Heterogeneous Mixing Processes Observed in the Dotson Ice Shelf Outflow, Antarctica

Abstract

We present the first observations of ocean turbulent mixing rate in front of the Dotson Ice Shelf, where meltwater-enriched water leaves the cavity. The observations showed elevated turbulent kinetic energy dissipation rates ($\epsilon$; ∼10⁻⁷ W kg⁻¹) and turbulent diapycnal diffusivities ($\kappa$; ∼10⁻² m² s⁻¹) near the seabed and in middepth layers, which are three orders of magnitude above background values away from the outflow. Elevated diapycnal fluxes of heat and salt were observed in regions of high mixing, moving vertically on average O ∼ 10 W m⁻² and O ∼ 10⁻⁶ kg m⁻² s⁻¹, respectively, toward shallow depths. At middepth layers, the overturning instabilities are characterized by shear-driven symmetric and centrifugal instabilities. Our observations provide an understanding of mixing in front of fast-melting ice shelves and are key to developing better parameterizations and representations of mixing in climate models.