Carbon dioxide in the Northern Indian Ocean during southwest monsoon

Carbon dioxide in the Northern Indian Ocean during southwest monsoon

V.V.S.S. Sarma, M. Dileep Kumar, S.N. de Sousa and M. D. George

National Institute of Oceanography, Dona Paula - 403 004, Goa.

Abstract

Data on the carbon dioxide system have been collected during southwest monsoon season in the northern Indian Ocean. Total Alkalinity (TA) is much lower in the Bay of Bengal than in the Arabian Sea at all depth levels. TA is comparatively low in intermediate waters of the northern Arabian Sea due to nitrate reduction. This was more obvious between 17° and 20° N. TCO₂ concentrations were comparatively higher (by ~30 m M) in the Arabian Sea than that in the Bay of Bengal. A marginal increase in TCO₂ in the surface layers towards the northern Arabian Sea is due to upwelling either driven by findlater jet or gyral circulation. Surface pCO₂ concentrations ranged between 360 and 420 m atm in the Bay of Bengal and from 390 to 440 m atm in the Arabian Sea. A gradient of ~50 m atm in pCO₂ occurred between the north and the southern Bay of Bengal. The highest concentration observed, at mid-depths, during this season was ~1250 m atm. The air to sea fluxes of carbon dioxide varied from 2 to 22 mmol. m^-2.d^-1 in the Arabian Sea while these were from 0.6 to 3.5 mmol. m^-2.d^-1 in the Bay of Bengal.