Go to Google News

Big chunk of Antarctic ice shelf falling apart

4 hours ago

WASHINGTON (AFP) — Antarctica's massive Wilkins Ice Shelf has begun
disintegrating under the effects of global warming, satellite images by the
University of Colorado's National Snow and Ice Data Center showed.

The collapse of a substantial section of the shelf was triggered February 28
when an iceberg measuring 41 by 2.4 kilometers (25.5 by 1.5 miles) broke off its
southwestern front.

That movement led to disintegration of the shelf's interior, of which 414
square kilometers (160 square miles) have already disappeared, scientists
say.

The Wilkins Ice Shelf is a broad plate of permanent floating ice 1,609
kilometers (1,000 miles) south of South America, on the southwest Antarctic
Peninsula.

Now, as a result of recent losses, a large part of the
12,950-square-kilometer (5,000-square-mile) shelf is supported by a narrow
5.6-kilometer (3.5-mile) strip of ice between two islands, scientists said.

"If there is a little bit more retreat, this last 'ice buttress' could
collapse and we'd likely lose about half the total ice shelf area in the next
few years," NSIDC lead scientist Ted Scambos said in a statement.

"Wilkins is the largest ice shelf on West Antarctica yet to be threatened.
This shelf is hanging by a thread," echoed David Vaughan of the British
Antarctic Survey, which contributed data on the break-up.

Jim Elliott, who was onboard a British Antarctic Survey Twin Otter aircraft
sent to video the extent of the damage, said the scene looked like a bomb
site.

"I've never seen anything like this before -- it was awesome," he said in a
BAS statement.

"We flew along the main crack and observed the sheer scale of movement from
the breakage.

"Big hefty chunks of ice, the size of small houses, look as though they've
been thrown around like rubble -- it's like an explosion."

Antarctica has suffered unprecedented warming in the last 50 years -- with
several ice shelves retreating and six of them collapsing since the 1970s.

"Climate warming in the Antarctic Peninsula has pushed the limit of viability
for ice shelves further south, setting some of them that used to be stable on a
course of retreat and eventual loss," Vaughan said.

Vaughan said the Wilkins breakout would not affect sea levels because it was
already floating when it broke off.

"But it is another indication of the impact that climate change is having on
the region."

Over the past half century, the western Antarctic Peninsula has experienced
the steepest temperature increase on Earth, 0.5 degrees Celsius (0.9 Farenheit)
per decade.

"We believe the Wilkins has been in place for at least a few hundred years,
but warm air and exposure to ocean waves are causing a breakup," said Scambos,
who first spotted the disintegration in March.

With the Antarctic summer drawing to a close, scientists do not expect the
ice shelf to further disintegrate in the next several months.

"This unusual show is over for this season," said Scambos. "But come January,
we'll be watching to see if the Wilkins continues to fall apart."

Ultimately, ice shelf breakup in the Antarctic -- more than 13,000 square
kilometers (5,000 square miles) have been lost over the past 50 years -- could
significantly increase ocean levels around the world.

In 1995 the Larsen A Ice Shelf -- 75 kilometers (47 miles) long and 35
kilometers (22 miles) wide -- disintegrated, fragmenting into icebergs in the
Weddell Sea.

In March 2002, a NASA satellite captured the collapse of Larsen B, which had
a surface area of 3,850 square kilometers (1,486 square miles), was 200 meters
(656 feet) high, and packed in 720 billion tonnes of ice. It took just 30 days
to break apart.

According to some calculations based on the present sea level rise of three
millimeters per year (0.11 inches), ocean levels could rise by 1.4 meters (4.6
feet) by the end of the century.

Hosted by

Copyright © 2008 AFP. All rights reserved. More »