Transition to turbulence induced by near-inertial wave–vortex interactions

We study interactions between anticyclonic and cyclonic coherent barotropic vortices with inertial oscillations across a broad range of Rossby numbers and wave–vortex energy ratios. We examine parameter regimes where the interaction leads to high vertical velocities along with fine-scale dissipative structures and identify these as cases where the flow transitions to turbulence. The analysis reveals that flows that transition to turbulence have Rossby numbers and energy ratios inversely correlated. As a result, low Rossby number flows need a higher wave–vortex energy ratio while higher Rossby number flows can transition to turbulence at lower wave–vortex energy ratios. We also explore energetic interactions between the flow components using baroclinic–barotropic, linear wave–balance and a fast–slow decomposition. The results show that the three decompositions yield similar results at low Rossby numbers while the fast–slow and baroclinic–barotropic decompositions are better suited for high Rossby number flows. In all the cases we find that the slow barotropic vortical flow facilitates the forward cascade and dissipation of the fast baroclinic wave field, while its own dissipation and energy exchange with the wave field remain relatively small.