Regime shift in the decadal variability of the Indian Ocean subsurface temperature

Abstract

The decadal variability in the subsurface temperature of the tropical Indian Ocean shows a strong seasonality and features a prominent east–west dipole structure. The seasonal characteristics of the decadal variability shows a semiannual cycle in the rapid warming period of the twentieth century and then shift to an annual cycle during the recent hiatus period. The semiannual cycle is in phase with the climatological seasonal cycle, and therefore strengthens the climatological seasonal variations. Whereas during the recent hiatus period, the annual cycle shows a negative (positive) Indian Ocean Dipole pattern in the first (second) half of the year. Such regime shift in the decadal variability of subsurface temperature is strongly correlated with that of the surface wind in the tropical Indian Ocean, especially the equatorial zonal wind. Our result suggests that an abrupt weakening in both summer and winter Indian monsoon at the beginning of this century is the major cause of the regime shift in decadal variability of surface winds. • Decadal variability in Indian Ocean subsurface temperature shows strong seasonality. • The decadal variability features a prominent east–west dipole structure. • The decadal variability experienced an abrupt regime shift around 2000. • Such regime shift is correlated with surface wind, especially equatorial zonal wind. • The regime shift in local wind is related to an abrupt weakening in Indian monsoon.