Greenland’s massive ice sheet has melted this month over an usually large area, NASA has said.
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% of the ice sheet to 97% in just four days from 8 July.
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”.
Scientists said the "unprecedented" melting took place over a larger area that ever detected in three decades of satellite observation
NASA said that nearly the entire ice cover of Greenland, from its thin, low-lying coastal edges to its centre, which is 3 km (two miles) thick, experienced some degree of melting at its surface.
“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.”
He said that because this Greenland-wide melting has happened before they are not yet able to determine whether this is a natural but rare event, or if it has been sparked by man-made global warming.
Scientists said they believed that 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% of the area.
Ice last melted at Summit station in 1889, ice core records show.
The news comes just days after NASA satellite imagery revealed that a massive iceberg, twice the size of Manhattan, had broken off a glacier in Greenland.
“This event, combined with other natural but uncommon phenomena, such as the large calving event last week on Petermann Glacier, are part of a complex story,” said NASA’s Tom Wagner.
The Petermann Glacier in northern Greenland has calved an iceberg twice the size of Manhattan, scientists say.
Images from a NASA satellite show the island breaking off a tongue of ice that extends at the end of the glacier.
In 2010 an ice island measuring 250 square km (100 square miles) broke off the same glacier.
Glaciers do calve icebergs naturally, but the extent of the changes to the Petermann Glacier in recent years has taken many experts by surprise.
The Petermann Glacier in northern Greenland has calved an iceberg twice the size of Manhattan
“It is not a collapse but it is certainly a significant event,” Eric Rignot from NASA said in a statement.
Some other observers have gone further.
“It’s dramatic. It’s disturbing,” University of Delaware’s Andreas Muenchow told the Associated Press. “We have data for 150 years and we see changes that we have not seen before,” Andreas Muenchow added.
However, the calving is not expected have an impact on sea levels as the ice was already floating.
Icebergs from the Petermann Glacier sometimes reach the coast off Newfoundland in Canada, posing a danger to shipping and navigation, according to the Canadian Ice Service.
Scientists have also raised concerns in recent years about the Greenland ice shelf, saying that it is thinning extensively amid warm temperatures.
Solar Dynamics Observatory, a NASA satellite, captured amazing pictures of a gigantic tornado moving across the sun.
The tornado is larger than it might look – in fact, it is probably bigger than the Earth, and could extend hundreds of thousands of miles out into space.
And while its progress over the sun’s surface seems almost stately, it is moving at 300,000 miles per hour.
The extraordinary phenomenon – which cannot yet be fully explained by scientists – was filmed by NASA’s Solar Dynamics Observatory (SDO) over a 30-hour period earlier this month.
That satellite, known as the SDO, is in the middle of a five-year mission to monitor how solar activity affects the Earth, particularly changes in the sun’s magnetic field.
Solar Dynamics Observatory, a NASA satellite, captured amazing pictures of a gigantic tornado moving across the sun
While the tornado – called a “solar prominence” by scientists – looks very similar to twisters here on Earth, its origins are completely different.
Rather than being the result of atmospheric pressure, the solar activity comes from fluctuations in the sun’s magnetism.
However, researchers cannot explain much more than that – NASA’s Terry Kucera told Fox News that she and her colleagues were “still looking to understand what’s happening with these things”.
The tornado, at 15,000 degrees Fahrenheit (8,000 C), is much cooler than its surroundings, which are around 2 million degrees.
The phenomenon was not caught on camera until 1996.