Abstract
Ice-age cooling of the central equatorial Atlantic Ocean reflects both equatorial upwelling and advection of cool water off the southern-hemisphere eastern boundary, but the largest contribution appears to be advection. This conclusion is based on planktonic foraminiferal assemblages that vary over the last ~300 ky in the tropical Atlantic and Pacific Oceans. Core-top maps of these assemblages reveal relationships to 1) the tropical-subtropical warm pool, 2) equatorial and coastal upwelling, and 3) eastern boundary current advection. The faunal indices are not sensitive to selective dissolution, as they do not correlate with measures of preservation such as calcite fragmentation or water depth. The sequence of changes going into a glacial interval is 1) initial cooling associated with equatorial upwelling driven by trade winds, followed by 2) amplified cooling by intensified meridional winds along the SE Atlantic margin which advected cool Benguela Current water to the central equatorial Atlantic. The Gulf of Guinea maintained its present cyclonic gyre circulation in glacial time, bounded by a front similar to the present Angola-Benguela Front. We prefer a model in which thermal gradients in the southern hemisphere drive changes in the South Equatorial Currents.
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Mix, A.C., Morey, A.E. (1996). Climate Feedback and Pleistocene Variations in the Atlantic South Equatorial Current. In: The South Atlantic. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-80353-6_26
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