Impact of Remote Equatorial Winds and Local Mesoscale Eddies on the Existence of “River in the Sea” Along the East Coast of India Inferred From Satellite SMAP

Abstract

AbstractThe Northern Bay of Bengal (NBOB) exhibits extreme salinity stratification caused by intense summer monsoon rainfall and associated river discharge. This accumulated fresh water plume in NBOB is believed to be transported along the East coast of India (ECI) by East India Coastal Current (EICC), known as River in the Sea (RIS). Though in situ sea Surface Salinity (SSS) measurements are sparse, the advancement of satellite monitoring system has provided a unique opportunity to unravel salient features of RIS. In the present study, in situ SSS at five selected regions around the Indian coast and open ocean are utilized to validate the Soil Moisture Active Passive (SMAP) (L3, v4.3) products. Further, this new SMAP data is used to examine year‐to‐year variability of RIS during 2015–2019 and the driving forces responsible for its existence. This SMAP SSS exhibited 1.52, 0.46, 0.38, 1.45 RMSD and 0.97, 0.82, 0.85, 0.86 correlation in NBOB1, NBOB2, Central BOB (CBOB) and Western BOB (WBOB), respectively with in situ measurements. This data also depicted the presence of “RIS” all along the ECI only during November in consistent with the magnitude of Kelvin wave induced EICC. The southward extension of RIS along the ECI is primarily based on the magnitude of remote equatorial wind induced forces. The mesoscale eddies in south‐western BOB (SWBOB) alters the shape of RIS and even inhibit its southward propagation completely.