Gulf Stream hydrography during the Late Pliocene/Early Pleistocene: low versus high latitude forcing of the Atlantic Meridional Overturning Circulation

该项目的目标是重建上新世晚期/更新世早期中美洲海道关闭最后阶段的墨西哥湾流水文。我们建议使用佛罗里达海峡和加勒比海中部的ODP站点1006和1000的材料来验证CAS关闭、墨西哥湾流变暖和盐度增加与大西洋经向翻转环流（AMOC）的主要加强之间存在直接联系的假设，AMOC导致了今天的大西洋环流和气候系统。首先基于底栖有孔虫氧碳稳定同位素组成建立1006站点（658 m水深）的年龄模型。这个关键地点的年龄模型，理想地定位在墨西哥湾流的起点，将成为一系列古海洋学研究的基础。通过测量有孔虫Fe-Mn包覆层中钕的放射性成因同位素组成，可以追踪海平面变化引起的CAS关闭和重新开放期间的中间水团混合和AMOC的强度。根据混合层和温跃层浮游有孔虫中氧的稳定同位素组成重建上层水柱的水文特征。总之，这些千年分辨率记录将使我们深入了解低纬度强迫和高纬度强迫对AMOC强度的重要性。这不仅将大大提高我们对过去主要构造变化驱动海洋环流变化机制的理解，而且还将提供与未来气候扰动有关的信息，这些扰动是墨西哥湾流海面盐度变化影响北大西洋环流功能的结果。

The goal of this project is to reconstruct the hydrography of the Gulf Stream during the final stages of the closure of the Central American Seaway (CAS) in the Late Pliocene/Early Pleistocene. We propose to use material from ODP Sites 1006 and 1000 in the Florida Straits and central Caribbean to test the hypothesis that there was a direct link between CAS closure, warming and increased salinity of the Gulf Stream, and a major strengthening of the Atlantic Meridional Overturning Circulation (AMOC), which led to the present day Atlanticcirculation and climate system. It is proposed to first establish an age model for Site 1006 (658 m water depth), based on the stable isotope composition of oxygen and carbon in benthic foraminifera. An age-model for this key site, positioned ideally at the start of the Gulf Stream, will be the basis for a whole range of paleoceanographic research efforts. The radiogenic isotope composition of neodymium (Nd) in the Fe-Mn coatings of uncleaned foraminifera will be measured to trace intermediate water mass mixing and the strengthof the AMOC during repeated episodes of CAS closure and re-opening caused by sea level changes. Upper water column hydrography will be reconstructed from the stable isotope composition of oxygen measured in mixed-layer and thermocline dwelling planktonic foraminifera. Together, these millennial resolution records will give us insight into the importance of low versus high latitude forcings of the strength of the AMOC. This willnot only significantly improve our understanding of the mechanisms driving past changes in ocean circulation in response to major tectonic changes but will also provide information relevant to future climate perturbations as a consequence of changing sea surface salinity of the Gulf Stream influencing the functioning of the North Atlantic circulation.