Energy spectra of non-local internal gravity wave turbulence

TL;DR

This paper derives a simplified kinetic equation for internal gravity wave turbulence, revealing scaling laws consistent with ocean observations, emphasizing the role of non-local resonant interactions called induced diffusion triads.

Contribution

It introduces a simplified kinetic model highlighting the significance of non-local induced diffusion interactions in internal wave turbulence.

Findings

Scaling laws match ocean data

Energy transfer dominated by non-local interactions

Cascade linked to constant wave action flux

Abstract

Starting from the classical formulation of the weak turbulence theory in a density stratified fluid, we derive a simplified version of the kinetic equation of internal gravity wave turbulence. This equation allows us to uncover scaling laws for the spatial and temporal energy spectra of internal wave turbulence which are consistent with typical scaling exponents observed in the oceans. The keystone of our description is the assumption that the energy transfers are dominated by a class of non-local resonant interactions, known as the ``induced diffusion'' triads, which conserve the ratio between the wave frequency and vertical wave number. Our analysis remarkably shows that the internal wave turbulence cascade is associated to an apparent constant flux of wave action.