Constrains on glacial erosion in the alps

Project Summary

Glaciers are strong agents of erosion and play a key role in the evolution of mountain ranges. In order to improve our understanding of the influence of glacial erosion dynamics on landscape evolution and mountain building, it is essential to quantify glacial erosion rates across multiple topographic and climatic settings.

In situ cosmogenic 10Be concentrations measured in river sediments have been widely used over the last twenty years to infer denudation rates integrated at the catchment scale. This approach was mainly applied to fluvial settings because, in this case, the 10Be concentration of detrital sediments is a simple function of denudation. In regions covered by glaciers, river sediments result from a mixture of materials produced in the pure fluvial domain and sediments produced by glacier erosion. The 10Be concentration measured in such settings thus results from the mixture of these two sources. Here, we use a simple mass conservation approach to estimate pure glacial erosion rates from the 10Be concentration measured in watersheds combining glacial and fluvial domains. In practice, we first established an empirical power law linking denudation rates to mean slope of non-glaciated catchments. For each partially glaciated catchment, this law was used to constrain the pure fluvial 10Be end-member using slopes derived from a DEM. Finally, this input was used to compute the pure glacial erosion rate required to satisfy the 10Be concentration measured in rivers

We apply this approach to determine erosion of modern glaciers across the entire Alps. We used previously published 10Be concentrations measured in river sediments covering partially glaciated watersheds. The fluvial denudation power law was constrained from 148 fluvial – glacier free catchments. Inclusion criteria of our dataset are basins with glaciers bigger than 5 km2 and covering at least 5% of the basin. The so-obtained glacial erosion rates from 11 watersheds range from 0.2 to 1.5 mm.yr-1. Finally, we compare those values to satellite-derived glaciers' sliding velocities which is thought to be the main factor controlling glacial erosion rates.

Scientific Results

First results from this project were presented at EGU 2022 in Vienna