Canada's Top Ten Weather Stories for 2012

6. The Big Melt

 A map of Canada with the affected regions highlighted.

The year 2012 will go down as one of extraordinary change across the Arctic, backed up by an ocean of evidence – the Arctic Ocean to be more precise, with sea ice that is becoming dramatically thinner, weaker and younger, and melting more easily. According to the United States National Snow and Ice Data Center, sea ice covering the Arctic Ocean dropped to 3.41 million square km on September 16, the lowest pan-Arctic sea ice extent reached since satellite measurements began in 1979 and down by 18 per cent from the previous low recorded during the historic 2007 melt season. The loss of ice in six months was stunning. The ice extent is now less than one-quarter of the Arctic Ocean and 49 per cent below the 1979-2000 average.

In Canadian waters, scientists with the Canadian Ice Service found that less than 8.5 per cent of the area was ice-covered on September 10, compared with a normal 20 to 25 per cent. In the southern route of the venerable Northwest Passage, there was no sea ice coverage at all. In the northern route, west of Resolute, 14 per cent of the Passage contained bands of hazardous multi-year ice. Everywhere, the ice has become thinner and less resistant to summer melt with the oldest, thickest and toughest ice quickly disappearing. The southern limit of multi-year ice is now only 10 degrees of latitude away from the North Pole. The Arctic’s once dominant perennial ice is being replaced by young, thin ice. Bucking the trend this year was Frobisher Bay, where there were significant delays in ice melting. With predominantly southeasterly winds over southern Nunavut, the ice persisted in the Bay until the end of August (setting a record for late ice melt) and along the western shore of Foxe Basin until late September.

Coast Guard ship travelling through icy waters.

Off the coasts of Newfoundland and Labrador it was the third winter in a row with low levels of sea ice. And there was hardly any ice in the Gulf of St. Lawrence. Owing to some unseasonable and lasting warmth, Great Lakes average ice cover in winter 2011-2012 was the lowest on record, dating back to the winter of 1972-1973. In usually ice-covered Lake Erie, only the Western Basin became thinly ice covered this year. Similar conditions on Lake Erie have been seen only in 1998 and 2002.