BIOGEOCHEMICAL SIGNIFICANCE OF EDDIES OF THE EASTERN ARABIAN SEA

Abstract. Within the Arabian Sea, the western part is considered to be highly productive when compared to the northern, central and eastern parts of the basin. Despite the contrasting chlorophyll and primary productivity patterns, sediment trap data show that annual fluxes of organic carbon reach comparable rates in most regions of this highly productive basin. The traditional mechanisms of nutrient supply to the upper ocean waters of the Arabian Sea cannot only account for this. Episodic injections of nutrients associated with cold-core eddies stimulate rapid biological activity and increase biological production in the open ocean waters of the eastern Arabian Sea during the demise of the southwest monsoon. In addition to wind-driven coastal upwelling during the monsoons, annually, an eddy-mediated enhanced biological production, at regional to basin-wide scales is proposed. The enhanced production caused by a high nutrient supply mechanism such as a meso-scale eddy leads directly to organic carbon fluxes to the deep Arabian Sea. The elevated export flux occurred in association with the rapid response of grazers was imported to the deeper layers which leads to a spectacular enhancement of biogenic particle sedimentation