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沿着变化最快的地区之一，有一些大陆上冰川融化速度最快的地区。 铁在控制阿蒙森海初级生产和碳及营养物质循环中的作用引起了人们极大的兴趣，它可能是南大洋近海沃茨铁的重要来源，这些水域营养物质丰富，但铁有限。 这项工作是美国GEOTRACES GP 17-ANT阿蒙森海巡航的一部分，这是一项对微量元素和同位素循环的多研究者研究。 这项工作将研究铁是如何从阿蒙森盆地海底沉积物中移动的。 这种动员受到与气候变化直接相关的两个因素的影响。 冰川融化增加了被称为冰穴的无冰区，那里经历了浮游植物的大量繁殖。 这些水华中的有机物最终到达海底，形成低氧条件，加速铁运输到上覆的沃茨。 此外，冰川的加速融化将增加这些铁通过沿着冰川/海洋界面的浮力“融水泵”向表面的运输。 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，以开发具有有用预测能力的模型。 更广泛的影响包括与南加州大学联合教育项目和PolarTREC教师合作，以GEOTRACES南极考察为基础创建课程，该课程将分发给洛杉矶地区的15所小学，并开发在线数据探索模块，以鼓励在海洋学课程中进行基于数据的学习。这一合作项目将调查阿蒙森海沉积物和水柱之间的铁氧化还原循环以及与南大洋的交换，方法是确定水柱中的铁（II）浓度和氧化还原动力学，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 GP 17-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。 拟议的工作是必不可少的，以确定铁的来源和源通量的控制，以及将决定其命运的内部转换。 该项目的数据产品将与其他调查人员的结果结合起来，在航行后进行综合工作，包括溶解和颗粒铁及锰等相关金属，以及镭同位素等沉积物来源的重要示踪剂。 在这些寒冷的沃茨中，铁（II）的氧化非常缓慢，将把动力学与铁（II）的底层水浓度和底栖通量结合起来，以评价缓慢氧化动力学对铁从底栖边界层迁移的重要性。 底栖生物产生的碘（称为“过量碘”）将被用作铁输入的重要半保守示踪剂。 碘是一种有用的比较元素，因为铁和碘在氧化条件下积累在沉积物中，在还原条件下释放。碘本身就很重要，因为南极大陆架沃茨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知识价值和更广泛的影响审查标准进行评估，被认为值得支持。