Rising carbon emissions putting Antarctic ice sheet under threat

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In the "the longest-ever assessment" of Antarctica's ice mass, scientists are reporting a rapid increase in melting - a six-fold increase in yearly Antarctic ice mass loss between 1979 and 2017.

Understanding Antarctica and the delicate balance of ice melt draining into the Southern Ocean, and the replenishing snowfall over the continent's interior, is critically important when estimating how much seas will rise around the globe as a result of global warming. They found the ice loss to be accelerating dramatically - a key indicator of human-caused climate change.

They discovered that from 1979 to 1990, Antarctica lost about 40 billion tonnes (44 billion tons) of ice each year.

The pace of melting also increased from 1979 to 2017: Antarctica's ice melting pace was an average of 48 gigatons per year, per decade.

"As the Antarctic ice sheet continues to melt away, we expect multi-metre sea level rise from Antarctica in the coming centuries", study lead Eric Rignot, chair of Earth system science at the University of California, said.

Lead author Richard Levy, from GNS Science and Victoria University of Wellington, said the study showed the ice sheet was "highly sensitive" to changes in temperature.

The western edge of the famed iceberg A-68, calved from the Larsen C ice shelf, is seen from NASA's Operation IceBridge research aircraft, near the coast of the Antarctic Peninsula region, on October 31, 2017, above Antarctica.

The ice sheet is buffered by these warmer waters by sea-ice but as emissions continue to rise, that sea-ice is slowly disappearing, making the ice sheet more vulnerable to melting, Mr Levy said.

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The Associated Press Health & Science Department receives support from the Howard Hughes Medical Institute's Department of Science Education. If melted, the Antarctic ice will cause the average sea level to rise 57.2 meters or 188 feet.

"Persistent sea ice appears to have helped maintain a degree of stability in the Antarctic Ice Sheet".

As oceans grow warmer and weaker areas of East and West Antarctica become exposed, Rignot noted that more research needs to be done and fast.

The continent's glaciers accumulate ice from snowfall, and these snow crystals are buried under more recent precipitation, eventually reaching a depth where they are compacted into glacier ice.

"[But] the places undergoing changes in Antarctica are not limited to just a couple places". This massive body of ice flows out into the ocean through a complex array of partially submerged glaciers and thick floating expanses of ice called ice shelves. However, in the period from 2009 to 2017, this figure jumped to 252 billion tons.

The continental ice sheet is, by far, the largest single mass of ice on Earth - miles deep in places and containing more than 26 million cubic kilometers of ice.

It takes 360 billion tons of ice to produce one millimetre of global sea-level rise.

"All of these data suggest we need to get cracking and reduce our greenhouse gas emissions", warned Levy, "we don't want to lose that sea ice".

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