Abstract
Direct measurements of dissipation rates in the Southern Ocean unveiled a deficit of lee-wave dissipation compared to lee-wave generation (Brearley et al. 2013; Sheen et al. 2013; Waterman et al. 2013, 2014; Cusack et al. 2017, 2020), which is described as “suppression of turbulence” in Waterman et al. (2014). One possible explanation is the generation of freely propagating internal gravity waves (free waves with Eulerian frequency 𝜔𝐸 ≠ 0) that can radiate outside of the lee-wave critical layer and dissipate remotely. In a numerical simulation of lee waves generated by a localized, stable geostrophic current over sinusoidal topography, free waves are observed to emanate from the lee-wave critical layer. The escaped fraction of free-wave energy (the fraction that tunnels through the lee-wave critical layer and reaches the upper ocean) is 5%, while the majority remains trapped.