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

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, 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

 

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

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.

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

• GLAS/ICESat L2 Antarctic and Greenland Ice Sheet Altimetry Data
• Antarctic 5-km Digital Elevation Model from ERS-1 Altimetry
• MODIS Mosaic of Antarctica (MOA) Image Map

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