Collaborative Research: US GEOTRACES GP17-ANT: Iron redox cycling in the Amundsen Sea in the water column and shelf sediments

合作研究：US GEOTRACES GP17-ANT：阿蒙森海水柱和陆架沉积物中的铁氧化还原循环

• 批准号: 2124188
• 负责人: James Moffett
• 金额: $ 22.55万
• 依托单位: University of Southern California
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-06-01 至 2024-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2124188&HistoricalAwards=false
• 关键词: Collaborative; Research; US; GEOTRACES; GP17

The Amundsen Sea is one of the most rapidly changing areas along the Antarctic coast, with some of the fastest rates of glacial melting on the continent. There is great interest in the role of iron in controlling primary production and carbon and nutrient cycling within the Amundsen Sea, and it is probably an important source of iron to offshore waters of the Southern Ocean, which are rich in nutrients but iron limited. The work is part of the US GEOTRACES GP17-ANT cruise to the Amundsen Sea, a multi-investigator study of trace elements and isotope cycling. This work will study how iron is mobilized from sediments at the seafloor of the Amundsen basin. Such mobilization is influenced by two factors directly linked to climate change. Glacial melting increases ice-free areas known as polynyas, which experience large blooms of phytoplankton. Organic matter from these blooms eventually reaches the seafloor, creating low-oxygen conditions that accelerate iron transport into the overlying waters. Moreover, accelerated melting of glaciers will increase the transport of this iron to the surface via the buoyant “meltwater pump” along the glacier/ocean interface. These processes create feedbacks between climate and biological productivity that must be understood to develop models with a useful predictive capability. The broader impacts include partnering with University of Southern California Joint Educational Project and a PolarTREC teacher to create curriculum based on GEOTRACES Antarctic Expedition, which will be disseminated to 15 elementary school in Los Angeles area and develop online data exploration modules to encourage data-based learning in oceanography classes. This collaborative project will investigate iron redox cycling between sediments and water column of the Amundsen Sea and exchange with the Southern Ocean by determining iron (II) concentrations and redox kinetics in the water column as well as fluxes of iron and other elements from the seafloor to the water column from porewater measurements. A major objective of the US GEOTRACES GP17-ANT cruise is to study the exchange of iron between the Amundsen Sea and the Southern Ocean. The proposed work is essential to identifying the sources of iron and controls on source fluxes as well as internal transformations that will determine its fate. The data product from the project will be integrated with the results of other investigators in a synthesis effort after the cruise, including dissolved and particulate iron and related metals like manganese, as well as important tracers of sediment sources like radium isotopes. Iron(II) oxidizes very slowly in these cold waters, and kinetics will be combined with iron(II) bottom water concentrations and benthic fluxes to evaluate the importance of the slow oxidation kinetics on iron transport away from the benthic boundary layer. Benthic-derived iodine (denoted as “excess iodine”), will be utilized as an important semi-conservative tracer of iron inputs. Iodine is a useful comparative element because both iron and iodine accumulate in sediments under oxidizing conditions and are released under reducing conditions. Iodine is of interest in its own right because Antarctic Shelf waters are a massive source of reactive iodine species to the atmosphere.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.

阿蒙森海是南极海岸变化最快的地区之一，这里的冰川融化速度是该大陆最快的。人们对铁在控制阿蒙森海内初级生产以及碳和养分循环方面的作用非常感兴趣。它可能是南大洋近海水域的重要铁来源，该水域营养丰富，但铁含量有限。这项工作是前往阿蒙森海的美国 GEOTRACES GP17-ANT 巡航的一部分。这项工作将研究阿蒙森盆地海底沉积物中铁的​​流动受到与气候变化直接相关的两个因素的影响。作为冰间湖，浮游植物大量繁殖，最终到达海底，创造了低氧条件，加速了铁向上覆水域的输送。冰川将通过沿着冰川/海洋界面的浮力“融水泵”增加铁向地表的运输，这些过程在气候和生物生产力之间产生反馈，必须理解这些反馈才能开发具有更广泛影响的有用模型。包括与南加州大学联合教育项目和PolarTREC老师合作，​​创建基于GEOTRACES南极探险的课程，该课程将分发到洛杉矶地区的15所小学并在线开发数据探索模块，以鼓励海洋学课程中基于数据的学习，该合作项目将研究阿蒙森海沉积物和水体之间的铁氧化还原循环，并通过确定水体中的铁 (II) 浓度和氧化还原动力学与南大洋进行交换。以及通过孔隙水测量从海底到水柱的铁和其他元素的通量。美国 GEOTRACES GP17-ANT 巡航的一个主要目标是研究阿蒙森海和南大洋之间的铁交换。拟议的工作对于确定铁的来源和对源通量的控制以及将决定其命运的内部转换至关重要。该项目的数据产品将在巡航后与其他研究人员的综合工作的结果相结合，包括。溶解的铁和颗粒铁以及锰等相关金属，以及镭同位素等沉积物来源的重要示踪剂在这些冷水中氧化非常缓慢，动力学将与底水浓度和铁(II) 结合起来。底栖通量来评估缓慢氧化动力学对铁从底栖边界层迁移（称为“过量碘”）的重要性，将被用作铁输入的重要半保守示踪剂。一种有用的比较元素，因为铁和碘在氧化条件下积聚在沉积物中，并在还原条件下释放，因为南极洲碘本身就很有趣。陆架水域是大气中活性碘物质的大量来源。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。