RUI: Using opal and organic carbon as proxies for wind-driven upwelling during the onset and termination of the African Humid Period in a transect of African margin cores

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Marine and terrestrial records from northern Africa have greatly enhanced our understanding of both the causes and effects of climate change in the geologic past. Specifically, proxy records of changes in paleoproductivity yield information about upwelling strength, and therefore wind strength along the North African margin. Changes in wind strength, in turn, have been shown to correlate with changes in the relative aridity of the Sahel: periods of increased precipitation in the past were periods of weaker trade winds and decreased upwelling, and vice verse. Today the population of the Sahel region is highly vulnerable to changes in effective precipitation, making it all the more important to understand the connections between aridity, wind-strength, and climate change, and how abruptly changes can occur.This work, led by an early career faculty member at Macalester College in Minnesota, focuses on the environmental changes associated with the African Humid Period (AHP, 11,000 to 5,000 years before present), a time when northern Africa was characterized by a much wetter environment than it is today. Specifically, the work will assess the timing and abruptness of changes in upwelling associated with the onset and termination of the AHP across a 20-degree span of latitudes along the northwest African margin. The lead researcher will determine changes in upwelling intensity using the percentages of opal and organic carbon preserved in sediment cores, and combine these data with 230Th data from a separately funded project to calculate fluxes of each constituent. These efforts will provide an extraordinarily rich and detailed dataset of proxies related to wind strength, upwelling, and aridity in the Sahel region throughout the deglaciation and the Holocene. In terms of broader impact, this project will offer the opportunity for a number of undergraduates at a small mid-western liberal arts college to engage in ocean sciences research. Funding also supports collaboration between two early career scientists.