The surface of Greenland’s massive ice sheet has melted this month over an unusually large area, Nasa has said.
Scientists said the “unprecedented” melting took place over a larger area than has been detected in three decades of satellite observation.
Melting even occurred at Greenland’s coldest and highest place, Summit station.
The thawed ice area jumped from 40% of the ice sheet to 97% in just four days from 8 July.
Although about half of Greenland’s ice sheet normally sees surface melting over the summer months, the speed and scale of this year’s thaw surprised scientists, who described the phenomenon as “extraordinary”.
Nasa said that nearly the entire ice cover of Greenland, from its thin, low-lying coastal edges to its centre, which is 3km (two miles) thick, experienced some degree of melting at its surface.
Until now, the most extensive melting seen by satellites in the past three decades was about 55% of the area.
According to ice core records, such pronounced melting at Summit station and across the ice sheet has not occurred since 1889.
“When we see melt in places that we haven’t seen before, at least in a long period of time, it makes you sit up and ask what’s happening,” Nasa chief scientist Waleed Abdalati said.
“It’s a big signal, the meaning of which we’re going to sort out for years to come.” See before and after pictures in BBC.