Collaborative Research: US GEOTRACES GP17-ANT: Dissolved concentrations, isotopes, and colloids of the bioactive trace metals

国际GEOTRACES计划的目标是了解海洋中微量化学元素及其同位素（TEI）的分布。许多微量金属，如铁是生命所必需的，因此被认为是浮游植物生长的营养物质，微量金属循环对影响铁有限的南大洋的碳循环特别重要，其中来自一系列不同外部来源的铁的间歇性供应很重要。该项目的主要目标是测量溶解的浓度，大小分区，溶解的铁同位素的签名在整个阿蒙森海和周围地区的南极边缘，作为GP 17-ANT远征的一部分，一个横断面的水柱站。该项目的第二个目标是分析所有水柱样本中微量金属锰、锌、铜、镉、镍和铅的浓度和粒度分布，测量水柱样本子集中锌、镉、镍和铜的同位素比，并测量气溶胶、孔隙水和颗粒的Fe同位素特征。该项目的观测结果将纳入区域和全球海洋地球化学模型，以评估阿蒙森海内的TEI循环及其对更广泛的南大洋的影响。该项目跨越三个机构，四名研究生，本科生，并将提供超滤样品和数据给其他PI作为服务。美国GEOTRACES GP 17 ANT探险，计划于2023/2024年南夏，旨在确定南极边缘阿蒙森海区（100-135°W）微量元素及其同位素的分布和循环。此次巡航将沿着阿蒙森海的“传送带”，对来自南极绕极流的沃茨进行采样，进入大陆架，包括Dotson和松岛冰架附近、多产的阿蒙森海Polynya（ASP）和流出的沃茨。来自尘埃、冰架、融冰和沉积物的溶解铁和其他TEI的阶段性增加驱动了南极大陆架和近海南大洋的季节性初级生产力和碳输出。因此，季节性的沿海冰棚，如高产的ASP，是全球碳循环的关键杠杆。然而，在这些地区的TEIs的现场观测仍然很少，海洋地球化学循环过程中捕获的海洋地球化学模型。研究人员将使用他们的组合分析工具箱，与诊断化学示踪剂和其他资助团体的区域模型合作，以解决四个主要目标：1）在向ASP提供Fe和其他TEI时，不同来源的相对重要性是什么？2)这种铁的物理化学形态是什么，它的运输潜力是什么？3)ASP中的生物吸收、清除和再生如何影响TEI分布、化学计量和营养限制？4)什么是TEI的通量和签名离岸到ACC和南大洋？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知识价值和更广泛的影响审查标准进行评估的支持。

The goal of the international GEOTRACES program is to understand the distributions of trace chemical elements and their isotopes (TEIs) in the oceans. Many trace metals such as iron are essential for life and thus considered nutrients for phytoplankton growth, with trace metal cycling being especially important for influencing carbon cycling in the iron-limited Southern Ocean, where episodic supply of iron from a range of different external sources is important. The primary goal of this project is to measure the dissolved concentrations, size partitioning, and dissolved isotope signature of Fe on a transect of water-column stations throughout the Amundsen Sea and surrounding region of the Antarctic Margin, as part of the GP17-ANT Expedition. The secondary goal of this project is to analyze the concentrations and size partitioning of the trace metals manganese, zinc, copper, cadmium, nickel, and lead in all water-column samples, measure the isotope ratios of zinc, cadmium, nickel, and copper in a subset of water column samples, and measure the Fe isotopic signature of aerosols, porewaters, and particles. Observations from this project will be incorporated into regional and global biogeochemistry models to assess TEI cycling within the Amundsen Sea and implications for the wider Southern Ocean. This project spans three institutions, four graduate students, undergraduate students, and will provide ultrafiltered samples and data to other PIs as service.The US GEOTRACES GP17 ANT expedition, planned for austral summer 2023/2024 aims to determine the distribution and cycling of trace elements and their isotopes in the Amundsen Sea Sector (100-135°W) of the Antarctic Margin. The cruise will follow the Amundsen Sea ‘conveyor belt’ by sampling waters coming from the Antarctic Circumpolar Current onto the continental shelf, including near the Dotson and Pine Island ice shelves, the productive Amundsen Sea Polynya (ASP), and outflowing waters. Episodic addition of dissolved Fe and other TEIs from dust, ice-shelves, melting ice, and sediments drive seasonal primary productivity and carbon export over the Antarctic shelf and offshore into Southern Ocean. Seasonal coastal polynyas such as the highly productive ASP thus act as key levers on global carbon cycling. However, field observations of TEIs in such regions remain scarce, and biogeochemical cycling processes are poorly captured in models of ocean biogeochemistry. The investigators will use their combined analytical toolbox, in collaboration with the diagnostic chemical tracers and regional models of other funded groups to address four main objectives: 1) What is the relative importance of different sources in supplying Fe and other TEIs to the ASP? 2) What is the physiochemical speciation of this Fe, and its potential for transport? 3) How do biological uptake, scavenging and regeneration in the ASP influence TEI distributions, stoichiometry, and nutrient limitation? 4) What is the flux and signature of TEIs transported offshore to the ACC and Southern Ocean?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.