The Great Lakes between the United States and Canada were formed by the passage of ice at end of the last glacial period around 10,000 years ago. They are now being covered by near record ice once again (although, not not by glaciers.) Ice now covers more than 88% of the Great Lakes approaching the 90.7% of 1994 and the 94.7% record set in 1979.
The Great Lakes form the world’s largest group of fresh water lakes and contain 21% of the world’s surface fresh water. The area covered with ice is now approaching the total land area of Great Britain.
One interesting aspect to the ice coverage on the Great Lakes is how widely variable it has been from year to year. In 2012 the maximum ice coverage was only around 12%, rising only to 38% last year. The ice coverage over the last 40 years have been roughly 51%.