Deshielo en el Ártico Canadiense

Fuente: MSNBC
Comentario: A pesar de que la fuente es un medio norteamericano de los "grandes", siempre emplear "calentamiento global", "cambio climático" etc

Ancient ice shelf breaks free in Canadian Arctic

Breakaway may 'signal the onset of accelerated change,' researchers say

TORONTO - A giant ice shelf has snapped free from an island south of the North Pole, scientists said Thursday, citing climate change as a “major” reason for the event.

The Ayles Ice Shelf — about the size of Manhattan — broke clear 16 months ago from the coast of Ellesmere Island, about 500 miles south of the North Pole in the Canadian Arctic.

Scientists discovered the event by using satellite imagery. Within one hour of breaking free, the shelf had formed as a new ice island, leaving a trail of icy boulders floating in its wake.

Warwick Vincent of Laval University, who studies Arctic conditions, traveled to the newly formed ice island and couldn’t believe what he saw.

“This is a dramatic and disturbing event. It shows that we are losing remarkable features of the Canadian North that have been in place for many thousands of years,” Vincent said. “We are crossing climate thresholds, and these may signal the onset of accelerated change ahead.”

The ice shelf was one of six major shelves remaining in Canada’s Arctic. They are packed with ancient ice that is more than 3,000 years old. They float on the sea but are connected to land.

'Consistent with climate change'
Some scientists say it is the largest event of its kind in Canada in nearly 30 years and that climate change was a major element.

“It is consistent with climate change,” Vincent said, adding that the remaining ice shelves are 90 percent smaller than when they were first discovered in 1906. “We aren’t able to connect all of the dots ... but unusually warm temperatures definitely played a major role.”

Laurie Weir, who monitors ice conditions for the Canadian Ice Service, was poring over satellite images in 2005 when she noticed that the shelf had split and separated.

Weir notified Luke Copland, head of the new global ice lab at the University of Ottawa, who initiated an effort to find out what happened.

Using U.S. and Canadian satellite images, as well as seismic data — the event registered on earthquake monitors 155 miles away — Copland discovered that the ice shelf collapsed in the early afternoon of Aug. 13, 2005.

Copland said the speed with which climate change has affected the ice shelves has surprised scientists.

“Even 10 years ago scientists assumed that when global warming changes occur that it would happen gradually so that perhaps we expected these ice shelves just to melt away quite slowly,” he said.

Instead, satellite images showed the 9-mile long crack, then the ice floating about a half mile from the coast within about an hour, Copland said.

“You could stand at one edge and not see the other side, and for something that large to move that quickly is quite amazing,” he said.

Copland said the break was likely due to a combination of low accumulations of sea ice around the mass’s edges as high winds blew it away, as well as one of the Arctic's warmest temperatures on record. The region was 5.4 degrees F above average in the summer of 2005, he said.

Ice shelves in Canada’s far north have decreased in size by as much as 90 percent since 1906, and global warming likely played a role in the Ayles break, Copland said.

“It’s hard to tie one event to climate change, but when you look at the longer-term trend, the bigger picture, we’ve lost a lot of ice shelves on northern Ellesmere in the past century and this is that continuing,” he said. “And this is the biggest one in the last 25 years.”