Collaborative Research: Measurement of tritium, helium isotopes, and noble gases on GO-SHIP line P18

GO-SHIP计划旨在描述热量、淡水、碳、氧、营养物和其他化学示踪剂随时间演变的全球尺度海洋分布，以阐明和量化重要的物理和地球化学过程，并记录全球变化。 作为这项国际努力的一部分，2016年在东太平洋和南大洋（从下加利福尼亚到南极洲的冰缘）沿沿着约110°W占领了P18分区。这笔赠款将资助在2016年P18部分收集的大约500个存档水样上测量海洋示踪剂-氚，3 He/4 He同位素比和全套惰性气体（He，Ne，Ar，Kr和H2O）。 示踪剂样品将在世界卫生组织同位素地球化学设施的专门提取系统和质谱仪上进行处理。 不断演变的海洋气候系统给我们带来了前所未有的挑战。冰川和海冰融化增加，海平面上升，海洋酸化和脱氧是一些必须预测的社会重要影响，如果可能的话，可以使用全球海洋环流和地球化学模型进行定量预测。 这样的模型需要更好地理解内在过程，因为它们必然是复杂的，但不完整的现实抽象，它们需要观察校准，测试和（如果可能的话）验证。 评价 和 在许多其他观测数据集和理论的背景下，记录这些示踪剂的分布及其演变，将为全球海洋气候物理和地球化学模型提供宝贵的制约因素，而这些模型是理解和处理全球变化的关键。新的P18氚-3He和惰性气体数据将通过气候变化和大气研究中心和碳水文学办公室网站向任何感兴趣的各方公开提供。该项目的科学目标是：（1）记录2016年相对于1994年和2008年早期职业的P18部分上氚和3 He分布的演变，以阐明东太平洋通风和环流的十年尺度模式和可能的气候变化;（2）在东太平洋和南大洋进行首次高质量的惰性气体测量，以确定海气交换效应和太平洋溶解气体的贯向混合，以及冰川融化对环极深水的贡献。在美国全球海洋碳和重复水文计划中，氚-3He是一个2级（“非常可取”）数据集，与核心GO-SHIP计划分开资助，但大量利用并增加了测量和运输时间。新的氚-3He和惰性气体数据将在2016年GO-SHIP P18水文和示踪观测的背景下进行解释（例如，CFCs、SF6、O2）、1994年和2008年以前P18职业的氚-3He数据以及太平洋流域尺度 氚-3He 数据 从 其他 GO-SHIP 和 GEOTRACES 路段 新的示踪剂数据提供了独特的和有价值的信息，物理和地球化学过程在东太平洋和南大洋：氚作为一种瞬态示踪剂具有独特的半球不对称性，可用作诊断示踪剂的北与南水团来源在热带地区。氚-氦定年法提供了一种独特而敏感的测量方法，可以在年到十年的时间尺度上测量浅层通风和环流，这与其他示踪剂（如CFCs和SF6）不同，可以估计浅层沃茨的水团起源、年龄和变化。 深水中的氦同位素提供了有关热液羽流来源、扩散和稀释以及制约深水循环模式的重要信息。惰性气体是海气交换、水团来源、冰-海相互作用、上升流和原位底辟混合的敏感和明确的示踪剂。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的知识价值和更广泛的影响审查标准进行评估来支持。

The GO-SHIP program seeks to characterize the time-evolving global scale ocean distributions of heat, freshwater, carbon, oxygen, nutrients and other chemical tracers with a view to illuminating and quantifying important physical and biogeochemical processes and to document global change. As part of this international effort, the meridional section P18 was occupied in 2016 along approximately 110°W in the eastern Pacific and Southern Ocean (from Baja California to the ice edge off Antarctica). The grant will fund efforts to measure ocean tracers – tritium, 3He/4He isotope ratio, and the full suite of noble gases (He, Ne, Ar, Kr, and Xe) – on approximately 500 archived water samples collected on the 2016 P18 section. The tracer samples will be processed on specialized extraction systems and mass spectrometers at the WHOI Isotope Geochemistry Facility. Evolving ocean-climate systems present us with challenges that are never more important than now. Increased glacial and sea-ice melting, increasing sea level, ocean acidification, and deoxygenation are a few of the societally important effects that must be anticipated and if possible quantitatively predicted using global ocean circulation and biogeochemical models. Such models require a better understanding of the inherent processes, and because they are necessarily complex, yet incomplete abstractions of reality, they need observations for calibration, testing, and (if ever possible) verification. Evaluation and documentation of the distributions of these tracers and their evolution, within the context of many other observational data sets and theories, will provide valuable constraints on global ocean-climate physical and biogeochemical models that are key to understanding and dealing with global change. The new P18 tritium–3He and noble gas data will be made publicly available to any interested parties through the CLIVAR and Carbon Hydrographic Office (CCHDO) site. The project science objectives are to: (1) Document the evolving tritium and 3He distributions in 2016 on the P18 section relative to the earlier 1994 and 2008 occupations to illuminate decadal-scale patterns and possible climatic changes in ventilation and circulation in the eastern Pacific; (2) Make the first high quality noble gas measurements in the eastern Pacific and Southern Ocean to characterize air-sea exchange effects and diapycnal mixing on dissolved gases in the Pacific, and glacial melt contributions to the Circumpolar Deep Water. In the U.S. Global Ocean Carbon and Repeat Hydrography Program, tritium–3He is a Level 2 (“highly desirable”) data set that is funded separate from, but heavily leverages and adds to the measurements and ship time conducted by the core GO-SHIP program. The new tritium–3He and noble gas data will be interpreted in the context of the 2016 GO-SHIP P18 hydrographic and tracer observations (e.g., CFCs, SF6, O2), tritium–3He data from previous P18 occupations in 1994 and 2008, and Pacific basin-scale tritium–3He data from other GO-SHIP and GEOTRACES sections. The new tracer data offer unique and valuable information on physical and biogeochemical processes in the eastern Pacific and Southern Ocean: Tritium as a transient tracer has a unique hemispheric asymmetry that can be used as a diagnostic tracer of north vs south water mass provenance in the tropics. Tritium-helium dating provides a unique and sensitive measure of shallow ventilation and circulation on annual to decadal time-scales that is distinct from other tracers such as CFCs and SF6, giving estimates of water mass origins, ages, and modification in shallow waters. Helium Isotopes in the deep water provide important information regarding hydrothermal plume provenance, dispersion and dilution, and constraining deep-water circulation models. Noble gases are sensitive and unambiguous tracers of air-sea exchange, water mass provenance, ice-ocean interaction, upwelling, and in situ diapycnal mixing.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.