Time-series observations in the Northern Indian Ocean

V.V.S.S. SarmaNational Institute of Oceanography

Visakhapatnam, India

The Second GEOSS Asia-Pacific Symposium, Tokyo, 14-16th April 2008

Seasonal variations in winds, currents and ITCZ in NIO

Importance of N. Indian Ocean

5.2-13.3 5.6-7.3

0.4-6.5

0.81-6.3

0.07-5.5

0.7-5.2

0.6-3.4

0.6-3.4

8.1-10.5

Primary production Sea-to-air flux of CO2

Oxygen at 500 m deepSinking organic carbon

mmol C/m2/d micromol/kg

NCP and sea-to-air fluxes of CO2

Region Sea-to-air flux (F) New/NCP(NP) F/NP Ratio

Eq.Pacific (HNLC) 0.80 to 1.00 0.65 to 0.98 1.0-1.2(1980-2000) (Feely et al., 2002) (LeBorgne et al., 2002)

Arabian Sea 0.07 to 0.09 0.17 to 0.20 0.4-0.45 (1995) (Sarma., 2003) (Sarma, 2004)

Bay of Bengal 0.0025 to 0.005 0.059-0.077 0.19-0.22 (Takahashi et al., 2002) (Sarma, 2006)

(PgC y-1)

Deep water DIC in the World Oceans

Sarma et al. 2007

(µmol kg-1)Source: WOCE data on sigma-3: 41.488 (~3000m)

-1.4

-1.2

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

PgC

y-1

Antarctic

S Indian

S Pacific

S Atlantic

N Indian

Eq Indian

Eq Pacific

Eq Atlantic

N.Cen Pacific

N.Cen Atlantic

N Pacific

N Atlantic

0

0.2

0.4

0.6

0.8

degr

ee C

Antarctic

S Indian

S Pacific

S Atlantic

N Indian Eq

Indian

Eq Pacific

Eq Atlantic

N.Cen Pacific

N.Cen Atlantic

N Pacific

N Atlantic

-80

-60

-40

-20

0

20

40

60

80

Perc

ent c

hang

e

Antarctic S Indian

S Pacific

S Atlantic

N Indian

Eq Indian

Eq Pacific

Eq Atlantic

N.Cen Pacific

N.Cen Atlantic

N Pacific

N Atlantic

-10

0

10

20

Per

cent

cha

nge

Antarctic

S Indian

S Pacific

S Atlantic

N Indian

Eq Indian

Eq Pacific

Eq Atlantic

N.Cen Pacific

N.Cen Atlantic

N Pacific N

Atlantic

Primary Production SST

Fe deposition Scalar wind stress

Change in conditions from SeaWiFS to CZCS era

Gregg et al., 2002

Physical forcing..upwelling in the Arabian Sea

Nutrients + Mineral ballast

Bottom flow

Lateral Input

Scavenging

Biological production + Particle aggregation

Fresh water

Particle ballast in the Bay of Bengal

Phytoplankton Blooms in the Bay of Bengal

Vinayachandran et al 2003

Tracks of cyclones and depressions in the Bay of Bengal

1997 1998 1999

2000 2001 2002

2003

2006

2004 2005

2007

Source : http://www.weather.unisys.com

Time-series observations in the northwestern Indian Ocean

•Impact of anthropogenic perturbations on oceanographic –atmospheric processes in and around India in the context of Global Change (CSIR Network Project No. CMM 009)Since 2002

Ongoing time-series projects in thewest coast of India (eastern Arabian Sea)

Sampling at Monthly Scale

0 60 120 180 240 300 36030

20

10

0

(a) Temp (ºC)

0 60 120 180 240 300 36030

20

10

0

(c) Oxygen (µM)

0 60 120 180 240 300 36030

20

10

0

(d) Nitrate (µM)

Days

0 60 120 180 240 300 36030

20

10

0

(b) Salinity

Evolution .. anoxia & H2S..

0 60 120 180 240 300 36030

20

10

0

(i) Chlorophyll amg m-3

Evolution .. anoxia & H2S..

Days

Dep

th (m

)

0 60 120 180 240 300 36030

20

10

0(e) Nitrite (µM)

0 60 120 180 240 300 36030

20

10

0

(f) Nitrous Oxide (nM)

0 60 120 180 240 300 36030

20

10

0(g) Ammonia (µM)

Days0 60 120 180 240 300 360

30

20

10

0

14

Evolution anoxia & H2S..

(h) Hydrogen sulphide(µM)

Time-series observations in the northeastern Indian Ocean

Visakhapatnam BOBFLUXSOLAS

•Biogeochemical Response of coastal waters off VisakhapatnamTo extreme climatic events and human interference – SurfaceOcean Lower Atmosphere Study (SOLAS) since 2006

•Bay of Bengal Carbon Flux Study (BOBFLUX) – Council of Scientific and Industrial Research (CSIR) Since 2008

•Variability of Ecosystem and Biogeochemistry in Godavari Estuarine System (VEBGES) – Supra Institutional Project (SIP)Of Council of Scientific and Industrial Research (CSIR) since2007.

