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: 1823452
• 负责人: Joseph Kuehl
• 金额: $ 27.95万
• 依托单位: University of Delaware
• 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: 2017-09-01 至 2022-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1823452&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。它们连接沿海和公海，通过营养物质、物种和热量的运输影响区域气候和生态系统，通过污染物的运输和对飓风强度的影响对人类人口产生更直接的影响。众所周知，环流主导着墨西哥湾1公里以上的环流，很可能是深层环流的主要驱动因素。尽管环流很重要，但人们对真实海洋环境中环流的动态知之甚少。实验室实验和理想化数值计算(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，并提供了一个框架来理解这些复杂的动力学。也就是说，环流系统的全球动力学似乎由解的尖点突变几何所支配。这项工作的目的是从实验和理论上将跨越边界流的尖点公式扩展到更现实的海洋情景，以便这种全球动力系统的理解可以更广泛地应用于实际的海洋系统。这将通过转台实验室实验和理论考虑相结合来实现。这项研究的结果将更好地让决策者了解气候变化和其他环境压力对半封闭盆地的影响。多态假设(尖点突变框架)在现实海洋条件下的确认和系统推广将影响到广泛的领域。在墨西哥湾，如果环流建模正确，飓风强度可能会得到更准确的预测。它还将提供一种手段，将海洋教育带到内陆？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内陆海洋教育中心，从而使基本上没有代表性的人口接触到海洋科学。该项目还将有助于初级教员PI的专业发展，结果的传播将提供一种基本地球物理流体动力学相互作用的独特方法。尖点突变观点源于对环流的动力系统解释(在这种情况下，环流代表全球动力系统方法)。结果表明，当惯性(海流强度)和涡度约束(物理上与海平面、风强迫、层结和地形有关)的控制参数变化时，环流系统经历全局分叉。通过跟踪突变面上的环路电流状态，可以以逻辑和可预测的方式理解环路状态、非环路状态和周期性涡流脱落状态之间的转变。尖点突变代表了对回路电流动力学的一种根本不同的思考方式。传统的环流研究主要集中在对锋面涡的形成和传播、正压和斜压不稳定发展以及其他局地动力特征的量化/识别上。尖点突变公式表明，这些局部动态只是全球系统分叉的症状。这一理论的一个重要结果是，半封闭盆地可能对微妙的气候变化表现出极高的敏感性。应该指出的是，尖点突变源于整个海洋系统普遍存在的惯性和涡度约束之间的平衡，这表明本研究的结果是广泛适用的。

项目成果

Dynamics of Gap-leaping Western Boundary Currents with Throughflow Forcing

穿流强迫下跨越间隙的西边界流动力学

• DOI: 10.1175/jpo-d-20-0216.1
• 发表时间: 2021
• 期刊: Journal of Physical Oceanography
• 影响因子: 3.5
• 作者: McMahon, Charles W.;Kuehl, Joseph J.;Sheremet, Vitalii A.
• 通讯作者: Sheremet, Vitalii A.

Effect of the Coastline Geometry on the Boundary Currents Intruding through the Gap

海岸线几何形状对侵入间隙的边界流的影响

• DOI: 10.3390/fluids7020071
• 发表时间: 2022
• 期刊: Fluids
• 影响因子: 1.9
• 作者: Kuehl, Joseph;Sheremet, Vitalii A.
• 通讯作者: Sheremet, Vitalii A.

Brief communication: A nonlinear self-similar solution to barotropic flow over varying topography

简短交流：变化地形上正压流的非线性自相似解

• DOI: 10.5194/npg-25-201-2018
• 发表时间: 2018
• 期刊: Nonlinear Processes in Geophysics
• 影响因子: 2.2
• 作者: Ibanez, Ruy;Kuehl, Joseph;Shrestha, Kalyan;Anderson, William
• 通讯作者: Anderson, William

An analytic solution for bottom intensified flow along sloping topography

沿倾斜地形底部强化流的解析解

• DOI: 10.1016/j.euromechflu.2020.03.007
• 发表时间: 2020
• 期刊: European Journal of Mechanics - B/Fluids
• 作者: Kuehl, Joseph;McMahon, Charles
• 通讯作者: McMahon, Charles

A Viscous, Two-Layer Western Boundary Current Structure Function

粘性两层西边界电流结构函数

• DOI: 10.3390/fluids5020063
• 发表时间: 2020
• 期刊: Fluids
• 影响因子: 1.9
• 作者: McMahon, Charles W.;Kuehl, Joseph J.;Sheremet, Vitalii A.
• 通讯作者: Sheremet, Vitalii A.