leftchick
07-30-2008, 05:21 AM
Break marks latest in erosion that has whittled 9,000 square kilometres down to 1,000 over past century
http://www.theglobeandmail.com/servlet/story/RTGAM.20080729.wice29/BNStory/National/home?pageRequested=all&print=true
From Tuesday's Globe and Mail
July 29, 2008 at 3:39 AM EDT
A four-square-kilometre chunk has broken off Ward Hunt Ice Shelf - the largest remaining ice shelf in the Arctic - threatening the future of the giant frozen mass that northern explorers have used for years as the starting point for their treks.
Scientists say the break, the largest on record since 2005, is the latest indication that climate change is forcing the drastic reshaping of the Arctic coastline, where 9,000 square kilometres of ice have been whittled down to less than 1,000 over the past century, and are only showing signs of decreasing further.
"Once you unleash this process by cracking the ice shelf in multiple spots, of course we're going to see this continuing," said Derek Mueller, a leading expert on the North who discovered the ice shelf's first major crack in 2002.
Dr. Mueller was part of a team monitoring ice along the northern coast of Ellesmere Island last April that discovered deep new cracks - 18 kilometres long and 40 metres wide - on the edge of Ward Hunt Ice Shelf, a 350-square-kilometre mass of ice that joins tiny Ward Hunt Island to the bigger Ellesmere. The cracks indicated a split was likely coming.
graphic
Enlarge Image
Internet Links
* DAAC study: Breakup of the Ward Hunt Ice Shelf Popup
The Globe and Mail
"It may weaken over time; it may melt away slowly, then all of a sudden you pass this threshold," Dr. Mueller said. "It's like a bar of soap. If you use the soap over and over again, it gets thinner and thinner. Then all of a sudden, it could break.
"Nobody knew when it would happen," he said, adding that specific conditions were required to enable it, including "offshore wind and a bit of open water in front of the ice shelf."
Sami Soja, a Kingston-based surveyor on contract to Parks Canada, was working on the island last week and was one of the first to witness the breakup.
"We hiked up [a peak] on the island, which is probably only about seven kilometres wide, ... and you could see those big cracks along it," he said, adding that, when he hiked back to the same point a few days later, "it was like, wow, something's totally different out there."
When Mr. Soja's team was airlifted off the island Sunday, they asked the pilot to fly over the ice mass so they could see the change from a better vantage point. From the air, he said, the group could see "a chunk was gone."
Trudy Wohlleben, a sea-ice forecaster with the Canadian Ice Service, said the chunk could float in the Beaufort Gyre, an ice-clogged, clockwise current in the Western Arctic, for some time and is unlikely to be an imminent danger to ships.
She and her colleagues are still working to establish what wind conditions were like when the ice broke away, but determining the time has proven tricky.
At this point, she said her team is confident the ice mass broke off last Wednesday or Thursday.
"There were southerly winds that pushed the sea ice offshore and probably helped break it off," she said.
"[Now] there's kind of an opening between the bulk of sea ice and the coast of Ellesmere. Last week that wasn't there."
Warwick Vincent, director of Laval University's Centre for Northern Studies, has had students monitoring conditions on the ice shelf for years.
He called the ice break "a significant event" that the shelf has been building toward since it began gradually thinning during the 1950s. Since then, over a 40-year period, the shelf thinned from 70 metres in the early 1950s to about 35 metres in the 1990s, Dr. Vincent said.
http://www.theglobeandmail.com/servlet/story/RTGAM.20080729.wice29/BNStory/National/home?pageRequested=all&print=true
From Tuesday's Globe and Mail
July 29, 2008 at 3:39 AM EDT
A four-square-kilometre chunk has broken off Ward Hunt Ice Shelf - the largest remaining ice shelf in the Arctic - threatening the future of the giant frozen mass that northern explorers have used for years as the starting point for their treks.
Scientists say the break, the largest on record since 2005, is the latest indication that climate change is forcing the drastic reshaping of the Arctic coastline, where 9,000 square kilometres of ice have been whittled down to less than 1,000 over the past century, and are only showing signs of decreasing further.
"Once you unleash this process by cracking the ice shelf in multiple spots, of course we're going to see this continuing," said Derek Mueller, a leading expert on the North who discovered the ice shelf's first major crack in 2002.
Dr. Mueller was part of a team monitoring ice along the northern coast of Ellesmere Island last April that discovered deep new cracks - 18 kilometres long and 40 metres wide - on the edge of Ward Hunt Ice Shelf, a 350-square-kilometre mass of ice that joins tiny Ward Hunt Island to the bigger Ellesmere. The cracks indicated a split was likely coming.
graphic
Enlarge Image
Internet Links
* DAAC study: Breakup of the Ward Hunt Ice Shelf Popup
The Globe and Mail
"It may weaken over time; it may melt away slowly, then all of a sudden you pass this threshold," Dr. Mueller said. "It's like a bar of soap. If you use the soap over and over again, it gets thinner and thinner. Then all of a sudden, it could break.
"Nobody knew when it would happen," he said, adding that specific conditions were required to enable it, including "offshore wind and a bit of open water in front of the ice shelf."
Sami Soja, a Kingston-based surveyor on contract to Parks Canada, was working on the island last week and was one of the first to witness the breakup.
"We hiked up [a peak] on the island, which is probably only about seven kilometres wide, ... and you could see those big cracks along it," he said, adding that, when he hiked back to the same point a few days later, "it was like, wow, something's totally different out there."
When Mr. Soja's team was airlifted off the island Sunday, they asked the pilot to fly over the ice mass so they could see the change from a better vantage point. From the air, he said, the group could see "a chunk was gone."
Trudy Wohlleben, a sea-ice forecaster with the Canadian Ice Service, said the chunk could float in the Beaufort Gyre, an ice-clogged, clockwise current in the Western Arctic, for some time and is unlikely to be an imminent danger to ships.
She and her colleagues are still working to establish what wind conditions were like when the ice broke away, but determining the time has proven tricky.
At this point, she said her team is confident the ice mass broke off last Wednesday or Thursday.
"There were southerly winds that pushed the sea ice offshore and probably helped break it off," she said.
"[Now] there's kind of an opening between the bulk of sea ice and the coast of Ellesmere. Last week that wasn't there."
Warwick Vincent, director of Laval University's Centre for Northern Studies, has had students monitoring conditions on the ice shelf for years.
He called the ice break "a significant event" that the shelf has been building toward since it began gradually thinning during the 1950s. Since then, over a 40-year period, the shelf thinned from 70 metres in the early 1950s to about 35 metres in the 1990s, Dr. Vincent said.