CLIMATE CHANGE IMPACTS ON PHYTOPLANKTON BIODIVERSITY &

IMPACTS ON THE ECOSYSTEM OF THE ARABIAN SEA

Joaquim I. Goes & Helga Gomes, Bigelow Lab. USA

Prasad Thoppil, John Kindle & Sergio de Rada, NRL, USA

Adnan Al Azri, Sultan Qaboos Univ., Oman

Prabhu Matondkar & Sushma Parab NIO, India

R. M. Dwivedi, Space Applications, Centre, India

John Fasullo, NCAR, USA, Fei Chai, Univ. Maine, USA

Richard Barber, Duke Univ., USA

UNIQUE FEATURES OF THE ARABIAN SEA

Comes under the influence of the monsoon winds which reverse their direction seasonally driving one the most energetic current systems and the greatest seasonal variability of phytoplankton biomass

Is a tropical sea and the northwestern landlocked arm of the Indian Ocean

Reversal of the winds and their intensity is strongly regulated by thermal gradient between land and sea

Schematic showing snow cover extent and wind direction superimposed on an ocean color chlorophyll image for the northeast monsoon season

(Nov-Feb).

LOW

HIGH

0.1 0.5 1.0 2.0 5.0 10.0 20.0

WINTER MONSOON

Schematic showing the reversal in wind direction during the southwest monsoon (Jun-Sept), superimposed on satellite derived chlorophyll fields

LOW

HIGH

0.1 0.5 1.0 2.0 5.0 10.0 20.0

SUMMER MONSOON

LESS PHYTO

COLDER LANDMASS

SEA

MORE SNOW

WEAKER SW MONSOON WINDS

WEAKER UPWELLING

WEAKER LAND SEA PRESSURE GRADIENT

HIGHER ALBEDO

SEA

LESS SNOW

STRONGER SW MONSOON WINDS

STRONGER LAND SEA PRESSURE GRADIENT

WARMER LANDMASS

LOWER ALBEDO

Schematic showing the SW Monsoon response of the Arabian Sea to snow cover over the Himalayan-Tibetan

Plateau

Warming of SW Eurasia mirrors the global-land signal, but recent warming anomalies are >50% larger than global temperature trends.

SW Eurasian-Land Warming

-8

-4

0

4

8

1967 1971 1975 1979 1983 1987 1991 1995 1999 2003

Sn

ow

Co

ver

Ext

ent

(%)

-8

-4

0

4

8

YEAR

Southwest Asia

Himalayan-Tibetan Plateau

Trend line showing anomalies (departures from monthly means) of snow cover extent over Southwest Asia and

Himalayas-Tibetan Plateau between 1967 and 2003.

70 years of global warming?: Photograph of the Pindari glacier in the Himalayas taken on October 7, 1936, by then Deputy Conservator of Forests F W Champion. 70 years later at the exact spot, his grandson James Champion photographed the same glacier. (Source Sunday Indian Express, 29th Dec. 2006).

Interannual changes in chlorophyll along coast of Somalia since 1997

(Goes et al., Science, 2005 )

0

0.4

0.8

1.2

1.6

2

1997 1998 1999 2000 2001 2002 2003 2004

Year

Chlor

ophy

ll (mg

m-3

)

SeaWiFS derived chlorophyll fields during the peak southwest monsoon growth season of 1997 and 2006

Sept. 1997

India

Oman

Sept. 2006

India

Oman

The Arabian Sea’s permanent oxygen minimum zone

0.1 0.5 1.0 2.0 5.0 10.0 20.0

OMZ

OMAN

SOMALIA

FISH MORTALITY OMAN – NOV 2005FISH MORTALITY OMAN – NOV 2005

SEA

LESS SNOW

WARMER AND HUMID WINDS

WARMER LANDMASS

WEAKER CONVECTIVE MIXING

LESS PHYTO

STRONGER CONVECTIVE MIXING

MORE PHYTO

COLDER LANDMASS

SEA

MORE SNOW

COLDER AND DRIER WINDS (E>P)_

NORTHEAST MONSOON

Air-temperature and Relative humidity for the northern Arabian Sea (60°E-70°E, 14°N-25°N).

