Antarctica: she's breaking up
View of the broken ice shelf (Pic: National Snow & Ice Data Center)
A huge section of the ice shelf in the Antarctic Peninsula has disintegrated, in the most dramatic such event over the past 30 years.
The collapse of the northern section of the Larsen B ice shelf was observed by satellite, and analysed at the US National Snow & Ice Data Center in Boulder, Colorado.
The ice mass has shattered and separated from the continent, forming a plume of thousands of icebergs adrift in the Weddell Sea.
"It's quite dramatic," said Mr Neal Young, a glaciologist at the Australian Antarctic Cooperative Research Centre in Hobart.
"Most of the break-up occurred over a period of two weeks."
Only once before has a large part of an ice shelf broken up and moved away — the Larsen A ice shelf in January 1995.
The Larsen B break-up is more than twice the size. About 3,250 square kilometres disintegrated over a 35-day period, releasing 720 billion tons of ice.
A total of 5,700 square kilometres has been lost, leaving the Peninsula 40 per cent smaller than it was five years ago.
Researchers observed a large amount of water on the ice surface on January 31, the result of a particularly warm summer in the Antarctic Peninsula.
They believe the meltwater helped to fracture the shelf by flowing into small cracks and forcing them open.
The part of the ice shelf that disintegrated was almost exactly the same region that was covered by melt ponds in late January.
"It's an indicator of what might happen if there is significant warming around the coastal regions of Antarctica," warned Mr Young.
The Antarctic Peninsula is warming more quickly than anywhere else in Antarctica. Temperature readings from research stations have shown an increase of two-and-a-half degrees or more over the past 60 years, he explained.
For the first time in many years, he added, the sea where the ice shelf broke up contains little or no sea ice.
If warmer summers continue over time, other ice shelves around the Antarctic coastline may also break up, Mr Young believes.
Studying such events will help researchers predict their effects on sea level, and to work out whether they are an indicator of long-term climate change.
However, ice separating from the ice shelf is not unusual in itself, said Mr Young.
"There has been carving of icebergs from ice shelves for eternity."
Ice shelves are thick plates of ice, fed by glaciers, that float on the ocean around much of Antarctica.
As it was already floating, the disintegration of Larsen will have no impact on sea level. According to the British Antarctic Survey, sea level will rise only if ice held on the continent, previously held back by an ice shelf, flows more quickly into the sea.
