Data Set ID:

ICESat-Derived Grounding Zone for Antarctic Ice Shelves, Version 1

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.

NSIDC does not archive these data.

  • Glaciers/Ice Sheets
  • Glaciers/Ice Sheets > Glacier Topography/Ice Sheet Topography
Data Format(s):
  • ASCII Text
Spatial Coverage:
N: -60, 
S: -80, 
E: 180, 
W: -180
Spatial Resolution:Not SpecifiedSensor(s):GLAS
Temporal Coverage:
  • 1 January 2003 to 31 December 2009
Temporal ResolutionNot specifiedMetadata XML:View Metadata Record
Data Contributor(s):Kelly Brunt, Helen Fricker, Laurence Padman, Shad O'Neel

Geographic Coverage

Please contact the data provider for the correct Data Citation for this data set.

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Detailed Data Description


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.

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File and Directory Structure

Data are available on the FTP site in the 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
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File Naming Convention

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



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.

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File Size

Files range in size from 1 KB to 70 KB.

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Total volume of the data set is approximately 200 KB.

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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

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Temporal Coverage

Data were collected from 2003 to 2009.

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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
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Software and Tools

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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).

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Sensor or Instrument Description

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

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References and Related Publications

Contacts and Acknowledgments

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

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

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

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

Document Information

Document Creation Date

12 August 2010

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