Spatial and temporal variations of glacial erosion in the Rhône valley (Swiss Alps): Insights from numerical modeling

- Estimates of glacial erosion on the pre-glacial and present-day Rhône valley.
- Glacial conditioning evolves in time, also depending on the landscape morphology.
- Initial increase of relief followed by erosion at high elevation during glaciation.
- Headward propagation of glacial erosion through time.
- Possible intensification of glacial erosion at the middle Pleistocene transition.

The present-day topography of the European Alps shows evidence of intense glacial reshaping. However, significant questions regarding Alpine landscape evolution during glaciations still persist. In this study, we focus on the Rhône valley (Swiss Alps), and use a numerical model to estimate patterns and magnitudes of glacial erosion. Comparing modeling results on a reconstructed pre-glacial topography and the present-day landforms, we find that the landscape response to glaciation is more complex than a simple “buzzsaw” mechanism (by which glacial erosion sets the height of mountain ranges) or increase of relief due to localized valley incision. Instead, glacial erosion propagates headward as the landforms evolve from a fluvial to a glacial state, leading to an initial increase of local relief followed by subsequent erosion at high elevations. It has also been proposed that the mid-Pleistocene climatic transition of glacial/interglacial oscillations from periods of 40 kyr (with symmetric shapes) to periods of 100 kyr (with asymmetric shapes) promoted glacial erosion within the Alps. Although this change of climate periodicity may have contributed to enhance glacial erosion, our results suggest that other factors such as an increase in rock uplift and/or progressive climate cooling are required to explain enhanced glacial carving at ~1Ma.