Greenland Glacier Breakup Suggests Imminent Disintegration

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New satellite images reveal that a massive ice chunk recently broken away from one of Greenland's glaciers, which researchers say will continue to disintegrate within the next year.

Scientists at Ohio State University monitoring daily NASA satellite images of Greenland's glaciers discovered that an 11-square-mile (29-square-kilometer) piece of the Petermann Glacier broke away between July 10 and 24. The chunk was about half the size of Manhattan.

They announced their finding today.

Glaciers are large, slow-moving rivers of ice, formed at the poles and in alpine regions by layers of compacted snow. The Petermann Glacier is one of the approximately 130 glaciers that flow out of the Greenland ice sheet and into the sea, where large chunks of ice fall off, or calve, to form icebergs.

The Petermann Glacier has a floating section of ice about 10 miles (16 km) wide and 50 miles (80 km) long —an area of about 500 square miles (1,295 square km).

The last major ice loss to the glacier occurred when 33 square miles (86 square km) of floating ice fell off between 2000 and 2001.

More ice loss has been occurring in recent years as temperatures in the Arctic rise along with global warming. The amount of ice that melted from Greenland in 2007 could have covered an area the size of the United States twice, researchers said last year.

Researchers also noticed what appears to be a massive crack in the glacier that could signal an imminent and much larger breakup.

"If the Petermann Glacier breaks up back to the upstream rift, the loss would be as much as 60 square miles (160 square km)," said OSU researcher Jason Box. That loss would represent one-third of the massive ice field.

Another of Greenland's glaciers, the Jakobshavn isbrae, has retreated inland further than it has at any time in the past 150 years of observations. Researchers think this is the furthest the glacier has retreated in the last 4,000 to 6,000 years.

The Jakobshavn is one of the largest of Greenland's glaciers and is responsible for producing at least one-tenth of the icebergs that calve off into the sea from Greenland.

The northern branch of the Jakobshavn broke up in the past several weeks and it has lost at least 3 square miles (10 square km) of ice since the end of the last melt season.

Between 2001 and 2005, a massive breakup of the Jakobshavn erased 36 square miles (94 square km) from the ice field.

On the other end of the globe, Antarctica's Wilkins Ice Shelf has been hanging on by just a thread as more large pieces of ice broke away from it earlier this summer.

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• Images: Ice of the Antarctic