Data Set ID:
NSIDC-0594

Radar Studies of Subglacial Lake Whillans and the Whillans Ice Stream Grounding Zone, Version 1

This data set includes ground-based, gridded, ice-penetrating radar thickness and basal reflection power, along with GPS coordinates, for two areas of Whillans Ice Stream: Subglacial Lake Whillans and the Whillans Ice Stream grounding zone.

NSIDC does not archive these data.

Parameter(s):
  • Snow/Ice > Ice Depth/Thickness > ICE DEPTH/THICKNESS
Data Format(s):
  • ASCII Text
Spatial Coverage:
N: -84.2, 
S: -84.3, 
E: -154, 
W: -164
Platform(s):FIELD SURVEYS
Spatial Resolution:Not SpecifiedSensor(s):RADAR
Temporal Coverage:
  • 1 December 2010 to 1 August 2012
Version(s):V1
Temporal ResolutionNot specifiedMetadata XML:View Metadata Record
Data Contributor(s):Robert Jacobel

Geographic Coverage

Please contact the data provider for the correct Data Citation for this data set.

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Detailed Data Description

Over 1600 line kilometers of ground-based, gridded, ice-penetrating radar and GPS data were collected at two locations on Whillans Ice Stream: Subglacial Lake Whillans and the Whillans Ice Stream grounding zone. Data were acquired using an impulse radar system operating at a center frequency of 5 MHz on grids with typical 1 km spacing (closer in some portions). The transmitter was a pulse generator operating at a 1 KHz pulse-repetition frequency with a pulse amplitude of 4 kV. The resistively tapered dipole antenna arms were each 10 m in length (20 m per pair) and the system was towed by snowmobile on two sleds with antenna center points separated by167 m. The digitizer-receiver was a two-channel, 200 MHz, 14-bit digitizing PCI board housed in a ruggedized military-grade computer. This board provides 84 dB of dynamic range for raw traces and a time accuracy of 5 ns, or approximately 0.5 m of ice thickness. Triggering for the digitizer was initiated by the air wave arrival and typically 1000 triggers were stacked (averaged) for each recorded waveform. At usual speeds of surface travel, this resulted in an average spacing of about 3 m per waveform. While the system has the capability to detect echoes from the basal interface at depths in excess of 3.5 km, in this deployment, depths averaged only about 750 m and internal reflecting horizons were imaged to the ice-bed interface. The first multiple of the bed reflection was also typically imaged where the ice was floating due to the high dielectric contrast across the ice--bed interface.

For more detailed information regarding the data, please see the author's papers in the References and Related Publications section of this document.

Format

Data are provided in the following formats:
ASCII Delimited Text (.txt
Joint Photographic Experts Group (.jpg)
Portable Document Format (.pdf)

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File and Directory Structure

Data are available on the FTP site in the ftp://sidads.colorado.edu/pub/DATASETS/AGDC/nsidc0594_jacobel/ directory. Within this directory there are five files. Two .txt files containing recorded radar waveform data, two .pdf files of maps with profile names and locations, and one .jpg file which is a sample profile radargram.

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File Naming Convention

The file names are self explanatory except for the two PDF files, which start with SLW (SLW_radar_lines_wnames.pdf) and WGZ (WGZ_Radar_Lines_wnames.pdf). SLW stands for the Subglacial Lake Whillans and WGZ stands for the Whillans Ice Stream grounding zone.

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File Size

File

Size

Radar_Profile_X-13_SLW.jpg

2031 KB

SLW_NSIDC_FINAL.txt

6448 KB

SLW_radar_lines_wnames.pdf

11414 KB

WGZ_NSIDC_FINAL.txt

9701 KB

WGZ_Radar_Lines_wnames.pdf

3728 KB

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Volume

35 MB

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Spatial Coverage

Whillans Ice Stream, West Antarctica
84.2° S to 84.3° S, 154° W to 164° W

Spatial Resolution

Conservatively: ±5 cm horizontal, ±10 cm vertical, ±5 m ice thickness

Projection and Grid Description

Polar Stereographic projection

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Temporal Coverage

Data were collected from 01 December 2010 to 08 January 2012.

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Parameter or Variable

Latitude (dd)
Longitude (dd)
Surface Elevation (mamsl-WGS-84)
Ice Thickness (m)
Basal Reflection Power (dB)

Sample Data Record

Figure 1 is sample data from the WGZ_NSIDC_FINAL.txt data file. The data in each column in the ASCII tab-delimited text file are as follows:

  • latitude (dd)
  • longitude (dd)
  • surface elevation (mamsl-WGS-84)
  • ice thickness (m)
  • relative basal reflection power (dB)
  • profile names and locations.
sample data file
Figure 1. Sample Data from the WGZ_NSIDC_FINAL.txt Data File

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Software and Tools

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Data Acquisition and Processing

Radar transmitter and receiver with 5 MHz dipole antennas were pulled along the surface by Snowmobiles in gridded profiles with typically 1 km spacing (closer in some locations). Typically 1000 traces were stacked for every ~3 m of surface travel and the resultant waveform was recorded along with position determined from dual-frequency, differential carrier phase GPS. Data processing included bandpass filtering using a fifth-order Butterworth filter from 5 to 20 Mhz, time correction for antenna separation, interpolation to standard trace spacing of 3 m, and two-dimensional time-wavenumber migration assuming a constant radar-wave speed in ice of 169 m/µs.

Ice thickness values were picked using a semi-autimated picker routine and converted to depth using a wave speed of 169 m/µs. Basal reflection power values were derived by integrating the squared amplitude of the basal echo and converting to dB (Gades et al. 2000).

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References and Related Publications

Contacts and Acknowledgments

Robert Jacobel
St. Olaf College
Physics Department
1500 St. Olaf Ave.
Northfield, MN 55057

Acknowledgments: 

This research was supported by the National Science Foundaton (NSF) Division of Polar Programs (POLAR) Grant Numbers 0838855 and 0838854.

Document Information

DOCUMENT CREATION DATE

October 2014

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