Iceberg twice the size of Manhattan breaks away from Greenland glacier

18 Jul 2012

The iceberg calving from Greenland's Petermann glacier on 17 July. Image by NASA

An iceberg that’s reportedly twice the size of Manhattan, New York, has torn away from Greenland’s Petermann glacier. The event has been captured by NASA’s Aqua satellite. Some scientists are claiming that recent global warming is to blame.

A massive iceberg measuring 260 sq kilometres already broke off of the Petermann Glacier in 2010.

Petermann Glacier is in north-west Greenland to the east of Nares Strait. It connects the Greenland ice sheet to the Arctic Ocean.

As for the latest ice loss from the glacier, researchers from the University of Delaware and the Canadian Ice Service have estimated that the ice island that broke free was twice the size of Manhattan, at 46 sq kilometres.

NASA’s imaging spectroadiometer in its Aqua satellite captured the new iceberg calving and drifting downstream on 16-17 July 2012.

The space agency’s polar-orbiting satellite makes multiple passes over the polar regions each day.

NASA’s Earth Observatory reported that at 10.25am (UTC) on 16 July the iceberg was still close to the glacier. However, at 12pm (UTC) that same day the berg had started moving northward down the fjord.

Then, on 17 July, the same satellite spied a larger opening between the glacier and the iceberg, as well as some break-up of the thinner, downstream ice.

“The Greenland ice sheet as a whole is shrinking, melting and reducing in size as the result of globally changing air and ocean temperatures and associated changes in circulation patterns in both the ocean and atmosphere,” said Andreas Muenchow, an associate professor of physical ocean science and engineering at the University of Delaware.

Satellite image of the ice island that calved off the glacier on 5 August 2010

Satellite image of the ice island that calved off the glacier on 5 August 2010

In his Icy Seas blog, Muenchow claimed the air around northern Greenland and Ellesmere Island has warmed by about 0.11 +/- 0.025°C per year since 1987. 

“Northwest Greenland and north-east Canada are warming more than five times faster than the rest of the world,” Muenchow wrote.

However, he said the “observed warming” is not proof that the diminishing ice shelf is caused by this.

Muenchow said this is because air temperatures have little effect on this glacier. “Ocean temperatures do, and our ocean temperature time series are only five to eight years long – too short to establish a robust warming signal,” he said.

Floating taxi for polar bears and marine life

Muenchow believes this latest iceberg to break away from the Petermann Glacier will follow the path of the 2010 ice island. He said it would provide a “slow-moving floating taxi” for polar bears, seals and other marine life.

Back in 2003, Muenchow and his research team installed an ocean and sea ice observing array with U.S. National Science Foundation support in Nares Strait. The array has recorded data up to 2009.

Now, the Canadian Coast Guard ship Henry Larsen is set to make a voyage to Nares Strait and Petermann Fjord later this summer to recover moorings placed by the University of Delaware in 2009.

The scientists are hoping to recover the data from these moorings in order to glean more insights about ocean current, temperature, salinity and ice thickness at better than hourly intervals from 2009 up to now.

Carmel Doyle was a long-time reporter with Silicon Republic