Rheological Implications of the Internal Structure and Crystal Fabrics of the West Antarctic Ice Sheet as Revealed by Deep Core Drilling at Byrd Station
Crystalline textures and fabrics of ice cores from the 2164-m-thick ice sheet at Byrd Station, Antarctica, reveal the existence of an anisotropic ice sheet. A gradual but persistent increase in the c-axis preferred orientation of the ice crystals was observed between the surface and 1200m. This prog...
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ftdtic:ADA031745 2023-05-15T13:56:28+02:00 Rheological Implications of the Internal Structure and Crystal Fabrics of the West Antarctic Ice Sheet as Revealed by Deep Core Drilling at Byrd Station Gow,Anthony J Williamson,Terrence COLD REGIONS RESEARCH AND ENGINEERING LAB HANOVER N H 1976-09 text/html http://www.dtic.mil/docs/citations/ADA031745 http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA031745 en eng http://www.dtic.mil/docs/citations/ADA031745 APPROVED FOR PUBLIC RELEASE DTIC AND NTIS Snow Ice and Permafrost *SEA ICE *ANTARCTIC REGIONS *ICE CAPS THICKNESS RHEOLOGY TEXTURE CRYSTAL GROWTH DRILLING *Core drilling Ice cores Ice sheets Internal structure Ice fabrics Ice texture Coring Text 1976 ftdtic 2016-02-20T11:40:36Z Crystalline textures and fabrics of ice cores from the 2164-m-thick ice sheet at Byrd Station, Antarctica, reveal the existence of an anisotropic ice sheet. A gradual but persistent increase in the c-axis preferred orientation of the ice crystals was observed between the surface and 1200m. This progressive growth of an oriented crystal fabric is accompanied by a 20-fold increase in crystal sized between 56 and 600m, followed by virtually no change in crystal size between 6000 and 1200m. A broad vertical clustering of c-axes develops by 1200m. Between 1200 and 1300 m the structure transforms into a fine-grained mosaic of crystals with their basal glide planes now oriented substantially within the horizontal. This highly oriented fine-grained structure, which persists to 1800m, is compatible only with a strong horizontal shear deformation in this part of the ice sheet. Rapid transformation from single- to multiple-maximum fabrics occurs below 1800m. This transformation, accompanied by the growth of very large crystals, is attributed to the overriding effect of relatively high temperatures in the bottom layers of old ice at Byrd Station rather than to a significant decrease in stress. The zone of single-maximum fabrics between 1200 and 1800 m also contains numerous layers of volcanic dust. Fabrics of the very fine-grained ice associated with these dust bands indicate the bands are actively associated with shearing in the ice sheet. Some slipping of ice along the bedrock seems likely at Byrd Station, since the basal ice is at the pressure melting point and liquid water is known to exist at the ice/rock interface. Text Antarc* Antarctic Antarctica Ice Ice Sheet permafrost Sea ice Defense Technical Information Center: DTIC Technical Reports database Antarctic Byrd Byrd Station ENVELOPE(-119.533,-119.533,-80.017,-80.017) West Antarctic Ice Sheet |
institution |
Open Polar |
collection |
Defense Technical Information Center: DTIC Technical Reports database |
op_collection_id |
ftdtic |
language |
English |
topic |
Snow Ice and Permafrost *SEA ICE *ANTARCTIC REGIONS *ICE CAPS THICKNESS RHEOLOGY TEXTURE CRYSTAL GROWTH DRILLING *Core drilling Ice cores Ice sheets Internal structure Ice fabrics Ice texture Coring |
spellingShingle |
Snow Ice and Permafrost *SEA ICE *ANTARCTIC REGIONS *ICE CAPS THICKNESS RHEOLOGY TEXTURE CRYSTAL GROWTH DRILLING *Core drilling Ice cores Ice sheets Internal structure Ice fabrics Ice texture Coring Gow,Anthony J Williamson,Terrence Rheological Implications of the Internal Structure and Crystal Fabrics of the West Antarctic Ice Sheet as Revealed by Deep Core Drilling at Byrd Station |
