IARC Technical Report #9 Report of the NABOS 2015 Expedition

Activities in the Arctic Ocean

With support from:

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TABLE OF CONTENTS

PREFACE ............................................................................................................................................................4

I.1. INTRODUCTION (I. Polyakov, IARC)......................................................................................................5

I.2. RESEARCH VESSEL ..................................................................................................................................5

I.3. CRUISE TRACK (V. Ivanov, AARI)..........................................................................................................8

I.4. SCIENTIFIC PARTY (V.Ivanov, AARI) .................................................................................................10

I.5. METEOROLOGICAL AND ICE CONDITIONS (Ivanov, AARI, Repina, IFA, Masanov, AARI) ..12

I.6. OBSERVATIONS .......................................................................................................................................13 I.6.1. SEA-ICE OBSERVATIONS (A. Masanov, AARI)............................................................................13 I.6.2. OBSERVATIONS OF AIR-ICE-OCEAN INTERACTIONS (I. Repina, IAF) .............................14

I.6.2.1. Introduction.....................................................................................................................................14 I.6.2.2. Instruments......................................................................................................................................15 I.6.2.3. Results .............................................................................................................................................16

I.6.3. OCEANOGRAPHIC OBSERVATIONS ..........................................................................................22 I.6.3.1. CTD measurements.........................................................................................................................22

I.6.3.1.1. Approach (V.Ivanov, AARI/IARC).........................................................................................22 I.6.3.1.2 Equipment .................................................................................................................................22 I.6.3.1.3 Preliminary results (V. Ivanov, AARI/IARC) ..........................................................................23

I.6.3.2. Mooring observations .....................................................................................................................26 I.6.3.2.1. Introduction (I. Polyakov, IARC) ............................................................................................26 I.6.3.2.2. Mooring recoveries ..................................................................................................................26

I.6.3.2.2.1. Logs of mooring recoveries (I. Waddington) ...................................................................27 I.6.3.2.2.3. Preliminary results (I. Polyakov, IARC; A. Pnyushkov, IARC) ......................................32

I.6.3.2.3. Mooring deployments ..............................................................................................................46 I.6.3.2.3.1. Logs of central-eastern Laptev Sea mooring deployments (I. Waddington)....................47 I.6.3.2.3.2. Notes of Cape Arkticheskiy mooring deployments (T. Kanzow) ....................................48

I.6.3.3. Lagrangian drifters (V. Ivanov, AARI) ............................................................................................51 I.6.4. HYDROCHIMICAL OBSERVATIONS (M. Alkire, APL/UW) ......................................................53

I.6.4.1. Background and purpose.................................................................................................................53 I.6.4.2. Personnel .........................................................................................................................................53 I.6.4.3. Instruments and equipment .............................................................................................................53 I.6.4.4. Standard operations.........................................................................................................................54 I.6.4.5. Sample collection............................................................................................................................54 I.6.4.6. Dissolved oxygen............................................................................................................................55 I.6.4.7. Preliminary Results .........................................................................................................................57 I.6.4.8. Data availability ..............................................................................................................................57

I.6.5. BIOLOGICAL OBSERVATIONS (E. Ershova, IORAS/UAF; K. Kosobokova, IORAS)...........58 I.6.5.1. Sampling scheme ............................................................................................................................58 I.6.5.2. Sampling methods...........................................................................................................................58 I.6.5.3. Preliminary results ..........................................................................................................................59

REFERENCES ..................................................................................................................................................61

Acknowledgments ..............................................................................................................................................61

APPENDIX I: List of NABOS 2015 stations (colors identify specific transects) .........................................62

APPENDIX II: Schematics of moorings recovered in 2015...........................................................................65

APPENDIX III: Schematics of deployed moorings ........................................................................................76

 

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GLOSSARY

Institutions and organizations:

AARI Arctic and Antarctic Research Institute, St.Petersburg, Russia

APL Applied Physical Laboratory, University of Washington, USA

AWI Alfred-Wegener Institute, Bremerhaven, Germany

BAS British Antarctic Survey, UK

BU Bangor University, UK

EEZ Exclusive Economic Zone

EU European Union

GI Geophysical Institute, University of Alaska Fairbanks, Alaska, USA

IABP International Arctic Buoy Programme

IAF Institute of Atmospheric Physics, Russian Academy of Science, Moscow, Russia

IARC International Arctic Research Center, University of Alaska Fairbanks, Alaska, USA

IORAS P.P.Shirshov Institute of Oceanology, Russian Academy of Sciences, Moscow, Russia

IOS Institute of Ocean Sciences, BC, Canada

LU Laval University, Quebec City, Quebec, Canada

NPI Norwegian Polar Institute, Norway

NOCS National Oceanographic Center, Southampton, UK

OM Oceanetic Measurement Ltd., Sidney, BC, Canada

POI V.I.Il’ichov Oceanographic Institute, Far Eastern Branch of the Russian Academy of Sciences

RAS Russian Academy of Sciences

SAMS Scottish Associationn of Marine Science, UK

UAF University of Alaska Fairbanks, Alaska, USA

UCL University College London, UK

UW University of Washington, USA

VNIRO All-Russian Research Institute of Fisheries and Oceanography

WHOI Woods Hole Oceanographic Institution, USA

Equipment:

ADCP Acoustic Doppler Current Profiler, an instrument that measures these parameters.

BPR Bottom Pressure Recorder, an instrument that measure these parameters.

CTD Conductivity, Temperature and Depth; an instrument that measures these parameters.

MMP McLane Moored Profiler

SBE Seabird, a Seattle based company that produces a number of oceanographic instruments

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PREFACE

In 2015, we conducted our tenth NABOS cruise aboard the Russian Research Vessel Akademik Tryoshnikov, and the NABOS observations that resulted have provided vital information about the state of the boundary current system, thus closing a substantial observational gap. For example, observational data collected under NABOS’ auspices have been in great demand: researchers from fifty-seven institutions in eleven countries have visited the NABOS data web page at http://nabos.iarc.uaf.edu/data/registered/main.php. NABOS data have been requested by the Hadley Centre Meteorological Office for inclusion in their global data set, and the NOAA National Ocean Data Center (NODC) added NABOS data to the publicly available World Ocean Database archive. Researchers from the Massachusetts Institute of Technology also visited our NABOS Data web page to acquire data for data assimilation, and University of Maryland scientists downloaded NABOS data for reanalysis of ocean circulation. Further, there were numerous requests for data for validation of ocean models, and we have provided NABOS data to many individuals upon request. This high demand for NABOS data demonstrates the utility of this program. NABOS observations have been instrumental to documenting all stages of ongoing Atlantic Water warming. They have also been used in atmospheric, ice, biological, geochemical, and oceanographic studies, and have led to more than fifty papers. During our 2013 cruise, we successfully deployed nine moorings in the Eurasian Basin of the Arctic Ocean; six of these moorings formed a cross-slope array along the ~125oE meridian spanning from a 250 to 3900 m depth range. All but one mooring were recovered during this 2015 cruise. Another extensive mooring deployment program, supported by joint IARC/AWI efforts, was conducted in summer 2015. Our multidisciplinary observational program—including chemical, biological, atmospheric, and ice observations, and complemented by moorings and buoys measurements—will help assess the ocean's role in climate change. These observations are therefore critical to the Arctic Ocean observational network.

Igor Polyakov Igor Ashik Vladimir Ivanov

US Principal Investigator Russian Principal Investigator Cruise Chief Scientist

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I.1. INTRODUCTION (I. Polyakov, IARC)

Our 2015 Arctic research cruise aboard the RV “Akademik Tryoshnikov” was the tenth expedition under the aegis of NABOS (the Nansen and Amundsen Basins Observational System) conducted by the International Arctic Research Center (IARC) at the University of Alaska Fairbanks (UAF) and the Applied Physics Laboratory (APL) of the University of Washington (UW), in partnership with the Arctic and Antarctic Research Institute (AARI, St. Petersburg, Russia) and Alfred Wegener Institute (AWI, Bremerhaven, Germany). The main goal of this NABOS project is to provide a quantitative assessment of circulation and water-mass transformation along the principal pathways transporting water from the Nordic Seas to the Arctic Basin. Specific features of the 2015 NABOS cruise, in addition to our “standard” cruise program, were our extensive mooring program and the eastward extension of our traditional area from the eastern Eurasian Basin to the northern East Siberian Sea. New, unique scientific data collected along the Eurasian and Makarov basin continental margin under extreme climatological conditions will be vital for understanding Arctic climate change. Eight moorings were recovered, and thirteen were deployed. Unfortunately we could not locate one of our moorings (M5), off Severnaya Zemlya; there is, however, a chance that a more extensive search on a future cruise will help recover this mooring. Due to a lack of ship time, we also did not have a chance to approach mooring M9, which has been deployed in the northern East Siberian Sea during the summer of 2008. We maintain hopes for the recovery of this mooring as well.

Our observations suggest that, even though the warm pulse of Atlantic origin water which entered the Arctic Ocean in the early 2000s has passed its peak, this intermediate (150-900 m depth range) water layer is still anomalously warm. Mooring observations suggest a strong, ~5Sv (1Sv = 106 m3/s), along-slope water transport in 2013-2015. They also showed strong ventilation of the Atlantic Water in summer due to, probably, enhanced shelf-basin interactions under ice-free conditions.

I.2. RESEARCH VESSEL

The Russian RV Akademik Tryoshnikov (Figure I.2.1) has been chartered by UAF to carry out oceanographic research over the continental slope of the Siberian Arctic shelf. This ship is operated by the Arctic and Antarctic Research Institute (AARI). RV Akademik Tryoshnikov is a powerful, conventionally-propelled ship, constructed in 2012 at the Admiralty Shipyard, St.-Petersburg, Russia. It was intended for work in Arctic and Antarctic conditions.

Figure I.2.1: RV Akademik Tryoshnikov

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The ship’s main technical characteristics are presented in Table I.2.1. In open water and broken ice, the ship can move forward and backward. Meanwhile in consolidated ice, the ship cannot break ice when moving backward. Four thrusters (two at the bow and two at the stern) provide high maneuverability of the ship over short distance. Pumps can move 74 tons of water per minute between ballast and heeling tanks. Fresh water is provided from a vacuum distillation apparatus heated by exhaust gases, which is supplemented by a reverse osmosis apparatus; a maximum of 80 tons per day can be produced. There are two helicopter decks. The main one is located at the stern. It allows full servicing of a mid-size helicopter. The auxiliary helicopter deck is located at the bow. It may be used for download/upload without helocopter landing on the deck. Safety equipment includes two fully-enclosed lifeboats and four inflatable life rafts (total capacity 140 persons). The ship is equipped with 3 deck cranes. Forward crane may operate on both sides and lift up to 10 tons. Two aft cranes can lift up to 5 tons. Bow crane may reach to a distance up to 25 meters off the ship. The aft cranes may reach up to 15 meters off the ship, but may not reach the far side of the helicopter deck at the stern.

Table I.2.1: Main technical characteristics of RV Akademik Tryoshnikov

Because of the poor configuration of the main deck of the ship, from where her oceanographic winches and A-frame are operated, a decision was made to install a set of NABOS equipment, including an A-frame, LEBOS winch, and HAWBOLDT capstan on the helicopter deck. Our 2015 cruise proved this decision correct. The LEBUS double-drum electric oceanographic winch (Figure I.2.2, left;

Displacement 16701 t (full load)

Draft 8.5 m

Breadth 23.25 m

Length 134 m (overall)

Builder Admiralty shipyard, St.Petersburg, RUSSIA, 2012

Main engines power 17400 kWt

Maximum endurance

(days)

limited by fuel capacity at service speed – 80, by food – 70, by fresh water

working desalters – 80

Fuel IFO-30 for main diesel sets, MGO for auxiliary generator sets

Fuel storage 2800 ton IFO-30 and 600 ton MGO

Hull thickness 45 mm where hull meets ice (the ice skirt) and 22-35 mm elsewhere

Maximum Speed 16 knot in calm open water

Operational Speed 14 knot in calm open water

Speed in ice 2 to 10,0 knots depending in ice thickness and concentration (in 1m thick

level ice the speed is 2 knots)

Classification class РМРС – КМ Arc 7 [2] AUT2, special purpose ship

Operating range 10 500 nautical miles (19 500 km) at 16 knot (30 km/h)

Anchors 2 weighing 6 tons each, with 300 m chains, and one spare

Life saving equipment 140 people

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manufactured by LEBUS Engineering International Ltd., England) was installed for deploying/recovering moorings. The winch’s electric motor power is 7.3 KW. Each drum capacity is 3500 m of 0.3-inch cable, with the left drum used only for mooring recovery and the right drum with a spooling mechanism and a 3000-m long mechanical cable for carrying the CTD probe, nets, and trawl. A HAWBOLDT C15-40 horizontal capstan (manufactured by HAWBOLDT Industries, 1989, Ltd., Canada) was placed near the LEBUS winch (Figure I.2.2, right). This capstan is equipped with an 11.2 KW two-speed Toshiba electric motor, and is used for mooring deployment/recovery. The horizontal drum diameter is 40”. The A-frame was installed offset from the center line of the helicopter deck, in order to better match deck beams underneath (Figure I.2.3). All these devices were welded to the helicopter deck in Kirkenes, Norway by KIMEK specialists.

Figure I.2.2: (left) LEBUS double-drum oceanographic winch and (right) HAWBOLDT C15-40 horizontal capstan.

Figure I.2.3: NABOS A-frame installed on the helicopter deck of RV Ak. Tryoshnikov.

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I.3. CRUISE TRACK (V. Ivanov, AARI)

The overall research area for the cruise included the Eurasian and Makarov continental margin, from St. Anna Trough to the East Siberian Sea (Fig. I.3.1). This operation area overlapped partly with the Russian Exclusive Economic Zone (EEZ)—as a result, permission to work within the EEZ was essential.

RV Akademik Tryoshnikov was loaded and mobilised in Kirkenes, Norway on August 18, 2015. Loading was conducted with ship cranes and a shoreside mobile crane working simultaneously, and was quite efficient. NABOS winches and an A frame were welded to the helicopter deck by the KIMEK shipyard company and connected to the ship’s electrical supply by ship engineers. All equipment were tested in port for correct rotation and load lifting. The majority of mooring hardware had been supplied to the ship and prepared for deploy in June 2015 at Kirkenes. Refurbished NABOS instruments were also available for the cruise. This required the recovery and recycling of most instruments deployed from 2013. The majority of onboard recycling was for steel and glass buoyancy. Calibrations were made using CTD by lowering sensors. Other tests and calibrations were carried out in the hangar. New anchors were provided by Alfred Wegener Institute (AWI).

The research vessel left Arkhangelsk at 00:00 on August 16, 2015 and set sail to Kirkenes, Norway, where she arrived on the evening of August 17. The ship left Kirkenes at 00:00 a.m. on August 19, 2015, after uploading/mounting of equipment and boarding of the non-Russian portion of the expedition team. On August 21, the ship arrived at port Arkhangelsk, where the remaining expedition team embarked. On August 23 at 1:00 p.m., the cruise began a four-day segment toward Severnaya Zemlya Archipelago, in the northern Kara Sea. On August 27, the vessel arrived at the M5 mooring position. Several attempts from different positions were made to communicate with M5 via acoustic channel; none were successful. After four hours of hunting in an ice-covered sea, the search for this mooring was halted. The test CTD was cast, and the ship moved to the M6 mooring, ~50 miles to the east from the M5 mooring position. Mooring M6b was recovered successfully, despite difficult 80-90 % ice concentration conditions. Over the next two days, seven CTD casts were made, and four moorings from our German colleagues at AWI were successfully deployed, completing a section crossing the upper part of the continental slope.

