Collaborative Research: US GEOTRACES GP17-ANT: Constraining the Neodymium (Nd) Isotope and Rare Earth Element Cycles near the Amundsen Sea Continental Margin

海水中的微量元素与气候和人类社会相关，因为它们可以作为海洋生态系统的必需营养素或各种海洋过程的有用化学指纹。国际GEOTRACES计划旨在确定控制全球海洋中关键微量元素及其同位素分布的过程和量化通量，并确定这些分布如何对不断变化的环境作出反应。钕（Nd）同位素和稀土元素（ree）是这些关键元素的显著例子，因为它们在追踪过去和现在的海洋混合以及微量元素到海洋的来源方面具有实用价值。在本项目中，研究人员将参加美国GEOTRACES科学考察队GP17-ANT前往南极大陆边缘的阿蒙森海地区，并分析此次考察队采集的样品中的Nd同位素比率和REE浓度。海洋的这一区域具有特别重要的意义，因为它在过去几十年中经历了迅速的环境变化，包括整个南极周围冰架的融化速度最快。该项目的测量结果将促进我们对导致当地冰架融化的海洋过程的理解，也将为维持该地区上层海洋异常高的生物生产力的营养来源提供新的线索。该项目将有助于支持不同职业水平的南极研究、教学和推广工作的发展。外展活动将提供充分的机会，让K-12学生、来自代表性不足群体的学生和公众在正式和非正式的环境中讨论海洋科学和南极环境。美国GEOTRACES GP17-ANT邮轮到阿蒙森海提供了一个特殊的机会来研究微量元素的海洋生物地球化学循环及其同位素，这些元素与南极大陆边缘、快速冰架融化、多产的多冰湖以及特别容易受到持续气候变化影响的地区的水团过程有关。本项目将研究该地区海水中钕同位素和稀土分布的来源和过程。具体的来源和过程将被研究，并在可能的情况下量化，包括：(1)水团运输和混合；(2)边坡交换；(3)气溶胶;(4)海冰；(5)冰下融水；(6)沉积物与陆架交换；(7)粒子相互作用。我们将对一系列精心挑选的海水、颗粒、沉积物、气溶胶和海冰样本进行Nd同位素和REE浓度分析，以约束这些不同控制因素的性质和相对重要性，从而全面了解南极边缘Nd同位素和REE循环。这些结果不仅将为了解该地区所有其他微量元素生物地球化学循环直接相关的水团过程和岩石成因输入提供关键约束，而且还将提高Nd同位素和REE模式作为现代和古代海洋研究的有用示踪剂的实用性。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Trace elements in seawater are relevant to climate and human society, because they can act as essential nutrients for marine ecosystems or useful chemical fingerprints for a variety of oceanographic processes. The international GEOTRACES program is intended to identify processes and quantify fluxes that control the distributions of key trace elements and their isotopes in the global ocean, and to establish how these distributions could respond to changing environments. Neodymium (Nd) isotopes and rare earth elements (REEs) are notable examples of such key elements because of their utility in tracing past and present ocean mixing and sources of trace elements to the ocean. In this project, investigators will participate in the US GEOTRACES science expedition GP17-ANT to the Amundsen Sea sector of the Antarctic continental margin, and analyze Nd isotope ratios and REE concentrations in samples collected from this expedition. This region of the ocean is of particular significance because it is experiencing rapid environmental changes in the past few decades, including the fastest melting of ice shelves around the entire Antarctic. Measurements from this project will advance our understanding of ocean processes that cause melting of local ice shelves, and also will shed new light on nutrient sources that sustain the unusually high biological productivity in the upper ocean of this region. This project will contribute to support the development of diverse involvement in Antarctic research, teaching and outreach efforts across career levels. The outreach activities will provide ample opportunities to engage K-12 students, students from underrepresented groups, and general public in discussions of ocean sciences and the Antarctic environment in both formal and informal settings.The US GEOTRACES GP17-ANT cruise to the Amundsen Sea provides an exceptional opportunity to study marine biogeochemical cycles of trace elements and their isotopes in relation to the Antarctic continental margin, fast iceshelf melting, productive polynyas, and water mass processes in an area especially susceptible to ongoing climate change. This project will study sources and processes that regulate the distribution of Nd isotopes and REEs in seawater in this region. Specific sources and processes that will be studied, and quantified where possible, include: (1) water mass transport and mixing; (2) slope exchange; (3) aerosols; (4) sea ice; (5) subglacial meltwaters; (6) sediments and shelf exchange; (7) particle interactions. Nd isotope and REE concentration analyses will be conducted on a suite of carefully selected seawater, particulate, sediment, aerosol, and sea ice samples to constrain the nature and relative significance of these different controls, providing a comprehensive understanding of Nd isotope and REE cycling in the Antarctic margin. These results will not only provide critical constraints on water mass processes and lithogenic inputs that are directly relevant to understand all other trace element biogeochemical cycles in this region, but also improve the utility of Nd isotopes and REE patterns as useful tracers for studies of modern and ancient oceans.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.