Deciphering global cooling of the mid-latitude oceans and its implication for the ocean circulation and climate during the early Pliocene (~5-3.5 Ma)

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We will focus our studies on the paleoceanographic effects of the constriction of the Central American Seaway (CAS) on the North and South Atlantic Ocean during the early Pliocene epoch (~5-3.5 Ma). During ~4.8-4 Ma, a critical threshold in the closing history of the CAS was reached with a significantly restricted Caribbean-Pacific surface water exchange. This caused a thermocline shoaling in the equatorial east Pacific and increased the Atlantic Meridional Overturning Circulation transporting warm and more saline waters towards high northern latitudes. For the first time recent simulation studies quantified this tectonic induced oceanographic changes. They predicted a distinct warming of the North Atlantic (up to 7°C) and a pronounced cooling of the Southern Hemisphere (~2°C) through “heat piracy” of the Northern Hemisphere. To test this hypothesis of an interhemispheric seesaw during the early Pliocene we selected various Deep-Sea Drilling Project (DSDP) and Ocean Drilling Program (ODP) core sites in the North and South Atlantic Ocean sensitive to “heat piracy” from the Northern Hemisphere. We will conduct combined δ18O and Mg/Ca measurements of planktic foraminifera from surface and subsurface levels and δ13C analyses from benthic foraminifera to reconstruct the hydrography of the upper water column and deep water currents during the early Pliocene.