One trillion tonne iceberg breaks off from Antarctica
A one trillion tonne iceberg has broken off from an Antarctic ice shelf, changing the shape of the Antarctic Peninsula forever.
The much-anticipated calving from the Larsen C Ice Shelf reduces its area by more than 12 per cent, though the 5800 square km iceberg won't have an impact on sea levels as it was already floating before completely breaking away.
Researchers have previously shown the rift could increase the risk of instability leading to the wider ice shelf's collapse - a fate which befell its neighbour Larsen B, seven years after it experienced its own calving event in 1995.
Believed to size up among the top ten on record (it is roughly 6000sqkm, six times the size of Auckland city), the iceberg separated from Larsen C sometime between July 10 and July 12 - the event detected and confirmed separately by two Nasa satellites.
* Antarctic crack widening quicker than expected, may release giant iceberg
* Nasa snaps photos of a new crack in one of Greenland's largest glaciers
* Mass human presence in Antarctica unsustainable, new options explored
Project MIDAS, a UK-based Antarctic research project, has been following the progress of the rift in the Larsen C ice shelf, following the disintegration of Larsen A in 1995 and Larsen B in 2002.
Professor Adrian Luckman of Swansea University, lead investigator of the project, told its blog the calving event has been anticipated for months.
"The iceberg is one of the largest recorded and its future progress is difficult to predict. It may remain in one piece but is more likely to break into fragments," he said.
"Some of the ice may remain in the area for decades, while parts of the iceberg may drift north into warmer waters."
The ice will add to risks for ships now it has broken off. The peninsula is outside major trade routes but the main destination for cruise ships visiting from South America.
In 2009, more than 150 passengers and crew were evacuated after the MTV Explorer sank after striking an iceberg off the Antarctic peninsula.
The collapse of the Larsen A and B ice shelves "resulted in the dramatic acceleration of the glaciers behind them, with larger volumes of ice entering the ocean and contributing to sea-level rise," said David Vaughan, glaciologist and director of science at British Antarctic Survey.
"If Larsen C now starts to retreat significantly and eventually collapses, then we will see another contribution to sea level rise," he added.
Big icebergs break off Antarctica naturally, meaning scientists are not linking the rift to man-made climate change. The ice, however, is a part of the Antarctic peninsula that has warmed fast in recent decades.
"In the ensuing months and years, the ice shelf could either gradually regrow, or may suffer further calving events which may eventually lead to collapse - opinions in the scientific community are divided," Luckman said.
"Our models say it will be less stable, but any future collapse remains years or decades away."
- Sydney Morning Herald, Reuters