Figure I.3.1: NABOS 2015 cruise map

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On August 1, the ship reached the M11 mooring position over the upper continental slope of the Laptev Sea, at ~126°E. During the next two days, five 2013 NABOS moorings were recovered successfully, and eleven CTD casts were made along the 126°E meridian. Worsening weather on the evening of September 2 (wind speed up to 18 m/s and high seas) put CTD and mooring operations on hold, until the early morning of September 3, when the M15a mooring was recovered in the face of continuing harsh weather conditions (swell height up to 2 m, ~10 m/s wind speed). The rest of that day, six CTD casts at the northern end of the cross-slope transect were conducted, and the M16a mooring was recovered. The next day, after ten hours of searching for an appropriate ice field, the first ITP and O-buoy were deployed onto pack ice. Over September 6-8, the cross-slope transect at 142°E was completed, the M3e mooing was recovered, and the M3f mooring was redeployed. On September 9, the ship began the transect along 160-165°E, from the shelf of the East Siberian Sea. This transect was completed the morning of September 12, and afterward, a cluster of four buoys was deployed on ice ~50 miles to the northeast of the northern transect point. From the evening of September 13 until that of September 16, the transect at 175°E was covered, from the deepest point over the Chukchi Plateau toward the shelf of the East Siberian Sea. After, the ship sailed toward the central Laptev Sea, where on September 18 the deployment of moorings along 126°E began; the shallowest M11b was first deployed over the continental margin at ~250 m depth. The next day, moorings M12b and M13b were deployed, and two CTD casts were made, before the weather became too harsh for further operations. The rest of that day and night, the ship continued moving slowly to the north. The next morning weather improved, and the M14b mooring was recovered and redeployed.

On September 21, all operations at the 126°E meridian were completed, after deployment of the M15b mooring, and the ship began her westward transit. The ship reached the middle point of the transect of 94°E at 12 p.m. on September 23. Three AWI/IARC moorings were deployed, and four CTD casts were carried out over the next forty-eight hours. On the evening of September 25, the ship began the final transect across St. Anna Trough. This was accomplished at 7:30 p.m. the next day. The ship then began steaming towards Arkhangelsk, where she arrived safely at 11:00 a.m. on September 30.

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I.4. SCIENTIFIC PARTY (V.Ivanov, AARI)

#

Name Team Position Affiliation E-mail Country

1 Alexeev, Vladimir meteo Scientist IARC alexeev@iarc.uaf.edu USA

2 Alkire, Matthew chem Scientist UW malkire@apl.washington.edu USA

3 Artamonov,

Alexander hydro Team leader AARI RUS

4 Ashik, Igor admin Co-Chief sci AARI ashik@aari.ru RUS

5 Bahr, Frank tech Moor. tech WHOI fbahr@whoi.edu USA

6 Baumann, Till tech Moor. tech IARC tbaumann@geomar.de GER

7 Bayburin, Ruslan ice Scientist IO RAN RUS

8 Dunn, Jim tech Moor. tech WHOI jdunn@whoi.edu USA

9 Engicht, Carina tech Technician AWI Carina.Engicht@awi.de GER

10 Ershova, Elizaveta bio Team leader IO RAN eershova@alaska.edu

RUS

11 Fedorenko, Natalia ice Scientist AARI

RUS

12 Gagarin, Vladimir bio Scientist IO RAN gagarin@ocean.ru RUS

13 Goszczko, Ilona hydro Scientist IO PAS ilona_g@iopan.gda.pl POL

14 Hargesheimer, Theresa chem Scientist AWI theresa.hargesheimer@awi.de GER

15 Ivanov, Vladimir admin Chief Scientist IARC vivanov@iarc.uaf.edu

RUS

16 Kanzow, Torsten tech Scientist AWI Torsten.Kanzow@awi.de GER

17 Keen, Peter tech Moor. tech IARC pwk@keen-marine.com NZ

18 Kessel, Anastasia meteo Scientist AARI nastena_post.92@mail.ru RUS

19 Khavina, Elena meteo Scientist MFTI RUS

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20 Kulagin, Dmitry bio Scientist IO RAN kulagin.dima@gmail.com RUS

21 Lee, Ho Won chem Scientist PNU slrkwsx70@gmail.com KOR

22 Markova, Natalia chem Scientist AARI marknatalia@yandex.ru RUS

23 Masanov, Andrey ice Team leader AARI masanov@aari.nw.ru RUS

24 Monsees, Mathias tech Moor. tech AWI Matthias.Monsees@awi.de GER

25 Murzanaev,

Sergey hydro Scientist AARI RUS

26 Naber, Dan chem Scientist IMS ddnaber@alaska.edu USA

27 Pnyushkov,

Andrey tech Scientist IARC andrey@iarc.uaf.edu USA

28 Polkin, Vasilii meteo Scientist AARI RUS

29 Rauschenberg,

Carlton tech Moor. tech Bigelow carlton@bigelow.org USA

30 Repina, Irina meteo Team leader IAP RAS repina@ifaran.ru RUS

31 Rohde, Jan tech Technician AWI der.herr.rohde@web.de GER

32 Sandalyuk, Nikita hydro Scientist SPBGU nikitasandaliuk@gmail.com RUS

33 So Hyun, Ahn chem scientist PNU wiseash@naver.com KOR

34 Stockwell, Dean chem Scientist IMS dastockwell@alaska.edu USA

35 Timoshina, Alena hydro Scientist RGGMU RUS

36 Torzunova,

Nadezhda chem Scientist VNIRO ntorg@list.ru RUS

37 Varentsov, Michail meteo Scientist IFA RAN

RUS

38 Waddington, Ian tech Team leader UK ian.waddington@yahoo.co.uk UK

39 Whitledge, Terry chem Co-Chief sci IMS terry@ims.uaf.edu USA

40 Wischnewski, Laura bio Scientist AWI Laura.Wischnewski@awi.de GER

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I.5. METEOROLOGICAL AND ICE CONDITIONS (Ivanov, AARI, Repina, IFA, Masanov, AARI)

Weather conditions during the cruise were variable. The air temperature was ~0 °C on average (Fig. I.5.1). At the end of the cruise, however, the temperature dropped below -10 °C. The surface water temperature was well above freezing in the open water, while near freezing under the ice. High humidity in the MIZ caused icing of meteorological instruments, thus biasing measurements of sea-air interaction.

Extended areas of open water led to the development of high waves from strong winds. There were several episodes during the cruise when strong winds (up to 20 m/s) were observed as the ship operated in the open water. In two instances, high waves interrupted rozetta sampling at cross-slope transects. Ice conditions during the cruise were characterized by the existence of a well pronounced marginal ice zone (MIZ), which separated zones of consolidated pack ice with 100 % concentration from open water areas (see Fig. I.5.2, right).

day of month day of month

Figure I.5.1: Surface air temperature (left) and wind speed (right) during the cruise.

Figure I.5.2: (Left) Ice conditions along the ship route at transect 5. (Right) SSM/I ice map on September 8, 2015.

Depending on the area (see Fig. I.5.3, left as an example), transects and mooring operations were carried out either in ice-free waters or in the pack ice. Ice thickness was on average 40-100 cm and predominantly made up of first-year ice, substantially rotten and melted from below. The thickest ice was encountered at the easternmost area reached by the vessel—to the east of 160ºE, and at the northernmost part of the transect near Cape Arktichesky.

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I.6. OBSERVATIONS

The NABOS-15 program included routine CTD observations, water sampling, recovery, and deployment of oceanographic moorings and buoys, as well as hydrochemical, biological, ice, and meteorological observations. The operational map for the NABOS-15 RV Akademik Tryoshnikov cruise is shown in Figure I.3.1; measurements made during the cruise are listed in Appendix I.

I.6.1. SEA-ICE OBSERVATIONS (A. Masanov, AARI)

Specialized sea-ice observations included visual, radar-based, and satellite observations.

Visual ice observations: Regular sea-ice observations began on August 27, when RV Akademik Tryoshnikov encountered the first ice floes, and finished on September 25, in the northern Kara Sea. Regionally, observations were divided into two subareas: “in the region” (within the range of horizontal visibility and radar screen area) and “on the route” (within the zone of three vessel widths on each side). The sea-ice patterns for these two areas are characterized by the following ice-cover parameters: ice concentration (total and partial for all stages of development); stages of development and forms (according to stages or predominance); ridge concentrations; average and maximal hummock heights; predominant ice thickness (en route only); predominant snow height (en route only); surface contamination concentration; ice pressure; percentage of rafted ice (for new and young ice); existence and orientation of openings (leads, cracks) in the ice cover and their average width; meteorological parameters such as visibility, snow, fog, and icebergs (height, width, coordinates); polar bears and their footsteps; and seals. Regular shipborne radar was used to estimate configuration of ice zones within the area of navigation. An example of a map with identified ice characteristics for the ship’s route is shown in Figure I.5.2.

There were several ship systems used for sea-ice observations, including the ship navigation system ECDIS Transas, ship navigation devices like radars, lags, rangefinders, and the ship automatic meteorological station MAWS 420 (Vaisala, Finland), etc. For analysis of sea-ice conditions in the range of ship operations, satellite images received by ship station Dartcom were used. Various satellite images were used to determine current ice conditions, and to choose the easiest path to the research area (Figure I.6.1.1). In addition, weather forecasts for three to four days in advance as well as wave forecasts were obtained from the AARI. During sea-ice observations from the ship bridge, the Sigma 6 ship locator (Rutter) was used for defining boundaries for ice of different concentrations within 1-10 miles, the positions of ice floes and leads, and the number and positions of icebergs. One example of the use of this system is shown in Figure I.6.1.2.

Figure I.6.1.1: (Left) NOAA satellite image dated August 30, 2015. (Right) Mosaic of Sentinel 3d

satellite images from September 8, 2015. Red от 8 сентября 2015 года. Red lines show recommended ship trajectory, triangles show CTD stations.

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Figure I.6.1.2: Ice floes (blue line), ship trajectory (red line), and position of ITP deployment (yellow triangle) on the ice radar display.

I.6.2. OBSERVATIONS OF AIR-ICE-OCEAN INTERACTIONS (I. Repina, IAF)

I.6.2.1. Introduction

The following objectives defined the design of our experiments and the choice of instrumentation:

• Measurements of the surface heat budget. Analysis of energy exchange between the atmosphere and the surface, using measurements of turbulent fluxes (latent and sensible heat fluxes, momentum fluxes) and radiation fluxes in the surface layer of the atmosphere under different stability conditions. Determination of exchange coefficients in the aerodynamic bulk formulas, surface roughness parameter with respect to the type of the surface, and meteorological conditions.

• Analysis of temperature and structural characteristics of the surface, and its influence on the atmospheric boundary layer. Validation of satellite-derived surface temperatures.

• Observation of atmospheric conditions and boundary layer dynamics in the marginal ice zone by remote sensing and contact techniques. Studies of Arctic Cloud Radiative Forcing.

• Investigation of time-space variability in atmospheric ozone and aerosol. Study of optical, microphysical, and chemistry properties of Arctic aerosol.

The following in situ observations were carried out during the cruise:

• Direct high-frequency measurements of air temperature, and horizontal and vertical components of wind speed above the ice and open water. These data were used for calculation of turbulent fluxes,

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roughness parameter of the surface, and atmospheric stability. Measurements were carried out when the ship was moving;

• measurement of sea surface temperature in the infrared (IR) range;

• standard meteorological measurements;

• measurements of temperature profiles in the atmospheric boundary layer;

• measurements of all radiation budget components (longwave and shortwave, outcoming and downwelling radiation);

• measurements of variability in atmospheric ozone content and optical, microphysical, and chemistry properties of atmospheric aerosol.

I.6.2.2. Instruments

To carry out the measurements described above, the following equipment was used:

A USA-1 Sonic thermo-anemometer (METEK Co.), for measuring fluctuations of three components of wind speed and temperature fluctuations at frequency of 10-50 Hz. A HEITRONICS KT19 II-Series infraRed radiometer, for measuring skin temperatures of the sea surface . A STS 360 inclinometer and three ADXL330 axis accelerometers and rate gyros, for measuring ship motions in three dimensions. GERMICOМ video camera (web cam), for sea surface conditions visual control. Images were recorded by a laptop computer for subsequent analysis. WX150 weather station (AIRMAR, USA) (Wind Speed, Gust and Direction, Air Temperature, Relative Humidity, Air Pressure, ship motion information). MTP-5 meteorological temperature profilemer (АТЕХ, Russia), used for remote measurements of temperature profiles for atmospheric layer 0-1000 m. Kipp & Zonen radiation complex with two СМP21 pyranometers (shortwave radiation measurements) and two pyrgeometers CGR-3 (longwave radiation measurements). GOPRO HERO 3+ Silver Edition photo/web camera а for surface and sky conditions control. Nefelometer (aerosol particles meter) GRIMM (model 1.108) for aerosol particle control and Aethalometer for black carbon concentration. Ozonemeter M-4 Fotometer for optical aerosol depth

Locations of sensors are listed in Table I.6.2.1.

When the ship was moving, turbulent measurement equipment was installed on the bow at 10-m mast height (height of measurements: 15 m), to reduce ship hull effects. The signals from turbulence and motion sensors were sent to a PC-based data acquisition system including Labview (National Instruments). This system samples all data at 10 Hz, and after filtering out high frequency noises and low frequency trends, ship motion correction was applied to wind velocity data. For the temperature signal, it is well calibrated and sound virtual temperature effects can be reduced later. After these correction procedures, ten-minute eddy fluxes and statistics are obtained in real-time and filed, along with row turbulence data.

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Table I.6.2.1: Instruments installed on the Academic Treshnikov for the NABOS 2015 cruise.

Instrument Location

Weather station on bow

Ship motion system on bow

IR radiometer starboard, at a 30° angle to surface

Sonic anemometer USA-1 top of the 10-m foremast

Temperature profilemer MTP5 starboard

Web-camera starboard near radiometer

Kipp&Zonen starboard

Photo/web camera а GOPRO high deck

Aerosol measurements on bow

Ozone measurements high deck

A standard eddy covariance technique was applied for calculating turbulent fluxes [Edson et al, 1998]. Additional micrometeorological measurements were necessary to 1) monitor turbulent fluxes of momentum, as well as sensible heat during the NABOS campaign; and 2) compare these direct measurements with calculated results from simple flux gradient parameterizations [Foken, 1984]. The skin temperature calibration technique and calculation from microwave measurements are described in Cherny and Raizer [1998].

I.6.2.3. Results

Onboard measurements were carried out along the entire route of the icebreaker from August 23 to September 28, 2015. Figure I.6.2.1 shows the variability in the main meteorological parameters during these measurements. Table I.6.2.2 presents average, maximum, and minimum measured values. All values are given relatively to 10-m height. True wind speed and direction are calculated using navigation data (speed and direction of vessel movement). Figure I.6.2.2 (a and b) shows the average, maximum, and minimum values for wind speed and temperature for each day en route.

Table I.6.2.2: Average, maximum, and minimum values measured during the NABOS 2015 cruise.

Air temperature,

°C

Relative

humidity, %

Air pressure, hPa Wind velocity, m/s

min. -17 54.5 984 0.5

max. 9.3 100 1019.9 18.4

avg. -1.4 92 1009.8 7.6

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Figure I.6.2.1: Variability in main meteorological parameters from August 24 to September 25 from moving RV "Akademik Treshnikov."

Figure I.6.2.2: Average (thick solid line), minimum, and maximum (thin dashed lines) values of air temperature and wind speed for each day.

