GEOTRACES Pacific Meridional Transect: Measurement of Beryllium-7 as a Tracer of Upper Ocean Processes

GEOTRACES 太平洋经线横断面：测量铍 7 作为上层海洋过程的示踪剂

• 批准号: 1736319
• 负责人: Mark Stephens
• 金额: $ 41.03万
• 依托单位: Florida International University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-09-01 至 2022-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1736319&HistoricalAwards=false
• 关键词: GEOTRACES; Pacific; Meridional; Transect; Measurement

The goal of the international GEOTRACES program is to understand the distributions of trace chemical elements and their isotopes in the oceans. One of the stated goals in the GEOTRACES Science Plan is to "create a unique opportunity for exploration and discovery by determining the distributions of novel trace elements and isotopes (TEIs) that have received little attention to date." This is a proposal to make measurements of one such species, the radioactive isotope beryllium-7 which will provide important biogeochemical rate information pertinent to the TEIs that will be measured during the 2018 U.S. GEOTRACES Pacific Meridional transect from Tahiti to Alaska. Many processes in the ocean cannot be directly observed and as such, tracers are used to provide important constraints on their rates and pathways. Beryllium-7 is a tracer that, because of its half-life (53.3 days), allows the study of processes which occur over time scales and depth scales that are otherwise difficult to obtain but which are critically important to studies of biological production, nutrient regeneration, and atmospheric deposition, to name a few. Advances in sampling and analytical techniques, coupled with a better understanding of the behavior of Be-7 in ocean biogeochemical cycles, present an opportunity to fully utilize this tracer.The proposed work has three main components:1) Measurements of Be-7 in the surface waters and in the lower atmosphere along the cruise track will provide estimates of the atmospheric input of relevant TEIs. The atmospheric input into the global ocean is an important budgetary component of numerous chemical species, yet is very difficult to constrain. The data generated in this work will be available to allow ground-truthing of models of aerosol deposition and atmospheric input of trace elements.2) Water column measurements of Be-7 provide a tracer of physical processes, such as mixing and upwelling, which redistribute biologically active species. Given quantitative knowledge of the circulation, mixing and ventilation of the water masses within which TEIs reside allows an assessment of the time- and space-integrated in situ biogeochemical behavior of these elements.3) The rate of oxygen utilization within the upper thermocline will be determined by water column measurements of Be-7 coupled with collected hydrographic data and observed oxygen distributions. The seasonal timescale afforded by Be-7 is ideal for estimating OUR within the shallow water just beneath the euphotic zone, where the most significant C remineralization is occurring. The project will support undergraduate student researchers at Florida International University, a leading minority serving institution. Lead investigator Kadko will participate in the Nippon Foundation - Partnership for Observation of the Global Oceans Center of Excellence (NF-POGO CofE), a unique platform which aims to provide world class training programs for students from emerging countries. Kadko will be offering an advanced topic course in chemical oceanography to these students during a stay at the Alfred Wegener Institute of Polar Studies. This outreach effort is consistent with the capacity building and educational goals of GEOTRACES as well as promoting international collaboration.

国际GEOTRACES计划的目标是了解微量化学元素及其同位素在海洋中的分布。GEOTRACES科学计划的一个既定目标是“通过确定迄今为止很少受到关注的新型微量元素和同位素（TEI）的分布，为探索和发现创造一个独特的机会。“这是一项测量此类物种的提议，放射性同位素铍-7将提供与TEI相关的重要地球化学速率信息，这些TEI将在2018年美国GEOTRACES太平洋子午线断面从塔希提岛到阿拉斯加进行测量。海洋中的许多过程无法直接观测，因此，示踪剂被用来对它们的速率和路径提供重要的限制。铍-7是一种示踪剂，由于其半衰期（53.3天），可以研究在时间尺度和深度尺度上发生的过程，这些过程很难获得，但对生物生产，营养再生和大气沉积的研究至关重要，仅举几例。随着取样和分析技术的进步，以及对Be-7在海洋地球化学循环中行为的深入了解，Be-7的利用成为可能。本文的工作主要包括三个方面：1）通过对沿沿着的表层沃茨和低层大气中Be-7的测量，估算相关TEI的大气输入量。进入全球海洋的大气输入是许多化学物种的重要预算组成部分，但很难限制。在这项工作中产生的数据将可用于允许地面实况模型的气溶胶沉积和大气输入的微量元素。2）水柱测量Be-7提供了一个物理过程的示踪剂，如混合和上升流，重新分配生物活性物种。考虑到TEI所在水体的循环、混合和通风的定量知识，可以评估这些元素的时间和空间综合原位地球化学行为。3）上部温跃层内的氧利用率将通过Be-7的水柱测量以及收集的水文数据和观察到的氧分布来确定。由Be-7提供的季节性时间尺度是理想的估计OUR内的浅水真光层，其中最显着的C化发生。该项目将支持佛罗里达国际大学的本科生研究人员，这是一所领先的少数民族服务机构。首席研究员Kadko将参加日本基金会-全球海洋观测卓越中心合作伙伴关系（NF-POGO），这是一个独特的平台，旨在为来自新兴国家的学生提供世界一流的培训计划。Kadko将在阿尔弗雷德·韦格纳极地研究所为这些学生提供化学海洋学的高级专题课程。这一外联工作符合GEOTRACES的能力建设和教育目标，也符合促进国际合作的目标。

项目成果

Quantifying Atmospheric Trace Element Deposition Over the Ocean on a Global Scale With Satellite Rainfall Products

• DOI: 10.1029/2019gl086357
• 发表时间: 2019-12
• 期刊: Geophysical Research Letters
• 影响因子: 5.2
• 作者: D. Kadko;W. Landing;C. Buck