Internal wave

Summary

An internal wave is a gravity wave that travels inside a stably stratified fluid, rather than along its surface. The restoring force is buoyancy, and its frequency cannot exceed the Brunt–Väisälä frequency. In a continuously stratified fluid the waves propagate obliquely, and their energy moves at right angles to their phase velocity. Internal waves carry energy through the ocean and the atmosphere, and their breaking is a main cause of mixing in the deep ocean.