To estimate total and net heat flux between the ocean and the atmosphere, data for radiation balance measurements were used. The magnitude of shortwave radiation was low on average. Maximum values were 200-300 W/m2 at the beginning of the expedition. At the end of the observation period, maximum values decreased to 50-100 W/m2. This is a direct result of the height of the sun change. Shortwave radiation contributed to the net balance only during the first part of the cruise, when the midday height of the sun above the horizon was about 20°.

Daily average long-wave radiation balance at the surface has changed slightly, from 10 to 50 W/m2, due to the variation in low clouds amount. Figure I.6.2.3 shows the variation in radiation balance during the cruise. The contribution from long-wave radiation balance increased significantly during the final stage of the cruise, when the height of the sun was low.

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Figure I.6.2.3: Downward and upward shortwave radiation (Qdown and Qup), downward and upward longwave radiation (Fdown and Fup), net longwave (F net) and shortwave (Q net) radiation, total (B)

radiation balance and Sun height (h) for the whole measurement period.

Onboard measurements of turbulent characteristics were carried out continually en route. Using direct measurements of sensible and latent heat fluxes, momentum and surface roughness parameters were calculated. Unstable and neutral stratification was dominant during the cruise. Observations of sensible and latent heat fluxes and frictional velocity over the entire measurement record (above different types of ice) are presented in Figure I.6.2.4. When the ship was moving through ice, the air temperature was close to the ice surface temperature. When ice cover was absent, intensive energy exchange was observed. Positive heat fluxes (from the ocean to the atmosphere) were observed above leads and over the open water, while low fluxes were measured above perennial ice.

Figure I.6.2.4: Behavior of sensible (Sh) and latent heat flux (Lh) and frictional velocity (U*) for the whole measurement period.

Figure I.6.2.5 shows variability in energy exchange (flow of sensible and latent heat) along the route of the vessel. Intensification of exchange processes was observed in the southern part of the Laptev Sea, near

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the marginal ice zone of the western part of the Laptev Sea and the area of leads, and in the Barents Sea, where an anomaly in the surface temperature was observed.

Figure I.6.2.5: Sensible and latent heat flux (W m-2) variations during the cruise.

Figure I.6.2.6 shows the total heat balance for the entire route. As it should be in the summer, radiation balance is the main contributor to heat balance, via incoming short-wave solar radiation. The exception from this rule is the marginal ice zones and leads, where during the transition to the autumn-winter period, incoming solar radiation was practically zero. In these cases, turbulent balance is the main contributor to the total heat flux from the ocean to the atmosphere. Therefore, in open water and over the newly formed thin ice in the autumn-winter period, turbulent energy exchange is playing a key role in the total energy balance, while its value is negligible though the thick perennial ice.

A MTP-5 temperature profiler was used to study the atmospheric boundary layer temperature structure, and provided information about the temperature every 50 meters from the surface to 1000 meters depth in a quasi-continuous regime. Figure I.6.2.7 shows the temperature structure of the atmospheric boundary layer over the entire observation period. Change of cold and warm fronts is clearly visible at this plot, as well as cold and warm out-breaking, including the ice and open water in the marginal zones.

Figure I.6.2.6: Average total heat balance of the period of observation. Lnet - longwave radiation balance; Qnet - shortwave radiation balance; H, HL - turbulence latent and sensible heat fluxes.

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Figure I.6.2.7: Time vs. heigh section of atmospheric boundary layer temperature.

Atmospheric aerosol and gas contents were measured en route in various parts of the Arctic Ocean and the seas of the Eastern Arctic. According to measurements carried out from 24 August to 25 September 2015, average daily values of total ozone (TO) were in the range of 333-213 Dobson units. The average value of TO was 280 Dobson units. Variability from day-TO values was due to spatial and temporal changes. The negative trend reflects the seasonal decrease of ozone in the fall. Figure I.6.2.8 shows the spatial distribution of total ozone for the expedition. It is evident that TO values are decreased with time in all areas. For example, values obtained over the Laptev Sea at the beginning of the expedition were higher than the values obtained in the later period.

Figure I.6.2.8: Spatial distribution of total ozone (Dobson unit) along the route of the RV "Akademik

Treshnikov."

A series of the mass concentration of black carbon and aerosol number concentration were obtained. The contents of the aerosol were close to background values.

Direct measurement of sea surface temperature in ice-covered areas is labor-consuming. The application of contact methods is not always possible, and in the case of non-homogeneous surfaces (e.g., a combination of ice floes and openings), presents large errors. We attempted to restore surface temperature using remote infrared radiometric measurements. In Figure I.6.2.9 the surface temperature variations are

21

shown. Breaks in ice cover cause visible surface temperature variations. Basically, positive anomalies were observed that ensured positive values of heat fluxes. In the northern part of the Laptev Sea, the ship passed through a field of ice, covered with broken ice and leads, which resulted in significant variations in surface temperature.

Figure I.6.2.9: The space variation of sea surface temperature.

The main results of field work:

1. The characteristics of energy exchange (turbulent sensible and latent heat fluxes, momentum fluxes) for various typical conditions in the coastal regions of the Arctic over the different types of ice and open water surface in the summer and autumn periods were obtained.

2. The processes of energy exchange in the marginal zones were investigated. The predominance of the turbulent component in the total heat balance in the border area of ice and areas of leads was found.

3. The structure of the atmospheric boundary layer over the different types of underlying surface was studied. The effect of surface temperature and cloud conditions in the ABL dynamic was investigated.

4. Continuous monitoring of the temperature of the underlying surface was carried out. It allows to improve the methodology for calculating of the turbulent fluxes over the thermally non-homogeneous surface and to validate satellite data.

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I.6.3. OCEANOGRAPHIC OBSERVATIONS

I.6.3.1. CTD measurements

I.6.3.1.1. Approach (V.Ivanov, AARI/IARC)

Ninety-four CTD/LADCP casts were carried out during the cruise (see Appendix I). These stations were taken at six cross-slope transects, as shown in Fig. I.6.3.1. In the deep basin (>1500 m), one out of between three and four casts was to the bottom. The casts in between were to 1000 m. Casts were to a depth of 5 to 30 m above the seabed, depending on water depth. All samples were taken during the up-cast, and the device was always stopped at each sampling depth. At the test station, all equipment (including the ship-borne CTD winch and rosetta) was tested and proved its operational readiness. During the cruise, the winch operated without major problems, though several minor ones occur (malfunctioning of electronic controls, loss of electric power). These small problems were fixed promptly and did not lead to any substantial delays in operations.

Figure I.6.3.1: Scheme of CTD transects.

I.6.3.1.2 Equipment

Conductivity, Temperature, and Depth (CTD) profiles of the water column were made using a Seabird SBE911plus CTD system. This system measures conductivity, temperature, and pressure at a 24 Hz sample rate throughout the full water column or to pre-determined end points—typically 1000 m on this occasion. Given a normal descent rate of 60 m/min, or 100 cm/sec, this provides a vertical resolution of around 4-5 cm.

The CTD system also integrates other auxiliary sensor systems, including paired Dissolved Oxygen sensors; a Transmissometer; a Fluorometer and Turbidity sensor; a Photosynthetically Active Radiation (PAR) sensor; a SUNA Nitrate sensor; a downward looking Acoustic Doppler Current Profiler; and a Benthos sonar altimeter, to avoid collisions with the seabed. The 9plus underwater profiling system output can be logged and monitored in real time on computers aboard the ship, via a conducting cable to the 11plus deck unit. The profiling sensor system was housed in a SBE32 24-way water sampling frame, carrying 24 × 10 litre OTE water sampling bottles. These can be closed remotely on demand from the 11plus deck unit. This allows samples for salinity, oxygen, and nutrients to be collected at discrete depths within a profile for comparison with electronic sensor outputs.

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All Seabird sensors had been returned to the manufacturer since the 2013 expedition for servicing and calibration, and stored unused since then. Technical descriptions for sensors, according to the specifications of Seabird Electronics, Inc., are presented in Table I.6.3.1. The full information can be downloaded from http://www.seabird.com/sbe911plus-ctd.

Table I.6.3.1: Seabird SBE911plus technical information.

Sensors Parameter Range Accuracy Typical stability (per month) Resolution

SBE 4C Conductivity 0-9 S/m 0.0003 S/m 0.0003 S/m 0.00004 S/m SBE 3T Temperature -5 to +35 °C 0.005 °C 0.0002 °C 0.0001 °C

Digiquartz® Pressure 6800 m +0.015 % of full scale range

+0.004 % of full scale range

+0.002 % of full scale range

SBE 43 Oxygen 120 % of Surface

Saturation

+2 % of Saturation

+0.5 % per 1000 hours

Wet Labs ECO-

FLNTUrtd

Chlorophyll and Turbidity

50 µ/l 50NTU 0.025 µg/l Chl

0.013 NTU

Wet Labs C-star

Beam Transmission (25 cm path)

650 nm (Red) 0.02 % Full Scale/hour 14 bit

Biospherical QCP-2350L

Cosine PAR sensor 400-700 nm 0.001 V 1 volt=1 × 1017

quanta/(cm2-sec)

Deep SUNA Nitrate

0.5-3000 µM (SW with T/S

corrs processing)

+2 µM

0.3 µM per hour Lamp time

(SW with T/S corrs processing)

0.3 µM (SW with T/S

corrs processing)

I.6.3.1.3 Preliminary results (V. Ivanov, AARI/IARC)

Potential temperature and salinity sections taken during the cruise are presented in Figs. I.6.3.2–I.6.3.7. Preliminary analysis of thermohaline property distribution at transects allows highlighting of several points that could be considered foundations for working hypotheses at the stage of more detailed data analyses. Sequential transects (2 and 3) along with similar sections taken in 2013 support an earlier proposed concept (e.g., Ivanov and Aksenov, 2013) about the rapid transformation of two branches of Atlantic Water (AW) between the confluence zone (north of St. Anna Trough) and the central Laptev Sea, due to isopycnal and diapycnal mixing between the branches. Detailed measurements during this cruise also demonstrated intensive interaction between two branches at the traverse of Cape Arkticheskiy (section 1). The Barents branch of AW submerges the Fram Strait branch and “pushes” it off slope. Similarly to September 2013, there is strong near-surface temperature maximum in the waters, associated with ice-free conditions that have existed for a long time during summer. However, contrary to 2013, in St. Anna Trough (section 6) this near-surface temperature maximum borders the subsurface pool that is filled with near freezing temperature waters. This such feature is presumably linked with the long duration of a southerly stretched “ice-tongue” in the western part of St. Anna Trough in summer 2015. Some signs of AW upwelling on the shelf are visible at the eastern transects (4 and 5). There are also some model-based indications (J. Zhao, personal communication) that these upwelling structures could be associated with a local cyclonic gyre in the AW layer at the southwestern slope of the Chukchi Plateau. However, additional analysis is required to determine exactly what drives these upwellings of AW.

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Figure I.6.3.2: Vertical cross-section of potential temperature (upper panel) and salinity (lower panel) at transect 1 (off Severnaya Zemlya, ~95°E, see location in Fig. I.6.3.1).

Figure I.6.3.3: Vertical cross-section of potential temperature (upper panel) and salinity (lower panel) at transect 2 (central Laptev Sea, ~125°E, see location in Fig. I.6.3.1).

Figure I.6.3.4: Vertical cross-section of potential temperature (upper panel) and salinity (lower panel) at transect 3 (off Novosibirskiye Islands, eastern Laptev Sea, see location in Fig. I.6.3.1).

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Figure I.6.3.5: Vertical cross-section of potential temperature (upper panel) and salinity (lower panel) at transect 4 (western East Siberian Sea, ~165°E, see location in Fig. I.6.3.1).

Figure I.6.3.6: Vertical cross-section of potential temperature (upper panel) and salinity (lower panel) at transect 5 (central East Siberian Sea, ~170°E, see location in Fig. I.6.3.1).

Figure I.6.3.7: Vertical cross-section of potential temperature (upper panel) and salinity (lower panel) at transect 6 (St. Anna Troufg, ~80.5°N, see location in Fig. I.6.3.1).

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I.6.3.2. Mooring observations

I.6.3.2.1. Introduction (I. Polyakov, IARC)

The primary goal of our mooring observations was to document water, heat, and salt transports and water mass transformations on the Siberian continental slope. Primary objectives included quantifying the structure and temporal variability of the main water masses and obtaining detailed information about AW layer dynamics and seasonal variations. A summary of the 2015 NABOS mooring operations is presented in Tables I.6.3.2, I.6.3.3 and I.6.3.4. Mooring schematics are presented in Appendices II and III. There are two types of moorings used by our program. One type uses the McLane Moored Profiler (MMP), designed and manufactured by McLane Research Laboratories, Inc. Technical information and description are available at http://www.mclanelabs.com. Our other type of mooring is conventional, consisting of Acoustic Doppler Current Profilers (ADCPs) and Seabird SBE37 Microcat CTDs.

I.6.3.2.2. Mooring recoveries

A map showing mooring positions planned for recovery during the summer 2015 NABOS cruise is shown in Figure I.6.3.8. Eight moorings were successfully recovered. Mooring M9 was deployed in summer 2008; there has been no opportunity to recover this mooring since then. This year, a combination of ice conditions and extremely limited funding precluded us from visiting this mooring site and confirming whether the mooring is still there. Further, mooring M5c was not found at its deployment position; see the next section for details.

Figure I.6.3.8. Map showing positions of moorings recovered during 2015 NABOIS cruise.

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I.6.3.2.2.1. Logs of mooring recoveries (I. Waddington)

M5c mooring recovery. 27-28 August 2015. On arrival at the site, this mooring was pinged by the Edgetech deck unit, but no reply was received from any of its three acoustic systems. The ship then moved off site by 1 km and repeated transmissions, again with no replies. The ship then moved back over the site and further transmissions were made as the ship drifted slowly. The ship is very quiet acoustically, and we expected to hear releases and the ELCAT upper mooring transponder easily. With no replies at all, the ship moved off, hopefully to return later in the cruise to try a box search. This proved impossible, as ice cover had increased greatly by that point. To test the acoustic deck unit’s performance, an acoustic release was placed on the CTD frame and lowered to 2000 m. Good replies and transponding were achieved, indicating the M5 mooring had moved off site, possibly due to an iceberg or deep ice keel. When deployed in 2013, this mooring had an increased anchor weight of 700 kg in water, and as the slope of the seabed was not steep, the possibility of it being moved by ocean current was not considered.

M6b mooring recovery. 30 August 2015. This mooring site was reached on the 30th of August, after steaming through ice to the M6b position. On arrival, it was possible to communicate with the mooring, both on the acoustic releasers and the upper mooring transponder. It was decided to triangulate the upper transponder (ELCAT), in order to get an accurate fix on the upper part of the mooring under ice. Using three transponding locations, a very accurate position was determined. The first release 43488 was commanded successfully, but the mooring did not appear to rise. Release 43486 was then commanded and a positive rise was indicated. There was no visual of the mooring, and ELCAT replies were intermittent, indicating close position to the surface under ice. The captain then carried out a slow speed ice clearing over the ELCAT position, and on the second approach by the ship the mooring was sighted, on the starboard side as the ULS buoy pack and on the port side as the releaser buoyancy. The ship stopped and backed up to 2 × glass showing on surface, and crew grappled 4 × 17 inch glass release support floats at 0345 h. Using a heavy lift grapnel, glass buoys were hauled in and the glass spheres then recovered onboard. The mooring was then hauled back carefully through and under ice blocks to the ULS—a backwards recovery, recovering the ULS at 0625 h. The releases left hanging overboard were then hauled onboard. Both had released but one had hung up, enabling the release chain and drop links to be recovered at 0637 h. Using the additional glass spheres of the acoustic releasers brought both ends of the mooring to the surface, which enabled this mooring recovery to be completed “backwards” from the releasers to the top ULS package, which minimized the chance of damage to the ULS with grappling for recovery. There was some minor damage to the ULS transducer guard ring as it moved through the loose ice, and one SBE-37 lost its top bracket as it came from under an ice block. The mooring hardware was otherwise in excellent condition.

