The Benguela Current, located off the west coast of southern Africa, is tied to a highly productive upwelling system1. Over the past 12 million years, the current has cooled, and upwelling has intensified2, 3, 4. These changes have been variously linked to atmospheric and oceanic changes associated with the glaciation of Antarctica and global cooling5, the closure of the Central American Seaway1, 6 or the further restriction of the Indonesian Seaway3. The upwelling intensification also occurred during a period of substantial uplift of the African continent7, 8. Here we use a coupled ocean-atmosphere general circulation model to test the effect of African uplift on Benguela upwelling. In our simulations, uplift in the East African Rift system and in southern and southwestern Africa induces an intensification of coastal low-level winds, which leads to increased oceanic upwelling of cool subsurface waters. We compare the effect of African uplift with the simulated impact of the Central American Seaway closure9, Indonesian Throughflow restriction10 and Antarctic glaciation**11, and find that African uplift has at least an equally strong influence as each of the three other factors. We therefore conclude that African uplift was an important factor in driving the cooling and strengthening of the Benguela Current and coastal upwelling during the late Miocene and Pliocene epochs.
The data was created by the CCSM3 model. The experiments that are considered are experiments run with 1) present.-day topography (HIGH) and 2) low African topography (LOW). The model results included are 100 year annual means. The ocean data comprise the upper 17 model layers. The atmospheric data was interpolated from model levels to 10 pressure levels. Included are model data from the ocean model POP and the atmosphere model CAM3.0 including the following variables: -atmospheric temperature -horizontal wind velocities -zonal and meridional wind stress -surface temperature -ocean temperature -vertical and horizontal oceanic velocity components -sensible and latent heat fluxes -radiative and heat fluxes
Supplement to: Jung, Gerlinde; Prange, Matthias; Schulz, Michael (2014): Uplift of Africa as a potential cause for Neogene intensification of the Benguela upwelling system. Nature Geoscience, 7(10), 741-747
