Collaborative Research: Probing the Ventilation Efficiency of the Deep Ocean with Conservative Dissolved Gas Tracers in Archived Samples

合作研究：利用存档样本中的保守溶解气体示踪剂探测深海的通风效率

• 批准号: 2122427
• 负责人: Alan Seltzer
• 金额: $ 66.92万
• 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: 2021
• 资助国家: 美国
• 起止时间: 2021-09-01 至 2024-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2122427&HistoricalAwards=false
• 关键词: Collaborative; Research; Probing; Ventilation; Efficiency

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2).The transfer of gases between the atmosphere and the interior of ocean is controlled by processes in the high latitudes, where deep waters are “formed” by the sinking of cold and/or salty surface waters. The processes that affect air-sea gas exchange during water mass formation play an important role in the uptake of carbon dioxide and other important gases by the ocean. Dissolved noble gases, which are not affected by chemistry or biology, are excellent tracers of the physics of air-sea gas exchange: their abundances in the ocean interior tell us about how efficient gas exchange was when water was last at the sea surface. Another tracer, the “triple oxygen isotope” (TOI) composition of dissolved oxygen (a measure of the relative abundances of oxygen-16, oxygen-17, and oxygen-18) is sensitive to both biology and physics. However, each of these important tracers of air-sea exchange remains understudied in the modern ocean. This project aims to make new state-of-the-art measurements of noble gases and TOIs in 100 archived gas samples from the North and South Atlantic. The methods developed in this project will also enable future research opportunities that take advantage of these valuable samples. The project will support the training of a PhD student and multiple undergraduates, while contributing to ongoing efforts to develop workshop and lecture materials for a new partnership between Woods Hole Oceanographic Institution (WHOI) and a nearby public high school that has a primarily underrepresented minority student body.The primary objective of this project is to quantify the magnitude and spatial variability of two sets conservative tracers that are each independently sensitive to air-sea gas exchange at the time of deep-water formation: noble gases and TOIs. A deeper understanding of these tracers will provide insight into the physical mechanisms that regulate the efficiency of deep-ocean ventilation. Over recent decades, multiple studies have consistently found undersaturation of the heavy noble gases (Ar, Kr, and Xe) in the deep ocean, with respect to their solubility equilibrium concentrations in seawater. However, while several theories exist, there is no consensus on why the heavy noble gases are undersaturated throughout the deep ocean nor any reason to suspect that a single process is responsible. The spatial variability in noble gas disequilibrium between the North and South Atlantic may provide key clues to this open question, given the vastly different mechanisms of northern and southern deep-water formation. However, to date, analytical limitations have limited the robust detection and quantification of inter water-mass differences in disequilibrium. TOIs may also provide insight into air-sea disequilibrium during deep-water formation, as the relative excess of oxygen-17 (with respect to the atmospheric oxygen isotope ratios and corrected for isotopic fractionation due to respiration) reflects the balance between air-sea exchange and photosynthesis. Together, noble gases and TOIs provide useful constraints to elucidate fundamental mechanisms. For example, sea-ice cover in regions of deep-water formation will simultaneously lead to undersaturation of noble gases and accumulation of photosynthetic oxygen (and thus excess oxygen-17). However, few high-quality measurements of TOI in the deep ocean exist, due to analytical challenges, despite the great potential of TOI as a conservative tracer of physics and biogeochemistry during deep-water formation. The proposed work will involve 100 measurements of archived dissolved gas samples that were extracted at sea in the 1980s and stored in robust tanks since collection. This project is the first effort to measure noble gases and TOI in the same deep-ocean samples across a wide spatial range, by consistently employing the same methodology and instrumentation to eliminate inter-laboratory biases. It involves measurements in three WHOI labs and makes use of state-of-the-art techniques for each independent tracer measurement. This work builds in redundancy to improve the accuracy of results by measuring all samples on multiple instruments, including pairs of adjacent stations, and carrying out extraction experiments with the original equipment used in the 1980s to collect these samples. For example, heavy noble gas elemental ratios will be measured independently on two separate instruments, and high-precision (order 0.01 permil) measurements of noble gas isotopes will be used to test and correct for sample integrity. Overall, this large set of archived gases offers a unique opportunity to better understand these tracers and explore the quantitative insight they may offer into outstanding questions about the deep-ocean ventilation.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.

