A one trillion tonne iceberg has broken off from an Antarctic ice shelf, changing the shape of the Antarctic Peninsula.
The much-anticipated calving from the Larsen C Ice Shelf reduces its area by more than 12 per cent, though the 5800 square kilometre iceberg won't have an impact on sea levels as it was already floating before breaking away completely.
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Trillion-tonne iceberg breaks off Antarctica
As big as Bali, the loss of the Larsen C ice shelf will require maps to be redrawn and could ultimately cause sea levels to rise.
But it will require the map of the Antarctic to be redrawn.
Researchers have previously shown the rift could increase the risk of instability of the wider ice shelf, leading to its collapse - a fate that befell its neighbour Larsen A, seven years after it experienced its own calving event in 1995.
The iceberg, which is likely to be named A68, is believed to be among the 10 biggest on record, roughly the size of Bali.
It separated from Larsen C between July 10 and July 12, an event detected and confirmed separately by two NASA satellites.
Project MIDAS, a British-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 the MIDAS blog the calving event had been anticipated for months.
![The lump of ice that broke has spawned one of the largest icebergs on record and changed the outline of the Antarctic ...](http://web.archive.org./web/20170714172915im_/https://www.fairfaxstatic.com.au/content/dam/images/g/x/a/5/8/f/image.related.articleLeadwide.620x349.gxa273.png/1499908936483.jpg)
"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.
![Scientists from NASAâs Operation IceBridge measured the iceberg that broke off from Larsen C at 130 kilometres long, ...](http://web.archive.org./web/20170714172915im_/https://www.fairfaxstatic.com.au/content/dam/images/g/x/5/u/h/l/image.related.articleLeadwide.620x349.gxa273.png/1499908936483.jpg)
"The remaining shelf will be at its smallest ever known size. This is a big change. Maps will need to be redrawn."
The iceberg will add to risks for ships now that it has broken off. The peninsula is outside major trade routes but is the main destination for cruise ships visiting from South America.
![The Larsen C ice shelf in Antarctica in February this year. It broke away this week, according to scientists.](http://web.archive.org./web/20170714172915im_/https://www.fairfaxstatic.com.au/content/dam/images/g/x/a/5/8/9/image.related.articleLeadwide.620x349.gxa273.png/1499925901065.jpg)
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 the British Antarctic Survey.
![This NASA photo on November 10 last year, shows a rift in the Antarctic Peninsula's Larsen C ice shelf.](http://web.archive.org./web/20170714172915im_/https://www.fairfaxstatic.com.au/content/dam/images/g/x/5/u/h/w/image.related.articleLeadwide.620x349.gxa273.png/1499908936483.jpg)
"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. However, the ice is a part of the Antarctic Peninsula that has warmed quickly in recent decades.
![Ice flow velocities of Larsen C in February this year, from ESA Sentinel-1 data.](http://web.archive.org./web/20170714172915im_/https://www.fairfaxstatic.com.au/content/dam/images/g/v/y/g/5/3/image.related.articleLeadNarrow.300x0.gxa273.png/1499908936483.jpg)
"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."
![graphic](http://web.archive.org./web/20170714172915im_/http://www.smh.com.au/cqstatic/12z7v7/1307iceberg729px.jpg)
With Reuters