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)

我们将重点研究上新世早期(~5-3.5 Ma)中美洲航道(CAS)收缩对南北大西洋的古海洋学效应。在约4.8-4 Ma期间，加勒比-太平洋地表水交换受到严重限制，达到了CAS关闭历史上的一个关键临界点。这导致赤道东太平洋温跃层变浅，并增加了大西洋经向翻转环流，将温暖和更多的咸水输送到北部高纬度。最近的模拟研究首次量化了这种构造引起的海洋变化。他们预测，北大西洋将明显变暖(高达7摄氏度)，南半球将显著降温(约2摄氏度)，这是由于北半球的“热海盗”。为了验证这一假设，在上新世早期，我们选择了在北大西洋和南大西洋对来自北半球的“热海盗”敏感的各种深海钻探计划和大洋钻探计划核心地点。我们将从表层和地下对浮游有孔虫进行δ18O和Mg/Ca的联合测量，并对海底有孔虫进行δ13C分析，以重建上新世早期上层水柱和深水水流的水文地貌。

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.