Satellite monitoring of lake ice breakup on the Laurentian Shield (1980-1994)
Lake ice breakup dates from 1980 to 1994 for 81 selected lakes and reservoirs in the U.S. upper Midwest and portions of Canada (60N, 105W to 40°N, 85OW) were determined employing analysis of 1,830 archival images from the visible band (0.54 to 0.70 pm) of the GOES-VISSR. The objectives were to investigate the utility of monitoring ice phenology as a climate indicator and to assess regional trends in lake ice breakup dates. The dates of image y represented the range available in the national archive at the time of this study. Comparison of satellite-derived breakup dates with available ground reference data revealed a mean absolute difference of + 3.2 days and a mean difference of -0.4 days, well within the natural variability in lake ice breakup dates (u +/- 12 days) for a single lake over time. The predominant spatial trends of mean ice breakup dates can be attributed to latitude and snowfall [R squared = 93 percent). Analysis of the pooled data for all 81 lakes revealed a significant (p \textless 0.001) trend toward earlier ice breakup dates. A11 of the individual lakes exhibiting significant trends toward earlier ice breakup from 1980 to 1994 are located in southern Wisconsin.