A new approach to inferring basal drag and ice rheology in ice streams, with applications to West Antarctic Ice Streams
Abstract Drag at the bed and along the lateral margins are the primary forces resisting flow in outlet glaciers. Simultaneously inferring these parameters is challenging since basal drag and ice viscosity are coupled in the momentum balance, which governs ice flow. We test the ability of adjoint-bas...
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crcambridgeupr:10.1017/jog.2020.95 2024-09-15T17:47:37+00:00 A new approach to inferring basal drag and ice rheology in ice streams, with applications to West Antarctic Ice Streams Ranganathan, Meghana Minchew, Brent Meyer, Colin R. Gudmundsson, G. Hilmar 2020 http://dx.doi.org/10.1017/jog.2020.95 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143020000957 en eng Cambridge University Press (CUP) http://creativecommons.org/licenses/by/4.0/ Journal of Glaciology volume 67, issue 262, page 229-242 ISSN 0022-1430 1727-5652 journal-article 2020 crcambridgeupr https://doi.org/10.1017/jog.2020.95 2024-06-26T04:04:02Z Abstract Drag at the bed and along the lateral margins are the primary forces resisting flow in outlet glaciers. Simultaneously inferring these parameters is challenging since basal drag and ice viscosity are coupled in the momentum balance, which governs ice flow. We test the ability of adjoint-based inverse methods to infer the slipperiness coefficient in a power-law sliding law and the flow-rate parameter in the constitutive relation for ice using a regularization scheme that includes coefficients weighted by surface strain rates. Using synthetic data with spatial variations in basal drag and ice rheology comparable to those in West Antarctic Ice Streams, we show that this approach allows for more accurate inferences. We apply this method to Bindschadler and MacAyeal Ice Streams in West Antarctica. Our results show relatively soft ice in the shear margins and spatially varying basal drag, with an increase in drag with distance upstream of the grounding line punctuated by localized areas of relatively high drag. We interpret soft ice to reflect a combination of heating through viscous dissipation and changes in the crystalline structure. These results suggest that adjoint-based inverse methods can provide inferences of basal drag and ice rheology when regularization is informed by strain rates. Article in Journal/Newspaper Antarc* Antarctic Antarctica Journal of Glaciology West Antarctica Cambridge University Press Journal of Glaciology 67 262 229 242 |
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Open Polar |
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Cambridge University Press |
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crcambridgeupr |
language |
English |
description |
Abstract Drag at the bed and along the lateral margins are the primary forces resisting flow in outlet glaciers. Simultaneously inferring these parameters is challenging since basal drag and ice viscosity are coupled in the momentum balance, which governs ice flow. We test the ability of adjoint-based inverse methods to infer the slipperiness coefficient in a power-law sliding law and the flow-rate parameter in the constitutive relation for ice using a regularization scheme that includes coefficients weighted by surface strain rates. Using synthetic data with spatial variations in basal drag and ice rheology comparable to those in West Antarctic Ice Streams, we show that this approach allows for more accurate inferences. We apply this method to Bindschadler and MacAyeal Ice Streams in West Antarctica. Our results show relatively soft ice in the shear margins and spatially varying basal drag, with an increase in drag with distance upstream of the grounding line punctuated by localized areas of relatively high drag. We interpret soft ice to reflect a combination of heating through viscous dissipation and changes in the crystalline structure. These results suggest that adjoint-based inverse methods can provide inferences of basal drag and ice rheology when regularization is informed by strain rates. |
format |
Article in Journal/Newspaper |
author |
Ranganathan, Meghana Minchew, Brent Meyer, Colin R. Gudmundsson, G. Hilmar |
spellingShingle |
Ranganathan, Meghana Minchew, Brent Meyer, Colin R. Gudmundsson, G. Hilmar A new approach to inferring basal drag and ice rheology in ice streams, with applications to West Antarctic Ice Streams |
author_facet |
Ranganathan, Meghana Minchew, Brent Meyer, Colin R. Gudmundsson, G. Hilmar |
author_sort |
Ranganathan, Meghana |
title |
A new approach to inferring basal drag and ice rheology in ice streams, with applications to West Antarctic Ice Streams |
title_short |
A new approach to inferring basal drag and ice rheology in ice streams, with applications to West Antarctic Ice Streams |
title_full |
A new approach to inferring basal drag and ice rheology in ice streams, with applications to West Antarctic Ice Streams |
title_fullStr |
A new approach to inferring basal drag and ice rheology in ice streams, with applications to West Antarctic Ice Streams |
title_full_unstemmed |
A new approach to inferring basal drag and ice rheology in ice streams, with applications to West Antarctic Ice Streams |
title_sort |
new approach to inferring basal drag and ice rheology in ice streams, with applications to west antarctic ice streams |
publisher |
Cambridge University Press (CUP) |
publishDate |
2020 |
url |
http://dx.doi.org/10.1017/jog.2020.95 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143020000957 |
genre |
Antarc* Antarctic Antarctica Journal of Glaciology West Antarctica |
genre_facet |
Antarc* Antarctic Antarctica Journal of Glaciology West Antarctica |
op_source |
Journal of Glaciology volume 67, issue 262, page 229-242 ISSN 0022-1430 1727-5652 |
op_rights |
http://creativecommons.org/licenses/by/4.0/ |
op_doi |
https://doi.org/10.1017/jog.2020.95 |
container_title |
Journal of Glaciology |
container_volume |
67 |
container_issue |
262 |
container_start_page |
229 |
op_container_end_page |
242 |
_version_ |
1810497074006851584 |