Annual cycle of sea surface temperature in the tropical Atlantic Ocean

Abstract

The strongest temporal variation of sea surface temperature (SST) in the Atlantic occurs at the annual period. In this paper we examine the causes of the annual cycle of SST through a series of modeling studies. In the subtropics we find that the annual cycle of SST follows the annual cycle of net shortwave radiation, except near the eastern boundary. Off northwest Africa, the annual cycle results from coastal upwelling induced by annual variations in alongshore winds. Off southwest Africa, the annual cycle results from a combination of coastal upwelling and effects caused by changes in the trade winds along the equator. In the band of latitudes between 3°N and 10°N, changes in latent heat loss due to the annual variation in wind speed is most important. The dominance of latent heat loss in this region explains why SST reaches a maximum in boreal fall even though the depth of the thermocline is at its annual minimum.