Inferred basal friction and mass flux affected by crystal-orientation fabrics
We investigate the errors caused by neglecting the crystal-orientation fabric when inferring the basal friction coefficient field, and whether such errors can be alleviated by inferring an isotropic enhancement factor field to compensate for missing fabric information. We calculate the steady states...
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Cambridge University Press (CUP)
2021
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Online Access: | http://dx.doi.org/10.1017/jog.2021.88 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143021000885 |
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crcambridgeupr:10.1017/jog.2021.88 2024-09-15T18:15:37+00:00 Inferred basal friction and mass flux affected by crystal-orientation fabrics Rathmann, Nicholas M. Lilien, David A. Villum Fonden Seventh Framework Programme 2021 http://dx.doi.org/10.1017/jog.2021.88 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143021000885 en eng Cambridge University Press (CUP) http://creativecommons.org/licenses/by/4.0/ Journal of Glaciology volume 68, issue 268, page 236-252 ISSN 0022-1430 1727-5652 journal-article 2021 crcambridgeupr https://doi.org/10.1017/jog.2021.88 2024-08-07T04:04:46Z We investigate the errors caused by neglecting the crystal-orientation fabric when inferring the basal friction coefficient field, and whether such errors can be alleviated by inferring an isotropic enhancement factor field to compensate for missing fabric information. We calculate the steady states that arise from ice flowing over a sticky spot and a bedrock bump using a vertical-slab numerical ice-flow model, consisting of a Weertman sliding law and the anisotropic Johnson flow law, coupled to a spectral fabric model of lattice rotation and dynamic recrystallisation. Given the steady or transient states as input for a canonical adjoint-based inversion, we find that Glen's isotropic flow law cannot necessarily be used to infer the true basal drag or friction coefficient field, which are obscured by the orientation fabric, thus potentially affecting vertically integrated mass fluxes. By inverting for an equivalent isotropic enhancement factor, a more accurate mass flux can be recovered, suggesting that joint inversions for basal friction and the isotropic flow-rate factor may be able to compensate for mechanical anisotropies caused by the fabric. Thus, in addition to other sources of rheological uncertainty, fabric might complicate attempts to relate subglacial conditions to basal properties inferred from an inversion relying on Glen's law. Article in Journal/Newspaper Journal of Glaciology Cambridge University Press Journal of Glaciology 1 17 |
institution |
Open Polar |
collection |
Cambridge University Press |
op_collection_id |
crcambridgeupr |
language |
English |
description |
We investigate the errors caused by neglecting the crystal-orientation fabric when inferring the basal friction coefficient field, and whether such errors can be alleviated by inferring an isotropic enhancement factor field to compensate for missing fabric information. We calculate the steady states that arise from ice flowing over a sticky spot and a bedrock bump using a vertical-slab numerical ice-flow model, consisting of a Weertman sliding law and the anisotropic Johnson flow law, coupled to a spectral fabric model of lattice rotation and dynamic recrystallisation. Given the steady or transient states as input for a canonical adjoint-based inversion, we find that Glen's isotropic flow law cannot necessarily be used to infer the true basal drag or friction coefficient field, which are obscured by the orientation fabric, thus potentially affecting vertically integrated mass fluxes. By inverting for an equivalent isotropic enhancement factor, a more accurate mass flux can be recovered, suggesting that joint inversions for basal friction and the isotropic flow-rate factor may be able to compensate for mechanical anisotropies caused by the fabric. Thus, in addition to other sources of rheological uncertainty, fabric might complicate attempts to relate subglacial conditions to basal properties inferred from an inversion relying on Glen's law. |
author2 |
Villum Fonden Seventh Framework Programme |
format |
Article in Journal/Newspaper |
author |
Rathmann, Nicholas M. Lilien, David A. |
spellingShingle |
Rathmann, Nicholas M. Lilien, David A. Inferred basal friction and mass flux affected by crystal-orientation fabrics |
author_facet |
Rathmann, Nicholas M. Lilien, David A. |
author_sort |
Rathmann, Nicholas M. |
title |
Inferred basal friction and mass flux affected by crystal-orientation fabrics |
title_short |
Inferred basal friction and mass flux affected by crystal-orientation fabrics |
title_full |
Inferred basal friction and mass flux affected by crystal-orientation fabrics |
title_fullStr |
Inferred basal friction and mass flux affected by crystal-orientation fabrics |
title_full_unstemmed |
Inferred basal friction and mass flux affected by crystal-orientation fabrics |
title_sort |
inferred basal friction and mass flux affected by crystal-orientation fabrics |
publisher |
Cambridge University Press (CUP) |
publishDate |
2021 |
url |
http://dx.doi.org/10.1017/jog.2021.88 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143021000885 |
genre |
Journal of Glaciology |
genre_facet |
Journal of Glaciology |
op_source |
Journal of Glaciology volume 68, issue 268, page 236-252 ISSN 0022-1430 1727-5652 |
op_rights |
http://creativecommons.org/licenses/by/4.0/ |
op_doi |
https://doi.org/10.1017/jog.2021.88 |
container_title |
Journal of Glaciology |
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1 |
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17 |
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1810453490661588992 |