Grounding Line Strain Grid Surveys, Kamb Ice Stream, Antarctica

Summary

This data set provides the results from a strain grid survey deployed across the Kamb Ice Stream grounding line on the West Antarctic Ice Sheet. The grid was deployed in 2006 and resurveyed in 2007 using a Global Positioning System (GPS). Parameters measured include latitude, longitude, and height of each survey mark in the strain grid, as well as northing, easting, elevations, and displacement of each point during the year between surveys.

Data are available via FTP in Microsoft Excel (.xls) 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.

Hulbe, C. L.. 2011. Grounding Line Strain Grid Surveys, Kamb Ice Stream, Antarctica. Boulder, Colorado, USA: National Snow and Ice Data Center. http://dx.doi.org/10.7265/N5Z899C6.

Overview Table

Category	Description
Data format	Microsoft Excel (.xls) Portable Document Format (.pdf)
Spatial coverage and resolution	Southernmost Latitude: 82.86°S Northernmost Latitude: 82.78°S Westernmost Longitude: 154.71°E Easternmost Longitude: 155.51°E
Temporal coverage and resolution	November 2006 November 2007
File naming convention	KISgroundingline_GPS.xls
File size	131 KB
Parameter(s)	Station Name Latitude Longitude Height Easting Northing Elevation Displacements
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

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

Technical Contact

Acknowledgements

This research was supported by NSF Office of Polar Programs grant number 0538015.

2. Detailed Data Description

Format

Data are in Microsoft Excel (.xls) format.

File and Directory Structure

Data are available on the FTP site in the ftp://sidads.colorado.edu/pub/DATASETS/AGDC/nsidc0494_hulbe_V01/ directory. This data set contains one file, KISgroundingline_GPS.xls contains the measurements and displacement information for each site in the strain grid survey. The directory also contains a readme file in text format, 00README.txt.

Table 1 describes the information and parameters in individual worksheets within the Excel file.

Table 1. Description of Workheets in the KISgroundingline_GPS.xls File

Worksheet name	Data Description
2007 Lat Lon 2006 Lat Lon	These two worksheets contain location information for each survey point in 2006 and 2007, as well as for the base stations where fixed GPS receivers operated throughout each survey. They also include positioning errors. Parameters: Latitude Longitude Height
2007 ENZ 2006 ENZ	These two worksheets contain the GPS latititude and longitude for each site in 2006 and 2007, converted into easting and northing. Parameters: Northing Easting Elevation
Displacements	This worksheet contains the computed 2006 to 2007 displacements of the survey marks in the grid. Parameters: Station name Northing 2006 Easting 2006 Elevation 2006 Change in northing (dN) Change in easting (dE) Change in elevation (dZ) Direction of displacement vector (dir) Magnitude of displacement vector (mag)

File Size

The file is 131 KB.

Spatial Coverage

This data set covers the grounding line of the Kamb Ice Stream, also known as Ice Stream C, on the West Antarctic Ice Sheet.

Southernmost Latitude: 82.86°S
Northernmost Latitude: 82.78°S
Westernmost Longitude: 154.71°E
Easternmost Longitude: 155.51°E

Spatial Resolution

1 km

Temporal Coverage

The data consists of two annual surveys of a strain grid. The strain grid was deployed in November 2006 and resurveyed in November 2007.

Temporal Resolution

One year

Parameter or Variable

This data set contains the locations for each point in the strain grid survey, measured in both 2006 and 2007. It also contains the computed displacements between 2006 and 2007, for each point.

Parameter Description

Table 2. Parameter Description for the KISgroundingline_GPS.xls File

Parameter	Description
Point	Station name. The stations were deployed in 2006 and resurveyed in 2007, but the names remained the same.
Latitude	GPS-measured latitude in decimal degrees
Longitude	GPS-measured longitude in decimal degrees
Northing	Cartesian coordinates converted from latitude measurement
Easting	Cartesian coordinates converted from longitude measurement
Elevation	Elevation was calculated from the height measurement using the base station measurements.
dN	Change in northing
dE	Change in easting
dZ	Change in elevation
dir	Direction of displacement vector
mag	Magnitude of displacement vector

 

Sample Data Record

Point	Northing	Easting	Elevation	dN	dE	dZ	dir	mag
KA1	1282329.670	1662067.546	108.544	-0.077	0.061	-0.051	-51.61346042	0.098234413
KA2	1281527.884	1661464.518	108.985	-0.041	0.056	0.087	-36.20945675	0.069404611
KA3	1280658.332	1660882.114	110.748	-0.039	0.04	-0.018	-44.27477558	0.055865911
KA4	1279841.147	1660302.648	112.139	-0.037	0.014	0.008	-69.27444119	0.039560081
KA5	1278979.274	1659704.973	112.172	-0.055	0.015	-0.106	-74.74488138	0.057008771

This sample data record shows the first 5 records in the displacements worksheet.

Sample Image

Figure 1. This map shows the locations of the survey marks in the strain grid (green circles). Contour lines show surface elevation (in meters) from the GPS surveys. The black lines are the traces of strand cracks in the region where the ice goes from grounded (the KA side) to floating (the KK side).

3. Data Access and Tools

Data Access

Data are available via FTP.

Volume

The data file is 131 KB.

Software and Tools

Data are accessible using Microsoft Excel software.

Related Data Collections

• Ice-Penetrating Radar Data Across Siple Coast Grounding Lines
• Ice Motion and Topography Near Margin Areas of Kamb Ice Stream, Antarctica
• Ice Velocity Data from Ice Stream C, West Antarctica

4. Data Acquisition and Processing

Theory of Measurements

A strain grid is a set of survey marks (metal conduits planted vertically in the snow) that are set out in a grid with relatively uniform spacing, surveyed, and then resurveyed. Changes in the vector lengths among the poles are used to compute strain rates at centroids of quadrilaterals (or triangles) formed using adjacent survey marks.

For every survey, the researchers established two base stations that recoreded a continuous GPS signal while other GPS receivers roved around the grid. The rovers stopped at marks in the grid and occupied them for 15 to 20 minutes. The resulting network of vectors (between the two base stations and each of the rover stops) is used to calculate the relative positions of all the marks in the grid. Absolute positions are determined using data from the base stations.

 

5. References and Related Publications

Hulbe, C. L. and I. M. Whillans. 1994. Evaluation of strain rates on Ice Stream B, Antarctica, using GPS phase measurements. Annals of Glaciology, 20. 254-262.

Table 3 lists related documents and Web sites.

Table 3. Related Documents

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

6. Document Information

Acronyms

The acronyms used in this document are listed in Table 4.

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
.XLS	Microsoft Excel File Extension

Document Creation Date

June 21, 2011

 

Document URL

http://nsidc.org/data/docs/agdc/nsidc0494_hulbe/index.html