M1_1a mooring recovery. 1 September 2015. On arrival at the mooring position in open water, the ELCAT transponder gave immediate replies, indicating close proximity at 280 m horizontal range. The releaser was triggered but was reluctant to release. The second releaser was then triggered, and the buoy was sighted soon after at 0817 h. The ship’s workboat was launched and a boat recovery undertaken, passing a recovery line from the ship to the boat. An efficient and quick attachment was achieved at 0820 h. The mooring recovered conventionally onto the winch, completing recovery at 0835 h. The acoustic releaser was still hanging onto the chain although in an open position—again, a slight misalignment, as with M6b. Some minor corrosion was seen on the 37-inch steel sphere, with significant biological growth on the sphere, instruments, and releasers.

M1_2a mooring recovery. 1 September 2015. The mooring releaser and ELCAT transponded immediately on arrival at the mooring position and indicated close proximity at 277 m. By straightforward ranging and observations of position on the bridge plotter, the buoy was released on the port side some 200 meters away. As weather had deteriorated, the use of the boat was precluded and so a recovery from aft, grappling from the lower deck and attaching to a line from the heli deck, was undertaken at 1348 h, with the recovery line hauled onboard. A conventional recovery was undertaken, winching onboard, and all was inboard by 1430 h. Instruments appeared in excellent condition, fouled by

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biological growth from the steel sphere to the acoustic releasers.

M1_3a mooring recovery. 2 September 2015. With the wind and sea state increasing, this mooring was located in position at 0129 h, at a range of 629 m to the ELCAT. Acoustic reception was good, and by adjusting the ship’s position, the range was closed to 195 m on the port side and the releaser completed. Response was good, indicating the mooring rising, and the buoy was sighted at 0215 h as predicted on the port side. Recovery operations were from aft, with grapple from the lower deck, attaching to line from heli deck at 0222 h. Hauling was then commenced with the winch and recovery went easily, with all onboard by 0341 h. Instruments were all in excellent condition, and no corrosion was observed on mechanical parts of the mooring.

M1_4a mooring recovery. 3 September 2015. This mooring recovery was not without incident, mainly due to marginal weather and an increasing sea state. The mooring was located on arrival with excellent acoustics by the ELCAT, indicating a mooring position at a range of 500 m. As the ship would not be able to hold position in the wind conditions, a recovery from the forward deck was undertaken. All equipment had been rigged previously for this possibility and readied. The ship was positioned across the wind at a range of 500 m from the mooring position and the acoustic releaser commanded, with the ULS buoyancy being sighted some 200 m on the starboard beam. Using the ship thrusters, the ULS buoy was placed alongside forward, where it was easily grappled and attached to the stern transfer line at 2253 h. As the buoy passed under the stern, the line from the ULS buoy to the steel subsurface caught on the portside rudder stock, and could not be freed, so the line between the two buoy packages was cut, securing the ULS package and clearing the subsurface buoy line from the rudder stock at 2311 h. The ULS and ADCP beneath were then recovered to the lower deck, and the steel sphere and remainder of the mooring was then hauled to the helicopter deck for a conventional mooring recovery. All of the mooring was inboard by 0112 h. The instruments were all in excellent condition, with no corrosion observed on the mechanical parts of the mooring.

M1_5a mooring recovery. 3 September 2015. The ship arrived at the mooring position with weather conditions marginal, wind 20 kts and sea swell 1 to 2 m. It was determined the conditions were not suitable for the workboat, which meant the Upper Ocean Array could be vulnerable alongside the ship. Recovery would then be conducted from lower aft deck, with the ship coming slowly astern on the mooring. The mooring was located at a range of 249 m to the ELCAT, and repositioned to 105 m on the starboard side. The ship was allowed to drift over the mooring and position with the mooring to the port side, all the time monitoring the acoustic ranges. When the range was indicated at 107 m, the releaser was commanded at 1200 h, and the mooring buoys sighted at 1201 h aft of the port beam. The ship maneuvered to place the buoy close under the stern, but unfortunately the ship ran over the array several times, resulting in the loss of parts of the Upper Ocean Array, which finally got caught under the ship. By hand hauling on the grapnel line around a cleat, the steel sphere buoy came out from under the ship, with the grapnel well tangled with thermistor array, and the loss of two thermistor loggers on the ship rail due to ship surge on swell. By continued hand hauling of the mooring recovery pick up eye, it was shackled into the winch, and the Upper Ocean Array remains were cut free and recovered at 1324 h. The mooring could then be hauled onboard, but with the wind conditions, the line was always streaming away from the ship, and the Hawboldt capstan had to be used as a puller to get line inboard for stopping off and recovery of the instruments. To recover the MMP in these conditions, the mooring wire had to be stopped off with come along stoppers at the MMP bumper at 1445 h. With the MMP instrument safely onboard, the recovery was straightforward all the way to the releasers, which were inboard at 1601 h.

M1_6a mooring recovery. 4 September 2015. This mooring was detected using acoustics at a horizontal range to the ELCAT of 39 m, effectively under the ship forward. The ship was allowed to drift off to a safe release range of 77 m, and with increasing range the releaser was commanded and released at 0822 h, with the buoys sighted 200 meters off the port beam at 0824 h. The steel buoy was under the port quarter and forward alongside the hull before the ship got it back to the stern for work boat pick up. Recovery commenced in increasing wind force, and using the ship’s work boat the thermistor chain was all

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successfully recovered into the boat, and transfer of the pick up line then hooked onto the steel buoy at 0857 h. The ship’s boat was then recovered onboard as the sea state increased. Recovery was conventional, with no problems encountered. All of the morring was inboard at 1117 h. The Upper Ocean Array was inspected, and the upper two sections were missing, with the 100 kg weak link at 20 meters severely strained and snapped. With the loss of the top of the flying thermistor array, the weak link had parted out under severe strain. All instruments and mooring components appeared in good condition.

M3e mooring recovery. 7 September 2015. On arrival at the mooring position at 0200 h, there was fog and poor visibility, ranging on the ELCAT at a horizontal range of 532 m, at which the conditions were too great for a visual sighting of a surfaced mooring. An acoustic triangulation was made to establish the exact position of the mooring, and by 0222 h the ship was positioned 34 m in horizontal range from the buoy. At 0229 h, the acoustic releaser was commanded, and the surfaced buoys were sighted 60 m off to port side at 0230 h. The ship’s workboat was launched and proceeded to pick up the Upper Ocean Array from the surfaced mooring. The recovery line was then passed to the boat, which attached it to the mooring for recovery. The boat was then recovered at 0249 h, and mooring recovery commenced at 0302 h. The mooring recovery went well, and all was inboard by 0405 h. Instruments were in good condition, though several SBE37s had top clamp bracket screws missing or loose. On deploy in 2013, this mooring had been towed to position for some time, which might have shaken these loose through strumming of the mooring line. All mechanical mooring components were in excellent condition. On checking the Upper Ocean Array, all sensors had been recovered.

I.6.3.2.2.2. Seabird instrument inter-calibration (P. Keen, Keen Marine Ltd.)

With the exception of a minimal selection of newly purchased instruments, all instruments recovered during the expedition were required for redeployment. Accordingly, instruments scheduled for redeployment were assessed in a variety of ways to ensure they were in a fit state to be redeployed. Where practical, this included conducting an inter-calibration of appropriate instruments. Inter-calibration is conducted by comparing a reference instrument with well-known calibration characteristics and collocated observations from another instrument, in order to derive calibration corrections for the latter. Instruments that suited this procedure on this expedition were the Sea-Bird microcats (SBE37) and thermistors (SBE56).

Inter-calibrations were conducted prior to instrument servicing, to avoid any bias introduced at the servicing stage, through handling or battery changes and to ensure that inter-calibration marked an endpoint to the deployment and that any changes in response could only be attributed to the deployment period.

Following downloading and safeguarding of deployment data, SBE37 instruments were grouped according to depth range. These were subsequently scheduled for a 9/11+ CTD cast to a depth dependent on the maximum pressure rating of the lowest rated instrument in the group. The microcats were programmed for the minimum sampling interval of ten seconds, and set for a delayed start that initiated sampling close to the scheduled beginning of the CTD cast. This was adopted as a means of conserving memory since original data had not, at this point, been erased. In the case of pumped microcats, a minimum conductivity frequency threshold was also set to prevent damage to the pump by running it in air.

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Table I.6.3.2: Summary of NABOS deep-water moorings recoveries in 2015.

M00RING   Date/s   Operation   Lat./Long.   Depth   Instruments  M1-­‐1a   26th  August  2013   Deployment   77  04.25247  N   250m   3  x  SBE37  

    1st  Sept  2015   Recovery   125  48.2878  E       1  x  ADCP  75kHz  M1-­‐2a   26th  August  2013   Deployment   77  10.3761  N   787m   1  x  SBE37  

    1st  Sept  2015   Recovery   125  47.5155  E       1  x  ADCP  300khz                       1  x  MMP  

M1-­‐3a   6th  September  2013   Deployment   77  39.286  N   1849m   1  x  SBE37       2nd  Sept  2015   Recovery   125  48.4014  E       1  x  ADCP  300khz                       1  x  MMP  

M1-­‐4a   8th  September  2013   Deployment   78  27.5431  N   2721m   4  SBE37       19th/20th  Sept  2015   Recovery   125  53.7583  E       1  x  ULS                       1  x  ISUS                       1  x  ODO/SBE37                       1  x  ADCP  300khz                       1  x  BPR                       1  x  ADCP  75kHz  

M1-­‐5a   28th  August  2013   Deployment   80  00.1986  N   3443m   1  x  ADCP  300khz       3rd  Sept  2015   Recovery   125  59.6729E       4  x  SBE37                       1xMMP                       15  x  SBE56  

M1-­‐6a   29th  August  2013   Deployment   81  08.18237  N   3900m   1  x  ADCP  300khz       4th  Sept  2015   Recovery   125  42.6732  E       4x  SBE37                       1xMMP                       15  x  SBE56  

M3e   31st  August  2013   Deployment   79  56.1358  N   1335m   1  x  ADCP  300khz       7th  Sept  2015   Recovery   142  14.8871  E       8x  SBE37                       15  x  SBE56                       1  x  ADCP  75kHz  

M5c   17th  September  2013   Deployment   82  30.9012  N   2503m   5  x  SBE37       NOT  DETECTED   NOT   89  59.5992  E       1  x  ADCP  300khz       27th/28th  Aug  2015   RECOVERED           1x  ADCP  75khz                       1  x  ISUS                       I  X  ODO/SBE37                       1  x  BPR                       15  x  SBE56  

M6b   14th  September  2013   Deployment   82  05.9846  N   2710m   4  x  SBE37       30th  August  2015   Recovery   97  01.8517  E       1  x  ADCP  300khz                       1  x  ADCP  75kHz                       1  x  ODO/SBE37                       1  x  ISUS                       1  x  ULS  

Seabird SBE56 thermistors were treated in a similar way, but set to a one-second sampling interval and, because memory capacity was not a limiting factor, were programmed for immediate start1. There was greater scope for scheduling calibration casts with the SBE56 instruments, as they are rated to a depth of 1500m and, given their rapid equilibration time and sampling rate, could be run on a normal CTD bottle stop schedule as cast. For SBE56 instruments, a deployment frame capable of securely accommodating fifteen thermistors at a time was available, which could be clamped directly to the CTD frame. Up to five SBE37 microcats were attached to the CTD frame on any individual cast by means of light line and several stout cable ties.

1Relative to the size of each data record these instruments have enormous memory capacity. At this sampling frequency and with the remaining memory these instruments could run for several months before exhausting storage capacity.

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Table I.6.3.3: Summary table of inter-calibration cast series

Date CTD Cast Number

Maximum depth (metres)

Stop depths (dbar) Instrument serial numbers

06 Sept. 2015

AT_028 col 100m 100, 75, 60, 40, 20 SBE37: 6282, 6309, 6279, 6278

07 Sept. 2015 AT_031 1000m As cast

SBE56: 2355, 2357, 2362, 2365, 2367, 2371, 2372, 2373, 2375, 2378, 2379, 2381

11 Sept. 2015 AT_052 1000m 1000, 789, 354,

126 SBE37: 2368, 6284, 10523, 10524

11 Sept. 2015 AT_049 860m As cast

SBE56: 2418, 2420, 2421, 2422, 2423, 2425, 2426, 2427, 2428, 2429, 2430, 2432, 2433, 2434, 2436

14 Sept 2015 AT_057 1000m 1003, 404, 323, 162

SBE37: 10522, 10525, 10527, 10528, 10529

15 Sept 2015 AT_062 1000m 1008, 809, 506, 385, 101 SBE37: 3049, 4703

16 Sept 2015 AT_071 100m 101, 40, 21 SBE37: 3380, 3441, 5183, 6158

23 Sept 2015 AT_078 1000m 1008, 306, 203, 121 SBE37: 4925, 5551, 5553, 6015

A normal CTD downcast would then be conducted, and the profile scrutinised for zones of vertical homogeneity in temperature. From these observations, two to four stopping depths, in addition to maximum cast depth, were defined to collect the inter-calibration measurement series, as conditions allowed. Instruments were held at maximum depth for ten minutes, to allow equilibration and for a minimum of five minutes at each stop depth after that. By using depth ranges within zones of vertical thermal homogeneity, any differences in temperature readings between the reference instrument and the test instruments ought to be attributable to differences in sensor output rather than vertical displacement on the frame, or frame movement up and down though the water column. As a result, sensible offsets can be established once compared to the original factory calibration series, as well as the output from the CTD sensors for each instrument. Differences in vertical displacement between instruments with pressure sensors (SBE37 series) and the reference pressure sensor (SBE 9/11+ Digiquartz® s/n 127217) were established to account for baseline differences in pressure sensor placement prior to incorporating into subsequent offset analysis or calibration coefficient derivation.

This series of measurements provides an important benchmark for the field data set in the absence of a full laboratory calibration of these instruments. Additionally, it provides data from which the initial calibration coefficients for the second deployment can be assessed and potentially derived, albeit over limited parameter ranges.

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I.6.3.2.2.3. Preliminary results (I. Polyakov, IARC; A. Pnyushkov, IARC)

The M6b mooring was deployed on the 14th of September, 2013 at 82°05.9846N and 97°01.8517E, water depth 2710 m. The M6b mooring consists of four Seabird SBE37s, two ADCPs, one ODO/SBE37, one ISUS, and one ULS. Instrument depths and setup parameters are summarized in Table I.6.3.2 and Figure A.II.8. The mooring was successfully recovered on August 30, 2015. In this preliminary analysis, we provide information for SBE37s, ADCPs, and ODO/SBE37 only. Data from ISUS and ULS were downloaded but it will take considerable time to process them and therefore they are not presented here.

This mooring provided two-year-long CTD records from four regular SBE37 microcats and one SBE37/ODO (Figure I.6.3.9). Unfortunately, the latter instrument provided only several months of record (yellow curve). There are some problems with several other instruments as well. SBE37 #4838 from ~220 m (blue) shows prolongated erroneous S spikes. T and C records from SBE37 #6280 (red) look highly correlated; however, S record shows values exceeding S from all other instruments, which look unrealistic and must be verified.

