Collaborative Research: Formation of Multiple Zonal Jets in the Oceans

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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.