David Ljunggren, PlanetArk 3 Sep 08;
OTTAWA - A huge 19 square mile (55 square km) ice shelf in Canada's northern Arctic broke away last month and the remaining shelves have shrunk at a "massive and disturbing" rate, the latest sign of accelerating climate change in the remote region, scientists said on Tuesday.
They said the Markham Ice Shelf, one of just five remaining ice shelves in the Canadian Arctic, split away from Ellesmere Island in early August. They also said two large chunks totaling 47 square miles (76 square km) had broken off the nearby Serson Ice Shelf, reducing it in size by 60 percent.
"The changes ... were massive and disturbing," said Warwick Vincent, director of the Centre for Northern Studies at Laval University in Quebec.
Temperatures in large parts of the Arctic have risen far faster than the global average in recent decades, a development that experts say is linked to global warming.
"These substantial calving events underscore the rapidity of changes taking place in the Arctic," said Derek Mueller, an Arctic ice shelf specialist at Trent University in Ontario.
"These changes are irreversible under the present climate and indicate that the environmental conditions that have kept these ice shelves in balance for thousands of years are no longer present," he said in an e-mailed statement from the research team sent late on Tuesday.
Mueller said the total amount of ice lost from the shelves along Ellesmere Island this summer totaled 83 square miles (134 square km) -- more than three times the area of Manhattan island.
The figure is more than 10 times the amount of ice shelf cover that scientists estimated on July 30 would vanish from around the island this summer.
"Reduced sea ice conditions and unusually high air temperatures have facilitated the ice shelf losses," said Luke Copland of the University of Ottawa.
BLEAK FUTURE
"Extensive new cracks across remaining parts of the largest remaining ice shelf, the Ward Hunt, mean that it will continue to disintegrate in the coming years," he said.
The first sign of serious recent erosion in the five shelves came in late July, when sheets of ice totaling almost eight square miles (13 square km) broke off the Ward Hunt shelf. Since then that shelf has lost another 8.5 square miles (14 square km).
Ellesmere Island was once home to a single enormous ice shelf totaling around 3,500 square miles (5,633 square km). All that is left of that shelf today are the four much smaller shelves that together cover little more than 300 square miles (483 square km).
Scientists say the ice shelves, which contain unique ecosystems that had yet to be studied, will not be replaced because they took so long to form.
The rapid melting of ice in the Canadian Arctic archipelago worries Ottawa, which fears foreign ships might try to sail through the waters without seeking permission first.
Last week Prime Minister Stephen Harper said Canada would toughen reporting requirements for ships entering its waters in the Far North, where some of those territorial claims are disputed by the United States and other countries.
(Editing by Alan Elsner)
Major ice-shelf loss for Canada
BBC News 3 Sep 08;
The ice shelves in Canada's High Arctic have lost a colossal area this year, scientists report.
The floating tongues of ice attached to Ellesmere Island, which have lasted for thousands of years, have seen almost a quarter of their cover break away.
One of them, the 50 sq km (20 sq miles) Markham shelf, has completely broken off to become floating sea-ice.
Researchers say warm air temperatures and reduced sea-ice conditions in the region have assisted the break-up.
"These substantial calving events underscore the rapidity of changes taking place in the Arctic," said Trent University's Dr Derek Mueller.
"These changes are irreversible under the present climate."
Scientists reported in July that substantial slabs of ice had calved from Ward Hunt Ice Shelf, the largest of the Ellesmere shelves.
Similar changes have been seen in the other four shelves.
As well as the complete breakaway of the Markham, the Serson shelf lost two sections totalling an estimated 122 sq km (47 sq miles), and the break-up of the Ward Hunt has continued.
Cold remnants
The shelves themselves are merely remnants of a much larger feature that was once bounded to Ellesmere Island and covered almost 10,000 sq km (3,500 sq miles).
Over the past 100 years, this expanse of ice has retreated by 90%, and at the start of this summer season covered just under 1,000 sq km (400 sq miles).
