Temporal variations of pCO2 in surface seawater of the Arabian Sea in 1995

As part of the JGOFS program in the Arabian Sea we continually measured the partial pressure of CO2 gas in surface seawater (pCOsea2) and in the atmosphere above the sea surface (pCOair2) along six similar cruise tracks in January, February, March, July, November, and December of 1995. The observed variations of pCOsea2 reached over 260 μatm close to the Omani coast in January–February and July–August. Offshore the pCOsea2 variations with time were relatively small (<40 μatm). The pCOair2 shifted by 15 μatm between the northeast and southwest monsoons. er to estimate monthly and annual mean of CO2 flux in the Arabian Sea, we used sea surface temperature and wind speed data, given on a 2.5°×2.5° resolution, from FNMOC and interpolated the observed pCOsea2 data both in time and space. Close to the Omani coast, the estimated monthly mean CO2 efflux across the air–sea interface varies from 8.3 to 44 mmol m-2 month-1 during most of the year and up to 312.8 mmol m-2 month-1 during the southwest monsoon season (July/August). Overall, the annual mean CO2 flux from the northern Arabian Sea to the atmosphere is estimated to be 0.46 mol m-2 yr-1 or 7.0 Tg C yr-1.