Airborne Laser Altimetry of the Thwaites Glacier Catchment, West Antarctica

Summary

This data set includes airborne altimetry collected over the catchment and main trunk of Thwaites Glacier, one of Antarctica's most active ice streams. The airborne altimetry comprises 35,000 line-kilometers sampled at 20 meters along track. The full dataset has an internal error of ±20 cm; a primary subset has an error of ±8 cm. We find a +20 cm bias with Geoscience Laser Altimeter System data over a flat interior region. These data will serve as an additional temporal reference for the evolution of Thwaites Glacier surface, as well as aid the construction of future high resolution Digital Elevation Models (DEM). Line data are available in space-delimited ASCII format and are available via FTP.

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.

If these data are used in a publication, they should be cited using the following reference: Young, D. A., S. D. Kempf, D. D. Blankenship, J. W. Holt, and D. L. Morse (in press), New airborne laser altimetry over the Thwaites Glacier Catchment, West Antarctica , Geochemistry, Geophysics, Geosystems, http://dx.doi.org/10.7265/N5HD7SK8.

To help us serve the scientific and cryospheric research communities, please acknowledge NSIDC: Data provided by the National Snow and Ice Data Center DAAC, University of Colorado, Boulder, CO."

Overview Table

Category	Description
Data format	Space delimited ASCII
Spatial coverage and resolution	Southernmost Latitude: 80 S Northernmost Latitude: 75 S Westernmost Longitude: 130 W Easternmost Longitude: 90 W
Temporal coverage and resolution	10 December, 2004, through January 29, 2005 (Summer only)
File size	161 MB
Parameter(s)	Ice sheet elevation
Procedures for obtaining data	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)

Duncan A.Young
University of Texas at Austin
Jackson School of Geosciences, Institute for Geophysics
J.J. Pickle Research Campus Bldg. 196
10100 Burnet Road (R2200)
Austin, TX 78758-4445 USA

Scott D. Kempf
University of Texas at Austin
Jackson School of Geosciences, Institute for Geophysics
J.J. Pickle Research Campus Bldg. 196
10100 Burnet Road (R2200)
Austin, TX 78758-4445 USA

Donald D. Blankenship
University of Texas at Austin
Jackson School of Geosciences, Institute for Geophysics
J.J. Pickle Research Campus Bldg. 196
10100 Burnet Road (R2200)
Austin, TX 78758-4445 USA

John W. Holt
University of Texas at Austin
Jackson School of Geosciences, Institute for Geophysics
J.J. Pickle Research Campus Bldg. 196
10100 Burnet Road (R2200)
Austin, TX 78758-4445 USA

David L. Morse
University of Texas at Austin
Jackson School of Geosciences, Institute for Geophysics
J.J. Pickle Research Campus Bldg. 196
10100 Burnet Road (R2200)
Austin, TX 78758-4445 USA

Technical Contact

Acknowledgements

This research was supported by National Science Foundation (NSF) Office of Polar Programs (OPP) grant 0230197 awarded to John Holt, Donald Blankenship and David Morse, OPP grant 0636724 awarded to Blankenship and Holt, the G. Unger Vetlesen Foundation and the Jackson School of Geosciences.

2. Detailed Data Description

Format

Space delimited ASCII with ten columns; 43 Mb after gzip compression.
Time(J2000 seconds)
Longitude
Latitude
ps71 meters eastings
ps71 northings
elevation (WGS-84)
Project
System
Transect
Quality Flag
Project indicates the project flown; most of these lines were THW; Unplanned transit flights fell under ASE1. System indicates the onboard acquisition system used; this is SJB0 for all of this data. Transect is the name of the flown line; normally all three terms are used to designate a flight line to maintain uniqueness among all seasons.

File Naming Convention

File name	File Size	Description
.dbase.gz	43 MB	compressed file
.txt	161 MB	space-delimited ASCII

File Size

161 MB ASCII
43 MB after gzip compression

Spatial Coverage

Thwaites Glacier, Smith Glacier and Haynes Glacier, West Antarctica

Southernmost Latitude: 80 S
Northernmost Latitude: 75 S
Westernmost Longitude: 95 W
Easternmost Longitude: 130 W

Spatial Resolution

1 cm resolution in elevation, 20 meters along track

Temporal Coverage

Collection period: 10 December 2004 through 29 January 2005 (Summer only)

