Mixed Layer Salinity Balance in the Eastern Tropical Indian Ocean

Abstract

AbstractThe mixed layer salinity (MLS) balance in the eastern tropical Indian Ocean is investigated using observations and output from the Estimating the Circulation and Climate of the Ocean model. The results suggest that the annual mean MLS is determined by the balance between the surface freshwater forcing and ocean advection. The seasonal MLS variation in the eastern equatorial Indian Ocean is driven strongly by salt advection associated with the Wyrtki Jet in spring and fall despite weak seasonal cycles of precipitation and evaporation over this region. Off the south Java coast, the MLS is the lowest in summer, due to the advection of freshwater southward associated with the meridional currents, whereas it reaches the maximum in fall, due to strong evaporation. During the negative Indian Ocean Dipole (IOD), the anomalous eastward currents transported high‐salinity water to the east, generating positive MLS anomalies in the eastern tropical Indian Ocean. The regional evaporation minus precipitation anomalies were negative, which reduced the MLS. The MLS balance during the positive IOD is found to be nearly a mirror reflection of that during the negative IOD.