Total detrital suspended matter and detrital clay distribution during the southwest monsoon (July–August) and the postmonsoon (November–December) season during 2007 in the Bay of Bengal and in the Arabian Sea

Associated with the coupled land–ocean heating–cooling, seasonal reversal of monsoon winds regulates hydrography, precipitation, upwelling, fluvial influx and a host of biogeochemical processes. We evaluate the role of the monsoon winds, fluvial discharge and currents on continental flux dynamics from advection magnitude of clays over an anomalous high precipitation regime of the southeastern Arabian Sea. Coupled with the intense rains and a high fluvial discharge, we archived an elevated content of detrital clays (> 41 mg/l) during the southwest monsoon over the < 40 m water depth. The deeper waters (> 40 m), however, had much reduced detrital clays (< 6 mg/l) year round. Therefore, two distinct environments (high and low detrital clays) prevailed over the shelf. Derived from the variations in the clays in the local riverine discharge and in the seawater loads, we found a dominant role of the southwest monsoon winds and that of the winter and the southwest monsoon (summer) coastal currents over the dispersal and sequestration processes. Over the inner shelf, an alongshore (equatorward) advection and merging of several, small, fluvial plumes by the southwest monsoon winds had sequestered most of the local fluvial discharge over the shallow region only. The outer-shelf received detritus mostly as a result of (a) the high salinity Arabian Sea Water during the southwest monsoon, (b) through the Bay of Bengal Water and (c) by way of aeolian supply from the Arabia and the Somalia.