Ice shelf hangs by a thread

A large part of the Wilkins Ice Shelf on the Antarctic Peninsula is now supported only by a thin strip of ice hanging between two islands and still on the move. It is another identifiable impact of climate change on the Antarctic environment.

The Wilkins Ice Shelf is a broad plate of permanent floating ice on the southwest Antarctic Peninsula, about 1,000 miles south of South America. In the past 50 years, the western Antarctic Peninsula has experienced the biggest temperature increase on Earth, rising by 0.5 degree Celsius (0.9 degree Fahrenheit) per decade.

"Wilkins is the largest ice shelf on the Antarctic Peninsula yet to be threatened. 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." Professor Professor David Vaughan at the British Antarctic Survey (BAS) said.

In 1993 he predicted that the northern part of Wilkins Ice Shelf was likely to be lost within 30 years if climate warming on the Peninsula were to continue at the same rate.

Unprecedented warming
"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 break-up." Glaciologist Ted Scambos from the University of Colorado, said.

Scambos first spotted the disintegration in March. He alerted colleagues Professor David Vaughan and Andrew Fleming of the British Antarctic Survey (BAS) that the ice shelf looked at risk. After checking daily satellite pictures, BAS sent a Twin Otter aircraft on a reconnaissance mission to check out the extent of the breakout.

Foto: British Antarctic Survey
Wilkins Ice Shelf from BAS Twin Otter.

"I've never seen anything like this before - it was awesome. 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."  Jim Elliott said. He was onboard the BAS Twin Otter to capture video of the breakout for Vaughan and colleagues.

Foto: British Antarctic Survey
Location map showing Wilkins Ice Shelf on the Antarctic PeninsulaBegan in February
Satellite images indicate that the Wilkins began its collapse on February 28. Data revealed that a large iceberg, 41 by 2.5 kilometers (25.5 by 1.5 miles), fell away from the ice shelf's south-western front, triggering a runaway disintegration of 405 square kilometers (160 square miles) of the shelf interior.

In a series of images, the edge of the shelf proceeded to crumble and disintegrate in a pattern that has become characteristic of climate-caused ice shelf retreats throughout the northern Peninsula, leaving a sky-blue patch spreading across the ocean surface compose of hundreds of large blocks of exposed old glacier ice.

By 8 March, the ice shelf had lost just over 570 km2, and the patch of disintegrated Antarctic ice had spread over 1400km2.

On March 23. A narrow beam of intact ice, just 6 kilometers wide (3.7 miles) was protecting the remaining shelf from further breakup.

Latest drama
Scientists track ice shelves and study collapses carefully because some of them hold back glaciers, which if unleashed, can accelerate and raise sea level.

The breakout is the latest drama in a region of Antarctica that has experienced unprecedented warming over the last 50 years.

Several ice shelves have retreated in the past 30 years - six of them collapsing completely Prince Gustav Channel, Larsen Inlet, Larsen A, Larsen B, Wordie, Muller and the Jones Ice Shelf.

The Larsen B became the most well-known of these, disappearing in just over thirty days in 2002.

Rapid Climate change
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. The Wilkins breakout won't have any effect on sea-level because it is floating already, but it is another indication of the impact that climate change is having on the region." Proafessor Ted Scambos Colorado said

The Antarctic Peninsula is an area of rapid climate change and has warmed faster than anywhere else in the Southern Hemisphere over the past half century. Climate records from the west coast of the Antarctic Peninsula show that temperatures in this region have risen by nearly 3°C during the last 50 years - several times the global average and only matched in Alaska.

Foto: British Antarctic Survey
Satellite image of Wilkins Ice Shelf - Satellite image showing the thread by which Wilkins Ice Shelf hangs. The red line indicates the position of ice edge in 2007. Just visible is the 'thread'
IPY- satelite
Regular satellite images of Wilkins Ice Shelf were obtained using NASA's Modis instruments and the International Polar Year ‘Polar View' project which uses the European Space Agency Envisat satellite. Polar View operates to provide timely images of the Antarctic sea ice and shelves to assist science and operations in the Southern Ocean.

Further information and images are available at http://www.polarview.aq/

This discovery follows the recent UNEP report that the world's glaciers are continuing to melt away. Data from 30 reference glaciers in nine mountain ranges show that between the years 2004-2005 and 2005-2006 the average rate of melting and thinning has more than doubled. 

Read more and see images at the British Antarctic Survey web page

Source: Press release from  British Antarctic Survey Press Office.