A new approach to inferring basal drag and ice rheology in ice streams, with applications to West Antarctic Ice Streams
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 invers...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
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Cambridge University Press
2021-04-01
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| Series: | Journal of Glaciology |
| Subjects: | |
| Online Access: | https://www.cambridge.org/core/product/identifier/S0022143020000957/type/journal_article |
| _version_ | 1811155819231707136 |
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| author | Meghana Ranganathan Brent Minchew Colin R. Meyer G. Hilmar Gudmundsson |
| author_facet | Meghana Ranganathan Brent Minchew Colin R. Meyer G. Hilmar Gudmundsson |
| author_sort | Meghana Ranganathan |
| collection | DOAJ |
| description | 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. |
| first_indexed | 2024-04-10T04:39:58Z |
| format | Article |
| id | doaj.art-b90d9bd5927643a1b8ed194ca9239692 |
| institution | Directory Open Access Journal |
| issn | 0022-1430 1727-5652 |
| language | English |
| last_indexed | 2024-04-10T04:39:58Z |
| publishDate | 2021-04-01 |
| publisher | Cambridge University Press |
| record_format | Article |
| series | Journal of Glaciology |
| spelling | doaj.art-b90d9bd5927643a1b8ed194ca92396922023-03-09T12:41:03ZengCambridge University PressJournal of Glaciology0022-14301727-56522021-04-016722924210.1017/jog.2020.95A new approach to inferring basal drag and ice rheology in ice streams, with applications to West Antarctic Ice StreamsMeghana Ranganathan0https://orcid.org/0000-0002-8099-4775Brent Minchew1https://orcid.org/0000-0002-5991-3926Colin R. Meyer2https://orcid.org/0000-0002-1209-1881G. Hilmar Gudmundsson3https://orcid.org/0000-0003-4236-5369Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA, USADepartment of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA, USAThayer School of Engineering, Dartmouth College, Hanover, NH, USAGeography and Environmental Sciences, Northumbria University, Newcastle upon Tyne, UKDrag 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.https://www.cambridge.org/core/product/identifier/S0022143020000957/type/journal_articleAntarctic glaciologyglacier flowice dynamicsice rheologyice streams |
| spellingShingle | Meghana Ranganathan Brent Minchew Colin R. Meyer G. Hilmar Gudmundsson A new approach to inferring basal drag and ice rheology in ice streams, with applications to West Antarctic Ice Streams Journal of Glaciology Antarctic glaciology glacier flow ice dynamics ice rheology ice streams |
| title | 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_short | 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 |
| topic | Antarctic glaciology glacier flow ice dynamics ice rheology ice streams |
| url | https://www.cambridge.org/core/product/identifier/S0022143020000957/type/journal_article |
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