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| Titel |
Comparisons of Fabric Strength and Development in Polycrystalline Ice at Atmospheric and Basal Hydrostatic Pressures |
| VerfasserIn |
Daniel Breton, Ian Baker, David Cole |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250074829
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| Zusammenfassung |
| Understanding and predicting the flow of polycrystalline ice is crucial to ice sheet modeling
and paleoclimate reconstruction from ice cores. Ice flow rates depend strongly on the fabric
(i.e. the distribution of grain sizes and crystallographic orientations) which evolves over time
and enhances the flow rate in the direction of applied stress. The mechanisms for fabric
evolution in ice have been extensively studied at atmospheric pressures, but little work
has been done to observe these processes at the high pressures experienced deep
within ice sheets where long-term changes in ice rheology are expected to have
significance.
We conducted compressive creep tests to ~10% strain on 917 kg m-3, initially
randomly-oriented polycrystalline ice specimens at 0.1 (atmospheric) and 20 MPa
(simulating ~2,000 m depth) hydrostatic pressures, performing microstructural analyses on
the resulting deformed specimens to characterize the evolution and strength of crystal
fabric. Our microstructural analysis technique simultaneously collects grain shape
and size data from Scanning Electron Microscope (SEM) micrographs and obtains
crystallographic orientation data via Electron BackScatter Diffraction (EBSD).
Combining these measurements allows rapid analysis of the ice fabric over large
numbers of grains, yielding statistically useful numbers of grain size and orientation
data.
We present creep and microstructural data to demonstrate pressure-dependent effects on
the mechanical and microstructural evolution of polycrystalline ice and discuss possible
mechanisms for the observed differences. |
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