Helicopter-borne and ground-towed radar surveys of the Fourcade Glacier on King George Island, Antarctica

To determine subglacial topography and internal features of the Fourcade Glacier on King George Island in
Antarctica, helicopter-borne and ground-towed ground-penetrating radar (GPR) data were recorded along four profiles in
November 2006. Signature deconvolution, f-k migration velocity analysis, and finite-difference depth migration applied to the
mixed-phase, single-channel, ground-towed data, were effective in increasing vertical resolution, obtaining the velocity
function, and yielding clear depth images, respectively. For the helicopter-borne GPR, migration velocities were obtained as
root-mean-squared velocities in a two-layer model of air and ice. The radar sections show rugged subglacial topography,
englacial sliding surfaces, and localised scattering noise. The maximum depth to the basement is over 79m in the subglacial
valley adjacent to the south-eastern slope of the divide ridge between Fourcade and Moczydlowski Glaciers.
In the groundtowed
profile,weinterpret a complicated conduit above possible basal water and other isolated cavities, which are a few metres
wide. Near the terminus, the GPR profiles image sliding surfaces, fractures, and faults that will contribute to the tidewater
calving mechanism forming icebergs in Potter Cove.