Collaborative Research: Novel constraints on air-sea gas exchange and deep ocean ventilation from high-precision noble gas isotope measurements in seawater

合作研究：海水中高精度稀有气体同位素测量对海气交换和深海通风的新限制

• 批准号: 1923915
• 负责人: Peter Barry
• 金额: $ 54.83万
• 依托单位: Woods Hole Oceanographic Institution
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-09-01 至 2024-02-29
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1923915&HistoricalAwards=false
• 关键词: Collaborative; Research; Novel; constraints; air

The proposed work brings together the fields of chemical oceanography, ocean modeling, and solid Earth geochemistry to develop the stable isotope composition of heavy noble gases dissolved in seawater as novel physical tracers of air-sea gas exchange. Noble gases represent ideal tools for quantifying physical processes due to the fact that they are chemically inert. Because argon (Ar), krypton (Kr), and xenon (Xe) isotope ratios have distinct solubility and diffusivity ratios, as recently quantified in laboratory experiments, they complement existing bulk noble gas measurements in seawater by adding new constraints with unique sensitivities. Precise constraints on air-sea exchange of inert gases are paramount to properly quantifying production, consumption, and physical transport of biogeochemically important gases (such as carbon dioxide and oxygen) as well as ventilation age tracers (such as sulfur hexafluoride and CFCs). Additionally, global circulation models (GCMs) routinely underestimate deep-ocean ventilation compared to noble gas observations. Introducing these new isotopic constraints into model simulations will help identify physical processes related to deep-water formation that require improvement in future GCM development. Because the overturning circulation is closely tied to projections of future climate, by both the transports of radiative gases and heat into the deep ocean, there is broad international interest in improving future model projections. Therefore, adding high-precision noble gas isotope measurements to the existing body of research on inert gases in seawater will provide valuable new constraints for both the marine biogeochemistry and physical oceanography communities. Education and training of a graduate student and postdoctoral scholar will contribute to the human resource base of the United States. The proposed work will develop high-precision Ar, Kr, and Xe stable isotope ratios in seawater as new oceanographic tracers. Along with a 2018 pilot study, the proposed measurements represent the first high- precision Kr and Xe isotope ratio analyses in seawater. A key goal of this project is to test two specific hypotheses for the observed undersaturation of Ar, Kr, and Xe throughout the deep ocean: (1) rapid cooling-induced gas uptake by the surface ocean during deep-water formation with insufficient time for equilibration before sinking, or (2) subsurface cooling caused by melting of glacial ice, leading to the dissolution of air bubbles trapped in ice. Whereas both of these non-mutually exclusive processes produce similar patterns of heavy noble gas undersaturation, the isotope ratios of these gases are well suited to distinguish the relative importance of each process. Specifically, theoretical predictions suggest a decrease in heavy-to-light isotope ratios from the kinetic fractionation associated with rapid surface ocean gas uptake, but an increase in these ratios from the input of gravitationally enriched glacial meltwater. Other goals include: (a) comparing observations to model simulations to identify successes and shortcomings of GCM representations of deep-water formation processes, and (b) a year-long time series of surface-ocean observations from the SIO pier to test models of isotopic fractionation associated with bubble injection and upwelling, with implications for the saturation of biogeochemically important gases. This work will improve upon a recent method for dissolved noble gas isotopic analysis by increasing sample sizes and refining purification techniques to achieve a 60% improvement in precision.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.

