Abstract:
The deep ocean is stably stratified in density as a result of vertical variations in temperature and salinity. This stratification allows internal gravity waves to propagate throughout the ocean interior. These internal waves are thought to play a fundamental role in oceanic mixing, as they contribute to the reduction of stratification, enhance vertical fluxes of heat, salt, and nutrients, and ultimately sustain the global meridional overturning circulation.
Mixing is driven by wave turbulence, which can lead to wave breaking and the generation of intense small-scale turbulence. Submesoscale motions observed in the ocean interior are often attributed to such wave-turbulent dynamics. To improve our understanding of the dynamics and statistical properties of nonlinear internal waves, we conducted laboratory experiments in the Coriolis facility, a large rotating tank 13 m in diameter and 1 m deep, in which stable density stratification is achieved using controlled salinity gradients.
Using a combination of diagnostic tools—including Eulerian and Lagrangian velocity measurements as well as density measurements—we compare our experimental results with theoretical frameworks such as Weak Wave Turbulence and Layered Anisotropic Stratified Turbulence. These theories aim to describe internal wave turbulence in stratified fluids but remain difficult to test experimentally due to the need for very large-scale facilities.