Collaborative Research: Origin, Dynamics and Transport Characteristics of the Large-Scale Eddy-Driven Patterns

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One of the principal consequences of mesoscale variability in the ocean is the spontaneous generation of coherent, slowly evolving patterns on spatial scales significantly exceeding the dominant scale of primary baroclinic instability. These Large-Scale Eddy-Driven Patterns (LEDPs) are generated and maintained by mesoscale eddies and preliminary results indicate that LEDPs represent a substantial fraction of variability in the oceans. Furthermore, LEDPs can play an important role in the transport of heat, salinity, bio-geo-chemical tracers, and momentum. Thus, it is vital to improve our understanding of these indirect eddy effects, especially in light of the need for the increased accuracy of future climate projections.Analytical models for the interaction between primary (mesoscale) and secondary (LEDP) structures will be developed using multi-scale techniques. Multi-scale methods are ideally suited to this task due to their transparency and ability to represent interactions between phenomena operating on distinct spatial and temporal scales. The novelty of our approach lies in the application of multi-scale methods to the primary eddy patterns realized in typical oceanic flows. This will make it possible to offer a realistic description of LEDPs, directly applicable to, and testable by, observations and comprehensive models. Theoretical models will be guided and validated by a hierarchy of numerical simulations with an increasing degree of realism, which will also focus on the properties and dynamics of LEDPs. Analytical studies, in turn, will be used extensively for interpretation of the numerical results. The combination of these approaches will reveal the complex interplay between mesoscale eddies and LEDPs, not possible through numerical simulation alone, and describe the eddy transport characteristics induced by the action of LEDPs. Specific research tasks include the analysis of: the formation mechanisms of LEDPs; the anisotropic dispersion of tracers induced by these structures; and the effects of the background state on LEDP dynamics.Oceanic variability plays an important, but poorly understood role in climate dynamics. Lateral eddy transfer is a fundamental component of the oceanic transport heat, nutrients, pollutants and other tracers. Thus, advances in the understanding of eddy-induced transport and low frequency variability in the oceans are needed to improve climate prediction capabilities, ultimately leading to societal benefits. Inferences from the theory and model runs will aid in the interpretation of observational data sets and in the planning of future observational strategies aimed at explaining large scale flow variability. In addition to its oceanographic importance, this study will have significant implications for fundamental fluid mechanics, geophysics and climate science. During this project, one Ph.D. student at RSMAS and a postdoctoral associate at NPS will participate in the planned research activities and develop expertise in eddying ocean dynamics. In addition, two graduate (MS) Navy students will perform their thesis research at NPS on topics related to this proposal at no cost to the project.