Trudy Wohlleben, a forecaster from the Canadian Ice Service, spotted the massive slab of ice that broke off a glacier in Greenland last week as she analyzed raw data from a NASA satellite.

At about 30 kilometers (18.6 miles) long and 10 kilometers wide, the ice island is about four times the size of Manhattan and experts say the last time the Arctic lost such a large chunk was in 1962.

Wohlleben played down fears the giant iceberg would pose an immediate threat to oil platforms or shipping lanes, saying it would first have to navigate a series of small islands in the Nares Strait.

It is likely to get broken down into smaller chunks before it reaches the shipping lanes off the Labrador Coast in Newfoundland, she said, and could even become lodged in a channel or stuck to land.

"In the next one to two years it could reach the east coast of Canada," she told AFP, explaining that unlike in the days when the Titanic sank in 1912, ships now have the latest satellite data to warn them of dangerous icebergs.

Satellite images of the area show that the Petermann glacier lost about one-quarter of floating ice-shelf. The phenomenon is known as "ice calving."

"On August 3, it was not there. Then the clouds prevented pictures from being taken, and on Thursday August 5 I saw it in the morning," Wohlleben recounted.

The Petermann glacier is one of Greenland's two largest that end in floating shelves and connects the Danish territory's ice sheet directly with the ocean.

Scientists have said that while global warming probably contributed to the break, ocean currents and Arctic winds could also be responsible.

Wohlleben refused to be drawn on the climate debate.

"It is hard to say," she told AFP. "There are just so many factors that could play a role."

Paal Prestrud, the head of the climate research group Cicero, said warmer waters likely caused the block of ice to break away, but added: "It's difficult to say for sure it's due to global warming.

"But you see the same things happening all around Greenland, ice shelves breaking up, the outletting glaciers are increasing their speed and retreating faster and faster, and the total mass of ice is decreasing."

earlier related report
Huge iceberg to threaten ships, oil wells
Nuuk, Greenland (UPI) Aug 11, 2010 - An ice sheet four times bigger than Manhattan has split off from Greenland's coast and could threaten shipping lanes and oil platforms in the Atlantic Ocean.

On Aug. 5, Trudy Wohlleben, a researcher at the Canadian Ice Service, glanced at her computer screen in excitement. She had been monitoring the Petermann Glacier on Greenland's northwestern coast for a while and she said she had expected the melting glacier to release a significant chunk of ice -- but not one as big as this.

The ice sheet that broke off last week, in a process experts call "calving," spans across 100 square miles, an area four times larger than the island of Manhattan.

"It's so much bigger than any other one that's calved," Wohlleben told Deutsche Welle. "The last large one of this size was back in the '60s … If you were on a ship, it would look like a big wall of ice rising out of the ocean."

While glaciers regularly shed chunks of ice, the size of the sheet that broke off last week has scientists worried.

It's floating toward the Nares Strait, a waterway between northern Canada and Greenland, and is expected to eventually make its way into the North Atlantic. It's normal for ice sheets that have calved to break into smaller pieces as they move south. Generally, they don't pose a significant threat to container ships and oil platforms because they're too small once they arrive in the busy waterways.

In the case of the latest calving, however, things could be different.

"Because so much more ice has broken off, (the ice sheet) will produce larger chunks of ice that will come down into the shipping lanes where the oil platforms are," Wohlleben said. "The danger is -- once they get to where the oil platforms are -- if the icebergs are too big then the normal methods used to break up the ice as it approaches the platform will have a lot more difficulties."

The Canadian Ice Service wants to place a satellite beacon on the main sheet as soon as possible to monitor the drifting ice and, if necessary, warn ships and oil platforms in its path.

It will take a while, however, for any real threat to emerge. It could take more than a year for ice from the sheet to appear in the North Atlantic, Wohlleben said.

Greenland -- the world's largest island -- is known for its dense ice cap, which can be up to 1.2 miles thick. During the past months, scientists have warned that Greenland's ice is melting at an accelerated pace. They say climate change is one of several factors responsible for the ice loss.

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