Turbulence in Forced Stratified Exchange Flows

Continuously forced, stratified exchange flows occur in many geophysical systems, such as through channels between ocean basins, between coastal shelves and the deep ocean, and at the mouth of rivers and estuaries. These exchange flows can be unstable to various instabilities that can promote the growth of turbulence and increase mixing between the two differing flows. While these mixing processes are assumed to be important to global ocean budgets, they are unresolved within Earth system models and therefore must be fully understood in order to accurately include through sub- grid scale parameterization. In this talk, we present results from three-dimensional direct numerical simulations of stratified exchange flows that are continuously forced by weakly damping the buoyancy and streamwise velocity back to their initial mean profiles. We explore a range of large and small values of the bulk Richardson number and, after an initial ‘spin-up’ period, a turbulent steady state is observed which is dependent on the bulk Richardson number. Both turbulence and mixing are characterized in each case and the implications for parameterization are discussed.