The Comings and Goings of Ice on the Lake
Ice coverage across all of southern Lake Michigan is a rare occurence. According to NOAA's Great Lakes Environmental Research Laboratory, the only year we are certain Lake Michigan approached being completely frozen over was 1979, when extended periods of low temperatures resulted in an extensive ice buildup in the southern half of the lake.
In an average year, ice covers a bit less than half of Lake Michigan¹s surface. Because the lake stretches about 300 miles from North to South, there is usually much open water over the deeper waters of the southern basin due to milder temperatures. Since airborne and satellite observations of lake ice began four decades ago, only two other years, 1977 and 1994, have seen periods when nearly 90% of the lake was ice-covered.
Typically on southern Lake Michigan ice formation is confined to the shallower, colder waters near the shores. However, this ice comes and goes, not only with cold spells and thaws, but also with changes in the wind across the lake. Below is a recent series of high resolution satellite images of southern Lake Michigan showing just how transitory the ice on this part of the lake can be.
This image is from January 15th. There is an extensive area of ice along the Illinois and Indiana shores that extends several miles out into the lake...
This is the next day, January 16th. Strong winds from the Northwest have started to push the ice away from the western shoreline, opening up a narrow gap of ice-free water...
The Northwest wind spread frigid arctic air across the region, and this image from January 18th shows that the gap along the western shore has filled back in with new ice...
This next image is from January 19th, when several inches of lake effect snow fell in Northwest Indiana...
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On January 20th North-Northeast winds brought lake effect snow into southern Cook County, and also pushed ice away from the Southwest Lower Michigan shore...
On January 21st, there were moderately strong winds out of the West and Southwest. These winds pushed ice away from the Illinois and Indiana shores...
The West winds persisted on January 22nd, pushing the ice even further away from the shore...
This picture from January 24th shows that new ice had formed on cold shallow waters along the shore, due to the return of very cold air across the region the previous day...
The image below is from the Harrison-Dever water intake crib off of downtown Chicago. It shows the ice covering the water close to shore the morning of January 24th...
On Sunday, January 25th, a light but persistant wind from the west once again moved much of the ice away from the western shores of the lake...
Another view from off shore of Chicago at sunset Sunday the 25th shows that much of the ice was once again gone from the near shore waters...
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