Plio‐Pleistocene Evolution of the Benguela and Agulhas Currents

Abstract Reconstructing the evolution of the Benguela and Agulhas currents throughout the Plio‐Pleistocene and understanding the controls on productivity and sea surface temperature at their confluence is of wide interest. This period of Earth's history is marked by a multi‐million‐year global cooling trend that may be reflected in the local climates influenced by the two systems. We present alkenone based sea surface temperature (SST) and biological productivity (C 37 total/MAR) records at ODP Sites 1085 and 1087 located at the southern end of the modern Benguela Upwelling System (BUS) and under the influence of the Agulhas Current, respectively. At both sites we find SST evolution mirrors the evolution of other upwelling systems across the globe, while productivity was more susceptible to local precession‐driven climate change. The SST gradient between the two sites tracks the intensity and location of the currents and shows that the Agulhas leakage was present consistently at Site 1087 for the past 3.5 Ma. The gradient oscillates at orbital time scales with its strongest peaks coinciding with the glacial cycles. Through a comparison to other Benguela alkenone records we propose that prior to the Mid‐Pleistocene Transition (MPT) the BUS extended further south and slightly muted the presence of Agulhas leakage at Site 1087. Our results suggest that post‐MPT the southern boundary of the BUS shifted northward resulting in the increased influence of the Agulhas at Site 1087 and strengthened upwelling in the northern and central cells of the BUS.