Examining Wetland Evapotranspiration Sensitivities to Northern Lake Michigan Atmospheric Moisture Returns Following High and Low Ice Cover Years

Evapotranspiration (ET) is estimated via the Penman-Monteith method at two in-situ hydro-climate stations on the Beaver Island archipelago in Lake Michigan, U.S.A to examine ET sensitivities to lake-ice cover patterns. Beaver Island is a small island (approximately 21km x 10km) but it possesses various wetland ecosystems with large biodiversity that can be vulnerable to changes in climate. The Great Lakes ice cover data from the National Oceanic and Atmospheric Administration’s (NOAA) Great Lakes Environmental Research Laboratory (GLERL) and meteorological and hydrological data from NOAA’s Realtime Coastal Observation Network (ReCON) station at White Shoal Light are used to examine the relationship between ice cover and evaporation rates of northern Lake Michigan. A recent report by Great Lakes Integrated Sciences and Assessments (GLISA) demonstrates a new concept that high evaporation values (more heat loss) in Lake Superior from the preceding fall results in high ice cover and cooler water temperatures following ice breakup, and vice versa for low evaporation during the preceding fall. This concept is tested in northern Lake Michigan using NOAA’s GLERL and ReCON daily data for a high and low ice cover year to quantify atmospheric moisture and ET differences during these two extremes. Since ET is a measure of moisture output, for a high ice cover year, higher ET estimates prior to ice formation and lower ET estimates following ice breakup should be expected in order to represent the concept at question.