misfi t (or model skill) estimates, as proposed by Penduff et al (2005) for current meter data. Within the OST/ST framework, the DRAKKAR group wishes to improve validation methods and make them more quantitative, by generating synthetic datasets colocated with various observations (e.g. Argo, T/P, Jason, etc) and defi ning appropriate skill estimates.High-resolution satellite products should help improve the forcing of ocean models, in combination with atmospheric reanalyses. The CLIPPER group made use of satellite SSTs (Reynolds and Smith, 1994) for air-sea fl ux corrections, and observed that scatterometer winds may substantially improve the simulations at low latitudes. Reanalysed atmospheric variables are being used through bulk for-mulae to force the global and regional DRAKKAR models. The merging of recent satellite datasets (e.g. winds, radiative fl uxes) with reanalyses is currently investigated, and their impact on oceanic simulations will be evaluated.In turn, realistic simulations provide a dynamical context to interpret observations or design observing systems. Among other examples, CLIPPER-derived synthetic datasets proved useful for estimating the representativeness of hydrographic transects (Treguier et al, 2005), diagnosing the spatial and temporal scales of surface salinity for remote sensing applications (Molines et al, 2001), evaluate the design of the Argo array (Guinehut et al, 2002) or its combination with satellite data for temperature analyses (Guinehut et al, 2004). One of DRAKKAR objectives is to pursue such collaborative investigations in order to characterize the representativeness of (possibly combined and/or future) observation systems, the observability of small-scale processes or climat indexes. To reach this goal, different kinds of synthetic datasets (satellite, in-situ, up to kilometric resolutions) will be designed, generated, distributed and analysed in col-laboration with the OST/ST and observationalist communities.

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Interpreting low frequency sea level signals over the last decade

Rui Ponte1, Sergey Vinogradov1 , Carl Wunsch2

1 Atmospheric and Environmental Research, Inc., 131 Hartwell Avenue, Lexington, MA 02421-3126, United States2 Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, United States


Sea level variability on time scales from months to years can be associated with a variety of processes, from warming of the water column due to changes in surface heat fl ux to changes in the surface circulation driven by variable wind stress. Correctly interpreting the observed sea level signals can thus reveal important clues about the nature of ocean and climate variability. Here an attempt is made to unravel the processes behind sea level signals observed over the period 1992-2004, from the seasonal cycle to long term trends. The basic tool is the estimation procedure used by the ECCO-GODAE consortium that constrains an ocean general circulation model in a least-squares sense. Altimetric data, both time-dependent, and time-mean are a large part of the 410 million data constraints used, which also include CTDs, XBTs, Argo fl oat profi les, and meteorological variables. The constrained solution produces a good fi t of the altimeter vari-ability and compares well with a tide gauge dataset not used in the optimization. Variability in sea level is decomposed into bottom pressure, halosteric, and thermosteric terms, and each respective contribution is analyzed as a function of time scale and location. Both regional and global mean sea level signals are treated in terms of their relation to surface forcing, relevant dynamic and thermodynamic processes, along with discussion of shortcomings in model formulation and overall uncertainties in the constrained solution.

***********Assessment of the MEDARGO Profi ling Float Program in the Mediterranean

Pierre-Marie PoulainIstituto Nazionale di Oceanografi a e di Geofi sica Sperimentale (OGS), Trieste, Italy

[email protected] PosterIn the framework of the EU-sponsored MFS project, MEDARGO profi ling fl oats have been deployed throughout the Mediterranean starting in summer 2004 to provide temperature and salinity data in near-real time to forecasting models of the Mediterranean. All fl oats were programmed with a neutral parking depth of 350 db and a maximum profi ling depth of 700 db, with a cycling period of 5 days. Every ten cycles, the fl oats were programmed to profi le as deep as 2000 db. The vertical sampling intervals are 5 m (above 100 m), 10 m (between 100 and 700 m) and 50 m (below 700 m). The fl oat data were processed and archived at the CORIOLIS Data Center (Brest, France) and were distributed on the GTS. As of the end of September 2005, 21 MEDARGO fl oats have been deployed and have provided more than 1100 profi les in most basins of the Mediterranean Sea.The effectiveness of the MEDARGO program is assessed, mostly in terms of the adequacy of the cycle characteristics chosen for the fl oats and in terms of the deployment sites selected. When collocated (in space and time) the MEDARGO data are compared to the temperatures obtained from the VOS XBT program. The MEDARGO data are used to describe the spatio-temporal variability of the water mass properties in the Mediterranean. They are also compared to the tempera-ture and salinity data of the MEDAR MEDATLAS II climatology.

**********Mediterranean temperature and salinity variability as derived from MEDARGO data

Riccardo Barbanti and Pierre-Marie PoulainIstituto Nazionale di Oceanografi a e di Geofi sica Sperimentale (OGS), Trieste, Italy

[email protected] PosterThe data provided by the MEDARGO profi ling fl oats in the Mediterranean between July 2004 and December 2005 (more than 1300 CTD profi les) are analyzed to study the variability of the temperature and salinity in the major basins of the Mediterranean Sea. Comparing these temperature and salinity data to the MEDAR MEDATLAS II climatology, the ME-DARGO project has revealed that the Western Mediterranean in the mid-2000xs is signifi cantly warmer and more saline than the climatology based on data mostly collected in the last century.

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Observations of the Mode Water Formation and Evolution from the Kuroshio Extension System Study (KESS) Float Program

Bo Qiu, Peter Hacker, Shuiming Chen, Kathleen A. Donohue, D. Randolph Watts, Humio Mitsudera, Nelson Hogg, Steven JayneDepartment of Oceanography, University of Hawaii at Manoa, 1000 Pope Road, Honolulu, HI 96822, USA


Properties and seasonal evolution of North Pacifi c Subtropical Mode Water (STMW) within and south of the Kuroshio Extension recirculation gyre are analyzed from profi ling fl oat data and additional hydrographic and ship-board ADCP measurements taken during 2004. The presence of an enhanced recirculation gyre and relatively low mesoscale eddy variability rendered this year favorable for the formation of STMW.

Within the recirculation gyre, STMW formed from late winter convectionwhich reached depths greater than 450 m near the center of the gyre. The lower boundary of STMW, corresponding to sigma_theta 25.5, was set by the maximum depth of the late winter mixed layer. Properties within the deep portions of the STMW layer remained largely unchanged as the season progressed. In contrast, the upper boundary of the STMW layer eroded steadily as the seasonal thermocline deepened from late April to August. Vertical eddy diffusivity responsible for this erosion was estimated from a budget analysis of potential vorticity to be in the range of 2 ~ 5 x 10 cm2sec -1

********** 34

Water mass transformation in the Nordic Seas

Detlef Quadfasel and Katrin LatariusInstitut für Meereskunde, Centre for Marine and Atmospheric Sciences Hamburg

[email protected]

Atlantic Water enters the Nordic Seas mainly across the eastern part of the Greenland-Scotland Ridge. Cooling, dilution with freshwater and input of salt brines during ice formation transform this water into a light, fresh component and into dense overfl ow water that feeds the lower branch of the Meridional Overturning Circulation of the North Atlantic. Since 2001 a number of ARGO profi ling fl oats have been deployed in the different deep basins of the Nordic Seas, allowing to quantify the water mass formation and modifi cation on the seasonal time scale.In the eastern basins winter time cooling created mixed layers up to 600 m depth, but the development was hampered by lateral input of freshwater from the coastal current. Here the heat loss occurring during winter is mainly replenished by the advection of warm water in the Norwegian Atlantic Current. In the Greenland Sea the mixed layer reached up to 1200 m depth. The large cyclonic gyre prevents direct advection and here the winter time heat loss is mainly replenished by lateral eddy fl uxes. The actual mixing depths are strongly related to the horizontal freshwater fl ux from the East Green-land Current. Most of the newly formed water is also exported to the boundary via eddies. The fl oats in the Icelandic Sea were deployed only during autumn 2005, but fi rst results on winter time overturning should be available by the time of the meeting.

