Collaborative Research: US GEOTRACES GP17-ANT: Answering key questions in marine particle trace element biogeochemistry in the Amundsen Sea

国际GEOTRACES计划的目标是了解微量化学元素及其同位素在海洋中的分布。该项目将生成一个关于悬浮颗粒和表层沉积物样品的40种微量元素的数据集，这些样品是在前往西南极洲阿蒙森海的GEOTRACES GP 17-ANT巡航中收集的。阿蒙森海是整个南极洲单位面积上生产力最高的冰间湖，其生物碳吸收量比南大洋的平均水平高出十倍。在过去30年中，该区域已成为淡水输入增加的主要地点，因为南极洲西部融化最快的冰川向阿蒙森海提供了大量和越来越多的淡水。这一区域对全球海平面上升的主要作用已有充分的文献记载，但融水和相关化学成分加速增加对南极大陆架沃茨的地球化学、特别是对微量元素循环的影响尚未得到全面的调查。将对解决阿蒙森海海洋地球化学系统四个关键组成部分的假设进行测试，结果将与其他GP 17-ANT调查人员提出的补充努力密切配合。该项目将支持一名研究生和几名本科生实习生，重点是扩大STEM的参与。研究人员还将与既定项目合作，为初中和高中学生创造有意义的校外科学体验。该项目的目的是量化和解释覆盖阿蒙森海大陆架大片区域的约500个样本中微粒微量元素的分布，包括受五个主要冰架影响的沃茨，以及以100°W和135°W为界，南纬67°以南的邻近的铁有限南大洋沃茨。研究人员将使用大小分级的样品收集，总酸消化和弱酸浸出，以及成熟的质谱方法来确定浓度和探测颗粒微量元素的物理化学状态。该小组将利用新数据调查以下问题：1）浮游植物的作用，重点是阿蒙森海陆架上的主要类群棕囊藻和硅藻，在经历不同程度的铁压力时，在驱动上层水柱中的元素循环方面的作用; 2）“融水泵”，它从冰架空腔产生有力和富含颗粒的外流;（3）再悬浮沉积物的底部雾状层作为一个反应带，决定了沉积古记录的组成，也调制了沉积物-水边界的化学通量; 4）稀土元素（REE），该团队提出，这些冰川携带着关于地质多样性冰川流域中陆源颗粒来源的独特地球化学信息，并且还包括不稳定颗粒部分，其量值和元素间比率可以用作元素清除强度的相对指数，其可以应用于预测其它颗粒的最大清除区域，该奖项反映了NSF的法定使命，并被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准。

The goal of the international GEOTRACES program is to understand the distributions of trace chemical elements and their isotopes in the oceans. This project will generate a dataset of 40 trace elements on suspended particles and surface sediment samples collected on the GEOTRACES GP17-ANT cruise to the Amundsen Sea, West Antarctica. The Amundsen Sea hosts the most productive polynya per unit area in all of Antarctica, with biological carbon uptake ten times higher than the average for the Southern Ocean. Over the past 30 years, this region has become a primary locus of increased freshwater input, as the fastest melting glaciers in West Antarctica deliver huge and increasing volumes of freshwater to the Amundsen Sea. The major contribution of this region to global sea level rise is well documented, but the impact of accelerated additions of meltwater and associated chemical constituents on the biogeochemistry of the Antarctic shelf waters, and in particular on the cycling of trace elements, has not received comprehensive investigation. Hypotheses addressing four key components of the biogeochemical system in the Amundsen Sea will be tested, and results will closely mesh with complementary efforts proposed by other GP17-ANT investigators. The project will support a graduate student and several undergraduate interns, with a focus on broadening participation in STEM. The investigators will also work with established programs to create meaningful out-of-school science experiences for middle and high school students.The aim of the project is to quantify and interpret the distributions of particulate trace elements in approximately 500 samples covering a large swath of the Amundsen Sea shelf, including waters influenced by five major ice shelves, and in the adjacent iron-limited Southern Ocean waters bounded by 100°W and 135°W, and south of 67°S. The investigators will use size-fractionated sample collection, total acid digestion and weak acid leaching, and well-established mass spectrometric methods to determine concentrations and probe the physico-chemical state of the particulate trace elements. The team will use the new data to investigate the following issues: 1) the role of phytoplankton, with a focus on Phaeocystis and diatoms, dominant taxa on the Amundsen Sea shelf, in driving element cycling in the upper water column while experiencing variable degrees of iron stress; 2) the “meltwater pump” which generates vigorous and particle-rich outflow from ice shelf cavities; 3) the bottom nepheloid layer of resuspended sediments as a reaction zone that determines the composition of the sedimentary paleo-record and also modulates of chemical fluxes at the sediment-water boundary; and 4) the rare earth elements (REE), which the team proposes carry unique geochemical information about terrigenous particle provenance among the geologically diverse glacial drainage regions, and also includes a labile particulate fraction whose magnitude and inter-element ratios may serve as a relative index of element scavenging intensity that can be applied to predict regions of maximal scavenging for other particle-reactive elements.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.