Basal Water and High-Pressure Basal Ice
Abstract Expressions are found for the water pressure in channels and cavities under a temperate glacier in a steady state. By steady state is meant that not only is the sliding velocity constant but also the basal water flow as well as the basal water production. The calculations are based on a sim...
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Cambridge University Press (CUP)
1986
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Online Access: | http://dx.doi.org/10.1017/s002214300001217x https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S002214300001217X |
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crcambridgeupr:10.1017/s002214300001217x 2024-03-03T08:46:04+00:00 Basal Water and High-Pressure Basal Ice Weertman, J. 1986 http://dx.doi.org/10.1017/s002214300001217x https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S002214300001217X en eng Cambridge University Press (CUP) Journal of Glaciology volume 32, issue 112, page 455-463 ISSN 0022-1430 1727-5652 Earth-Surface Processes journal-article 1986 crcambridgeupr https://doi.org/10.1017/s002214300001217x 2024-02-08T08:39:08Z Abstract Expressions are found for the water pressure in channels and cavities under a temperate glacier in a steady state. By steady state is meant that not only is the sliding velocity constant but also the basal water flow as well as the basal water production. The calculations are based on a simplified bimodal obstacle bed. One-size obstacles are of the magnitude of the conventional “controlling” obstacles size. The other obstacle size is several orders of magnitude larger than the controlling size. The large obstacles are introduced in order to investigate the storage of large amounts of water at the bed. The effect of the missing obstacles is mimicked by adding a friction stress whose values decrease linearly with ice–rock separation. It is found that water flow is primarily in a water film if the water flux is below a critical limit. The physical reason for this result is that a minimum water flow must be exceeded in order to keep a water channel open in high ice-pressure regions in front of obstacles. The new ingredient in our analysis of water flow is the explicit account taken of the effect of excess ice pressure (at the up-stream side of obstacles) on the closing of water channels. The excess ice-pressure regions play a critical role in the development of water films. The recognition of the possible importance of high-pressure basal ice regions to the regulation of water flow is the primary result of this paper. It is found that, in steady state, the water pressure is close to the overburden ice pressure provided that water transported through Nye channels is only a minor part of the total. The water flows primarily in a water film. If a large flux of upper-surface melt water descends to the bed, this water could cause a reduction of the water pressure and a channelization of the water flow. Article in Journal/Newspaper Journal of Glaciology Cambridge University Press Journal of Glaciology 32 112 455 463 |
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Open Polar |
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Cambridge University Press |
op_collection_id |
crcambridgeupr |
language |
English |
topic |
Earth-Surface Processes |
spellingShingle |
Earth-Surface Processes Weertman, J. Basal Water and High-Pressure Basal Ice |
topic_facet |
Earth-Surface Processes |
description |
Abstract Expressions are found for the water pressure in channels and cavities under a temperate glacier in a steady state. By steady state is meant that not only is the sliding velocity constant but also the basal water flow as well as the basal water production. The calculations are based on a simplified bimodal obstacle bed. One-size obstacles are of the magnitude of the conventional “controlling” obstacles size. The other obstacle size is several orders of magnitude larger than the controlling size. The large obstacles are introduced in order to investigate the storage of large amounts of water at the bed. The effect of the missing obstacles is mimicked by adding a friction stress whose values decrease linearly with ice–rock separation. It is found that water flow is primarily in a water film if the water flux is below a critical limit. The physical reason for this result is that a minimum water flow must be exceeded in order to keep a water channel open in high ice-pressure regions in front of obstacles. The new ingredient in our analysis of water flow is the explicit account taken of the effect of excess ice pressure (at the up-stream side of obstacles) on the closing of water channels. The excess ice-pressure regions play a critical role in the development of water films. The recognition of the possible importance of high-pressure basal ice regions to the regulation of water flow is the primary result of this paper. It is found that, in steady state, the water pressure is close to the overburden ice pressure provided that water transported through Nye channels is only a minor part of the total. The water flows primarily in a water film. If a large flux of upper-surface melt water descends to the bed, this water could cause a reduction of the water pressure and a channelization of the water flow. |
format |
Article in Journal/Newspaper |
author |
Weertman, J. |
author_facet |
Weertman, J. |
author_sort |
Weertman, J. |
title |
Basal Water and High-Pressure Basal Ice |
title_short |
Basal Water and High-Pressure Basal Ice |
title_full |
Basal Water and High-Pressure Basal Ice |
title_fullStr |
Basal Water and High-Pressure Basal Ice |
title_full_unstemmed |
Basal Water and High-Pressure Basal Ice |
title_sort |
basal water and high-pressure basal ice |
publisher |
Cambridge University Press (CUP) |
publishDate |
1986 |
url |
http://dx.doi.org/10.1017/s002214300001217x https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S002214300001217X |
genre |
Journal of Glaciology |
genre_facet |
Journal of Glaciology |
op_source |
Journal of Glaciology volume 32, issue 112, page 455-463 ISSN 0022-1430 1727-5652 |
op_doi |
https://doi.org/10.1017/s002214300001217x |
container_title |
Journal of Glaciology |
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32 |
container_issue |
112 |
container_start_page |
455 |
op_container_end_page |
463 |
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1792501941395259392 |