NASA says Greenland's massive ice sheet has melted this month over an usually large area. Scientists said the unprecedented melting took place over a larger area that ever 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 per cent of the ice sheet to 97 per cent in just four days from July 8. Although about half of Greenland's ice sheet normally melts over the summer months, the speed and scale of this year's melting surprised scientists, who described the phenomenon as extraordinary.