| In the Gulf of Guinea (4 degree W), the equatorial upwelling, generated by the divergence of surface current meridional components, appears only during the boreal (northern) summer (June to September) south of the Equator and exhibits a considerable enrichment in nitrate and phosphate at the sea surface. At the Equator below the surface, there is also a seasonal nutrient enrichment due to vertical mixing or/and vertical motion of the thermocline. Zonal advection from the African coastal zone, often advanced to explain the equatorial fertility, does not completely agree with the observed surface distributions of nitrate. In the western equatorial Atlantic (35 degree W), the seasonal surface nutrient enrichment does not appear in July and the surface layer... |
