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

We kindly request that you cite the use of this data set in a publication using the following citation example. 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

NSIDC User Services
National Snow and Ice Data Center
CIRES, 449 UCB
University of Colorado
Boulder, CO 80309-0449  USA
phone: +1 303.492.6199
fax: +1 303.492.2468
form: Contact NSIDC User Services
e-mail: nsidc@nsidc.org

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

map showing straing grid sites
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

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