Turbulence Signature of a Cold-Water Plume from below the Nansen Ice Shelf – an Autonomous Underwater Glider Survey

One of the largest contributors to ice shelf mass loss is the turbulent interaction of cold meltwater with warm seawater below the ice in complex basal channels. While such channels are relatively common in both the Arctic and Antarctic, the largest struggle with obtaining accurate estimates of relevant mixing parameters in proximity to basal channels is the extreme logistical difficulties in reaching such remote and inaccessible environments. However, recently developed autonomous technologies have finally made such an investigation possible. In January 2019, a Slocum autonomous underwater glider with a Rockland Scientific MicroRider turbulence probe returned estimates of energy dissipation (along with CTD data) along the calving front as well as directly below the Nansen Ice Shelf in Terra Nova Bay, Antarctica. This ground-breaking deployment successfully located and characterized a substantial cold-water plume flowing out from below the Nansen. Here, we present the turbulence signature of this plume, including elevated energy dissipation rates (10^-7 W/kg) in proximity to the coldest water. The dynamics of this plume provide insight into the movement of meltwater originating from the ice shelf’s grounding line and the nearby Dragalski Ice Tongue. Such below-ice autonomous surveys have great potential to contribute to the next generation of ice shelf melt models by gathering vital measurements of previously unconstrained oceanographic parameters.