Ice-Penetrating Radar Data Across Siple Coast Grounding Lines

Summary

These data consist of ice-penetrating radar data collected on the ground across the grounding line near Siple Dome during the 2006 and 2007 Antarctic summer field seasons. Primarily, the data consist of low-frequency radar data (2 MHz, approximately 50 meter resolution) in order to observe deep internal layers and the ice-bed interface. The data set also contains one file with high-frequency (100 MHz, approximately 1 meter resolution) radar data, for a sub-region of one of the low-frequency radar profiles. Coincident kinematic GPS data were also collected to correct the radar data for topography along each profile. Radar profiles are typically approximately 20 km in length with the grounding line crossed centrally where possible.

Data are available via FTP in Matlab (.mat) format.

Citing These Data

The following example shows how to cite the use of this data set in a publication. For more information, see our Use and Copyright Web page.

The following example shows how to cite the use of this data set in a publication. List the principal investigators, year of data set release, data set title, publisher: NSIDC, and digital media.

Catania, G., and C. Hulbe. 2010. Ice-Penetrating Radar Data Across Siple Coast Grounding Lines. Boulder, Colorado, USA: National Snow and Ice Data Center. http://dx.doi.org/10.7265/N5M043BH.

Overview Table

Category	Description
Data format	Matlab (.mat)
Spatial coverage and resolution	Southernmost Latitude: 83°S Northernmost Latitude: 81°S Westernmost Longitude: 160°W Easternmost Longitude: 145°W
Temporal coverage and resolution	Data were collected between November 2006 and December 2007.
File naming convention	GPR.mat NB.mat SA.mat
File size	Files range in size from 19 MB to 260 MB.
Parameter(s)	Ice sheet surface elevation Ice sheet bed elevation Ice sheet internal stratigraphy Basal conditions along profiles
Procedures for obtaining data	Data are available via FTP.

Table of Contents

1. Contacts and Acknowledgments
2. Detailed Data Description
3. Data Access and Tools
4. Data Acquisition and Processing
5. References and Related Publications
6. Document Information

1. Contacts and Acknowledgments

Investigator(s)

Dr. Ginny Catania
University of Texas Institute for Geophysics
J. J. Pickle Research Campus, Bldg. 196
10100 Burnet Rd. (R2200)
Austin, Texas, USA
78758

Dr. Christina Hulbe
Portland State University
Department of Geology
P. O. Box 751
Portland, Oregon, USA
97207

Technical Contact

Acknowledgements

This research was supported by NSF OPP grant number 0538120.

2. Detailed Data Description

Format

Data are in Matlab (.mat) format.

File and Directory Structure

Data are available on the FTP site in the ftp://sidads.colorado.edu/pub/DATASETS/AGDC/nsidc0474_catania_V01/ directory. Within this directory, there are seven Matlab (.mat) files, containing radar profile data from Siple Dome. Six of the files contain low-frequency radar data from six profiles near Siple Dome. The profile locations are provided in the files, and are further defined in Catania, et. al, 2010. The remaining file, GPR.mat, contains high-frequency (100 MHz) radar data acquired along a portion of line SA (SA.mat) where a relict ice shelf rift and a relict Kamb Ice Stream shear margin is crossed.

File Naming Convention

Files are named according to the following convention and as described in Table 1:

NN.mat

Where:

Table 1. File Naming Convention

Variable	Description
NN	Radar profile ID
.mat	Matlab file extension

Example: SA.mat contains the radar profile for the radar track "SA."

The data set contains seven files. The radar profiles NA, NB, and NC, span a grounding line north of the Siple Dome (SDM) summit, while SA, SB, and SC span a grounding line south of the SDM summit. The radar profile identified as GPR is a high-frequency record that spans a sub-section of the SA line. Position data for each radar profile is available in its respective Matlab file.

File Size

Files range in size from 19 MB to 260 MB

Spatial Coverage

Data were collected at the Kamb Ice Stream, in the Siple Dome region of Antarctica. Detailed location information is available in the Matlab files, as well as in Catania, et. al., 2010.

Southernmost Latitude: 83°S
Northernmost Latitude: 81°S
Westernmost Longitude: 160°W
Easternmost Longitude: 145°W

Spatial Resolution

14 meters

Temporal Coverage

Data were collected between November 2006 and December 2007.

