Variability of the Seychelles–Chagos Thermocline Ridge Dynamics in Connection With ENSO and Indian Ocean Dipole

Abstract

Remote processes, such as El Nino- Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD), are primary drivers of the Seychelles–Chagos thermocline ridge (SCTR) interannual variability with respect to ocean temperature and salinity. Although salinity variability in this region is understudied, previous studies have separated out effects of El Nino and IOD on sea surface temperature (SST) anomalies and concluded SST changes due to IOD are primarily associated with the southward advection of warmer equatorial water. Likewise, SST changes due to El Nino are associated with the suppression of clouds over the Indian Ocean. Although ENSO is known to have a stronger impact on SST south of the SCTR (10°S–15°S), this letter finds that the ENSO has a stronger impact on sea surface salinity (SSS) in the SCTR. This letter further explores how the surface and subsurface salinity and temperature in SCTR varies throughout the year in response to ENSO and IOD separate and coevents using long-term Simple Ocean Data Assimilation (SODA) reanalysis records. Our SSS results from the SODA reanalysis are compared and found to be consistent with soil moisture active passive derived SSS observations for both a positive and negative IOD year.