CMG Collaborative Research: The Oceanic Internal Wave Energy Spectrum-Synthesis of Theory and Observations

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The proposed effort is a synthesis of theory and observations of theoceanic internal wavefield. The work proposed is a trulycollaborative effort: the analysis of oceanic observations to groundtruth new theoretical descriptions of internal wave dynamics. Thetheoretical work proposed involves the use of a novel Hamiltonianformalism for the internal wave field, recently developed by thePI's. This has already been shown to include the high--frequencycomponent of the celebrated Garret--Munk spectrum as an exactstatistically stationary solution, as well as to account for much ofthe observed spectral variability. It is proposed to develop aselection principle, based on a combination of wave turbulence andasymptotic analysis, to determine how each oceanic realization of thisvariability is tied to the local nature of the forcing anddissipation, as well as to the latitude dependence of the Coriolis effect.Water in the ocean abyss is denser than water at the surface. Thisdensity stratification permits a class of waves within the oceaninterior, called internal waves. These waves are apparent as thedistortion of density surfaces, and their wave-like properties are dueto the restoring force of gravity. Internal waves are one of themajor player in ocean dynamics, as they can propagate over bigdistances, interact with each other and other major players in theocean, like vorticity and currents, internal waves break and mixwater. While involved in this complex dynamics, internal wavesredistribute mass, momentum, energy and tracers in the ocean.Understanding internal waves is a key element to understanding climatevariability, especially over long time periods. The most difficultpiece of this puzzle is the interaction of internal waves. The investigatorshave already contributed significantly to the understanding ofnonlinear internal wave interactions by demonstrating the existence ofan infinite family of statistically stationary solutions for theinternal wave spectrum, of which the celebrated Garrett and Munkspectrum is a member. Now they propose to investigate whetherparticular members of this infinite family are more likely thanothers, as well as quantify the effects of interaction of internalwaves with other key players in the ocean. This research will beaided by the ongoing analysis of oceanic data sets and will contributecrucial missing components to the theory of ocean mixing, weather and,ultimately, climate.