On the Role of Mechanical Energy in Maintaining Subglacial Water Conduits at Atmospheric Pressure
Abstract Recent theoretical studies of glacier hydrology have assumed that subglacial conduits are completely filled with water under steady-state conditions. This, however, is not necessarily the case. Where discharges are larger than a few tens of liters per second and the down-glacier slope of th...
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Cambridge University Press (CUP)
1984
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Online Access: | http://dx.doi.org/10.1017/s0022143000005918 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143000005918 |
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crcambridgeupr:10.1017/s0022143000005918 2023-06-11T04:13:27+02:00 On the Role of Mechanical Energy in Maintaining Subglacial Water Conduits at Atmospheric Pressure Hooke, Roger Leb. 1984 http://dx.doi.org/10.1017/s0022143000005918 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143000005918 en eng Cambridge University Press (CUP) Journal of Glaciology volume 30, issue 105, page 180-187 ISSN 0022-1430 1727-5652 Earth-Surface Processes journal-article 1984 crcambridgeupr https://doi.org/10.1017/s0022143000005918 2023-05-01T18:19:49Z Abstract Recent theoretical studies of glacier hydrology have assumed that subglacial conduits are completely filled with water under steady-state conditions. This, however, is not necessarily the case. Where discharges are larger than a few tens of liters per second and the down-glacier slope of the bed is more than a few degrees, the potential energy released by water descending this slope may be capable of melting the walls of a subglacial conduit many times faster than the conduit can close by plastic flow of the ice. As a result, the pressure in such tunnels may normally be atmospheric, or possibly even at the triple-point pressure if there is no open connection to the glacier surface. Simple calculations suggest that such pressures in subglacial conduits may be more common than heretofore anticipated. The positions of such “open” conduits may be unstable to small perturbations in discharge or ice velocity. This is because the mechanical energy available in excess of that needed to balance closure can instead offset the general flow of the ice. Conduits can thus trend diagonally across the direction of ice flow. If an increase in the angle which such a conduit makes with the ice flow direction also results in an increase in slope of the conduit, more mechanical energy will become available, resulting in a positive feedback process. Subglacial channels at atmospheric pressure may influence the origin and morphology of certain glacial landforms, such as eskers and “plastically-molded” features. Article in Journal/Newspaper Journal of Glaciology Cambridge University Press (via Crossref) Journal of Glaciology 30 105 180 187 |
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Cambridge University Press (via Crossref) |
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crcambridgeupr |
language |
English |
topic |
Earth-Surface Processes |
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Earth-Surface Processes Hooke, Roger Leb. On the Role of Mechanical Energy in Maintaining Subglacial Water Conduits at Atmospheric Pressure |
topic_facet |
Earth-Surface Processes |
description |
Abstract Recent theoretical studies of glacier hydrology have assumed that subglacial conduits are completely filled with water under steady-state conditions. This, however, is not necessarily the case. Where discharges are larger than a few tens of liters per second and the down-glacier slope of the bed is more than a few degrees, the potential energy released by water descending this slope may be capable of melting the walls of a subglacial conduit many times faster than the conduit can close by plastic flow of the ice. As a result, the pressure in such tunnels may normally be atmospheric, or possibly even at the triple-point pressure if there is no open connection to the glacier surface. Simple calculations suggest that such pressures in subglacial conduits may be more common than heretofore anticipated. The positions of such “open” conduits may be unstable to small perturbations in discharge or ice velocity. This is because the mechanical energy available in excess of that needed to balance closure can instead offset the general flow of the ice. Conduits can thus trend diagonally across the direction of ice flow. If an increase in the angle which such a conduit makes with the ice flow direction also results in an increase in slope of the conduit, more mechanical energy will become available, resulting in a positive feedback process. Subglacial channels at atmospheric pressure may influence the origin and morphology of certain glacial landforms, such as eskers and “plastically-molded” features. |
format |
Article in Journal/Newspaper |
author |
Hooke, Roger Leb. |
author_facet |
Hooke, Roger Leb. |
author_sort |
Hooke, Roger Leb. |
title |
On the Role of Mechanical Energy in Maintaining Subglacial Water Conduits at Atmospheric Pressure |
title_short |
On the Role of Mechanical Energy in Maintaining Subglacial Water Conduits at Atmospheric Pressure |
title_full |
On the Role of Mechanical Energy in Maintaining Subglacial Water Conduits at Atmospheric Pressure |
title_fullStr |
On the Role of Mechanical Energy in Maintaining Subglacial Water Conduits at Atmospheric Pressure |
title_full_unstemmed |
On the Role of Mechanical Energy in Maintaining Subglacial Water Conduits at Atmospheric Pressure |
title_sort |
on the role of mechanical energy in maintaining subglacial water conduits at atmospheric pressure |
publisher |
Cambridge University Press (CUP) |
publishDate |
1984 |
url |
http://dx.doi.org/10.1017/s0022143000005918 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143000005918 |
genre |
Journal of Glaciology |
genre_facet |
Journal of Glaciology |
op_source |
Journal of Glaciology volume 30, issue 105, page 180-187 ISSN 0022-1430 1727-5652 |
op_doi |
https://doi.org/10.1017/s0022143000005918 |
container_title |
Journal of Glaciology |
container_volume |
30 |
container_issue |
105 |
container_start_page |
180 |
op_container_end_page |
187 |
_version_ |
1768390493924753408 |