GPS-Measured Ice Velocities and Strain Data from the Ross and Amundsen Sea Ice Flow Divide, West Antarctica

Summary

This data set includes ice flow velocities and strain configurations, from GPS measurements on the West Antarctic Ice Sheet (WAIS) Divide. Ninety markers installed in the firn were measured during two consecutive field seasons running from 2005-2006 and 2006-2007. The markers were located in 150 by 60 km area, with smaller clusters of five markers located within about 10 km of each other. Consecutive Global Positioning System (GPS) measurements were used to derive velocity for each marker. Strain configurations were estimated by differentiating a linear fit of the data at each marker cluster.

Data are available via FTP as ASCII text (.txt ) files in comma separated value 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.

Matsuoka, K., A. Rasmussen, and D. Power. 2011. GPS-Measured Ice Velocities and Strain Data from the Ross and Amundsen Sea Ice Flow Divide, West Antarctica. Boulder, Colorado, USA: National Snow and Ice Data Center. http://dx.doi.org/10.7265/N5222RQ8.

Overview Table

Category	Description
Data format	ASCII text (.txt ) files in comma separated value format
Spatial coverage and resolution	Southernmost Latitude: 79.6401°S Northernmost Latitude: 78.7489°S Westernmost Longitude: 115.457°W Easternmost Longitude: 109.128°W
Temporal coverage and resolution	Data were collected during two Antarctic field seasons from 2005-2006 and 2006-2007.
File naming convention	WAISDivide_strain.txt WAISDivide_velocity.txt
File size	Total volume is 11 KB.
Parameters	GPS Velocity Strain Configuration
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

Investigators

Dr. Kenichi Matsuoka
Norwegian Polar Institute
Fram Centre
NO-9296 Tromsø
Norway

Donovan Power
Department of Earth and Space Sciences
Box 351310
University of Washington
Seattle, WA 98195
USA

Dr. Al Rasmussen
Department of Earth and Space Sciences
Box 351310
University of Washington
Seattle, WA 98195
USA

Technical Contact

Acknowledgements

This research was supported by the National Science Foundation (NSF) Office of Polar Programs (OPP) grant number 0440847.

2. Detailed Data Description

Format

Data are provided as ASCII text (.txt ) files in comma separated value format.

File and Directory Structure

Data are available on the FTP site in the ftp://sidads.colorado.edu/pub/DATASETS/AGDC/nsidc0503_matsuoka_V01/ directory. Within this directory, there are two data files:

• WAISDivide_velocity.txt provides GPS velocity data.
• WAISDivide_strain.txt provides strain configuration data
  

File Size

Data volume is a total of 11KB.

Spatial Coverage

Data were collected on the West Antarctic Ice Sheet.

Southernmost Latitude: 79.6401°S
Northernmost Latitude: 78.7489°S
Westernmost Longitude: 115.457°W
Easternmost Longitude: 109.128°W

Spatial Coverage Map

Figure 1. a. Map of the Antarctic Ice Sheet showing broad location of study area (b)
b. Regional surface topography (contours) and ice thickness (background color) in the WAIS Divide area: Gray rectangle indicates study area (c).Thick contours are drawn at 500 m intervals, and thin contours are drawn at 100 m. Byrd and WAIS Divide ice core sites are shown with white crosses. Surface topography is from Liu et al. 1999, and ice thickness is a composite of a continental BEDMAP model (Lythe et al., 2001) and a regional model by Support Office for Aerogeophysical Research (Morse et al., 2002).
c. Local surface topography (contours) and ice thickness (background color) in the WAIS Divide area, along with site names.
White circles show polarimetric radar measurement sites, and GPS ice-motion measurement sites are shown with blue circles.
Ninety-eight GPS markers were installed for mass balance study in the vicinity of the flowline through WAIS Divide core site, shown with blue dots (Conway and Rasmussen, 2009). Airborne along-flow radar profiles used for englacial attenuation analysis are shown with gray curves (Matsuoka et al., 2010).

Spatial Resolution

GPS measurements were made in clusters of five, located within about 10 km of each other. In total the marker clusters span a 150 km by 60 km area including the WAIS Divide deep ice coring site.

Temporal Coverage

Data were collected during two Antarctic field seasons from 2005-2006 and 2006-2007.

Parameter or Variable

This data set provides GPS velocity and strain configuration data. Table 1 describes the parameters for velocity data. Table 2 describes the parameters for the strain configuration data, which were derived from the velocity data.

