Polar Ice-sheet melting jumps three-fold: NASA

Economic Times , Saturday, December 01, 2012
Correspondent :
NEW DELHI: The combined rate of melting for the ice sheets covering Greenland and Antarctica has increased during the last 20 years says a landmark study published Thursday in the journal Science. The study was carried out by an international team of 47 experts from 26 laboratories supported by NASA and the European Space Agency (ESA).

Together, these ice sheets are losing more than three times as much ice each year as they were in the 1990s. About two-thirds of the loss is coming from Greenland, with the rest from Antarctica. The current ice loss is equivalent to sea level rise of 0.04 inches or 0.95 millimeters while in the 1990s, it was equivalent to 0.01 inches or 0.27 millimeters per year, NASA said in a statement.

The scientists combined data from 10 satellite missions and aircraft to produce the most comprehensive and accurate assessment to date of ice sheet losses in Greenland and Antarctica and their contributions to sea level rise.

This rate of ice sheet losses falls within the range reported in 2007 by the Intergovernmental Panel on Climate Change (IPCC). The spread of estimates in the 2007 IPCC report was so broad, however, it was not clear whether Antarctica was growing or shrinking. The new estimates, which are more than twice as accurate because of the inclusion of more satellite data, confirm both Antarctica and Greenland are losing ice. Combined, melting of these ice sheets contributed 0.44 inches (11.1 millimeters) to global sea levels since 1992. This accounts for one-fifth of all sea level rise over the 20-year survey period. The remainder is caused by the thermal expansion of the warming ocean, melting of mountain glaciers and small Arctic ice caps, and groundwater mining.

The researchers reconciled differences among dozens of earlier ice sheet studies by carefully matching observation periods and survey areas. They also combined measurements collected by different types of satellite sensors, such as ESA's radar missions; NASA's Ice, Cloud and land Elevation Satellite (ICESat); and the NASA/German Aerospace Center's Gravity Recovery and Climate Experiment (GRACE).

"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 Washington, quoted in the NASA 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."

The study found variations in the pace of ice sheet change 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" . Erik Ivins of NASA's Jet Propulsion Laboratory in Pasadena said. "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."

 
SOURCE : http://economictimes.indiatimes.com/environment/global-warming/polar-ice-sheet-melting-jumps-three-fold-nasa/articleshow/17426983.cms
 


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