Mechanics and dynamics of pinning points on the Shirase Coast, West Antarctica
Ice rises and rumples, sites of localised ice-shelf grounding, modify ice-shelf flow by generating lateral and basal shear stresses, upstream compression, and downstream tension. Studies of pinning points typically quantify this role indirectly, through related metrics such as a buttressing number....
Published in: | The Cryosphere |
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Main Authors: | , |
Format: | Article in Journal/Newspaper |
Language: | English |
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Copernicus Publications
2021
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ftnonlinearchiv:oai:noa.gwlb.de:cop_mods_00056954 2023-05-15T13:37:33+02:00 Mechanics and dynamics of pinning points on the Shirase Coast, West Antarctica Still, Holly Hulbe, Christina 2021-06 electronic https://doi.org/10.5194/tc-15-2647-2021 https://noa.gwlb.de/receive/cop_mods_00056954 https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00056604/tc-15-2647-2021.pdf https://tc.copernicus.org/articles/15/2647/2021/tc-15-2647-2021.pdf eng eng Copernicus Publications The Cryosphere -- ˜Theœ Cryosphere -- http://www.bibliothek.uni-regensburg.de/ezeit/?2393169 -- http://www.the-cryosphere.net/ -- 1994-0424 https://doi.org/10.5194/tc-15-2647-2021 https://noa.gwlb.de/receive/cop_mods_00056954 https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00056604/tc-15-2647-2021.pdf https://tc.copernicus.org/articles/15/2647/2021/tc-15-2647-2021.pdf https://creativecommons.org/licenses/by/4.0/ uneingeschränkt info:eu-repo/semantics/openAccess CC-BY article Verlagsveröffentlichung article Text doc-type:article 2021 ftnonlinearchiv https://doi.org/10.5194/tc-15-2647-2021 2022-02-08T22:33:49Z Ice rises and rumples, sites of localised ice-shelf grounding, modify ice-shelf flow by generating lateral and basal shear stresses, upstream compression, and downstream tension. Studies of pinning points typically quantify this role indirectly, through related metrics such as a buttressing number. Here, we quantify the dynamic effects of pinning points directly, by comparing model-simulated stress states in the Ross Ice Shelf (RIS) with and without a specific set of pinning points located downstream of the MacAyeal and Bindschadler ice streams (MacIS and BIS, respectively). Because ice properties are only known indirectly, the experiment is repeated with different realisations of the ice softness. While longitudinal stretching, and thus ice velocity, is smaller with the pinning points, flow resistance generated by other grounded features is also smaller. Conversely, flow resistance generated by other grounded features increases when the pinning points are absent, providing a non-local control on the net effect of the pinning points on ice-shelf flow. We find that an ice stream located directly upstream of the pinning points, MacIS, is less responsive to their removal than the obliquely oriented BIS. This response is due to zones of locally higher basal drag acting on MacIS, which may itself be a consequence of the coupled ice-shelf and ice-stream response to the pinning points. We also find that inversion of present-day flow and thickness for basal friction and ice softness, without feature-specific, a posteriori adjustment, leads to the incorrect representation of ice rumple morphology and an incorrect boundary condition at the ice base. Viewed from the perspective of change detection, we find that, following pinning point removal, the ice shelf undergoes an adjustment to a new steady state that involves an initial increase in ice speeds across the eastern ice shelf, followed by decaying flow speeds, as mass flux reduces thickness gradients in some areas and increases thickness gradients in others. Increases in ice-stream flow speeds persist with no further adjustment, even without sustained grounding-line retreat. Where pinning point effects are important, model tuning that respects their morphology is necessary to represent the system as a whole and inform interpretations of observed change. Article in Journal/Newspaper Antarc* Antarctica Ice Shelf Ross Ice Shelf The Cryosphere West Antarctica Niedersächsisches Online-Archiv NOA Ross Ice Shelf Shirase Coast ENVELOPE(-158.000,-158.000,-78.500,-78.500) West Antarctica The Cryosphere 15 6 2647 2665 |
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Open Polar |
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Niedersächsisches Online-Archiv NOA |
op_collection_id |
ftnonlinearchiv |
language |
English |
topic |
article Verlagsveröffentlichung |
spellingShingle |
