Last-glacial-cycle glacier erosion potential in the Alps

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.

Debris Cover Limits Subglacial Erosion and Promotes Till Accumulation

“…Sediment can also reside in the alpine landscapes for extended periods due to landslide damming (Korup et al., 2010) and sedimentation in glacially‐carved bedrock lakes (e.g., Anselmetti et al., 2007). More generally, alpine sediment storage creates lags in sediment routing (Blöthe & Korup, 2013) and complicates the identification of links between glacial erosion and climate change (Jonell et al., 2018; Lai & Anders, 2021; Seguinot & Delaney, 2021).…”

Glacial Erosion Rates Determined at Vorab Glacier: Implications for the Evolution of Limestone Plateaus

“…Inheritance from before the LGM at Tsanfleuron was negligible. Although the same test was not performed at Vorab, the huge thickness of ice at Vorab (estimated to be several hundred meters) during the LGM [21,22] would, in principle, have similarly removed more than 2 m of bedrock and removed nearly all previously produced 36 Cl. All bedrock samples located inside the LIA extent, whose true exposure ages should range from about 170 years (just inside of the LIA moraine ridge) to zero years (samples which became ice-free only during the summer of sampling, 2018), have apparent exposure ages that are much too old (3.3-5.8 ka).…”

“…In the past, researchers focused more on direct measurements [13,14] at the bedrock-ice interface or sediment yield measurements in meltwater streams [15][16][17]. Modern research concentrates more on numerical models based on glacier dynamics [18][19][20][21][22]. In the last decades, cosmogenic nuclide techniques have been shown to offer a unique possibility of determining glacial erosion rates directly on freshly exposed, glacially polished surfaces [23][24][25][26].…”

Performance analysis of high-resolution ice sheet simulations

“…Numerical ice sheet (glacier) models with evolving ice geometry are now routinely used for addressing scientific questions such as quantification of future sea level rise from changes in the Antarctic (Seroussi and others, 2020) and Greenland (Goelzer and others, 2020) ice sheets, interpretation of the paleoglacial record (Weber and others, 2021), and evaluation of long-term glacial erosion rates (Seguinot and Delaney, 2021), among other applications. It is generally accepted that horizontal mesh (grid) cells must be smaller than about 10 km in order to generate valid results, but narrow outlet glacier flows need yet finer resolution.…”

“…It is generally accepted that horizontal mesh (grid) cells must be smaller than about 10 km in order to generate valid results, but narrow outlet glacier flows need yet finer resolution. Whether using local mesh refinement (Fischler and others, 2022;Hoffman and others, 2018, for example) or not, resolutions of two or one kilometers (Seguinot and Delaney, 2021) or less (Aschwanden and others, 2019) are increasingly used for science at ice sheet scale.…”