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Abstract:
Debris on glaciers is sourced by the erosion of the surrounding ice-free rockwalls. Where the supply of debris relative to that of snow is high, glaciers tend to develop a significant debris cover, which influences their surface mass balance. Therefore, changes in rockwall erosion and, thus, the debris supply to glaciers will also influence the surface mass balance and the response of glaciers to climate change. However, estimated rockwall erosion rates in glacierized catchments are rare and very little is known about spatial and temporal variations. We summarize results from the COLD (Climate Sensitivity of Glacial Landscape Dynamics) project that provide new insights into rockwall erosion rates from glacierized catchments in the European Alps. We will first focus on the debris source areas and present (1) decadal-scale, remote sensing-derived thermal conditions, and (2) centennial- to millennial-scale cosmogenic nuclide-derived erosion rates. We will then take a closer look at (3) the cosmogenic nuclide inventory of medial moraines, which reflect variations in source area erosion over temporally-discrete intervals. Our results provide quantitative estimates of long-term erosion rates, and suggest not only spatial but also significant temporal variations in the debris supply to glaciers, probably induced by climate warming and permafrost thaw.
