Observed interannual variability of zonal currents in the equatorial Indian Ocean thermocline and their relation to Indian Ocean Dipole

Interannual variability of zonal currents in the eastern equatorial Indian Ocean thermocline is significantly correlated with sea surface temperature (SST) in the eastern pole of the Indian Ocean Dipole (IOD). This relationship is more significant than for zonal currents and the Dipole Mode Index, the latter of which measures zonal SST anomaly gradient. The variability of zonal currents in the thermocline is consistent with the variations of eastward pressure gradient force in the thermocline and the equatorward geostrophic thermocline flows associated with the shallow meridional overturning circulations in the eastern tropical Indian Ocean. Our analysis suggests a positive feedback between zonal currents in the thermocline and SST in the eastern pole of IOD. The combination of equatorial wind and off-equatorial wind stress curls associated with SST anomalies in the eastern pole of the IOD drives interannual variability in equatorial zonal thermocline flows and its covariability with the shallow meridional overturning cells.