A regional hydrodynamic model of upwelling in the Southern Benguela.

The Benguela upwelling system, off the southwest coast of southern Africa, is productive but also highly dispersive. Sardines and anchovies have adapted their reproductive strategy by spawning on the Agulhas Bank, away from the upwelling region. Transport from the spawning grounds to the nursery area is believed to be one of the main environmental processes that control recruitment. To understand the transport processes along the southwest African coast better, we set up an eddy-resolving, primitive equation model of the regional oceanic circulation. The model domain covers the shelves and oceanic plains from 40°S to 28°S and from 10° E to 24°E. To obtain statistically meaningful solutions, long simulations (more than 10 years) were conducted. The high-order accuracy of the model schemes and grid resolution allow the development of plumes, filaments and eddies, which are characteristic features of upwelling systems. While only large-scale and seasonal variations are forced, this energetic mesoscale activity induces an important variability. This intrinsic variability could limit the predictability of the transport processes and fish recruitment in the Benguela Current.