Dynamics of small-scale turbulence in the upper ocean under the action of currents and internal waves

We study the evolution of a turbulent layer in a stratified ocean layer using the theory of unsteady turbulent flows in a stratified fluid developed in [1] and subsequent works. The theory starts from a kinetic equation for turbulence parameters and results in the set of equations involving the mutual transformation of the kinetic and potential energies of turbulence that is shown to significantly affect the overall dynamics of energy exchange between small-scale turbulence and mesoscopic motions and the formation of the upper mixed layer. Besides, this approach allows an account for some important but usually neglected effects such as the dependence of vertical anisotropy of turbulence on stratification. Notably, the transformation between kinetic and potential energies eliminates the restriction on the existence of turbulence at large Richardson numbers.  The results are applied to the analysis of in situ data for turbulence evolution under the action of shear flows and internal waves, obtained in different regions that are significant for climate research, including the upper equatorial ocean. The fundamental role of potential energy in the formation of a turbulent flow is demonstrated.

The work was supported by RSF project No. 23-27-00002.

[1] Ostrovsky L.A., Troitskaya Yu.I. (1987) A model of turbulent transfer and dynamics of turbulence in a stratified shear flow. Izvestiya, Atm. and Oceanic Phys., 23(10), 767-773 (1987).