Hydraulic properties of subglacial sediment determined from the mechanical response of water-filled boreholes
Abstract Freezing of water-filled boreholes drives water into the subglacial bed and the associated pressure effects yield information about subglacial hydraulic properties. A numerical model describing the mechanical response of an unconnected borehole and the bed beneath it to this freezing forcin...
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Language: | English |
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Cambridge University Press (CUP)
1995
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Online Access: | http://dx.doi.org/10.1017/s0022143000017810 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143000017810 |
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crcambridgeupr:10.1017/s0022143000017810 2024-03-03T08:46:01+00:00 Hydraulic properties of subglacial sediment determined from the mechanical response of water-filled boreholes Waddington, Brian S. Clarke, Garry K. C. 1995 http://dx.doi.org/10.1017/s0022143000017810 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143000017810 en eng Cambridge University Press (CUP) Journal of Glaciology volume 41, issue 137, page 112-124 ISSN 0022-1430 1727-5652 Earth-Surface Processes journal-article 1995 crcambridgeupr https://doi.org/10.1017/s0022143000017810 2024-02-08T08:34:04Z Abstract Freezing of water-filled boreholes drives water into the subglacial bed and the associated pressure effects yield information about subglacial hydraulic properties. A numerical model describing the mechanical response of an unconnected borehole and the bed beneath it to this freezing forcing was developed, using a nonlinear transient visco-elastic ice-flow law and an approximate model of top-down freezing. The resulting system of equations was solved using the method of lines. Results agreed well with analytic solutions, when parameters were correctly chosen. Forward modelling of pressure records from three 1992 boreholes and three from other years indicated that the till underlying Trapridge Glacier has a hydraulic conductivity of 1.35-7.0 × 10 −9 m s −1 . The model was also used to investigate the response of a borehole to sudden pressure changes. The response is very fast compared to pressure-sensor sampling rates; thus, the true basal signal is essentially unaffected by the presence of the borehole, except during the initial freeze-in. Article in Journal/Newspaper Journal of Glaciology Cambridge University Press Trapridge Glacier ENVELOPE(-140.337,-140.337,61.233,61.233) Journal of Glaciology 41 137 112 124 |
institution |
Open Polar |
collection |
Cambridge University Press |
op_collection_id |
crcambridgeupr |
language |
English |
topic |
Earth-Surface Processes |
spellingShingle |
Earth-Surface Processes Waddington, Brian S. Clarke, Garry K. C. Hydraulic properties of subglacial sediment determined from the mechanical response of water-filled boreholes |
topic_facet |
Earth-Surface Processes |
description |
Abstract Freezing of water-filled boreholes drives water into the subglacial bed and the associated pressure effects yield information about subglacial hydraulic properties. A numerical model describing the mechanical response of an unconnected borehole and the bed beneath it to this freezing forcing was developed, using a nonlinear transient visco-elastic ice-flow law and an approximate model of top-down freezing. The resulting system of equations was solved using the method of lines. Results agreed well with analytic solutions, when parameters were correctly chosen. Forward modelling of pressure records from three 1992 boreholes and three from other years indicated that the till underlying Trapridge Glacier has a hydraulic conductivity of 1.35-7.0 × 10 −9 m s −1 . The model was also used to investigate the response of a borehole to sudden pressure changes. The response is very fast compared to pressure-sensor sampling rates; thus, the true basal signal is essentially unaffected by the presence of the borehole, except during the initial freeze-in. |
format |
Article in Journal/Newspaper |
author |
Waddington, Brian S. Clarke, Garry K. C. |
author_facet |
Waddington, Brian S. Clarke, Garry K. C. |
author_sort |
Waddington, Brian S. |
title |
Hydraulic properties of subglacial sediment determined from the mechanical response of water-filled boreholes |
title_short |
Hydraulic properties of subglacial sediment determined from the mechanical response of water-filled boreholes |
title_full |
Hydraulic properties of subglacial sediment determined from the mechanical response of water-filled boreholes |
title_fullStr |
Hydraulic properties of subglacial sediment determined from the mechanical response of water-filled boreholes |
title_full_unstemmed |
Hydraulic properties of subglacial sediment determined from the mechanical response of water-filled boreholes |
title_sort |
hydraulic properties of subglacial sediment determined from the mechanical response of water-filled boreholes |
publisher |
Cambridge University Press (CUP) |
publishDate |
1995 |
url |
http://dx.doi.org/10.1017/s0022143000017810 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143000017810 |
long_lat |
ENVELOPE(-140.337,-140.337,61.233,61.233) |
geographic |
Trapridge Glacier |
geographic_facet |
Trapridge Glacier |
genre |
Journal of Glaciology |
genre_facet |
Journal of Glaciology |
op_source |
Journal of Glaciology volume 41, issue 137, page 112-124 ISSN 0022-1430 1727-5652 |
op_doi |
https://doi.org/10.1017/s0022143000017810 |
container_title |
Journal of Glaciology |
container_volume |
41 |
container_issue |
137 |
container_start_page |
112 |
op_container_end_page |
124 |
_version_ |
1792501805939163136 |