Antarctica Is Melting Three Times Faster Than a Decade Ago

Experts fear the future may be grim if greenhouse gas emissions continue unabated

IAN JOUGHIN WASHINGTON UNIVERSITY Experts fear the future may be grim if greenhouse gas emissions continue unabated

The latest data is a continuation of previous assessments known as the Ice sheet Mass Balance Inter-comparison Exercise (IMBIE), which began in 2011 and tracks ice-sheet loss from 1992 onwards.

The West Antarctic lost 159 billion tons of ice each year on its own between 2012 and 2017 - more than 72% of the entire Antarctic ice sheet. The main factor behind that gain appears to be fluctuations in snowfall, researchers said.

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

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

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".

Satellites contributing to the project include CryoSat, Sentinel-1 and the U.S.

The East Antarctic Ice Sheet (EAIS) is the largest potential contributor to future sea level rise, but projections are hindered by uncertainty in how the EAIS responded to past warm periods, for example during the Pliocene (5.3-2.6 Myr ago) when atmospheric Carbon dioxide concentrations were last ≥ 400 ppm. The combined effects of climate variability, atmosphere, and ocean circulation, and even ice shelf melting have driven regional changes, including reductions in sea ice in the Amundsen and Bellingshausen seas.

A series of research papers in the journal Nature tells a story of ice loss and global concern.

Shepherd said the ice on West Antarctica can be melted by very small changes in ocean temperature.

If the West Antarctic ice sheet continues to disintegrate and ends up collapsing, then we could see an increase of more than 10 feet. Without them, there is nothing to stop vast amounts of grounded ice forming the Antarctic Ice Sheet from flowing into the Southern Ocean and raising sea levels. 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. The rate of sea-level rise due to Antarctic ice loss has tripled since 2012, he said.

If not enough is done to curb greenhouse gas emissions, changes to the Antarctic environment will result in global sea levels rising by more than a metre (3.3ft) by 2070.

Their report explained how ice shelf thinning and collapse have triggered an increase in the continent's contribution to sea level rise. "Things are happening. They are happening faster than we expected".

He adds that the new results have implications for predicting global sea level rise in the future. As part of IMBIE, Professor Shepherd coordinated with 83 other scientists, from 44 global organizations, to combine the data from two dozen different satellite surveys for this comprehensive look at the changes in Antarctica's ice mass balance.

East Antarctica, which makes up two-thirds of the continent, is a remote region of an already remote location, where data is scarcer because there are fewer measurement stations, Koppes said.

If the land-based East Antarctic Ice Sheet was stable during the Pliocene, as Shakun and colleagues suggest, the Pliocene total could have been at most 30 meters.

The changes will not be steady, in any case, said Knut Christianson, an Antarctic researcher at the University of Washington in Seattle, by email. "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".

The discovery comes after the worldwide research team, from Australia, the United States and New Zealand, combined satellite images and surface and ocean wave data with modelling, to analyse five major ice shelf disintegrations, between 1995 and 2009.

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