Current, temperature, and salinity beneath George VI Ice Shelf, Antarctica

Speed, direction, temperature, and conductivity were recorded from February to July 1980 within the thermocline near the northern ice front of George VI Ice Shelf. There were no significant changes in temperature or salinity from summer to winter. Fluctuations of around 10 and 40 days periodicity were observed in the current and temperature, and similar variations are evident in meteorological observations. Temperature oscillations were observed at tidal frequencies and may be caused by horizontal advection or internal wave motion. The horizontal kinetic energy is dominated by low-frequency periods (46%), semi-diurnal tides (40%), and diurnal tides (10%). Tidal ellipses have their major axes aligned along George VI Sound and are described anticlockwise. Terdiurnal constituents, which may be a particular effect in the response of a floating ice shelf to tide generating forces, were observed. The M2 constituent was highly suppressed. Both the amplitude of M2 current and the speed of the mean flow decreased sharply in mid-April. These changes may be related to increasing sea-ice cover with the onset of winter. The mean flow is directed eastwards across the narrow channel, parallel to the ice front and at right angles to the major axes of the tidal ellipses. We speculate on reasons for this unusual behaviour.