March 9, 2011

Polar Ice Sheet Mass Loss A Growing Problem

Ice sheets have been losing mass at an accelerated rate over the past two decades, and these changes could soon become the dominant contributor to rising global sea levels, a NASA-funded study has discovered.

The results of the nearly 20-year satellite research project--the longest study ever to track changes in polar ice sheet mass--showed that ice sheets in Greenland and the Antarctic lost an average of 475 gigatons of combined mass annually.

Each gigaton is roughly equal to 2.2 trillion pounds, and that ice loss, NASA said in a Tuesday press release, is enough to raise the worldwide sea level by an average of 0.05 inches each year.

Yet the melting of the ice sheets seem to have worsened over time, they say. Each year, the two ice sheets studied by the US space agency lost a combined average of 36.3 gigatons more each year than they had the previous year, according to the NASA press release.

The research was completed by Eric Rignot of NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California, and colleagues, and will be published in the journal Geophysical Research Letters.

According to Alex Morales of Bloomberg, Rignot and his team say that they compared two independent sets of measurements in order to validate their findings.

"That ice sheets will dominate future sea level rise is not surprising--they hold a lot more ice mass than mountain glaciers," Rignot, lead author of the study, said in a statement Tuesday.

"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," he added.

According to the press release, "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 centimeters (5.9 inches) by 2050. When this is added to the predicted sea level contribution of 8 centimeters (3.1 inches) from glacial ice caps and 9 centimeters (3.5 inches) from ocean thermal expansion, total sea level rise could reach 32 centimeters (12.6 inches)."

The Institute for Marine and Atmospheric Research at Utrecht University in the Netherlands and the National Center for Atmospheric Research (NCAR) in Boulder, Colorado were also credited as institutions participating in the research project.


Image 1: 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. Image credit: Eric Rignot, NASA JPL

Image 2: Total ice sheet mass balance between 1992 and 2009, as measured for Greenland (top), Antarctica (middle) and the cumulative sum of both ice sheets (bottom), in gigatons per year, as measured by the two different methods used by the researchers: the mass budget method (solid black circles) and time-variable gravity measurements from the NASA/German Aerospace Center's Gravity Recovery and Climate Experiment (Grace) satellites (solid red triangles). Image credit: NASA/JPL-UC Irvine-Utrecht University-National Center for Atmospheric Research


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