•Coastal Ocean Monitoring and Prediction system (COMPAS)-Ministry of Earth Science since 2008

Ongoing time-series projects in theeast coast of India (western Bay of Bengal)

Sampling at Monthly Scale

Sampling at diurnal to seasonal Scale

Sampling at daily Scale

Sampling at seasonal Scale

Impact of rainfall on biogeochemical processes

Distance (km)

14-21 Sep 2007 22-29 Sep 2007 30-07 Oct 2007

08-15 Oct 2007 16-23 Oct 2007 23-31 Oct 2007

Impact of Rainfall on Chlorophyll distribution in the coastal Bay of Bengal

Source: Weekly average chlorophyll-a by SeaWiFS from NASA

9 Nov 07 11 Nov 07 14 Nov 07 16 Nov 07 23 Nov 07 26 Nov 07

8 Nov 07 10 Nov 07 14 Nov 07 15 Nov 07 16 Nov 07 18 Nov 07

Influence of episodic atmospheric events on SST & chl-a

NE NE NENWNWNW

SST

Chl

-aW

inds

Net community Production (mmol O2/m2/d)

Phytoplankton production versus Bacterial Biomass

Station Oct 2007 Nov 2007 Dec 2007 Jan 2008 Feb 2008

V1 147.2 137.8 699.7 260.30 297.9

V2 246.2 27.3 659.3 142.50 356.9

V4 61.8 40.9 2.5 0.60 -93.8

V6 97.7 75.8 -42.9 -78.8 -134.8

Distance (km)

October 2007

November 2007

December 2007

January 2008

February 2008

Janu

ary

2008

Dec

embe

r 200

7N

ovem

ber 2

007

Oct

ober

200

7Fe

brua

ry 2

008Chlorophyll-a Dissolved O2 Nitrate Silicate

Formation of sub-oxic conditions in the Shelf waters

Distance (km)

Variability of Ecosystem and Biogeochemistry in Godavari Estuarine System (VEBGES)

252 277 302 327 352 12 37

0

200000

400000

600000

252 277 302 327 352 12 37

0

200000

400000

600000

Time-series variations in Godavari EstuaryRiver discharge (Cusecs/sec)

Suspended matter (g/L)

Salinity

Nutrients (µmol/kg)

Silicate (µmol/kg)

Julien Days (Sep 07-Feb 08)

252 277 302 327 352 12 37

0

200000

400000

600000

252 277 302 327 352 12 37

0

200000

400000

600000

Julien Days (Sep 07-Feb 08)

River discharge (Cusecs/sec)

Bulk chlorophyll

>10 µm chlorophyll >0.2 & <2 µm chlorophyll

>2 & <10 µm chlorophyll

Time-series variations in Godavari Estuary

Rates of changes in salinity and nutrients in Godavari Estuary

Parameter Rate of change per day

Salinity +0.2 psu

Dissolved O2 +0.2 µmol/kg

Nitrate -0.1 µmol/kg

Phosphate -0.01 µmol/kg

Silicate -0.4 µmol/kg

-400

-200

0

200

400

600

800

mm

ol O

2 m-2 d

-1

0

200

400

600

mm

ol O

2 m-2 d

-1

240 280 320 360 400 440-400

0

400

800

1200

1600m

mol

O2 m

-2 d

-1

Net Comm. Prod.

Dark Comm. Resp.

Gross Pri. Prod.

Time-series variationsin plankton metabolicrates in Godavariestuary

35 75Julien day

Heterotrophy Autotrophy

2 fold increase in Production

~65% of the GPP is respired

Future plans:both coastal & estuary time-series stations

Time-series measurements of triple oxygen isotopes and O2/Ar ratios in the surface ocean

Time-series measurements of inorganic carbon parameters

Measurements of δ13C, δ15N of dissolved and particulate (both organic & Inorganic)

Processing HPLC and DOC samples and isotopic ratios of δ13C of DOC

Phytoplankton growth and grazing rates (once in a week!!)

Nutrients utilization rates (once in a week!!)

Bacterial respiration rates (Unisense sensor)

Consumption and exchanges rates of carbon at the Benthic boundary

Water exchange rates using Radon isotopes.

Bay of Bengal Carbon Flux Study (BOBFLUX)

Visakhapatnam BOBFLUX

Objectives of Bay of Bengal Carbon Flux Study (BOBFLUX)

1. What is the short-term to inter-annual variability in plankton metabolic rates suchas gross and net community production, and community respiration?

2. How river inputs influence the plankton metabolic rates?

3.What is the influence of cyclones on nutrient injections, primary production andair-sea exchange of trace gases?

4. What is the seasonal to inter-annual variability in export production?

5. What is the relationship between primary and export production?

6. What is the influence of river runoff on bacterial growth rates and respiration?

7. What are the seasonal variations in transfer velocities of trace gases?

8. What are the temporal and spatial variations in the air-sea exchange of tracegases?

Meteorological Buoy

Remote Access Sampler (30 m)

Sediment trap (150 m) – Weekly sampling

Optode/current meter (500 m)

ADCP (1800 m)

Sediment trap (1700 m) – Weekly sampling

Bottom (2000 m)

Optode/current meter (20 m)

Schematic of mooring in the Bay of Bengal

Floating sedimentTraps – samplingOnce in 3 months

VisakhapatnamBOBFLUX

BOBFLUX

Time-series transect observations

0.25o water column sampling for biogeo-chemical parameters – nutrients, chl-a,HPLC, DIC, TA, pH, DOC, SSM, O2isotopes, O2/Ar, Plankton composition etc. Underway pCO2 system, SST,SSS, Chl-a,& dissolved O2Underway plankton metabolic rates bytriple oxygen isotopes & O2/Ar Isotopic ratios of δ13C-DIC, DOC ofdissolved δ13C & δ15N of particulate matter

Sampling : Bi-monthlyStarts from September 2008

Thank You