Seasonal Variations of the Subsurface Thermal Structure in the Gulf of Guinea

Abstract

The subsurface thermal structure in the Gulf of Guinea is analyzed using the historical hydrographic data file. Of particular interest is the rapid vertical displacement of the thermal structure from the warm (March?May) season to the cold (July?August) season. This displacement field is trapped at the equator with vertical and meridional scales appropriate to a second or third mode baroclinic Kelvin wave. It has a maximum amplitude between 4°W and 10°W with a node near 2°E. South of 4°S no seasonal displacement of the thermocline underlies the seasonal variation in the sea surface temperature. Along the eastern boundary north of the equator to 3°E the displacement field vanishes. Thus the coastal upwelling associated with a vertical displacement tightly bound to the northern coast from 2°E to 10°W appears detached from the equatorial regime.