11 april 2009

Ice Loss Sparks New Climate Change Fears
By Fiona Harvey in Bonn

Financial Times, April 11 2009

Key Facts and Quotes:

3°C: Amount Antarctic peninsula has warmed in 50 years

7 metres: Amount sea level will rise if Greenland’s ice sheet melts

70 metres: Rise if both east and west Antarctic ice sheets melt

”What we’re seeing is very dramatic. It’s very worrying”, Andrew Fleming, British Antarctic Survey

”We have no time to lose in tackling this crisis”, Hillary Clinton, US secretary of state

Evidence of ice loss from both poles this week has sparked fresh fears that global warming is progressing faster than scientists had predicted.

Arctic ice has thinned dramatically, as well as shrinking in area, according to US research. Thin seasonal ice, which melts and refreezes each year, now makes up about 70 per cent of the Arctic winter ice, up from about 40 to 50 per cent in the 1980s and 1990s, leaving far less of the older, thicker ice that is harder to melt.

In the Antarctic, an ice bridge connecting an island to the Wilkins ice shelf – a sheet of ice about the size of Northern Ireland – shattered as scientists monitored it through satellite observations.
“What we’re seeing is very dramatic,” said Andrew Fleming, remote sensing manager at the British Antarctic Survey. “It’s very worrying.”

Scientists believed the effects were linked to the “very strong warming” at the poles, he said. The Antarctic peninsula has warmed by more than 3ºC in the past 50 years. “That’s a staggering rate of warming, and it’s still going up,” said Mr Fleming.

Ice shelves take centuries to form, but when they start to break up it can be sudden. The bridge at the Wilkins ice shelf was a 40km strand of ice, at its narrowest point a few hundred metres wide, connecting the shelf to Charcot and Latady islands.

Last year, scientists from the BAS landed on it in an aircraft to examine the ice. They had known for some time it was under strain, but it remained intact until at the end of last week satellite images showed new cracks appearing.

The next day, the ice sheet had “exploded from the centre outwards”, said Mr Fleming, who was monitoring the break-up through satellite images from the European Space Agency.

“It was very fast, very dramatic,” he said. “It’s now completely shattered.”

The break-up of the ice bridge alarms scientists because it could accelerate the break-up of the rest of the Wilkins shelf. This was at least the 10th shelf to start disintegrating quickly in recent years, said Mr Fleming, and several more were in danger.

Rapid melting of polar sea ice is of particular concern for two reasons: disappearing ice leaves areas of open sea that are dark, and – unlike the reflective ice – absorb the sun’s heat, accelerating the warming process; the break-up of ice shelves exposes glaciers that then begin to move faster to the sea.

The Arctic and some of the Antarctic float on the sea. Ice takes up more space than water, and when this floating ice melts, it does not directly raise sea levels, in the same way that the melting of ice cubes in a full glass of water would not cause the glass to overflow.

However, the glaciers of the Antarctic peninsula are on land, so when they tumble into the sea, they contribute directly to rising sea levels. In the north, the Greenland ice sheet is also on land, and its glaciers are flowing faster to the sea.

If Greenland’s ice sheet melted, it would raise sea levels by seven metres, and if both the east and west Antarctic ice sheets went, the figure would be 10 times higher.

That would take hundreds of years, according to the Intergovernmental Panel on Climate Change.

Long before the land ice disappeared, however, sea levels would rise significantly – a 1 per cent loss of the Antarctic land ice would probably raise levels by 65cm, estimates the Norwegian Polar Institute.

Two conferences this week were addressing the problems of the poles and climate change....

[See also The Montreal Gazette of 4 April for a comparable article on Arctic ice melt: "The Climate Clock is ticking"

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