Collaborative Research: Coupling of physical and chemical processes in the shelf to basin transport of iron and iodine off Washington and Oregon

合作研究：华盛顿州和俄勒冈州附近铁和碘从陆架到盆地运输的物理和化学过程的耦合

• 批准号: 2023708
• 负责人: James Moffett
• 金额: $ 31.72万
• 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: 2020
• 资助国家: 美国
• 起止时间: 2020-09-01 至 2023-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2023708&HistoricalAwards=false
• 关键词: Collaborative; Research; Coupling; physical; chemical

The boundary between productive coastal waters and relatively non-productive offshore waters is not a simple function of distance from the coast, but is determined by a complex interplay between biology, chemistry, and ocean physics. This interplay is a fundamental property that controls the oceanic contribution to the food supply and the global carbon cycle. During summer months when waters are warmer with low oxygen, biological decomposition near the seafloor consumes available oxygen and releases iron from sediments into overlying seawater. In deeper parts of the ocean, canyons and other rugged surface features influence currents and create turbulence that rapidly moves iron from the shelf offshore. This iron in turn can enhance biological productivity miles away. This project will investigate (1) how decomposition processes on the continental shelf seafloor release elements like iron required for ocean life and (2) how ocean currents interact with the continental shelf and slope to move waters overlying the shelf offshore to enhance productivity. Based on model simulations from the California and Oregon coasts done over 20 years that show transport of iron via plumes from the shelf to the open ocean, scientists will collect and analyze samples for iron and iodine to prove the findings of the model. Iodine has been included in the study because it can track inputs from low oxygen sediments to the shelf. In addition, results from the study will be used to improve assumptions used in the current model. The project will support the research in whole or in part of four graduate students and several undergraduate students. The scientists are involved with High School student mentoring, through Project COOL (Chemical Oceanography Outside the Lab) and the Students on Ice Foundation. Scientists from the University of Southern California and the University of California, Los Angeles will study iron (Fe) and iodine (I) geochemistry along the Washington and Oregon Coasts, where high organic matter oxidation rates, low dissolved oxygen concentrations, and high sedimentary Fe fluxes on the continental shelf occur. This project hypothesizes that a shelf-to-basin shuttle controls the supply of Fe from the Fe-rich shelf into the interior of the North Pacific Ocean. Simulations of a Regional Oceanic Modeling System (ROMS) coupled with the Biogeochemical Elemental Cycling model (BEC) run between 2007-2017 showed that this coastline is a major source of Fe to the ocean basin, exhibiting both deep and shallow Fe plumes that arise from subsurface eddies generated by poleward undercurrents. Results from this model will be used to predict how the distribution of Fe evolves seasonally and guide sampling during two cruises in 2021 to the region. According to the ROMS-BEC model, the Fe inventory is highest in late summer, when bottom water oxygen is lowest, and the inventory is lowest in winter and early spring. Model-generated deep plumes resemble those reported off Namibia, Peru and the Gulf of Alaska. This work will sample depths up to 4500m and look for such plumes. Deep plumes are important in global Fe budgets and because they may outcrop in high latitude waters that are Fe limited. Iodine will also be measured because, like Fe, it accumulates at the sediment water interface and is released under reducing conditions. Plumes of iodine arising from shelf sediments will be used as a semi-conservative tracer for lateral Fe advection. The cruises will also assess the relative importance of direct inputs from rivers (especially the Columbia River) versus reducing sediments, since these inputs are decoupled seasonallyThis 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.

生产性沿海水域与相对非生产性的近海水之间的边界不是距离沿海距离的简单功能，而是由生物学，化学和海洋物理学之间的复杂相互作用确定的。 这种相互作用是控制海洋对食品供应和全球碳循环的贡献的基本财产。 在夏季，海水变暖，氧气低，海底附近的生物分解会消耗可用的氧气，并将铁从沉积物中释放到上覆的海水中。 在更深的海洋部分，峡谷和其他坚固的表面特征会影响电流并产生湍流，从而迅速从架子上移动铁。这种铁反过来可以增强几英里之外的生物生产力。该项目将调查（1）大陆架子海底释放元件（例如海洋生物所需的铁）上的分解过程以及（2）洋流如何与大陆架和坡度相互作用，以将架构上的水移动到海上陆上以提高生产率。 基于加利福尼亚和俄勒冈海岸的模型模拟，在20多年的时间里，科学家将通过李子从架子到开阔的海洋进行羽流的运输，从而收集并分析铁和碘的样品，以证明该模型的发现。 碘已包括在研究中，因为它可以跟踪从低氧沉积物到架子的输入。 此外，研究的结果将用于改善当前模型中使用的假设。 该项目将在四个研究生和几个本科生中全部或部分研究。 科学家通过Project Cool（实验室外的化学海洋学）和ICE基金会的学生参与了高中生指导。来自南加州大学和加利福尼亚大学洛杉矶分校的科学家将在华盛顿和俄勒冈州海岸研究铁（Fe）和碘（I）地球化学，那里发生了高有机物氧化速率，低溶解的氧气浓度以及大陆架上的高沉积性FE磁通量。该项目假设货架到巴辛航天飞机控制着富含铁的货架的铁的供应到北太平洋的内部。 区域海洋建模系统（ROMS）以及2007年至2017年之间运行的生物地球化学元素循环模型（BEC）的模拟表明，该海岸线是海盆的FE的主要来源，它表现出由极高的地下质量产生的深层和浅的Fe羽。 该模型的结果将用于预测FE的分布如何在2021年两次巡航期间向该地区进行季节性演变。 根据ROMS-BEC模型，FE库存在夏末最高，当时底部水氧最低，并且库存在冬季和早春最低。 模型生成的深羽类似于纳米比亚，秘鲁和阿拉斯加湾报道的羽毛。这项工作将采样高达4500m的深度，并寻找此类羽毛。深羽在全球FE预算中很重要，并且因为它们可能会在有限的高纬度水域中耗尽。 碘也将被测量，因为像FE一样，它在沉积物水界面上积聚并在还原条件下释放。 由架子沉积物引起的碘羽将用作侧向Fe的半保守示踪剂。 巡航还将评估河流（尤其是哥伦比亚河）直接投入的相对重要性与减少沉积物的相对重要性，因为这些投入是季节性脱口而出的，这反映了NSF的法定任务，并且被认为是值得通过基金会的知识分子优点和更广泛的影响审查标准来通过评估来通过评估来支持的。

项目成果

The role of seasonal hypoxia and benthic boundary layer exchange on iron redox cycling on the Oregon shelf

季节性缺氧和底栖边界层交换对俄勒冈陆架铁氧化还原循环的作用

• DOI: 10.1002/lno.12476
• 发表时间: 2023
• 期刊: Limnology and Oceanography
• 影响因子: 4.5
• 作者: Evans, Natalya;Floback, Alexis E.;Gaffney, Justin;Chace, Peter J.;Luna, Zachary;Knoery, Joël;Reimers, Clare E.;Moffett, James W.
• 通讯作者: Moffett, James W.