North Atlantic Meridional Circulation during the Last Glacial Maximum:Density Structure and Pre-formed Nitrate: Phase I

大西洋的大尺度传送带状环流(大西洋子午线翻转环流，简称AMOC)通过其热通量及其对大气二氧化碳水平的影响而显著影响气候。许多证据表明，在上一个冰河时期，环流的结构有所不同，但这些重建是间接的。深海中的沉积孔隙水保存了古老的海水，并提供了更直接地记录上一次冰川盛期的AMOC与现在的不同的可能性。该项目由罗德岛大学的一个研究小组领导，将解决关于海洋环流和气候变化之间联系的这些基本问题。具体地说，资金支持一项为期一个月的研究探险，沿着波多黎各和新英格兰之间的横断面收集长长的沉积物岩芯。取心地点的深度从1公里到5公里以上。取心目标的选择将结合多波束条带测深、海底后向散射和线性调频海底地震数据。研究小组将分析船上回收的沉积物中孔隙水的成分(氯化物、溶解氧和硝酸盐浓度)，以检测上一次冰盛期期间深水化学的残留信号。这些测量将使研究人员能够直接测试冰川环流对气候的影响(通过北大西洋LGM深层和中间水中预先形成的硝酸盐含量)。考察队将包括几名研究生和本科生，提供有价值的培训活动和丰富的教育经验。

The large-scale conveyor-belt-like circulation of the Atlantic Ocean (the Atlantic Meridional Overturning Circulation, or AMOC) significantly affects climate via its heat flux and its impact on atmospheric carbon dioxide levels. A number of lines of evidence suggest that the structure of the circulation was different during the last ice age, however these reconstructions are indirect. Sedimentary pore waters in the deep sea preserve ancient seawater, and offer the possibility of more directly documenting how AMOC of the last glacial maximum differed from that of the present.This project, led by a team of researchers from the University of Rhode Island, will address these fundamental questions about the links between ocean circulation and climate change. Specifically, funding supports a month-long research expedition to collect long sediment cores along a transect between Puerto Rico and New England. Coring sites would range in depth from 1 to more than 5 km. Coring targets will be chosen with a combination of multibeam swath bathymetry, seafloor backscatter, and CHIRP sub-bottom seismic data. The team would analyze the composition (chloride, dissolved oxygen, and nitrate concentrations) of pore waters in the recovered sediments shipboard to detect the relict signal of deep water chemistry during the last glacial maximum. These measurements will allow the researchers to directly test the influence of glacial circulation on climate (via the pre-formed nitrate content of deep and intermediate water in the LGM North Atlantic). The expedition will include several graduate and undergraduate students, offering a valuable training activity and a strong educational experience.