# In search of the energy spectra of internal wave turbulence

Wednesday 04, 10:15

Pierre-Philippe Cortet

Laboratoire FAST, CNRS, Université Paris-Saclay

It has long been proposed that small-scale oceanic dynamics results from nonlinear processes involving internal gravity waves. The scales in question are not resolved in oceanic models but are accounted for by ad-hoc parameterizations. Physically modeling their turbulent dynamics would therefore be a major lever for improving parameterizations in climate models. In this context, a promising avenue is the wave turbulence theory. Its implementation in the case of internal waves in density stratified fluids has nevertheless proved complex and remains an open problem. It is the subject of delicate questions concerning the convergence of the so-called “collision integral” which drives the dynamics in wave turbulence problems.

In this lecture, I will present two recent works, one theoretical and one experimental, which both aim at identifying solutions to the internal gravity wave turbulence problem.

On the theoretical side, we establish predictions for the energy spectra of the weak internal-wave turbulence problem which agree with oceanic observations. The key is the assumption that energy transfers are dominated by a class of non-local resonant interactions, known as *induced diffusion* triads.

On the experimental side, the regime of internal wave turbulence has remained globally inaccessible. Most experiments up to now indeed conducted to a discretization of the energy in frequency and wavenumber associated to the emergence of eigenmodes of the fluid domain. This feature prevents the flow from approaching the regime described by the wave turbulence theory. In our work we identify an experimental mean allowing to inhibit the discrete wave modes opening the way to the laboratory observation of a canonical internal gravity wave turbulence.