Effect of mesoscale eddies on the transport of low-salinity water from the Bay of Bengal into the Arabian Sea during winter

Abstract: The distribution of sea surface salinity (SSS) in the Arabian Sea (AS) and Bay of Bengal (BoB) is in contrast due to differences in air-sea freshwater fluxes and river runoff inputs.The monsoon-induced inter-basin water exchange plays an important role in regional salinity balance and atmosphere-ocean feedback in the North Indian Ocean. The satellite SSS dataset reveals that significant intraseasonal variability of SSS occurs in the region south of the Indian Peninsula with the strongest amplitude in winter. A case study in autumn-winter of 2016 showed that the Northeast Monsoon Current (NMC) and mesoscale eddies play a dominant role in the intraseasonal variability of the SSS in the region south of the Indian peninsula. In November, the East India Coastal Current (EICC) transports the low-salinity water southward to the region east of Sri Lanka. Meanwhile, a cyclonic eddy develops and propagates westward south of the NMC. Both NMC and the cyclonic eddy advects the low-salinity water westward to the region south of the Indian Peninsula. Then, an anticyclonic eddy generates in the north of the NMC. Thus, an eddy pair forms for more than one and a half months, which develops and propagates westward, transporting low-salinity water westward. The perturbation of mesoscale eddies and SSS gradient leads to the significant intraseasonal variability of SSS there.

Key words: Sea Surface Salinity; intraseasonal variability; mesoscale eddies; North Indian Ocean;