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 计划的目标是了解海洋中微量化学元素及其同位素的分布。 GEOTRACES 科学计划的既定目标之一是“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，为探索和发现创造独特的机会。”这是一项对其中一种物质（放射性同位素铍-7）进行测量的提案，它将提供与 TEI 相关的重要生物地球化学速率信息，TEI 将在 2018 年美国 GEOTRACES 太平洋经线横断面（从塔希提岛到阿拉斯加）期间进行测量。海洋中的许多过程无法直接观察，因此示踪剂用于对其速率和路径提供重要限制。 Beryllium-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，但对于生物生产、营养物质的研究至关重要再生和大气沉降等等。采样和分析技术的进步，加上对海洋生物地球化学循环中 Be-7 行为的更好理解，为充分利用这种示踪剂提供了机会。拟议的工作包括三个主要组成部分：1）测量 Be-7 在海洋生物地球化学循环中的变化。沿巡航轨道的地表水和低层大气将提供相关 TEI 的大气输入的估计。全球海洋的大气输入是众多化学物质的重要预算组成部分，但很难限制。这项工作中生成的数据将可用于对气溶胶沉积模型和痕量元素的大气输入进行地面验证。2) Be-7 的水柱测量提供了物理过程的示踪剂，例如混合和上升流，这些过程重新分配生物活性物种。给定 TEI 所在水团的循环、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生物地球化学行为。 3) 上温跃层内的氧气利用率将是通过 Be-7 的水柱测量结合收集的水文数据和观察到的氧气分布来确定。 Be-7 提供的季节性时间尺度非常适合估算富光带下方浅水中的 OUR，那里发生了最显着的碳再矿化。该项目将为佛罗里达国际大学的本科生研究人员提供支持，该大学是一家领先的少数族裔服务机构。首席研究员 Kadko 将参加日本基金会 - 全球海洋卓越观测中心伙伴关系 (NF-POGO CofE)，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项目。卡德科将在阿尔弗雷德韦格纳极地研究所学习期间为这些学生提供化学海洋学高级主题课程。这项外展工作符合 GEOTRACES 的能力建设和教育目标以及促进国际合作。

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