January 3, 2008


Watching Great Lakes Ice Cover from Space

Ann Arbor, MI — Satellites, orbiting the Earth more than 14 times a day, carry radars to take routine measurements over the Great Lakes. Such radars are useful to identify and map ice cover on lakes regardless of cloud cover or darkness. Ice cover has major impacts on regional climate, ecology, water level, coastal erosion, toxin distribution, as well as hydropower, fishing, and shipping industries.

"Translating the satellite radar data to ice cover information requires a signature library," said Son Nghiem, a scientist at the NASA Jet Propulsion Laboratory (JPL). "It is like a foreign language. We need to make a dictionary that can translate radar signatures to information pertaining to various ice types and use it to map ice cover over the Great Lakes," he added.

Radar signatures of ice were measured during a field experiment campaign conducted in the 1997 winter season across the Straits of Mackinac and Lake Superior using two different United States Coast Guard icebreaker vessels, the Biscayne Bay in February and the Mackinaw in March. Aboard these icebreakers, a JPL polarimetric C-band radar was used to make ice signature measurements. The JPL radar data together with field observations form a signature library that can be used to interpret satellite data for ice classification and mapping.

The signature library was used to identify and map the most common Great Lakes ice types in both ERS-2 and RADARSAT-1 satellite radar images. At look angles in the far range, thick brash ice, the most difficult for icebreaking operations and the most hazardous for ship navigation, can be uniquely detected by radar for wind conditions below the gale force. Moreover, the library of radar signatures is applicable to making maps of ice types from ENVISAT and the recently launched RADARSAT-2 satellite images as well.

Original Publication Information

Results of this study, study "Satellite SAR remote sensing of Great Lakes Ice Cover, Part 1. Ice backscatter signatures at C-band," and "Part 2. Ice Classification and Mapping" are reported by in the latest issue (Volume 33, No. 4, pp. 722-735 and pp. 736-750) of the Journal of Great Lakes Research, published by the International Association for Great Lakes Research, 2007.


For more information about the study, contact Son V. Nghiem, NASA Jet Propulsion Laboratory, California Institute of Technology, MS 300-235, 4800 Oak Grove Drive, Pasadena, CA 91109,, (818) 354-2892, or George A. Leshkevich, NOAA Great Lakes Environmental Research Laboratory, 2205 Commonwealth Blvd., Ann Arbor, MI 48105,, (734) 741-2265.

For information about the Journal of Great Lakes Research, contact Stephanie Guildford, Scientific Co-Editor, Large Lakes Observatory, University Minnesota Duluth, 2205 East Fifth Street, Duluth, Minnesota, 55812-2401;; (218) 726-8064.

Since 1967, IAGLR has served as the focal point for compiling and disseminating multidisciplinary knowledge on North America's Laurentian Great Lakes and other large lakes of the world and their watersheds. In part, IAGLR communicates this knowledge through publication of the Journal of Great Lakes Research, available to members in print and electronic form. A searchable archive of the journal is available online and includes the abstracts of articles from the journal's inception in 1975 through the most recent issue. In addition, complete articles are available to members who have signed up for an electronic subscription.