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

国际地学研究计划的目标是了解海洋中痕量化学元素及其同位素的分布情况。铁等许多痕量金属对生命至关重要，因此被认为是浮游植物生长的营养物质，微量金属循环对于影响铁有限的南大洋的碳循环尤其重要，因为在南大洋，来自各种不同外部来源的铁的断断续续的供应很重要。该项目的主要目标是作为GP17-ANT探险的一部分，在整个阿蒙森海和南极边缘周围地区的水柱站的横断面上测量铁的溶解浓度、大小分配和溶解同位素特征。该项目的次要目标是分析所有水柱样品中痕量金属锰、锌、铜、镉、镍和铅的浓度和尺寸分配，测量部分水柱样品中锌、镉、镍和铜的同位素比率，并测量气溶胶、淡水和颗粒物的铁同位素特征。该项目的观察结果将被纳入区域和全球生物地球化学模型，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，四名研究生和本科生，并将为其他PI提供超滤样本和数据作为服务。美国GEOTRACES GP17蚂蚁探险队计划于2023/2024年南半球夏季进行，旨在确定南极边缘阿蒙森海区(100-135°W)痕量元素及其同位素的分布和循环。邮轮将沿着阿蒙森海的传送带，对来自南极绕极洋流的水进行采样，进入大陆架，包括多特森和松岛冰架附近、生产力丰富的阿蒙森海波利尼亚(ASP)和外流水域。来自尘埃、冰架、融化的冰和沉积物的溶解Fe和其他TEI的间歇性增加推动了季节性初级生产力和碳在南极陆架和近海进入南大洋的输出。因此，季节性沿海多年生植物，如高生产力的多年生草本植物，是全球碳循环的关键杠杆。然而，在这些地区对TEI的实地观测仍然很少，在海洋生物地球化学模型中很难捕捉到生物地球化学循环过程。研究人员将使用他们的联合分析工具箱，与其他资助小组的诊断化学示踪剂和区域模型合作，解决四个主要目标：1)不同来源在向ASP供应铁和其他TEI方面的相对重要性？2)这种铁的物理化学形态是什么，以及它的运输潜力？3)ASP中的生物吸收、清除和再生如何影响TEI的分布、化学计量、和营养限制？4)离岸运输到ACC和南大洋的TEI的流量和签名是什么？该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

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.