Data Set ID:

Great Lakes Ice Charts, Version 1

These charts show ice extent and concentration three times weekly during the ice season, for all lakes except Ontario, from the 1973/74 ice season through the 2001/2002 ice season. Most charts are annotated to indicate data sources. The Straits of Mackinac, Green Bay, and Sault Ste. Marie are enlarged as insets; and in some cases, provided as separate charts. From 1973/74 through 1986/87, charts were prepared by the National Weather Service Forecast Office in Ann Arbor, Michigan. Beginning with the 1987/88 season, the National Ice Center (formerly known as the Navy/NOAA Joint Ice Center) in Suitland, Maryland prepared the charts. Charts are available as GIF files.

This is the most recent version of these data.

  • Snow/Ice > Ice Extent > ICE EXTENT
  • Snow/Ice > Lake Ice > LAKE ICE
  • Snow/Ice > River Ice > RIVER ICE
Data Format(s):
  • GIF
Spatial Coverage:
N: 49, 
S: 41, 
E: -79, 
W: -93
Spatial Resolution:
  • Varies
Temporal Coverage:
  • 1 December 1973 to 9 May 2002
Temporal Resolution2 dayMetadata XML:View Metadata Record
Data Contributor(s):National Snow & Ice Data Center, .

Geographic Coverage

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FTP data can be downloaded through a Web browser or command line via FTP. For help downloading data through an FTP client, go to the How to access data using an FTP client support page.

As a condition of using these data, you must cite the use of this data set using the following citation. For more information, see our Use and Copyright Web page.

National Snow & Ice Data Center, . 2004. Great Lakes Ice Charts, Version 1. [Indicate subset used]. Boulder, Colorado USA. NSIDC: National Snow and Ice Data Center. doi: [Date Accessed].

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Detailed Data Description

This data collection is being provided as is. The images in this data set were digitized from an analog collection of paper charts. NOAA@NSIDC believes these data to be of value but is unable to provide more complete documentation.

The analog material upon which this digital data set is based moved to the University of Colorado (CU) Libraries Archives in August 2018, where it is part of the Roger G. Barry glaciology collection.  

If you are interested in the analog collection, you can search for "Great Lakes Ice Charts" from the CU search interface, but be aware that it may not yet be catalogued, or it may be catalogued under a different name.  If you have questions, contact 

File Naming Convention

On the FTP site, the GIF files for each melt season are tarred together into one file of the form yy1_yy2.tar where yy1 is the 2-digit year of the beginning year of the melt season and yy2 is the 2-digit year of the end of the melt season.

The data files within the tar files are named according to the following convention. Note: Starting in 2000, some images are supplied as .jpg instead of .gif.



Variable Description
xx[x] 2-3 digit location code:

cis: All great lakes
el: Eastern Great Lakes including Lake Erie, Lake Huron, Georgian Bay, and North Channel
gbl: Green Bay
gl: All great lakes
ml: Whitefish Bay south to Detour, including Sault Ste. Marie and St. Mary's River south to Detour, Michigan
scr: St. Clair River
wl: Western Great Lakes including Lake Michigan and Superior

Note: Prior to the 1986-87 ice season, charts were organized by region. Beginning with the 1986-87 ice season and beyond, all regions were combined into a single chart for each date. Each chart then has a "gl" prefix in the file name to indicate "all" Great Lakes.
yy 2-digit year
mm 2-digit month
dd 2-digit day of month

Note: For the 01-02 melt season, ASCII text files of descriptions of the ice are provided as well as GIS .e00 files.

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Document Information

Document Author

NSIDC Technical Writer

Document Creation Date


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