Ocean circulation beneath Larsen C Ice Shelf, Antarctica from in situ observations

Abstract

Hot‐water drilled access holes were used to obtain oceanographic data from beneath two sites on Larsen C Ice Shelf, one in the north and one in the south. At both sites the entire water column was colder than the surface freezing point, and the temperature‐salinity characteristics are consistent with a High Salinity Shelf Water source of maximum salinity 34.65 psu. At the southern site the 0.08°C thermal driving at the ice base and the 0.2‐m s−1 rms water speed resulted in a melt rate of 1.3 ± 0.2 m a−1, as measured over an eight‐day period. When combined with the available ship‐based data, the evidence suggests that the sub‐ice cavity is flushed only by water at the surface freezing point. This implies that the reported decrease in surface elevation of Larsen C Ice Shelf is unlikely to be a result of thinning due to an increasing rate of basal melting.