Collaborative Research: Formation of Multiple Zonal Jets in the Oceans

观测和模拟研究最近证明，海洋包含多个交替的、近乎纬向的急流，这些急流覆盖所有大洋盆地，从海洋顶部向底部穿透。每股急流的典型宽度为100-300公里，典型速度为1-5厘米/S，并嵌入大尺度洋流中。海洋喷流也可能在动力学上与木星等巨大气体行星大气中的多个交替喷流有关。大气喷流的研究已经进行了几十年，大气学界形成了一套有用的理论思想。这些理论中的普遍假设是，这些喷流是一种由涡流维持的非线性现象。然而，不仅对大气层喷流的了解仍然很少，而且相应的理论观点与大洋喷流的相关性也受到质疑。多股喷流形成的潜在机制将用一系列海洋环流模型来研究。其核心思想是了解能够维持所观察到的喷流并确定其结构的物理机制。具体目标是：(1)在现有观测的背景下系统地描述喷流的现象学；(2)确定喷流特性对各种物理因素的依赖；(3)分析喷流内涡通量汇聚和各向异性混合的重要性；(4)研究与喷流有关的低频变异性；以及(5)确定喷流形成的机制。通过非线性解的分析和流动成分的线性稳定性分析来研究基本的流动机制和射流特性。需要解释的重要性质包括经向和垂直结构、振幅和急流的瞬时可变性。本课程将与现有的大气喷流理论以及更广泛的关于各向异性湍流的文献相联系。这个项目将使用理论、模型和观测来解决这类特殊的海洋涡旋/大尺度相互作用的基本但鲜为人知的物理问题。这项工作与为新出现的多个喷流的观测提供物理基础有关。与这些喷流相关的高度各向异性输运的参数化是另一个将受益于对该现象的基本理解的研究课题。该项目将资助迈阿密大学的一名研究生。

Observational and modeling studies have recently demonstrated that the ocean contains multiple, alternating, nearly zonal jets that cover all oceanic basins and penetrate from the top to the bottom of the ocean. The typical width of each jet is 100-300 km, typical velocity is 1-5 cm/s, and the jets are embedded in the large-scale oceanic currents. The oceanic jets may be also dynamically related to the multiple alternating jets in the atmosphere of such giant gas planets as Jupiter. The atmospheric jets have been studied for a few decades, and the atmospheric community developed a set of useful theoretical ideas. The prevailing hypothesis in these theories is that these jets are a nonlinear phenomenon, maintained by eddies. However, not only do the atmospheric jets remain poorly understood, but also the relevance of the corresponding theoretical ideas to the oceanic jets is under question. Potential mechanisms of the multiple jet formation will be studied with a hierarchy of ocean circulation models. The central idea is to understand physical mechanisms that can maintain the observed jets and determine their structure. Specific objectives are to: (i) systematically describe phenomenology of the jets in the context of available observations; (ii) establish dependence of jet properties on various physical factors; (iii) analyze importance of eddy flux convergences and anisotropic mixing within the jets; (iv) examine low-frequency variability associated with the jets, and (v) determine the mechanisms of jet formation. The underlying flow mechanisms and jet properties will be studied both with analysis of the nonlinear solutions and with linear stability analysis of the flow components. Important properties that need to be explained include meridional and vertical structures, amplitude, and transient variability of the jets. Connection will be made to existing atmospheric-jet ideas, as well as to the broader literature on anisotropic turbulence. This project will address fundamental but poorly understood physics of this particular class of oceanic eddy/large-scale interactions, using theory, models, and observations. The work has to do with providing the physical basis for the emerging observations of the multiple jets. Parameterization of highly anisotropic transport associated with these jets is another research topic that will benefit from fundamental understanding of the phenomenon. This project will support one graduate student at the University of Miami.