Experimental constraints on subglacial rock friction
Abstract Subglacial rock friction is an important control on the sliding dynamics and erosive potential of hard-bedded glaciers, yet it remains largely unconstrained. To explore the relative influence of basal melt rate, effective stress and ice temperature on frictional resistance, we conducted abr...
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Online Access: | http://dx.doi.org/10.1017/aog.2019.47 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0260305519000478 |
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crcambridgeupr:10.1017/aog.2019.47 2024-09-30T14:22:45+00:00 Experimental constraints on subglacial rock friction Hansen, Dougal D. Zoet, Lucas K. 2019 http://dx.doi.org/10.1017/aog.2019.47 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0260305519000478 en eng Cambridge University Press (CUP) http://creativecommons.org/licenses/by/4.0/ Annals of Glaciology volume 60, issue 80, page 37-48 ISSN 0260-3055 1727-5644 journal-article 2019 crcambridgeupr https://doi.org/10.1017/aog.2019.47 2024-09-04T04:04:45Z Abstract Subglacial rock friction is an important control on the sliding dynamics and erosive potential of hard-bedded glaciers, yet it remains largely unconstrained. To explore the relative influence of basal melt rate, effective stress and ice temperature on frictional resistance, we conducted abrasion experiments in which limestone beds were slid beneath a fixed slab of ice laden with granitic rock fragments. Shear stress scales linearly with melt rate and cryostatic stress, confirming that both viscous drag and effective stress are first-order controls on the contact force in drained conditions. Furthermore, temperature gradients in the ice increase the contribution of viscous drag on basal shear stress. In all experiments, the relationship between melt rate and shear stress is best explained by a model that accounts for the effects of regelation and viscous creep on the bed-normal drag force. We interpret this to mean fluid flow around entrained clasts contributed to basal drag even at subfreezing temperatures. Incorporating premelting dynamics into the Watts/Hallet model for subglacial rock friction, we find that the predicted debris-bed drag decreases by approximately an order of magnitude, with a corresponding ~3.5 × increase in the transition radius. This is lower than we observe for ice slightly below the pressure melting point. Article in Journal/Newspaper Annals of Glaciology Cambridge University Press Hallet ENVELOPE(6.662,6.662,63.003,63.003) Annals of Glaciology 60 80 37 48 |
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Open Polar |
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Cambridge University Press |
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crcambridgeupr |
language |
English |
description |
Abstract Subglacial rock friction is an important control on the sliding dynamics and erosive potential of hard-bedded glaciers, yet it remains largely unconstrained. To explore the relative influence of basal melt rate, effective stress and ice temperature on frictional resistance, we conducted abrasion experiments in which limestone beds were slid beneath a fixed slab of ice laden with granitic rock fragments. Shear stress scales linearly with melt rate and cryostatic stress, confirming that both viscous drag and effective stress are first-order controls on the contact force in drained conditions. Furthermore, temperature gradients in the ice increase the contribution of viscous drag on basal shear stress. In all experiments, the relationship between melt rate and shear stress is best explained by a model that accounts for the effects of regelation and viscous creep on the bed-normal drag force. We interpret this to mean fluid flow around entrained clasts contributed to basal drag even at subfreezing temperatures. Incorporating premelting dynamics into the Watts/Hallet model for subglacial rock friction, we find that the predicted debris-bed drag decreases by approximately an order of magnitude, with a corresponding ~3.5 × increase in the transition radius. This is lower than we observe for ice slightly below the pressure melting point. |
format |
Article in Journal/Newspaper |
author |
Hansen, Dougal D. Zoet, Lucas K. |
spellingShingle |
Hansen, Dougal D. Zoet, Lucas K. Experimental constraints on subglacial rock friction |
author_facet |
Hansen, Dougal D. Zoet, Lucas K. |
author_sort |
Hansen, Dougal D. |
title |
Experimental constraints on subglacial rock friction |
title_short |
Experimental constraints on subglacial rock friction |
title_full |
Experimental constraints on subglacial rock friction |
title_fullStr |
Experimental constraints on subglacial rock friction |
title_full_unstemmed |
Experimental constraints on subglacial rock friction |
title_sort |
experimental constraints on subglacial rock friction |
publisher |
Cambridge University Press (CUP) |
publishDate |
2019 |
url |
http://dx.doi.org/10.1017/aog.2019.47 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0260305519000478 |
long_lat |
ENVELOPE(6.662,6.662,63.003,63.003) |
geographic |
Hallet |
geographic_facet |
Hallet |
genre |
Annals of Glaciology |
genre_facet |
Annals of Glaciology |
op_source |
Annals of Glaciology volume 60, issue 80, page 37-48 ISSN 0260-3055 1727-5644 |
op_rights |
http://creativecommons.org/licenses/by/4.0/ |
op_doi |
https://doi.org/10.1017/aog.2019.47 |
container_title |
Annals of Glaciology |
container_volume |
60 |
container_issue |
80 |
container_start_page |
37 |
op_container_end_page |
48 |
_version_ |
1811635381377957888 |