Antarctic region shows sudden, surprising ice loss

No surprise if we are starting to get tipping points. They are inevitable, and we usually won't know we are approaching one until after the fact.

http://www.cbsnews.com/news/antarctic-region-shows-sudden-surprising-ice-loss/

By Michael Casey CBS News May 22, 2015

A region of Antarctica once thought to be relatively stable has shown a dramatic loss of ice in recent years, raising concerns about how much it could be contributing to rising seas.

Using data from satellites including the European Space Agency's CryoSat-2 satellite,which is dedicated to remote-sensing of ice, researchers found that the Southern Antarctic Peninsula showed no signs of change up until 2009. But soon after, multiple glaciers along a vast coastal expanse, measuring some 750 km (460 miles) in length, started to shed ice into the ocean at a nearly constant rate of 60 cubic km, or about 55 trillion liters of water, each year.

"It appears that sometime around 2009, the ice-shelf thinning and the subsurface melting of the glaciers passed a critical threshold that triggered the sudden ice loss," Bert Wouters, who led the study that appeared in Science this week and is with the Bristol Glaciology Centre at the University of Bristol, said.

This makes the region the second largest contributor to sea level rise in Antarctica. "To date, the glaciers added roughly 300 cubic km of water to the ocean," Wouters said. "That's the equivalent of the volume of nearly 350,000 Empire State Buildings combined."

The ice loss in the region is so large that it causes small changes in the gravity field of the Earth, which can be detected by another satellite mission, the Gravity Recovery and Climate Experiment (GRACE).

"The fact that so many glaciers in such a large region suddenly started to lose ice came as a surprise to us," Wouters said. "It shows a very fast response of the ice sheet: in just a few years the dynamic regime completely shifted."

Data from an Antarctic climate model shows that the sudden change cannot be explained by changes in snowfall or air temperature. Instead, the team attributes the rapid ice loss to warming oceans, whose temperatures have increased in recent years due to emissions from fossil fuels.

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