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Role of sub-surface ocean variability for recent extreme weather events Over south Asia during 2005: Insights from Argo

K.V. RameshOcean and Climate Modelling,, CSIR Centre for Mathematical Modelling and Computer Simulation, NAL Belur Campus,

Bangalore-37, [email protected]

PosterIndian Ocean plays an important role in regional and global climate variability. The year 2005, Indian sub-continent ex-perienced lot of extreme weather events ( Heavy rainfall events and number of cyclones). In this study we examine the role of oceans in affecting the regional weather patterns. Here we analysed the network of Argo fl oats from Indian Ocean The preliminary results shows the high frequencey variability of ocean sub-surface temperature is playing a crucial role in initiating or sustaining these events. The results will be presented in detail.

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Controlling the large-scale ocean circulation using a multivariate 3D-Var approach: the complementary role of altimetry and in situ measurements

Elisabeth Remy1, Anthony Weaver2 , and Nicolas Daget2

1 MERCATOR OCEAN, Parc Technologique du canal, 31520 Ramonville, France2 CERFACS, 31 avenue Gustave Coriolis, 31000 Toulouse, France2 CERFACS, 31 avenue Gustave Coriolis, 31000 Toulouse, France2

[email protected]

The Mercator-Ocean operational systems routinely assimilate in situ and altimetry measurements using an optimal inter-polation scheme to estimate initial conditions for two-week ocean state predictions. More advanced assimilation methods are under development in collaboration with external research groups: one of them is the variational approach. In this presentation we explore the ability of a 3D-Var version of OPAVAR, developed at CERFACS, to constrain the global large-scale ocean circulation by assimilating in situ and remote-sensing observations. The experimental design is based on the framework defi ned in the European ENACT project. Reanalysis experiments for the period 1993-2001 will be described. The experiments are performed with a 2-degree global ocean model, the ORCA2 confi guration of OPA. The fi rst one assimilates only in situ temperature and salinity data from the ENACT quality-controlled data-set; the second experiment assimilates only sea-level anomalies from the CLS data-base; and the third experiment assimilates both data-sets. Those simulations are analysed and compared with a free-model run. The relative impact of the different types of observations to constrain the model dynamics and water masses will be investigated. Particular attention will be paid to the large-scale surface and subsurface circulation, its mean and variability on seasonal-to-interannual time-scales. The problem of the MSSH will also be addressed.

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Complementarities between ship-of-opportunity in situ surface salinity data and the Argo data

Gilles ReverdinLODYC, Univ. Paris VI, boite 100, 4, place Jussieu, 75252 Paris Cx 05, France

[email protected] Oral Saturday 1130Surface data have been collected by ships-of-opportunity across large swaths of the Atlantic Ocean on regular basis since the mid 1970s, either from water samples collected mostly from buckets or data from thermosalinographs (TSG). These data are used to produce maps of surface salinity, which have two main drawbacks. First, the coverage is highly inhomogeneous; second, the data present often biases which are very diffi cult to assess. The Argo data sampling of the upper ocean presents since the late 1990s an attractive alternative. We will present fi rst the intercomparison of the two types of data, and illustrate how these can be used to identify biases in the ships-of-opportunity TSG data. We’ll also compare the performances of mapping of the TSG data versus the Argo data.

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Labrador Sea convection and circulation of low-salinity waters tracked by Seagliders, Argo and Altimetry

Hjalmar Hatun, Charlie Eriksen, and Peter RhinesUniversity of Washington, Seattle, Washington, 98195 USA


We have observed with Seagliders, Argo fl oats and altimetry, the eddy-rich separation of the west Green-land boundary current in the Labrador Sea. This current provides buoyancy, at both deep and shallow levels, to mediate deep wintertime convection, and hence to mediate the creation of Labrador Sea Water. The inward advection of a buoyant, low-salinity surface layer also exerts strong control over the geographical distribu-tion of late-winter mixed layer depth. The internal structure of intense, predominantly anticyclonic eddies em-bedded in the circulation, is probed at high resolution. Argo fl oats provide essential hydrographic fi elds ‘sur-rounding’ these intense events. A related issue, the 1990s decline of the altimetrically-observed subpolar gyre circulation and associated change in the Atlantic Water infl ow from Atlantic to Nordic Seas will be touched upon.Argo fl oats, Seagliders and satellite altimetery are strongly complementary in their sampling ability; we will discuss ways in which gliders can provide essential observations of ocean climate change.

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An Ocean Data Analysis from in-situ remote-sensing data for the Australian Region

Ken Ridgway, Jeff Dunn, Madeline Cahill, David Griffi nCSIRO Marine & Atmospheric Research, GPO Box 1538, Hobart, Tasmania 7001, Australia


We describe an empirical system for generating 3-D fi elds of temperature and Salinity for the waters around Australia us-ing both Argoprofi les and surface altimetry and SST fi elds (SynTS). Historical oceanic profi les are used as a training set to derive vertical relationships between surface properties, which are observed by satellite sensors (sea level anomaly, temperature) and subsurface T and S. Two methods are used which depend heavily on CSIRO Atlas of Regional Seas (CARS), an accurate, high resolution T and S climatology. North of ~ 50°S a set of multiple linear regression relations are obtained between the surface and the temperature at each depth level. A loess fi lter is used to generate smooth 2-D fi elds of regression coeffi cients at each level from the non-uniform spatial distribution of ocean casts. The relationships are derived as anomalies with respect to the CARS mean. South of ~50°S, we apply a variant of the Gravest Empirical Mode (GEM) method. We exploit the tight relationship between subsurface T and S and the surface steric height. The empirical system is applied to a region enclosing 90°-180°E; 60°S – 10°N. The fi nal product merges Argo profi les with the synthetic fi elds at each depth using optimal interpolation. The system has been run in hindcast mode for the period 1993-2004 using delayed mode gridded altimetry fi elds and composite satellite SST and is also operated in a near real-time mode. A range of results are presented including comparisons with Argo, XBT & CTD sections, and with OFAM, an eddy-resolving, data-assimilating ocean model.

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Year-long measurements of rain and windspeed from Argo fl oats

Stephen C. RiserSchool of Oceanography, University of Washington, Seattle, WA 98195 USA

[email protected] Oral Saturday 1710Measurements of rainfall and wind speed have been collected from Argo fl oats deployed in the Bay of Bengal and the eastern equatorial Pacifi c. In the Bay of Bengal case, where the measurements lasted for well over one year, the data show a seasonal monsoon cycle consistent with both climatology and data from moored weather buoys and coastal me-teolological stations. The measurements are collected using an Acoustic Rain Gauge, an addition to profi ling fl oats that listens for characteristic acoustic signatures of wind and rainfall while drifting at depth between profi les. In the cases re-ported here, data were collected and processed at approximatly 3-hour intervals along the fl oat drift path. It is suggested that this relatively low-cost addition to profi ling fl oats could in the future provide useful climate data for improving surface fl ux estimates in remote parts of the world where few data presently exist.

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Long-term measurements of dissolved oxygen from Argo fl oats

Stephen C. RiserSchool of Oceanography, University of Washington, Seattle, WA 98195 USA

[email protected]

We assess the performance of dissolved oxygen sensors on over 20 profi ling fl oats deployed in Argo. Some of these sen-sors performed well for nearly 3 years, showing only small values of sensor drift over this time. Several sensors showed only weak drift over times in excess of one year, although there were calibration offsets in the data that appeared imme-diately after deployment. In other cases, sensors failed within a few profi les of deployment. We have deployed several fl oats with SeaBird and Aanderaa/Optode sensors mounted side-by-side for comparison; in these cases there are some systematic differences between the measurements but in general the two sensors agree remarkably well. In general it has been sound that, making dissolved oxygen measurements from profi ling fl oats is very promising, although more work is required on sensor integration and development before these techniques can be routinely used in Argo.

