Tuesday, 14 August, 2018

Antarctica is losing ice at an increasingly rapid rate

Sea level contribution due to the Antarctic ice sheet between 1992 and 2017 from data gathered by international Antarctica Has Lost 3 Trillion Tonnes of Ice Since '92
Sandy Nunez | 15 June, 2018, 00:25

Antarctica has lost 3 trillion tons of ice in the past 25 years, and that ice loss has accelerated rapidly over the last five years.

"This has to be a concern for the governments we trust to protect our coastal cities and communities", says Andrew Shepherd from the University of Leeds, one of the study leads.

The analysis suggests that 3 trillion tons' worth of Antarctic ice losses have increased global sea levels by 7.6 mm (0.3 inches) since 1992, and that the increase is accelerating. Since then, however, the melt rate has increased dramatically from an average of about 84 billion tons a year between 1992 and 2011, to more than 241 billion tons a year from 2012 to 2017. It holds enough water to cause as much as 34 meters of sea level rise if the ice sheet were to melt completely.

Pine Island Glacier in Antarctica is melting at an alarming rate.

However, if emission were low, the ice shelves would remain intact, Antarctica would make a small contribution to sea level rise, and the continent would remain a "natural reserve, dedicated to peace and science" as agreed by Antarctic nations in the late 20th century.

"With the number of scientific studies focusing on this region, the technological tools we have at our disposal and data sets spanning several decades, we have an unequivocal picture of what's happening in Antarctica", Eric Rignot, an Earth system science professor at the University of California Irvine who participated in the research, said in a statement.

Altogether, across the continent, 34,000 square kilometers (13,000 square miles) of the ice shelf has been lost since the 1950s.

But afterwards, that sped up remarkably, resulting in a three-fold increase from 2012 to 2017, during which the continent lost some 219 billion tonnes of ice every year, pushing the ocean up 0.6 mm annually.

It's "possible that Antarctica alone can add about half a foot to sea level rise by the end of the century", Shepherd said in an interview with The Associated Press.

And now data from satellites launched by the European Space Agency, Japan, Canada, NASA, Italy and Germany has been combined into something known as the Ice Sheet Mass Balance Inter-comparison Exercise, or IMBIE for short. The rate at which ice losses from Antarctica will increase in response to a warming world remains uncertain.

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To get around those problems in this study, more than 80 researchers from around the world collected data from about a dozen different satellite measurements dating to the early 1990s.

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

"Satellites have given us an fantastic, continent-wide picture of how Antarctica is changing", said Dr. Pippa Whitehouse, a member of the IMBIE team from Durham University, according to a University of Leeds press release.

Much of the East Antarctic Ice Sheet is land-based.

If the volcanoes are active, they could erupt at any moment, melting vast amounts of ice and contributing to the already worrisome rising sea levels endangering large swathes of coastal populations around the globe.

"The next piece of the puzzle is to understand the processes driving this change", Durham University's Pippa Whitehouse said.

The researchers concluded that the changes in East Antarctica were not almost enough to make up for the rapid loss seen in West Antarctica and the Antarctic Peninsula.

"If you start removing mass from there, you can have a very large scale evacuation of ice into the ocean and significant sea level rise, " she continued.

The researchers relied on samples taken as part of the global ANtarctic geological DRILLing (ANDRILL) project.