Scientists see dramatic drop in Arctic sea ice

The reduction of perennial winter sea ice is the primary cause of this summer's fastest-ever sea ice retreat on record and subsequent smallest-ever extent of total Arctic coverage, the scientists said. Their findings appeared in the journal Geophysical Research Letters.

Meier said it would not be surprising that in the next 25 years -- far sooner than previously predicted -- that there might be an ice-free Arctic during the summer.

"I don't think you can get this kind of situation if you didn't have warming temperatures," Meier said, pointing to man-made emissions of carbon dioxide and other so-called greenhouse gases.

Mark Serreze, another researcher at the National Snow and Ice Data Centre, said in a statement, "Computer projections have consistently shown that as global temperatures rise, the sea ice cover will begin to shrink.

"While a number of natural factors have certainly contributed to the overall decline in sea ice, the effects of greenhouse warming are now coming through loud and clear," Serreze said.

Meier said satellite imagery showed no ice for several weeks in August and September along the Northwest Passage, which would enable vessels other than modern icebreakers to get through.

"The channels there were basically completely open," Meier said.