Turbulence in the Deep Ocean: A Study of Lee Wave Propagation through Depth-Varying Currents and the Implications for Energy Dissipation

Abstract

Lee wave dissipation rates estimated from observations are two to three times lower than those predicted by models. However, such models have assumed a constant background current into which the waves propagate. To explore the impact of depth-varying currents on lee waves, I have run idealized 2D numerical simulations with sinusoidal bathymetry and linearly varying currents. For both bottom- and surface-intensified currents, waves propagate to the surface when their frequency ($\Omega$) remains within the radiating range, $f<\Omega < N$. In contrast, waves reach an evanescent layer when their frequency is Doppler-shifted to the limits of the radiating range, namely a dissipative layer when $\Omega=f$ or an internal reflective layer when $\Omega=N$. All simulations are time-dependent, with the generation of inertial oscillations and interference patterns when reflection occurs. Furthermore, depth-varying currents allow for energy exchanges, a dominant feature of wave energetics.