Ice thickness measurements of the Erebus Ice Tongue by radio echo sounder

The Erebus Ice Tongue breaks off near its mid point in single regular calving events at about 30 year intervals. A number of studies have been made on the growth rate, mass balance, ice physics and regimes in general. More recent studies include surface mass balance, measurement of strain and some ice thickness measurements by radio-echo sounder. This event visited the ice tongue to a) check ice thickness measurements with a radio echo sounder against those made by other methods, b) ascertain the nature of radio echo sounder reflections of ice over seawater and of perhaps wet based glacier ice and of dry base glacier ice, c) attempt to locate the position of the hinge line of the tongue and d) determine the subglacial topography close to the shore line to determine whether a deep narrow channel is responsible for the unique extrusion of the tongue. Ice thickness measurements by radio-echo sounding equipment were made over the full length of the Erebus Ice Tongue at established pole sties and the soundings were continued inland in a circuit around the neve. Some 20 soundings were made and their positions fixed by survey.