Radar attenuation demonstrates advective cooling in the Siple Coast ice streams
Abstract Ice streams are warmed by shear strain, both vertical shear near the bed and lateral shear at the margins. Warm ice deforms more easily, establishing a positive feedback loop in an ice stream where fast flow leads to warm ice and then to even faster flow. Here, we use radar attenuation meas...
Published in: | Journal of Glaciology |
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Cambridge University Press (CUP)
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Online Access: | http://dx.doi.org/10.1017/jog.2022.86 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143022000867 |
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crcambridgeupr:10.1017/jog.2022.86 2024-09-15T17:59:54+00:00 Radar attenuation demonstrates advective cooling in the Siple Coast ice streams Hills, Benjamin H. Christianson, Knut Jacobel, Robert W. Conway, Howard Pettersson, Rickard National Science Foundation 2022 http://dx.doi.org/10.1017/jog.2022.86 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143022000867 en eng Cambridge University Press (CUP) http://creativecommons.org/licenses/by/4.0/ Journal of Glaciology volume 69, issue 275, page 566-576 ISSN 0022-1430 1727-5652 journal-article 2022 crcambridgeupr https://doi.org/10.1017/jog.2022.86 2024-08-21T04:04:40Z Abstract Ice streams are warmed by shear strain, both vertical shear near the bed and lateral shear at the margins. Warm ice deforms more easily, establishing a positive feedback loop in an ice stream where fast flow leads to warm ice and then to even faster flow. Here, we use radar attenuation measurements to show that the Siple Coast ice streams are colder than previously thought, which we hypothesize is due to along-flow advection of cold ice from upstream. We interpret the attenuation results within the context of previous ice-temperature measurements from nearby sites where hot-water boreholes were drilled. These in-situ temperatures are notably colder than model predictions, both in the ice streams and in an ice-stream shear margin. We then model ice temperature using a 1.5-dimensional numerical model which includes a parameterization for along-flow advection. Compared to analytical solutions, we find depth-averaged temperatures that are colder by 0.7°C in the Bindschadler Ice Stream, 2.7°C in the Kamb Ice Stream and 6.2–8.2°C in the Dragon Shear Margin of Whillans Ice Stream, closer to the borehole measurements at all locations. Modelled cooling corresponds to shear-margin thermal strengthening by 3–3.5 times compared to the warm-ice case, which must be compensated by some other weakening mechanism such as material damage or ice-crystal fabric anisotropy. Article in Journal/Newspaper Bindschadler Ice Stream Journal of Glaciology Kamb Ice Stream Whillans Ice Stream Cambridge University Press Journal of Glaciology 1 11 |
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Open Polar |
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Cambridge University Press |
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crcambridgeupr |
language |
English |
description |
Abstract Ice streams are warmed by shear strain, both vertical shear near the bed and lateral shear at the margins. Warm ice deforms more easily, establishing a positive feedback loop in an ice stream where fast flow leads to warm ice and then to even faster flow. Here, we use radar attenuation measurements to show that the Siple Coast ice streams are colder than previously thought, which we hypothesize is due to along-flow advection of cold ice from upstream. We interpret the attenuation results within the context of previous ice-temperature measurements from nearby sites where hot-water boreholes were drilled. These in-situ temperatures are notably colder than model predictions, both in the ice streams and in an ice-stream shear margin. We then model ice temperature using a 1.5-dimensional numerical model which includes a parameterization for along-flow advection. Compared to analytical solutions, we find depth-averaged temperatures that are colder by 0.7°C in the Bindschadler Ice Stream, 2.7°C in the Kamb Ice Stream and 6.2–8.2°C in the Dragon Shear Margin of Whillans Ice Stream, closer to the borehole measurements at all locations. Modelled cooling corresponds to shear-margin thermal strengthening by 3–3.5 times compared to the warm-ice case, which must be compensated by some other weakening mechanism such as material damage or ice-crystal fabric anisotropy. |
author2 |
National Science Foundation |
format |
Article in Journal/Newspaper |
author |
Hills, Benjamin H. Christianson, Knut Jacobel, Robert W. Conway, Howard Pettersson, Rickard |
spellingShingle |
Hills, Benjamin H. Christianson, Knut Jacobel, Robert W. Conway, Howard Pettersson, Rickard Radar attenuation demonstrates advective cooling in the Siple Coast ice streams |
author_facet |
Hills, Benjamin H. Christianson, Knut Jacobel, Robert W. Conway, Howard Pettersson, Rickard |
author_sort |
Hills, Benjamin H. |
title |
Radar attenuation demonstrates advective cooling in the Siple Coast ice streams |
title_short |
Radar attenuation demonstrates advective cooling in the Siple Coast ice streams |
title_full |
Radar attenuation demonstrates advective cooling in the Siple Coast ice streams |
title_fullStr |
Radar attenuation demonstrates advective cooling in the Siple Coast ice streams |
title_full_unstemmed |
Radar attenuation demonstrates advective cooling in the Siple Coast ice streams |
title_sort |
radar attenuation demonstrates advective cooling in the siple coast ice streams |
publisher |
Cambridge University Press (CUP) |
publishDate |
2022 |
url |
http://dx.doi.org/10.1017/jog.2022.86 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143022000867 |
genre |
Bindschadler Ice Stream Journal of Glaciology Kamb Ice Stream Whillans Ice Stream |
genre_facet |
Bindschadler Ice Stream Journal of Glaciology Kamb Ice Stream Whillans Ice Stream |
op_source |
Journal of Glaciology volume 69, issue 275, page 566-576 ISSN 0022-1430 1727-5652 |
op_rights |
http://creativecommons.org/licenses/by/4.0/ |
op_doi |
https://doi.org/10.1017/jog.2022.86 |
container_title |
Journal of Glaciology |
container_start_page |
1 |
op_container_end_page |
11 |
_version_ |
1810437015580180480 |