Turbulence generation by large-scale extreme vertical drafts and the modulation of local energy dissipation in stably stratified geophysical flows

We observe the emergence of strong vertical drafts in direct numerical simulations of the Boussinesq equations in a range of parameters of geophysical interest. These structures, which appear intermittently in space and time, generate turbulence and enhance kinetic and potential energy dissipation, providing an explanation for the observed variability of the local energy dissipation in the ocean and the modulation of its probability distribution function. We show how, due to the extreme drafts, in runs with Froude numbers observable in oceans, roughly $10%$ of the domain flow can account for up to $50%$ of the total volume dissipation, consistently with recent estimates based on oceanic models.