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Abstract:
The Dotson Ice Shelf, which abuts the warm waters of Antarctica’s Amundsen Sea, has exhibited high rates of ocean-driven basal melting in recent decades. As part of the UK-US ITGC collaboration, we surveyed the ice front using a vertical microstructure profiler (VMP) and two ocean gliders equipped with shear and temperature microstructure probes, as well as an ordinary conductivity-temperature sensor. Closely spaced (~1 km horizontal resolution) profiles in the principal in- and outflow regions were collected using the VMP, while the gliders conducted a series of near-zonal sections along the ice front over a three-week period. The glider sections reveal a concentrated inflow, 10 km across, of Circumpolar Deep Water in the east; outflow is concentrated in the west, but occurs over the remainder of the 40 km section. Estimates of turbulent kinetic energy dissipation rate, ε, from shear and temperature, and from gliders and the VMP, generally agree to within an order of magnitude. High values of ε (10-8 to 10-7 W kg-1) are observed at the sea floor in the inflow region, a result of bottom friction, and throughout the water column in the principal outflow region. In the centre of the section, ε is lower (10-11 to 10-10 W kg-1), but for a region of elevated ε at the interface between Circumpolar Deep Water and the Winter Water that overlies it. We also calculate horizontal heat transports and, from ε, turbulent vertical heat fluxes, key quantities for understanding the influence of the ocean on basal melting.
