October 8, 2011


Evaporation from Lake Superior occurs only in the Winter

Ann Arbor, MI — Seasonal changes in Lake Superiorís water level have been thought to be related to changes in evaporation, but until recently, evaporation was only estimated or modeled. This study directly measured evaporation from the lake from a remote lighthouse, Stannard Rock, 39 km offshore continuously for over two years. Remote sensing was used to extent the Stannard Rock measurements across the lake. Surprisingly, during the summertime, there was virtually no evaporation; all of the strong summertime solar energy was used to warm the large volume of Lake Superiorís water. In the winter, when solar energy was weak, evaporation was large with the energy supplied from the lake itself; there is nearly a six-month delay between energy inputs and outputs. The wintertime lake-effect snow in the region is delayed summertime sunshine. Ice conditions vary significantly across the lake and between years, and also affect evaporation. Since evaporation cools the water surface, this promotes ice cover (especially near-shore) and limits the next summer seasonís solar energy inputs providing a lower heat content for the next winterís evaporation. This study shows that evaporation from this large lake variable in both space and time, and controlled by both by regional and distance factors coupled though complex feedbacks. Though a better understanding of these physical controls, we will be in a better position to predicted evaporation with climate change, and therefore better predict changes in water levels.

Original Publication Information

Results of these studies, "Evaporation from Lake Superior: 1. Physical Controls and Processes," and "Evaporation from Lake Superior: 2. Spatial Distribution and Variability," Ē, are reported by Peter Blanken, Christopher Spence, Newell Hedstrom, V. Fortin, H. Wilson and J.D. Lenters in Volume 37, No. 4, of the Journal of Great Lakes Research, published by Elsevier, 2011.


For more information about the study, contact Peter Blanken, Department of Geography, 260 UCB, University of Colorado, Boulder CO 80309-0260;, (303)-492-8310.

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.