DataSheet1_Softening of Temperate Ice by Interstitial Water.pdf
Ice at depth in ice-stream shear margins is thought to commonly be temperate, with interstitial meltwater that softens ice. Models that include this softening extrapolate results of a single experimental study in which ice effective viscosity decreased by a factor of ∼3 over water contents of ∼0.01–...
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ftfrontimediafig:oai:figshare.com:article/14985351 2023-05-15T13:40:12+02:00 DataSheet1_Softening of Temperate Ice by Interstitial Water.pdf Conner J. C. Adams Neal R. Iverson Christian Helanow Lucas K. Zoet Charlotte E. Bate 2021-07-15T04:26:45Z https://doi.org/10.3389/feart.2021.702761.s001 https://figshare.com/articles/dataset/DataSheet1_Softening_of_Temperate_Ice_by_Interstitial_Water_pdf/14985351 unknown doi:10.3389/feart.2021.702761.s001 https://figshare.com/articles/dataset/DataSheet1_Softening_of_Temperate_Ice_by_Interstitial_Water_pdf/14985351 CC BY 4.0 CC-BY Solid Earth Sciences Climate Science Atmospheric Sciences not elsewhere classified Exploration Geochemistry Inorganic Geochemistry Isotope Geochemistry Organic Geochemistry Geochemistry not elsewhere classified Igneous and Metamorphic Petrology Ore Deposit Petrology Palaeontology (incl. Palynology) Structural Geology Tectonics Volcanology Geology not elsewhere classified Seismology and Seismic Exploration Glaciology Hydrogeology Natural Hazards Quaternary Environments Earth Sciences not elsewhere classified Evolutionary Impacts of Climate Change ice stream shear margin experiments water content ice creep viscosity Dataset 2021 ftfrontimediafig https://doi.org/10.3389/feart.2021.702761.s001 2021-07-21T23:02:16Z Ice at depth in ice-stream shear margins is thought to commonly be temperate, with interstitial meltwater that softens ice. Models that include this softening extrapolate results of a single experimental study in which ice effective viscosity decreased by a factor of ∼3 over water contents of ∼0.01–0.8%. Modeling indicates this softening by water localizes strain in shear margins and through shear heating increases meltwater at the bed, enhancing basal slip. To extend data to higher water contents, we shear lab-made ice in confined compression with a large ring-shear device. Ice rings with initial mean grain sizes of 2–4 mm are kept at the pressure-melting temperature and sheared at controlled rates with peak stresses of ∼0.06–0.20 MPa, spanning most of the estimated shear-stress range in West Antarctic shear margins. Final mean grain sizes are 8–13 mm. Water content is measured by inducing a freezing front at the ice-ring edges, tracking its movement inward with thermistors, and fitting the data with solutions of the relevant Stefan problem. Results indicate two creep regimes, below and above a water content of ∼0.6%. Comparison of effective viscosity values in secondary creep with those of tertiary creep from the earlier experimental study indicate that for water contents of 0.2–0.6%, viscosity in secondary creep is about twice as sensitive to water content than for ice sheared to tertiary creep. Above water contents of 0.6%, viscosity values in secondary creep are within 25% of those of tertiary creep, suggesting a stress-limiting mechanism at water contents greater than 0.6% that is insensitive to ice fabric development in tertiary creep. At water contents of ∼0.6–1.7%, effective viscosity is independent of water content, and ice is nearly linear-viscous. Minimization of intercrystalline stress heterogeneity by grain-scale melting and refreezing at rates that approach an upper bound as grain-boundary water films thicken might account for the two regimes. Dataset Antarc* Antarctic Frontiers: Figshare Antarctic |
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Open Polar |
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Frontiers: Figshare |
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ftfrontimediafig |
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unknown |
topic |
Solid Earth Sciences Climate Science Atmospheric Sciences not elsewhere classified Exploration Geochemistry Inorganic Geochemistry Isotope Geochemistry Organic Geochemistry Geochemistry not elsewhere classified Igneous and Metamorphic Petrology Ore Deposit Petrology Palaeontology (incl. Palynology) Structural Geology Tectonics Volcanology Geology not elsewhere classified Seismology and Seismic Exploration Glaciology Hydrogeology Natural Hazards Quaternary Environments Earth Sciences not elsewhere classified Evolutionary Impacts of Climate Change ice stream shear margin experiments water content ice creep viscosity |
spellingShingle |
