A sink for atmospheric carbon dioxide in the northeast Indian Ocean

Intensive observations in the northeast Indian Ocean (Bay of Bengal) during the pre-southwest and northeast monsoon seasons of 1991 reveal that freshwater discharge from rivers of the Indian subcontinent exerts the dominant control over total carbon dioxide (TCO2) and pCO(2) distributions in surface waters. Low pCO(2) levels occur within the low-salinity zones, with a large area in the northwestern bay acting as a sink for atmospheric CO2. Only a part of the observed pCO(2) variation can be accounted for by the effect of salinity, and biological production supported by external nutrient inputs in conjunction with strong thermohaline stratification may be more important in lowering surface water pCO(2) by > 100 mu atm relative to that in the atmosphere. The pCO(2) distribution is seasonally variable and appears to be controlled by the spreading of fresher waters by the prevailing surface circulation.