The impact of glaciers on mountain erosion

Herman, Frédéric; Doncker, Fien De; Delaney, Ian; Prasicek, Günther; Koppes, Michèle

doi:10.1038/s43017-021-00165-9

Cited by 61 publications

(50 citation statements)

References 193 publications

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“…k g is an erodability constant and l er is an exponent, which varies from between 0.66 and 3 (Herman et al, 2021). u b is assumed to be a given fraction f sl of the ice deformation velocity (e.g.…”

Section: ∂H ∂Tmentioning

confidence: 99%

“…For instance, erosive processes likely dominate over sediment transport processes on glaciers with minimal sediment storage and steep gradients (Humphrey and Raymond, 1994;Herman et al, 2015Herman et al, , 2021. Furthermore, landscape evolution models, that use empirical relationships to quantify erosion with respect to sliding speed, demonstrate the dominant role of erosional processes, as opposed to sediment transport ones, over geologic timescales (Harbor et al, 1988;Herman et al, 2011;Egholm et al, 2012).…”

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confidence: 99%

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The spatially distributed nature of subglacial sediment dynamics: using a numerical model to quantify sediment transport and bedrock erosion across a glacier bed in response to glacier behavior and hydrology

Delaney¹,

Anderson

Herman³

2021

Preprint

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Abstract. In addition to ice and water, glaciers expel sediment. As a result, changing glacier dynamics and melt will result in changes to glacier erosion and sediment discharge, which can impact the landscape surrounding retreating glaciers, as well as communities and ecosystems downstream. To date, the available models of subglacial sediment transport on the sub-hourly to decadal-scale exist in one dimension, usually along a glacier's flow line. Such models have proven useful in describing the formation of landforms, the impact of sediment transport on glacier dynamics, the interactions between climate, glacier dynamics, and erosion. However, because of the large role of sediment connectivity in determining sediment discharge, the geoscience community needs modeling frameworks that describe subglacial sediment discharge in two spatial dimensions over time. Here, we present SUGSET_2D, a numerical model that evolves a two-dimensional subglacial till layer in response to the erosion of bedrock and changing sediment transport conditions below the glacier. Experiments employed on test cases of synthetic ice sheets and alpine glaciers demonstrate the heterogeneity in sediment transport across a glacier's bed. Furthermore, the experiments show the non-linear increase in sediment discharge following increased glacier melt. Lastly, we apply the model to Griesgletscher in the Swiss Alps where we use a parameter search to test model outputs against annual observations of sediment discharge measured from the glacier. The model captures the glacier's inter-annual variability and quantities of sediment discharge. Furthermore, the model's capacity to represent the data depends greatly on the grain size of sediment. Smaller sediment sizes allow sediment transport to occur in regions of the bed with reduced water flow and channel size, effectively increasing sediment connectivity into the main channels. Model outputs from the three test-cases together show the importance of considering heterogeneities in water discharge and sediment availability in two dimensions.

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Section: ∂H ∂Tmentioning

confidence: 99%

mentioning

confidence: 99%

The spatially distributed nature of subglacial sediment dynamics: using a numerical model to quantify sediment transport and bedrock erosion across a glacier bed in response to glacier behavior and hydrology

Delaney¹,

Anderson

Herman³

2021

Preprint

Self Cite

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“…More detailed information about paleoclimate conditions would moreover improve our understanding of glacier response(s) to current climate change as well as our ability to anticipate glacier evolutions for proposed future climate scenarios (Zemp et al, 2006;Haeberli et al, 2020). Furthermore, direct temperature constraints associated with paleoglacier variations are also critical to our understanding of glacier erosion processes (Hallet, 1979) which have profoundly shaped high-latitude and mountain landscapes over 10 3 to 10 6 yr timescales (Herman et al, 2021), and which seems to relate, among other factors, to climatic conditions (Koppes et al, 2015;Cook et al, 2020).…”

Section: Introductionmentioning

confidence: 99%

Cosmogenic <sup>3</sup>He paleothermometry on post-LGM glacial bedrock within the central European Alps

