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Antarctica's Ice Sheet Is Melting 3 Times Faster Than Before

14 June 2018

The findings should dispel any lingering doubts that the continent's ice mass is shrinking, the authors said.

While that won't happen overnight, Antarctica is indeed melting, and a study published Wednesday (June 13) in the journal Nature shows that the melting is speeding up.

This unthinkable vision can be avoided, but the researchers say the world's climate efforts in the next 10 years will be crucial to securing the mitigated benefits of a low emissions destiny - which would see Antarctica's ice shelves remain intact, only contributing about half a metre to sea level rise by 2070.

They also highlight the existential threat facing low-lying coastal cities and communities home to hundreds of millions of people.

Changes in global sea level, from 1992 to 2017, due to contributions from the Antarctic ice sheet.

"We view these results as another ringing alarm for action to slow the warming of our planet".

But more than two decades of satellite data - the new findings draw from 24 separate space-based surveys - have finally yielded a more complete picture.

For the total period from 1992 through the present, the ice sheet has lost almost 3 trillion tons of ice, equating to just under 8 millimeters of sea level rise.

"If you take a look at the first IPCC [Intergovernmental Panel on Climate Change] assessment report - 30 years ago, before we had satellite measurements of the polar regions - you'll see that the ice sheets were not expected to respond to climate change at all".

Some studies had suggested a net gain in mass over recent decades.

The high seas are getting even higher, and all that water is largely coming from a colossal Antarctic ice melt that has gotten much worse in recent years.

The melting is the result of warmer ocean waters undermining glaciers grounded on sea bottoms around Antarctica and increased surface melt from warmer air temperatures.

Almost all of the mass shed over the last quarter century has come from West Antarctica, the study found. Prior to 2012 the continent was losing ice at a rate of around 76 billion tonnes per year.

The researchers attribute the increased losses in West Antarctica and the Antarctic Peninsular to changes in regional floating-ice shelves, which can provide a buffer to continental-ice sheets. The study in Wednesday's journal Nature is part of an global effort to assess vulnerable ice sheets in Antarctica and Greenland, which are key indicators of climate change.

That's adding 0.6 of a millimetre to sea levels each year. Since 1993, the global ocean watermark has gone up by 84.8 mm (3.3 inches). According to the study, the rate of loss in that part of the content has increased from 53 billion tonnes per year in the 1990s, up to the current rate of 159 billion tonnes per year.

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. All that water made global oceans rise about three-tenths of an inch (7.6 millimeters).

Twila Moon, a research scientist at the National Snow and Ice Data Center who wasn't part of the studies, said "ice-speaking, the situation is dire".

She also said that in light of the study, it is "very clear that now is absolutely not the time to back away from the science infrastructure that allows us to have information, so the coastal communities can plan with the best available information about what's happening down in Antarctica".

Chris Rapley, a professor of climate science at University College London who was not involved in the study, wrote in a comment that he had suggested in 2005 that a "slumbering giant (of ice in Antarctica) seemed to be awakening".

"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", says Earth observation scientist Andrew Shepherd from the University of Leeds, UK.

Or alternatively, he continued, Antarctica could drive faster changes, ones that "begin to exceed what we're going to be able to cope with".

Antarctica's Ice Sheet Is Melting 3 Times Faster Than Before