On Triad Interactions in a Linearly Stratified Ocean

Abstract

Triad interactions in a linearly stratified ocean are studied numerically using a Garrett?Munk energy spectrum as the initial condition. It is found by bispectrum analysis that wave?mean flow interactions dominate and resonant interactions are limited to very large scales. Resonant triads of parametric subharmonic instability type play an insignificant role in the energy distribution. Local sum resonant triads provide the most effective energy transfer at very large scales. The analysis of triadic energy transfer rates suggests that triad configuration determines the energy flow pattern. When the modes with zero horizontal wavenumber are set to zero, resonant interactions arise. Thus, over most of the Garrett?Munk spectrum the energy level is low enough for resonance, but due to strong nonlinearities induced by horizontal currents, resonance is destroyed and wave?mean flow interactions dominate. If the energy level is reduced by a factor of 100, the number of resonant modes increases but wave?mean flow interactions remain important at high wavenumber.