Radar characterization of ice crystal orientation fabric and anisotropic rheology within Rutford Ice Stream, 2017-2019
We use polarimetric radar sounding to investigate variation in ice crystal orientation fabric within the near-surface (top 40-300 m) of Rutford Ice Stream, West Antarctica. To assess the influence of the fabric on ice flow, we use an analytical model to derive anisotropic enhancements of the flow law from the fabric measurements. In the shallowest ice (40-100 m) the azimuthal fabric orientation is consistent with flow-induced development and correlates with the surface strain field. Notably, toward the ice-stream margins, both the horizontal compression angle and fabric orientation tend toward 45 degrees relative to ice flow. This result is consistent with theoretical predictions of flow-induced fabric under simple shear, but to our knowledge has never been observed. The fabric orientation in deeper ice (100-300 m) is significantly misaligned with shallower ice in some locations, and therefore inconsistent with the local surface strain field. This result represents a new challenge for ice flow models which typically infer basal properties from the surface conditions assuming simplified vertical variation of ice flow. Our technique retrieves azimuthal variations in fabric but is insensitive to vertical variation, and we therefore constrain the fabric and rheology within two end-members: a vertical girdle or a horizontal pole. Our hypotheses are that fabric near the center of the ice-stream tends to a vertical girdle that enhances horizontal compression, and near the ice-stream margins tends to a horizontal pole that enhances lateral shear.
ApRES radar data were collected as part of the BEAMISH Project (NERC AFI award numbers NE/G014159/1 and NE/G013187/1). Tom Jordan would like to acknowledge support from EU Horizon 2020 grant 747336-BRISRES-H2020-MSCA-IF-2016.
Simple
- Alternate title
- Polar Data Centre (PDC) record GB/NERC/BAS/PDC/01428
- Date (Publication)
- 2020-11-04
- Identifier
- http://www.antarctica.ac.uk/dms/metadata.php?id= / GB/NERC/BAS/PDC/01428
- Maintenance and update frequency
- unknown Unknown
- Keywords
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- NDGO0001
- NERC OAI Harvesting
-
- NERC_DDC
- GCMD Parameter Valids
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- EARTH SCIENCE > Cryosphere > Glaciers/Ice Sheets
- EARTH SCIENCE > Cryosphere > Glaciers/Ice Sheets > Glacier Motion/Ice Sheet Motion
- EARTH SCIENCE > Spectral/Engineering > Radar
- BAS Free-text keywords
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- anisotropy
- fabric
- ice flow
- polarimetry
- radar
- rheology
- Use limitation
- This data is supplied under Open Government Licence v3.0 http://www.nationalarchives.gov.uk/doc/open-government-licence/version/3/.
- Access constraints
- otherRestrictions Other restrictions
- Other constraints
- This data is supplied under Open Government Licence v3.0 http://www.nationalarchives.gov.uk/doc/open-government-licence/version/3/.
- Metadata language
- EnglishEnglish
- Topic category
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- Environment
- Geoscientific information
- Begin date
- 2019-12-05
- End date
- 2019-12-05
- Reference system identifier
- OGP / urn:ogc:def:crs:EPSG::4326
- Distribution format
-
- OnLine resource
- https://doi.org/10.1029/2018JF004776
- Hierarchy level
- dataset Dataset
Domain consistency
- Measure identification
- INSPIRE / Conformity_001
Conformance result
- Date
- Explanation
- See the referenced specification
- Pass
- No
- Statement
- Polarimetric data quality is established from the coherence magnitude, which provides a metric for sections of the ice column where fabric can be reliably estimated. Fabric estimates could be made in the top 100-200 m of the ice column at 18 of the 20 measurement sites (maximum depth ~ 100 m near the shear-margin, and ~200 m in the ice-stream centre).
- File identifier
- GB_NERC_BAS_PDC_01428 XML
- Metadata language
- EnglishEnglish
- Hierarchy level
- dataset Dataset
- Date stamp
- 2020-11-04
- Metadata standard name
- NERC profile of ISO19115:2003
- Metadata standard version
- 1.0