SURFACE-WATER CARBON-DIOXIDE IN THE SOUTHWEST INDIAN SECTOR OF THE SOUTHERN-OCEAN - A HIGHLY VARIABLE CO-2 SOURCE SINK REGION IN SUMMER

Measurements of partial pressure of carbon dioxide (pCO2), total dissolved inorganic carbon (TCO2), total alkalinity (TA) and chlorophyll a (Chl a) have been made in surface water in the southwestern Indian sector of the Southern Ocean (20-85-degrees-E) in the austral summer (INDIVAT V cruise, January-February 1987). Between Antarctica and Africa, pCO2 distribution was linked to the oceanic frontal zones and Chl a variations. The pCO2 spatial structure was very close to that explored in summer 1967 in the same region but the pCO2 differences between the ocean and the atmosphere were smaller in 1987 than 20 years ago. At all latitudes we found strongly contrasting surface pCO2 characteristics between eastern (around 80-degrees-E) and western (around 25-degrees-E) regions; CO2 sources were mainly in the west and CO2 sinks in the east. South of 60-degrees-S, the contrast could be due to biological activity. Between 60-degrees-S and the Antarctic Polar Front, intensification of upwelling might be responsible for the higher pCO2 values in the west.