Kumar, M.
Dileep, V.V.S.S. Sarma, P.S. Swathi1, S. Prasannakumar, M.
Madhupratap, V. Ramaswamy, M. M. Sarin2, M. Gauns, N. Ramaiah, S.
Sardessai and S. N. de Sousa
National Institute of
Oceanography, Dona Paula, Goa 403 004, India, E-mail: dileep@csnio.ren.nic.in, 1CSIR
Centre for Mathematical Modeling and Computer Simulation, Bangalore 560 037,
India and 2Physical Research Laboratory, Navrangpura, Ahmedabad 380
009, India
Carbon budget in the eastern and central Arabian Sea
Carbon budget for the eastern and central Arabian Sea was constructed using results from the Modular Ocean Model and biogeochemical data collected largely under Indian JGOFS programme. The study region (east of 64oE and between 11 and 21oN) was divided into two vertical boxes; surface box of the top 100 m and subsurface box of 100-1000 m. Exchange of significant quantities of water with the rest of the Arabian Sea occurs at surface than in the deep on an annual basis. Maximal water flow occurred in surface box (83 x1012 m3 in SW monsoon) than in subsurface box (~29 x1012 m3 in both intermonsoon and SW monsoon). Carbon exchanges with surrounding Arabian Sea waters occurred prominently in SW monsoon followed by winter and intermonsoon in surface layers while in the subsurface layers fluxes in intermonsoon are significant followed by SW monsoon and winter. The physical pump supplies 82 Tg C y-1 to the surface box whereas 57 Tg C y-1 flows out from subsurface layers. The carbon supplied by circulation appears to account for only 1/10 to 1/8 of the primary production (234 TgC y-1) wherein the latter seems to sustain an annual living biomass (phytoplankton, bacteria, micro- and mesozooplankton) of 644 Tg C. Bacterial respiration (67-735 Tg C y-1) together with that supplied by physical pump (25 Tg C y-1) maintains the carbon requirements of the study region. Therefore, the central and eastern Arabian Sea is a net sink of oceanic dissolved carbon where 644 Tg C y-1 is siphoned into living organic pool (~2,500 Tg C is present as particulate organic pool in the study area with little seasonal variability), 3 Tg C y-1 is exported to the deep sea and 32 Tg C is emitted to atmosphere.