Margin Migration Rates and Dynamics: Siple Coast Ice Streams

Summary

This product, based on prior data collected under NSF-OPP grant 8716604 (Echelmeyer and Harrison) and NSF-OPP grant 9117911 (Harrison), includes ice velocity data between stations S17 and UpB on the Upper Whillans Ice Stream, Siple Coast, West Antarctica, from January 1994 to January 1995. Velocities were measured using a total station, a surveying instrument that combines a digital theodolite and an Electronic Distance Measuring (EDM) device to measure horizontal and vertical angles, slope, and horizontal and vertical distances. Data are in ASCII and Excel formats, and are available via FTP.

Citing These Data

Truffer, M., and K. Echelmeyer. 2005. Margin migration rates and margin dynamics of the Siple Coast ice streams. Boulder, CO: National Snow and Ice Data Center. http://dx.doi.org/10.7265/N50K26HH.

Overview Table

Category	Description
Data format	Tab-delimited ASCII files and Excel file
Spatial coverage	Upper Whillans Ice Stream, Siple Dome, West Antarctica
Temporal coverage	January 1994 to January 1995
File size	gpsvel.txt: 376 bytes truffer_margin_velocities.txt: 670 bytes margin_velocities.xls: 15872 bytes
Parameter(s)	Ice velocity
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) Name and Title

Martin Truffer and Keith Echelmeyer
University of Alaska Fairbanks
Fairbanks, AK     USA

Technical Contact

Acknowledgements

This research was supported by NSF OPP award #0086997, Margin Migration Rates and Margin Dynamics of the Siple Coast Ice Streams.

2. Detailed Data Description

Format

Data are available as tab-delimited ASCII files and as Excel spreadsheets.

File Naming Convention

gpsvel.txt: 376 bytes
truffer_margin_velocities.txt: 670 bytes
margin_velocities.xls: 15872 bytes

File Size

gpsvel.txt: 376 bytes
truffer_margin_velocities.txt: 670 bytes
margin_velocities.xls: 15872 bytes

Spatial Coverage

Data were collected on the Whillans Ice Stream (83.57778°S, 138.14972°W), Siple Coast, West Antarctica.

Upper Left:	83.54415°S	134.9841°W
Lower Left:	83.21296°S	137.7229°W
Upper Right:	83.85934°S	138.0105°W
Lower Right:	83.51190°S	140.7206°W

Study Area Location Map

Following is a map of the study area with the stations labeled and the optical data track shown as a red line. The plot overlays a Moderate Resolution Imaging Spectroradiometer (MODIS) image of the upper Whillans Ice Stream area.

Temporal Coverage

Data were collected between January 1994 and January 1995.

Parameter or Variable

Unit of Measurement

Velocity measurements and errors are in meters per year (m/a).

Sample Data Record

The following sample shows the first five lines of "gpsvel.txt."

Station	Latitude(DMS)	Longitude(DMS)	Velocity(m/a)	Error	Azimuth
S17	83 34 40S	138 8 59W	2.76	0.10	N77W
I21	83 34 44S	138 5 51W	2.04	0.10	N67W
OutB	83 37 1S	138 3 31W	0.52	0.12	N56W
Fishhook	83 40 46S	138 22 28W	1.60	0.16	S65W

The following sample shows the first five lines of "truffer_margin_velocities.txt."

Distance (from center)	Speed (m/a)
1771	427.05
2610	423.40
3527	423.40
5100	419.97

Error Sources

Estimated errors for the GPS data range from 0.10 to 0.30 m/a. Maximum estimated errors for the optical data are approximately 0.2 m/a.

3. Data Access and Tools

Data Access

Data are available via FTP.

4. Data Acquisition and Processing

Sensor or Instrument Description

Velocities were measured using a total station, a surveying instrument that combines a digital theodolite and an Electronic Distance Measuring (EDM) device to measure horizontal and vertical angles, slope, and horizontal and vertical distances. An EDM is a device mounted on the top of the total station that sends out a pulse of light. The EDM measures the time it takes for the light to travel from the EDM to a prism, bounce off of the prism, then return to the EDM. This measurement is displayed as distance, but it is really a measurement of time (U.S. Army Corps of Engineers 2002).

5. References and Related Publications

Echelmeyer, K.A., W.D. Harrison, C. Larsen, and J.E. Mitchell. 1994. The role of the margins in the dynamics of an active ice stream. Journal of Glaciology 40(136): 527-538.

Echelmeyer, K.A. and W.D. Harrison. 1999. Ongoing margin migration of Ice Stream B, Antarctica. Journal of Glaciology 45(150): 361-369.

Harrison, W.D, K.A. Echelmeyer, and C.F. Larsen. 1998. Measurement of temperature in a margin of Ice Stream B, Antarctica: implications for margin migration and lateral drag. Journal of Glaciology 44(148): 615-624.

Truffer, M. and K.A. Echelmeyer. 2003. Of icestreams and isbrae. Annals of Glaciology 36: 67-72.

U.S. Army Corps of Engineers. 2002. "Angle and Distance Observations - Total Stations and EDM." In Structural Deformation Surveying. Engineer Manual 1110-2-1009. [View PDF.]

6. Document Information

List of Acronyms

The following acronyms are used in this document:

ASCII: American Standard Code for Information Interchange
FTP: File Transfer Protocol
EDM: Electronic Distance Measuring
GPS: Global Positioning System
MODIS: Moderate Resolution Imaging Spectroradiometer
NSF: National Science Foundation
NSIDC: National Snow and Ice Data Center

Document Creation Date

March 2005

Document Revision Date

March 2005

Document Review Date

March 2005

Document URL

http://nsidc.org/data/docs/agdc/nsidc0263_truffer/index.html