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Understanding of the East (Japan) Sea Circulation by using Altimeter, Argo and SST

Young Jae Ro, Eung Kim, and Yong Hoon YounDept. of Oceanography,, Chungnam National University, Taejon, Korea

[email protected]

The East (Japan) Sea has been drawing keen attentions to its surface circulation feature as well as to vertical ventila-tion processes. Since mid 90’s, the East Sea was recognized as ‘Miniature Ocean’ suitable for studying global warming problems in relatively smaller time and space scales compared to open ocean water.In this study, various datasets such as satellite altimeter and AVHRR image data (SSH and SST) at the sea surface and Argo Float Profi les (AFP) in the subsurface layer are utilized in understanding the circulation patterns and other dynamic processes such as meso-scale warm eddy generation and subpolar frontal meanders.

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JASON and Argo reveal a decadal spin-up of the South Pacifi c gyre

Dean Roemmich, John Gilson, Russ Davis, Phil Sutton, Susan Wijffels, Steve RiserScripps Institution of Oceanography, University of California San Diego, La Jolla CA 92093-0230 USA


The combination of satellite altimetry with the now-global Argo fl oat array enables unprecedented observations of sea-sonal-to-decadal variability in the global ocean circulation. The combined measurements describe the evolution in sea surface height (SSH) together with the subsurface temperature, salinity and velocity variability that are responsible for large-scale SSH changes. In the present work, Argo profi le and trajectory data, along with altimetric height and WOCE/CLIVAR hydrography, reveal a decadal spin-up of the South Pacifi c gyre.The increase in circulation of the deep subtropical gyre is observed over 12 years. The signal in SSH is a 12 cm increase between 1993 and 2003, centered at 40°S, 170°W and on large spatial scale. The subsurface datasets show that this sig-nal is predominantly due to density variations in the water column, extending to depths of at least 1800 m. The increases in SSH and dynamic height are co-located with the deep center of the subtropical gyre, representing an increase in the counter-clockwise geostrophic circulation of the gyre by ~ 25% at 1000 m. At the sea surface, the corresponding decadal increase in SST is 0.4° C. A comparison of WOCE and Argo fl oat trajectory data at 1000 m provides agreement with the gyre spin-up during the 1990xs as seen in SSH and dynamic height. Similarly, all of the datasets indicate that the spin-up signal peaked and began to reverse around 2003. The 1990sx increase in wind-driven circulation resulted from decadal intensifi cation of wind-stress curl east of New Zealand, variability associated with an increase in the southern hemisphere annual mode (SAM). It is suggested (based on SSH) that mid-latitude gyres in all of the oceans have been affected by variability in the atmospheric annular modes on decadal timescales. A major advance from the altimeters and the Argo array could be the global description of this climate variability signal.

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Recovery of North-East Atlantic temperature fi elds from profi ling fl oats: determination of the optimal fl oat number from sampling and instrumental error analysis

Simón Ruiz1,, Damià Gomis1 , and Jordi Font21 IMEDEA (CSIC-UIB), c/ Miquel Marqués, 21, 07190 Esporles, Spain

2 ICM (CMIMA-CSIC), P. Maritim de la Barceloneta, 37-49, 08003 Barcelona, Spain2 ICM (CMIMA-CSIC), P. Maritim de la Barceloneta, 37-49, 08003 Barcelona, Spain2

[email protected]

Argo is an international project that is deploying an array of temperature and salinity profi ling fl oats over the global ocean. Here we use the error formulation derived from Optimal Statistical Interpolation to estimate statistical errors associated with the recovery of the temperature fi eld in the North-East Atlantic ocean. Results indicate that with the present distribu-tion of fl oats (119 in the considered domain), scales of wavelength larger than 500 km can be recovered with a relative uncertainty (rms error relative to the standard deviation of the fi eld) of about 7% at 50 m, 8% at 200 m and 10% at 1000 m. This corresponds to mean absolute errors of 0.111ºC at 50 m, 0.104º C at 200 m and 0.073ºC at 1000 m.The splitting of total errors into instrumental and sampling contributions reveals that, in the present scenario, errors are more due to the small number of fl oats than to instrumental errors, especially at upper levels. For scales larger than 500 km this will hold true until 200-250 fl oats are deployed (less than 200 for deep levels). In such a simulated scenario, the number of observations and the technology become approximately equally limiting factors for the accuracy of the tem-perature fi eld mapping, with total relative errors of less than 2% at upper levels and about 3% at 1000 m.

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Barrier layers in the subtropical gyres of the world’s oceans

Kanako Sato, Toshio Suga, and Kimio HanawaInstitute of Observational Research for Global Change, Japan Agency for Marine-Earth Science and Technology

2-15 Natsushima-cho Yokosuka, Japan [email protected]

PosterThe existence of the barrier layers (BLs) has been reported not only in the equatorial regions but also in the subtropical gyres of the world’s oceans. BLs in the subtropical gyres have been investigated to a lesser degree only based on the climatological data partly due to insuffi cient synoptic observational data. In the present study, BLs in the subtropical gyres of the world’s oceans are detected by analyzing all temperature and salinity profi les taken by Argo fl oats from January 2000 to June 2005. The thick BLs exceeding 40-m thickness appear in the subtropical gyres of the world’s oceans but confi ned mainly in the winter hemisphere. The thickness and frequency of appearance of the BLs in the subtropical gyres of the North Atlantic, South Pacifi c, and Indian Ocean show considerable seasonal dependencies in the similar manner to those in the North Pacifi c reported earlier by Sato et al. (2004; GRL) as the BLs are thicker and appear more frequently in the boreal winter than the other seasons. The fact that the BLs of the subtropical gyres in the winter hemisphere lie in the region of excess evaporation and near the intense salinity fronts suggests that the BLs of the subtropical gyres are formed by the same mechanism as those in the North Pacifi c, that is the subduction of high saline water at those sharp salinity fronts.

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Preliminary estimates of the time-variant heat budget in the Tropical Atlantic

Claudia Schmid, Gustavo Goni, and Rick LumpkinNOAA/AOML, 4301 Rickenbacker Causeway, Miami, FL 33149, USA

[email protected] PosterA better understanding of the mixed layer heat budget in the tropical Atlantic is important for climate research and predic-tion. Of particular interest are regions where the heat balance is not dominated by the surface heat fl uxes. Such regions include, for example, the equatorial cold tongue and the coastal upwelling regions off Africa. The approach is based on the analysis of a wide range of insitu and satellite observations covering the years 1997-2005. Hydrographic profi les are used to derive the a time series of the monthly heat storage rate. Where the temporal resolution is poor these observa-tions are augmented by sea surface temperatures and sea surface height anomalies from satellites. The oceanic heat transports are derived from drifter observations in conjunction with geostrophic velocities from altimetric fi elds and Ekman currents from scatterometer winds. Preliminary results from this analysis show that good estimates of the heat budget can be derived with this approach. For example, in the tropical South Atlantic (10-3S, 15-0W) the difference between the heat storage rate and the net surface heat fl ux is on the order of 40 W/m^2 in boreal summer, and the peak of the heat storage rate lags behind the peak of the surface fl ux by about a month. When taking the advection of heat into account the phase shift is gone in most years and the difference in the boreal summer peaks is reduced to less then 10 W/m^2 in most years.

