PLIO-PLEISTOCENE BIOMARKER RECONSTRUCTIONS AT THE AGULHAS PLATEAU AND IMPLICATIONS FOR TERRESTRIAL AFRICAN CLIMATE

The Agulhas Current is the strongest boundary jet current of the southern Indian Ocean, playing an important role in global and regional climates while promoting exchange of heat to atmospheric moisture. Movement from the Indian Ocean to the Atlantic Ocean of some portion of the warm, saline Agulhas Current occurs through Agulhas leakage south of Africa. Restrictions in this Indian-Atlantic Ocean gateway region are thought to occur through latitudinal shifts in ocean fronts, moderating the dynamics of water flow. The Agulhas Plateau is located in the area affected by latitudinal migrations of these ocean fronts and thus provides an important region to study how changes in front movements may have contributed to changes in the Atlantic Meridional Overturning Circulation and southern Indian Ocean climate variability. Using sediments recovered at IODP site 1475 on the Agulhas Plateau (Expedition 361), we present new organic geochemical records of water temperature ( and TEX₈₆), marine primary productivity (chlorins and alkenones), and sea surface salinity (δD_alkenones), across the Plio-Pleistocene, from 3 Ma – 300 ka. Our multi-proxy reconstructions highlight glacial-interglacial periodicity, showing more abrupt and higher amplitude cycles after the MPT, suggesting changes in Agulhas Current strength and leakage variability. We see offsets between the two water temperature proxies during glacials and interglacials, which may suggest varying contributions of regional water masses at the Agulhas Plateau. We discuss the potential influence of oceanographic variability at the Agulhas Plateau on African terrestrial climates.