Determination of the spatial snow and _rn layering on Rhonegletscher using Ground Penetrating Radar
Student : Felix Bissig
Supervisor: Dr. Andreas Bauder, Laboratory of Hydraulics, Hydrology and Glaciology
Co-Supervisor: Prof. Dr. Hansruedi Maurer, Institute of Geophysics
Ground Penetrating Radar (GPR) is a suitable tool to measure spatial distribution of snow accumulation of a glacier in order to determine its mass balance (e.g. Sold et al. 2013). In the framework of this thesis, ground-based GPR was used along a common offset profile on Rhonegletscher. After data processing and time to depth conversion with a constant velocity, internal reflection horizons visible in the GPR sections could be interpreted. This year’s snow accumulation could be assessed by combining 1000MHz GPR data and manual snow depth soundings. Small-scale features are better resolved by depth soundings, whereas GPR is able to track dielectric interfaces continuously along an entire profile. Firn layering is difficult to be interpreted correctly due to lack of absolute identification of past summer’s surfaces and an overly simple velocity model used in this thesis. Internal reflection horizons were interpreted as past summer’s surfaces because of their structural appearances in the 500MHz GPR sections. The thinning of annual firn layers over the years represents compaction and primarily ablation in the summer after snow deposition. Past accumulation rates can be estimated out of thickness of firn layers. Lowering of past summer’s surfaces with time is mainly influenced by ice ow and to a lesser extent by compaction. While interpreting evolution of past summer’s surfaces, changes in level of acquisition should be corrected for.