A decadal climate variation in the tropical Atlantic Ocean from thermodynamic air-sea interactions
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abstract
Rainfall variability in northeast South America and the Sahel region of Africa is profoundly influenced by the sea surface temperature (SST) of the tropical Atlantic Ocean. Of particular importance are relative changes in SST between the hemispheres on decadal timescales, a phenomenon often called the Atlantic SST dipole. Here we propose that the decadal variation in the tropical SST dipole may be attributed to an unstable thermodynamic ocean- atmosphere interaction between wind-induced heat fluxes and SST. Using coupled ocean-atmosphere models, we show that the coupled dipole mode has a typical oscillation period of about a decade. The notion that the Atlantic dipole-like SST variability may be related to an oscillatory coupled mode might assist attempts to predict decadal climate variability in the tropical Atlantic region.