GEOTRACES Peru-Tahiti section: Measurement of 7Be as a Tracer of Upper Ocean Processes

在海洋中，微量元素作为营养物质，作为人类活动的污染物，甚至作为当前和过去海洋过程的方便示踪剂发挥着各种各样的作用。它们的生物地球化学循环对海洋碳循环和生态系统动态以及全球气候变化具有重要影响。影响海洋中微量元素分布和行为的许多过程不能直接观察到，因此使用各种地球化学示踪剂来提供对其速率和途径的重要限制。铍-7 （Be7）是一种宇宙生成（即在高层大气中产生）的放射性核素，由于其半衰期（53.3d），可用于研究季节性时间尺度上发生的环境过程。这个时间尺度对生物生产、养分再生和大气沉积等研究都很重要。在这个项目中，迈阿密大学的一个研究小组将于2013年测量从秘鲁到塔希提岛的美国geotraces样带的水柱Be7。国际GEOTRACES计划（美国是该计划的一个组成部分）的任务是“确定控制海洋中关键微量元素和同位素分布的过程和量化通量，并确定这些分布对不断变化的环境条件的敏感性。”作为美国多机构GEOTRACES太平洋活动的一部分，迈阿密团队将解决GEOTRACES科学计划中制定的关键任务。具体而言，它们将：(1)提供影响测量的感兴趣微量元素（TEI）分布的潜在运输过程的现实估计；他们将使用Be7的水柱测量作为物理过程的示踪剂，例如混合和上升流，这些过程会重新分配生物活性物种；(2)开发和应用新的Be7方法来量化其他参与该活动的研究团队测量的TEIs的大气沉积。对沿巡航轨道的地表水和低层大气中的Be7的测量将提供对相关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模型和微量元素的大气输入的地面真实性。更广泛的影响：建议的工作是为了支持GEOTRACES计划，并因此对该计划的许多广泛的智力目标做出了贡献。提供相关tei的大气输入估计的能力是一个重要的例子，它将在未来对GEOTRACES以外的领域作出广泛贡献，包括了解人为对海洋的影响。研究生的教育和培训将是这项研究的重要组成部分。

In the ocean, trace elements function variously as nutrients, as contaminants from human activity, and even as convenient tracers of current and past oceanographic processes. Their biogeochemical cycling has major impacts on the ocean carbon cycle and ecosystem dynamics as well as on global climate change. Many processes influencing the distribution and behavior of trace elements in the ocean cannot be directly observed, so consequently a variety of geochemical tracers are used to provide important constraints on their rates and pathways. Beryllium-7 (Be7) is a cosmogenic (i.e., produced in the upper atmosphere) radionuclide that, because of its half-life (53.3d), can be used in the study of environmental processes occurring over seasonal timescales. This timescale is important to studies of biological production, nutrient regeneration, and atmospheric deposition, to name a few. In this project, a research team from the University of Miami will make measurements of water column Be7 along the U.S.GEOTRACES transect from Peru to Tahiti in 2013. The mission of the International GEOTRACES Program (of which the US program is a component) is "to identify processes and quantify fluxes that control the distributions of key trace elements and isotopes in the ocean, and to establish the sensitivity of these distributions to changing environmental conditions." As part of the multi-institutional U.S.GEOTRACES Pacific campaign, the Miami team will address key tasks formulated within the GEOTRACES Science Plan. Specifically, they will: (1) provide realistic estimates of the underlying transport processes influencing measured trace elements of interest (TEI) distributions; they will use water column measurements of Be7 as a tracer of physical processes, such as mixing and upwelling, which redistribute biologically active species; and (2) develop and apply new Be7 methods for quantifying the atmospheric deposition of TEIs measured by other research teams participating in the campaign. Measurements of Be7 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 aerosol deposition models and the atmospheric input of trace elements. Broader impacts: The proposed work is in support of the GEOTRACES program, and as such contributes to many of the broad intellectual objectives of that program. The ability to provide estimates of the atmospheric input of relevant TEIs is an important example, and one that will contribute widely to the field in the future beyond GEOTRACES, including understanding anthropogenic impacts on the oceans. Education and training of graduate students will be essential components of this research.