Collaborative Research: U.S. GEOTRACES North Atlantic Section: Analysis of 230Th, 232Th and 231Pa

在该项目中，四个合作实验室--伍兹霍尔海洋研究所、罗德岛大学、明尼苏达大学和拉蒙特-多尔蒂--将对美国地质调查局北大西洋段的230和231Pa溶解和微粒浓度进行测量，这两种同位素被认为是GEOTRACES计划成功的“关键”或关键。此外，他们还将测量232Th浓度，并提供颗粒成分的辅助分析。这项拟议的工作实现了美国地理追踪北大西洋实施计划中定义的科学目标。这些新的231Pa230Th和232Th数据有望在整个盆地范围内改进边界和大西洋内部之间的物质交换模型。该项目将使研究小组和海洋放射地球化学界能够检验关于环流、颗粒成分和颗粒通量区域变化的相对重要性的假设，这些变化影响到与颗粒有关的元素，包括碳、痕量金属和污染物在大陆架/斜坡区域和大西洋内陆盆地之间的重新分配。此外，获得新的231Pa和第230个水柱数据将允许检验一个关键假设：第230个水柱在北大西洋内大部分被去除，而就地生产的231pa中近一半与北大西洋深水一起出口。沉积231Pa230th比值已成为评价过去大西洋子午线翻转环流(AMOC)变化的主要指标。完成拟议的工作将表征颗粒组成对231Pa230Th分馏的重要性，从而限制将231Pa230Th用作AMOC运动学指标的潜在偏差。这些结果反过来将导致对AMOC变异性在过去气候变化中的作用进行更可靠的评估。更广泛的影响本提案中概述的假设和目标是国际GEOTRACES计划的核心，该计划的重点是海水中痕量元素和同位素的全球海洋分布。231pa和230th是地球科学计划中指定的关键参数，因为它们在所有部分的测量被认为是这一国际海洋科学计划成功的关键。拟议的研究将为研究生(LDEO)和博士后(UMinn)的研究经验提供新的机会，加强几个美国机构(LDEO、URI、UMinn、WHOI)之间的海洋科学互动，促进与国际地球物理研究中心(GEOTRACES)同事的合作，并为现有的面向教师和公众的科学教育计划做出贡献。

In this project four collaborating labs -- Woods Hole Oceanographic Institution, University of Rhode Island, University of Minnesota and Lamont-Doherty -- will undertake measurements on the US GEOTRACES North Atlantic section of the dissolved and particulate concentrations of 230Th and 231Pa, two isotopes designated as "key" or critical to the success of the GEOTRACES program. In addition, they will measure 232Th concentrations and provide supporting analyses of particle composition. The proposed work fulfills scientific objectives defined in the U.S. GEOTRACES North Atlantic Implementation Plan.These new 231Pa, 230Th and 232Th data are expected to lead to improved models of material exchange between the boundaries and interior Atlantic on a basin-wide scale. This project will permit the research team and the marine radiogeochemical community to test hypotheses regarding the relative importance of regional variations in circulation, particle composition, and particle flux that influence the redistribution of particle-associated elements, including carbon, trace metals and contaminants, between the continental shelf/slope regions and interior basins in the Atlantic. Furthermore, obtaining new water column 231Pa and 230Th data will allow testing of a key hypothesis: that 230Th is largely removed within the North Atlantic, whereas nearly half of the 231Pa produced in-situ is exported with North Atlantic Deep Water. Sedimentary 231Pa/230Th ratios have become the principal proxy used to evaluate past changes in Atlantic Meridional Overturning Circulation (AMOC). Completing the proposed work will characterize the importance of particle composition for 231Pa/230Th fractionation, and thereby constrain the potential bias in using 231Pa/230Th as a kinematic proxy for AMOC. These results, in turn, will lead to a more reliable assessment of the role of AMOC variability in past climate change.Broader Impacts The hypotheses and objectives outlined in this proposal are central to the International GEOTRACES program, whose focus is on the global-ocean distribution of trace elements and isotopes in seawater. 231Pa and 230Th are designated key parameters in the GEOTRACES Science Plan as their measurement on all sections is deemed to be critical to the success of this international ocean science program. The proposed research will provide new opportunities for graduate student (LDEO) and post doc (UMinn) research experience, enhance ocean science interactions between several US institutions (LDEO, URI, UMinn, WHOI), foster collaboration with international GEOTRACES colleagues, and contribute to existing science education programs designed for teachers and the public.