Ice microstructure (electron backscatter diffraction) from Jarvis Glacier, Alaska, 2017-2020
Ice sheets and alpine glaciers discharge primarily though streaming flow, so the dynamics of that flow is central to the overall mass balance of the cryosphere. In glaciers and ice streams, the resistance to flow at the bed is important, but equally important is the internal viscous strength of the...
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| Format: | Dataset |
| Language: | English |
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NSF Arctic Data Center
2020
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| Online Access: | https://dx.doi.org/10.18739/a2gb1xh9k https://arcticdata.io/catalog/view/doi:10.18739/A2GB1XH9K |
| Summary: | Ice sheets and alpine glaciers discharge primarily though streaming flow, so the dynamics of that flow is central to the overall mass balance of the cryosphere. In glaciers and ice streams, the resistance to flow at the bed is important, but equally important is the internal viscous strength of the ice near the margins. In many cases, the lateral margins support greater than 50% of the resisting stress. At present, there is moderate to high uncertainty of the factors controlling the viscous strength of streaming ice under natural conditions. Although experiments suggest that variations in the intensity and orientation of the crystallographic fabric can result in up to a ten-fold difference in flow strength, in-situ observational studies of the microstructural architecture of streaming ice number in the low single digits. Most microstructural and in-situ rheological studies come from ice divides, near sites of paleoclimate coring. To complement that work and provide insight into the dynamic influence of streaming ice margins, our study documented both temperature and microstructure across a strain gradient at the lateral margin of Jarvis (Creek) Glacier and related those observations to modeled and observed 3D velocity structure. The dataset included here is one component of the larger project described above: electron backscatter diffraction raw and processed data from two ice cores collected in spring 2017. Holes were drilled along a transect from less to more sheared ice, with the goal being to reach bed in at least two locations within the time constraints of the drilling season. We attempted six holes. The first (JA; 63.4750˚N, 145.6753˚W, 1621 m elevation), and fifth (JE; 63.4743˚N, 145.6766˚W, 1625 m elevation) appear to have reached bed, and those are the ones represented in this dataset. Other cores were limited by debris. All data were collected at 60 degree tilt using an EDAX-TSL electron backscatter diffraction (EBSD) system on a Tescan Vega II electron microscope. Raw data files (in text format, with .ang extension) are not tilt-corrected. In addition to the raw data, we include products derived from the EBSD data: one-point-per-grain orientation lists, and orientation tensors for each sample. For background, we also include a location map and core log. |
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