This data set contains subglacial water flow paths beneath Thwaites Glacier, West Antarctica, interpreted from ice thickness and bed elevation measurements collected between 7 December 2004 and 31 January 2005 by the Airborne Geophysical Survey of the Amundsen Embayment (AGASEA) expedition.
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Subglacial water flow paths under Thwaites Glacier, West Antarctica, Version 1
Geographic Coverage
Spatial Coverage: |
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Spatial Resolution: | Not Specified |
Temporal Coverage: |
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Temporal Resolution: | Not specified |
Parameter(s): |
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Platform(s) | AIRCRAFT |
Sensor(s): | RADAR |
Data Format(s): |
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Version: | V1 |
Data Contributor(s): | Sasha Carter, Duncan Young, Donald Blankenship |
Metadata XML: | View Metadata Record |
Data Citation
As a condition of using these data, you must cite the use of this data set using the following citation. For more information, see our Use and Copyright Web page.
Carter, S. P., D. A. Young, and D. D. Blankenship 2012. Subglacial water flow paths under Thwaites Glacier, West Antarctica, Version 1. [Indicate subset used]. Boulder, Colorado USA. NSIDC: National Snow and Ice Data Center. doi: http://dx.doi.org/10.7265/N5RJ4GC8. [Date Accessed].Detailed Data Description
Data are provided as an ASCII text file with a corresponding .pdf map.
The FTP directory ftp://sidads.colorado.edu/pub/DATASETS/AGDC/nsidc0518_carter_V01
contains two files:
drains.xyz
, an ASCII text file that contains the flow path data;drains.xyz.pdf
, a Portable Document Format file that contains a map of the flow paths.
drains.xyz
and drains.xyz.pdf
are 48 KB and 125 KB, respectively.
Thwaites Glacier, West Antarctica:
- Northernmost Latitude: 75°S
- Southernmost Latitude: 80°S
- Westernmost Longitude: 120° W
- Easternmost Longitude: 90° W
Spatial Resolution
Ice thickness data are spaced on a 15 km by 15 km ice thickness grid over the entire catchment of the glacier and sampled at approximately 15 m along track.
The AGASEA radar data from which this data set was derived were obtained between 7 December 2004 and 31 January 2005.
Table 2 below provides a description of each column in drains.xyz.
Column | Description |
---|---|
1 | Northing (polar stereographic -71 degrees) |
2 | Easting (polar stereographic -71 degrees) |
3 | Longitude (decimal degrees) |
4 | Latitude (decimal degrees) |
5 | Hydraulic Head (meters, WGS-84) |
6 | Surface Elevation (radar derived; meters, WGS-84) |
7 | Bed Elevation (radar derived; meters, WGS-84; 169 m/usec, no firn correction) |
8 | Flow Path Name (text) |
ASCII data are arranged in blocks, each representing a separate flow path. Blocks are separated by a line that begins with the ">" character followed by the flow path name, as illustrated by the following example from drains.xyz
:
Figure 1 is a map showing the flow paths. The file drains.xyz.pdf
contains a high-resolution version.

Software and Tools
Data can be read using standard spreadsheet software or with Global Mapping Tools, an open source collection of approximately 65 tools for manipulating geographic and Cartesian data sets.
Data Acquisition and Processing
Radar data were acquired by the Airborne Geophysical Survey of the Amundsen Embayment (AGASEA) expedition between 7 December 2004 and 31 January 2005, using the High Capability Radar Sounder Version 1 (HiCARS 1) VHF ice-penetrating radar system developed by the University of Texas Institute of Geophysics. HiCARS, which uses an 8 kW transmitter with a 1 μs FM chirp and a pulse repetition frequency of 6400 Hz, was operating with a 60MHz center frequency and 15 MHz of bandwidth. Across track beam width is controlled by the antenna beam pattern, and has a main cross-track half-power beam width of 12 degrees and side lobes at ±22 degrees.
Processing Steps
Radar data were down converted to a 10 MHz center frequency and recorded on two gain offset channels sampled at 50 MHz. Total dynamic range between the 2 channels is 90 dB. The data were coherently stacked 32 times to yield 16-bit, 3200-sample coherent records at 200 Hz, and during post-processing were range compressed with a synthetic chirp and filtered to remove 10 MHz coherent system noise.
Subglacial water flow paths were inferred by first using gridded ice thicknesses and bed elevations to generate a course map of hydrostatic potential, and then converting line-based ice thicknesses and bed elevations, derived from focused radar data, into lines of hydrostatic potential. Flow lines were constructed by selecting minima at obvious nickpoints and connecting them along fall lines of the grid.
References and Related Publications
Contacts and Acknowledgments
Dr. Sasha P. Carter
Scripps Institution of Oceanography
University of California, San Diego
9500 Gilman Drive
La Jolla, CA 92093
USA
Dr. Duncan A. Young
University of Texas at Austin
Institute for Geophysics
Mail Code R2200
10100 Burnet Road
Austin, TX 78758
USA
Dr. Donald D. Blankenship
University of Texas at Austin
Institue for Geophysics
Mail Code R2200
10100 Burnet Road
Austin, TX 78758
USA
This research was supported by the National Science Foundation (NSF) Office of Polar Programs (OPP) grant number 0636724.
Document Information
DOCUMENT CREATION DATE
May, 2012
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