Annual trends of net heat flux (NCEP-NCAR) (60-70°E, 14°N-25°N) and Mixed Layer Depth (XBT, JEDAC, USA)

Observed and model-derived MLD for winter (Jan – Feb), and model derived Sea Surface Salinity (SSS, psu) during Jan – May for the 60°E-70°E, 14°N-25°N. Model derived fields are obtained from the ECCO-JPL Kalman Filter Assimilation project.

Winter mean SeaWiFS Chl a averaged over the Eastern Arabian Sea (EAS, 66°E-70°E, 15°N-24°N) and in the western Arabian Sea (WAS, 55°E-62°E, 17.5°N-22.5°N).

EAS

WAS

0.5

0.7

0.9

1.1

1.3

1.5

1996 1998 2000 2002 2004 2006

Year

Chl

orop

hyll

a (m

g m

-3)

High chlorophyll concentrations during the NEM are being caused by blooms of dinoflagellate Noctiluca miliaris

Its appearance in bloom proportions during the NEM is unprecedented as no reports of blooms of this organism during Int. Arabian Sea JGOFS 1992 to 1996 or from Int. Indian Ocean Expeditions of the 1960’s.

It occurs in (cold) <22oC, nutrient rich and oxygen poor waters

Noctiluca is a heterotrophic dinoflagellate containing a green endosymbiont “Pedinomonas noctilucae”

Noctiluca appears to have replaced diatoms as the major bloom forming phytoplankton of the NEM.

CHARACTERISTICS OF ARABIAN SEA NOCTILUCA MILIARIS BLOOMS

PHYTOPLANKTON BLOOM OF 2003

Weekly SeaWiFS and MODIS/Aqua Level-3 merged Chl a images with Sea Surface Height anomalies and geostrophic velocity

vectors from TOPEX/POSEIDON and ERS-2

Gomes et al. (2008) Deep-Sea Research

20th Feb 2008

OMAN

Precipitable water from SSM/I for June showing particularly strong postive and pervasive trends in the Arabian Sea

(John Fasullo NCAR)

Is the appearance of N. miliaris blooms the result of climate change or natural variability?

What are the long-term impact of this possible change in phytoplankton biodiversity and biological productivity on:

OUTSTANDING QUESTIONS FOR THE ARABIAN SEA

•Carbon delivery to deeper layers of the Arabian Sea

•Bacterial processes

•Denitrification rates

•The Oxygen Minimum Zone and

•Increased storm activity

•Coastal Fisheries

• 1/8-degree NCOM (Navy Coastal Ocean Model)

• 30S to 30N, 30.5 to 121.5E

• Mercator grid (~13km), 40 Levels σ/z

• Boundary and initial conditions from Global NCOM

• 0.5-degree NOGAPS Atmospheric forcing

• MODAS: Full 3D Temperature and Salinity relaxation

• Initial simulation for 2007

INDIAN OCEAN CIRCULATION INDIAN OCEAN CIRCULATION MODELMODEL

((John Kindle & Sergio deRadaJohn Kindle & Sergio deRada))

PhysicalModel

Nitrate[NO3]

Advection& Mixing

SmallPhytoplankton

[P1]NO3

Uptake

Micro-Zooplankton

[Z1]

Grazing

Ammonium[NH4]

Excretion

NH4

Uptake

Detritus-N[DN]

FecalPellet

Sinking Silicate[Si(OH)4]

Diatoms[P2]

Si-Uptake

N-UptakeMeso-zooplankton

[Z2]

Sinking

Detritus-Si[DSi]

GrazingFecalPellet

Sinking

Predation

Lost

Total CO2

[TCO2]

BiologicalUptake

Air-Sea Exchange

Dissolution

Carbon, Silicate, Nitrogen Ecosystem Model (CoSiNE) Chai et al. 2002; Dugdale et al. 2002

Chai et al., 1996; 2003

Iron

Iron

Iron

SEAWIFSSEAWIFS MODELMODEL

3030thth Sept 2006 Sept 2006 3030thth Sept 2006 Sept 2006

“Nothing in the sea falls haphazard; if we cannot predict, it is because we do not know the cause, or how the cause works..."

Henry Bryant Bigelow

ACKNOWLEDGEMENTS

This work is being funded by NASA Oceans and Ice & NASA Biodiversity and Ecosystem Programs. We are thankful to the National Institute of Oceanography

and the Indian Space Research Organization for supporting ship

observations. Special thanks to Woody Turner and Paula Bontempi for their

support