Figure I.6.3.9. Time series derived from SBE37 microcats and ODO/SBE37 deployed at NABOS M6b

mooring.

Current records are provided by two ADCPs for the upper 55-m layer and for the depth range of ~175-450 m (Figure I.6.3.10). The upward-looking 300-kHz ADCP was deployed at 50 m, covering a 0-50 m depth range with 2-m vertical resolution (Figure I.6.3.10, left). The top ~5 m of its hourly record is contaminated by noise. The upward-looking 75-kHz ADCP was deployed at 466 m, providing an hourly record with 5-m vertical resolution (Figure I.6.3.10, right); the first (deepest) level contains some noise. Interestingly, the record for the deeper layer shows a substantially increased current speed in the summer of 2014, similar to what was captured by ADCP in the upper ocean layer.

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Figure I.6.3.10. Depth vs. time diagram of current speed (cm/s) derived from ADCP #19063 (left) and ADCP #19033 (right), deployed at M6b mooring.

The M1-1a mooring was deployed on the 26th of August, 2013 at 77°04.2547N and 125°48.2878E, at water depth 250 m. The M1-1a mooring consists of three Seabird SBE37s and one ADCP (Table I.6.3.2 and Figure A.II.1). This mooring was recovered successfully on September 1, 2015.

CTD records from SBE37 (Fig. I.6.3.11) clearly show seasonal signals in temperature (T) that are not as clear in salinity (S) records. Deeper instruments have higher T and S. T and S from all instruments are highly correlated, attesting to the good quality of the records.

Figure I.6.3.11. Time series derived from SBE37 microcats deployed at the NABOS M1-1a mooring.

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ADCP #19143 provided a full two-year record covering the depth range from the surface to the bottom (Fig. I.6.3.12); note, however, that the record from the very top 20-25 m layer experiences problem from a high level of noise. The current speed is higher (>25 cm/s) in winter and lower (5-10 cm/s) in summer. There are numerous eddy-like events throughout the record.

Figure I.6.3.12. Depth vs. time diagram of current speed (cm/s) derived from ADCP #19143 deployed at M1-1a

mooring.

The M1-2a mooring was deployed on the 26th of August, 2013 at 77°10.3761N and 125°47.5155E, at water depth 787 m. The M1-2a mooring consists of one Seabird SBE37, one ADCP, and an MMP (Table I.6.3.2 and Figure A.II.2). This mooring was recovered successfully on September 1, 2015.

Figure I.6.3.13 shows two-year long SBE37 records of T, S, conductivity (C), and pressure (P). There is an apparent upward trend in R, C, and S records. P records demostrate several ~10-15 m spikes, which may be associated with the tilting of the mooring by surface currents due to winds.

Figure I.6.3.13. Time series derived from SBE37 microcat deployed at NABOS M1-2a mooring.

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The MMP profiler performed for an almost two-year-long period. T and S recorded during this period of time are presented in Figure I.6.3.14. Records show the MMP experienced problems at the beginning of the period, though fortunately the MMP resumed its normal work, providing full casts starting in 2014. The T and S records show strong variability at time scales resolved by the records. For example, two T maxima visible in Figure I.6.3.14 are probably due to the seasonal cycle.

Figure I.6.3.14. Time-depth sections of (left) temperature (°C) and (right) salinity, derived from MMP deployed at M1-2a mooring.

Vertical profiles of MMP current speed are shown in Figure I.6.3.15. These profiles show a strong winter enhancement of current, with a maximum of ~20 cm/s in the upper part of the profile and at ~400-500 m.

Figure I.6.3.15. Time-depth section of current speed (cm/s) derived from MMP #11494, deployed at M1-2a mooring.

ADCP #19035 provided a full two-year record covering the depth range from the surface to ~48 m (Fig. I.6.3.16); note, however, that the record from the very top 5-m layer experiences problem due to a high level of noise. The current speed is higher (>20 cm/s) in fall-winter and lower (5-10 cm/s) in summer. MMP and ADCP current speed records complement each other nicely, attesting to good quality of the records. Comparison of ADCP and MMP current speed records from the nearsest depth levels (60 and 78 m, respectively) demonstrated high (R ~ 0.74) correlation.

Figure I.6.3.16. Time-depth section of current speed (cm/s), derived from ADCP #19035 deployed at mooring M1-2a.

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The M1-3a mooring was deployed on the 6th of September, 2013 at 77°39.286N and 125°48.4014E, water depth 1849m. The M1-3a mooring consists of one Seabird SBE37, one ADCP and an MMP (Table I.6.3.2 and Figure A.II.3). The mooring was successfully recovered on September 2, 2015.

Figure I.6.3.17 shows two-year long SBE37 records for T, S, C, and P. As in T records from mooring M1-2a, there are apparent upward trends in R, C, and S records since the beginning of 2014. The P record denostrates several spikes, though they are much weaker—up to 3-4 m—compared with the 10-15 m spikes from mooring M1-2a. We also note a strong decrease in both T and S at the end of 2013, and gradual recovery after that.

Figure I.6.3.17. Time series derived from SBE37 microcat deployed at NABOS M1-3a mooring.

The same signal is clearly seen in T and S MMP records (Fig. I.6.3.18), attesting that this strong change is not due to errors in data (however, this signal is not evident in the MMP current record, Fig. I.6.3.19).

Figure I.6.3.18. Time-depth sections of (left) temperature (°C) and (right) salinity, derived from MMP #12215 deployed at M1-3a mooring.

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Additional confirmation that this feature of the MMP records is not an error comes from comparision of the first and last MMP T profiles, with CTD casts made immediately after the mooring deployment and recovery (Fig. 6.6.3.20), showing close fit between MMP and CTD profiles. The T and S MMP record shows a strong seasonal signal. In contrast with the M1-2a mooring, current speed documented at the M1-3a mooring site is not dominated by the seasonal signal (compare Figs. I.6.3.15 and I.6.3.19). Overall, current speed at M1-3a mooring is much weaker than at M1-2a mooring site, with typical values of 2-4 cm/s, disrupted by eddy-like events with current speed at 6-8 cm/s and even higher.

Figure I.6.3.19. Time-depth section of current speed (cm/s) derived from MMP #12215 deployed at M1-3a mooring.

Figure I.6.3.20. Comparison of the first and last T profiles derived from MMP #12215 from M1-3a mooring and CTD casts made right after deployment and recovery of the M1-3a mooring. Their close fit attests that the apparently anomalous T and S data evident in the MMP M1-3a record (Fig. I.6.3.15) are not due to malfunction of the MMP.

Currents at the upper ocean layer were monitored by ADCP #11292 (Fig. 6.3.21). The record demonstrates a strong increase of currents (up to 20 cm/s and stronger) in ice-free seasons. Comparison of ADCP and MMP current velocity components from the nearsest depth levels (54 and 78 m, correspondingly) demonstrated high (R ~ 0.8) correlations.

Figure I.6.3.21. Time-depth section of current speed (cm/s) derived from ADCP #11292 deployed at M1-3a mooring.

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The M1-4a mooring was deployed on the 8th of September, 2013 at 78°27.5431N and 125°53.7583E, at water depth 2721 m. The M1-4a mooring consists of four Seabird SBE37s, one ODO/SBE37, two ADCPs, one ULS, one ISUS and one BPR (Table I.6.3.2 and Figure A.II.4). The mooring was successfully recovered on September 3, 2015.

This mooring provided two-year-long CTD records from four regular SBE37 microcats and one SBE37/ODO (Figure I.6.3.22). The records are mostly clean, and without obvious errors; however, SBE37 #6015 from ~250 m (purple) shows a prolongated erroneous S spike in June 2016. The T record from SBE37 #10530 from ~120 m (blue) shows the strongest variability.

Current records are provided by two ADCPs for the upper 55-m layer and for the depth range ~175-450 m (Figures I.6.3.23-25). The upward-looking ADCP 300 kHz was deployed at 56 m, covering a 0-55 m depth range with 2-m vertical resolution (Figure I.6.3.23, left). The top ~5 m of its hourly record is contaminated by noise. The upward-looking 75-kHz ADCP was deployed at 463 m, providing an hourly record with 5-m vertical resolution (Figure I.6.3.23, right). Even though the instrument was new, it experienced problems switching from normal four-beam operation to three-beam operation after ~800 hours. This resulted in extremely noisy records (see figure). Tidal analysis applied to raw current records failed (results are not shown), and we believe that high-frequency (including tidal) variability is not recoverable from the record. However, we found that lower-frequency variability is recoverable. Figure I.6.3.24 compares time series from 55-m depth provided by ADCP 300 kHz and from 175 m provided by 75-kHz ADCP. This figure demonstrates that a two-day running mean filtering eliminates noise effectively from the 75-kHz ADCP record, so that means and standard deviations derived from the records provided by two different instruments become well correlated. Figure I.6.3.25 shows 75-kHz ADCP current speed after filtering out high-frequency noise; the first (deepest) level still contains noise.

Figure I.6.3.22. Time series derived from SBE37 microcats deployed at NABOS M1-4a mooring.

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Figure I.6.3.23. Depth vs. time diagram of current speed (cm/s) derived from ADCP #11240 (left) and ADCP #19062 (right), deployed at M1-4a mooring.

Figure I.6.3.24. (Top and middle) Time series of standard deviations (SD, cm/s) calculated within running one-month long window for (top) U-component and (middle) V-component of current record made by ADCP 75 kHz at 175 m (blue curves). Two-day running mean filtering was applied to eliminate high-frequency noise. For comparison, red time series show SDs derived from raw record from the nearest 55-m depth level from ADCP 300 kHz. (Bottom) Time series of hourly (dotted lines) and monthly (solid lines) current speed (cm/s), derived from ADCP 75 kHz (blue) and ADCP 300 kHz (red) records.

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Figure I.6.3.25. Depth vs. time diagram of current speed (cm/s) derived from ADCP #11240 300 kHz (top) and ADCP #19062 75 kHz (bottom), deployed at M1-4a mooring. ADCP 75 kHz record was cleaned of high-frequency noise using a two-day running mean filter.

Time series of bottom pressure P, accompanied by the temperature record, is shown in Figure I.6.3.26. There is a downward P trend before approximately 2014.1; however, the rest of the record does not show any obvious trend, so there are some physical reasons for downsloping in the earlier part of the record. The high-frequency component of the record is dominated by tides, with clear fortnightly envelopes formed by tidal constituents.

Figure I.6.3.26. Time series of temperature (upper panel) and bottom pressure (lower panel) from BPR #0083 deployed at M1-4a mooring.

The M1-5a mooring was deployed on the 28th of August, 2013 at 80°00.1986N and 125°59.6729E, at water depth 3443 m. The M1-5a mooring consists of one Seabird SBE37, one ADCP, and one MMP

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(Table I.6.3.2 and Figure A.II.5a). Above major flotation, the mooring also included a thermistor chain (Figure A.II.5b). This mooring was successfully recovered on September 3, 2015. However, the upper part of the chain, including one SBE37 and ten SBE56 thermistors, was lost during mooring recovery, and only two SBE37 and five thermistors were successfully recovered.

Temperature records from the thermistor chain is shown in Figure I. 6.3.27. An interesting feature of this record is pulses of warmth at the bottom of the upper 70m layer which may be probably interepreted as influx orf AW heat to the upper ocean (but this hypothesis needs further verification).

Figure I.6.3.27. Time-depth diagram of water temperature derived from the upper ocean thermistor array deployed at NABOS M1-5a mooring.

T, C, S, and P records from all three recovered SBE37s are shown in Figure I.6.3.28. Except some minor S spikes evident in the shallowest (#10524, red) instrument record, all time series appear clean and well correlated, showing similar variability in all records. However, P records suggest something happened with the mooring between approximately 2014.4 and 2014.55, with deepening of all instruments at the beginning and end of the period by ~20 m, and rough behavior in between.

Figure I.6.3.28. Time series derived from SBE37 microcats deployed at NABOS M1-5a mooring.

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Anomalous behavior of the mooring over this period of time is also evident in the MMP record (Figure I.6.3.29). Throughout the water column, to the depth of ~750 m, MMP T and S records demonstrate strong anomalies. Particularly striking is the MMP current speed record, with a strong maximum in the deeper layers (Figure I.6.3.30). We have checked the quality of data and found no reason to think the data are erroneous. The only plausible explanation for this anomaly is a remarkable baroclinic eddy that passed the mooring location during this period of time.

Figure I.6.3.29. Time-depth sections of (left) temperature (°C) and (right) salinity derived from MMP # 12040 deployed at M1-5a mooring.

Unfortunately, ADCP provided just one year-long current record (Figure I.6.3.30, right). The record shows anomalously high currents at the beginning of the record (which are not evident in the MMP current record, same figure, left panel) and a trace of downward propagation in signal in winter months. Over the overlapping one-year-long portions of the MMP and ADCP records, two current speed time series taken from the nearest depth levels (88 m from MMP and 80 m from ADCP) are correlated at R = 0.66 (not shown).

Figure I.6.3.30. Depth vs. time diagram of current speed (cm/s) derived from MMP #12040 (left) and ADCP #19100 (right) deployed at the M1-5a mooring.

The M1-6a mooring was deployed on the 29th of August, 2013 at 81°08.1824N and 125°42.6732E, at water depth 3900 m. This M1-6a mooring consists of one Seabird SBE37, one ADCP, and one MMP (Table I.6.3.2 and Figure A.II.6a). Above major flotation, the mooring also had a thermistor chain, including seven thermistors and two SBE37 (Fig. A.II.6b).

The mooring was successfully recovered on September 4, 2015.

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Temperature records from the thermistor array are shown in Figure I.6.3.31. There is a clear seasonal cycle, with ventilation of the layer driven by brine rejection during ice formation in winter and warming in summer.

Figure I.6.3.31. Time-depth sections of temperature (°C) derived from upper ocen thermistor chain at M1-6a mooring.

T, C, S, and P records from all three recovered SBE37s are shown in Figure I.6.3.32. Except some minor S spikes evident in the shallowest (#10524, red) instrument record, all time series appear clean and well correlated.

Figure I.6.3.32. Time series derived from SBE37 microcats deployed at NABOS M1-6a mooring.

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The MMP record shows a gradual increase of T and S in time with little variability, which is expected considering the depth of the mooring (Figure I.6.3.33). Current speed from the MMP (Figure I.6.3.34, left) has a two-layer structure, with a lot of noise-like signals in the upper (~75-150 m) part, and a much smoother deeper portion of the record. Intensification of currents in summer 2014 is in phase with changes in the upper mixed layer documented by ADCP (Figure I.6.3.34, right). MMP and ADCP records from nearby depth levels (64 m and 52 m, respectively) are correlated at R = 0.55.

Figure I.6.3.33. Time-depth sections of (left) temperature (°C) and (right) salinity derived from MMP # 12047 deployed at M1-6a mooring.

Figure I.6.3.34. Depth vs. time diagram of current speed (cm/s) derived from MMP #12047 (left) and ADCP #11292 (right) deployed at M1-6a mooring.

The M3e mooring was deployed on the 31st of August, 2013 at 79°56.1358N and 142°14.8871E, with water depth 1335 m. The M3e mooring consists of five Seabird SBE37s and two ADCPs (Table I.6.3.2 and Figure A.II.7a). Above major flotation, the mooring also had a thermistor chain, which included three SBE37 and fifteen SBE56 thermistors (Fig. A.II.7b). This mooring was successfully recovered on September 7, 2015; however, the very top buoy of the thermostor array was lost, and the upper segment hung down, duplicating records made by the middle segment of the chain. Further analysis includes only the two lower segments of the chain.

