Thermally driven migration of ice-stream shear margins
Abstract Ice-stream shear margins are the lateral boundaries of narrow, fast-flowing bands of ice within an ice sheet. We develop a theory for the migration of shear margins over time driven by viscous dissipation of heat within the ice, focusing on widening of the ice stream. The location of the ma...
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crcambridgeupr:10.1017/jfm.2012.438 2024-03-03T08:45:26+00:00 Thermally driven migration of ice-stream shear margins Schoof, Christian 2012 http://dx.doi.org/10.1017/jfm.2012.438 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022112012004387 en eng Cambridge University Press (CUP) https://www.cambridge.org/core/terms Journal of Fluid Mechanics volume 712, page 552-578 ISSN 0022-1120 1469-7645 Mechanical Engineering Mechanics of Materials Condensed Matter Physics journal-article 2012 crcambridgeupr https://doi.org/10.1017/jfm.2012.438 2024-02-08T08:25:39Z Abstract Ice-stream shear margins are the lateral boundaries of narrow, fast-flowing bands of ice within an ice sheet. We develop a theory for the migration of shear margins over time driven by viscous dissipation of heat within the ice, focusing on widening of the ice stream. The location of the margin is modelled as a transition from a cold to a temperate ice-sheet bed, and simultaneously as the transition from no slip to free slip at the same location. The temperature field in the ice is affected by intense shear heating as well as by the migration velocity of the margin (i.e. by the widening rate of the ice stream); if migration is too fast, there is little time for the ice to warm up and the margin remains cold, causing the bed to freeze. This suppresses widening. Conversely, if the migration speed is too slow, the ice in the margin warms up, causing the bed on the far side of the cold–temperate transition to reach the melting point, and migration to speed up. Using a Wiener–Hopf method, we show that for a given far-field shear stress, geothermal heat flux, and ice geometry, there is a single migration velocity that balances the two effects and permits widening at a steady rate. This velocity increases with the far-field lateral shear stress imposed by the ice stream, which controls shear heating in the margin. Our results also indicate that (i) a region of temperate ice must form in the margin, and that (ii) lateral advection of ice may play a significant role in controlling migration speeds. Article in Journal/Newspaper Ice Sheet Cambridge University Press Journal of Fluid Mechanics 712 552 578 |
institution |
Open Polar |
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Cambridge University Press |
op_collection_id |
crcambridgeupr |
language |
English |
topic |
Mechanical Engineering Mechanics of Materials Condensed Matter Physics |
spellingShingle |
Mechanical Engineering Mechanics of Materials Condensed Matter Physics Schoof, Christian Thermally driven migration of ice-stream shear margins |
topic_facet |
Mechanical Engineering Mechanics of Materials Condensed Matter Physics |
description |
Abstract Ice-stream shear margins are the lateral boundaries of narrow, fast-flowing bands of ice within an ice sheet. We develop a theory for the migration of shear margins over time driven by viscous dissipation of heat within the ice, focusing on widening of the ice stream. The location of the margin is modelled as a transition from a cold to a temperate ice-sheet bed, and simultaneously as the transition from no slip to free slip at the same location. The temperature field in the ice is affected by intense shear heating as well as by the migration velocity of the margin (i.e. by the widening rate of the ice stream); if migration is too fast, there is little time for the ice to warm up and the margin remains cold, causing the bed to freeze. This suppresses widening. Conversely, if the migration speed is too slow, the ice in the margin warms up, causing the bed on the far side of the cold–temperate transition to reach the melting point, and migration to speed up. Using a Wiener–Hopf method, we show that for a given far-field shear stress, geothermal heat flux, and ice geometry, there is a single migration velocity that balances the two effects and permits widening at a steady rate. This velocity increases with the far-field lateral shear stress imposed by the ice stream, which controls shear heating in the margin. Our results also indicate that (i) a region of temperate ice must form in the margin, and that (ii) lateral advection of ice may play a significant role in controlling migration speeds. |
format |
Article in Journal/Newspaper |
author |
Schoof, Christian |
author_facet |
Schoof, Christian |
author_sort |
Schoof, Christian |
title |
Thermally driven migration of ice-stream shear margins |
title_short |
Thermally driven migration of ice-stream shear margins |
title_full |
Thermally driven migration of ice-stream shear margins |
title_fullStr |
Thermally driven migration of ice-stream shear margins |
title_full_unstemmed |
Thermally driven migration of ice-stream shear margins |
title_sort |
thermally driven migration of ice-stream shear margins |
publisher |
Cambridge University Press (CUP) |
publishDate |
2012 |
url |
http://dx.doi.org/10.1017/jfm.2012.438 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022112012004387 |
genre |
Ice Sheet |
genre_facet |
Ice Sheet |
op_source |
Journal of Fluid Mechanics volume 712, page 552-578 ISSN 0022-1120 1469-7645 |
op_rights |
https://www.cambridge.org/core/terms |
op_doi |
https://doi.org/10.1017/jfm.2012.438 |
container_title |
Journal of Fluid Mechanics |
container_volume |
712 |
container_start_page |
552 |
op_container_end_page |
578 |
_version_ |
1792500988890841088 |