July’s record-breaking scorcher hit Greenland hard this month, melting 97 percent of the surface ice cover to some degree in just a few days.
“This was so extraordinary that at first I questioned the result: was this real or was it due to a data error?” said Son Nghiem of NASA’s Jet Propulsion Laboratory in a press release. Ngheim was the first to notice Greenland’s extreme thaw while he analyzed satellite images.
Normally about half of Greenland’s ice cap shows signs of melting in mid-summer. But by July 12 this year, nearly all of the ice’s surface was one ginormous slushy.
“The melting spread quickly. Melt maps derived from the three satellites showed that on July 8, about 40 percent of the ice sheet’s surface had melted. By July 12, 97 percent had melted,” reported NASA in a press statement.
Even in Greenland’s heartland, temperatures reached slightly above freezing at Summit Station, a frigid high point 2 miles (3.2 kilometers) above sea level. Much of the water that melts inland will eventually refreeze, but on the coasts the water runs off the ice caps and contributes to the globally-averaged rising sea level.
The melt occurred after a series of strong ridges of warm air parked over Greenland. Each ridge turned up the heat a little more. While such warmth is unusual, ice cores suggest that cap melts this extreme may occur on a regular basis.
“Ice cores from Summit show that melting events of this type occur about once every 150 years on average. With the last one happening in 1889, this event is right on time,” said Lora Koenig, a Goddard glaciologist and a member of the research team analyzing the satellite data in a press release. “But if we continue to observe melting events like this in upcoming years, it will be worrisome.”
Greenland seen from the space shuttle Atlantis. (Corbis)
Melt water on the Greenland ice sheet near Camp Victor north of Ilulissat. (Ashley Cooper, Corbis)
Extent of surface melt over Greenland’s ice sheet on July 8, 2012, (left) and July 12, 2012 (right). (Nicolo E. DiGirolamo, SSAI/NASA GSFC, and Jesse Allen, NASA Earth Observatory)