Impact of river runoff on seasonal sea level, Kelvin waves, and East India Coastal Current in the Bay of Bengal : A numerical study using ROMS

Abstract

High riverine freshwater discharge makes the salinity distribution highly heterogeneous in the Bay of Bengal (BoB). This paper investigates the impact of freshwater discharge from ten major rivers on the seasonal sea surface variability and the coastal Kelvin wave characteristics in the BoB using the Regional Ocean Modeling System (ROMS). Two numerical experiments were conducted (i) with- and (ii) without-incorporating monthly climatology of river runoff into the model under the same forcing conditions. The model was forced by Comprehensive Ocean-Atmosphere DataSet (COADS) climatology for both the experiments. This study demonstrates that incorporation of river discharge into the model simulates a realistic picture of sea surface salinity, seasonal sea level variations, Kelvin wave activities, and equatorward flowing East India Coastal Current (EICC). The amplitude of the second downwelling Kelvin wave is increased most (greater than 4 cm at the Odisha coast and approximately 2 cm near the Chennai coast) due to river discharge. Apart from that, we also found that the equatorward EICC is strengthened and more organized when river runoff is considered. The volume transport by equatorward EICC becomes almost double when river runoff is included in the model in most of the region.