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 part of the peninsula has experienced the biggest temperature increase on Earth, rising by 0.5 degree Celsius (0.9 degree Fahrenheit) per decade.
The collapse of the 26 square mile ice shelf was discovered in late February when satellite imagery attracted the attention of Ted Scambos, lead scientist at the National Snow and Ice Data Center at the University of Colorado-Boulder. Scambos first spotted the disintegration, which began on February 28.
"We believe the Wilkins has been in place for at least a few hundred years," said Scambos. "But warm air and exposure to ocean waves are causing a break-up."
Scambos alerted colleagues around the world, seeking to ensure that every means of gathering information was focused on the collapsing ice shelf.
On the western Antarctic Peninsula, the Wilkins Ice Shelf is disintegrating. (Photo by Jim Elliott courtesy British Antarctic Survey)
The British Antarctic Survey conducted an overflight of the crumbling shelf, collecting video footage and other observations. BAS glaciologist David Vaughan said the ice shelf is supported by a single strip of ice strung between two islands.
Vaughan, who in 1993 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, said, "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," Vaughan said. "We'll know in the next few days or weeks what its fate will be."
Jim Elliott was onboard the BAS Twin Otter to capture video of the breakup. "I've never seen anything like this before - it was awesome," he said. "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."
Scientists track ice shelves and study collapses carefully because some of them hold back glaciers, which if released, can accelerate and raise sea level.
"The Wilkins disintegration won't raise sea level because it already floats in the ocean, and few glaciers flow into it," Scambos said. "However, the collapse underscores that the Wilkins region has experienced an intense melt season. Regional sea ice has all but vanished, leaving the ice shelf exposed to the action of waves."
Scientist Cheng-Chien Liu at Taiwan's National Cheng-Kung University analyzed high-resolution color satellite images of the area from Taiwan's Formosat-2 satellite.
Liu said, "It looks as if something is slicing the ice shelf piece by piece on an incredible scale, kilometers long but only a few hundred meters in width."
Chilean scientists also got involved. Andres Rivera and Gino Cassasa at the Laboratorio de Glaciología y Cambio Climático at the Centro de Estudios Científicos are studying images of the Wilkins from the ASTER instrument, aboard NASA's Terra satellite.
The Wilkins Ice Shelf is breaking up. (Photo by Jim Elliott courtesy British Antarctic Survey)
The combined efforts of these international teams have begun to provide observational data that will improve scientific understanding of the mechanisms behind ice shelf collapse.
Scambos said, "The Wilkins is an example of an event we don't see very often. But it's a key process in being able to predict how sea level will change in the future."
Climate warming has increased the volume of summer meltwater on glaciers, which has weakened ice shelves, the scientists say. Sea ice, which protects ice shelves from ocean swell, has reduced also as a result of warming temperatures.
The Wilkins Ice Shelf began retreating in the 1990s. A major breakout occurred in 1998 when 1,000 square kilometers of ice was lost in a few months.
The Wilkins is one of a string of ice shelves that have collapsed in the West Antarctic Peninsula in the past 30 years. The Larsen B became the best known of these, disappearing in just one month in 2002.
The Prince Gustav Channel, Larsen Inlet, Larsen A, Wordie, Muller, and the Jones Ice Shelf collapses also underscore the unprecedented warming in this region of Antarctica.
Professor Vaughan of the British Antarctic Survey said, "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."
Copyright Environment News Service (ENS) 2008. All rights reserved.