Decadal variations in the subtropical cells and equatorial pacific SST

Abstract

A mechanism for generating decadal sea surface temperature (SST) variability in the equatorial Pacific is investigated using an ocean general circulation model forced by observed wind stress. Equatorial SST variability is governed by different ocean dynamics on interannual and decadal time scales. At interannual time scales, equatorial SST anomalies are mainly driven by equatorial winds. At decadal time scales, on the other hand, they are forced both by equatorial winds and by off‐equatorial winds in the tropics, while the contribution from midlatitude winds poleward of 25° is negligible. Trade‐wind variations in the off‐equatorial tropics force equatorial SST variability by spinning up and down the subtropical cells that transport cold water into the equatorial upwelling zone. Equatorial SST anomalies induced by this mechanism lag behind the response to local equatorial winds by about two years.