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墨西哥湾流在上新世晚期/更新世早期中美洲航道（CAS）关闭的最后阶段的水文。我们建议使用ODP站点1006和1000在佛罗里达海峡和加勒比海中部的材料来测试的假设，有一个直接的联系CAS关闭，变暖和墨西哥湾流的盐度增加，并加强了大西洋经向翻转环流（AMOC），这导致了今天的南极环流和气候系统。建议首先根据底栖有孔虫的氧、碳稳定同位素组成建立1006站位（水深658 m）的年龄模型。这个关键地点的年龄模型，理想地位于墨西哥湾流的起点，将成为整个古海洋学研究工作的基础。通过测量未清理有孔虫Fe-Mn涂层中Nd的放射性同位素组成，追踪海平面变化引起的CAS闭合和重新开放的反复事件中中间水团混合和AMOC的强度。将从混合层和温跃层栖息的浮游有孔虫中测得的氧稳定同位素组成重建上层水柱水文。总之，这些千年分辨率记录将使我们深入了解AMOC强度的低纬度与高纬度强迫的重要性。这不仅将大大提高我们对过去海洋环流因重大构造变化而发生变化的机制的理解，而且还将提供与未来气候扰动有关的信息，因为墨西哥湾流海面盐度的变化影响了北大西洋环流的运作。

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.