Antarctica's ice sheet is melting 3 times faster than before


Prior to 2012, the rate of ice loss held mostly steady at around 76 billion tonnes per year - equating to a 0.2 mm annual contribution to sea level rise.

On current trends, Antarctica could become the single largest source of sea level rise, ahead of runoff from the Greenland ice sheet and mountain glaciers, and the expansion of ocean water as it warms, the study found. If all of the glaciers on the southern continent were to melt then sea level would rise by 58 meters (190 feet). They include Antarctic glaciers speeding up in the wake of ice shelf collapse, warming waters in the Amundsen sea-which lies to the west of the continent-and reduced ice sheet growth in East Antarctica.

As part of IMBIE, Professor Shepherd coordinated with 83 other scientists, from 44 worldwide organizations, to combine the data from two dozen different satellite surveys for this comprehensive look at the changes in Antarctica's ice mass balance.

The new findings are the result of the most complete satellite survey of Antarctic ice sheet change to date, involving 84 scientists from 44 global organizations (including NASA and the European Space Agency).

"Since around 2010, 2012, we can see that there's been a sharp increase in the rate of ice loss from Antarctica". "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", Andrew Shephard, lead author of the study and a professor at the University of Leeds, said in a statement. The water nibbles at the floating edges of ice sheets from below. Their results - known formally as the "Ice Sheet Mass Balance Inter-comparison Exercise" (IMBIE) - were published Wednesday in the journal Nature.

More than 70 percent of the recent melt is in West Antarctica.

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".

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. These "tell us about changes in the earth's gravitational attraction over time and that can be related to the mass of the ice sheets overall", Shepherd says, "and they are really powerful measurements because they can add up everything across Antarctica". If sea level continues to change at this rate and acceleration, the researchers estimate that average sea-level rise by 2100 will be closer to 24 inches than 10 inches in 2100.

"I don't know if it's going to keep exactly tripling, but I think it has a lot of potential to keep significantly increasing, " said Velicogna. But clues from the geologic record suggest that the climate change driving ice loss in Antarctica is doing so much faster than during its periods of ice loss in the distant past, Shepherd told Live Science.

The changes will not be steady, in any case, said Knut Christianson, an Antarctic researcher at the University of Washington in Seattle, by email. So we should expect "periods of stability interspersed with rapid retreat, " he said.

For the new study, the scientists combined data from three types of satellite measurements to track changes in ice over time, study co-author Andrew Shepherd, a professor of Earth observation with the School of Earth and Environment at the University of Leeds in the United Kingdom, told Live Science. "But remember for the northern hemisphere, for North America, the fact that the location in West Antarctica is where the action is amplifies that rate of sea level rise by up to an about additional 25 percent in a city like Boston or NY". And many of those papers showed different results.

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

Rising sea levels can have a unsafe impact on coastal habitats and communities as flooding increases along with higher tides and stronger storm surges.