Temperature records from the thermistor array show a clear seasonal cycle, with ventilation of the layer driven by brine rejection during ice formation in winter and warming in summer (Figure I.6.3.35). Particularly striking is the very high temperatures, of up to 2 °C, recorded in summer 2014.

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Figure I.6.3.35. Time-depth sections of temperature (°C), derived from upper-ocen thermistor chain at M3e mooring.

T, C, S, and P records from six recovered SBE37s are shown in Figure I.6.3.36. Despite some minor S spikes evident in the records, all time series overall appear clean. Records from the upper ocean (SBE37 #10523, 10527, and 10529) appear well correlated.

Figure I.6.3.36. Time series derived from SBE37 microcats deployed at NABOS M3e mooring.

Current speed records are provided by two ADCPs for the upper 50 m layer and for the depth range ~175-450 m (Figure I.6.3.37). The top ~5 m of the shallower ADCP record is strongly contaminated by noise; the rest of the record is dominated by seasonal signals, with much stronger (up to 30 cm/s) current speed

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in summer. The deeper ADCP record is clean, with several periods of increased currents. Unlike mooring M6b and M1-4a ADCP records, the lower ADCP does not show any increase in current speed in summer.

Figure I.6.3.37. Depth vs. time diagram of current speed (cm/s), derived from ADCP #11187 (left) and ADCP #18918 (right) deployed at M3e mooring.

I.6.3.2.3. Mooring deployments

The total number of moorings deployed during the NABOS 2015 cruise was thirteen. Six of them belong to IARC; these form a five mooring cross-slope section along ~125°E, with an additional single mooring M3 (Figure I.6.3.38). Six others belong to AWI, forming the core for the mooring section at ~95°E. The additional mooring AK6/M6c, combining instruments from AWI and IARC, is also a part of the this mooring cross-slope section.

Figure I.6.3.38. Map showing positions of moorings deployed during 2015 NABOIS cruise.

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I.6.3.2.3.1. Logs of central-eastern Laptev Sea mooring deployments (I. Waddington)

Mooring M1-1b. 18 September 2015. The ship arrived at the site of mooring M1-1b and faced into the wind. Deploy commenced at 1840 h, anchor first from the winch. Deployment went well, with the final lift of the steel sphere and ELCAT beacon carried out from the lower deck to enable lift height. Water depth was monitored continually from the ship's echo sounder repeater positioned in the Mooring Operations Container on the heli deck. The mooring was let go from the ship using an Ixsea acoustic release positioned in line above the subsurface sphere and commanded from the portable AWI deck unit on the lower deck. On completion of deployment at 1929 h, a mooring acoustic triangulation was carried out to determine accurate mooring position. With the survey completed, the ship went to the newly navigated position and checked depth and acoustic range. With position now established, all underwater acoustic units were disabled.

Mooring M1-2b. 18 September 2015. Deployment procedures were carried out as with mooring M1-1b. Deployment went well, commencing at 2143 h and completion at 2310 h. The Upper Ocean Array was attached from the lower deck, and with the ship moving some way on, was then streamed out astern with the subsurface steel buoy just at the sea surface. The mooring was let go, as M1-1b with the Ixsea system and the mooring and Upper Ocean Array observed to sink clear of the ship, and well streamed out at 2312 h. An acoustic navigation triangulation was carried out and accurate position determined.

Mooring M1-3b. 19 September 2015. This was the first MMP (McLane Moored Profiler) mooring to be deployed on this cruise, and required the use of both Hawboldt capstan and winch systems. Deployment was anchor first and began at 0518 h, with no problems deploying Aramid lines from the Hawboldt. On transfer from the Hawboldt to the winch and pay out of profiling wire, it was clear the winch load nearly reached its maximum, with the winch stalling under heave. The profiling wire had several areas of jacket damage as the wire “knifed” into the underlying wire turns. Repairs were made to the wire coating using Scotch Cote and PVC tape 470—in the past, this has had no adverse effects on profiling. Deployment went well otherwise, and the mooring was let go from the ship at 0745 h. An acoustic navigation triangulation was carried out, and accurate position determined, though acoustic reception was not good and the threshold of the Edgetech deck unit had to be reduced from the normal 2.5 to 1.9. On completion, the ship positioned close to the navigated position, with acoustic reception limited and the acoustic transducer drifting away from ship and often under ship. The wind had increased and the ship could not hold its position. On completion the acoustic units were all disabled.

Mooring M1-4b. 20 September 2015. This mooring was deployed anchor first from the Hawboldt Capstan, as all mooring line was Aramid and prewound onto a single wooden drum housed on the Reel-o-matic Tensioning machine. Deployment went well, carried out in snow squalls and a gusting wind, which made overside line angles at times difficult to work with. The mooring deploy commenced at 0407 h, with the mooring let go at 0645 h. Acoustic navigation was carried out with some difficulty, ranging on the ELCAT giving good reception at all positions. Releaser reception was poor and infrequent. When the ship was positioned directly over the mooring, the navigated position of both releasers could be interrogated. On completion all acoustics were disabled.

Mooring M1-5b. 21 September. The ship arrived on position in the early hours of the morning and was slow steaming into a swell sea and 20 kts wind, making 4kts. By 0320 h, with the wind decreasing and barometer rising, the ship required 4 kts ahead to hold position and course. Mooring deploy was delayed for an improvement in conditions. Weather having improved, deployment commenced at 0638 h. The BPR (Bottom Pressure Recorder) anchor assembly, with releasers and glass spheres, was deployed from the lower deck using the Hawboldt Capstan. Transfer from the Aramid mooring line to the MMP wire on the winch was made easily, and the MMP was deployed overside on the bottom bumper without mishap. The deployment of the mooring wire from the winch was difficult, however, as the line length overside increased, which in turn meant an increase in load on the winch. The wire knifed in several times, and repairs had to be made to the jacket wire. The winch cut out several times as the load maximum was

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reached with ship pitch and roll. On deploy of the steel spheres, the winch could not lift the steel buoys, and the lift had to be transferred to the Hawboldt capstan to lift the buoys overside. At this point, it was evident that a further 100 m of line would be required to position the ADCP and Upper Ocean Array at correct depth. The steel buoys and ADCP were hauled back onboard, and a length of 100 m of Dyneema line inserted. Deploy to the Upper Ocean Array then continued, with the array being attached to the steel buoys on the lower deck. Several attempts to stream the array were made as the steel buoy rotated in the propeller wash, winding up the array line. With the array observed successfully streamed, the mooring was let go. An acoustic navigation was carried out using five points for positioning, as it appeared the mooring was still settling and coming upright. With the first two positions giving a poor fix, three more points were occupied. With an accurate position obtained, the ship then repositioned over the new navigated position and acoustics were checked. The ELCAT responded well, but the acoustic releasers were erratic and reception was poor. Moving the ship approximately 500 m to one side, acoustic releaser reception was greatly improved, indicating probable shadowing of the releasers by the four glass spheres close above.

The acoustics having been checked were then all disabled.

Mooring M3f. 7 September 2015. This mooring deployment commenced in good weather conditions with open water. Deployment was from the Hawboldt Capstan and commenced at 1615 h. With all moorings deployed and the steel buoys overside, a tow was undertaken to position at the correct depth. On reaching the required depth, the ship was slowed, and the Upper Ocean Array deployed from the lower deck. The Array was observed to be streaming correctly, and with a “kick ahead” on the ship's propellers, the steel buoys were lowered underwater and the Ixsea release commanded to let go of the mooring. The mooring was observed to sink away well clear of the ship, with the Upper Ocean Array streaming above it as it descended at 1850 h. An acoustic navigation was then performed, with an accurate position established and good acoustics to ELCAT and releasers. On completion of the navigation, the ship positioned at the established position and interrogation of the CAT established a horizontal range of 100 meters. All acoustics were then disabled.

I.6.3.2.3.2. Notes of Cape Arkticheskiy mooring deployments (T. Kanzow)

A total of seven moorings were deployed along a line across the continental slope of the Severnaya Zemlya Archipelago north of Cape Arkticheskiy near 95°E. The water depths at the deployment sites increase from 304 m at the shelf edge (AK1) to 3019 m at the base of the continental slope (AK7). All moorings were deployed with the anchors first.

The four shallowest moorings (AK1, AK3, AK3, AK4) were deployed August 28-30. The three deeper moorings (AK5, AK6, A7) were deployed September 23-24. AK1 and AK2 were deployed in open water. AK3 and AK4 were deployed in loose sea ice, which made it difficult for the vessel to hold (or drift to) the pre-defined deployment position. AK5, AK6, and AK7 were deployed on consolidated sea ice. Here, the starting points for the mooring deployment operations were defined from drift tests, with the vessel subsequently drifting with the sea ice toward target deployment locations. The deployments of AK5 and particularly AK6 were accompanied by strong, variable winds, which made the drift speed & direction change relative to those obtained from the drift test. An acoustic triangulation for accurate determination of the positions was performed for moorings AK5, AK6, and AK7.

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Table I.6.3.3: Summary of central-eastern Laptev Sea deep-water moorings deployments in 2015.

M00RING   Date/s   Operation   Lat./Long.   Depth   Instruments  

M1-­‐1b   18th  Sept  2015   Deployment   77  4.221N   252m   3  x  SBE37  

            125  49.577E       1  x  ADCP  75kHz  

M1-­‐2b   18th  Sept  2015   Deployment   77  10.373  N   783m   6x  SBE37  

            125  47.974E  E       1  x  ADCP  300khz                       1  x  ADCP75khz  

                    1x  ISUS                       1  x  ODO/SBE37  

                    1x  Therm  Array  

M1-­‐3b   19th  Sept  2015     Deployment   77  39.234  N   1866m   1  x  SBE37  

            125  48.686  E       1  x  ADCP  300khz                       1  x  MMP  

M1-­‐4b   20th  Sept  2015     Deployment   78  28.084  N   2700m   4  SBE37               125  57.679  E       1  x  ULS  

                    1  x  ISUS                       1  x  ODO/SBE37  

                    1  x  ADCP  300khz                       1  x  ADCP  75kHz  

M1-­‐5b   21st  Sept  2015     Deployment   79  59.1941N   3443m   1  x  ADCP  300khz  

            126  01.2282E       3x  SBE37                       1xMMP  

                   

1  x  Therm  Array  1x  BPR  

        Deployment   79  56.1941N   1357m   1  x  ADCP  300khz  

M3f   7th  Sept  2015         142  15.216E       6  x  SBE37                       1  x  ADCP75khz  

                    1  x  Therm  Array  

The moorings were designed to carry CTD sensors (SBE-37) on standard depths of 135 m, 210 m, 300 m, 600 m, 1300 m and at the sea floor. AK1, AK3, and AK4 also had CTD sensors near 50 m. Actual sensor depths deviate slightly from the designed ones, as a result of the inability to deploy moorings right at the pre-defined positions (see comments above). Moorings AK2 and AK3 used a combination of a 150 KHz (Quartermaster) and 75 KHz ADCP, to measure the velocity profile in the upper 500 m of the water column. AK1 uses a 150-KHz ADCP. AK4 and AK5 rely on a combination of a 300-KHz (Workhorse) and 75-KHz (Longranger) ADCP to measure the velocity profile in the upper 400 m of the water column. In all cases, 150-KHz and 300-KHz devices look upward and are equipped with bottom track capability. This way, sea-ice movement can be monitored. The latter will be used as a constraint for the ADCP-inferred water current directions, which are subject to large uncertainties in the high Arctic. In addition, point current meters (Aanderaa RCM 7 and 8, and RCM11) were used near the sea floor and—where applicable—at 700 and 1300 m, and on the inshore moorings AK1–AK5.

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Table I.6.3.4: Summary of central-eastern Laptev Sea deep-water moorings deployments in 2015.

Mooring Lat / N

Anchor drop

Lon / E

Anchor drop

Depth [m] Sound

Speed

Date Time

AK 1 81° 50.69’ 094° 20.53’ 304 1465 28/08/15 19:47

AK 2 81° 54.17’ 094° 28.92’ 898 1465 29/08/15 00:46

AK 3 81° 57.73’ 094° 32.60’ 1453 1465 29/08/15 08:28

AK 4 82° 06.28’ 094° 46.34’ 1985 1465 30/08/15 03:46

AK 5 82° 13.46’ 094° 50.77’ 2398 1465 23/09/15 17:15

AK 6 82° 22.03’ 095° 13.06’ 2794 1465 24/09/15 00:32

AK 7 82° 35.10’ 095° 30.00’ 3019 1465 24/09/15 19:43

For AK6 and AK7 no Longranger ADCP devices were available. AK6 was initially supposed to incorporate the Longranger recovered from the NABOS M1-4 site (from the 126°E line). This instrument unfortunately had not worked properly (malfunction of Beam 3), and was therefore not available for deployment. At both moorings RCM 8 and 11, current meters are used near 200, 300, 450, and 700 m to obtain water column profiles of ocean currents. On AK6 and AK7, a Workhorse ADCP (with bottom track capability) and an RCM7 are used near 100 m, respectively.

Moorings AK1, AK3, AK5, and AK7 are also equipped with bottom pressure recorders (SBE-26 BPRs), in order to compute horizontally-integrated ocean transports. BPRs were attached to the dual-release packages using magnesium bolts. The latter should dissolve in seawater, so that the BPRs drop to the sea floor soon after the deployment. The BPRs remain connected to the releases by wires, so that they can be recovered jointly with the moorings.

AK3 and AK6 also include ISUS nitrate sensors, the former at 50 m and 125 m, the latter at 125 m. AK6 incorporates both AWI and NABOS instrumentation and hardware.

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I.6.3.3. Lagrangian drifters (V. Ivanov, AARI)

Several Lagrangian drifters were deployed during the NABOS-2015 cruise, including three ITP buoys, two O-buoys, one Seasonal Ice Mass Balance (SIMB) buoy, one Autonomous Ocean Flux Buoy (AOFB), and twelve meteorological buoys. Locations of ITP deployments are presented in Table I.6.3.5 and Figure I.6.3.37. One O-buoy was deployed together with the first ITP #91. The second O-buoy and all other buoys (except meteorological ones) were deployed along with the second ITP #92. Meteorological buoys were deployed en route, outside the Russian EEZ (see Table I.6.3.6). The first two ITPs were deployed during ice stations, both on ~1 m thick ice floes. Since the search for an appropriate ice floe for deployment of the third ITP at ~ 175°E and 80°N was unsuccessful, this third ITP #90 was deployed in open water. Confirmation was received from WHOI that all three ITPs started up fine and reported profiles back. However, the in-water ITP #90 stopped reporting after a few days.

Table I.6.3.5: Initial position of ITP buoys deployed in 2015.

ITP ID# Launch date/time Longitude Latitude

91   2015/09/05 10:45 GMT   124o30.9'E   82o44.5'N  

92   2015/09/12 23:30 GMT   166o28.8'E   80o43.2'N  

90   2015/09/21 16:10 GMT   125o9.3'E   79o58.3'N  

Table I.6.3.6: Initial position of meteorological buoys deployed in 2015.

