In a worrisome sign tied to global warming, NASA announced Tuesday that Greenland experienced more days of melting snow and at higher altitudes last year than average over the previous 18 years that satellite measurements have been taken.
“The sensors detected that snowmelt occurred more than 10 days longer than the average over certain areas of Greenland in 2006,” said Marco Tedesco, a scientist at the Joint Center for Earth Systems Technology, which is managed by NASA’s Goddard Space Flight Center and the University of Maryland.
Areas along Greenland’s western, southeastern and northeastern coast saw the largest number of melt days last year.
Tedesco and his team have improved on the satellite measurements to where they can make multiple measurements on any given day.
The long-term fear is that Greenland's vast ice sheet will melt enough to raise sea levels around the world. A complete melt, while not expected, would raise oceans by 20 feet, swamping coastal areas.
“The melting snow produces liquid water that will potentially influence sea levels,” Tedesco, the lead author of the study published Tuesday in the journal Eos, said in a statement. “And some of the liquid water will drain into the glaciers through cracks and vertical passages, called moulins, reaching the bedrock below and lubricating the ice sheet."
Earlier NASA studies have found that the water from summer melting at the Greenland ice sheet's base can increase how fast the ice moves, "causing it to contribute more rapidly to sea level than previously thought," NASA said. "This phenomenon, together with others recently observed, suggest that the ice might respond more quickly to a warming climate."
Tedesco noted that even the melting snow that refreezes can have a significant impact on climate. “Although wet and dry snow look similar at first glance, wet and re-frozen snow absorb more of the sun’s radiation, reflecting only 50-60 percent back into the atmosphere," he said. "Dry snow, on the other hand, reflects about 85 percent of the sun’s radiation.
"In other words, melting snow absorbs three to four times as much energy as dry snow, greatly affecting Earth’s energy budget" by creating a feedback effect that can warm the ice sheet further.