Collaborative Research: US GEOTRACES GP17-ANT: Tracing Inputs and Transport of Aluminum, Manganese, and Iron from the Amundsen Sea Sector of the Antarctic Continental Margin

国际GEOTRACES计划旨在了解微量元素及其同位素在海洋中的分布。作为这一努力的一部分，美国GEOTRACES计划将于2023年11月至2024年1月进行GP 17-ANT研究巡航，重点是南大洋阿蒙森海部分的微量元素和同位素分布。南大洋的生物生产通过生物吸收和相关的有机物质向海洋内部转移，在调节大气二氧化碳方面发挥着重要作用。这一海洋区域的大部分拥有浮游植物生长所需的丰富的主要营养物质（氮、磷和硅），但缺乏必需的微量营养素铁。这意味着浮游植物在夏季生长季节的生长是由铁调节的。其他微量元素，如锰和钴，在这方面也可能具有重要意义。因此，迫切需要将这些微量营养素微量元素的来源限制在南大洋表层沃茨。这些来源中最主要的是南极大陆边缘的沉积物、冰川和海冰。该项目旨在促进对南大洋阿蒙森海部分微量营养素铁和锰的来源和运输的了解，作为即将进行的GEOTRACES GP 17-ANT研究探险的一部分。阿蒙森海是南极大陆边缘的一个高产区，与南极一些融化最快的冰川冰架接壤，被认为是南极绕极流邻近缺铁表层沃茨溶解铁的重要来源。因此，这次考察期间对微量元素和同位素的测量将提供一个至关重要的基准，以评估未来几十年预计对这一海洋环境的重大变化的影响，例如与冰川融化增加有关的微量营养素铁的投入。该项目涉及两个美国实验室，并将支持一名研究生和一名本科生的研究。该项目还包括一名K-12 STEM教育专家的参与，他将开发针对中小学学生和科学教师的教育宣传材料。作为微量营养素的微量元素的浓度（溶解的铁和锰）和来自大陆尘埃和海底沉积物的输入物的示踪物在GP 17-ANT期间收集的海水样本中，将测量溶解铝和锰。 此外，还将进行船上实验，以评估悬浮颗粒和表层沉积物对表层海水中这些溶解的微量元素的贡献潜力。 这项工作，连同合作者对其他微量元素和同位素的测量，将评估南极大陆边缘这一部分微量营养素的来源、迁移和化学转化，从而评估这些微量营养素投入对未来环境变化的反应轨迹。溶解的铝、锰和铁的化学分析将在海上进行，接近实时，从而提供数据，为巡航采样策略提供信息，并指导其他调查人员的分析。该奖项反映了NSF的法定使命，并被认为值得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来支持。

The international GEOTRACES program seeks to understand the distributions of trace elements and their isotopes in the oceans. As part of this effort, the US GEOTRACES program will undertake the GP17-ANT research cruise in November 2023-January 2024, with a focus on the distribution of trace elements and isotopes in the Amundsen Sea sector of the Southern Ocean. Biological production in the Southern Ocean plays an important role in regulating atmospheric carbon dioxide via biological uptake and the associated transfer of organic matter into the ocean interior. Most of this ocean region has abundant major nutrients (nitrogen, phosphorous and silicon) required for phytoplankton growth, but is deficient in the essential micronutrient iron. This means that phytoplankton growth during the summer growing season is regulated by iron. Other trace elements, such as manganese and cobalt, may also hold importance in this context. Hence, there is a compelling need to constrain the sources of these micronutrient trace elements to Southern Ocean surface waters. Chief among these sources are sediments, glaciers and sea ice on the Antarctic continental margins. This project seeks to advance understanding of the sources and transport of the micronutrients iron and manganese in the Amundsen Sea sector of the Southern Ocean, as part of the upcoming GEOTRACES GP17-ANT research expedition. The Amundsen Sea is a highly productive section of the Antarctic continental margin that is bordered by some of Antarctica’s most rapidly melting glacial ice shelves, and is thought to provide an important source of dissolved iron to the adjacent, iron-deficient surface waters of the Antarctic Circumpolar Current. As such, the measurements of trace elements and isotopes during this expedition will provide a critically important benchmark to assess the impacts of major changes that are anticipated for this marine environment during the coming decades, such as inputs of the micronutrient iron that are associated with increased glacial melting. The project involves two US laboratories, and will support the research of a graduate student and an undergraduate student. The project also includes the participation of a K-12 STEM education specialist who will develop educational outreach materials targeting elementary and middle school students and science teachers.In this project, the concentrations of trace elements that serve as micronutrients (dissolved iron and manganese) and tracers of inputs from continental dust and seafloor sediments (dissolved aluminum and manganese) will be measured in seawater samples collected during GP17-ANT. In addition, shipboard experiments will be performed to assess the potential for suspended particles and surface sediments to contribute these dissolved trace elements to surface seawater. This work, together with measurements of other trace elements and isotopes made by collaborators, will assess the sources, transport and chemical transformations of micronutrients in this sector of the Antarctic continental margin, and hence the trajectories of these micronutrient inputs in response to future environmental changes. The chemical analyses of dissolved aluminum, manganese and iron will be performed at sea, in near real-time, thus providing data to inform the cruise sampling strategy and guide the analyses of other investigators.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.