Nasa image shows giant iceberg breaking off Greenland glacier
Petermann Glacier calves a second iceberg in two years, raising concerns at the rapid pace of ice loss
NASA satellite imagery has captured an iceberg twice the size of Manhattan breaking free from a Greenland glacier.
It is the second time in two years that the Petermann Glacier has spawned an ice island: in 2010 another huge iceberg broke off into the sea.
The glacier sits mostly on land but a section of it sticks out over the water like a frozen tongue, this is where the chunks break off, a process known as 'calving'.
Like other glaciers, Petermann is expected to calve periodically, but ice breaks of this scale - and only two years apart - are unprecedented.
"It's dramatic. It's disturbing," said Andreas Muenchow, an Arctic oceanographer at the University of Delaware.
"We have data for 150 years and we see changes that we have not seen before".
Scientists always closely monitor the Petermann Glacier at this time of year; if icebergs reach the coast of Newfoundland they can cause significant danger to shipping and navigation. The 2010 iceberg did reach this area but caused no damage.
This time the iceberg has broken off further upstream, much closer inland than scientists have ever seen.
Reuters reports this could accelerate the glacier's ongoing flow towards the sea as the iceberg may have been blocking movement. The 2010 break increased the Petermann Glacier's movement by between 10 and 20 per cent, which was "significant but not dramatic", said Meunchow.
Recently, many of Greenland's southern glaciers have been melting at an unusually rapid pace but the latest development brings large ice loss much further north than expected.
"It is not a collapse, but it is certainly a significant event," Nasa glaciologist Eric Rignot said. "This is not part of natural variations anymore."
The ice lost so far from the glacier was already floating, so the latest breaks won't add to global sea levels. That could change if the melting continues, however, and parts of Petermann that are currently lying on land are lost.
Scientists also reported this week that the Arctic experienced the largest sea ice loss on record for June.
According to Meunchow, climate change is certainly a factor in the changing state of the Petermann Glacier. "The Greenland ice sheet is changing rapidly before our eyes," he said.