topic_facet |
Snow Ice and Permafrost *SEA ICE *ANTARCTIC REGIONS *ICE CAPS THICKNESS RHEOLOGY TEXTURE CRYSTAL GROWTH DRILLING *Core drilling Ice cores Ice sheets Internal structure Ice fabrics Ice texture Coring |
description |
Crystalline textures and fabrics of ice cores from the 2164-m-thick ice sheet at Byrd Station, Antarctica, reveal the existence of an anisotropic ice sheet. A gradual but persistent increase in the c-axis preferred orientation of the ice crystals was observed between the surface and 1200m. This progressive growth of an oriented crystal fabric is accompanied by a 20-fold increase in crystal sized between 56 and 600m, followed by virtually no change in crystal size between 6000 and 1200m. A broad vertical clustering of c-axes develops by 1200m. Between 1200 and 1300 m the structure transforms into a fine-grained mosaic of crystals with their basal glide planes now oriented substantially within the horizontal. This highly oriented fine-grained structure, which persists to 1800m, is compatible only with a strong horizontal shear deformation in this part of the ice sheet. Rapid transformation from single- to multiple-maximum fabrics occurs below 1800m. This transformation, accompanied by the growth of very large crystals, is attributed to the overriding effect of relatively high temperatures in the bottom layers of old ice at Byrd Station rather than to a significant decrease in stress. The zone of single-maximum fabrics between 1200 and 1800 m also contains numerous layers of volcanic dust. Fabrics of the very fine-grained ice associated with these dust bands indicate the bands are actively associated with shearing in the ice sheet. Some slipping of ice along the bedrock seems likely at Byrd Station, since the basal ice is at the pressure melting point and liquid water is known to exist at the ice/rock interface. |
author2 |
COLD REGIONS RESEARCH AND ENGINEERING LAB HANOVER N H |
format |
Text |
author |
Gow,Anthony J Williamson,Terrence |
author_facet |
Gow,Anthony J Williamson,Terrence |
author_sort |
Gow,Anthony J |
title |
Rheological Implications of the Internal Structure and Crystal Fabrics of the West Antarctic Ice Sheet as Revealed by Deep Core Drilling at Byrd Station |
title_short |
Rheological Implications of the Internal Structure and Crystal Fabrics of the West Antarctic Ice Sheet as Revealed by Deep Core Drilling at Byrd Station |
title_full |
Rheological Implications of the Internal Structure and Crystal Fabrics of the West Antarctic Ice Sheet as Revealed by Deep Core Drilling at Byrd Station |
title_fullStr |
Rheological Implications of the Internal Structure and Crystal Fabrics of the West Antarctic Ice Sheet as Revealed by Deep Core Drilling at Byrd Station |
title_full_unstemmed |
Rheological Implications of the Internal Structure and Crystal Fabrics of the West Antarctic Ice Sheet as Revealed by Deep Core Drilling at Byrd Station |
title_sort |
rheological implications of the internal structure and crystal fabrics of the west antarctic ice sheet as revealed by deep core drilling at byrd station |
publishDate |
1976 |
url |
http://www.dtic.mil/docs/citations/ADA031745 http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA031745 |
long_lat |
ENVELOPE(-119.533,-119.533,-80.017,-80.017) |
geographic |
Antarctic Byrd Byrd Station West Antarctic Ice Sheet |
geographic_facet |
Antarctic Byrd Byrd Station West Antarctic Ice Sheet |
genre |
Antarc* Antarctic Antarctica Ice Ice Sheet permafrost Sea ice |
genre_facet |
Antarc* Antarctic Antarctica Ice Ice Sheet permafrost Sea ice |
op_source |
DTIC AND NTIS |
op_relation |
http://www.dtic.mil/docs/citations/ADA031745 |
op_rights |
APPROVED FOR PUBLIC RELEASE |
_version_ |
1766263978103668736 |