Antarctica is melting more than twice as fast as in 2012

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From 2012 to 2017, the melting Antarctic ice sheet has dumped 241 billion tons of water into the ocean, the study says.

"The general consensus in glaciology was that ice sheets couldn't change rapidly - but that's not the case", Shepherd said.

Millimeters of sea level rise may not sound like much, but previous surveys suggested that Antarctica's massive ice sheets likely wouldn't be affected by climate change at all.

West Antarctica lost 159 billion tons of ice a year from 2012 through 2017, compared with just 65 billion tons from 2002 through 2007.

West Antarctica contributed the most ice loss from the continent, shedding almost 160 billion tonnes each year since 2012.

Before 2010, Antarctica was contributing a relatively small proportion of the melting that is causing global sea levels to rise, says study co-leader Andrew Shepherd of the University of Leeds.

Benjamin Smith, senior principal investigator at the University of Washington Applied Physics Laboratory, said climate scientists are getting a better handle on crucial questions relating to the impact of Antarctic melting, thanks to more advanced satellites.

Up to now, scientists have struggled in determining whether Antarctica has accumulated more mass through snowfall than it loses in meltwater run-off and ice flows into the ocean.

"We can not count on East Antarctica to be the quiet player, and we start to observe change there in some sectors that have potential, and they're vulnerable", co-author Isabella Velicogna, a researcher from University of California, told told the Post.

"According to our analysis, there has been a step increase in ice losses from Antarctica during the past decade, and the continent is causing sea levels to rise faster today than at any time in the past 25 years. And the ice sheet is now losing three times as much ice", Shepherd adds.

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"If we aren't already alert to the dangers posed by climate change, this should be an enormous wake-up call", said Martin Siegert, of the Grantham Institute at Imperial College London, and one of the authors.

More than 70 percent of the recent melt is in West Antarctica.

Between 60 and 90 percent of the world's fresh water is located in Antarctica - the size of Mexico and the United States combined - and if that were to all melt, sea levels would shoot up by nearly 61 metres, which would prove catastrophic for billions of people around the world.

"We depend upon the satellite measurements to not only tell us how the ice sheets respond but also to make these calculations to sea-level contribution", Shepherd said. "If this kind of thing happens more in the future we have to be aware of that". In the Antarctic Peninsula, the collapse of the Larsen B and Wilkins ice shelves in the 2000s has had similar consequences: an abrupt acceleration in the rate local glaciers drain into the ocean.

"Global sea level has risen by about 8 inches since reliable record keeping began in 1880".

"This does not mean that at current atmospheric carbon dioxide levels Antarctica won't contribute to sea level rise".

That's because as Antarctica's mass shrinks, the ice sheet's gravitational pull on the ocean relaxes somewhat, and the seas travel back across the globe to pile up far away - with US coasts being one prime destination.

Those signs help researchers to gauge the pace of ice retreat in Antarctica - estimated in the past to be about 164 feet (50 meters) each year - between glacial cycles, Shepherd said.

Andrew Shepherd of the University of Leeds, who leads the Ice sheet Mass Balance Inter-comparison Exercise (Imbie), said it had always been suspecting changes in Earth's climate would affect the polar ice sheets.