Philander, S. G. H., 1979: Upwelling in the Gulf of Guinea. Journal of Marine Research, 37 (1), 23-33.

Abstract: Upwelling along the northern coast of the Gulf of Guinea occurs only between June and October even though the local winds are favorable for upwelling throughout the year and have no seasonal variability. Away from the coast, near the equator for example, the winds do vary seasonally and cause large scale oceanographic conditions in the Gulf of Guinea to change seasonally. One of these changes is an intensification of the eastward Guinea current north of the equator, during the summer. Because the current is in geostrophic balance it is associated with a thermocline that shoals in a northward direction, particularly so during the summer. Hence conditions along the northern coast are more favorable for upwelling during the summer than during the rest of the year. The cross-equatorial winds, that have a strong seasonal variation at the equator but not at the coast, are shown to contribute to the intensification of the Guinea current during the summer.