The use of the salinity maximum of the equatorial undercurrent for estimating nutrient enrichment and primary production in the Gulf of Guinea

Abstract

In the Atlantic Ocean the summer equatorial nutrient enrichment seems due to the increased vertical mixing induced by the vertical shear between the westward South Equatorial Current and the eastward Equatorial Undercurrent. The high salinity core of the undercurrent is a good indicator of the intensity of vertical mixing: its salinity decreases as vertical mixing increases. There is a linear relationship between the salinity of the core and the nitrate enrichment of the surface layer, and at times when nitrate is limiting, the salinity maximum of the Equatorial Undercurrent can be used as a measure of the primary production.