Much of the area was lost during a warm period in the 1930s and 1940s.
Temperatures in the Arctic are now even higher than they were then, and a period of renewed ice shelf break-up has ensued since 2002.
Unlike much of the floating sea-ice which comes and goes, the shelves contain ice that is up to 4,500 years old.
A rapid sea-ice retreat is being experienced across the Arctic again this year, affecting both the ice attached to the coast and floating in the open ocean.
The floating sea-ice, which would normally keep the shelves hemmed in, has shrunk to just under five million sq km, the second lowest extent recorded since the era of satellite measurement began about 30 years ago.
"Reduced sea-ice conditions and unusually high air temperatures have facilitated the ice shelf losses this summer," said Dr Luke Copland from the University of Ottawa.
"And extensive new cracks across remaining parts of the Ward Hunt Ice Shelf mean that it will continue to disintegrate in the coming years."
Loss of ice in the Arctic, and in particular the extensive sea-ice, has global implications. The "white parasol" at the top of the planet reflects energy from the Sun straight back out into space, helping to cool the Earth.
Further loss of Arctic ice will see radiation absorbed by darker seawater and snow-free land, potentially warming the Earth's climate at an even faster rate than current observational data indicates.
19-square-mile ice sheet breaks loose in Canada
Charmaine Noronha, Associated Press Writer Yahoo News 3 Sep 08;
A chunk of ice shelf nearly the size of Manhattan has broken away from Ellesmere Island in Canada's northern Arctic, another dramatic indication of how warmer temperatures are changing the polar frontier, scientists said Wednesday.
Derek Mueller, an Arctic ice shelf specialist at Trent University in Ontario, told The Associated Press that the 4,500-year-old Markham Ice Shelf separated in early August and the 19-square-mile shelf is now adrift in the Arctic Ocean.
"The Markham Ice Shelf was a big surprise because it suddenly disappeared. We went under cloud for a bit during our research and when the weather cleared up, all of a sudden there was no more ice shelf. It was a shocking event that underscores the rapidity of changes taking place in the Arctic," said Mueller.
Mueller also said that two large sections of ice detached from the Serson Ice Shelf, shrinking that ice feature by 47 square miles — or 60 percent — and that the Ward Hunt Ice Shelf has also continued to break up, losing an additional eight square miles.
Mueller reported last month that seven square miles of the 170-square-mile and 130-feet-thick Ward Hunt shelf had broken off.
This comes on the heels of unusual cracks in a northern Greenland glacier, rapid melting of a southern Greenland glacier, and a near record loss for Arctic sea ice this summer. And earlier this year a 160-square mile chunk of an Antarctic ice shelf disintegrated.
"Reduced sea ice conditions and unusually high air temperatures have facilitated the ice shelf losses this summer," said Luke Copland, director of the Laboratory for Cryospheric Research at the University of Ottawa. "And extensive new cracks across remaining parts of the largest remaining ice shelf, the Ward Hunt, mean that it will continue to disintegrate in the coming years."
Formed by accumulating snow and freezing meltwater, ice shelves are large platforms of thick, ancient sea ice that float on the ocean's surface but are connected to land.
Ellesmere Island was once entirely ringed by a single enormous ice shelf that broke up in the early 1900s. All that is left today are the four much smaller shelves that together cover little more than 299 square miles.
Martin Jeffries of the U.S. National Science Foundation and University of Alaska Fairbanks said in a statement Tuesday that the summer's ice shelf loss is equivalent to over three times the area of Manhattan, totaling 82 square miles — losses that have reduced Arctic Ocean ice cover to its second-biggest retreat since satellite measurements began 30 years ago.
"These changes are irreversible under the present climate and indicate that the environmental conditions that have kept these ice shelves in balance for thousands of years are no longer present," said Mueller.
During the last century, when ice shelves would break off, thick sea ice would eventually reform in their place.
