MONTREAL (AFP) - The "shocking" record loss of Arctic sea ice was Canada's top weather event in 2007, Canada's environment ministry said Thursday.  Each year for the past 12, Environment Canada has published a list of the top 10 climate or weather phenomena to impact Canada that year.  For 2007, "the dramatic disappearance of Arctic sea ice -- reported in September -- was so shocking that it quickly became our number one weather story," the ministry said in a statement.

Satellite images in September revealed that Arctic ice had shrunk to about four million square kilometers (2.4 million square miles), a 23 percent decrease from the previous record low of 5.3 million square kilometers (3.2 million square miles) in 2005.  The area of ice that melted roughly corresponds to the size of the Canadian province of Ontario or the country of South Africa.

"Canadians might remember 2007 as the year that climate change began biting deep and hard on the home front," the ministry said. 

The Northwest Passage -- an arctic maritime route that links the Atlantic and Pacific oceans -- was navigable for almost five weeks into August and September, an exceptional turn of events.

"In 2007, ships as small as sailboats could have plied the normally ice-infested waters of the venerable Passage -- and nearly 100 vessels did," the statement said.

Due to the delayed start, it will be harder for this winter's ice to reform, and more likely the ice will shrink even more next summer, it said.

To blame, it said, were "several years of favorable Arctic winds pushing old ice into the Atlantic, as well as persistent, year-round warming of the North."

It also noted a dramatic transformation of the Arctic from "a highly reflective white snow or ice to dark heat-absorbing sea water."

The last two winters were the warmest ever recorded in northern Canada, and five of the 10 warmest years in the last 60 have occurred since 2001, it said.

"Scientists are now even more convinced that the Arctic climate system is heading toward a more ice-free state during the summer months, and that human-caused global warming is playing a significant role," it said.

"While the disappearing ice is having an immediate impact on northern peoples, the effects of this unprecedented loss outside the Arctic is uncertain.

"What we do know is that ice exerts an enormous control on global climate and its sudden loss could have profound impacts on weather well beyond the Arctic's borders," it said.