The proposed effort is a synthesis of theory and observations of the oceanic internal wavefield. The work proposed is a truly collaborative effort: the analysis of oceanic observations to ground truth new theoretical descriptions of internal wave dynamics. The theoretical work proposed involves the use of a novel Hamiltonian formalism for the internal wave field, recently developed by the PI's. This has already been shown to include the high--frequency component of the celebrated Garret--Munk spectrum as an exact statistically stationary solution, as well as to account for much of the observed spectral variability. It is proposed to develop a selection principle, based on a combination of wave turbulence and asymptotic analysis, to determine how each oceanic realization of this variability is tied to the local nature of the forcing and dissipation, as well as to the latitude dependence of the Coriolis effect.
Water in the ocean abyss is denser than water at the surface. This density stratification permits a class of waves within the ocean interior, called internal waves. These waves are apparent as the distortion of density surfaces, and their wave-like properties are due to the restoring force of gravity. Internal waves are one of the major player in ocean dynamics, as they can propagate over big distances, interact with each other and other major players in the ocean, like vorticity and currents, internal waves break and mix water. While involved in this complex dynamics, internal waves redistribute mass, momentum, energy and tracers in the ocean. Understanding internal waves is a key element to understanding climate variability, especially over long time periods. The most difficult piece of this puzzle is the interaction of internal waves. The investigators have already contributed significantly to the understanding of nonlinear internal wave interactions by demonstrating the existence of an infinite family of statistically stationary solutions for the internal wave spectrum, of which the celebrated Garrett and Munk spectrum is a member. Now they propose to investigate whether particular members of this infinite family are more likely than others, as well as quantify the effects of interaction of internal waves with other key players in the ocean. This research will be aided by the ongoing analysis of oceanic data sets and will contribute crucial missing components to the theory of ocean mixing, weather and, ultimately, climate.
