Great Lake Ice Cover Decreasing

The Alpena GLERL camera caught a boat moving thru the icy waters of Thunder Bay this afternoon shortly before 3 pm.  Great Lakes surface ice extent dropped 29.86% last Saturday to 18.88% today.  That’s a drop of 36.7%.  You’re probably saying, it hasn’t been that warm that long to melt all that ice.  Well, it’s not just temperature that determines how much ice is on the surface of the Great Lakes.  Wind plays a very important role.  We had a gust in Muskegon MI on Monday of 40 mph and on Tuesday up to 39 mph.  That wind helped break up ice on the Lake Michigan.

Here’s a graph of Great Lakes ice cover from the winter of 2013-14.  That winter we had a day with very strong winds on Feb. 21, 2014.  Grand Rapids had a peak gust that day of 60 mph and an average wind speed of 27.5 mph.  Holland recorded a gust of 56 mph.  The wind broke up a lot of ice on the Great Lakes, as you can see in that big dip in the graph.  But, as soon as the wind died down, the ice reformed and peak ice occurred in early March at 92.5%, the second highest ice extent on the lakes since 1973.  Only 1979 had a higher ice extent at 94.7%.  As you can see, the wind made a big difference.  I suspect with the cold air returning this weekend, that the ice extent will grow again and later this winter we’ll exceed the peak of 29.86% that we’ve had this winter.

By the way, the highest ice extent we had all last winter was 19.4%, so we’ve already exceeded that number.  I ksuspect we’ll beat the 33.8% greatest extent of the winter of 2015-16 before the end of January.  Peak ice extent usually comes sometime from mid-February to early March.

Comments are closed.