CAREER: Moving Beyond Equilibrium: Understanding the Ocean's Overturning Circulation in a Changing Climate

对海洋环流的大多数理论理解都假设，海洋能迅速感受到海面风和海-气热通量的变化，这是海洋环流的驱动因素。这一假设意味着在海洋表面驱动力的变化和整个海洋的海洋流动之间的瞬时动态平衡(所谓的稳态平衡解决方案)。数值模型表明，深海对表面变化的调整不是瞬时的，可能需要数千年的时间，这表明理论研究所需的稳态平衡方法可能会错过在十年到千年时间尺度上发生的海洋反应。这可能会对理解海洋颠覆环流产生重大影响，并影响我们做出准确气候预测的能力。将开发一套模型，以说明海洋在这些与气候相关的长时间尺度上对风强迫的变化做出反应所需的时间。这些模型将被用来更深入地了解控制海洋颠覆环流变化的每一种最基本的机制，以及它们的综合影响。该套件将作为开源软件在网上发布，并将为研究人员和学生提供互动计算体验，帮助他们建立对海洋动力学的直观理解。与此同时，它将促进学生现代计算技能的发展，这在研究和工业中都越来越重要。该项目将培训来自少数族裔的两名研究生和两名本科生实习生。此外，该项目将与高中生接触，向他们介绍海洋和气候科学--有助于将下一代科学家带入这一领域。这个项目将从理论上理解海洋对气候变化的非平衡响应，时间尺度从几十年到几千年。它的目的是缩小观测和数值模拟研究之间的差距，这些研究表明瞬时响应不同于使用平衡解获得的响应。这项拟议的研究集中在两个在文献中受到广泛关注的具体问题上，但预期发展的理论框架最终将适用于更广泛的问题，即海洋在过去和未来气候变化中的作用。第一个问题涉及海洋状态和环流对南大洋风应力变化的时间尺度反应。第二个问题涉及海洋对全球变暖的依赖时间的反应，既适用于人为气候变化，也适用于冰川-间冰期气候转变。这项调查将使用不同复杂程度的一系列模型，从机制上了解深海对几十年到几千年时间尺度上表层边界条件变化的反应。一个特别的重点将是为翻转循环开发一个简单的模型套件，它将被纳入这项提案的研究和教育部分。该模型套件将在一台笔记本电脑上使用，并将允许更深入地了解控制海洋颠覆环流变化的最基本机制。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Most theoretical understanding of the ocean circulation assumes that changes in surface winds and air-sea heat fluxes, the drivers of ocean circulation, are rapidly felt by the ocean. This assumption implies an instantaneous dynamic balance between changes in the drivers at the ocean surface, and ocean flow throughout the ocean (so-called steady-state equilibrium solutions). Numerical models show that the deep ocean adjustment to changes at the surface are not instantaneous, and can take many millennia, suggesting that the steady-state equilibrium approach required for theoretical studies can miss ocean responses occurring at decadal to millennial time-scales. This could have a significant impact on understanding ocean overturning circulation, and affect our ability to make accurate climate predictions. A suite of models will be developed that accounts for the time required for the ocean to respond to changes in wind forcing over these long, climate relevant time-scales. These models will be used to gain deeper insights into each of the most essential mechanisms that control changes in the ocean overturning circulation, and their combined effects. The suite will be disseminated online as open source software, and will provide researchers and students with an interactive computing experience to help them build an intuitive understanding of ocean dynamics. At the same time, it will foster the development of modern computational skills to students, something increasingly important in both research and industry. The project will train two graduate students as well as two undergraduate interns from underrepresented minorities. In addition, the project will engage with high-school students and introduce them to ocean and climate science - helping to entrain the next generation of scientists into this field. This project will develop a theoretical understanding of the nonequilibrium ocean response to changes in climate on time-scales from decades to millennia. It aims at closing the gap between observations and numerical modelling studies which demonstrate transient responses to be different than those obtained using equilibrium solutions. The proposed research focuses on two specific problems that have received wide attention in the literature, but the expectation is that the developed theoretical framework will eventually be applicable to a much wider range of questions about the ocean's role in past and future climate change. The first question addresses the time-scale dependent response of the ocean state and circulation to changes in the wind stress over the Southern Ocean. The second question addresses the ocean's time-dependent response to global warming, with applications to both anthropogenic climate change as well as glacial-interglacial climate transitions. The investigation will use a hierarchy of models of varying complexity to obtain a mechanistic understanding of the deep ocean's response to changes in the surface boundary conditions on time-scales from decades to millennia. A particular focus will be on the development of a simple model suite for the overturning circulation, which will be incorporated both in the research and educational component of this proposal. The model suite will be set up in Python for use on a laptop computer and will allow deeper insight into the most essential mechanisms that control changes in the ocean overturning circulation.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.