"It wouldn't surprise me to see more calving this summer," said Derek Mueller of Trent University, who's been studying the Ward Hunt Ice Shelf off the north coast of Ellesmere Island for years.
In a development consistent with climate change theories and happenings elsewhere in the Arctic, an enormous icy plain about 20 square kilometres in size broke free sometime last week and began slowly drifting into the Arctic Ocean. The piece had been a part of the shelf for 3,000 years.
A crack in the shelf was first spotted in 2002. Last spring, a patrol of Canadian Rangers found the weakness had spread into an extensive network of cracks, some 40 metres wide and 18 kilometres long. The crack-riddled section of ice was like a jigsaw puzzle, with the pieces held in place only by each other
It wouldn't have taken much to work a chunk of the shelf free, said Mueller.
"Further changes were likely given the right conditions. We had open water in front of the ice shelf. We had a favourable current and we probably had a favourable wind."
Formed by accumulating snow and freezing meltwater, ice shelves are large platforms of thick, ancient sea ice that float on the ocean's surface. Ellesmere Island was once entirely ringed by a single enormous ice shelf that broke up in the early 1900s.
At 440 square kilometres in size and 40 metres thick, the Ward Hunt shelf is the largest of those remnants - even bigger than the Antarctic shelf that collapsed earlier this year and seven times the size of the Ayles Ice Shelf chunk that broke off in 2005 from Ellesmere's western coast.
Despite a period of stability in the 1980s, the Ward Hunt shelf and its characteristic corrugated surface has been steadily declining since the 1930s, said Mueller. Its southern edge has lost 20 square kilometres over the last six years.
Mueller now believes the Serson Ice Shelf, in an exposed position off Ellesmere's western coast, could be the next to start breaking up.
"It certainly wouldn't surprise me if something happened on the Serson. It's exposed right now. There's no ice around it."
Mueller is careful not to blame the Ward Hunt breakup specifically on climate change, but says it is consistent with the theory. The current Arctic climate certainly isn't reinforcing ice shelves.
"We're in a different climate now," he said. "It's not conducive to regrowing them. It's a one-way process."
It's the same all over the Arctic, said Gary Stern, co-leader of a major international research program on sea ice.
Speaking from the Coast Guard icebreaker Amundsen about 70 kilometres off the Mackenzie Delta, Stern said the Ward Hunt breakup is related to what he's seeing thousands of kilometres away.
He hasn't seen any ice in weeks. Plans to set up an ice camp last February had to be abandoned when usually dependable ice didn't form for the second year in a row.
"Nobody on the ship is surprised anymore," said Stern. "We've been trying to get the word out for the longest time now that things are happening fast and they're going to continue to happen fast."
Many scientists now believe that the Arctic will have ice-free summers by 2013 instead of 2030 as predicted by the International Panel on Climate Change. Annual ice loss since the 1970s has quickened from about 75,000 square kilometres every summer to about 1.4 million square kilometres, said Stern.
"It's all connected to the warming climate. Everything is connected together."
