PLEISTOCENE PHOSPHORUS BURIAL IN THE AGULHAS CURRENT: LINKS TO REGIONAL AND GLOBAL CLIMATE VARIABILITY

The Agulhas Current is the strongest western boundary current in the Southern Hemisphere and is responsible for the transport of warm, saline waters down the Southeastern coast of Africa. The current has a profound impact on climate and weather patterns in the region, due to heat and moisture exchanges with the atmosphere. The nutrient load of the Agulhas Current is essential to primary productivity off the South African coast, but little is known about how it is influenced by regional and global climate through time. The focus of this research is to explore the connections between climate and nutrient burial through time, with an emphasis on phosphorus variability. Ocean sediment cores from the International Ocean Discovery Program (IODP) Expedition 361 were selected based on their locations within the Agulhas, from sites U1474 and U1479. Site U1474 is representative of the point where the Agulhas is considered fully constituted in the Natal Bight, and site U1479 is representative of the retroflection point of the current, where it sheds rings of warm water into the Atlantic Ocean. The core sections selected represent approximately the last 1 Ma, into the Late Pleistocene. Preliminary metal and phosphorus data show little correlation with known glacial-interglacial cycles and are indicative of global climate variation having a weak influence on overall nutrient burial in the Agulhas Current. Future research will involve sequential phosphorus extractions, to better understand the full picture of phosphorus burial in the current and how different components in the sediments may or may not have reacted to past climate fluctuations. The data will also be compared with continental records of aridity in Eastern Africa, to evaluate the relationship between continental climates and oceanic phosphorus burial in this region.