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Energetics of the barrier layer in the tropical Indian Ocean using Argo profi les

Rashmi Sharma, Neeraj Agarwal, Anant Parekh and Abhijit SarkarOceanic Sciences Division, Meteorology and Oceanography Group, Space Applications Centre, Ahmedabad, India

PosterDifferent regions of the tropical Indian Ocean (TIO) are subjected to diverse atmospheric forcings and consequently their characteristics are also quite dissimilar. Both Arabian Sea and Bay of Bengal are forced by seasonally reversing monsoon winds, yet their water mass characteristics are quite different, the former losing fresh water due to excess evaporation whereas, the later receives excess fresh water due to surplus rain and river discharge. Previous studies using climatological data base have revealed that the thickness of the barrier layer (BL), which is the layer between the bases of the mixed layer and the isothermal layer in the eastern equatorial Indian Ocean region is 10-25 m. The strong stratifi cation due to the presence of BL leads to trapping of the kinetic energy in the mixed layer. It also reduces the inter-action between the mixed layer and the deeper isothermal layer. The difference in the depths of the surface isothermal layer and the isopycnal layer can be studied in terms of surface forced turbulent winds, fresh water fl ux and net heat fl ux. In some of the oceanic regions the formation of barrier layer could be due to the horizontal heat and salt transport. The long period availability of Argo fl oats offers a unique opportunity to study the distribution of BLs, its energetics and formation mechanism in the entire TIO.We have evaluated the barrier layers (BLs) from Argo profi ling fl oats deployed in the TIO from Jan. 2003 to Jun 2005. The Arabian Sea and Bay of Bengal show distinct water mass characteristics on the T-S diagram constructed using Argo temperature and salinity profi les. A clear separation of the two basins is evident on the density isolines on T-S diagram. The Bay of Bengal surface water temperature show a small range of temperature variation as contrast to Arabian Sea, which has a temperature range of 20ºC to 30ºC. The average distribution of BL depth in the TIO show large values in Bay of Bengal, eastern Indian Ocean and in the southeast Arabian Sea, where the average value is of the order of 30-40 m. Due to the strong stratifi cation the energy required for mixing (ERM) upper 50 m of the ocean is quite large in these regions. This has been calculated from the vertical density profi les. Interestingly, in these regions the turbulent energy available (computed from satellite derived ocean surface wind) for mixing is quite less. A detailed analysis of the energet-ics of the barrier layer will be presented in the workshop.

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JAMSTEC’s activity in Argo Program

Nobuyuki Shikama, T.Kobayashi, E.Oka, S.Minato, S.Hosoda, and H.UenoIORGC/JAMSTEC, 2-15, Natshushima-cho, Yokosuka, Kanagawa, 237-0061,Japan

[email protected]

JAMSTEC has been playing an important role to implement the international Argo Program.JAMSTEC has deployed about 400 Argo fl oats since 2000 in the North and South Pacifi c, the Indian, and the Southern Oceans and made a variety of research and development associated with Argo Program as follows;logistics problem to deploy fl oats, simulation of fl oat dispersion, analyses of malfuncion of fl oats, recovery of fl oats to ex-amine sensor drift, development and improvement of delayed-mode quality control procedure, launching device of fl oats, development of a new fl oat, capacity building for younger generation and Island Nations in the Pacifi c, et al. All these JAMSTEC’s activities are oulined in this presentation.

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Upper ocean response to the Madden-Julian Oscillation in the Indian and Western Pacifi c Oceans from Argo fl oats

Patama Singhruck, Karen Heywood and Adrian MatthewsSchool of Environmental Sciences, University of East Anglia, Norwich, Norfolk, NR4 7TJ, UK

[email protected]

The Madden-Julian Oscillation (MJO) is the dominant mode of intraseasonal variability in the tropical atmosphere. Changes in atmospheric forcing, i.e. surface wind stress, and surface energy and freshwater fl uxes can induce changes in the structure and dynamics of the upper ocean. The objective of this study is to examine how the upper ocean responds to the MJO using newly available observations. Temperature and salinity from Argo fl oats in the Indian and Western Pacifi c Oceans from 2003 to 2005 are mapped to a regular weekly-mean grid with one-degree horizontal and fi ve-me-ter vertical resolution by an objective interpolation method. The newly gridded dataset shows good agreement with the NOAA optimum interpolation sea surface temperature dataset and selected moored buoys from TAO/TRITON project. It also captures some salient features in this region such as a narrow band along the equator of semi-annual variability of the Indian Ocean Equatorial current system. Preliminary results from compositing temperature and salinity anomalies during MJO events show a coherent pattern of near surface changes in the two variables. However, subsurface changes are less coherent. Further analysis on subsurface variability and mixed layer depth dynamics will be presented in detail.

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Assimilation of Argo data into ECMWF models: operational impacts and diagnostics of ocean transports

Gregory C. Smith, .Keith Haines, Arthur Vidard, David Anderson, Magdalena Balmaseda, Chunlei Liu, Alberto TroccoliEnvironmental Systems Science Centre, University of Reading, 3 Earley Gate, Reading, RG6 6AL, UK


Argo data is now part of operational seasonal forecasting system 3 at ECMWF. The impact of improved coverage of ocean temperatures and the availability of coincident ocean salinity data are examined. In particular, the infl uence of sa-linity data is demonstrated through a new S(T) assimilation scheme. Assimilation diagnostics show that the ocean model forecasts of all quantities, including currents, have improved. The ocean model is then used to assess ocean transports and water mass variability. It is shown that salinity measurements have a big impact on these transport products, and it is argued that Argo data is an excellent tool for monitoring the impact and the role of the ocean in climate variability.

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Profi ling Float Observations in the Aegean Sea

S. Sofi anos1, A. Theocharis2 and V. Vervatis1

1University of Athens, Ocean Physics and Modelling Group2Hellenic Center for Marine Research, Institute of Oceanography

sofi [email protected]

Aiming at gaining a better understanding of the dynamics governing the circulation of the very complex environment of the Aegean Sea as well as the mixing and water mass formation processes in the region, profi ling fl oats are being de-ployed in various locations of the basin. The initial efforts demonstrate the capabilities of the new monitoring techniques and at the same time point out the need for specialized sampling strategies in the region. The profi ling fl oat data (with the accompanied CTD surveys) reveal and/or confi rm interesting features of the Aegean Sea dynamics. There is a re-markable difference of the temperature/salinity characteristics between the North and South Aegean sub-basins. At the surface layers the large differences can attributed to the presence of the Black Sea Water in the northern basin (infl owing from the Dardanelles strait with very low temperature and salinity), while in the Cretan Sea surface waters are infl uenced by the warmer and more saline waters of Levantine origin. The deep-water temperature and salinity differences are also important, indicating a possible decoupling of the two sub-basins. The Cretan Sea profi les reveal a relatively less saline intermediate layer centered at around 800m. Its origin is the deep-water masses of the eastern Mediterranean and is related to the regional abrupt climatic event of the early 90s known as Eastern Mediterranean Transient. Comparison with older observations indicates important mixing processes within and outside the Aegean and a possible evolution of the exchange between the Cretan Sea and the Levantine basin.

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Argo measurements near the sea-ice margin.

K. Speer, N. Wienders, C. ChienDepartment of Oceanography, Florida State University, Tallahassee, FL 32303, USA


Argo observations will be used to understand the mechanisms of seasonal changes in sea ice. In order to address these mechanisms, we estimate budgets in given regions to deduce which of the possible mechanisms of sea ice growth by local freezing, transport or melt is dominant. The procedure will be to estimate the tendencies of heat and freshwater/moisture content in the surface layer of the ocean (Argo data) and atmosphere (satellite and NCEP) and relate these to available air-sea fl ux and advection products.Heat and freshwater content along the path of the fl oat can be estimated directly from the ocean profi les of temperature and salinity. Using these budgets, we will investigate the dominant mechanisms responsible for sea ice edge expansion and melt during the seasonal cycle.

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Data Assimilation Experiment of Argo fl oats to Quasi-Operational Ocean Prediction System around Korean Waters

Moon-Sik Suk and D. Bala SubrahamanyamOcean Climate and Environment Research Division. Korea Ocean Research & Development Institute (KORDI)

Ansan P.O. Box 29, Seoul 425-600, Republic of Korea.Oral Saturday 0920 [email protected]

As part of Korean Ocean Prediction System (KOPS), we present some features of Korean waters through data assimila-tion experiments carried out on a three-dimensional circulation model commonly known as the Princeton Ocean Model. In this paper, special emphasis is paid towards the assimilation of observational temperature and salinity data obtained from drifting Argo fl oats and AVISO Sea Surface Heights (SSH) data. The data assimilation is carried out by nudging as used in an optimal interpolation based analysis. Observational data obtained from the free-drifting Argo profi ling fl oat includes profi les of temperature and salinity of the upper 700 m of the ocean, whereas residual sea surface heights from AVISO contain information on vertically integrated dynamic structure of a water column. Conceptually, Argo fl oats build on the existing upper-ocean thermal networks, extending their spatial and temporal coverage, depth range and accuracy, and enhancing them through addition of salinity and velocity measurements. Incorporation of observational datasets from Argo profi les and AVISO Altimetry in initial conditions of the model through assimilation drastically improves the quality of forecast. The goal of the study is on construction of one unifi ed ocean model for the entire Korean waters and building upon data assimilation scheme for the operational purpose.

