High-resolution numerical modelling of seasonal volume, freshwater, and heat transport along the Indian coast

Abstract. Seasonal reversal of winds and equatorial remote forcing influences the circulation of the Arabian Sea (AS) and Bay of Bengal (BoB) basins in the North Indian Ocean. In this study, we numerically modelled the physical characteristics of AS and BoB, using the MITgcm model at a high spatial resolution of 1/20° forced with climatological initial and boundary conditions. The simulated temperature, salinity, and flow fields were validated with satellite and in situ datasets. We then studied the exchange of coastal waters by evaluating transports computed from the model simulations. The alongshore volume transport on the eastern coast is stronger with high seasonal variability due to the poleward-flowing western boundary current and equatorward-flowing East Indian Coastal Current. West coast transport is influenced by large intraseasonal oscillations. The alongshore freshwater transport is two orders less than the alongshore volume transport. Out of the net volume transport, freshwater accounts for a maximum of 6.03 % during the southwest monsoon season followed by 4.85 % in the post-monsoon season. We observe an inverse relationship between alongshore freshwater and volume transport on the western coast and a direct relationship on the eastern coast. Seasonal variations between the cross-shore volume transport and its alongshore component also present such a contradiction along the western coast while displaying in-phase behaviour on the eastern coast. We also observed that meridional heat transport over AS is stronger than BoB. Both basins act as a heat source during the summer monsoon and heat sink during the winter. This high-resolution model set-up simulates all the important physical climatological patterns making it a useful tool in various physical as well as biogeochemical studies in this region.