Giant iceberg breaks off Antarctica

A section of an iceberg – about 6,000 sq km – broke away as part of the natural cycle of iceberg calving off the Larsen-C ice shelf in Antarctica in this satellite image released by the European Space Agency on July 12, 2017. Courtesy ESA/Handout via REUTERS ATTENTION EDITORS - THIS IMAGE WAS PROVIDED BY A THIRD PARTY.

(This July 12 story corrects name of vessel in eighth paragraph and year it sank)

LONDON (Reuters) - One of the biggest icebergs on record has broken away from Antarctica, scientists said on Wednesday, creating an extra hazard for ships around the continent as it breaks up.

An aerial view of the rift in the Larsen C seen in an image from the Digital Mapping System over the Antarctica Peninsula, Antarctica, on November 10, 2016. NASA's Goddard Space Flight Center/Handout via REUTERS/File Photo

The one trillion ton iceberg, measuring 5,800 square km, calved away from the Larsen C Ice Shelf in Antarctica sometime between July 10 and 12, said scientists at the University of Swansea and the British Antarctic Survey.

The iceberg, which is roughly the size of the U.S. state of Delaware or the Indonesian island of Bali, has been close to breaking off for a few months.

Throughout the Antarctic winter, scientists monitored the progress of the rift in the ice shelf using the European Space Agency satellites. 

The one trillion tonne iceberg, measuring 5,800 square km, calved away from the Larsen C Ice Shelf in Antarctica, in an image taken July 12, 2017. REUTERS/via European Space Agency

"The iceberg is one of the largest recorded and its future progress is difficult to predict," said Adrian Luckman, professor at Swansea University and lead investigator of Project MIDAS, which has been monitoring the ice shelf for years.

"It may remain in one piece but is more likely to break into fragments. Some of the ice may remain in the area for decades, while parts of the iceberg may drift north into warmer waters," he added.

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.

A rift across the Larsen C Ice Shelf that had grown longer and deeper is seen during an airborne surveys of changes in polar ice over the Antarctic Peninsula from NASA’s DC-8 research aircraft on November 10, 2016. Courtesy NASA/Handout via REUTERS/File Photo

In 2007, more than 150 passengers and crew were evacuated after the MS Explorer sank after striking an iceberg off the Antarctic peninsula.

The iceberg, which is likely to be named A68, was already floating before it broke away so there is no immediate impact on sea levels, but the calving has left the Larsen C ice shelf reduced in area by more than 12 percent.

The Larsen A and B ice shelves, which were situated further north on the Antarctic Peninsula, collapsed in 1995 and 2002, respectively.

A satellite view of Antarctica. REUTERS/NASA/via Reuters

"This 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 manmade 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."

For a graphic, click http://fingfx.thomsonreuters.com/gfx/rngs/ANTARCTICA-LARSEN/010041GT36Y/ANTARCTICA-LARSEN-RIFT.jpg

(Editing by Toby Chopra)