Lake Superior Ice Data
How does mean winter temperature affect length of season for lake ice? To investigate this question we
obtained seasonal ice observation data for a single gauge station (#9004) on Lake Superior. Data were reported
in the form of "first date of observed ice" and "last date of observed ice" -- from these dates
we computed the number of days of ice for each year at this station. We found temperature data from a nearby
National Climate Data Center weather station (#205816 in Michigan). The temperature data is compiled by the
United States Historic Climate Network (USHCN) a division of NOAA, but can be downloaded most easily through QELP data set #050.
The scatter in the data suggests that mean winter (December through April) temperature is not a very strong
predictor of the length of the ice season. There is some correlation in the data (we computed a linear regression
r value of -.42), but why not more? What other factors could affect the length of the ice season? Could
the mean December and mean April temperatures be a better predictor? Is there a different weather station
whose temperature data would correlate better with the ice data? Are there other climate factors (such as
wind, clouds, or solar radiation) that also play a part in the duartion of ice? What information can be gleaned
from the outliers on this scatterplot? These are all excellent questions that students might investigate, if only
at a rudimentary level.
Ice Data Source: National Snow and Ice Data Center: http://www.nsidc.org