Three satellites found that 97 percent of Greenland's surface ice cover melted never before seen in more than 30 years of satellite observations, NASA's Jet Propulsion Laboratory reported Tuesday.
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, NASA said in a news release.
"This was so extraordinary that at first I questioned the result: was this real or was it due to a data error?" Son Nghiem of NASA's Jet Propulsion Laboratory said.
Nghiem was analyzing radar data from the Indian Space Research Organization's (ISRO) Oceansat-2 satellite when he noticed that most of Greenland appeared to have undergone surface melting on July 12. Results from other satellites then confirmed the findings.
Researchers have not yet determined whether the extensive melt event, which coincided with an unusually strong ridge of warm air over Greenland, will affect the overall volume of ice loss this summer and contribute to a rise in sea level.
In the summer, on average about half of the surface of Greenland's ice sheet melts naturally. 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.
"But if we continue to observe melting events like this in upcoming years, it will be worrisome," said Lora Koenig, a glaciologist at NASA's Goddard Space Flight Center.
