Interactions of internal gravity waves with other waves and mesoscale eddies

We find internal gravity waves everywhere in the oceans. The interaction of these waves with other waves or eddies are key to the energy transfers in the ocean and can also lead to wave breaking and density mixing, which in turn drives the large-scale mean flow. The importance of wave-wave interactions compared to wave-mean flow interactions, however, remains largely unknown. We present two methods to better understand both processes: First, the scattering of waves by other waves is evaluated numerically using the kinetic equation derived from the assumption of weak interactions. Second, the interaction of waves with a local coherent meso-scale eddy and a random eddy field is simulated using a novel numerical model called the Internal Wave Energy Model based on the six-dimensional radiative transfer equation. We find mainly a forward energy cascade due to wave-wave interactions. Waves loose energy to the local eddy at its rim in a critical layer like behaviour, while the eddy field scatters the waves along a constant frequency cone.