Parameter Description

 

Table 1. Parameter Description for the WAISDivide_velocity.txt File

Parameter	Description
Site Name	Name of site
Elevation	Elevation in meters above WGS84 ellipsoid, measured in the first year
Latitude	Latitude in decimal degree (WGS84) measured the first year
Longitude	Longitude in decimal degree (WGS84) measured the first year
Azimuth	Angle (in degrees) of flow vector measured counter-clockwise from true north
Speed	Speed in meters per year

 

Table 2. Parameter Description for the WAISDivide_strain.txt File

Parameter	Description
Site Name	Name of marker cluster
Latitude	Latitude in decimal degree (WGS84) of the center marker of each cluster, measured the first year
Longitude	Longitude in decimal degree (WGS84) of the center marker of each cluster, measured the first year
Elevation	Elevation (meters above WGS84 ellipsoid) of the central marker at each cluster
Strain Configurations (7 columns)	Strain configurations are derived in units of (year)-1: Divergence Curl Stretching Shear Deformation Extension Compression
Theta	Angle (rad) of the stretching axis measured clockwise from local UTM X-positive axis

 

Sample Data Record

This sample data record shows the first 4 rows of the WAISDivide_velocity.txt file

Name	Elevation	Lattitude	Longitude	Azimuth	Speed
CE1_A	1776.2	79.089102442S	111.932826069W	18.2	2.89
CE1_B	1779.08	79.130355900S	111.835434950W	16.9	2.2
CE1_C	1781.21	79.148821914S	112.054192125W	21.5	1.6
CE1_D	1779.53	79.107454058S	112.150893425W	22.2	2.07

 

This sample data record shows the first 4 rows of the WAISDivide_strain.txt file

site name	Lattitude (degree)	Longitude (degree)	elevation (m)	divergence (year-1)	curl (year-1)	stretching (year-1)	shear (year-1)	deformation (year-1)	extension (year-1)	compression (year-1)	theta (rad)
CE1	79.118552239S	111.993470842W	1780.66	1.50E-04	-4.30E-05	1.62E-04	1.31E-04	2.09E-04	1.80E-04	-2.91E-05	0.3402
S-E30	79.071715000S	110.940295556W	1763.77	8.97E-05	-1.19E-04	2.75E-04	3.26E-04	4.26E-04	2.58E-04	-1.68E-04	0.4354
N-E15	78.834677472S	113.740722167W	1799.78	2.39E-04	-2.81E-05	-8.88E-05	6.31E-05	1.09E-04	1.74E-04	6.49E-05	1.2618
N-Div	78.928057139S	114.245306417W	1809.86	1.31E-04	1.10E-06	-7.37E-05	9.63E-05	1.21E-04	1.26E-04	5.10E-06	1.112

 

3. Data Access and Tools

Data Access

Data are available via FTP.

Volume

Total volume of the data set is 11 KB.

Related Data Collections

• Polarimetric Radar Data from the Ross and Amundsen Sea Ice Flow Divide, West Antarctica (NSIDC-0496)

4. Data Acquisition and Processing

Theory of Measurements

Ninety markers installed in the firn were measured twice, during two consecutive field seasons (2005-2006 and 2006-2007), using L1/L2 geodetic GPS receivers. The markers were installed in 18 clusters of 5 markers, located within about 10 km of each other.

Velocity was derived for each marker based on the two measurements. Strain configuration data were obtained by differentiating a linear fit of these data at each marker cluster.

Sensor or Instrument Description

L1/L2 geodetic Global Positioning System (GPS) receivers

5. References and Related Publications

The following related documents are available

Table 3. Related Documents

Document	Description	URL
Antarctic Glaciological Data Center	Data Center Web site	http://nsidc.org/agdc/

6. Document Information

Acronyms

The following acronyms are used in this document.

Table 4. Acronyms and Abbreviations

Acronym	Description
FTP	File Transfer Protocol
GPS	Global Positioning System
NSIDC	National Snow and Ice Data Center
URL	Uniform Resource Locator
UTM	Universal Transverse Mercator
WAIS	West Antarctic Ice Sheet
WGS84	World Geodetic System 84

Document Creation Date

29 August 2011

Document URL

http://nsidc.org/data/docs/agdc/nsidc0503_matsuoka/index.html