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

国际GEOTRACES项目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（TEIs）的分布，为勘探和发现创造一个独特的机会。”这是一项对放射性同位素铍-7进行测量的建议，铍-7将提供重要的生物地球化学速率信息，这些信息将在2018年美国GEOTRACES从塔希提岛到阿拉斯加的太平洋子午线样带期间测量。海洋中的许多过程不能直接观察到，因此，示踪剂用于对其速率和途径提供重要的限制。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，但对研究生物生产、营养再生和大气沉积等至关重要。采样和分析技术的进步，加上对Be-7在海洋生物地球化学循环中的行为的更好理解，为充分利用这种示踪剂提供了机会。拟议的工作有三个主要组成部分：1)测量沿巡航轨道的地表水和低层大气中的Be-7将提供有关tei的大气输入的估计。大气对全球海洋的输入是许多化学物种的重要预算组成部分，但很难加以限制。在这项工作中产生的数据将可用于使气溶胶沉积和大气微量元素输入模式的地面真实性。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，这些物理过程重新分配了生物活性物种。给定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集成的原位生物地球化学行为。3)上层温跃层内氧的利用速率将由be -7的水柱测量值与收集到的水文资料和观测到的氧分布相结合来确定。Be-7提供的季节性时间尺度对于估计光带下方浅水中的OUR是理想的，在这里发生了最显著的C再矿化。该项目将支持佛罗里达国际大学的本科生研究人员，这是一个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-全球海洋卓越观察合作中心（NF-POGO CofE），这是一个独特的平台，旨在为新兴国家的学生提供世界级的培训课程。在阿尔弗雷德·韦格纳极地研究所逗留期间，Kadko将为这些学生提供化学海洋学的高级专题课程。这项外联工作与GEOTRACES的能力建设和教育目标以及促进国际合作是一致的。

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.