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May 29, 2007
UMBC/NASA Study Shows Increasing Snowmelt in Greenland
New Area the Size of Maryland Starts to Melt Each Year; Long-term Satellite Data Showed First-Ever High Altitude Melting in 2002
Some sobering findings on the extent of Greenland's melting ice sheets were published today as part of a long-term study of earth observing satellites’ data by researchers with the University of Maryland, Baltimore County (UMBC) and NASA-Goddard Space Flight Center.
Marco Tedesco, a scientist at the Joint Center for Earth Systems Technology (JCET) of UMBC and NASA-Goddard Space Flight Center, was lead author of a study published in the American Geophysical Union's journal Eos. By using a new method for detecting melting snow from satellites, Tedesco found that in 2006 Greenland experienced more days of melting snow and at higher altitudes than the previous trends from the past 18 years.
Tedesco used a new method for detecting melting snow based on readings from the Special Sensor Microwave Imaging radiometer (SSM/I), an instrument aboard the U.S. Air Force’s Defense Meteorological Satellite Program spacecraft. The SSM/I can see through clouds and can measure data without sunlight. Tedesco has tracked the data annually since 1988, allowing him to study big-picture trends in the duration and extent of Greenland's snowmelt.
Certain areas of Greenland were melting over 10 days longer than average in 2006. Greenland’s 2006 melt index, or the number of melting days times the melting area, continued on an upward trend seen in data from 1988 to 2005.
Results from another study by Tedesco published on Geophysical Research Letters on January 2007 show that the year 2002 showed signs of extreme melting. “We identified an extreme melting event in June 2002 that showed for the first time in 18 years snow melting in inner Greenland at high altitudes,” said Tedesco.
“During the same year, over 80 percent of the entire Greenland ice sheet surface experienced at least one day of melting. This corresponds to an area the size of France, Spain and Italy put together,” he said. The area experiencing at least one day of melting has been increasing since 1992 at a rate of 35,000 square kilometers per year, or about two percent of the entire Greenland surface. “That means that, on the average, every year since 1992 an area equivalent to the state of Maryland has been subject to new melting,” Tedesco said.
Left: UMBC JCET Researcher Marco Tedesco
According to Tedesco, tracking melting snow in Greenland, which contains enough water to raise global sea level by approximately 7 meters, is important for several reasons. “Although wet and dry snow look similar, they absorb sun’s radiation in a different way, with melting snow absorbing three to four times as much energy as dry snow, greatly affecting Earth’s energy budget,” said Tedesco.
“Also, melting snow produces liquid water that will seep down to the interface of ice and bedrock, lubricating the ice sheet and increasing the speed with which ice moves,” Tedesco said. “This means that ice might react to a warm climate faster than thought, contributing more rapidly to sea level than previously thought.”
Posted by crose at May 29, 2007 4:13 PM