Comparative study of mixing and biological activity of the Benguela and Canary upwelling systems

We present a comparative study of the horizontal mixing properties, from satellite derived data of the surface velocity field, of the two eastern boundary Canary and Benguela upwelling systems, based on a Finite Size Lyapunov Exponents analysis. Each area can be subdivided into two subsystems attending to their mixing activity values. These coincide nicely with distinct biological signatures. When investigating links with chlorophyll as a proxy for biological activity in these two upwelling systems, results show that surface horizontal stirring and mixing vary inversely with chlorophyll standing stocks. Ekman-transport induced upwelling exhibits a positive correlation with chlorophyll. These two findings are complementary since spatial structure in plankton distributions results from both dynamics of the 3D turbulent medium and of the marine ecosystem.