Dielectric variability of a 130 m Antarctic ice core: implications for radar sounding

A 130 m long ice core has been dielectrically profiled. From an analysis of the measurements, we obtain a profile of the high-frequency (radio-echo) conductivity. This profile has been represented by a simplified 700 layer model. The model has layers of differing conductivities, permittivities and thicknesses. A reflection-coefficient log can be calculated, assuming that permittivity is a smooth function of depth. Variations in conductivity are shown to be more likely sources of internal reflections from depths greater than a few hundred metres than changes in permittivity caused by density changes. The log is convoluted with input pulses of various frequencies and pulse lengths in order to produce synthetic radargrams. These show features that correspond to the internal reflections typically seen when radio echo-sounding polar ice sheets.