Modelling subglacial erosion and englacial sediment transport of the North American ice sheets
The glacial geology of North America is a rich resource upon which reconstructions of ice sheets are made. Numerical modelling of ice sheets based on ice physics is an alternate avenue for cryospheric reconstruction. However, such algorithms are unable to draw from the full wealth of geomorphic data...
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The University of British Columbia
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ftdatacite:10.14288/1.0052346 2023-05-15T16:35:33+02:00 Modelling subglacial erosion and englacial sediment transport of the North American ice sheets Hildes, Dave Henry Degast 2002 https://dx.doi.org/10.14288/1.0052346 https://doi.library.ubc.ca/10.14288/1.0052346 en eng The University of British Columbia PhysicalObject CreativeWork ArchivalObject article 2002 ftdatacite https://doi.org/10.14288/1.0052346 2021-11-05T12:55:41Z The glacial geology of North America is a rich resource upon which reconstructions of ice sheets are made. Numerical modelling of ice sheets based on ice physics is an alternate avenue for cryospheric reconstruction. However, such algorithms are unable to draw from the full wealth of geomorphic data because a large-scale forward model of basal processes, necessary to link the ice and the bed, is not available. I develop a process-based model of sediment production, entrainment, deposition and transport to fill this conspicuous gap. Subglacial abrasion is modelled following Hallet [1979, 1981] and a quarrying model, dependent on subcritical crack growth, is constructed. Entrainment proceeds predominantly by intrusion into the sediment [Iverson and Semmens, 1995] and when basal melt exceeds the rate of entrainment, englacial sediment is deposited. Both vertical redistribution of englacial sediment within an ice column and lateral transport of debris is considered. Ice entrains loose debris from the bed, transports it downstream and deposits an allochthonous debris train, observable on the modern landscape. This can be modelled when an accurate geologic representation of the bed is used, allowing the exploitation of distinct lithologies as natural tracers of ice motion. Also, incorporation of the differences in physical properties between various lithologies is possible with such a lithologically realistic description of the bed. Several processes are functions of bed topography and a description of small-scale topography within a large-scale grid is required; a downscaling method is therefore developed. Basal-ice processes must be coupled to both ice sheet conditions and subglacial hydrology. The Marshall-Clarke thermo-mechanicalice sheet model [Marshall, 1996; Marshall and Clarke, 1997a,b; Marshall et al., 2000] gives the necessary ice sheet fields and provides the forcing for the hydrology model of Flowers [2000] which in turn delivers subglacial water pressure, used for both the quarrying and entrainment simulations. Comparisons of model results with the documented large-scale debris trains of Hudson Bay Paleozoic sedimentary rocks and Dubawnt Group detritus are used to test the veracity of the transport model while estimates of paleo-erosion are used to assess the erosion model. Article in Journal/Newspaper Hudson Bay Ice Sheet DataCite Metadata Store (German National Library of Science and Technology) Hudson Bay Hudson Hallet ENVELOPE(6.662,6.662,63.003,63.003) |
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Open Polar |
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DataCite Metadata Store (German National Library of Science and Technology) |
op_collection_id |
ftdatacite |
language |
English |
description |
The glacial geology of North America is a rich resource upon which reconstructions of ice sheets are made. Numerical modelling of ice sheets based on ice physics is an alternate avenue for cryospheric reconstruction. However, such algorithms are unable to draw from the full wealth of geomorphic data because a large-scale forward model of basal processes, necessary to link the ice and the bed, is not available. I develop a process-based model of sediment production, entrainment, deposition and transport to fill this conspicuous gap. Subglacial abrasion is modelled following Hallet [1979, 1981] and a quarrying model, dependent on subcritical crack growth, is constructed. Entrainment proceeds predominantly by intrusion into the sediment [Iverson and Semmens, 1995] and when basal melt exceeds the rate of entrainment, englacial sediment is deposited. Both vertical redistribution of englacial sediment within an ice column and lateral transport of debris is considered. Ice entrains loose debris from the bed, transports it downstream and deposits an allochthonous debris train, observable on the modern landscape. This can be modelled when an accurate geologic representation of the bed is used, allowing the exploitation of distinct lithologies as natural tracers of ice motion. Also, incorporation of the differences in physical properties between various lithologies is possible with such a lithologically realistic description of the bed. Several processes are functions of bed topography and a description of small-scale topography within a large-scale grid is required; a downscaling method is therefore developed. Basal-ice processes must be coupled to both ice sheet conditions and subglacial hydrology. The Marshall-Clarke thermo-mechanicalice sheet model [Marshall, 1996; Marshall and Clarke, 1997a,b; Marshall et al., 2000] gives the necessary ice sheet fields and provides the forcing for the hydrology model of Flowers [2000] which in turn delivers subglacial water pressure, used for both the quarrying and entrainment simulations. Comparisons of model results with the documented large-scale debris trains of Hudson Bay Paleozoic sedimentary rocks and Dubawnt Group detritus are used to test the veracity of the transport model while estimates of paleo-erosion are used to assess the erosion model. |
format |
Article in Journal/Newspaper |
author |
Hildes, Dave Henry Degast |
spellingShingle |
Hildes, Dave Henry Degast Modelling subglacial erosion and englacial sediment transport of the North American ice sheets |
author_facet |
Hildes, Dave Henry Degast |
author_sort |
Hildes, Dave Henry Degast |
title |
Modelling subglacial erosion and englacial sediment transport of the North American ice sheets |
title_short |
Modelling subglacial erosion and englacial sediment transport of the North American ice sheets |
title_full |
Modelling subglacial erosion and englacial sediment transport of the North American ice sheets |
title_fullStr |
Modelling subglacial erosion and englacial sediment transport of the North American ice sheets |
title_full_unstemmed |
Modelling subglacial erosion and englacial sediment transport of the North American ice sheets |
title_sort |
modelling subglacial erosion and englacial sediment transport of the north american ice sheets |
publisher |
The University of British Columbia |
publishDate |
2002 |
url |
https://dx.doi.org/10.14288/1.0052346 https://doi.library.ubc.ca/10.14288/1.0052346 |
long_lat |
ENVELOPE(6.662,6.662,63.003,63.003) |
geographic |
Hudson Bay Hudson Hallet |
geographic_facet |
Hudson Bay Hudson Hallet |
genre |
Hudson Bay Ice Sheet |
genre_facet |
Hudson Bay Ice Sheet |
op_doi |
https://doi.org/10.14288/1.0052346 |
_version_ |
1766025790906957824 |