Giant Ice Island Breaks Off From Greenland

(Aug. 7) -- A giant chunk of ice four times the size of Manhattan has broken off from one of Greenland's two biggest glaciers, creating the largest Arctic iceberg since 1962.

The new ice island has a surface area of about 100 square miles and a thickness of about half the height of the Empire State Building. It broke off from the Petermann Glacier on Thursday, and was spotted by a NASA satellite sensor.

"The freshwater stored in this ice island could keep the Delaware or Hudson rivers flowing for more than two years," University of Delaware researcher Andreas Muenchow said in a statement on the school's website. "It could also keep all U.S. public tap water flowing for 120 days."

Muenchow, a professor of physical ocean science and engineering, has been doing research in the Nares Strait between Greenland and Canada – where the new iceberg is likely heading. It could get stuck in the deep but narrow waterway -- possibly blocking key shipping routes -- or break up into smaller chunks there while being propelled by ocean currents out into the Atlantic within the next two years.

The U.S. Coast Guard's International Ice Patrol estimates that anywhere from 10,000 to 40,000 icebergs break off from Greenland's west coast in any given year. But what's unusual about this one is its size – more typical of Antarctica rather than the Arctic.

The last time such a massive iceberg formed in the Arctic was in 1962, when the Ward Hunt Ice Shelf gave birth to a 230-square-mile ice island which also broke up in the Nares Strait.

Icebergs often break off from glaciers in summer, when the ice begins to melt and gets thinner in some areas, triggering cracks. The process has been exacerbated by global warming, and the melting of arctic glaciers could lead to a rise in global sea levels.

Last month, Greenpeace researchers warned that the Petermann Glacier, the northern hemisphere's largest, was likely to crack soon.

"Ocean warming currents are circulating around the fjord here and eroding the underbelly of Petermann Glacier at an incredible rate, which is 25 times that of the surface melt," Alun Hubbard, a glaciologist at the University Of Wales, told the Sydney Morning Herald at the time. "There's been a revelation in the last couple of years in the role that warming oceans play in triggering the enhanced acceleration, break-up and thinning of these outlet glaciers."