Speaker: Nicolas Lanchon
Abstract: The small-scale oceanic dynamics has now long been proposed to result from
non-linear processes involving internal gravity waves. Several models have been put
forward to describe this dynamic, a most promising one being the weak turbulence
theory (WTT). This model appears as a potential avenue for improving the
parameterization of small scales in global oceanic models. Nevertheless, the
implementation of the WTT in the case of density stratified fluids revealed to be complex
and is still the subject of delicate analytical questions regarding the convergence of the
collision integral. In this talk, we examine the weak turbulence theory in a linearly
stratified fluid from a new perspective. A key step in our work is to realize that the
turbulent cascade is driven by a subset of triadic resonant interactions, denoted as
induced diffusion triads. These interactions, nonlocal in both wavenumber and frequency, impose a constant ratio between the frequency and the vertical wave number. Then, we
derive a new analytical solution to the kinetic equation which leads to 1D energy spectra
compatible with typical oceanic observations. (Joint work with P.-P. Cortet)