Note: Data files were updated on 28 October, 2010, because of an interpolation problem. Contact NSIDC User Services for more information.

ICESat-Derived Grounding Zone for Antarctic Ice Shelves

Summary

This data set includes estimates of the location of the grounding zone of Antarctic ice shelves based on laser altimeter data acquired during the Ice, Cloud, and Land Elevation Satellite (ICESat) mission, October 2003 through October 2009. The estimates are based on ICESat repeat-track analysis, which can be used to detect the region of ice flexure across the grounding line, since each repeated pass is acquired at a different tidal phase. The technique provides estimates for the landward limit of flexure, the point where the ice becomes hydrostatically balanced, and the break-in-slope associated with the flexure.

Data files are available via FTP in ASCII text (.txt) 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, publisher: NSIDC, and digital media.

Brunt, K. M., H. A. Fricker, L. Padman, and S. O'Neel. 2010. ICESat-Derived Grounding Zone for Antarctic Ice Shelves. Boulder, Colorado USA: National Snow and Ice Data Center. http://dx.doi.org/10.7265/N5CF9N19.

Overview Table

Category Description
Data format ASCII text (.txt) format
Spatial coverage and resolution Southernmost Latitude: 80°S
Northernmost Latitude: 60°S
Westernmost Longitude: 180°W
Easternmost Longitude: 180°E
Temporal coverage and resolution Data used in this analysis were collected between 2003 and 2009
File naming convention ANTP_GZ.txt
Coates_GZ.txt

File size Files range in size from 1 KB to 70 KB.
Parameter(s) Landward limit of flexure
Point of hydrostatic balance of ice shelf
Break-in-slope associated with flexure
Latitude
Longitude
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

Investigators

Dr. Kelly M. Brunt
Cryospheric Sciences Branch, Code 614.1
NASA Goddard Space Flight Center
Greenbelt, Maryland 20771
USA

Dr. Helen A. Fricker
Scripps Institution of Oceanography,
UCSD 9500 Gilman Drive
Mail Code: 0225
La Jolla, California 92093
USA

Dr. Shad O'Neel
USGS Alaska Science Center
4210 University Drive
Anchorage, Alaska 99508
USA

Dr. Laurence Padman
Earth & Space Research
3350 SW Cascade Ave.
Corvallis, Oregon 97333
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

 

2. Detailed Data Description

Format

The data are in ASCII text (.txt) format. One additional image file, in .png format, provides an explanation of grounding zone anatomy and the codes. The image is also provided below, under Parameter Description.

File and Directory Structure

Data are available on the FTP site in the ftp://sidads.colorado.edu/pub/DATASETS/AGDC/nsidc0469_brunt_V01/ directory. Within this directory, there are nine ASCII text files and a readme file. The data files correspond to different locations along the Antarctic grounding zone, as described in Table 1.

Table 1. Locations of Data Files
Filename Location of File
ANTP_GZ.txt Antarctic Peninsula
Ronne_GZ.txt Filchner/Ronne Ice Shelf
Coates_GZ.txt Clockwise from Filchner/Ronne Ice Shelf through Coats Land
Maud_GZ.txt Clockwise from Coats Land through Queen Maud Land
Enderby_GZ.txt Clockwise from Queen Maud Land to Amery Ice Shelf
Amery_GZ.txt Amery Ice Shelf
EANT_GZ.txt From Amery Ice Shelf to Ross Ice Shelf
Ross_GZ.txt Ross Ice Shelf
PIG_GZ.txt Clockwise from Ross Ice Shelf to the Antarctic Peninsula


File Naming Convention

Files are named according to the following convention and as described in Table 2:

LOC_GZ.txt

Where:

Table 2. File Naming Convention
Variable Description
LOC Location
GZ Grounding Zone
.txt ASCII text file extension

Example: ANTP_GZ.txt is an ASCII text file containing grounding zone information for the Antarctic Peninsula.

File Size

Files range in size from 1 KB to 70 KB.

