[R-G] Huge chunk snaps off storied Arctic ice shelf - Globe & Mail

tchilds at resist.ca tchilds at resist.ca
Thu Jul 31 16:59:21 MDT 2008


http://www.theglobeandmail.com/servlet/story/RTGAM.20080729.wice29/BNStory/National/home

Huge chunk snaps off storied Arctic ice shelf
Break marks latest in erosion that has whittled 9,000 square kilometres
down to 1,000 over past century
 Article   Comments (856)
JESSICA LEEDER
>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.


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DAAC study: Breakup of the Ward Hunt Ice Shelf

"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.

In 2002, when his then-student Dr. Mueller discovered that the shelf had
cracked in two, continuing changes to the structural integrity of the
shelf seemed inevitable.

"Over the last five years or so, there's been an acceleration of change in
this area," Dr. Vincent said.

"We see this in a variety of indicators, including ... a gradual increase
in air temperatures in this area. Each year it seems we're crossing a new
threshold of environmental change in this area of the world."

Dr. Vincent said it's important to note that the Ward Hunt ice break is
"small compared to what we've seen in the past."

Indeed, the largest ice break recorded in recent time was significantly
larger: In 2005, the Ayles Ice Shelf, one of six in existence in Canada at
the time, broke off in its entirety, rendering a 66-square-kilometre ice
island that floated out to sea.

Still, the latest break "indicates ongoing change in this very sensitive
area," Dr. Vincent said.

Dr. Mueller, whom Dr. Vincent calls the pre-eminent expert on Ward Hunt
Ice Shelf, says he's concerned that the ice shelves will disappear
completely.

"The take-home message for me is that these ice shelves are not
regenerating," he said. "If we're looking at an indicator of whether
climate is to blame, it's really the lack of regeneration that convinces
me. They're breaking away so rapidly that there's no hope of
regeneration," he said, adding that is "pretty strong evidence that
suggests this is related to global warming."

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