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.

热带印度洋地下温度的年代际变化具有很强的季节性，并具有明显的东西向偶极结构。年代际变率的季节特征在二十世纪的快速变暖时期表现为半年周期，然后在最近的间歇期转变为年度周期。半年周期与气候季节周期同相，因此加强了气候季节变化。而在最近的中断时间段，年度周期在上半年（下半）显示负（正）印度洋偶极子模式。地表温度年代际变化的这种变化与热带印度洋的地表风，特别是赤道纬向风密切相关。