article Verlagsveröffentlichung Still, Holly Hulbe, Christina Mechanics and dynamics of pinning points on the Shirase Coast, West Antarctica |
topic_facet |
article Verlagsveröffentlichung |
description |
Ice rises and rumples, sites of localised ice-shelf grounding, modify ice-shelf flow by generating lateral and basal shear stresses, upstream compression, and downstream tension. Studies of pinning points typically quantify this role indirectly, through related metrics such as a buttressing number. Here, we quantify the dynamic effects of pinning points directly, by comparing model-simulated stress states in the Ross Ice Shelf (RIS) with and without a specific set of pinning points located downstream of the MacAyeal and Bindschadler ice streams (MacIS and BIS, respectively). Because ice properties are only known indirectly, the experiment is repeated with different realisations of the ice softness. While longitudinal stretching, and thus ice velocity, is smaller with the pinning points, flow resistance generated by other grounded features is also smaller. Conversely, flow resistance generated by other grounded features increases when the pinning points are absent, providing a non-local control on the net effect of the pinning points on ice-shelf flow. We find that an ice stream located directly upstream of the pinning points, MacIS, is less responsive to their removal than the obliquely oriented BIS. This response is due to zones of locally higher basal drag acting on MacIS, which may itself be a consequence of the coupled ice-shelf and ice-stream response to the pinning points. We also find that inversion of present-day flow and thickness for basal friction and ice softness, without feature-specific, a posteriori adjustment, leads to the incorrect representation of ice rumple morphology and an incorrect boundary condition at the ice base. Viewed from the perspective of change detection, we find that, following pinning point removal, the ice shelf undergoes an adjustment to a new steady state that involves an initial increase in ice speeds across the eastern ice shelf, followed by decaying flow speeds, as mass flux reduces thickness gradients in some areas and increases thickness gradients in others. Increases in ice-stream flow speeds persist with no further adjustment, even without sustained grounding-line retreat. Where pinning point effects are important, model tuning that respects their morphology is necessary to represent the system as a whole and inform interpretations of observed change. |
format |
Article in Journal/Newspaper |
author |
Still, Holly Hulbe, Christina |
author_facet |
Still, Holly Hulbe, Christina |
author_sort |
Still, Holly |
title |
Mechanics and dynamics of pinning points on the Shirase Coast, West Antarctica |
title_short |
Mechanics and dynamics of pinning points on the Shirase Coast, West Antarctica |
title_full |
Mechanics and dynamics of pinning points on the Shirase Coast, West Antarctica |
title_fullStr |
Mechanics and dynamics of pinning points on the Shirase Coast, West Antarctica |
title_full_unstemmed |
Mechanics and dynamics of pinning points on the Shirase Coast, West Antarctica |
title_sort |
mechanics and dynamics of pinning points on the shirase coast, west antarctica |
publisher |
Copernicus Publications |
publishDate |
2021 |
url |
https://doi.org/10.5194/tc-15-2647-2021 https://noa.gwlb.de/receive/cop_mods_00056954 https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00056604/tc-15-2647-2021.pdf https://tc.copernicus.org/articles/15/2647/2021/tc-15-2647-2021.pdf |
long_lat |
ENVELOPE(-158.000,-158.000,-78.500,-78.500) |
geographic |
Ross Ice Shelf Shirase Coast West Antarctica |
geographic_facet |
Ross Ice Shelf Shirase Coast West Antarctica |
genre |
Antarc* Antarctica Ice Shelf Ross Ice Shelf The Cryosphere West Antarctica |
genre_facet |
Antarc* Antarctica Ice Shelf Ross Ice Shelf The Cryosphere West Antarctica |
op_relation |
The Cryosphere -- ˜Theœ Cryosphere -- http://www.bibliothek.uni-regensburg.de/ezeit/?2393169 -- http://www.the-cryosphere.net/ -- 1994-0424 https://doi.org/10.5194/tc-15-2647-2021 https://noa.gwlb.de/receive/cop_mods_00056954 https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00056604/tc-15-2647-2021.pdf https://tc.copernicus.org/articles/15/2647/2021/tc-15-2647-2021.pdf |
op_rights |
https://creativecommons.org/licenses/by/4.0/ uneingeschränkt info:eu-repo/semantics/openAccess |
op_rightsnorm |
CC-BY |
op_doi |
https://doi.org/10.5194/tc-15-2647-2021 |
container_title |
The Cryosphere |
container_volume |
15 |
container_issue |
6 |
container_start_page |
2647 |
op_container_end_page |
2665 |
_version_ |
1766094080915275776 |