Gribenski

Tremblay

Valla

et al. 2022

Preprint

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Abstract. Diffusion properties of cosmogenic 3He in quartz at Earth’s surface temperatures offer the potential to reconstruct the evolution of past in-situ temperatures directly from formerly glaciated areas, information important for improving our understanding of glacier-climate interactions. In this study, we apply cosmogenic 3He paleothermometry on rock surfaces gradually exposed since the Last Glacial Maximum (LGM) to the Holocene period along two deglaciation profiles in the European Alps (Mont Blanc and Aar massifs). Laboratory experiments conducted on one representative sample per site indicate significant variability in 3He diffusion kinetics between the two sites, with quasi linear Arrhenius behavior observed in quartz from the Mont Blanc site and complex Arrhenius behavior observed from the Aar site, which we interpret to indicate the presence of multiple diffusion domains (MDD). Assuming that same diffusion kinetics apply to all quartz samples along each profile, predictive simulations indicate that 3He abundance in all the investigated samples should be at equilibrium with present-day temperature conditions. However, measured natural 3He concentrations in samples exposed since before the Holocene indicate an apparent 3He thermal signal significantly colder than today. This observed 3He thermal signal cannot be explained with a realistic post-LGM mean annual temperature evolution in the European Alps at the study sites. One hypothesis is that the diffusion kinetics and MDD model applied may not provide sufficiently accurate, quantitative paleo-temperature estimates in these samples; thus, whereas pre-Holocene 3He thermal signal is indeed preserved in the quartz, the helium diffusivity would be lower at Alpine surface temperatures than our diffusion models predict. Alternatively, if the modeled helium diffusion kinetics is accurate, the observed 3He abundances may reflect complex geomorphic/paleoclimatic evolution with much more recent ground temperature changes associated with the degradation of alpine permafrost.

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“…For example, numerical ice-sheet models used to simulate past and future ice-sheet evolution typically rely on a basal sliding parameter that is sparsely constrained by empirical measurements (e.g., Cuzzone et al, 2018;Larour et al, 2012;Morlighem et al, 2010). Despite the importance of including basal processes in ice sheet models, comparatively less focus has been placed on measuring erosion rates beneath ice sheets than alpine glacier systems (e.g., Cook et al, 2020;Herman et al, 2021;Koppes et al, 2015) The Greenland Ice Sheet (GrIS) is of particular concern, as it exhibits sustained mass loss in response to modern warming (King et al, 2020), yet the rate at which subglacial erosion and sediment transport takes place beneath the ice sheet remains poorly constrained.…”

Section: Introductionmentioning

confidence: 99%

Centennial- and orbital-scale erosion beneath the Greenland Ice Sheet

Balter-Kennedy¹,

Young²,

Briner³

et al. 2021

Preprint

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Erosion beneath glaciers and ice sheets is a fundamental Earth-surface process dictating landscape development, which in turn influences ice-flow dynamics and the climate sensitivity of ice masses. The rate at which subglacial erosion takes place, however, is notoriously difficult to observe because it occurs beneath modern glaciers in a largely inaccessible environment. Here, we present 1) cosmogenic-nuclide measurements from bedrock surfaces with well constrained exposure and burial histories fronting Jakobshavn Isbræ in western Greenland to constrain centennial-scale erosion rates, and 2) a new method combining cosmogenic nuclide measurements in a shallow bedrock core with cosmogenic-nuclide modelling to constrain orbital-scale erosion rates across the same landscape. Twenty-six 10Be measurements in surficial bedrock constrain the erosion rate during historical times to 0.4–0.8 mm yr-1. Seventeen 10Be measurements in a 4-m-long bedrock core corroborate this centennial-scale erosion rate, and reveal that 10Be concentrations below ~2 m depth are greater than what is predicted by an idealized production-rate depth profile. We utilize this excess 10Be at depth to constrain orbital-scale erosion rates at Jakobshavn Isbræ to 0.1–0.3 mm yr-1. The broad similarity between centennial- and orbital-scale erosion rates suggests that subglacial erosion rates have remained relatively uniform throughout the Pleistocene at Jakobshavn Isbræ.

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The impact of glaciers on mountain erosion

Cited by 61 publications

References 193 publications

The spatially distributed nature of subglacial sediment dynamics: using a numerical model to quantify sediment transport and bedrock erosion across a glacier bed in response to glacier behavior and hydrology

The spatially distributed nature of subglacial sediment dynamics: using a numerical model to quantify sediment transport and bedrock erosion across a glacier bed in response to glacier behavior and hydrology

Cosmogenic <sup>3</sup>He paleothermometry on post-LGM glacial bedrock within the central European Alps

Centennial- and orbital-scale erosion beneath the Greenland Ice Sheet

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The impact of glaciers on mountain erosion

Cited by 61 publications

References 193 publications

The spatially distributed nature of subglacial sediment dynamics: using a numerical model to quantify sediment transport and bedrock erosion across a glacier bed in response to glacier behavior and hydrology

The spatially distributed nature of subglacial sediment dynamics: using a numerical model to quantify sediment transport and bedrock erosion across a glacier bed in response to glacier behavior and hydrology

Cosmogenic &lt;sup&gt;3&lt;/sup&gt;He paleothermometry on post-LGM glacial bedrock within the central European Alps

Centennial- and orbital-scale erosion beneath the Greenland Ice Sheet

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Resources

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Cosmogenic <sup>3</sup>He paleothermometry on post-LGM glacial bedrock within the central European Alps