Some 220 square miles of ice has collapsed in Antarctica and an ice shelf about seven times the size of Manhattan is "hanging by a thread," the British Antarctic Survey said Tuesday, blaming global warming.
"We are in for a lot more events like this," said professor Ted Scambos, a glaciologist at the National Snow and
Scambos alerted the British Antarctic Survey after he noticed part of the Wilkins ice shelf disintegrating on February 28, when he was looking at NASA satellite images.
Late February marks the end of summer at the South Pole and is the time when such events are most likely, he said.
"The amazing thing was, we saw it within hours of it beginning, in between the morning and the afternoon pictures of that day," Scambos said of the large chunk that broke away on February 28.
The Wilkins ice shelf lost about 6 percent of its surface a decade ago, the British Antarctic Survey said in a statement on its Web site
Another 220 square miles -- including the chunk that Scambos spotted -- had splintered from the ice shelf as of March 8, the group said.
"As of mid-March, only a narrow strip of shelf ice was protecting several thousand kilometers of potential further breakup," the group said.
Scambos' center put the size of the threatened shelf at about 5,282 square miles, comparable to the state of
Once Scambos called the British Antarctic Survey, the group sent an aircraft on a reconnaissance mission to examine the extent of the breakout.
"We flew along the main crack and observed the sheer scale of movement from the breakage," said Jim Elliott, according to the group's Web site.
"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," he said.
"Wilkins is the largest ice shelf on the
"I didn't expect to see things happen this quickly. The ice shelf is hanging by a thread -- we'll know in the next few days or weeks what its fate will be."
Ice shelves are floating ice sheets attached to the coast. Because they are already floating, their collapse does not have any effect on sea levels, according to the Cambridge-based British Antarctic Survey.
Scambos said the ice shelf is not currently on the path of the increasingly popular tourist ships that travel from South America to
"Wildlife will be impacted, but they are pretty adept at dealing with a topsy-turvy world," he said. "The ecosystem is pretty resilient."
Several ice shelves -- Prince Gustav Channel, Larsen Inlet, Larsen A, Larsen B, Wordie, Muller and Jones -- have collapsed in the past three decades, the British Antarctic Survey said.
Larsen B, a 1,254-square-mile ice shelf, comparable in size to the
Scientists say the western Antarctic peninsula -- the piece of the continent that stretches toward
Scambos said the poles will be the leading edge of what's happening in the rest of the world as global warming continues.
"Even though they seem far away, changes in the polar regions could have an impact on both hemispheres, with sea level rise and changes in climate patterns," he said.
News of the Wilkins ice shelf's impending breakup came less than two weeks after the United Nations Environment Program reported that the world's glaciers are melting away and that they show "record" losses.
"Data from close to 30 reference glaciers in nine mountain ranges indicate that between the years 2004-2005 and 2005-2006 the average rate of melting and thinning more than doubled," the UNEP said March 16.
The most severe glacial shrinking occurred in Europe, with
The Associated Press, March 25, 2008
A chunk of Antarctic ice about seven times the size of
Satellite images show the runaway disintegration of a 160-square-mile chunk in western
This is the result of global warming said British Antarctic Survey scientist David Vaughan.
Because scientists noticed satellite images within hours, they diverted satellite cameras and even flew an airplane over the ongoing collapse for rare pictures and video.
"It's an event we don't get to see very often," said Ted Scambos, lead scientist at the National Snow and Ice Data Center in Boulder, Colo. "The cracks fill with water and slice off and topple... That gets to be a runaway situation."
While icebergs naturally break away from the mainland, collapses like this are unusual but are happening more frequently in recent decades,
The rest of the Wilkins ice shelf, which is about the size of
Scientists said they are not concerned about a rise in sea level from the latest event, but say it's a sign of worsening global warming.
Such occurrences are "more indicative of a tipping point or trigger in the climate system," said Sarah Das, a scientist at the Woods Hole Oceanographic Institute.
Planetark.org, March 26, 2008
The area of collapse measured about 160 square miles (415 square km) of the Wilkins Ice Shelf, according to satellite imagery from the
The Wilkins Ice Shelf is a broad sheet of permanent floating ice that spans about 5,000 square miles (13,000 square km) and is located on the southwest Antarctic Peninsula about 1,000 miles (1,600 km) south of South America.
"Block after block of ice is just tumbling and crumbling into the ocean," Ted Scambos, lead scientist at the National Snow and Ice Data Centre, said in a telephone interview.
"The shelf is not just cracking off and a piece goes drifting away, but totally shattering. These kinds of events, we don't see them very often. But we want to understand them better because these are the things that lead to a complete loss of the ice shelf," Scambos added.
Scambos said a large part of the ice shelf is now supported by only a thin strip of ice. This last "ice buttress" could collapse and about half the total ice shelf area could be lost in the next few years, Scambos added.
British Antarctic Survey scientist David Vaughan said in a statement: "This shelf is hanging by a thread."
"One corner of it that's exposed to the ocean is shattering in a pattern that we've seen in a few places over the past 10 or 15 years. In every case, we've eventually concluded that it's a result of climate warming," Scambos added.
Satellite images showing the collapse began on Feb. 28, as a large iceberg measuring 25.5 by 1.5 miles (41 km by 2.4 km) fell away from the ice shelf's south-western front leading to a runaway disintegration of the shelf interior, Scambos said.
A plane also was sent over the area to get photographs of the shelf as it was disintegrating, he added.
Scambos said this ice shelf has been in place for at least a few hundred years, but warm air and exposure to ocean waves are causing a breakup. In the past half century, the
"The warming that's going on in the peninsula is pretty clearly tied to greenhouse gas increases and the change that they have in the atmospheric circulation around the Antarctic," Scambos said.