Calculating Basal Thermal Zones Beneath the Antarctic Ice Sheet
A procedure is presented for using a simple flowline model to calculate the fraction of the bed that is thawed beneath present-day ice sheets, and therefore for mapping thawed, frozen, melting and freezing basal thermal zones. The procedure is based on the proposition, easily demonstrated, that vari...
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2000
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ftmaineuniv:oai:digitalcommons.library.umaine.edu:ers_facpub-1018 2024-09-15T17:39:11+00:00 Calculating Basal Thermal Zones Beneath the Antarctic Ice Sheet Wilch, Ellen Huges, Terence J. 2000-01-01T08:00:00Z application/pdf https://digitalcommons.library.umaine.edu/ers_facpub/19 https://doi.org/10.3189/172756500781832927 https://digitalcommons.library.umaine.edu/context/ers_facpub/article/1018/viewcontent/hughes_46.153.297.pdf unknown DigitalCommons@UMaine https://digitalcommons.library.umaine.edu/ers_facpub/19 doi:10.3189/172756500781832927 https://digitalcommons.library.umaine.edu/context/ers_facpub/article/1018/viewcontent/hughes_46.153.297.pdf This Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. In addition, no permission is required from the rights-holder(s) for educational uses. For other uses, you need to obtain permission from the rights-holder(s). Earth Science Faculty Scholarship Earth Sciences text 2000 ftmaineuniv https://doi.org/10.3189/172756500781832927 2024-07-24T05:38:40Z A procedure is presented for using a simple flowline model to calculate the fraction of the bed that is thawed beneath present-day ice sheets, and therefore for mapping thawed, frozen, melting and freezing basal thermal zones. The procedure is based on the proposition, easily demonstrated, that variations in surface slope along ice flowlines are due primarily to variations in bed topography and ice-bed coupling, where ice-bed coupling for sheet flow is represented by the basal thawed fraction. This procedure is then applied to the central flowlines of flow bands on the Antarctic ice sheet where accumulation rates, surface elevations and bed topography are mapped with sufficient accuracy, and where sheet flow rather than stream flow prevails. In East Antarctica, the usual condition is a low thawed fraction in subglacial highlands, but a high thawed fraction in subglacial basins and where ice converges on ice streams. This is consistent with a greater depression of the basal melting temperature and a slower rate of conducting basal heat to the surface where ice is thick, and greater basal frictional heat production where ice flow is fast, as expected for steady-state flow. This correlation is reduced or even reversed where steady-state flow has been disrupted recently, notably where ice-stream surges produced the Dibble and Dalton Iceberg Tongues, both of which are now stagnating. In West Antarctica, for ice draining into the Pine Island Bay polynya of the Amundsen Sea, the basal thawed fraction is consistent with a prolonged and ongoing surge of Pine Island Glacier and with a recently initiated surge of Thwaites Glacier. For ice draining into the Ross Ice Shelf, long ice streams extend nearly to the West Antarctic ice divide. Over the rugged bed topography near the ice divide, no correlation consistent with steady-state sheet flow exists between ice thickness and the basal thawed fraction. The bed is wholly thawed beneath ice streams, even where stream flow is slow. This is consistent with ongoing gravitational ... Text Amundsen Sea Antarc* Antarctic Antarctica East Antarctica Ice Sheet Ice Shelf Iceberg* Pine Island Pine Island Bay Pine Island Glacier Ross Ice Shelf Thwaites Glacier West Antarctica The University of Maine: DigitalCommons@UMaine Journal of Glaciology 46 153 297 310 |
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Open Polar |
collection |
The University of Maine: DigitalCommons@UMaine |
op_collection_id |
ftmaineuniv |
language |
unknown |
topic |
Earth Sciences |
spellingShingle |
Earth Sciences Wilch, Ellen Huges, Terence J. Calculating Basal Thermal Zones Beneath the Antarctic Ice Sheet |
