Double diffusion as a driver of turbulence in the stratified boundary layer beneath George VI Ice Shelf

Warmer and more persistent intrusions of Circumpolar Deep Water (CDW) onto the West Antarctic Peninsula are a key driver of the recent increase in ice shelf mass loss. The relatively warm and salty CDW is thought to be mixed up to the base of the ice shelves via shear-driven turbulence where it has a high capacity to melt the ice. We analyze data from a year-long mooring beneath George VI Ice Shelf at a location where double-diffusive layering was observed. The turbulent dissipation rates do not vary with mean flow speed, suggesting shear-driven mixing is not the driver of basal melt at this site. Instead, we predict the observed dissipation using a new method that links along-isopycnal stirring of temperature anomalies with double-diffusive convection. Our work suggests that along-isopycnal temperature variance may be a stronger indicator of melt than flow speed within strongly stratified ice shelf-ocean boundary layers.

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