Internal Waves, Turbulence and Mixing in the Antarctic Circumpolar Current

Andreas M Thurnherr, Lamont-Doherty Earth Observatory, Palisades, NY, United States, Yvonne Firing, National Oceanography Center, Soton, Southampton, United Kingdom, Teresa K Chereskin, SIO/UCSD, La Jolla, CA, United States and Stephanie Waterman, University of British Columbia, Department of Earth, Ocean and Atmospheric Sciences, Vancouver, BC, Canada
The Southern Ocean is the nexus of the global overturning circulation, with the Antarctic Circumpolar Current (ACC) providing an unblocked advective pathway connecting the major ocean basins, and hot spots of energetic internal waves, turbulence and mixing re-distributing buoyancy and passive tracers between different water masses. Here we report results from an NSF-funded project aiming to synthesize internal-wave and turbulence observations in the ACC region with the eventual goal of deriving a climatology of internal-wave and turbulence properties for the Southern Ocean. Primarily using data from 15 yearly repeat occupations of the SR1b British LADCP/CTD section across Drake Passage we previously showed (2018 AGU Fall Meeting) that, when the data from several repeat occupations are averaged, many fundamental internal-wave properties --- shear, strain, vertical kinetic energy (VKE), the shear-to-strain variance ratio, parameterized dissipation --- show well-defined spatial patterns but that these patterns are largely obscured in single section occupations. Our updated analysis covers additional parameters, including the so-called rotary coefficient, vertical convergence (which is equal to horizontal divergence) from the LADCP, as well as the spectral slopes in wavenumber space of several finestructure quantities, which have recently been shown to affect the performance of shear/strain finestructure parameterizations. The primary focus of the work presented at the OSM is the temporal variability of internal-wave properties across Drake Passage, in particular with respect to the modulation of internal waves by the near-bottom velocities in the ACC.