topic_facet |
Earth Sciences |
description |
A procedure is presented for using a simple flowline model to calculate the fraction of the bed that is thawed beneath present-day ice sheets, and therefore for mapping thawed, frozen, melting and freezing basal thermal zones. The procedure is based on the proposition, easily demonstrated, that variations in surface slope along ice flowlines are due primarily to variations in bed topography and ice-bed coupling, where ice-bed coupling for sheet flow is represented by the basal thawed fraction. This procedure is then applied to the central flowlines of flow bands on the Antarctic ice sheet where accumulation rates, surface elevations and bed topography are mapped with sufficient accuracy, and where sheet flow rather than stream flow prevails. In East Antarctica, the usual condition is a low thawed fraction in subglacial highlands, but a high thawed fraction in subglacial basins and where ice converges on ice streams. This is consistent with a greater depression of the basal melting temperature and a slower rate of conducting basal heat to the surface where ice is thick, and greater basal frictional heat production where ice flow is fast, as expected for steady-state flow. This correlation is reduced or even reversed where steady-state flow has been disrupted recently, notably where ice-stream surges produced the Dibble and Dalton Iceberg Tongues, both of which are now stagnating. In West Antarctica, for ice draining into the Pine Island Bay polynya of the Amundsen Sea, the basal thawed fraction is consistent with a prolonged and ongoing surge of Pine Island Glacier and with a recently initiated surge of Thwaites Glacier. For ice draining into the Ross Ice Shelf, long ice streams extend nearly to the West Antarctic ice divide. Over the rugged bed topography near the ice divide, no correlation consistent with steady-state sheet flow exists between ice thickness and the basal thawed fraction. The bed is wholly thawed beneath ice streams, even where stream flow is slow. This is consistent with ongoing gravitational ... |
format |
Text |
author |
Wilch, Ellen Huges, Terence J. |
author_facet |
Wilch, Ellen Huges, Terence J. |
author_sort |
Wilch, Ellen |
title |
Calculating Basal Thermal Zones Beneath the Antarctic Ice Sheet |
title_short |
Calculating Basal Thermal Zones Beneath the Antarctic Ice Sheet |
title_full |
Calculating Basal Thermal Zones Beneath the Antarctic Ice Sheet |
title_fullStr |
Calculating Basal Thermal Zones Beneath the Antarctic Ice Sheet |
title_full_unstemmed |
Calculating Basal Thermal Zones Beneath the Antarctic Ice Sheet |
title_sort |
calculating basal thermal zones beneath the antarctic ice sheet |
publisher |
DigitalCommons@UMaine |
publishDate |
2000 |
url |
https://digitalcommons.library.umaine.edu/ers_facpub/19 https://doi.org/10.3189/172756500781832927 https://digitalcommons.library.umaine.edu/context/ers_facpub/article/1018/viewcontent/hughes_46.153.297.pdf |
genre |
Amundsen Sea Antarc* Antarctic Antarctica East Antarctica Ice Sheet Ice Shelf Iceberg* Pine Island Pine Island Bay Pine Island Glacier Ross Ice Shelf Thwaites Glacier West Antarctica |
genre_facet |
Amundsen Sea Antarc* Antarctic Antarctica East Antarctica Ice Sheet Ice Shelf Iceberg* Pine Island Pine Island Bay Pine Island Glacier Ross Ice Shelf Thwaites Glacier West Antarctica |
op_source |
Earth Science Faculty Scholarship |
op_relation |
https://digitalcommons.library.umaine.edu/ers_facpub/19 doi:10.3189/172756500781832927 https://digitalcommons.library.umaine.edu/context/ers_facpub/article/1018/viewcontent/hughes_46.153.297.pdf |
op_rights |
This Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. In addition, no permission is required from the rights-holder(s) for educational uses. For other uses, you need to obtain permission from the rights-holder(s). |
op_doi |
https://doi.org/10.3189/172756500781832927 |
container_title |
Journal of Glaciology |
container_volume |
46 |
container_issue |
153 |
container_start_page |
297 |
op_container_end_page |
310 |
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1810478053126569984 |