Buoy type Time, Date Latitude Longitude Producer Comment

IMEI  #300234062856890   07:49  UTC  Sep3   79  27,505N   125  49,898E   Met  Ocean    

IMEI  #300234062956120   06:16  UTC  Sep  4   80  55,190N   125  46,670E   Met  Ocean    

IMEI  #300234062852920   07:27  UTC  Sep  5   82  45,506N   124  23,426E   Met  Ocean   ice  station  

IMEI  #300234062850900   06:48  UTC  Sep  6   81  19,243N   136  30,192E   Met  Ocean    

IMEI  #300234062854890   22:24  UTC  Sep  11   79  18,347N   168  00,273E   Met  Ocean    

IMEI  #300234062855110   17:20  UTC  Sep  12   80  40,134N   166  25,790E   Met  Ocean   ice  station  

IMEI  #300234062853910   07:47  UTC  Sep  13   80  27,850N   171  20,570E   Met  Ocean    

IMEI  #300234062959450   20:33  UTC  Sep  13   79  59,715N   178  00,269E   Met  Ocean    

ARGO#135388   09:00  UTC  Sep  14   79  09,219N   175  50,870E   Argo    

ARGO#135389   07:40  UTC  Sep  15   77  59,403N   173  12,883E   Argo   did  not  respond  

ARGO#135385   07:36  UTC  Sep  20   78  27,263N   125  59,709E   Argo    

ARGO#135387   13:10UTC  Sep  21   80  00,170N   126  00,165E   Argo    

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Figure I.6.3.37. Map showing positions of ITP buoys deployed during 2015 NABOIS cruise.

Figure I.6.3.38. Deployment of (left) ITP buoy and (right) O-buoy during 2015 NABOIS cruise.

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I.6.4. HYDROCHIMICAL OBSERVATIONS (M. Alkire, APL/UW)

I.6.4.1. Background and purpose

The main objectives of the Eurasian and Makarov Basins (EMB) observational network include improved understanding of ongoing changes in (1) along-slope transport of AW by boundary currents; (2) interaction and mixing between AW branches and shelf waters, the interior of the deep basins, and the upper ocean; and (3) upper ocean circulation of the EMB. The primary role of the hydrochemistry program concerns the second research target—specifically, the formation of different types of halocline water in the eastern Arctic and their subsequent modification through mixing. Mixing between Atlantic and Siberian shelf waters is of great concern for the formation of halocline waters that separate overlying sea ice cover from the heat stored in the core of the Atlantic layer (Steele and Boyd, 1998). Different mechanisms have been proposed for the formation of halocline waters, ranging from densification of shelf waters via brine release during sea ice formation (Aagaard et al., 1981; Steele et al., 1995) to the freshening and cooling of Atlantic waters through melting sea ice (Rudels et al., 1996; Steele and Boyd, 1998). These mechanisms produce separate branches of halocline water with different physical and chemical characteristics. As such, geochemical tracers can be used as tools for distinguishing between formation processes of halocline waters and their potential origins. However, mixing and modification of halocline water during circulation along the Siberian slope may convolute these different signatures, making the distinction and study of formation and modification processes difficult. Extensive measurements collected during 2013 and 2015 NABOS cruises provide detailed geochemical measurements for halocline and Atlantic layers. This focused sampling effort allows for the detection of small changes and/or transitions between layers that point towards differences in formation mechanisms (upstream) versus mixing and/or modification along the spreading pathway (downstream).

I.6.4.2. Personnel

Personnel were split into two teams of four to work twelve-hour shifts during the day (08:00 to 20:00) or night (20:00 to 08:00).

Table I.6.4.1: Timetable of hydrochemistry team shifts during 2015 NABOS cruise

Name Institution Shift Matthew Alkire APL/UW Day, shift leader Nadya Torgunova VNIRO Night Theresa Hargesheimer AWI Day Ho Won Lee PNU Day Natalia Markova AARI Night Dan Naber IMS/UAF Night, shift leader Ahn So Hyun PNU Day Dean Stockwell IMS/UAF Day & Night as needed Laura Wischnewski AWI Night

I.6.4.3. Instruments and equipment

The sensor suite utilized during this cruise included a Seabird SBE9plus CTD (conductivity-temperature-depth tool), equipped with dual temperature (SBE3) and conductivity (SBE4) sensors; a SBE5T submersible pump; and a digi-quartz pressure sensor. Additional biogeochemical sensors mounted to the rosette included dual Seabird SBE43 dissolved oxygen sensors, a WET Labs ECO-FLNTU chlorophyll and turbidity sensor, a WET Labs C-Star transmissometer (beam transmission and attenuation), a photosynthetically-active radiation (PAR) sensor (Biospherical model QCP2350), and a Satlantic Deep Submersible Ultraviolet Nitrate Analyzer (SUNA). A Benthos PSA-916 altimeter was also mounted to

54

the bottom of the rosette to avoid contact with the carousel on the seafloor. Finally, twenty-four Niskin bottles (10 L capacity) were included for the collection of water samples at specified depths.

I.6.4.4. Standard operations

A total of ninety-four hydrographic stations were occupied during the 2015 NABOS cruise. At all but six of these stations, water samples were collected for a variety of chemical and biological measurements. Metadata describing the locations, dates, times (GMT), and depths of these stations have been made available with this report (2015 Stations.xlsx). During each cast, the rosette was moved from the hydrology room to the port side deck using a hydraulic crane. The rosette was then transferred to a winch and lowered over the port side of the vessel to a depth of ~15 m for initialization and sensor equilibration. The rosette was then brought up to the surface (0-2 m) and lowered back through the water column at a relatively constant rate, to a depth of either ~1000 m or between 5 and 10 m above the bottom (most casts were to ~1000 m, as some instruments cannot withstand pressures exceeding 1000 db). Once maximum depth was reached, the rosette was stopped and a Niskin bottle was fired to obtain a water sample. The rosette was then brought back up through the water column and routinely stopped at depths of 500, 250, 200, 150, 140, 130, 120, 110, 90, 80, 70, 60, 50, 40, 30, 20, 10, and 2-4 m (surface) for the collection of water samples (alternate or additional depths were tripped on a cast-by-cast basis). The rosette was stopped for a period of ~30 seconds before sample collection to allow bottles to soak, and to minimize turbulent flows caused by the carousel’s wake as it moved upward through the water column. Once the rosette reached the surface, it was brought back on deck and transferred inside the hydrology lab using the crane. All sensor-based data acquired from the CTD and additional instrumentation on the rosette that correspond directly to the times and depths of seawater sample collections have been made available with this report (ctd bottle values.xlsx). Optical instruments were typically rinsed with distilled water immediately after the rosette was brought back into the hydrology lab.

Once rinsing was complete, Niskin bottles were immediately sampled. Gases (dissolved oxygen, dissolved inorganic carbon) were sampled from bottles first to minimize atmospheric contamination. Once sampling for gases was completed, the chemistry team sampled all other Niskin bottles for remaining chemical parameters. This was completed by preloading a series of twenty-four buckets (each corresponding to a Niskin bottle on the rosette) with the appropriate bottles necessary for collection of the samples desired. Each bucket (and bottles therein) was labeled with a specific identification number, corresponding to the station and depth of the sample. Each member of the chemistry team on duty took a bucket to its associated Niskin bottle and filled the sample bottles in that bucket, taking care to fill smaller volume sample bottles first (e.g., nutrients, stable oxygen isotopes) and then moving on to larger volume bottles (e.g., POC, DNA). The completed bucket would then be returned, and the team member would move to another bucket and continue sampling. Once all buckets had been sampled, a log of collected samples was taken (scanned copies of log sheets made available with this report: CTD_Logsheets_NABOS15.pdf) for checking and record keeping. If all samples were appropriately filled, Niskins were emptied of any remaining seawater.

I.6.4.5. Sample collection

At all stations, samples were routinely collected for chlorophyll (0-50 m), stable oxygen isotopes (δ18O, full depth range), nutrients (full depth range), dissolved organic carbon (DOC, full depth range), and barium (full depth range). At alternating stations, samples were collected for either dissolved oxygen and salinity or dissolved inorganic carbon and total alkalinity (TA & DIC). Salinity and dissolved oxygen samples were collected primarily to assess the quality of factory calibrations of conductivity and O2 sensors, respectively, and to determine if there was any drift in sensor response during the cruise. Larger volume samples for particulate organic carbon (POC), HEME, DNA, and enzymes were collected at a smaller number of casts (approximately every third cast) to allow necessary time for filtering. Samples collected to estimate the rate of primary production (PP) were collected at ten different stations. The

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frequency of samples collected for PP was determined predominantly by local sunlight conditions. The majority of samples collected during the cruise will be shipped to various laboratories and analyzed over the next several months. Nutrient and DOC samples were frozen immediately after collection at -80 ºC and will be shipped back to facilities at IARC/UAF and AWI, respectively, for analysis. TA & DIC samples were preserved with saturated mercuric chloride and will be analyzed at IARC/UAF. Salinity and barium samples will also be shipped to IARC/UAF for analysis. Stable oxygen isotope samples will be shipped to laboratory facilities at Oregon State University for analysis. POC, HEME, and DNA samples were filtered on board the vessel and filters stored frozen for subsequent analysis at AWI. Samples for primary productivity and phytoplankton composition were similarly filtered; resulting samples will be shipped to laboratory facilities in Korea for subsequent analysis. Samples collected for enzymes and chlorophyll concentration were processed and analyzed during the cruise; however, final data sets require additional analysis and can be acquired by contacting Theresa Hargesheimer and Dean Stockwell, respectively. Preliminary comparisons between chlorophyll concentrations derived from seawater samples and those estimated from the WET Labs ECO FLNTU sensor indicate the sensor was properly calibrated and likely experienced little drift during the cruise. Additional analyses are required before any adjustments and/or corrections to calibration coefficients of the FLNTU are made. Samples of dissolved oxygen were processed during the cruise and are discussed in the next section.

I.6.4.6. Dissolved oxygen

O2 sensor precision was estimated to be ±0.04 mL L-1, determined from random duplicate samples (n = 4) collected over the cruise. These data were used in combination with salinity and temperature taken from bottle files logged by the CTD, to check the quality of the Seabird SBE43 oxygen sensor calibration and determine whether updates to the calibration coefficients were necessary. Figure I.6.4.1 shows comparison between the Winkler O2 data (normalized by phi, a parameter determined from the corresponding CTD salinity, temperature, and pressure, as well as applied calibration coefficients) and sensor voltages recorded by SBE43 sensors. Correlation coefficients for the linear regressions were excellent: R2 = 0.99518 and 0.99123 for sensors 1 and 2, respectively. Furthermore, available data suggested that sensor response was close to that expected from factory calibration (see Table 3) and did not drift significantly over the course of the cruise. All dissolved oxygen data, comparisons with CTD-derived concentrations, plots, and regressions have been made available with this report (NABOS_Winklers_2015.xls).

Figure I.6.4.1: Voltages from dissolved oxygen sensors versus “Winkler/phi,” a parameter that utilized dissolved oxygen concentrations determined via Winkler titration to check the accuracy of calibration coefficients of the two sensors. The slope and intercept of the linear regressions are used to derive updated calibration coefficients for the sensors (see Table I.6.4.3).

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Table I.6.4.2: Summary of water samples collected during the 2015 NABOS Cruise. δ18O: stable oxygen isotopes; TA & DIC: total alkalinity and dissolved inorganic carbon; Nutrients: phosphate,

nitrate, nitrite, ammonium, and silicic acid; DOC: dissolved organic carbon; POC: particulate organic carbon; PP: primary production & phytoplankton composition.

Variable Total number of samples collected

Institution Sample volume (mL)

Number of stations (sampling frequency)

Salinity 95 IARC/UAF 125 42

O2 121 APL/UW 125 47

δ18O 1400 APL/UW 20 84

TA & DIC 237 IARC/UAF 250 41

Barium 639 IARC/UAF 30 84

Nutrients 1277 IARC/UAF 30 88

Chlorophyll 564 IARC/UAF 1060 88

DOC 389 AWI 30 38

POC 256 AWI 4000 38

HEME 192 AWI 2000 38

DNA 304 AWI 6000 27

Enzymes 10 AWI 6000 5

PP 50 PNU 2000 10

DOC 443 VNIRO 50 55

Table I.6.4.3: Calibration coefficients (Soc & Voffset) for SBE43 oxygen sensors. Original coefficients were supplied by Seabird; new coefficients are derived from the data comparison

(Figure I.6.4.1).

Sensor 1 Sensor 2

New Soc 0.4728 0.3981

New Voffset -0.4101 -0.3858

Original Soc 0.4806 0.4119

Original Voffset -0.4754 -0.4990

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I.6.4.7. Preliminary Results

There are very few observations available for conducting preliminary analyses, as most chemical and biological samples collected during the cruise require further processing and analysis at home laboratory institutions. Nevertheless, we can begin to analyze data collected by the CTD and additional instruments mounted on the rosette. For example, a potential temperature-salinity diagram of CTD data from the five transects occupied during the cruise (Figure I.6.4.2, top) shows differences in the potential temperature of the lower halocline (33.5 < S < 34.5). The warmest halocline water was observed along the easternmost transects (165ºE and 175ºE) and appears to be associated with diapycnal mixing between Atlantic waters and colder shelf and/or slope waters. Concentrations of dissolved oxygen were quite low in this layer (Figure I.6.4.2, bottom), likely indicative of influence from bottom sediments. Thus, the upwelled Atlantic water either came into contact with shelf and/or slope sediments with a high biological oxygen demand or mixed with O2-poor, bottom shelf waters.

I.6.4.8. Data availability

All data collected during the cruise will be checked thoroughly for errors and archived online with accompanying metadata to detail any chemical analysis and data postprocessing and/or analyses, at the Cooperative Arctic Data and Information Service (www.aoncadis.org), a repository for data collected during research projects funded by the National Science Foundation, under the Arctic Observing Network program.

Figure I.6.4.2: (Top) Potential temperature (θ) versus salinity; (Bottom) dissolved oxygen (O2) versus salinity from select transects occupied during the 2015 NABOS cruise.

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I.6.5. BIOLOGICAL OBSERVATIONS (E. Ershova, IORAS/UAF; K. Kosobokova, IORAS)

I.6.5.1. Sampling scheme

The biological program of the NABOS 2015 cruise was executed by the team of Elizaveta Ershova, Vladimir Gagarin, and Dmitry Kulagin. The main objectives for the biological team were to study the diversity, distribution, and productivity of zooplankton on the East-Siberian Sea shelf and the adjacent slope; to relate the distribution of zooplankton in the study region to the circulation of water masses; and to examine the population ecology of significant taxa using methods of molecular biology. Sampling of zooplankton was conducted along two longitudinal transects in the East-Siberian Sea, as well as opportunistically at a number of stations along the ship’s track (Figure I.6.5.1). The targeted species for genetic analysis included the copepods Calanus glacialis and Metridia longa, and the chaetognath Parasagitta elegans.

Figure I.6.5.1: Map of the sampling area.

I.6.5.2. Sampling methods

Quantitative samples of mesozooplankton were collected using a Juday net with a mesh size of 180 µm and opening diameter of 37 cm, as well as a Bongo net with a mesh size of 180 µm and opening diameter of 60 cm (Figure I.6.5.2). The Juday net was used for collecting stratified samples at depth intervals: ~0-25, 25-65, 65-131, 131-260, and 260-451 m. Exact intervals were determined by hydrology characteristics at each station. The net was towed vertically with a wire speed of 0.5 m/sec, and closed at each designated depth with a messenger, which was propelled down the wire as the net ascended. Zooplankton samples were preserved using 10 % formalin, for later processing in the laboratory. Additionally, qualitative samples were collected using a Bongo net hauled vertically, 100-200 m from the surface. These samples were examined under a microscope, and organisms of interest were selected and preserved separately in 97 % ethanol. The remainder of the sample was pooled and preserved in 97 % ethanol.

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Figure I.6.5.2: Devices: Juday net (left) and Bongo net (right).

