Gravity Data Show that Antarctic Ice Sheet Is Melting Increasingly Faster

During the past decade, Antarctica's massive ice sheet lost twice the amount of ice in its western portion compared with what it accumulated in the east, according to Princeton University researchers who came to one overall conclusion -- the southern continent's ice cap is melting ever faster.

The researchers "weighed" Antarctica's ice sheet using gravitational satellite data and found that from 2003 to 2014, the ice sheet lost 92 billion tons of ice per year, the researchers report in the journal Earth and Planetary Science Letters.  If stacked on the island of Manhattan, that amount of ice would be more than a mile high -- more than five times the height of the Empire State Building.

The vast majority of that loss was from West Antarctica, which is the smaller of the continent's two main regions and abuts the Antarctic Peninsula that winds up toward South America. Since 2008, ice loss from West Antarctica's unstable glaciers doubled from an average annual loss of 121 billion tons of ice to twice that by 2014, the researchers found.  The ice sheet on East Antarctica, the continent's much larger and overall more stable region, thickened during that same time, but only accumulated half the amount of ice lost from the west, the researchers reported.

"We have a solution that is very solid, very detailed and unambiguous," said co-author Frederik Simons, a Princeton associate professor of geosciences.  "A decade of gravity analysis alone cannot force you to take a position on this ice loss being due to anthropogenic global warming. All we have done is take the balance of the ice on Antarctica and found that it is melting -- there is no doubt.  But with the rapidly accelerating rates at which the ice is melting, and in the light of all the other, well-publicized lines of evidence, most scientists would be hard pressed to find mechanisms that do not include human-made climate change."

Compared to other types of data, the Princeton study shows that ice is melting from West Antarctica at a far greater rate than was previously known and that the western ice sheet is much more unstable compared to other regions of the continent, said first author Christopher Harig, a Princeton postdoctoral research associate in geosciences.  Overall, ice-loss rates from all of Antarctica increased by 6 billion tons per year each year during the 11-year period the researchers examined.  The melting rate from West Antarctica, however, grew by 18 billion tons per year every year, Harig and Simons found.
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"The fact that West Antarctic ice-melt is still accelerating is a big deal because it's increasing its contribution to sea-level rise," Harig said.  "It really has potential to be a runaway problem. It has come to the point that if we continue losing mass in those areas, the loss can generate a self-reinforcing feedback whereby we will be losing more and more ice, ultimately raising sea levels by tens of feet."

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