The nutrient characteristics of the Agulhas Bank

Abstract

The distribution of nutrients over the Agulhas Bank, based on an analysis of historical hydrographic data, demonstrates the existence of three distinct nutrient provinces. The western Agulhas Bank is largely driven by the Benguela system and derives its higher nutrient values from coastal upwelling; the shelf-edge of the eastern Agulhas Bank is under the influence of the Agulhas Current, which only contributes nutrient-poor water at the surface, whereas the major part of the eastern Agulhas Bank is under the influence of the far-eastern Agulhas Bank upwelling cell, which provides nutrient-rich bottom water. Seasonal changes in nutrient distributions over the whole Agulhas Bank are driven by strong vertical stratification in summer and the erosion of this stratification, by vertical mixing, in winter. During summer, nutrient concentrations in the surface layers are characteristic of Subtropical Surface Water; those in bottom water derive from Central Water.