NASA: Ice sheet loss at both poles increasing




NASA: Ice sheet loss at both poles increasing

NASA says new study strongly suggests that rate of ice sheet loss is increasing.

A team of researchers supported by NASA and the ESA has compiled data from several satellites and aircraft to generate the most comprehensive and accurate assessment to date of ice sheet losses at both poles and their contributions to sea levels rise, according to the space agency.

The study reveals strong evidence that the rate of ice sheet loss has increased in Greenland and Antarctica during the last 20 years. Nearly 50 researchers from 26 laboratories around the world contributed to the study.

The study finds that these ice sheets are losing more than three times as much ice each year (equivalent to sea level rise of 0.04 inches) as they were in the 1990s (equivalent to 0.01 inches). Researchers note that approximately two-thirds of the loss is coming from Greenland, with the rest from Antarctica.

The rate of ice sheet losses determined by the study falls within the range reported in 2007 by the Intergovernmental Panel on Climate Change (IPCC). Researchers say, however, that their estimates are more than twice as accurate as the IPCC’s estimates because of the addition of more satellite data. Melting of ice sheets in Greenland and Antarctica contributed 0.44 inches to global sea levels since 1992. Ice sheet losses account for one-fifth of all sea level rise over the 20-year survey period. Thermal expansion of the warming ocean, melting of mountain glaciers and small Arctic ice caps and groundwater mining account for the rest.

The study combined observations from 10 satellite missions to create an accurate assessment of polar ice sheet changes. By expertly matching observation periods and survey areas, researchers reconciled differences among dozens of earlier ice sheet studies. They also combined measurements obtained by various types of satellite sensors like ESA’s radar missions and NASA’s Ice, Cloud and land Elevation Satellite (ICESat).

“What is unique about this effort is that it brought together the key scientists and all of the different methods to estimate ice loss,” said Tom Wagner, NASA’s cryosphere program manager, in a statement. “It’s a major challenge they undertook, involving cutting-edge, difficult research to produce the most rigorous and detailed estimates of ice loss from Greenland and Antarctica to date. The results of this study will be invaluable in informing the IPCC as it completes the writing of its Fifth Assessment Report over the next year.”

Study coordinator Andrew Shepherd of the University of Leeds is confident that the undertaking was a success due to the cooperation of the international scientific community and accuracy of different satellite sensors.

“Without these efforts, we would not be in a position to tell people with confidence how Earth’s ice sheets have changed, and to end the uncertainty that has existed for many years,” Mr. Shepherd said.

The study notes several differences in the pace of ice sheet loss in Antarctica and Greenland.

“Both ice sheets appear to be losing more ice now than 20 years ago, but the pace of ice loss from Greenland is extraordinary, with nearly a five-fold increase since the mid-1990s,” said Erik Ivins of NASA’s Jet Propulsion Laboratory. “In contrast, the overall loss of ice in Antarctica has remained fairly constant, with the data suggesting a 50-percent increase in Antarctic ice loss during the last decade.”

The team’s findings were discussed Thursday in the journal Science.


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