[A-OS11] Ocean Mixing Frontiers

[AOS11-06] Turbulent mixing variability in an energetic standing meander of the Southern Ocean

*Ajitha Cyriac^1,2, Helen Phillips^1,3, Nathan Bindoff^1,3, Kurt Polzin⁴ (1.IMAS, University of Tasmania, Hobart, Australia, 2.ARCCSS, Hobart, Australia, 3.AAPP, Hobart, Australia, 4.WHOI, Woods Hole, USA)

Keywords:Turbulent mixing, Internal waves

Turbulent mixing is a crucial mechanism that controls the distribution of heat, salt, sediments and organisms throughout the world oceans. It also plays an important role in driving large-scale oceanic processes such as watermass transformation, overturning circulation and stratification. Here we present mixing estimates from field observations of a standing meander near the Macquarie ridge, a major topographic obstacle for the Antarctic Circumpolar Current (ACC). It is a region of high eddy kinetic energy and interior upwelling. We collected more than 1400 profiles of temperature, salinity and velocity of the upper ocean using state of the art Electromagnetic Autonomous Profiling Explorer (EM-APEX) profiling floats in the upper 1600 m. By applying a finescale parameterization, we estimated the spatial and temporal variability of diapycnal mixing along the float tracks and investigated the sources. Elevated turbulent mixing is mostly associated with regions of subantarctic front and mesoscale eddies. In the upper layers, wind-generated downward propagating near-inertial waves dominate the enhanced mixing. The mixing is also high in cyclonic eddies associated with upward propagating internal waves. The dissipation rate estimates over rough and smooth topography has similar magnitudes suggesting that topography plays less role in mixing the upper 1600 m.