Understanding the origins of interannual thermocline variations in the tropical Indian Ocean

Based on the data analysis of the 1000 hPa wind, SST and SSH anomalies, it is revealed that the atmospheric variations associated with Indian Ocean Dipole (IOD, or referred as Indian Ocean Zonal Dipole Mode, IOZDM) consist of a pair of anticyclones closely north and south of the equator with accompanying intense equatorial easterly anomalies, while the atmospheric variations related to El Nino/Southern Oscillation (ENSO) include a strong anticyclone in the southeastern tropical Indian Ocean (TIO) at higher latitudes with strong along-shore wind anomalies near Java-Sumatra coast. The different atmospheric forcing patterns lead to the fact that oceanic thermocline variations associated with IOD/IOZDM are more closely confined to the region north of 10 degrees S, while ENSO-induced thermocline variations are dominant south of 10 degrees S.