Greenland glacier sheds billions of tonnes of ice into ocean

A glacier in northeast Greenlandwith enough ice to raise world ocean levels by 50 cms (20inches) has begun to slide faster toward the sea, extending icelosses to all corners of the vast remote island, a study showedon Thursday.

Warmer water temperatures meant the end of the ZachariaeIsstrom glacier floated free from a ridge of bedrock below sealevel on which it had rested until 2012, according to the U.S.study reported in the journal Science.

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Without that natural brake, the glacier in the cold northwas now sliding quicker and more icebergs were snapping off,
adding a net five billion tonnes of ice a year to the oceans,according to the study based on satellite and aerial surveys.

"Similar changes even larger are under way in thesouth," Jeremie Mouginot, lead author of the study at the
University of California, Irvine (UCI), told Reuters in ane-mail.

Greenland contains enough ice to raise world sea levels byabout sixmetres (20 feet) if it ever all melted in a slow-motioncollapse that could take thousands of years.

Its ice losses, along with thawing ice from the Alps toAntarctica, have raised sea levels by about 20 centimetressince 1900.That aggravates storm surges for cities from New York toShanghai and threatens low-lying tropical island nations.

• Sea level has climbed 8 centimetressince 1992

A nearby north Greenland glacier, Nioghalvfjerdsfjorden often called "79" for ease of pronunciation was also meltingfast, the study said. But its slide was restricted by an uphillsection of seabed under its icy base.

'Staggering' changes

"The changes are staggering and are now affecting the fourcorners of Greenland," Eric Rignot, a co-author at UCI, said ina statement.

Almost 200 nations will meet in Paris for a summit startingon Nov. 30 to try to limit climate change.

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The U.N. panel ofclimate scientists estimates that sea levels may rise by between26 and 82 centimetres(10 and 32 inches) this century.

Ruth Mottram of the Danish Meteorological Institute, who wasnot involved in Thursday's study, said Greenland's glacierssometimes accelerate after small changes in the environment.

"A small retreat can become a much bigger retreat becausethese glaciers are only stable when they are resting on
bedrock," she said.

Another study has estimated Greenland lost a net 211 billiontonnes of ice annually from 2000-11 roughly 0.6 millimetres ofglobal sea level rise a year with icebergs and melting iceexceeding snowfall that replenishes the ice sheet.