London, July 26: A massive icesheet in Greenland melted this month over an unusually larger area, which was detected after analysing radar data from the Indian Space Research Organisation's ( ISRO) Oceansat- 2 satellite.
The “ unprecedented” melting is the highest in three decades of satellite observation, Nasa said in a statement.
Melting even occurred at Greenland's coldest and highest place, Summit station.
The thawed ice area jumped from 40 per cent of the icesheet to 97 per cent in just four days from July 8 to July 12.
Although about half of Greenland's icesheet melts over the summer, the speed and scale of this year's melting surprised scientists, who described the phenomenon as “ extraordinary”.
Son Nghiem of Nasa's JPL (Jet Propulsion Laboratory) in Pasadena, California, was analysing radar data from Oceansat- 2 satellite last week when he noticed that most of Greenland appeared to have undergone surface melting on July 12.
“ This was so extraordinary that at first I questioned the result: was this real or was it because of a data error?” Nghiem said.
Nasa said nearly the entire ice cover of Greenland, from its thin, low- lying coastal edges to its centre, which is 3 km thick, experienced some degree of melting at its surface.
“ Satellite observations are helping us understand how events like these may relate to one another as well as to the broader climate system,” Tom Wagner, Nasa's cryosphere program manager in Washington, said.
He added that because the Greenland- wide melting has happened before, Nasa was not yet able to determine whether it is a natural but rare event, or if it has been sparked by manmade global warming.
Scientists said they believed much of Greenland's ice was already freezing again.
Until now, the most extensive melting seen by satellites in the past three decades was about 55 per cent of the area. Ice last melted at Summit station in 1889.
The news comes just days after Nasa satellite imagery revealed that a huge iceberg had broken off a glacier in Greenland.