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Interannual variability of the subpolar mode water in the North-Atlantic

Virginie Thierry, Herlé MercierLaboratoire de Physique des Océans - UMR 6523 CNRS/IFREMER/UBO, Ifremer, BP 70, 29280 Plouzané Cédex,

[email protected]

PosterMode waters are formed in winter through enhanced air-sea forcing. The variability of their properties integrates the history of winter air-sea interactions in the formation area and is thus of interest for climate change studies. We use the ARGO data set as well as historical data to investigate the North Atlantic subpolar mode water variability. South of Iceland for instance, the present day mode water is warmer and saltier compared to the 90’s. As those temperature and salinity anomalies are not compensated, the mode water is lighter. We show that this variability is tightly related to the NAO index. Using the ARGO data set to determine the formation area of the various type of subpolar mode water, we investigate in more details the origin of this variability.

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Interest of combining satellite altimeter data with temperature and salinity data on the new assimilation MERCATOR System

Benoît Tranchant1, Charles-Emmanuel Testut1, Nicolas Ferry1 , Pierre Brasseur2

1 MERCATOR, Mercator-océan, 8/10 rue Hermes, 31520 Ramonville-St-Agne, France2 LEGI, BP 53, 38041 Grenoble , France2 LEGI, BP 53, 38041 Grenoble , France2

[email protected]

The French MERCATOR project is developing several operational ocean forecasting systems to take part in the Global Ocean Data Assimilation Experiment (GODAE). Prototype systems are designed to simulate (1) the Atlantic and Mediter-ranean Sea (from 1/3° to 1/15°), and (2) the global ocean circulation (from 2° to 1/4°). A new generation of fully multivari-ate assimilation system referred to as SAM2v1 is being developed from the SEEK (Singular Evolutive Extended Kalman) algorithm (developed at LEGI, Grenoble). This scheme is a Reduced Order Kalman Filter using a 3D multivariate modal decomposition of the forecast error covariance as well as an adaptive scheme to specify parameters of the forecast er-ror. The use of the SEEK fi lter and its 3D modal representation for the error statistic is intended to overcome some of the limitations of the previous OI scheme in highly inhomogeneous, anisotropic, and nonseparable regions of the world ocean such as shallow areas, as well as in the surface layer. Unlike the original SEEK fi lter, the variant of SAM2 which is considered here doesn’t evolve the error statistics according to the model dynamics [Testut et al., 2003]. This would require prohibitive costs given the size of the operational systems. However, some form of evolutivity of the background error is taken into account by considering different error sub-spaces related to the analysis day. As the previous system, it allows to assimilate vertical profi les and SST in addition to altimetry (JASON, ERS-2 and GFO), but in larger quantity at a lower cost. To minimise the computational requirements, the analysis kernel in SAM2 has been massively parallelized and integrated in a generic platform hosting the SAM1 and SAM2 kernel families [Tranchant et al., 2005]. This platform is driven by the PALM software [Lagarde et al., 2001; Piacentini et al., 2003] which makes the coupling between the model codes and the assimilation schemes more effective. Several Observing System Experiments have been performed with SAM2 for various prototypes (North Atlantic to Global confi gurations) and results will be presented and discussed.

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Seasonal temperature and salinity distribution in the Upper South West Atlantic derived from Argo and historical hydro-graphic data

Ariel Hernán TroisiCentro Argentino de Datos Oceanográfi cos, Servicio de Hidrografía Naval, Av. Montes de Oca 2124,

C1270ABV Buenos Aires, [email protected]

PosterSeasonal temperature and salinity fi elds in the Upper South West Atlantic derived from Argo fl oats data are compared against distributions derived from historical hydrographic databases. The selected area between 30ºS and 38ºS is a highly variable and energetic region infl uenced by the Brazil/Malvinas Confl uence. The results are expected to give indi-cations on the spatial and temporal resolution according to data density providing an evaluation tool for the use of Argo data in areas of sparse sampling.

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Seasonal and interannual variability of temperature inversions in the subarctic North Pacifi c

Hiromichi Ueno, Eitarou Oka, Toshio Suga and Hiroji OnishiArgo Group, Institute of Observational Research for Global Change,

JAMSTEC, 2-15 Natsushima-cho, Yokosuka, Kanagawa, 237-0061, [email protected]

Oral Friday 1710Hydrographic data from profi ling fl oats obtained during 2000-2004 were analyzed to study seasonal and interannualvari-ability of temperature inversions (T-invs) in the subarctic North Pacifi c (SNP). In the western SNP and Bering Sea, the temperature minimum at the top of T-invs outcropped and was renewed every winter, causing a seasonal cycle in the magnitude of T-invs, with the maximum at the end of winter. In the Gulf of Alaska in the eastern SNP, the temperature minimum outcropped in winters 2002 and 2004, but scarcely outcropped in winter 2003. Consequently, the magnitude of the T-invs showed remarkable interannual variation; its monotonic decrease through winter 2003 overwhelmed the seasonal cycle. The year-to-year variation of the magnitude of the T-invs in each region of the SNP was consistent with and thereby attributable to that of the winter sea surface temperature anomaly there.

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Eddies and winter mixed layer depth in the Rockall Trough observed by fl oats

Jenny Ullgren, Martin White, Christian MohnDepartment of Earth and Ocean Sciences, National University of Ireland, Galway.

[email protected]

The Rockall Trough, west of Ireland, is an important pathway by which warm, saline water masses enter the Nordic Seas, as part of the ocean climate system. Several water masses converge and mix in this region, and the area is known for its deep winter convection. Argo fl oat T/S data were used in conjunction with other in situ and remotely sensed data to study the winter mixing and the water mass structure and circulation in the southern Rockall Trough in 2003-2004. Two Argo fl oats deployed in October 2003, set to drift at 1000dB pressure level, demonstrated signifi cant mesoscale eddy activity at the southern entrance to the Trough, and an East-West orientated dominant fl ow pattern. One of the fl oats circulated anticyclonically around a high dynamic height feature that was often present in the altimetry, the location of its centre moving mainly in east-west direction. Float data were also used to calculate the winter mixed layer depths and the infl u-ence of different water masses along the fl oat track. It is hoped that this study will shed light on how the winter mixing and large scale oceanic forcing infl uences the circulation and water mass mixing in the southern Rockall Trough.

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A statistical description of the eddy fi eld in the subtropical North Atlantic using combined Argo and CTD data.

Manuel Vargas-Yáñez, Pedro Vélez-Belchi, Gregorio Parrilla, Alicia Lavín.Instituto Español de Oceanografía. C.O. Málaga. Puerto Pesquero de Fuengirola, s/n. 29640 Fuengirola, Málaga, Spain

[email protected]

The mesoscale fi eld in the ocean is superimposed to other time and length scales, not being easy to differentiate. A more exact description of it, is important in different studies. It should be considered for quantifying its impact on the data sets synopticity. Even Argo data sets are frequently made of not simultaneous profi les. The length scales and the variance associated to these structures have to be taken into account in the optimal interpolation of oceanographic data. Analysis of long time and spatial scale structures need the knowledge of these properties in order to asses im-portant statistics such as the integral time or spatial length scales. Modelling would profi t from the knowledge of these statistical properties for the parameterisation of sub-grid scale phenomena, such as eddy diffusion, viscosity, etc.Satellite data can provide a description of the eddy-fi eld at the sea surface, but some of these properties can be depth de-pendent. The combined use of Argo data and transatlantic hydrographic surveys in the subtropical North Atlantic, allow us to distinguish the time variability associated to the mesoscale fi eld from that associated to seasonal cycles or the profi lers drift. Objective analysis over different areas and surveys can help to defi ne the corresponding length scales. The ratio between both of them can provide a fi rst guess of the velocity of displacement of these structures. Argo and CTD profi les allow us to study the depth dependence of these variables.

