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有关，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应对不断变化的环境。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和海洋微量元素来源方面具有实用性。在该项目中，研究人员将参加美国GEOTRACES科学考察队GP 17-ANT到南极大陆边缘的阿蒙森海部分，并分析从这次考察中收集的样品中的Nd同位素比值和REE浓度。这一海洋区域具有特别重要的意义，因为在过去几十年里，它正在经历快速的环境变化，包括整个南极周围冰架融化最快。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，并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发展不同职业层次的南极研究、教学和外联工作。外联活动将为K-12学生、代表性不足群体的学生和公众提供充分的机会，在正式和非正式场合讨论海洋科学和南极环境。美国GEOTRACES GP 17-ANT号阿蒙森海巡航提供了一个难得的机会，研究与南极大陆边缘有关的微量元素及其同位素的海洋生物地球化学循环，在一个特别容易受到持续气候变化影响的地区，快速的冰盖融化、多产的冰穴和水团过程。该项目将研究该地区海水中Nd同位素和稀土元素分布的来源和调节过程。将研究并尽可能量化的具体来源和过程包括：（1）水团迁移和混合;（2）斜坡交换;（3）气溶胶;（4）海冰;（5）冰下融水;（6）沉积物和大陆架交换;（7）颗粒相互作用。Nd同位素和稀土元素浓度分析将进行一套精心挑选的海水，颗粒，沉积物，气溶胶和海冰样品，以限制这些不同的控制的性质和相对意义，提供了一个全面的了解Nd同位素和稀土元素循环在南极边缘。这些结果不仅将提供对水团过程和成岩输入的关键约束，这与了解该地区所有其他微量元素的地球化学循环直接相关，该奖项反映了NSF的法定使命，并通过使用基金会的知识产权进行评估，被认为值得支持。优点和更广泛的影响审查标准。

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.