该奖项是根据2021年《美国救援计划法》（公共法第117-2）的全部或部分资助的。大气与海洋内部之间的气体转移受高纬度地区的过程控制，在那里，寒冷和/或咸水的沉没形成了深水。在水质量形成过程中影响空气气体交换的过程在海洋二氧化碳和其他重要气体的吸收中起着重要作用。不受化学或生物学影响的溶解的贵重气体是空气气体交换物理学的出色示踪剂：它们在海洋内部的丰度告诉我们，当水是最后一次在海面上的水时，气体交换的效率有多高。另一个示踪剂是溶解氧的“三重氧同位素”（TOI）组成（对氧相对丰度，氧气16，氧和氧气-18的相对丰度的度量）对生物学和物理学敏感。但是，在现代海洋中，这些重要的空气交流示踪剂中的每一个仍被理解。该项目旨在在北大西洋和南大西洋100个存档的气体样品中对贵重气体和TOI进行新的最新测量。该项目中开发的方法还将带来未来的研究机会，以利用这些有价值的样本。该项目将支持对博士学位学生和多个本科生的培训，同时为开发研讨会和演讲材料的持续努力，为伍兹洞海洋学机构（WHOI）和一所近公立高中建立新的合作伙伴关系，该伙伴关系具有主要代表性不足的少数派学生的主要目标。深水形成的时间：高贵的气体和tois。对这些示踪剂的更深入了解将提供对调节深海洋通风效率的物理机制的见解。在最近几十年中，就海水中的溶解度当量浓度而言，多项研究一直发现，在深海中，沉重的贵重气体（AR，KR和XE）持续不饱和。但是，尽管存在几种理论，但在整个深海中沉重的贵重气体为什么不饱和，也没有任何理由怀疑一个过程是造成的，尚无共识。鉴于北部和南部深水形成的机制截然不同，北大西洋和南大西洋之间贵族气体盘的空间变化可能为这个开放问题提供关键线索。然而，迄今为止，分析局限性限制了二滴水序列间质量差异的可靠检测和定量。 TOI还可以在深水形成过程中对空气不平衡的洞察力，因为相对过量的氧气17（相对于大气中的氧同位素比，并且因呼吸而引起的同位素分馏）反映了空气 - 海洋交换和光合作用之间的平衡。高贵的气体和TOI一起提供了有用的限制，以阐明基本机制。例如，深水形成区域中的海冰覆盖只会导致贵重气体的不饱和度和光合氧的积累（从而超过氧气17）。然而，由于分析挑战，尽管在深水形成期间，由于TOI是保守的物理学和生物地球化学的保守示踪剂，因此，由于分析挑战的高质量测量很少。拟议的工作将涉及100次测量存档的溶解气体样品，这些溶解气体样品在1980年代在海上提取，并在收集以来存储在健壮的储罐中。该项目是在广泛的空间范围内相同深度海洋样品中测量贵重气体和TOI的第一个努力，它始终采用相同的方法和仪器来消除实验室间偏见。它涉及三个WHOI实验室中的测量，并利用每个独立示踪剂测量的最新技术。这项工作以冗余的形式建立，以通过测量多种仪器（包括相邻站点对）上的所有样品，并使用1980年代使用的原始设备来收集这些样品，从而提高结果的准确性。例如，将在两种单独的仪器上独立测量重的贵重气体元素比，并将使用高精度（0.01 persil）的贵重气体同位素测量来测试并正确地测试样品完整性。总体而言，这种大量存档的天然气为更好地了解这些示踪剂提供了一个独特的机会，并探索了他们可能在有关深度海洋通风的杰出问题中提供的定量见解。该奖项反映了NSF的法定任务，并被认为是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的支持。