Abstract:We will present preliminary results from geophysical and glaciological measurements on Potsdam Glacier, south of the Schirmacher Oasis, Central Dronning Maud Land, East Antarctica.The data were retrieved during the Antarctic summer season 2003/2004 and consist of ground penetrating radar (GPR) surveys as well as shallow firn cores and snow pits.The GPR surveys were carried out using a central frequency of 500 MHz on the main flow line of Potsdam Glacier and perpendicular to that line. The total length of the GPR profiles was about 100 km, thus covering an area of ca. 400 km2 . Traces were recorded each 0.5 m and the time window was chosen such that the upper 25-30 m of the snow pack could be covered in high resolution.The processed radar data show several internal reflection horizons indicating a change of density (or conductivity) in the subsurface.These horizons were traced throughout the profiles and will be dated by the results of the firn core analyses.The firn cores were drilled at five locations on the radar profile lines, each core being 12-13 m in length. At the same locations snow pits were digged with a depth of 2 m and a sampling interval of 5cm, giving 40 snow samples per pit.On the firn cores dielectric profiling measurements were carried out in the laboratory to determine the real part of the dielectric permittivity and the conductivity. Furthermore the density was measured as well as the content of oxygen isotope, δ18O. From the snow samples density and δ18O were determined as well.Combining the geophysical and glaciologicaldata sets gives information about the accumulation pattern and internal structures in the upper snowpack. From the firn core data models were derived giving an estimation of the distribution of the radar velocity with depth. Using these models the radar data can be converted from traveltime- to depth-sections so the depths of the different horizons are known. Furthermore mass-depth relations were established yielding information about tht cumulative snow mass for the respective radar detected layers.Δ18O-peaks in the firn core data indicating summer times help to derive annual cycles covered by the firn cores.Comparing the depths of the radar horizons with the dated firn cores allows dating of the horizons. From the cumulative snow mass of the different reflection horizons and their respective ages the mean accumulation along the radar survey lines can be estimated.So the combination of geophysical and glaciological studies provides a powerfull tool for the determination of the accumulation pattern. On Potsdam Glacier the data indicate a high spatial variability of accumulation rate along the main flow line.
Helmholtz Research Programs > MARCOPOLI (2004-2008) > POL6-Earth climate variability since the Pliocene