Spatial and temporal variability of central Indian Ocean salinity fronts observed by SMOS

Abstract

Soil Moisture and Ocean Salinity (SMOS) Sea Surface Salinity (SSS) measurements, in addition to other data, are used to study the occurrence of salinity fronts in the poorly sampled Indian Ocean, which exhibits unique seasonal wind and current reversals. The strength and extent of salinity fronts are analyzed to understand their variabilities. Salinity fronts computed from SMOS compare favorably with those computed from Argo floats data, with SMOS showing higher magnitudes and more detailed structure of the fronts than Argo. Strong salinity fronts are observed along the equatorial region, with meridional migration of the fronts following the migration of the Intertropical Convergence Zone (ITCZ) and meridional ocean currents. Linked with these fronts are less saline subsurface waters that are sustained by the ITCZ-influenced precipitation and warm near-surface layer. During the 2010 negative Indian Ocean Dipole event, the equatorial front was influenced more by the increased SSS along the equator rather than precipitation. Additional factors, such as advective processes, aid the dynamics of fronts in the tropical Indian Ocean. Zonal currents advect less saline waters from the eastern Indian Ocean into the central Indian Ocean. Additionally the Indonesian Throughflow transports less saline waters to the region south of the equator, which eventually influence SSS front dynamics.