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Spreading pattern of the Mediterranean outfl ow in the Iberian Basin estimated from Argo data

Pedro Velez-BelchiInstituto Español de Oceanografi a, Centro Oceanografi co de Canarias, Crta San Andres,45, E-38180 Sant Cruz de Tenerife, Spain

[email protected]

In the Iberian basin, the intermediate water masses that occupy the layer between 700 dbar and 1200 dbar, with potential density ranging between 27.3-27.7 kg m-3, are composed of Mediterranean Outfl ow waters (MOW) and Antarctic Inter-mediate Waters (AAIW); both water masses are clearly distinguished by the saltiness of the MOW. The mean location and spreading pattern of the Mediterranean Water outfl ow (MOW) is studied using ARGO data available since 2001. The main features of the MOW distribution are similar to those described in previous studies carried out with historical hydro-graphic data, with the maximum salinity values found northward the Strait of Gibraltar and the 36.0 isohaline extending westward to 16ºW. Some particular features of the distribution have strong differences when compared with other authors since the Argo data show a more meandering structure with its axis towards the northwest. The salty MOW tongue has higher variability than previously presumed. Given one of the strongest Argo characteristics, the temporal resolution, the interannual variability of the MOW tongue is also analyzed.

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Latitudinal variations in mixed layer depth and water mass properties around the Crozet Plateau from Argo profi le data

H Venables and R.T. PollardNational Oceanography Centre, Empress Dock, Southampton SO14 3ZH, UK

[email protected]

Satellite ocean colour images show that the regular phytoplankton bloom that occurs north of the Crozet Plateau (52°E, 46°S, Southern Ocean) starts away from the plateau and spreads south towards it. This indicates that the bloom is ini-tially controlled by the onset of stratifi cation (removal of light limitation) and that there are suffi cient nutrients in the bloom area at the end of winter. The mixed layer depth was found in each of the profi les in the area (40-60°E, 40-50°S) and the effects of day of year removed using a sinusoidal fi t. The residual mixed layer depths show a shallowing of the mixed layer to the north of 4.4±0.8 m/degree. The density difference between the mixed layer and 200m also increases to the north, indicating less temporal variability in the mixed layer depth. Consistent with this, satellite images show a latitudinal gradient in SST despite profi le data showing a consistent temperature at 200m within the bloom area. The extra heat is either coming from the much warmer (but also saltier) subtropical waters across the fronts bounding the area to the north or from in situ heating. Argo profi les show an increase in both temperature and salinity north of the fronts at the surface and 200m but an increase only in surface temperature to the south. The lack of enhanced salinity proves that the effect is from in situ heating, despite the relatively small latitudinal scale of the area of the bloom (300km).

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Assimilation of altimeter data in the ECMWF ocean analysis system

Arthur Vidard, Magdalena A. Balmaseda, and David L. T. AndersonECMWF, Shinfi eld Park, RG2 9AX Reading, United Kingdom

[email protected]

The operational ocean analysis system at ECMWF has been recently upgraded; among other changes it includes the ability to assimilate both salinity data and sea level anomalies derived from altimeter in addition to temperature.The altimeter data is used to correct temperature and salinity using the Cooper and Haines (1996) scheme. As part of the process of developing the new system, several ways of merging this information with the assimilation of subsurface data were explored and their respective merits compared. Additionally, attempts were made to use grace derived mean seal levels to reconstruct the total mean sea level. Although not used in the ECMWF operational system where only anomalies are assimilated, the relevance of this approach is discussed.An ocean reanalysis was carried out from 1959 and has now reach real time. It assimilates subsurface data from 1959 and altimeter data from 1993. Results from this analysis are presented and compared with subsurface only assimilation runs.

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Argo fl oat observations and high resolution modeling of the Arabian Sea warm pool

P. N. Vinayachandran and J. KurienCentre for Atmospheric and Oceanic Sciences, Indian Institute of Science, Bangalore 560012, India


The sea surface temperature exceeds 30C over a large area in the eastern Arabian Sea during the pre-summer monsoon moths of February – May and this warm pool is believed to play an important role on the onset of southwest monsoon over the southern tip of India. Previous observations of the warm pool has been restricted to the western coast of India. Temperature and salinity profi les from Argo fl oats provide the annual evolution of the three-dimensional structure of the Arabian Sea warm pool. The warmest waters are oriented in southwest-northeast direction (with one end touching the Indian coast) and is associated with high sea level anomalies and deeper thermocline. Previous studies have suggested that the intrusion of low salinity water from the Bay of Bengal in the southeastern Arabian Sea lead to the formation of a mini warm pool in that region by barrier layer formation. The Argo fl oat profi les suggest that the low salinity water from the Bay of Bengal that entering the Arabian Sea takes two paths: one part continues westward and and the other part fl ows northward along the Indian coast. A high resolution (25kmX25km, 40 vertical levels) ocean general circulation model has been used to simulate the Arabian Sea warm pool as well as to investigate its thermodynamics. Results of process ex-periments designed to isolate the salinity effects suggest that the shape of the warm pool is not determined by the barrier layer but by the large scale monsoon winds.

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Changes in the large-scale mixed layer properties in the Southern Ocean based on recent hydrographic observations and a simple mixed-layer model.

F. Busdraghi 1,2, F. Vivier 1, D. Iudicone 2

1 Laboratoire d’OcÈanographie et du Climat: Experimentation et Approches NumÈriques (LOCEAN, formerly known as LODYC), UniversitÈ Pierre et Marie Curie, Paris, France.

2 Stazione Zoologica A. Dohrn, Naples, Italy.2 Stazione Zoologica A. Dohrn, Naples, Italy.2


In an effort to document and understand the variability of the upper Southern Ocean, we are engaged in map-ping thermodynamic variables of the upper ocean from a wide base of in-situ observations. We use all pub-lic high vertical resolution data available from 1940 to present: WOCE (Word Ocean Circulation Experiment) and WOD01 (World Ocean Database 2001) data, combined with the most recent Argo, Mirounga04 (Elephant seals), and GTSPP (Global Temperature-Salinity Profi le Program) databases. The last three drastically improve the spatial data coverage at high latitudes and provide information in several regions totally unsampled to date.

Particular efforts are spent in quality check and data mapping, to capture changes that have occured at large spatial scales. We examine the variability of mixed layer depth, temperature and, wherever possible, salinity. Causes of ob-served variations are investigated using a simple ocean mixed-layer model forced with reanalysed fl uxes from the Euro-pean Centre for Medium-Range Weather Forecasts.

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Recent Changes of Heat Content in the North Atlantic Ocean

Neil C Wells, V.O. Ivchenko and Dr D.L. AleynikNOC, Southampton, SO14 3ZH, U.K

[email protected] [email protected]

The evolution of temperature and salinity fi elds during the last six years of observations in the upper 2 km layer in the Northern Atlantic were analysed in this study. The optimal interpolation technique is based on Gandin (1964) and Breth-erton et.al. al. (1976). Temporal and spatial gaps in data coverage were fi lled by combination with a climatology. The climatologies used (WOCE Global Hydrographic monthly climatology Gouretski and Koltermann, 2004; and WOA-2001, Levitus, 2001) demonstrate substantial differences in T and S distribution. The local variations of T, S characteristics were strongly dependent on the interpolation schemes used: isopycnal in WOCE and isobaric in WOA. Especially large differ-ences take place near frontal zones. We used Argo profi les data for the last 6 years (1999-2004) to calculate anomaly of heat content (AHC). We found a statistically signifi cant link between variability of the heat content in the upper 2000 m of the North Atlantic and the North Atlantic Oscillation index (NAO). The correlation between AHC and NAO are r=0.52, r=0.65, r=0.49 and r=0.55 if the lag is 0,1,6 and 8 years, respectively (NAO leads). The small lag relates to the baro-tropic adjustment (propagation of the fast barotropic Rossby waves) or the quick response of the Ekman transport to the changes in the wind fi eld. The long time lag may be linked with the Kelvin waves propagation along the continental slope and shelf, and refl ection of the baroclinic Rossby waves from the eastern boundary of the North Atlantic.

