The Amplification of Internal Waves in the Ocean Interior

The conventional picture of internal waves in the ocean interior has the waves breaking, dissipating their energy, and driving vertical mixing. Here we present results from an internal wave-resolving numerical model that shows vastly different wave behavior. In our model, boundary generated waves are energised between 200m and 3km depth at rates of 0.1-1mW/m^2. This energy is drawn from the available potential energy (APE) associated with weak small-scale horizontal buoyancy gradients which are destroyed by the waves’ frontolytic strain. The wave field thus acts as an effective horizontal diffusion in respect to the mean flow with diffusivity of O(1-10)m^2/s. The horizontal wave-driven mixing is a significant sink of energy from the mean flow. However, this process is only observable in our model when relatively small explicit horizontal diffusivity and viscosity is used. Larger parameter values tend to reproduce the conventional picture of wave energy loss in the ocean interior. Which picture provides a realistic model of the world ocean? What are the consequences for the ocean’s energy budget and the location and strength of wave breaking? In this presentation we will address these questions using a suite of wave-resolving simulations with different sources and sinks of internal waves.