The supplied chart below indicates the precentage of five North American great lakes ice cover during 20 years period from (1973) to (2012).
Moving to the Superior, in 1973 covered nearly, a quarter of ice which in 1992 to 2012 dropped to the almost, 15 percents. However, in Michigan the percentage decreased to approximately, less than a fifth in 1973 and in 2012 reached to roughly, 10 percents in contrast to the Superior that had the massive change in 1973 but then again, there was change intermittently from 1992 to 2012.
In Huron in,1973 reached to nearly, 27 percents and in, 1992 and 2012 jumped to almost, a fifth comparing to the Superior and Michigan which was below than 10 perecnts and 15 percents. That being said In Erie in, 1973 the cover of ice exceeded and reached the vertex which was less than a third and furthermore, from 1992 to 2012 reached to
the highest point which was roughly, 27 percents. Moving to the last lake Ontario remained steady in 1973 and 1992 to 2012 and collapsed in contrast with other four lakes in both periods of time in 1973 touched very small number and in 1992 to 2012 reached to even below than 5 percents.
As an overview trend, there was a massive change from Superior to Ontario during these periods In Erie in both,
1973 and 1992 to 2012 touched the apex and in Ontario touched the lowest point which was one in twenty and below than 5 percents.