Huge iceberg breaks away from Petermann Glacier fuelling fears over global warming

Nasa satellite images show a crescent-shaped crack between the iceberg and glacier (Reuters)

For the second time in two years a huge piece of ice has broken away from the Petermann Glacier in Greenland -fuelling concerns about global warming.

An iceberg twice the size of Manhattan tore away from one of Greenland's largest glaciers scientists said.

For a number of years scientists had been observing a long crack close to the tip of the northerly Petermann Glacier.

A rift in the ice was first identified in 2001 and scientists have been observing it since. Nasa satellites showed on Monday that it had finally broken away from the glacier.

The iceberg, which measures 46-square-miles, was observed breaking away by Nasa's Aqua satellite which passes over the North Pole a number of times a day.

Two years ago a massive ice island, twice the size of the one this week, broke away from the Petermann Glacier.

The combination of the two incidents of iceberg calving have caught the attention of scientists and provoked growing concern over the impact of climate change on the region.

Because this ice was already part of the shelf attached to the land - but extended over water - its break away into open sea will have no immediate impact on sea levels, much as a melting ice cube in a glass of water does not raise the level of water in the glass.

Four-fifths of Greenland is covered by a massive ice sheet.

This week's ice calving occurred on part of the Petermann Glacier that juts out across the water like a frozen tongue.

The break occurred on part of a floating river of ice. It then moved downstream along a fjord on the northwest coast.

The ice split was spotted on Tuesday by Nasa, “The floating extension (of the glacier) is breaking apart,” Eric Rignot of NASA's Jet Propulsion Laboratory said in a statement. “It is not a collapse, but it is certainly a significant event.”

A key difference between this week's event and the one in 2010 is that the ice berg broke off further upstream where the ice is up against the fjord's side walls - effectively damming the glaciers seaward movement.

“This piece that has been much further back, may have actually been providing more of a frictional force to cork (the glacier) up than the piece that broke off in 2010, which was much further out,” said Andreas Muenchow, an Arctic oceanographer at the University of Delaware.

Floating ice tongue coastal glaciers of this type tend to block the ice flow headed for sea.

When the large sections of ice break loose the land-based glaciers tend to move more quickly behind them.

It is thought that the 2010 break accelerated the Petermann Glacier's movement towards the sea by around 10 to 20 percent.

Andreas Muenchow said his website that the accelerated movement of the Petermann Glacier after the 2010 break was “noticeable but not dramatic.”

Muenchow also said that climate change was a factor in in the changing state of the Glacier.

He says the glacier is as far back towards the land as it has been for 150 years.

Though researchers suggest that global warming is to blame for the changes in Greenland they are unable to prove it conclusively.

Though glaciers do naturally calve icebergs many scientists believe what has occurred in the last three years on the Petermann Glacier is not part of the natural variations.