Numerical simulations of a Minimal Ocean Mixing Systems (MOMS)*

Diapycnal mixing is a critical component of the ocean energy budget and one of the processes which regulate the Meridional Overturning Circulation.

In analogy with the Minimal Channel Unit concept in boundary layer turbulence, we consider a Minimal Ocean Mixing System (MOMS), that is the smallest system which exibits a GM-like spectrum, i.e., a Zakharov-Kolmogorov solution of the associated wave kinetic equation at large to intermediate scales, and a hard isotropic turbulent regime at scales smaller than the Ozmidov scale. The idea is to move away from studying individual mixing events in favor of considering a system where mixing is "naturally" driven by the interaction of random internal waves.   

To simulate a MOMS, we use the Stratified Ocean Model with Adaptive Refinement to simulate  the flow in a uniformly stratified rectangular tank with aspect ratio 3, forced by a wavemaker that injects energy at low frequency. Over several hundreds forcing periods, nonlinearities create an internal wave field characterized by a GM spectrum. Episodically, instabilities develop which drive irreversible mixing. By monitoring the energy in the system, we can calculate the mixing efficiency of the system, as opposed to the mixing efficiency of individual mixing events.