Satellite Observations of Upwelling in the Gulf of Guinea

The classical case of favorable winds driving coastal upwelling does not adequately account for the upwelling observed along the northwestern Gulf of Guinea (GoG) coast, which is the area of focus in this letter. Herein, we used mainly satellite-derived data to examine the dynamics of upwelling in the study area. Upwelling indexes are derived from sea surface temperature (SST) and wind influences. Low SST, which is a characteristic of upwelling, is observed mainly along the entire coastal region from July to September. The relative contributions of local wind forcing are quantified; the wind-stress-driven Ekman transport was more important than the wind-stress-curl-driven Ekman pumping in affecting changes in SST. They both however do not entirely explain the upwelling that is observed along the entire coast. It is shown that winds in the western equatorial Atlantic force eastward propagating upwelling Kelvin waves that lead to lowering of sea level and SST along the northwestern GoG coast.