The role of oceans in climate asymmetries

海洋对地球气候的一系列科学上有趣和社会上相关的不对称负有责任。此外，海洋的长时间尺度和不同的区域环流对温室气体强迫下的地表和地下变暖模式施加了强烈的限制。反过来，海洋通过(i)深海异常热量的储存和（ii）地表变暖模式与大气辐射反馈之间的耦合调节全球变暖的速度和幅度，这控制着全球气候敏感性的演变。对海洋在气候中的作用的认识来自理想化的全球气候耦合模式（GCM）实验，其中不同的海洋环流和气候是由规定不同的大陆几何形状引起的。这个项目是在简化几何和云反馈的情况下研究大尺度海洋环流在地球气候系统中的作用。将考虑不同的理想大陆形态。这项工作改进了以前使用仅海洋模型或不包括云反馈的耦合模型的工作。这项工作将支持一名女研究生、一名助理教授为研究提供建议，以及一名兼职软件工程师在计算和建模的技术方面提供协助。研究生将在气候科学的教学和传播方面获得宝贵的经验。这个项目的理想结果将使它们成为本科和研究生课程的宝贵补充。为了在耦合模型中设计理想的大陆（或深海）几何形状而开发的工具将通过GitHub和最终在NCAR的社区地球系统模型（CESM）理想海洋模型层次结构中广泛提供给社区。该项目在三个关键方面改进了以前理想化的耦合建模框架：(i)通过采用最先进的模型组件，重要的是，这些组件代表了以前被忽视的现实云反馈；用新的大陆几何形状和不同的行星自转速率进行模拟；（三）利用由这些独特的大陆几何形状引起的一系列背景海洋环流制度进行二氧化碳强迫模拟。这些模式实验旨在回答关于海洋在气候和气候变化中的作用的关键问题。这项工作将使人们更好地了解大规模海洋环流产生的条件，并进而控制：(1)气候的大规模不对称；气候变化的地理格局；（三）全球变暖的速度和幅度。特别是，它将提供关于海洋和大气影响两极到赤道温度梯度的具体动力学的更深入的知识；经向热输运及其在海洋和大气之间的分配；淡水运输;热带降雨模式；深水地层定位及经向翻转。这项工作还可以为为什么gcm预测温室气体强迫下气候敏感性的增加提供一个物理理论，从而提高我们对气候预测中一个主要不确定性的理解。评估云和云反馈对这些特性的贡献的关键作用将是贯穿始终的重点。该奖项反映了美国国家科学基金会的法定使命，并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，被认为值得支持。

The oceans are responsible for a range of scientifically interesting and societally relevant asymmetries in Earth's climate. Moreover, the ocean's long timescales and diverse regional circulations impose strong constraints on the patterns of surface and subsurface warming under greenhouse-gas forcing. In turn, oceans mediate the rate and magnitude of global warming through (i) storage of anomalous heat at depth and (ii) the coupling between surface warming patterns and atmospheric radiative feedbacks, which governs the evolution of global climate sensitivity. Insights into the role of oceans in climate have come from idealized coupled global climate model (GCM) experiments wherein different ocean circulations and climates are induced by prescribing distinct continental geometries. This project is to examine the role of large scale oceanic circulation in the earth's climate system in simplified geometries and with cloud feedbacks. Different idealized continental configurations will be considered. This work improves upon previous efforts that have used ocean-only models or coupled models that did not include cloud-feedbacks. This work would support a female graduate student, an assistant professor to advise the research, and a part-time software engineer to assist in technical aspects of computing and modeling. The graduate student would gain valuable experience in teaching and communicating climate science. The idealized nature of results from this project would make them valuable additions to undergraduate and graduate courses. Tools developed for the purposes of designing idealized continental (or bathymetric) geometries in the coupled model will be made widely available to the community through both GitHub and, eventually, within NCAR's Community Earth System Model (CESM) idealized ocean model hierarchy.This project improves on previously idealized, coupled modeling framework in three key ways: (i) By employing state-of-the-art model components that, importantly, represent realistic cloud feedbacks which were previously neglected; (ii) By performing simulations with novel continental geometries and with varying planetary rotation rates; and (iii) By performing carbon dioxide forcing simulations with a range of background ocean circulation regimes induced by those distinct continental geometries. These model experiments are designed to answer key outstanding questions about the role of oceans in climate and climate change. The work will lead to improved understanding of the conditions by which large-scale ocean circulations arise and in turn govern: (i) large-scale asymmetries in climate; (ii) geographic patterns of climate change; and (iii) the rate and magnitude of global warming. In particular, it will provide deeper knowledge of the specific dynamics by which the oceans and atmosphere affect pole-to-equator temperature gradients; meridional heat transport and its partitioning between oceans and atmosphere; freshwater transport; tropical rainfall patterns; and localization of deep-water formation and meridional overturning. The work could also provide a physical theory for why GCMs predict increasing climate sensitivity under greenhouse-gas forcing, thus improving our understanding of one of the major uncertainties in climate projection. Evaluating the key role of clouds and cloud feedbacks in contributing to these features will be a focus throughout.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.