RESEARCHERS STUDY LAKE SUPERIOR ICE DYNAMICS
Houghton, MI--Michigan Tech researchers have found that RADARSAT ScanSAR imagery can be a powerful tool for studying the dynamics of Great Lakes ice. ScanSAR observations of Lake Superior reveal a highly complex and dynamic ice environment, with the potential for rapid and widespread change.
Dr. Drew Pilant, research assistant professor of physics, and co-investigators Ashok Agarwal (MTU Remote Sensing Institute), Dr. Henry Santeford (Civil and Environmental Engineering), and Dr. Robert Davis (Cold Regions Research and Engineering Laboratory), have spent three years studying ice types and dynamics on America's greatest lake.
Lake Superior is the earth's largest lake (in area), containing approximately ten percent of the earth's liquid fresh water, and is of major ecological and economic significance. "Ice is present on the Great Lakes for two to four months a year, and presently it is the dominant control on a host of lake processes including heat loss, snow production, latent heat loss through evaporation, generation of lake-effect snow, and wind coupling with the water surface" says Pilant.
Satellite imaging radar is an important new technology for earth observation. The Radar instrument transmits a beam toward the earth, and measures the return signal reflected off the earth (or ice) surface. Radar sensors operate in the microwave portion of the electromagnetic spectrum; microwave energy passes through earth's atmosphere and clouds virtually unaffected, permitting day-night and all-weather imaging. This is critically important during the long dark days of winter in the Lake Superior region. The radar is sensitive to ice roughness, which yields an indication of ice type.
Using RADARSAT ScanSAR imagery to observe Lake Superior ice cover, the MTU team has collected information on ice type identification and drift detection, using an AVHRR (Advanced Very High Resolution Radiometer) for analysis. RADARSAT is unique in its ability to focus the radar beam in several different modes, from high resolution to low resolution. SAR is the satellite, the sensor of choice for lake and sea ice studies because of its all-weather, day or night viewing capability, and its sensitivity to relevant ice parameters such as roughness and wetness. "ScanSAR imagery of the Great Lakes, the first of its kind, allows us to observe the lakes at regional scales, yet with high spatial resolution compared to alternative satellite capabilities," Pilant says.
The Lake Superior environment is analogous to the polar marginal ice zone, disconnectedly unbounded on the margin and hence subject to rapidly juxtaposed episodes of compression, extension and wave action, according to Pilant.
Pilant believes that the ScanSAR imagery "has illuminated many new aspects of lake ice, and has greatly enhanced Great Lakes studies of plant and animal ecosystems, shoreline infrastructure, lake levels and navigation." Researchers are also now using snow and ice to look for indications of climate change due to anthropogenic (human-caused) global warming.
Successful completion of this study will lead to a better understanding of wintertime navigation on the Great Lakes, particularly with respect to commercial shipping; water levels for shipping and hydroelectricity generation; damage to shoreline infrastructure (e.g., bridges, docks), and municipal water supply management.
This project is being funded by a grant from the National Aeronautics & Space Administration (NASA).
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06/08/99-MTN111