Antarctica lost 3 trillion tonnes of ice in just 25 years

Media playback is unsupported on your device                  Media caption Andrew Shepherd

Two-fifths of that ice loss occurred in the last five years, a three-fold increase in the pace at which Antarctica is shedding its kilometres-thick casing, a consortium of 84 scientists reported in the journal Nature.

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

Ice loss of 2.7 trillion tons since 1992 added about 8mm to sea level.

The largest change by far is recorded in an area dominated by marine-terminating glaciers known as West Antarctica.

In April, a team of United Kingdom researchers released a report saying that underwater glaciers in Antarctica are melting at an "alarming rate". 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.

That's a lot of ice.

In total, that amounts to almost 3 trillion tonnes of ice lost, in just 25 years time.

In a controversial 2016 study, former NASA scientist James Hansen and a team of colleagues (including Velicogna) found that the Earth could see sea level rise above 1 meter (or 3.3 feet) within 50 years if polar ice sheet loss doubles every 10 years.

West Antarctica experienced the most acceleration in ice loss among regions studied during the research period, growing from 53 billion tons a year in the 1990s to 159 billion tons annually in the final five years.

That might not sound like much, but what's particularly concerning is the way the ice loss has sharply accelerated over the course of the 25-year timeframe. The absence of data about the East Antarctic Ice Sheet's response to warming in the past have hindered efforts to predict its role in future sea level rise.

In a new study, the most comprehensive to date of the continent's icy status, an worldwide group of 84 researchers analyzed data from multiple satellite surveys, from 1992 to 2017.

Overall, though, the continent is losing the mass of its ice, and if the world continues to warm, this loss can only accelerate.

"To see a threefold increase just since 2012 - that's disturbing to me", said Brenda Ekwurzel, director of climate science for the Climate and Energy Program at the Union of Concerned Scientists.

However, the role of sea ice in buffering ice shelves and continental ice sheets is rarely factored into Antarctic ice-loss modelling, according to lead researcher Dr Rob Massom from the Australian Antarctic Institute.

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.

"The next piece of the puzzle is to understand the processes driving this change", Whitehouse added.

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.

"The fate of Antarctica, the fate of Greenland, is the fate of Miami", she said.

The Antarctic ice sheets are melting many times faster than previously thought, significantly increasing the rise of global sea levels in recent years, according to a new research by a group of U.S. and United Kingdom scientists. "To do this, we need to keep watching the ice sheet closely, but we also need to look back in time and try to understand how the ice sheet responded to past climate change". This uncertainty persists because global sea level estimates for the Pliocene have large uncertainties and can not be used to rule out substantial terrestrial ice loss, and also because direct geological evidence bearing on past ice retreat on land is lacking.

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