Global Dynamics Approach to Gap Leaping and Loop Current Systems

间隙跳跃和环流系统的全局动力学方法

• 批准号: 1657856
• 负责人: Joseph Kuehl
• 金额: $ 29.61万
• 依托单位: Baylor University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-03-01 至 2018-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1657856&HistoricalAwards=false
• 关键词: Global; Dynamics; Approach; Gap; Leaping

Loop currents, such as those in the Gulf of Mexico or South China Sea, represent an important part of the ocean circulation. Linking the coastal and open ocean, they affect regional climate and ecosystems through the transport of nutrients, species and heat, with more direct influence on human population through the transport of pollutants and influence on hurricane intensity. It is well known that the Loop Current dominates the upper 1km of circulation in the Gulf of Mexico and is likely a major driver of the deep circulation. Despite its importance, little is understood about the dynamics of loop currents in real ocean situations. Laboratory experiments and idealized numerics (conducted by PI and his collaborators) have recently confirmed the existence of multiple steady states and hysteresis in loop current systems, as well as provided a framework under which these complex dynamics might be understood. That is, the global dynamics of loop current systems appear to be governed by a cusp catastrophe geometry of solutions. The objective of this work is to experimentally and theoretically expand the Cusp formulation of gap-leaping boundary currents toward more realistic oceanographic scenarios, so that such global dynamical systems understanding can be more broadly applied to actual oceanographic systems. This will be accomplished through a combination of rotating table laboratory experiments and theoretical considerations. The results of this research will better inform decision makers about the effects of climate change and other environmental stressors on semi-enclosed basins. The confirmation and systematic extension of the multiple states hypothesis (cusp catastrophe framework) in realistic ocean conditions will impact a wide range of fields. In the Gulf of Mexico, hurricane intensity may be predicted more accurately if loop currents are modeled correctly. It will also provide a means for ?bringing ocean education inland? with at least one graduate student and one undergraduate student participating directly in this project, but more generally it will help establish an inland hub for oceanographic education, thus exposing a largely unrepresented population to ocean science. The project will also serve to assist in the professional development of junior faculty PI, and the dissemination of results will present a unique approach to fundamental geophysical fluid dynamic interaction.The cusp catastrophe perspective follows from a dynamical systems interpretation of the Loop Current (which in this case represents a global dynamical systems approach to Gulf of Mexico circulation). It has been shown that when the control parameters of inertia (current strength) and vorticity constraints (which physically relate to sea level, wind forcing, stratification and topography) are varied, the loop current systems undergoes global bifurcations. By tracing the Loop Current state on the catastrophe surface, transitions between a looping state, a non-looping state and a periodic eddy shedding state can be understood in a logical and predictable way. The cusp catastrophe represents a fundamentally different way of thinking about Loop Current dynamics. Traditional studies of the Loop Current have focused on quantification/identification of frontal eddy formation and propagation, barotropic and baroclinic instability development, and other local dynamical features. The cusp catastrophe formulation suggests that these local dynamics are merely symptoms of a global system bifurcation. An important consequence of this theory is that semi-enclosed basins are likely to exhibit extreme sensitivity to subtle climate shifting. It should be noted that the cusp catastrophe follows from a balance between inertia and vorticity constraints which are prevalent throughout the entire ocean system, suggesting the results of this study are broadly applicable.

环流，如墨西哥湾或南中国海的环流，是海洋环流的重要组成部分。它们连接着沿海和公海，通过输送营养物质、物种和热量影响区域气候和生态系统，通过输送污染物和影响飓风强度对人口产生更直接的影响。众所周知，环流主导着墨西哥湾上层1公里的环流，可能是深层环流的主要驱动力。尽管它的重要性，很少有人了解的动态圈电流在真实的海洋的情况。实验室实验和理想化的数值（由PI和他的合作者进行）最近证实了回路电流系统中存在多个稳态和滞后现象，并提供了一个框架，在此框架下可以理解这些复杂的动力学。也就是说，环电流系统的全球动态似乎是由尖点突变几何的解决方案。这项工作的目的是从实验和理论上扩展Cusp制定的间隙跳跃边界流更现实的海洋学场景，这样的全球动力系统的理解可以更广泛地应用于实际的海洋学系统。这将通过旋转台实验室实验和理论考虑相结合来实现。这项研究的结果将使决策者更好地了解气候变化和其他环境压力对半封闭流域的影响。在现实海洋条件下，多态假设（尖点突变框架）的证实和系统扩展将影响到广泛的领域。在墨西哥湾，如果环流模型正确，飓风强度可以更准确地预测。它还将提供一种手段？把海洋教育带到内陆至少有一名研究生和一名本科生直接参与这一项目，但更广泛地说，这将有助于建立一个海洋学教育的内陆中心，从而使基本上没有代表的人口接触海洋科学。该项目还将有助于初级教师PI的专业发展，结果的传播将提出一个独特的方法，基本的地球物理流体动力学interaction.The尖点灾难的角度如下从动力系统解释的环流（在这种情况下，代表了一个全球动力系统的方法，墨西哥湾环流）。它已被证明，当控制参数的惯性（电流强度）和涡度约束（物理上涉及到海平面，风强迫，分层和地形）是不同的，环电流系统进行全球分叉。通过在突变表面上追踪回路电流状态，可以以逻辑和可预测的方式理解回路状态、非回路状态和周期性涡流脱落状态之间的转变。尖点灾难代表了一种从根本上不同的思考回路电流动力学的方式。传统的环流研究主要集中在锋面涡的形成和传播、正压和斜压不稳定发展以及其他局部动力学特征的定量/识别上。尖点突变公式表明，这些局部动态仅仅是一个全球系统分岔的症状。这一理论的一个重要结论是，半封闭盆地可能对微妙的气候变化表现出极端的敏感性。值得注意的是，尖点突变来自于惯性和涡度约束之间的平衡，这在整个海洋系统中普遍存在，这表明本研究的结果具有广泛的适用性。