NSFGEO-NERC: Collaborative Research: Understanding the Drivers of Inert Gas Saturation to Better Constrain Ice Core-Derived Records of Past Mean Ocean Temperature

该奖项全部或部分由《2021年美国救援计划法案》（公法117-2）资助。全球海洋的综合热含量是了解地球能量平衡的一个基本气候变量。准确估计过去全球能量收支的变化对于理解地球系统固有的敏感性至关重要。该项目将通过对海洋中溶解气体进行计算机模拟来解决这些估计的准确性问题。通过分析这些模拟的结果，研究小组的目标是改进基于冰芯的海洋热含量重建，这种重建依赖于测量保存在冰芯中的古代气泡中的气体（氙、氪和氮）。该项目旨在首次估算末次盛冰期冰川海洋中氙、氪和氮饱和度异常的不确定范围。最近的分析进展已经允许测量冰芯中氙与氮和氪与氮的比率，其精度足以解决这些比率的全大气变化，这些变化反映了全球海洋在0.1ºC水平上的变暖和变冷。然而，要用惰性气体测量来定量地限制过去的海洋热含量，需要对这些气体的全球海洋饱和状态的长期变化进行假设，这仍然是一个完全开放的问题。因此，该团队将使用传输矩阵法进行生物地球化学示踪剂模拟。他们将利用维多利亚大学地球系统气候模型对冰川海洋中的氧气和二氧化碳进行一系列先前进行的模拟，以定量地限制惰性气体饱和状态下的冰期-间冰期变化，并了解其物理驱动因素。此外，研究小组将使用第二种模型（麻省理工学院全球环流模型）进行独立实验，并进行几项未来的变暖实验，以考虑地球系统中正在发生的变化如何影响物理空气-海洋气体转移。最后，研究小组将重新评估现有的冰芯惰性气体记录，以对末次盛冰期和末次消冰期突然变暖期间海洋热含量的变化做出最佳估计。该项目由美国国家科学基金会地球科学理事会（NSF/GEO）（美国参与者）和英国自然环境研究委员会（UKRI/NERC）通过NSF/GEO-NERC牵头机构协议共同资助。该协议允许美国/英国提交一份联合提案，并由其调查员拥有最大比例预算的机构进行同行评审。在成功地共同确定一项奖励后，每个机构为预算的比例和与自己的调查人员有关的调查人员和工作的组成部分提供资金。该奖项全部或部分由2021年美国救援计划法案（公法117-2）资助。该奖项反映了美国国家科学基金会的法定使命，并通过基金会的智力价值和更广泛的影响审查标准进行评估，认为值得支持。

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2). The integrated heat content of the global ocean is a fundamental climate variable for understanding Earth’s energy balance. Accurate estimates of past changes in the global energy budget are essential for understanding the inherent sensitivities of the Earth system. This project will address the accuracy of these estimates by carrying out computer simulations of dissolved gases in the ocean. By analyzing the outcomes of these simulations, the team aims to refine ice-core-based reconstructions of ocean heat content that rely on measurements of gases (Xenon, Krypton, and Nitrogen) in ancient air bubbles preserved in ice cores. The project aims to produce the first estimates and uncertainty ranges of saturation anomalies of Xenon, Krypton, and Nitrogen in the glacial ocean during the Last Glacial Maximum. Recent analytical advances have permitted measurement of ratios of Xenon to Nitrogen and Krypton to Nitrogen in ice cores at sufficient precision to resolve whole-atmosphere changes in these ratios that reflect warming and cooling of the global ocean at the 0.1ºC level. However, to quantitatively constrain past ocean heat content using inert gas measurements requires assumptions about long-term changes in the global ocean saturation state of these gases, which remains an entirely open problem. Consequently, the team will use the Transport Matrix Method for biogeochemical tracer simulations. They will build on a suite of previously conducted simulations of oxygen and carbon dioxide in the glacial ocean with the University of Victoria Earth System Climate Model to quantitatively constrain the glacial-interglacial change in inert gas saturation state and understand its physical drivers. In addition, the team will add independent experiments using a second model (the MIT global circulation model) and carry out several future warming experiments to consider how ongoing changes in the Earth system may affect physical air-sea gas transfer. Finally, the team will reevaluate existing ice-core inert gas records to produce best estimates of changes in ocean heat content during the Last Glacial Maximum and periods of abrupt warming throughout the last deglaciation. This is a project that is jointly funded by the National Science Foundation’s Directorate of Geosciences (NSF/GEO) (U.S. participants) and the Natural Environment Research Council (UKRI/NERC) of the United Kingdom (UK) via the NSF/GEO-NERC Lead Agency Agreement. This Agreement allows a single joint US/UK proposal to be submitted and peer-reviewed by the Agency whose investigator has the largest proportion of the budget. Upon successful joint determination of an award, each Agency funds the proportion of the budget and the investigators associated with its own investigators and component of the work.The NSF award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2)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.