Last-glacial-cycle glacier erosion potential in the Alps

Julien Seguinot,Ian Delaney

doi:10.5194/esurf-9-923-2021

Abstract

Abstract. The glacial landscape of the Alps has fascinated generations of explorers, artists, mountaineers, and scientists with its diversity, including erosional features of all scales from high-mountain cirques to steep glacial valleys and large overdeepened basins. Using previous glacier modelling results and empirical inferences of bedrock erosion under modern glaciers, we compute a distribution of potential glacier erosion in the Alps over the last glacial cycle from 120 000 years ago to the present. Despite large uncertainties pertaining to the climate history of the Alps and unconstrained glacier erosion processes, the resulting modelled patterns of glacier erosion include persistent features. The cumulative imprint of the last glacial cycle shows a very strong localization of erosion potential with local maxima at the mouths of major Alpine valleys and some other upstream sections where glaciers are modelled to have flowed with the highest velocity. The potential erosion rates vary significantly through the glacial cycle but show paradoxically little relation to the total glacier volume. Phases of glacier advance and maximum extension see a localization of rapid potential erosion rates at low elevation, while glacier erosion at higher elevation is modelled to date from phases of less extensive glaciation. The modelled erosion rates peak during deglaciation phases, when frontal retreat results in steeper glacier surface slopes, implying that climatic conditions that result in rapid glacier erosion might be quite transient and specific. Our results depict the Alpine glacier erosion landscape as a time-transgressive patchwork, with different parts of the range corresponding to different glaciation stages and time periods.

Highlights

The glacial erosion landscape of the Alps has fascinated generations of explorers, artists, mountaineers, and scientists for centuries
While mountain cirque glaciers and relevant erosion processes may not be captured by the model physics and horizontal resolution, high cumulative erosion potential occurs near the valley heads
There is a general tendency for higher cumulative erosion in the north-western Alps where the input winter precipitation is higher (WorldClim; Fig. 1h in Seguinot et al, 2018) and the glacial relief more pronounced in the topography

Summary

Introduction

The glacial erosion landscape of the Alps has fascinated generations of explorers, artists, mountaineers, and scientists for centuries. Penck, 1905), present a higher variety of glacier erosional landforms, whose implications for glacial history are yet to be understood. In parallel to such landscape diversity, the cosmogenic nuclide memory of bedrock erosion provides a more quantitative but varied picture of glacier erosion effectiveness both within and between glaciated regions (Jansen et al, 2019; Steinemann et al, 2020, 2021). It remains elusive whether glacial topography is a proxy for temperate ice-cover duration and why some glaciated regions show preserved periglacial block-

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Discussion

Conclusion