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.

阿蒙森海是南极沿岸最快变化的地区之一，持续的冰川融化速率最快。铁在控制阿蒙森海内的碳和碳循环中的角色引起了极大的兴趣，它可能是南大洋近海水域的重要来源，这些水是富含营养但有限的富含养分但有限的。这项工作是美国地理位置GP17-ant巡航到Amundsen Sea的一部分，Amundsen Sea是一项对痕量元素和同位素循环的多次评估研究。这项工作将研究如何从阿蒙森盆地海底的沉积物中动员铁。这种动员受到与气候变化直接相关的两个因素的影响。冰川融化增加了无冰区域，称为Polynyas，它会经历浮游植物的大血液。这些血液中的有机物最终到达了海底，从而产生了低氧条件，使铁的运输加速到上覆的水域。此外，冰川的加速融化将通过沿冰川/海洋界面的浮力“融水泵”来增加该铁向表面的运输。这些过程在气候和生物生产力之间产生了反馈，必须理解这些过程以开发具有有用的预测能力的模型。更广泛的影响包括与南加州大学联合教育项目和Polartrec老师合作，​​以基于Geotraces南极探险来创建课程，该课程将被传播到洛杉矶地区的15个小学，并开发在线数据勘探模块，以鼓励基于数据的学习水平学课程。该协作项目将通过确定水柱中的铁（II）浓度和氧化还原动力学以及铁和其他元素从孔隙水测量中确定铁和铁的通量以及从海底到水柱的铁和其他元素，从而研究阿蒙森海沉积物和水柱之间的铁氧化还原循环。美国地理位置GP17-Ant Cruise的一个主要目标是研究Amundsen海与南大洋之间的铁交换。拟议的工作对于确定铁和控制源的控制以及将决定其命运的内部变换至关重要。该项目的数据产品将与其他研究人员的结果集成在巡航之后的合成工作中，包括溶解和特定的铁和相关金属（如锰）以及诸如半径同位素等沉积物源的重要示踪剂。铁（II）在这些冷水中非常缓慢地氧化，动力学将与铁（II）底部水浓度和底栖通量结合，以评估慢速氧化动力学对铁转运远离底栖边界层的重要性。底栖衍生的碘（称为“过量碘”）将被用作铁输入的重要半保守示踪剂。碘是一个有用的比较元素，因为在氧化条件下铁和碘都在沉积物中积聚，并在还原条件下释放。碘本身就是感兴趣的，因为南极的架子水域是大气中反应性碘物种的巨大来源。该奖项反映了NSF的法定任务，并通过使用基金会的智力优点和更广泛的影响来审查标准，通过评估来诚实地支持支持。