Solid Earth Sciences Climate Science Atmospheric Sciences not elsewhere classified Exploration Geochemistry Inorganic Geochemistry Isotope Geochemistry Organic Geochemistry Geochemistry not elsewhere classified Igneous and Metamorphic Petrology Ore Deposit Petrology Palaeontology (incl. Palynology) Structural Geology Tectonics Volcanology Geology not elsewhere classified Seismology and Seismic Exploration Glaciology Hydrogeology Natural Hazards Quaternary Environments Earth Sciences not elsewhere classified Evolutionary Impacts of Climate Change ice stream shear margin experiments water content ice creep viscosity Conner J. C. Adams Neal R. Iverson Christian Helanow Lucas K. Zoet Charlotte E. Bate DataSheet1_Softening of Temperate Ice by Interstitial Water.pdf |
topic_facet |
Solid Earth Sciences Climate Science Atmospheric Sciences not elsewhere classified Exploration Geochemistry Inorganic Geochemistry Isotope Geochemistry Organic Geochemistry Geochemistry not elsewhere classified Igneous and Metamorphic Petrology Ore Deposit Petrology Palaeontology (incl. Palynology) Structural Geology Tectonics Volcanology Geology not elsewhere classified Seismology and Seismic Exploration Glaciology Hydrogeology Natural Hazards Quaternary Environments Earth Sciences not elsewhere classified Evolutionary Impacts of Climate Change ice stream shear margin experiments water content ice creep viscosity |
description |
Ice at depth in ice-stream shear margins is thought to commonly be temperate, with interstitial meltwater that softens ice. Models that include this softening extrapolate results of a single experimental study in which ice effective viscosity decreased by a factor of ∼3 over water contents of ∼0.01–0.8%. Modeling indicates this softening by water localizes strain in shear margins and through shear heating increases meltwater at the bed, enhancing basal slip. To extend data to higher water contents, we shear lab-made ice in confined compression with a large ring-shear device. Ice rings with initial mean grain sizes of 2–4 mm are kept at the pressure-melting temperature and sheared at controlled rates with peak stresses of ∼0.06–0.20 MPa, spanning most of the estimated shear-stress range in West Antarctic shear margins. Final mean grain sizes are 8–13 mm. Water content is measured by inducing a freezing front at the ice-ring edges, tracking its movement inward with thermistors, and fitting the data with solutions of the relevant Stefan problem. Results indicate two creep regimes, below and above a water content of ∼0.6%. Comparison of effective viscosity values in secondary creep with those of tertiary creep from the earlier experimental study indicate that for water contents of 0.2–0.6%, viscosity in secondary creep is about twice as sensitive to water content than for ice sheared to tertiary creep. Above water contents of 0.6%, viscosity values in secondary creep are within 25% of those of tertiary creep, suggesting a stress-limiting mechanism at water contents greater than 0.6% that is insensitive to ice fabric development in tertiary creep. At water contents of ∼0.6–1.7%, effective viscosity is independent of water content, and ice is nearly linear-viscous. Minimization of intercrystalline stress heterogeneity by grain-scale melting and refreezing at rates that approach an upper bound as grain-boundary water films thicken might account for the two regimes. |
format |
Dataset |
author |
Conner J. C. Adams Neal R. Iverson Christian Helanow Lucas K. Zoet Charlotte E. Bate |
author_facet |
Conner J. C. Adams Neal R. Iverson Christian Helanow Lucas K. Zoet Charlotte E. Bate |
author_sort |
Conner J. C. Adams |
title |
DataSheet1_Softening of Temperate Ice by Interstitial Water.pdf |
title_short |
DataSheet1_Softening of Temperate Ice by Interstitial Water.pdf |
title_full |
DataSheet1_Softening of Temperate Ice by Interstitial Water.pdf |
title_fullStr |
DataSheet1_Softening of Temperate Ice by Interstitial Water.pdf |
title_full_unstemmed |
DataSheet1_Softening of Temperate Ice by Interstitial Water.pdf |
title_sort |
datasheet1_softening of temperate ice by interstitial water.pdf |
publishDate |
2021 |
url |
https://doi.org/10.3389/feart.2021.702761.s001 https://figshare.com/articles/dataset/DataSheet1_Softening_of_Temperate_Ice_by_Interstitial_Water_pdf/14985351 |
geographic |
Antarctic |
geographic_facet |
Antarctic |
genre |
Antarc* Antarctic |
genre_facet |
Antarc* Antarctic |
op_relation |
doi:10.3389/feart.2021.702761.s001 https://figshare.com/articles/dataset/DataSheet1_Softening_of_Temperate_Ice_by_Interstitial_Water_pdf/14985351 |
op_rights |
CC BY 4.0 |
op_rightsnorm |
CC-BY |
op_doi |
https://doi.org/10.3389/feart.2021.702761.s001 |
_version_ |
1766130591941525504 |