Largest ice sheet on Earth was stable throughout last warm period

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But another decade after that, between 2012 and 2017, that number was 219 billion metric tons of ice lost per year.

The rate at which Antarctica is losing ice has more than doubled since 2012, according to the latest available data.

Changes in the Antarctic ice sheet's contribution to global sea level, 1992 to 2017.

Scientists have acknowledged that these sad results surpassed their expectations.

"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.

"We took all the estimates across all the different techniques, and we got this consensus, " said Isabella Velicogna, an Antarctic expert at the University of California, Irvine, and one of the many authors from institutions in 14 separate countries.

Looking closer, the rapid, recent changes are nearly entirely driven by the West Antarctic ice sheet, which scientists have long viewed as an Achilles' heel. Then the melting accelerated significantly, and since 2012 the rate has jumped to more than 241 billion tons a year - adding 0.6 mm per year to sea level rise. Ice shelf collapse in the Antarctic Peninsula is another major contributor, whereas less certain estimates of East Antarctica's mass change suggest the region may have gained a negligible amount of ice. They say that by 2100, Antarctica's melting ice alone could contribute to the rise of sea levels by six inches, or 15 centimeters.

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.

Worryingly, the paper demonstrates that the rate of ice loss has tripled in recent times.

In the last quarter century, the southern-most continent's ice sheet - a key indicator of climate change - melted into enough water to cover Texas to a depth of almost 13 feet (4 meters), scientists calculated.

Regardless of the exact rate, these findings emphasize the importance of efforts to combat climate change.

East Antarctica has sometimes been a focus of attention for people who deny the science of global warming. "So, every incremental increase in sea level rise really has impacts in terms of flooding".

"According to our analysis, there has been a steep 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", he added.

The changes will not be steady, in any case, said Knut Christianson, an Antarctic researcher at the University of Washington in Seattle, by email. That loss made global oceans rise about three-tenths of an inch, or 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".

"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".

Even more grim, a half-century of high emissions by this point would have locked in more than 10 metres (33 ft) of future sea level rise in coming millennia - and could potentially lead to more than 50 metres of sea level rise over the next 10,000 years.

"These events and the sea-level rise they've triggered are an indicator of climate change and should be of concern for the governments we trust to protect our coastal cities and communities".