RII Track-4:NSF: Evaluating the Role of Deep Ocean Equilibration in Warmer Climates

RII Track-4：NSF：评估深海平衡在温暖气候中的作用

• 批准号: 2327230
• 负责人: Weimin Si
• 金额: $ 27.08万
• 依托单位: Brown University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2024
• 资助国家: 美国
• 起止时间: 2024-01-01 至 2025-12-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2327230&HistoricalAwards=false
• 关键词: RII; Track; NSF; Evaluating; Role

This Research Infrastructure Improvement Track-4 EPSCoR Research Fellows project will provide a fellowship to a Senior Research Associate and training for a graduate student at Brown University. This work would be conducted in collaboration with researchers at the National Center for Atmospheric Research (NCAR). The Intergovernmental Panel on Climate Change (IPCC 2021) predicts that atmospheric pCO2 will likely reach 940-1490 ppm by the end of the century. Consequently, global temperature is expected to increase by 1.5-4.5°C. This relationship between pCO2 levels and the magnitude of warming estimated from climate models is known as climate sensitivity. Models, however, are built upon an incomplete understanding of Earth’s climate system and, to some extent, upon simplifications of biogeochemical- and physical processes that drive climatic feedback due to our limited computational capability to fully grasp the vast complexity of the system. On the other hand, reconstructions of past climate change using deep-time archives, although sparse in time and space, offer ground truths of equilibrium climatic responses to elevated pCO2, allowing climatologists to benchmark the performance of climate models. In this proposed study, the PI and researchers at NCAR will collaborate to integrate paleoclimate reconstructions of 15 million years ago (aka. the Middle Miocene) with climate model simulations. Current studies suggest that the Middle Miocene was ~6-10°C warmer than today while estimated pCO2 was only 200-300 ppm higher. This suggests a climate sensitivity of 6-10°C warming per doubling of pCO2, much higher than the 1.5-4.5°C suggested by IPCC 2021. The new study aims to explore possible explanations for this model-data discrepancy, with the hope that insights we gain from studying climatic processes under past warm conditions can improve our knowledge about future climate changes.Projections of future global warming depend critically on our knowledge of climate sensitivity, which is continually refined by emerging reconstructions of past warm climates. The mid-Miocene Climate Optimum (MMCO, ~17.5-13.9 Ma) is one such period that has recently inspired the development of paleoclimate simulations, aimed at improving our understanding of climatic dynamics when estimated pCO2 was higher than today. Paleoclimate records, however, pose several challenges to climate models, including high climate sensitivities and flat meridional temperature gradients, both of which are difficult to reproduce in models. This proposal puts forth a hypothesis that a possibly overlooked contributing factor to MMCO warming and model-data disagreement is the equilibrium responses of the deep ocean under elevated CO2 forcing. Unlike SST, Miocene deep-ocean temperature and circulation have not received much attention. Yet increasing evidence suggests that the equilibrium responses of the deep ocean differ from transient responses, and significantly affect the spatial and temporal patterns of surface warming. Evolving feedback with changing SST patterns and the degree of equilibration in turn influences equilibrium climate sensitivity. This proposed study seeks to address this gap by (1) performing long-running MMCO simulations (6000 years) in collaboration with Jiang Zhu at NCAR (host institution) to produce equilibrium responses of the deep ocean; (2) comparing simulated MMCO oceans with paleo-proxies including benthic δ13C and Neodymium isotopes (ɛNd) to explore patterns of Miocene ocean circulation; and (3) examining whether modeled equilibrium responses of the deep ocean reduce model-data mismatches in deep-water temperatures as well as the spatial patterns of SST, with focuses on the warming anomalies in the North Atlantic and the flat meridional temperature gradients during the MMCO.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.

这项研究基础设施改进 Track-4 EPSCoR 研究员项目将为布朗大学的高级研究员提供奖学金，并为研究生提供培训。这项工作将与国家大气研究中心 (NCAR) 的研究人员合作进行。政府间气候变化专门委员会 (IPCC 2021) 预测，到本世纪末，大气中的 pCO2 可能会达到 940-1490 ppm，全球气温预计将上升 10%。 1.5-4.5°C。pCO2 水平与气候模型估计的变暖程度之间的这种关系被称为气候敏感性，然而，模型是建立在对地球气候系统的不完全了解的基础上的，并且在某种程度上是建立在生物地球化学的简化基础上的。 - 由于我们的计算能力有限，无法完全掌握系统的巨大复杂性，因此驱动气候反馈的物理过程另一方面，使用深度档案重建过去的气候变化，尽管时间和空间都稀疏。空间，提供平衡气候对 pCO2 升高的反应的基本事实，使气候学家能够对气候模型的性能进行基准测试。在这项拟议的研究中，PI 和 NCAR 的研究人员将合作整合 1500 万年前（又名中古气候）的重建。中新世）与气候模型模拟目前的研究表明，中新世比今天温暖约 6-10°C，而估计的 pCO2 仅高出 200-300 ppm。 pCO2 每增加一倍，气候敏感度就会升高 6-10°C，远高于 IPCC 2021 建议的 1.5-4.5°C。这项新研究旨在探索对这种模型数据差异的可能解释，希望我们的见解能够为我们提供更多见解。研究过去温暖条件下的气候过程可以提高我们对未来气候变化的了解。对未来全球变暖的预测在很大程度上取决于我们对气候敏感性的了解，而这种知识通过对过去温暖条件的重建而不断完善。中新世中期气候最佳期（MMCO，~17.5-13.9 Ma）是最近激发古气候模拟发展的一个时期，旨在提高我们对估计 pCO2 高于今天古气候记录时的气候动态的理解。然而，这给气候模型带来了一些挑战，包括高气候敏感性和平坦的经向温度梯度，这两者都很难在模型中重现。 MMCO 变暖和模型数据不一致的可能因素是深海在二氧化碳强迫作用下的平衡响应，与海表温度不同，中新世深海温度和环流并未受到太多关注，但越来越多的证据表明，深海的平衡响应。深海与瞬态响应不同，并影响地表变暖的空间和时间模式，而变化的海温模式和平衡程度反过来又会显着影响平衡气候敏感性。长期运行的与 NCAR（主办机构）的 Zhuiang Zhu 合作进行 MMCO 模拟（6000 年），以产生深海的平衡响应；(2) 将模拟的 MMCO 海洋与包括底栖 δ13C 和钕同位素 (ɛNd) 在内的古代表进行比较，以探索中新世海洋环流；以及（3）检查深海的模型平衡响应是否减少了深水温度以及空间的模型数据不匹配。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。