The two ice sheets are losing about 2.2 trillion pounds of mass each year. This is occurring much sooner than climate model forecasts had predicted.
The study, which was published this month in the journal Geophysical Research Letters, analyzed almost 20 years of NASA satellite data.
"That ice sheets will dominate future sea level rise is not surprising -- they hold a lot more ice mass than mountain glaciers," said lead author Eric Rignot, jointly of NASA's Jet Propulsion Laboratory, Pasadena, Calif., 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."
The authors concluded that, if current ice-sheet melting rates continue for the next 40 years, their loss could raise sea level by 5.9 inches by 2050. When this is added to the predicted sea level contribution of 3.1 inches from glacial ice caps and 3.5 inches from ocean thermal expansion, total sea level rise could reach 12.6 inches.
However, the authors caution that considerable uncertainties remain in estimating future ice loss acceleration.
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