Parameter or Variable

Ice sheet elevation

Parameter Description

Ice sheet elevation via laser altimetry

Sample Data Record

Time(J2000 seconds)	Longitude	Latitude	ps71 meters eastings	ps71 northings	Elevation (WGS-84)	Project	System	Transect	Quality Flag
157472167.727700	-124.793463	-76.072357	-1248629.329000	-867608.728800	2184.409372	THW	SJB0	X03a	PRIMARY
157472168.020600	-124.793730	-76.072517	-1248610.745000	-867604.463600	2184.638830	THW	SJB0	X03a	PRIMARY
157472168.312200	-124.794007	-76.072676	-1248592.173000	-867600.505700	2184.631137	THW	SJB0	X03a	PRIMARY
157472168.603500	-124.794287	-76.072833	-1248573.759000	-867596.735300	2184.690533	THW	SJB0	X03a	PRIMARY
157472168.892800	-124.794545	-76.072990	-1248555.635000	-867592.475200	2184.857183	THW	SJB0	X03a	PRIMARY
157472169.181900	-124.794771	-76.073149	-1248537.813000	-867587.396600	2184.900682	THW	SJB0	X03a	PRIMARY
157472169.471000	-124.795006	-76.073307	-1248519.964000	-867582.591300	2184.871665	THW	SJB0	X03a	PRIMARY
157472169.761600	-124.795253	-76.073466	-1248501.800000	-867577.967100	2185.149318	THW	SJB0	X03a	PRIMARY
157472170.052400	-124.795530	-76.073626	-1248483.190000	-867573.967300	2185.194623	THW	SJB0	X03a	PRIMARY
157472170.341700	-124.795796	-76.073787	-1248464.514000	-867569.589200	2185.277740	THW	SJB0	X03a	PRIMARY

Error Sources

Data gaps are due to clouds, excessively rough terrain (i.e. crevasses, rock) and poor GPS solutions. Lines lacking at least three cross overs were dropped as quality assessment was difficult. These data have not been tide corrected.

Quality Assessment

The Quality Flag (either 'PRIMARY' or 'SECONDARY') indicates whether the root mean square (RMS) crossovers values of the data was low enough to allow it to influence other data during leveling, or whether it should attempt to level to other data.

3. Data Access and Tools

Data Access

available via FTP

Volume

161 MB ASCII
43 MB gzip compression

Related Data Collections

• Subglacial Topography: Airborne Geophysical Survey of the Amundsen Sea Embayment, Antarctica

4. Data Acquisition and Processing

Sensor or Instrument Description

A Riegl LD90-3HiP nadir pointing distance ranger, sampling at 3.5 Hz, was used to collect the range data; K&RS, a differential dual carrier phase method, and kinematic GIPSY, a single receiver dual carrier phase method, was used to reduce the GPS positioning at 2 Hz and 1 Hz respectively. Trimble 5700 and Ashtech Z-Surveyor receivers on both the aircraft and at the bases were used for GPS acquisition. A Litton 92 ring laser gyro inertial navigation system (INS) provided attitude data, with a quoted angular resolution of 0.05˚.

Data Acquisition Methods

These data were collected on a DHC-8 Twin Otter flown out of camps in the Pine Island Glacier Catchment and on the Ross-Amundsen Sea Divide in 2004-05. Typical line spacing was 15 kilometers. The aircraft typical ground speed was 70 meters per second.

5. References and Related Publications

Holt, J. W., D. D. Blankenship, D. L. Morse, D. A. Young, M. E. Peters, S. D. Kempf, T. G. Richter, D. G. Vaughan, and H. Corr. 2006. New boundary conditions for the West Antarctic ice sheet: Subglacial topography of the Thwaites and Smith Glacier catchments. Geophysical Research Letters, 33(L09502), 10.1029/2005GL025561.

Blankenship, D. D., D. Morse, C. A. Finn, R. E. Bell, M. E. Peters, S. D. Kempf, S. M. Hodge, M. Studinger, J. C. Behrendt, and J. M. Brozena. 2001. Geological controls on the initiation of rapid basal motion for West Antarctic Ice Streams: A geophysical perspective including new airborne radar sounding and laser altimetry results, in The West Antarctic Ice Sheet: Behavior and Environment. Antarctic Research Series, vol. 77, edited by R. B. Alley and R. A. Bindschadler, pp. 105–121, American Geophysical Union.

Young, D. A., S. D. Kempf, D. D. Blankenship, J. W. Holt, and D. L. Morse (in press), New airborne laser altimetry over the Thwaites Glacier Catchment, West Antarctica, Geochemistry, Geophysics, Geosystems, 10.1029/2007GC001935. Diehl, T. M., J. W. Holt, D. D. Blankenship, D. A. Young, T. A. Jordan, and F. Ferraccioli (2008), First airborne gravity results over the Thwaites Glacier catchment, West Antarctica, Geochemistry, Geophysics, Geosystems, 8(Q04011), 10.1029/2007GC001878.

Diehl, T. M., J. W. Holt, D. D. Blankenship, D. A. Young, T. A. Jordan, and F. Ferraccioli (2008), Antarctic airborne gravity data: Free-Air Gravity Anomalies Over the Thwaites Glacier Catchment, West Antarctica. Boulder, Colorado USA: National Geophysical Data Center, Digital media. http://www.ngdc.noaa.gov/mgg/gravity/utig_agasea.html

The following related documents are available on NSIDC's Web site.

Related Documents

Document	Description	URL
Subglacial Topography: Airborne Geophysical Survey of the Amundsen Sea Embayment, Antarctica	Guide Document	http://nsidc.org/data/docs/agdc/nsidc0292_holt/index.html

6. Document Information

Acronyms and Abbreviations

The following acronyms and abbreviations are used in this document.

Acronyms and Abbreviations

FTP	File Transfer Protocol
NSIDC	National Snow and Ice Data Center
URL	Uniform Resource Locator
DEM	Digital Elevation Model
GPS	Global Positioning System
GIPSY	GPS-Inferred Positioning System
OPP	Office of Polar Programs

Document Creation Date

March 2008

Document URL

http://nsidc.org/data/docs/agdc/nsidc0334_young/index.html