Interpretation of Mono-Pulse Ice Radar Soundings on Two Peruvian Glaciers

During the 1979 and 1980 field seasons, mono-pulse radar sounding experiments were carried out on the Quelccaya Ice Cap in southern Peru and the col of Huascarán in northern Peru. Along with ice thickness determinations, some of which are described in detail elsewhere (the maximum ice thickness measured using the radar was 165 ± 20 m for the Quelccaya Ice Cap and 190 ± 10 m for Huascarán), studies were conducted to estimate the average temperature of the glaciers and the character of the glacier beds using the measured amplitudes and phases of the radar data. Values for the electrical properties of ice needed to model absorption in the ice reflection amplitudes at the ice base were compiled from the literature and extrapolated down to 5 MHz. An ambiguity in the interpretation of the radar data, regarding the relative contributions of reflection and absorption losses to the total attenuation, could only be resolved by including additional independent information about the glaciers such as 15-m temperatures and evidence for sliding around the perimeter. We conclude from these data that both the Quelccaya Ice Cap and the col of Huascarán are temperate glaciers which are dry-based near their summits and, in the case of Quelccaya, wet-based near the margin.