The article states that Lake Superior was not ice free until June 6 this year, according to the National Ice Center. The relatively high areal extent of ice coverage this year has never been seen in the 40 years of recorded data.

“At the end of April 2014, for example, roughly 23% of Lake Huron and 10% of Lake Michigan were covered in ice, whereas more than half of Lake Superior (roughly 51%) was covered in ice (Figure 1). Prior to 2014, the highest percentage of late spring ice cover on Lake Superior was recorded (at roughly 30%) in April 1979 (Figure 2); at that time, ice cover on the other Great Lakes was at or very close to 0%. At no time in the 40-year record has there been significant ice cover on Lakes Michigan, Erie, and Ontario in late April, and in only a few years has significant ice cover been reported in late April on Lake Huron,” the article states.

Although spring 2014 conditions on the Great Lakes contrast sharply with those of the 40-year record, they are particularly unusual relative to conditions over the past 15 years.

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