ENVIRONMENT-ANTARCTICA: Speed of Ice Shelf Collapse Shocked Experts

By Marcela Valente Reprint | | Print |

Marcela Valente

BUENOS AIRES, Mar 22 2002 (IPS) - Although it was expected to happen, Argentine researchers who study Antarctica were shocked at how fast the 3,200-square-kilometre Larsen B ice shelf broke off from the Antarctic continent.

“What really drew our attention was the speed with which the ice shelf collapsed,” Argentine geologist Hernán De Angelis told IPS. “The place where we had been camping in September, an area that had been ice for 12,000 years, was just ocean, with whales leaping around in it, by March.”

De Angelis and glaciologist Pedro Skcvarca, with the Argentine Antarctic Institute, pointed out that temperatures in the Antarctic peninsula, where the Larsen B ice shelf was located off the extreme southern tip of South America, were the highest in over a century during this southern hemisphere summer.

The ice shelf, which scientists had predicted would collapse, but not so fast, is now floating in the Weddell sea, broken up into thousands of icebergs.

However, the disintegration of ice shelves, which surround much of the Antarctic continent, does not raise sea level, because they are already floating on the water. Nevertheless, it leaves glaciers exposed to the action of the waves, which speeds up their erosion.

The researchers also reported changes in the flora and fauna on the Antarctic peninsula.

“We observed enormous growths of moss and animals never before seen there, like black neck swans and South American sea lions, as well as an increase in the populations of species that already lived in the area,” said De Angelis.

The experts showed IPS photos of lagoons and a 30-metre high waterfall dropping into the sea from the top of the iceshelf – a landscape they described as “incredible” and “never before seen” in that area.

Skcvarca could not believe what he had witnessed. “In just 41 days, 33 percent of a 12,000-year-old shelf was lost, and we saw it. That is a real privilege for a glaciologist,” he said.

In September, De Angelis and Skcvarca had already documented a drastic acceleration of the displacement and shrinking of the Larsen B ice shelf. But the disintegration picked up even more speed over the past month and a half.

Satellite images of the changes in the shape of the Antarctic continent have flown around the world this week. But De Angelis and Skcvarca provided personal testimony of the time they had spent on the Larson B ice shelf, and they have also flown over the area at just 100 metres altitude taking photographs and gauging the changes.

“In September we had noted anomalous phenomena. The speed at which the shelf was moving went from one metre a day – the average over the last 12,000 years – to 1.3 metres. An 800-square- kilometre area had collapsed, and the temperature was the highest, on average, in nearly a century,” De Angelis explained.

“The acceleration was a clear sign that the shelf would disintegrate,” he added. When the temperature rises, water creates bigger and bigger cracks and crevasses in ice shelves, eventually destroying them, said De Angelis.

The changes they observed led the two researchers to return to the Antarctic in February, where they stayed until this month. But bad weather kept them from flying over the area when the collapse actually occurred.

Once they were able to take off in the plane, they found a “bleak” landscape, said De Angelis. “Where a 230-metre high ice shelf stood before, there was now open sea,” he added. The researchers said the area that collapsed was roughly 16 times the size of the city of Buenos Aires.

“The barrier had broken to pieces. The collapse was dramatic,” said Skcvarca, who has worked on the vast, practically uninhabited frozen continent on and off for 20 years.

Ice shelves need highly stable conditions, explained the researchers, who agree with scientists around the world that the break-up of the enormous Larsen B shelf, which altered the map of the coastline of the Antarctic peninsula, was a sign that drastic changes lay ahead.

“In the last flight we took this month, we saw that the shelf had actually disappeared along an at least 200-km stretch of coastline. The glaciers and exposed rock can be seen, and are now directly washed by the Weddell sea,” said Skcvarca.

Although they underlined that they are not climatologists, the researchers joined scientists around the globe in warning that the phenomenon is probably linked to global warming, caused by the greenhouse effect, which is blamed by the scientific community on the release of carbon dioxide into the atmosphere by the burning of fossil fuels.

They noted that Antarctic ice core at least 500,000 years old has shown that the content of carbon dioxide in the atmosphere has risen by 30 percent over the past two centuries, with an especially large increase in the second half of the 20th century, due to the growing automobile industry.

However, they stressed that the change in temperature that led to the collapse of the Larsen B ice shelf was regional in nature, and did not even affect the rest of Antarctica – a continent of 13 million square kilometres – where average temperatures remained stable and were even gradually dropping.

But at the Argentine air force’s Marambio base on the Antarctic peninsula, “there were days when the temperature rose to as high as 12 degrees Celsius” said De Angelis, who was surprised at being able to work outside in shirtsleeves.

“If a two degree rise in temperature was seen at a global level, it would be absolutely catastrophic. It would affect the entire world, and there would be no glaciers left,” Skcvarca underscored.