"But today, warmer temperatures and a changing climate means there's no hope for regrowth. A scary scenario," said Mueller.
The loss of these ice shelves means that rare ecosystems that depend on them are on the brink of extinction, said Warwick Vincent, director of Laval University's Centre for Northern Studies and a researcher in the program ArcticNet.
"The Markham Ice Shelf had half the biomass for the entire Canadian Arctic Ice Shelf ecosystem as a habitat for cold, tolerant microbial life; algae that sit on top of the ice shelf and photosynthesis like plants would. Now that it's disappeared, we're looking at ecosystems on the verge of extinction,' said Mueller.
Along with decimating ecosystems, drifting ice shelves and warmer temperatures that will cause further melting ice pose a hazard to populated shipping routes in the Arctic region — a phenomenon that Canada's Prime Minister Stephen Harper seems to welcome.
Harper announced last week that he plans to expand exploration of the region's known oil and mineral deposits, a possibility that has become more evident as a result of melting sea ice. It is the burning of oil and other fossil fuels that scientists say is the chief cause of manmade warming and melting ice.
Harper also said Canada would toughen reporting requirements for ships entering its waters in the Far North, where some of those territorial claims are disputed by the United States and other countries.
Canada's Arctic ice shelves break apart, drift away
Michel Comte Yahoo News 3 Sep 08;
Two ice shelves in Canada's far north have lost massive sections since August while a third ice shelf now is adrift in the Arctic Ocean, said researchers Wednesday who blamed climate change.
The entire 50 square-kilometer (19 square-mile) Markham Ice Shelf off the coast of Ellesmere Island broke away in early August and is now adrift, while two sections of the nearby Serson Ice Shelf detached, reducing its mass by 60 percent or 122 square kilometers (47 square miles).
Ward Hunt Ice Shelf, which halved in July, lost an additional 22 square kilometers (8.5 square miles).
"These changes are irreversible under the present climate and indicate that the environmental conditions that have kept these ice shelves in balance for 4,000 years are no longer present," said Trent University's polar expert Derek Mueller.
Canada's summer ice shelf losses now total 214 square kilometers (82.5 square miles), which is more than three times the area of Manhattan Island, the researchers said.
Extensive cracks in Ward Hunt, the largest remaining ice shelf, means it will continue to disintegrate in the coming years, said Luke Copland, director Ottawa University's cryospheric research lab.
In an interview with AFP, Copland blamed "very warm temperatures" and "reduced sea ice" for the crumbling ice shelves.
The sea ice usually braced the shelves and without it, wind and waves more easily broke them apart, he explained.
The coast of Ellesmere Island has also warmed an average of two degrees (Celsius) in the last 50 years, he said. In winter, temperatures are now five degrees warmer, making it more difficult for ice lost in summer to recover in winter.
"We see that warming is concentrated in the winter," Copland said. "It's part of global warming. When we warm up the planet it gets concentrated close to he poles."
"Usually the ice shelves would use the winter to recover from the previous summer. They would reform, ... but the ice shelf can't recover in the winter anymore."
"We have now reached a threshold where (the environment) is too warm for these ice shelves to exist anymore," he said. "What it tells us is that the Arctic is changing."
Mueller told AFP: "It underscores the rapidity of the changes, how quickly things are moving along in the Arctic."
"Its not just the ice shelves that are changing. These changes are occurring in concert with sea ice reduction and other indications of climate change," he said.
The Ellesmere ice shelves were formed some 4,500 years ago, composed of sea ice, accumulated snow and glacier ice up to 40 meters (131 feet) thick.
The detached pieces broke into numerous 'ice islands' (tabular icebergs) whose fate could take many forms, said researchers.
Martin Jeffries of the US National Science Foundation and University of Alaska Fairbanks, and who has studied the Ellesmere ice shelves since 1982, said they could float along the northern edge of Queen Elizabeth Islands toward the Beaufort Sea or enter the Canadian Archipelago.
The Canadian Ice Service is tracking the broken pieces.
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