HIGH BIOLOGICAL PRODUCTIVITY IN THE INTERIOR ARABIAN SEA DURING SUMMER MONSOON DRIVEN BY EKMAN PUMPING AND LATERAL ADVECTION

S. Prasanna Kumar*, M. Madhupratap, M. Dileep Kumar, P.M. Muraleedharan, Surekha Sawant, Mangesh Gauns & V.V.S.S. Sarma

National Institute of Oceanography, Dona Paula, Goa 403 004, India
Submitted to JGR-Oceans
30 June 1998

Ocean interiors are generally oligotrophic. Recent results from the central Arabian Sea show that the Arabian Sea may be an exception to this rule. Here we report the first observational evidence of this (high biological production) in the central Arabian Sea during summer monsoon of 1995 and 96, based on shipboard measurement under Indian programme of Joint global Ocean Flux Study (JGOFS). The findings are particularly pertinent to the southern areas (south of 15^oN) which were hitherto presumed to be downwelling, oligotrophic provinces. We describe how the interior ocean can get fertilized by physical forcings through a combination of lateral advection from coastal upwelling regions of Somalia and Arabia and open ocean upwelling, the latter unique to the Arabian Sea. These findings help to explain several other processes such as the low oxygen content at intermediate depths of the open Arabian Sea, the dilemma that denitrification processes are decoupled from productive coastal waters and that high particle fluxes are observed in central regions.