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...
| Main Authors: | , |
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| Format: | Article |
| Language: | English |
| Published: |
Cambridge University Press
2022-04-01
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| Series: | Journal of Glaciology |
| Subjects: | |
| Online Access: | https://www.cambridge.org/core/product/identifier/S0022143021000885/type/journal_article |
| _version_ | 1811155750687342592 |
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| author | Nicholas M. Rathmann David A. Lilien |
| author_facet | Nicholas M. Rathmann David A. Lilien |
| author_sort | Nicholas M. Rathmann |
| collection | DOAJ |
| 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. |
| first_indexed | 2024-04-10T04:39:48Z |
| format | Article |
| id | doaj.art-9cc26a5085d142e29434bbc4b84fe851 |
| institution | Directory Open Access Journal |
| issn | 0022-1430 1727-5652 |
| language | English |
| last_indexed | 2024-04-10T04:39:48Z |
| publishDate | 2022-04-01 |
| publisher | Cambridge University Press |
| record_format | Article |
| series | Journal of Glaciology |
| spelling | doaj.art-9cc26a5085d142e29434bbc4b84fe8512023-03-09T12:41:13ZengCambridge University PressJournal of Glaciology0022-14301727-56522022-04-016823625210.1017/jog.2021.88Inferred basal friction and mass flux affected by crystal-orientation fabricsNicholas M. Rathmann0https://orcid.org/0000-0001-7140-0931David A. Lilien1https://orcid.org/0000-0001-8667-8020Niels Bohr Institute, University of Copenhagen, Copenhagen, DenmarkNiels Bohr Institute, University of Copenhagen, Copenhagen, DenmarkWe 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.https://www.cambridge.org/core/product/identifier/S0022143021000885/type/journal_articleAnisotropic ice flowice rheologysubglacial processesrecrystallisation |
| spellingShingle | Nicholas M. Rathmann David A. Lilien Inferred basal friction and mass flux affected by crystal-orientation fabrics Journal of Glaciology Anisotropic ice flow ice rheology subglacial processes recrystallisation |
| title | 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_short | Inferred basal friction and mass flux affected by crystal-orientation fabrics |
| title_sort | inferred basal friction and mass flux affected by crystal orientation fabrics |
| topic | Anisotropic ice flow ice rheology subglacial processes recrystallisation |
| url | https://www.cambridge.org/core/product/identifier/S0022143021000885/type/journal_article |
| work_keys_str_mv | AT nicholasmrathmann inferredbasalfrictionandmassfluxaffectedbycrystalorientationfabrics AT davidalilien inferredbasalfrictionandmassfluxaffectedbycrystalorientationfabrics |