Abstract

Turbulent mixing on the west Antarctic Peninsula shelf is a highly important process, being responsible both for delivering ocean heat to the melting glaciers of the region, and for supplying nutrients to the biologically productive surface layers. Despite this, literature estimates of the turbulent diffusivity and the associated heat fluxes vary by up to an order of magnitude, and direct estimates of mixing are extremely sparse.

In this talk, we document and discuss two separate pieces of fieldwork aimed at understanding both the magnitude of mixing at the Rothera Time Series (RaTS) site, and its controlling processes. Whilst overall heat fluxes through the pycnocline at the site are relatively modest (~1 W m-2), shear instabilities in the water column arise by different mechanisms during periods when fast ice is absent or present. Whilst the diurnal tides are important in generating velocity shear year-round, a significant input of wind-driven near-inertial energy into the ocean during the fast-ice-free months is responsible for generating turbulent motions. We will also discuss the most recent microstructure estimates of turbulent diffusivity obtained in February 2016 from Ryder Bay, and discuss how the results compare to finestructure-based estimates of turbulent dissipation.