As ice in Greenland melts at the surface, water carves fissures and reaches the base, where ice meets land. This sub-glacial ice can lubricate a glacier, causing it to flow to the ocean faster and be depleted more quickly than would otherwise occur.
The icy mega-island of Greenland is slipping away faster than before, as it experienced more days of melting snow in 2006 than it does on average, new satellite observations show.
Satellite sensors taking daily observations of the ice since 1988 revealed that Greenland’s melting days have progressively increased and melting has increasingly taken place at higher altitudes.
“The sensors detected that snowmelt occurred more than 10 days longer than the average over certain areas of Greenland in 2006,” said study team leader Marco Tedesco, of the Joint Center for Earth Systems Technology, managed by the University of Maryland, Baltimore County, and NASA's Goddard Space Flight Center in Maryland.
Areas along Greenland’s western, southeastern and northeastern coasts witnessed the largest number of melt days in 2006.
More melting days could mean faster glacial flow and therefore more water pouring from the ice sheets into the ocean.
“The melting snow produces liquid water that will potentially influence sea levels,” Tedesco said. “And some of the liquid water will drain into glaciers through cracks and vertical passages, called moulins, reaching the bedrock below and lubricating the ice sheet.”
Previous studies have shown that melt water below ice sheets can speed their journey to the sea, where ice bergs calve, or break off, from the sheets, and potentially contribute to rising sea levels. A warming climate could ramp up the process even more.
The melting could cause less of the sun’s radiation to bounce back into the atmosphere, because snow that melts and refreezes absorbs more sunlight than dry snow. If more radiation is absorbed, polar temperatures could rise even more than they have already and are predicted to continue doing as a result of global warming.
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