Oral Presentation AMOS Annual Meeting and International Conference on Tropical Meteorology and Oceanography

Downstream propagation and remote dissipation of internal waves in the Southern Ocean (#271)

Maxim Nikurashin 1 , Kaiwen Zheng 1
  1. University of Tasmania, Hobart, TAS, Australia

Recent microstructure observations in the Southern Ocean report enhanced internal gravity waves and turbulence in the frontal regions of the Antarctic Circumpolar Current extending a kilometre above rough bottom topography. Idealised numerical simulations and linear theory show that geostrophic flows impinging on rough small-scale topography are very effective generators of internal waves and predict vigorous wave radiation, breaking, and turbulence within a kilometre above bottom. However, both idealised simulations and linear theory assume periodic and spatially uniform topography and tend to overestimate the observed levels of turbulent energy dissipation locally at the generation sites. In this study, we explore the downstream evolution and remote dissipation of internal waves generated by geostrophic flows using a series of numerical, realistic topography simulations and parameters typical of Drake Passage. The results show that significant levels of internal wave kinetic energy and energy dissipation are present downstream of the rough topography, internal wave generation site. About 30-40% of the energy dissipation occurs locally over the rough topography region, where internal waves are generated. The rest of the energy dissipation takes place remotely and decays downstream of the generation site with an e-folding length scale of up to 30km. The implications of these results for turbulent energy dissipation observations and mixing parameterisations are discussed.