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Anomaly of heat content in the Northern Atlantic in the past 6 years: Is the ocean warning or cooling?

Ivchenko V.O., N.C. Wells and D.L. AleynikNOC, European Way, Southampton, SO14 3ZH, UK [email protected] [email protected]

PosterWhether the North Atlantic Ocean is warming or cooling is an important question both in physical oceanography and climate change. Levitus et al. (Science, 2000) has shown a warming of the upper 300 m of the North Atlantic between 1975 by 1998.The ARGO buoys provide an accurate and stable instrument for determining the tendencies in heat content from the surface to 2000m from 1999 to the present. However there are both spatial and temporal gaps in this data set. For this reason we combine these observations with a climatology (Levitus(2001), Gouretski and Koltermann (2004)). By this method we can estimate the anomaly of heat content (AHC) in the North Atlantic and all of its smaller sub-domains for the period 1999-2005.The results of our calculations are stable: removing a part of the data does not substantially changed the AHC. The upper 1500-m layer of the North Atlantic shows persistent negative values during the whole 6.5 year period. Comparing the AHC for three layers: 100-500 m, 500-1000 m and 1000-1500 m we fi nd negative values in all layers. The strongest anomaly corresponds to the layer 500-1000 m. Analysis of the meridional averages for 10-degree strips between 10N and 70N show a negative values in the southern and central subdomains (SD) (10-50 N) and positive in the northern subdomains. In the northern SD (50-70 N) positive values and a positive trend in the AHC is evident.

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Application of a model-based mapping tool for Argo observations

Susan Wijffels, Peter Oke, Helen Phillips (University of Tasmania)CSIRO Marine and Atmospheric Research, Hobart, TAS 7001, Australia

[email protected]

We are developing a system for producing routine, near-real-time, global maps of potential temperature and salinity ob-servations from the Argo array. We contrast maps produced using traditional optimal interpolation to those produced us-ing model-based estimates for the covariances. The model-based covariances have the advantage that they represent, more realistically, the length-scales and anisotropy of the ocean circulation in different regions. One of the applications of this approach is intended for the quality control of salinity observations. To achieve this we will produce maps of salinity on potential temperature surfaces. This may allow us to identify fl oats that exhibit erroneous drift in salinity.

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Mid-depth Circulation of the World’s Oceans: A First Look at the Argo Array

Josh Willis and Lee-Lueng FuJet Propulsion Laboratory, M/S 300-323, Pasadena, CA 91109, United States


Satellite-based measurements of sea-surface height provide data that is highly complimentary to a wide variety of in situ data sets. One of the most robust such data sets is the Argo array of profi ling fl oats. As of September, 2005, the Argo array has reached almost two-thirds of its target density and consists of more than 1900 fl oats, which now provide near-global coverage. In addition to producing a wealth of temperature and salinity profi les, Argo fl oats provide estimates of the mid-depth ocean circulation by drifting at a depth of 1000m over a period of 10 days. With roughly 3500 fl oat-years of data now available, a preliminary estimate of the mid-depth circulation can now be produced for most of the oceans using Argo data. Estimates of the velocity fi eld and dynamic height at 1000m depth will be presented. Altimeter-based estimates of sea-surface height anomaly also contain information about the geostrophic velocity fi eld. In addition to the estimates of mid-depth circulation, the relationship between anomalous geostrophic velocity at the surface and 1000m fl oat displacements was explored. Over much of the ocean, the altimeter data was found to be complimentary to the fl oat displacement data and a technique was developed for combining these two datasets to create improved estimates of the time-averaged velocity fi eld at 1000m. The altimeter data is fi rst used to estimate anomalous geostrophic velocity at depth, which is then used to correct individual fl oat displacements. Although improvements to individual fl oat trajectories are not always discernable, the correction signifi cantly reduces the variance of the displacement data and improves the signal to noise ratio by 50% in most regions, and more in regions of high eddy variability.

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Use of Argo data to detect and understand ocean climate change

Richard A. Wood, Sheila Stark, Michael Vellinga and Peili WuHadley Centre for Climate Prediction and Research, Met Offi ce, Exeter,UK

richard.wood@metoffi ce.gov.ukOral Friday 0840

The continuous timeseries of ocean temperature and salinity that Argo will provide are an essential tool if we are to understand the impact of climate change on the ocean. The full value of Argo for climate research will only be realised when multi-year or decadal timeseries are availiable; this presentation gives examples of the questions that Argocan help answer, which are inaccessible with currently available methods of observation. First, we use a climate model (HadCM3) to interpretinterpret recent observations of salinity changes in the South IndianOcean. Since only a few snapshots are available, it is not possible to quantify the interannual variability in these water masses. Interpretation of the observed changes, and using those changes to understand possible changes in the atmosphere’s hydrological cycle, will only be possible once the Argo timeseries has been in place for several years. A second example shows how Argo data may be used to supplement continuous observations of the Atlantic Meridional Ocverturning Circula-tion, in order to allow early detection of climate change signals. Sustaining the Argo timeseries for long enough to reap the full benefi ts for climate science is a challenging goal. By providing focused information on the specifi c scientifi c payoffs (and expected timescales) we clarify why it is so important to do this.

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ARGOS - 3 THE NEXT GENERATION

Bill Woodward, Christian Ortega - CLS; Philippe Gros - CLSARGOS Inc

[email protected]

The French-U.S. Argos system has been reliably satisfying the real-time data collection demands of the global oceano-graphic and meteorological communities for nearly three decades. By pacing the science and operational requirements of the ocean and meteorological community the satellite-based Argos data collection and location system enables fi xed weather stations and moored and drifting buoys and fl oats to continue to provide valuable research and operational data supporting the description, understanding and prediction needs of the coupled ocean-atmosphere system. There are presently nearly 2200 active fl oats in the international Argo program, with over half provided by the U.S. All of these instruments use the ARGOS Data Collection and Location System except for a few prototype fl oats equipped with Iridium or Orbcomm. In mid-2006 the third generation Argos system will become available. Scheduled for launch on the EUMET-SAT METOP 1 satellite in June this new generation of Argos will provide a number of signifi cantly improved features and capabilities to the community, including, among other things, an order of magnitude higher data rate and two-way com-munications. This presentation will outline these new capabilities, describe how they can be applied using the Argo fl oat program as a case study, present the launch schedule for satellites that will carry the new Argos 3 systems and provide some insight into what is being considered for the next generation of capabilities – Argos 4.

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Combining Altimetric and All Other Data with a General Circulation Model

Carl Wunsch and Patrick HeimbachMIT, Room 54-1524, Cambridge, USA


The TOPEX/POSEIDON mission was formulated in conjunction with the World Ocean Circulation Experiment (WOCE). Although altimetric data are by far the largest ocean data set that emerged from that experiment, it was recognized from the outset that the best estimate of the ocean circulation and its variability would be made by combining all the data with a good general circulation model. The US ECCO-GODAE consortium has now produced useful estimates of the three-dimensional time evolving ocean circulation at 1 degree lateral resolution, 23 layers in the vertical, over the time period 1992-2004. At the present time, the solution represents a least-squares misfi t to about 410million separate observational constraints. A huge variety of fi elds can be analyzed in the results, but the focus will be on the overturning circulation and its changes over this time period. The residual model/data misfi ts raise diffi cult questions about remaining errors in the altimetric/geoid fi elds.

