Polar ice melt speeds up

Store Glacier, West Greenland. A new NASA funded study finds that the Greenland and Antarctic ice sheets are losing mass at an accelerating pace, three times faster than that of mountain glaciers and ice caps.
Eric Rignot, NASA JPL
Date:17 March 2011 Tags:

Our sea levels could rise by more than 30 cm by 2050 if polar ice sheets continue melting at their current rate, a study has predicted.
Greenland and Antarctic ice sheets are losing mass so fast that they will soon become the dominant contributor to global sea level rise, much sooner than model forecasts have predicted, the study found.
The authors conclude that, if current ice sheet melting rates continue for the next four decades, their cumulative loss could raise sea level by 15 centimetres by 2050. When this is added to the predicted sea level contribution of 8 centimetres from glacial ice caps and 9 centimetres from ocean thermal expansion, total sea level rise could reach 32 centimetres. However, they caution that considerable uncertainties remain in estimating future ice loss acceleration.
Conducted over nearly two decades, the study – published in Geophysical Research Letters and funded by Nasa, suggests that these ice sheets are overtaking ice loss from mountain glaciers and ice caps. The study is the longest to date of changes in polar ice sheet mass.
In 2006, the Greenland and Antarctic ice sheets lost a combined mass of 475 billion tons (gigatons) a year. To put that in perspective, the effect would have been to raise sea level by an average of 1,3 millimetres. But polar ice is disappearing faster and faster.
Each year over the course of the study, the two ice sheets lost a combined average of 36,3 gigatons more than the year before.
In comparison, a 2006 study of mountain glaciers and ice caps estimated their loss at 402 gigatons a year on average, with a year-over-year acceleration rate three times smaller than that of the ice sheets.
Of course, ice sheets hold much more water than mountain glaciers, said lead author Eric Rignot, jointly of Nasa's Jet Propulsion Laboratory and the University of California, Irvine. "What is surprising is this increased contribution by the ice sheets is already happening. If present trends continue, sea level is likely to be significantly higher than levels projected by the United Nations Intergovernmental Panel on Climate Change in 2007. Our study helps reduce uncertainties in near-term projections of sea level rise."

Rignot's team combined nearly two decades (1992-2009) of monthly satellite measurements with advanced regional atmospheric climate model data to examine changes in ice sheet mass and trends in acceleration of ice loss.


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