Snow Accumulation on Rhonegletscher

Snow and firn accumulation on Rhonegletscher using ground-penetrating radar

Student : Cédric Berger

Supervisor: Andreas Bauder and Hansruedi Maurer

Winter mass balance measurements are essential for the separation of the mass balance components. For a high spatial coverage, ground-penetrating radar (GPR) offers a high-resolution geophysical approach for imaging the depth structure of mountain glaciers. GPR uses reflections of high-frequency electromagnetic waves to image changes in dielectric properties in the subsurface. These changes are related to density contrasts in the subsurface. In this study, GPR data of a 500MHz antenna pair provide insight into the snow and firn layers of the Rhonegletscher. After data processing, firn layers are assigned to their year of accumulation. The result is a 7.6km long two-dimensional profile which reveals a nine-year-old history of firn evolution within the shallow subsurface. Furthermore, the comparison of the GPR data to traditional snow depth sounding measurements enables to obtains the exact geometry of the last summer surface. Based on two snow density measurements, we derive the water equivalent of the snow cover. The water equivalent evaluations allow temporal comparisons of winter mass balances between the years 2015-2017. The results show that the winter mass balance of 2017 is about 10% lower compared to the previous years.