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Estimating ocean middle-depth velocities from Argo fl oats: error estimation and application to Pacifi c

Jiping Xie1,2, JiangZhu1

1 Institute of Atmospheric Physics, Chinese Academy of Sciences2 Graduate School, Chinese Academy of Sciences2 Graduate School, Chinese Academy of Sciences2

[email protected]

We discuss three important issues concerning estimating mid-depth velocities from Argo fl oats. The fi rst is the quality control. It is found that a strict quality control in addition to operational QC procedures is necessary for the purpose of mid-depth current estimation. The second is the estimation of the fi rst and last points of a continuous surface trajectory in each diving-rising cycle of a fl oat. We proposed a stochastic, sequential estimation scheme that includes a deterministic forecast model to predict next surface position from two previous estimated surface points and a random part that represents the uncertainties in the forecast model. The deterministic model contains both non-rotational and inertial rotational movements. Determination of variances of the random part is also discussed. This estimation scheme can gives also estimation errors that are consistent with the statistics of forecast minus observation. The third issue is the error estimation of the mid-depth velocities. We consider both vertical sheer of velocity and the estimation errors of the fi rst and last points estimations.The above methods are applied to the Argo data in the tropical Pacifi c from 2001.11 to 2004.10. Mid-depth velocity estimations along with their estimation errors are obtained. The estimated mid-depth velocities are also compared with existing information of Pacifi c mid-depth velocities.

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Study on the circulation and water masses in the Northwest Pacifi c Ocean Using Argo profi ling fl oats

Xu Jianping 1,2 Liu Zenghong 1,2 Sun Chaohui 1,2 Zhu Bokang 1

1 Second Institute of Oceanography, State Oceanic Administration, Hangzhou 310021, China2 Key Lab. of Ocean Dynamic Processes and Satellite Oceanography, State Oceanic Administration. Hangzhou 310012, China

[email protected]

The main circulation and water masses in the area of northwest Pacifi c Ocean are studied using the drafting trajectory, temperature and salinity data obtained by Argo profi ling fl oats. Research shows that the main circulation in this area consists of the Subtropical Countercurrent (STCC), North Equatorial Current (NEC) /Equatorial Countercurrent (ECC), Kuroshio Current (KC), and the Mindanao Current (MC). It also indicates that SCC and NEC/ECC all have the character-istics of deep fl ow, for the evidence of them could be seen in the depth of 1500m. Near the offshore area east of Philip-pines, the fl ow fi eld the NEC presents a complex structure, of which may be related to the bifurcating of the current in this area. The T - S relation in this region indicates there exist 8 water masses: they are the North Pacifi c Tropical Surface Water (NPTSW), North Pacifi c Subsurface Water (NPSSW), North Pacifi c Subtropical Water (NPSTW), North Pacifi c In-termediate Water (NPIW), North Pacifi c Deep Water (NPDW) and Equatorial Surface Water (ESW), and the South Pacifi c Subsurface Water (SPSSW) and South Pacifi c Intermediate Water (SPIW). It is the growth and decline of those water masses, the atmospheric circulation, and the air-sea interaction, that result in peculiar weather/sea anomaly phenomena such as typhoon, warm pool, and EL Nino/La Nina.

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Global dataset of deep current velocities derived from Lagrangian data of Argo fl oats

Hiroshi Yoshinari, Nikolai Maximenko and Peter HackerAsia-Pacifi c Data-Research Center, IPRC/SOEST, University of Hawaii, 1680 East West Road, POST #401,

Honolulu, HI 96816, USA1997-2005, [email protected]

PosterData of the global array of 2440 Argo fl oats are used to assess velocities of horizontal currents at parking depths of the fl oats. A set of algorithms of varying complexity is developed to reconstruct the three-dimensional trajectory of a fl oat based on its satellite-measured coordinates at the sea surface and baroclinic structure of the ocean inferred from the CTD profi le taken by the fl oats. Corrections include estimates of the actual surface arrival and diving times and drift of actual parameters from their preprogrammed values. Data of about 120,000 cycles from different types of Argo fl oats stored in the eight Data Assembly Centers are unifi ed and merged into the velocity (fl oat displace-ment and error) archives at the sea surface and at the individual parking depths. This presentation announces publicavailability of the velocity data from the IPRC/APDRC. To illustrate the characteristics of our product we also present the global map of mean dynamic topography at the sea surface and at the level of 1000 dbar and regional maps at1500 and 2000 dbars. Feasibility of reconstruction of monthly three-dimensional velocity fi elds is discussed based on modality of vertical structures and on coherence of the pressure anomaly at different depths with changes in thealtimeter-tracked sea level.

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Argo program and data application in METRI/KMA

Yong-Hoon Youn, You-Soon Chang, Homan Lee, and Ji-Ho KimMarine Meteorology and Earthquake Research Laboratory, Meteorological Research Institute,, Seoul 156-720,

South [email protected]

PosterMETRI (Meteorological Research Institute) / KMA (Korea Meteorological Administration) ARGO program was success-fully launched in 2001 year. The total number of Argo fl oats deployed by us reached 70. They have been deployed mainly in the East (Japan) Sea and western Pacifi c. We have a plan to deploy 15 fl oats ever year in order to expand the array in the same region. We receive all Argo data from the real-time mode and distribute the data through own web-based system (http://argo.metri.re.kr). Since 2003 year, METRI has also operated the RTQC (Real Time Quality Control) sys-tem, which delivers QCed data with TESAC and NETCDF format to WMO countries and GDACs (Global Data Assembly Centers) via GTS and ftp, as a function of DAC (Data Assembly Center), the name of “KM”.

With trajectories calculated from Argo data deployed by KMA, we check the cyclonic boundary current along the Korean and Japanese coast, anti-cyclonic current on the Korea Plateau, and high variability in the Ulleung basin. As for the west-ern Pacifi c, the Kuroshio-trapped signals are notable. Argo data will ultimately be used through data assimilation in ocean prediction model. Therefore, we are concentrating on the development of ocean circulation model and data assimilation techniques as well as data application study.

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An anticyclonic eddy observed by Argo Profi ling fl oat east of Mindanao

Hui Zhou1,2 Jian-Ping Xu2 , Pei-Fang Guo3 and Mao-chong Shi3, Zeng-hong Liu2

1, Institute of Marine Environment, Ocean University of China2 Laboratory of Ocean Dynamic Process and Satellite Oceanography, Second Institute of Oceanography, SOA

3Institute of Marine Environment, Ocean University of China

PosterAn anticyclonic eddy was observed by the Argo profi ling fl oat 5900224 which was deployed at 8.7°N, 129.9°E on 3 Janu-ary 2003 by the China ARGO Project, here we call it “Mindanao Anticyclonic Eddy (MAE)”. Both the trajectory and the parking-depth (1500db) velocity fi eld estimated from fl oat 5900224 show that there was an anticyclonic eddy just east of Mindanao coast where the Mindanao cyclonic Eddy(ME) normally exists. The MAE is circular in shape with a diameter of 180km and the tangential velocity of the edge at parking depth is 14.0cm/s with the rotation period of about 46days. The eddy-resolving, 1/10th-degree, 54 level OFES (Ocean General Circulation Model for the Earth Simulator) driven by climatological winds well simulated the MAE. In the annual mean, the size, the averaged tangential velocity at 1500db and the rotation period of the simulated MAE agree well with the observations. Model simulation suggests that the MAE lies between 300-1500m with the core depth of 500-800m, and the fl ow pattern derived from fl oat 5900224 and the altim-eter data also indicate that the MAE is an intermediate feature. The velocity fi eld estimated from fl oat 5900224 at parking depth bears little resemblance to that at surface suggests that energy source of the eddy is not local wind forcing, or instability of local upper-ocean currents.

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Venice, March 2006 - Argo · Venice, March 2006 Welcome to the Second Argo Science Workshop. At the...

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Transcript of Venice, March 2006 - Argo · Venice, March 2006 Welcome to the Second Argo Science Workshop. At the...