Southwest African Coastal Upwelling System and Benguela Niños (SACUS)

Coastal countries of southwest Africa strongly depend upon their ocean: societal development, fisheries, and tourism face important changes associated with climate variability and global change. Global climate change will particularly impact eastern boundary upwelling regions by a combination of different stressors: increasing temperatures, acidification and deoxygenation. The main focus of the proposed study is the coastal upwelling off southern Africa. We will study its variability forced locally by the wind field and remotely by both wave propagation and water mass advection from the equatorial region, its interaction with the open ocean, and its response to climate change with its impact on rainfall of the region. Our collaborative project will address physical mechanisms of regional climate variability with profound impact on ocean biogeochemistry, hypoxia and marine ecosystems. We will use dedicated observing systems, experiments at sea as well as various modeling approaches in order to study intraseasonal to long term changes of the southwest African coastal upwelling system (SACUS) and the overlying atmosphere to finally improve climate predictions for southern Africa. The project aims at building and expanding local capacities required for the monitoring and prediction of the variability of the upwelling system and of the climate of surrounding land areas by cooperative research, joint summer/winter schools and scientist/technician exchange, by teaching of PhD students from southern African countries at German Universities, by research cruises open for southern African participants and by providing data and model output for analysis at southern African universities and institutes.



Schematic oceanic circulation of the southwest African coastal upwelling region in late austral summer superimposed on mean sea surface temperature (SST, color scale) and wind speed and direction (black arrows). Major features are Equatorial Undercurrent (EUC), South Equatorial Counter Current (SECC), South Equatorial Undercurrent (SEUC), Gabon Current (GC), Congo River (CR), Angola Current (AC), Angola Dome (AD), Angola Benguela front (ABF) and Benguela Current (BC). SST is plotted every degree from 18 to 30 °C. Maximum wind speed is 8 m/s in the south and minimum wind speed is 3 m/s just north of the ABF (from Rouault et al., 2007).