The Decadal Twin Dipoles in the Southern Atlantic and Indian Oceans

Abstract

Analysis of sea surface temperature (SST) data robustly detects dipole-pattern decadal anomalies in the southern Atlantic and Indian Oceans (SAIOs) that co-occur like twins, termed the Atlantic-Indian Twin Dipoles (AITDs). The mechanisms governing the AITDs are investigated based on observational data sets, climate model simulations, and ocean model experiments. We show that the AITDs are coupled with alterations in subtropical highs that involve a variety of regional air-sea processes. Specifically, while cloud-controlled radiative heating plays key role in the Atlantic, wind-driven turbulent heat flux change is essential in the Indian Ocean. Wind-driven ocean dynamics are also important near the eastern boundaries of the SAIOs. Interdecadal Pacific Oscillation and Southern Annular Mode are conducive to the AITDs by modulating the subtropical highs. Our results highlight the trans-basin linkage between the SAIOs, providing implications for predicting the Southern Hemisphere climate and regional extremes.