I.6.5.3. Preliminary results

Quantitative zooplankton samples were collected along two longitudinal transects in the East Siberian Sea at sixteen stations. In addition, qualitative samples were collected at several stations along the ship's path. In total, seventy-seven samples were collected at twenty-three stations. Of these, twelve were collected using the Bongo net and sixty-five using the Juday net (Table I.6.5.1).

Preliminary results show that the majority of the zooplankton biomass in the deep basin/slope stations was concentrated in the top 50-100 m, with the species Calanus glacialis, Calanus hyperboreus, and Metridia longa being the most important contributors to abundance and biomass. The expatriate Atlantic species Calanus finmarchicus was common in all basin stations, but was absent on the East Siberian shelf. The shallow East-Siberian shelf stations contained fauna typical for Arctic shelf seas, with high contributions of the chaetognath Parasagitta elegans, the small copepods Acartia longiremis and Pseudocalanus spp., and a wide variety of hydrozoan jellyfish. These communities contained markedly lower zooplankton biomass than the adjacent Chukchi Sea (Ershova et al., 2015).

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Table I.6.5.1: Biological stations carried out during NABOS 2015 cruise

Station Date Time Latitude (°N) Longitude (°E) Gear used Number of samples

AT1 28.08.2015 11:30 82.16 131.2 Bongo 1

AT3 28.08.2015 21:00 81.84 164.4 Bongo 1

AT10 1.9.2015 12:30 77.08 128.0 Bongo 1

AT30 7.9.2015 7:30 79.95 162.2 Bongo 1

AT36 8.9.2015 8:00 79.37 173.2 Bongo 1

AT38 8.9.2015 11:30 79.08 120.5 Bongo 2

AT39 9.9.2015 19:30 75.00 121.0 Juday/Bongo 3

AT40 9.9.2015 23:00 75.54 135.0 Juday 2

AT41 10.9.2015 3:50 76.00 154.5 Juday 2

AT42 10.9.2015 8:30 76.46 169.6 Juday/Bongo 3

AT43 10.9.2015 12:00 76.95 120.8 Juday 3

AT44 10.9.2015 16:30 77.45 120.7 Juday/Bongo 4

AT45 10.9.2015 19:30 77.83 141.0 Juday 4

AT48 11.9.2015 6:00 78.57 123.9 Juday 5

AT51 11.9.2015 16:30 78.89 129.2 Juday 6

AT55 13.9.2015 23:30 80.00 179.8 Juday/Bongo 6

AT58 14.9.2015 14:00 79.15 130.8 Juday/Bongo 6

AT61 15.9.2015 3:30 78.44 178.9 Juday 5

AT64 15.9.2015 15:00 77.76 123.4 Juday 5

AT67 16.9.2015 2:00 77.16 132.7 Juday 5

AT70 16.9.2015 15:00 76.23 166.2 Juday/Bongo 5

AT71 16.9.2015 20:15 75.82 152.4 Juday/Bongo 5

AT76 20.9.2015 14:30 78.71 54.1 Bongo 1

61

REFERENCES

Ershova, E. A., R. R. Hopcroft, and K. N. Kosobokova (2015) Inter-annual variability of summer mesozooplankton communities of the western Chukchi Sea: 2004–2012. Polar Biology 38(9), 1461-1481. DOI:10.1007/s00300-015-1709-9.

Ivanov V.V., E.O. Aksenov, Atlantic Water transformation in the eastern Nansen Basin: observations and modelling, 2013, Problemy Arctiki, 1(95), 72-87 (in Russian with English abstract).

Acknowledgments

The successful recovery and deployment of our moorings was a great team effort by all onboard the R/V Akademik Tryoshnikov. Many thanks to all who helped achieve such great results. We particularly appreciate the key role of the ship master Dmitry Karpenko, his chiefmates Dmitry Belkov and Vitaly Rizhov, science chiefmate Michail Romanov, the third chiefmate Evgeny Lubarts, lead in electronics Artem Kavalerov, and bosun Yuri Khromov. We also thank our AARI colleagues, particularly V. Vizitov, for help with resolving the complex permissions to work within the Russian EEZ. Many thanks to Mr. V. Zaitsev for logistical support of the expedition and for preparation of the ship for our cruise, and to E. Morozova for her help with getting clearance from Russian customs. Colleagues from the Russian RosHydroMet and Visa office also deserve our special thanks for their help in getting Russian visas for non-Russian cruise participants.

This work was supported by IARC/UAF. We would also like to thank NSF and NOAA for providing financial support.

62

APPENDIX I: List of NABOS 2015 stations (colors identify specific transects)

##   Date   Time  Lat,  deg.N  

Lat,  min  

Lon,  deg.  E  

Lon,  min  

Depth,  m   Lat   Lon  

AT001   28,08   9:51   82   9,764   94   48,911   2243   82,16273   94,81518  AT002   28,08   15:20   81   48,149   94   17,407   197   81,80248   94,29012  AT003   28,08   17:14   81   50,664   94   18,57   284   81,8444   94,3095  AT004   28,08   20:54   81   53,995   94   27,394   835   81,89992   94,45657  AT005   29,08   1:46   81   57,169   94   32,588   1359   81,95282   94,54313  AT006   29,08   9:44   82   5,854   94   47,105   1988   82,09757   94,78508  AT007   29,08   13:44   82   17,5   95   6,6   2596   82,29167   95,11  AT008   30,08   3:56   82   6,39   97   0,161   2723   82,1065   97,00268  AT009   30,08   9:23   82   5,149   94   45,563   1921   82,08582   94,75938  AT010   1,09   8:50   77   4,529   125   50,034   302   77,07548   125,8339  AT011   1,09   10:49   77   7,295   125   48,233   638   77,12158   125,8039  AT012   1,09   14:41   77   9,57   125   51,342   843   77,1595   125,8557  AT013   1,09   17:03   77   17,394   125   48,666   1212   77,2899   125,8111  AT014   1,09   19:08   77   24,22   125   48,223   1544   77,40367   125,8037  AT015   1,09   21:14   77   31,837   125   48,167   1750   77,53062   125,8028  AT016   1,09   23:26   77   39,253   125   49,99   1852   77,65422   125,8332  AT017   2,09   5:12   77   48,658   125   49,739   1852   77,81097   125,829  AT018   2,09   7:42   77   58,26   125   50,323   2270   77,971   125,8387  AT019   2,09   11:34   78   27,248   125   55,999   2708   78,45413   125,9333  AT020   3,09   17:02   79   59,951   126   0,89   3417   79,99918   126,0148  AT021   3,09   21:07   80   13,649   125   55,909   3514   80,22748   125,9318  AT022   3,09   23:40   80   27,596   125   53,035   3607   80,45993   125,8839  AT023   4,09   2:35   80   40,62   125   50,39   3713   80,677   125,8398  AT024   4,09   5:16   80   54,767   125   44,596   3792   80,91278   125,7433  AT025   4,09   11:56   81   8,006   125   43,021   3792   81,13343   125,717  AT026   6,09   5:17   81   18,38   136   32,686   3200   81,30633   136,5448  AT027   6,09   10:28   81   1,6   137   54,448   2299   81,02667   137,9075  

AT028col   6,09   16:11   80   50,772   139   4,508   -­‐9999   80,8462   139,0751  AT028   6,09   13:39   80   48,82   138   52,739   2011   80,81367   138,879  AT029   6,09   19:09   80   34,45   139   46,808   -­‐9999   80,57417   139,7801  AT030   7,09   5:21   79   57,018   142   18,108   1410   79,9503   142,3018  AT031   7,09   8:41   80   9,536   141   34,246   -­‐9999   80,15893   141,5708  AT032   7,09   11:59   80   21,829   140   36,176   1647   80,36382   140,6029  AT033   7,09   21:39   79   46,795   142   52,322   1005   79,77992   142,872  AT034   8,09   0:15   79   40,458   143   14,3   618   79,6743   143,2383  AT035   8,09   2:34   79   31,238   143   41,925   304   79,52063   143,6988  AT036   8,09   4:33   79   22,453   144   6,604   168   79,37422   144,1101  AT037   8,09   6:34   79   13,901   144   23,718   84   79,23168   144,3953  AT038   8,09   8:02   79   4,68   144   59,65   82   79,078   144,9942  AT039   9,09   15:51   75   0,194   159   58,894   47   75,00323   159,9816  AT040   9,09   19:46   75   32,13   160   45,035   50   75,5355   160,7506  

63

AT041   10,09   0:29   75   59,803   161   25,748   51   75,99672   161,4291  AT042   10,09   5:10   76   27,913   162   10,358   81   76,46522   162,1726  AT043   10,09   8:51   76   56,963   162   59,383   102   76,94938   162,9897  AT044   10,09   12:50   77   27,54   163   59,738   127   77,459   163,9956  AT045   10,09   16:16   77   49,993   164   39,068   222   77,83322   164,6511  AT046   10,09   20:34   78   10,561   165   22,331   294   78,17602   165,3722  AT047   10,09   23:18   78   19,997   165   41,654   377   78,33328   165,6942  AT048   11,09   2:12   78   33,034   165   56,645   539   78,55057   165,9441  AT049   11,09   6:03   78   38,355   166   13,45   866   78,63925   166,2242  AT050   11,09   8:15   78   41,245   166   24,488   1043   78,68742   166,4081  AT051   11,09   11:55   78   52,882   166   51,133   1584   78,88137   166,8522  AT052   11,09   17:38   79   4,175   167   26,8   2006   79,06958   167,4467  AT053   11,09   21:37   79   17,903   168   2,04   2367   79,29838   168,034  AT054   12,09   0:53   79   31,058   168   39,64   2585   79,51763   168,6607  AT055   13,09   18:37   79   59,929   177   59,762   1688   79,99882   177,996  AT056   14,09   1:07   79   40,081   177   7,858   1770   79,66802   177,131  AT057   14,09   4:59   79   22,151   176   23,172   2074   79,36918   176,3862  AT058   14,09   8:39   79   9,19   175   51,542   2167   79,15317   175,859  AT059   14,09   14:48   78   55,976   175   1,948   2271   78,93293   175,0325  AT060   14,09   18:36   78   41,957   174   46,29   2219   78,69928   174,7715  AT061   14,09   22:10   78   26,201   173   59,356   1930   78,43668   173,9893  AT062   15,09   3:47   78   12,204   173   39,938   1630   78,2034   173,6656  AT063   15,09   7:17   77   59,299   173   13,586   1122   77,98832   173,2264  AT064   15,09   10:44   77   45,254   172   55,65   1069   77,75423   172,9275  AT065   15,09   15:47   77   32,436   172   35,216   954   77,5406   172,5869  AT066   15,09   19:08   77   21,366   172   11,704   739   77,3561   172,1951  AT067   15,09   22:10   77   9,586   171   47,257   446   77,15977   171,7876  AT068   16,09   3:18   77   5,424   171   40,298   389   77,0904   171,6716  AT069   16,09   6:36   76   47,287   171   9,484   295   76,78812   171,1581  AT070   16,09   11:43   76   14,092   170   16,77   227   76,23487   170,2795  AT071   16,09   16:47   75   48,968   169   27,287   149   75,81613   169,4548  

AT072cal   19,09   1:10   77   10,424   125   49,919   902   77,17373   125,832  AT073   19,09   13:05   78   8,244   125   50,924   2445   78,1374   125,8487  AT074   19,09   16:58   78   17,514   125   52,325   2595   78,2919   125,8721  

AT075cal   20,09   8:55   78   28,145   125   55,537   2700   78,46908   125,9256  AT076   20,09   10:42   78   42,005   125   51,479   902   78,70008   125,858  

AT077_prod   22,09   7:05   79   44,368   107   48,943   1447   79,73947   107,8157  AT078   23,09   10:02   82   11,821   94   58,033   2360   82,19702   94,96722  AT079   24,09   8:29   82   22,458   94   58,668   2700   82,3743   94,9778  AT080   24,09   12:35   82   34,632   95   30,082   2360   82,5772   95,50137  AT081   25,09   19:10   80   25,202   74   30,082   92   80,42003   74,50137  AT082   25,09   20:13   80   24,946   74   14,706   154   80,41577   74,2451  AT083   25,09   21:15   80   24,917   74   1,018   224   80,41528   74,01697  AT084   25,09   22:20   80   24,832   73   54,052   257   80,41387   73,90087  AT085   25,09   23:37   80   24,839   73   47,454   303,5   80,41398   73,7909  AT086   26,09   1:10   80   24,961   73   30,251   403   80,41602   73,50418  

64

AT087   26,09   3:15   80   25,202   72   54,521   495   80,42003   72,90868  AT088   26,09   5:16   80   25,1   71   54,769   565   80,41833   71,91282  AT089   26,09   7:45   80   24,96   70   3,151   586   80,416   70,05252  AT090   26,09   10:08   80   25,042   67   59,222   528   80,41737   67,98703  AT091   26,09   11:30   80   25,067   66   59,975   520   80,41778   66,99958  AT092   26,09   13:06   80   25,076   65   59,5   305   80,41793   65,99167  AT093   26,09   14:47   80   24,8   65   0,101   227   80,41333   65,00168  AT094   26,09   15:52   80   24,732   64   30,094   163   80,4122   64,50157  

65

APPENDIX II: Schematics of moorings recovered in 2015

Figure A.II.1. NABOS M1-1a (2013-15) mooring schematic.

66

Figure A.II.2. NABOS M1-2a (2013-15) mooring schematic.

67

Figure A.II.3. NABOS M1-3a (2013-15) mooring schematic.

68

Figure A.II.4. NABOS M1-4a (2013-15) mooring schematic.

69

Figure A.II.5a. NABOS M1-5a (2013-15) mooring schematic.

70

Figure A.II.5b. Schematic of upper ocean termistor array for NABOS M1-5a (2013-15) mooring.

71

Figure A.II.6a. NABOS M1-6a (2013-15) mooring schematic.

72

Figure A.II.6b. Schematic of upper ocean termistor array for NABOS M1-6a (2013-15) mooring.

73

Figure A.II.7a. NABOS M3e (2013-15) mooring schematic.

74

Figure A.II.7b. Schematic of upper ocean termistor array for NABOS M3e (2013-15) mooring.

75

Figure A.II.8. NABOS M6b (2013-15) mooring schematic.

76

APPENDIX III: Schematics of deployed moorings

Figure A.III.1. NABOS M1-1b (2015-17) mooring schematic.

77

Figure A.III.2a. NABOS M1-2b (2015-17) mooring schematic.

78

Figure A.III.2b. Schematic of upper ocean termistor array for NABOS M1-2b (2015-17) mooring.

79

Figure A.III.3. NABOS M1-3b (2015-17) mooring schematic.

80

Figure A.III.4. NABOS M1-4b (2015-17) mooring schematic.

81

Figure A.III.5a. NABOS M1-5b (2015-17) mooring schematic.

82

Figure A.III.5b. Schematic of upper ocean termistor array for NABOS M1-5b (2015-17)

mooring.

83

Figure A.III.6a. NABOS M3f (2015-17) mooring schematic.

84

Figure A.III.6b. Schematic of upper ocean termistor array for NABOS M3f (2015-17) mooring.

85

Figure A.III.7. AWI AK1-1 (2015-17) mooring schematic.

86

Figure A.III.8. AWI AK2-1 (2015-17) mooring schematic.

87

Figure A.III.9. AWI AK3-1 (2015-17) mooring schematic.

88

Figure A.III.10. AWI AK4-1 (2015-17) mooring schematic.

89

Figure A.III.11. AWI AK5-1 (2015-17) mooring schematic.

90

Figure A.III.12. AWI/IARC AK6-1 (2015-17) mooring schematic.

91

Figure A.III.13. AWI AK7-1 (2015-17) mooring schematic.