Mountain glaciers store water in the form of ice and snow and can guarantee the water supply to thousands of communities living down-valley of the glaciers. Many glaciers in high altitude mountain ranges present surface debris-covers, which alter the meltwater supply and change the glacier behavior in response to climate conditions. Despite the increasing number and magnitude of debris-covered glaciers in most of the worlds mountain regions, debris thickness, and its variability in both time and space, is rarely accounted for in local and regional models for climate and cryosphere.
So far, the most widespread methods to measure the supraglacial debris thickness consist in digging pits and surveying exposures above ice cliffs. Both these techniques require great physical efforts, are subject to large sampling bias, and lead to single point discrete measurements. GPR is a versatile, non-invasive geophysical method, which produces high resolution, near-surface, pseudo-continuous data with a relatively small physical and economical efforts. This thesis aims to assess the use of Ground Penetrating Radar (GPR) as a method for investigating this hard-to-measure property of supraglacial debris thickness.
The data were collected on the Solda Glacier (Italy), where four areas characterized by different surface morphology and debris aspects were studied, with different frequency antenna (400, 600, 900, 1600 MHz). The GPR profiles were processed according to a straightforward processing flow and were coupled with precise positioning data.
A strong continuous reflector, interpreted as the debris-ice interface was widely identified, suggesting that GPR performs well to gain reliable information on supraglacial debris thickness, in particular for debris thicker than 0.15 cm. Debris thickness compares well to the debris thickness distribution obtained from direct measurements across the glacier but with a positive bias of 0.1 m, despite the variable data quality, caused by the presence of water and poor antennae connectivity over this type of glacier surface. The use of multiple frequencies allows the debris-ice interface to be located with greater precision, and also allows investigation of the nature of the sub-surface debris sources by distinguishing between debris-filled crevasses and medial moraine structures. This allows also a broader geomorphological interpretation about the conditions leading to the formation of the debris cover.