An ice "island" four times larger than Manhattan and up to 600 feet tall has broken off the world's northernmost glacier, a University of Delaware researcher reports. The chunk of Arctic ice that calved off Greenland's Petermann Glacier is the biggest in almost 50 years.

The icy isle, which broke off early yesterday, is at least 100 square miles and as a thick as "up to half the height of the Empire State Building," according to a university news release.

In mid-July, other scientists on a Greenpeace ship predicted the calving, the Sydney Morning Herald reported last month. They said that, altogether, 500 billion metric tons of ice was set to crumble from the glacier.

"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," said Alun Hubbard, a glaciologist at the University of Wales. There's been a revelation in the last couple of years in the role that warming oceans play in triggering the enhanced acceleration, breakup and thinning of these outlet glaciers."

A National Ice Center scientist writes in The Washington Post that while iceberg creation is a regular occurrence, the newest is unusual for its size, which is more typical of Antarctic icebergs.

Don't worry about running into that new iceberg anytime soon.

"The newly born ice-island may become land-fast, block the channel, or it may break into smaller pieces as it is propelled south by the prevailing ocean currents," said Andreas Muenchow of Delaware's College of Earth, Ocean and Environment. "From there, it will likely follow along the coasts of Baffin Island and Labrador, to reach the Atlantic within the next two years."

Update at 8:34 p.m. ET: Correcting amount of ice expected to slough off the glacier to 1.1 trillion pounds, not tons as initially written after converting from metric tonnes (2,205 pounds/tonne). Thinking one thing, writing another. Ah, Friday ...

Update at 9:08 p.m. ET: Friday math follies continue... Well, it's certainly way more than 1.1 trillion pounds, now that I actually think about it off the clock. How about 11 quadrillion pounds? (11 with 15 zeros)

Converting on the fly is always dangerous. Pass the weekend dunce cap.

(Posted by Michael Winter)