By John M. Reynolds
Managing Director, Reynolds International Ltd., and Co-founder of the Glacier and Permafrost Hazards Working Group, U.K.
Non-invasive imaging of land through ice sheets has provided huge steps forward in the mapping and understanding of these features since the 1950s. Historically, airborne Radio-Echo Sounding (RES) has been undertaken over cold dry polar ice sheets, which are virtually transparent to radiowaves, and depths of investigation of up to 5 km are not unknown. Since then, developments in radar equipment and analytical techniques have enabled the derivation of other significant information about the structure, composition, layering and dynamics of these major ice masses and related physical processes. The first use of impulse radar (Ground Penetrating Radar, GPR) for glaciological purposes was in the early 1970s. Since the mid-1990s, there has been huge growth in the use of commercial GPR systems in particular over temperate glaciers, which are at their pressure melting point. RES systems were first deployed from large aircraft in Polar Regions. GPR systems were originally used in ground-based investigations of temperate glaciers and have been used with increasing benefit in similar ways in Polar Regions. However, GPR systems are now being mounted onto helicopters for use in rugged mountain environments, such as in the European Alps and the Indian Himalaya. By examining the radar characteristics of key glaciological features in both Polar and Himalayan regions it is possible to design optimal radar surveys for a variety of glaciological applications. Such surveys, such as may be undertaken in the Indian Himalaya, can produce information that is key to climate change monitoring, measuring glacier volume fluxes, enhanced mass balance estimations, and that forms a high-quality baseline against which changes over time can be measured.
Introduction The investigation of Polar ice sheets using radio-waves (Radio-Echo Sounding – RES) from aircraft began in earnest in the early 1960s and led to major steps forward in the mapping of such features, with the discovery of whole mountain ranges buried beneath the ice. Analysis of reflections within the ice itself provides important information about the structure and dynamics of the ice sheets. The use of large aircraft has been critical to cover large areas of otherwise inaccessible...