GEOTRACES Pacific Section: Measurement of Helium Isotopes, Tritium, Noble Gases, and Radiocarbon

GEOTRACES 太平洋部分：氦同位素、氚、稀有气体和放射性碳的测量

• 批准号: 1232991
• 负责人: William Jenkins
• 金额: $ 79.77万
• 依托单位: Woods Hole Oceanographic Institution
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-01-01 至 2017-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1232991&HistoricalAwards=false
• 关键词: GEOTRACES; Pacific; Section; Measurement; Helium

The biogeochemical cycling of trace elements and isotopes (TEIs) in the marine environment is an important research area within the context of global change that motivates the International GEOTRACES program. Some trace elements are known to play potentially important roles as micronutrients in biological cycling, particularly in regard to enzymatic and catalytic processes in the marine environment. Radioisotopes, transient tracers, and noble gases are valuable tracers of these and related processes, and of the ocean?s interaction with the atmosphere and the solid earth, which in turn play a role in shaping many trace element distributions within the ocean. According to the GEOTRACES Science Plan, the guiding mission of the GEOTRACES program is "to identify processes and quantify fluxes that control the distributions of key trace elements and isotopes in the ocean". The key observational strategy for GEOTRACES is an internationally-coordinated global-scale ocean survey of key TEIs. The second US GEOTRACES section, set for the Eastern South Pacific in 2013, is aimed at the characterization of key processes in an oxygen minimum zone (OMZ), as well as a major abyssal hydrothermal plume extending westward from the East Pacific Rise. To help achieve these goals, with support from this grant, a research team at the Woods Hole Oceanographic Institution will collaborate with other GEOTRACES investigators on the Eastern South Pacific expedition to measure a suite of tracers useful for interpreting the rest of the synoptic TEI data. Specifically, the team will make measurements of the noble gases, helium isotopes, tritium, and radiocarbon include in order to: (1) quantify ventilation, circulation, and diapycnal mixing in the OMZ to enable estimation of fluxes and transformation rates of key TEIs; (2) determine upwelling rates in the oxygen minimum zone (OMZ) over a range of timescales to constrain the fluxes of biogeochemically important properties; (3) estimate hydrothermal fluxes of key TEIs using 3He as a flux gauge, and also use 3He as a measure of downstream dilution in the hydrothermal plume; (4) use radiocarbon to estimate abyssal remineralization rates for key TEIs; and (5) probe for evidence of off-axis contribution of hydrothermal processes to TEI distribution. The collective effort will allow marine geochemists to understand mechanistically and quantitatively how a variety of physical, chemical, and biological processes join to determine the distribtuion of TEIs in the ocean.Broader Impacts: It has been argued that anthropogenic influence on the global cycles of many elements is emerging as significant. As outlined in the International GEOTRACES Science Plan, the broader impacts of this activity include both an important "baseline snapshot" of the biogeochemical state of the oceanic environment, and a quantitative improvement in the characterization and understanding of important processes in the marine environment. Both of these build a foundation for improved models and quantitative predictions of the oceanic response and role in global change and climate, particularly with anthropogenic forcing. For example, recent evidence of "ocean deoxygenation" has profound implications for marine biologic response. In particular, the evolving state of marine OMZs represents an important biogeochemical "climate canary". A key benefit of diagnosing trace metal dynamics and response to changing redox conditions is the improvement in prognostic capabilities of coupled ocean-atmosphere biogeochemical models for global change.

在海洋环境中，痕量元素和同位素（TEI）的生物地球化学循环是全球变化范围内的重要研究领域，激发了国际地理领域的计划。已知一些痕量元素在生物循环中起着潜在的重要作用，尤其是在海洋环境中的酶促和催化过程方面。放射性同位素，瞬态示踪剂和贵重气体是这些和相关过程的有价值的示踪剂，以及与大气和固体地球的相互作用，这又在塑造海洋内许多痕量元素分布中起着作用。 根据Geotraces科学计划，Geotraces计划的指导使命是“识别流程并量化控制关键痕量元素和海洋同位素分布的通量”。 地理位置的关键观察策略是一项国际协调的全球规模海洋调查。 2013年为东南太平洋地区设置的第二个美国地理环境部分旨在表征氧最小区域（OMZ）中的关键过程，以及从东部Pacacific Rise向西延伸的主要深渊热液羽流。为了帮助实现这些目标，在这笔赠款的支持下，伍兹霍尔海洋学机构的研究团队将与其他地理领域的调查员在南太平洋东部探险方面合作，以测量一套有助于解释其余的TEI数据的示踪剂。 具体而言，该团队将对贵重气体，氦同位素，tri骨和放射性碳进行测量，包括：（1）量化OMZ中的通风，循环和杂音混合，以启用估计磁通量和关键TEIS的磁通速率； （2）确定在一系列时间尺度上氧最小区（OMZ）中的上升速率，以限制生物地球化学上重要特性的通量； （3）使用3HE作为通量表估算钥匙TEI的热液通量，并使用3HE作为水热羽流中下游稀释的量度； （4）使用放射性碳来估计关键TEI的深渊回忆率； （5）探测水热过程对TEI分布的及轴的证据。集体努力将使海洋地球化学主义者能够在机械和定量上理解各种物理，化学和生物学过程如何结合以确定海洋中TEI的分布。BROADER的影响：有人认为，人类对许多元素全球周期的影响是显着的。正如国际地理学科学计划中概述的那样，这项活动的更广泛影响包括海洋环境生物地球化学状态的重要“基线快照”，以及对海洋环境中重要过程的表征和理解的定量改善。这两者都为改善模型的基础和对海洋反应的定量预测以及在全球变化和气候中的作用而定量预测，尤其是在人为强迫的情况下。例如，“海洋脱氧”的最新证据对海洋生物学反应具有深远的影响。特别是，不断发展的海洋OMZ状态代表着重要的生物地球化学“气候金丝雀”。诊断痕量金属动力学和对变化氧化还原条件的响应的关键好处是，耦合的海洋 - 大气生物地球化学模型的预后能力改善了全球变化。