Parameter or Variable

The Matlab files contain raw and filtered data and coincident location information from GPS. Table 2 contains a description of arrays in the low-frequency radar data files, SA.mat, SB.mat, SC.mat, NA.mat, NB.mat, and NC.mat. Table 3 contains a description of arrays in the high-frequency data file, GPR.mat.

Parameter Description

Table 2. Radar Profile Array Description for Low-Frequency Data Files

Array	Description
Hpos	Horizontal position along profile (in meters) calculated from latitude/longitude position per trace
Xinc	1/sampling frequency (in units of seconds/sample)
Yinc	Amplifier setting on oscilliscope (units of Volts/bit)
data	Raw data has been demeaned or dewowed to remove the mean-average waveform. Form of data array is number of samples x number of traces. Sample length is typically 2500.
height	GPS-determined surface elevation at each radar trace
dday	Decimal day recorded in some cases to match radar and GPS data height: surface elevation from GPS data
lat	Latitude in decimal degrees for each trace
lon	Longitude in decimal degrees for each trace
time	Travel time (seconds)

Table 3. Radar Profile Array Description for the High-Frequency Data File, GPR.mat

Array	Description
Hpos	Horizontal position along profile (in meters) calculated from latitude/longitude position per trace
Xinc	Volts/bit for converting values
filtdata	Bandpassed data (between 50 and 150 MHz)
height	GPS-determined surface elevation at each radar trace
lat	GPS-determined latitude at each radar trace
lon	GPS-determined longitude at each radar trace
time	Two-way travel time for traces

 

Sample Data Record

Figure 1. Arrays in the File SA.mat

3. Data Access and Tools

Data Access

Data are available via FTP.

Volume

750 MB

Software and Tools

Data are accessible using Matlab software, available from http://www.mathworks.com.

Related Data Collections

• Singular Value Decomposition Analysis of Ice Sheet Model Output Fields
• Ice Motion and Topography Near Margin Areas of Kamb Ice Stream, Antarctica
• Compilation of Antarctic Radar Data, Siple Coast, 2000-2002

4. Data Acquisition and Processing

Theory of Measurements

The researchers used a custom built, low-frequency, short-pulse, ground-based radar system to image deep internal layers and the base of the ice sheet. They collected six radar profiles across the grounding line of Siple Dome. Three were located on the south side of the grounding line (SA,SB,SC) and three were located on the north side, (NA,NB,NC).

All Siple Dome radar data were collected using 3 MHz antennas which provide a pulse wavelength of 56 meters in ice and a horizontal resolution of 14 meters. Waveforms were averaged over a horizontal spacing of 3 meters. There was an 80 m separation between the transmitter and receiver sleds for the deep radar. The signal to noise ratio was improved in all profiles by removing the mean waveform, to limit interference due to instrumentation artifacts. The researchers also employed a higher-frequency (100 MHz) radar to image near-surface layers in some regions. Separation between transmit (Tx) and receive (Rx) is 1 m. Global Positioning System (GPS) data were used to compute elevation, latitude and longitude for every radar waveform.

For profiles NA and NB position data come from a geodetic quality Trimble GPS receiver that provides surface elevation relative to the WGS84 ellipsoid. In this region the ellipsoid is 45 m above the present-day sea level and the two radar profiles are corrected to reflect the true elevation of the ice surface above mean-sea level. Accuracy is less than 1 m in horizontal and approximately 2 m in vertical. The remaining Siple Dome radar profiles use position data from a lower-resolution real-time kinematic GPS solution which does not require an ellipsoid correction. Accuracy is roughly 10 m horizontal, 20 m vertical.

5. References and Related Publications

Catania, G., C. Hulbe and H. Conway. 2010. Grounding line basal melt rates determined using radar-derived internal stratigraphy, Journal of Glaciology Vol 56, No. 197.

The following related documents are available.

Table 4. Related Documents

Document	Description	URL
Antarctic Glaciological Data Center	Data Center Web site	http://nsidc.org/agdc/
The History of Grounding Line retreat in the Kamb Ice Stream Outlet Region	Project Description	http://www.ig.utexas.edu/people/staff/gcatania/research/active/glf/

6. Document Information

Acronyms

The following acronyms are used in this document.

Table 5. Acronyms and Abbreviations

Acronym	Description
FTP	File Transfer Protocol
NSIDC	National Snow and Ice Data Center
URL	Uniform Resource Locator

Document Creation Date

26 July 2010

Document URL

http://nsidc.org/data/docs/agdc/nsidc0474_catania/index.html