拟议的工作汇集了化学海洋学，海洋建模和固体地球地球化学领域，以发展溶解在海水中的重贵重气体的稳定同位素组成，作为空气气体交换的新型物理示踪剂。贵重气体代表了量化物理过程的理想工具，因为它们是化学惰性的。因为氩（AR），Krypton（KR）和Xenon（XE）同位素比具有明显的溶解度和扩散率，因此最近在实验室实验中进行了量化，因此它们通过添加具有独特敏感性的新约束来补充海水中现有的大量贵重气体测量。惰性气体交换的精确限制对于正确量化生物地球化学重要气体（例如二氧化碳和氧气）以及通风年龄示踪剂（例如硫六氟化物和CFC）的生物地球化学重要气体（例如二氧化碳和氧气）的生产，消耗和物理运输至关重要。此外，与高贵的气体观测相比，全球循环模型（GCMS）通常低估了深海洋通风。将这些新的同位素约束引入模型模拟将有助于确定与深水形成相关的物理过程，这些过程需要改善未来的GCM开发。由于倾覆的流通与未来气候的预测紧密相关，因此辐射气体和热量向深海的运输都息息相关，因此在改善未来模型预测方面具有广泛的国际兴趣。因此，在现有的有关海水惰性气体的研究体中添加高精度贵重同位素测量值将为海洋生物地球化学和物理海洋学群落提供宝贵的新约束。对研究生和博士后学者的教育和培训将为美国的人力资源基础做出贡献。拟议的工作将在海水中以新的海洋示踪剂的形式发展出高精度的AR，KR和XE稳定的同位素比。除了2018年的试点研究外，所提出的测量值代表了海水中的第一个高精度KR和XE同位素比分析。 A key goal of this project is to test two specific hypotheses for the observed undersaturation of Ar, Kr, and Xe throughout the deep ocean: (1) rapid cooling-induced gas uptake by the surface ocean during deep-water formation with insufficient time for equilibration before sinking, or (2) subsurface cooling caused by melting of glacial ice, leading to the dissolution of air bubbles trapped in ice.尽管这两个非纯正排斥过程都产生了类似的重质量气体不饱和模式，但这些气体的同位素比非常适合区分每个过程的相对重要性。具体而言，理论上的预测表明，与快速表面海洋气体吸收相关的动力学分馏量降低了重度同位素比，但这些比率增加了重力富集的冰川融合水的输入。 Other goals include: (a) comparing observations to model simulations to identify successes and shortcomings of GCM representations of deep-water formation processes, and (b) a year-long time series of surface-ocean observations from the SIO pier to test models of isotopic fractionation associated with bubble injection and upwelling, with implications for the saturation of biogeochemically important gases.这项工作将通过增加样本量和提高纯化技术以提高精度的最新方法来改善溶解贵重同位素分析的方法。该奖项反映了NSF的法定任务，并被认为是值得通过基金会的知识分子优点和更广泛影响的审查标准来通过评估来获得支持的。

项目成果

The triple argon isotope composition of groundwater on ten-thousand-year timescales

万年时间尺度地下水的三重氩同位素组成

• DOI: 10.1016/j.chemgeo.2021.120458
• 发表时间: 2021
• 期刊: Chemical Geology
• 影响因子: 3.9
• 作者: Seltzer, Alan M.;Krantz, John A.;Ng, Jessica;Danskin, Wesley R.;Bekaert, David V.;Barry, Peter H.;Kimbrough, David L.;Kulongoski, Justin T.;Severinghaus, Jeffrey P.
• 通讯作者: Severinghaus, Jeffrey P.

Solubility Equilibrium Isotope Effects of Noble Gases in Water: Theory and Observations

稀有气体在水中的溶解度平衡同位素效应：理论与观察

• DOI: 10.1021/acs.jpcb.3c05651
• 发表时间: 2023
• 期刊: The Journal of Physical Chemistry B
• 作者: Seltzer, Alan M.;Shackleton, Sarah A.;Bourg, Ian C.
• 通讯作者: Bourg, Ian C.

A unified method for measuring noble gas isotope ratios in air, water, and volcanic gases via dynamic mass spectrometry

通过动态质谱测量空气、水和火山气体中稀有气体同位素比率的统一方法

• DOI: 10.1016/j.ijms.2022.116873
• 发表时间: 2022
• 期刊: International Journal of Mass Spectrometry
• 影响因子: 1.8
• 作者: Seltzer, Alan M.;Bekaert, David V.
• 通讯作者: Bekaert, David V.

Widespread six degrees Celsius cooling on land during the Last Glacial Maximum

末次盛冰期陆地上普遍降温六摄氏度

• DOI: 10.1038/s41586-021-03467-6
• 发表时间: 2021
• 期刊: Nature
• 影响因子: 64.8
• 作者: Seltzer, Alan M.;Ng, Jessica;Aeschbach, Werner;Kipfer, Rolf;Kulongoski, Justin T.;Severinghaus, Jeffrey P.;Stute, Martin
• 通讯作者: Stute, Martin