Stratigraphic profiling of antarctic firn with 400-MHz GPR at 1500 ns

The firn regime of Antarctica extends 60-100 m deep and contains at least the last 200 years of snow deposition. As part of a program to study the influence of industrialization on antarctic climate and glacial mass balance, I have acquired about 3000 km of profiles of the stratigraphy of this regime in West Antarctica using 400-MHz GPR. Here, sections of these deeper profiles are presented to show the performance that can be achieved with commercial-grade radar in polar firn and to show some of the horizon characteristics. The profiles show 1) distinct reflections that are probably thin layer responses, 2) deepest penetration to about 130 m, 3) long-distance horizon continuity (as great as 500 km), and 4) folding caused by tectonic compression. The continuity, the increase of reflection strength with depth, and the slow variation of strength with distance suggest that the reflections are caused by chemical impurities and not density contrasts. Continuity will improve with faster trace acquisition. Resolution may not improve at higher frequencies because horizons may blur from antenna motion and horizon irregularities.