Energy cascade in the Garrett-Munk spectrum of internal gravity waves
arXiv:2305.13110 · doi:10.1017/jfm.2023.862
Abstract
We study the spectral energy transfer due to wave-triad interactions in the Garrett-Munk spectrum of internal gravity waves (IGWs) based on a numerical evaluation of the collision integral in the wave kinetic equation. Our numerical evaluation builds on the reduction of the collision integral on the resonant manifold for a horizontally isotropic spectrum. We directly evaluate the downscale energy flux available for ocean mixing, whose value is in close agreement with the empirical finescale parameterization. We further decompose the energy transfer into contributions from different mechanisms, including local interactions and three types of nonlocal interactions, namely parametric subharmonic instability (PSI), elastic scattering (ES) and induced diffusion (ID). Through analysis on the role of each type of interaction, we resolve two long-standing paradoxes regarding the mechanism for forward cascade in frequency and zero ID flux for GM76 spectrum. In addition, our analysis estimates the contribution of each mechanism to the energy transfer in each spectral direction, and reveals new understanding of the importance of local interactions and ES in the energy transfer.
References in corpus (10)
- Toward Regional Characterizations of the Oceanic Internal Wavefield
- Hamiltonian formalism and the Garrett-Munk spectrum of internal waves in the ocean
- Diffusion of inertia-gravity waves by geostrophic turbulence
- Full derivation of the wave kinetic equation
- Rossby and Drift Wave Turbulence and Zonal Flows: the Charney-Hasegawa-Mima model and its extensions
- A Hamiltonian Formulation for Long Internal Waves
- Downscale energy fluxes in scale invariant oceanic internal wave turbulence
- Inertia-gravity-wave scattering by geostrophic turbulence
- The Effect of Discrete Resonant Manifold Structure on Discrete Wave Turbulence
- Nonlocal gravity wave turbulence in presence of condensate