Spatial Coverage

This data set encompasses the Antarctic coast line.

Southernmost Latitude: 80°S
Northernmost Latitude: 60°S
Westernmost Longitude: 180°W
Easternmost Longitude: 180°E

Spatial Coverage Map

map showing the location of points in the data set
Figure 1. Map of the Antarctic Grounding Zone

Temporal Coverage

Data were collected from 2003 to 2009.

Parameter or Variable

Parameter Description

This data set consists of ASCII text files with four fields: longitude, latitude, track number, and code (1, 2, or 3), corresponding to specified points of flexure and hydrostatic balance.

Table 3 describes the codes used in the data set.

Table 3. Code and Point Descriptions
Code Point Name Description
1 F Landward limit of ice flexure
2 H Point where ice becomes hydrostatically balanced
3 I Break-in-slope associated with flexure

 

Figure 2 provides a visual explanation of the points described above.


image showing the anatomy of an ice sheet and location of points of interest
Figure 2. Anatomy of a Grounding Zone

 

Sample Data Record

The data are space-delimited and do not contain a header row. The four fields, from left to right, are longitude, latitude, track number, and code (1, 2, or 3).

-74.480517 -73.59472 108 1
-64.807816 -68.697001 10 1
-77.536906 -73.458606 123 1
-77.674675 -73.311815 123 1

 

3. Data Access and Tools

Data Access

Data are available via FTP.

Volume

Total volume of the data set is approximately 200 KB.

Related Data Collections

4. Data Acquisition and Processing

Theory of Measurements

The location of the grounding zone of Antarctica was estimated, using laser altimeter data acquired during the ICESat mission (October 2003 through October 2009). Estimates are based on ICESat repeat-track analysis, which can be used to detect the region of ice flexure across the grounding line since each repeated pass is acquired at a different tidal phase. The methods are described in more detail in Brunt, et. al., 2010. The technique provides estimates for the landward limit of flexure (point F), the hydrostatic balance point (point H), and the break-in-slope associated with the flexure (point I).

Sensor or Instrument Description

For more information about the ICESat data used to produce this data set, see the ICESat/GLAS Data Web site.

5. References and Related Publications

Fricker, H. A. and L. Padman. 2006. Ice Shelf Grounding Zone Structure from ICESat Laser Altimetry. Geophysical Research Letters, 33(15), L15502.

Fricker, H. A., R. Coleman, L. Padman, T. A. Scambos, J. Bohlander and K. M. Brunt. 2009. Mapping the Grounding Zone of the Amery Ice Shelf, East Antarctica using InSAR, MODIS, and ICESat. Antarctic Science, 21(5), 515–532.

Brunt, K. M., H. A. Fricker, L. Padman, T. A. Scambos, and S. O’Neel. 2010. Grounding Zone of Ross Ice Shelf Mapped using ICESat Laser Altimetry. Annals of Glaciology, 51(55), 71-79.

Scambos, T. A., T. M. Haran, M. A. Fahnestock, T. H. Painter, and J. Bohlander. 2007. MODIS-Based Mosaic of Antarctica (MOA) Data Sets: Continent-Wide Surface Morphology and Snow Grain Size. Remote Sensing of the Environment 111(2-3): 242-257, doi:10.1016/j.rse.2006.12.020.

The following related documents are available:

Table 4. Related Documents
Document Description URL
ICESat Data ICESat data information and access http://nsidc.org/data/icesat/
Antarctic Glaciological Data Center Antarctic data center Web site http://nsidc.org/agdc/

6. Document Information

Acronyms

The following acronyms are used in this document.

Table 5. Acronyms and Abbreviations
Acronym Description
FTP File Transfer Protocol
ICESat Ice, Cloud, and Land Elevation Satellite
NSIDC National Snow and Ice Data Center
URL Uniform Resource Locator

Document Creation Date

12 August 2010

Document URL

http://nsidc.org/data/docs/agdc/nsidc0469_brunt/index.html