Enormous ice shelf snaps off in Arctic

An ancient ice shelf has cracked off northern Ellesmere Island, creating an enormous, 66- square-kilometre ice island and leaving a trail of icy blocks in its wake.
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It broke up 16 months ago, but no one was present to see it. The scientists say they are only now releasing details after piecing together what occurred using seismic monitors and Canadian and U.S. satellites.
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"If you were standing right on the edge of the shelf, there'd have been this huge 15-kilometre crack as far as you could see in both directions," said Mr. Copland.

"And then the ice drifted off." Within an hour, the giant ice island was a kilometre offshore. It travelled west about 50 kilometres over the next few weeks, and then moved east before freezing into the sea ice about 15 kilometres offshore.

The ice island is about 37 metres thick and measures roughly 15 kilometres by five kilometres. That's the size of a small city, or larger than 11,000 football fields.

The island is now stuck in the winter ice, but the researchers believe it is just a matter of time before it is freed and floats away. They say the ice island could become a potential hazard to navigation and oil and gas extraction if it sails south towards the Beaufort Sea.

Two new series of radiocarbon age determinations form the basis for this paper. The first series shows that both the outer east coast of Ellesmere Island (north to latitude 78 degrees 36 prime) and much of Makinson Inlet were free of glacier ice prior to 9000 radiocarbon years ago (dates uncorrected for the apparent age of sea water). However, on the basis of the available data the head of the north arm of Makinson Inlet, north of the present site of Split Lake, was not invaded by a marine fauna until about 2000 years later, presumably because of the persistence of glacier ice in this trough. The second series of age determinations relates to fluctuations of outlet glaciers during Holocene time. Dates of 5180+-260 years (GSC-2909) and 2590+-150 years (GSC-3191) for the bottom and top, respectively, of a massive peat deposit bracket a period during which outlet glacier 7A-45, north of the head of Makinson Inlet, was smaller than it is at present. Data from several sites suggest an advance of glaciers about 1000 years ago, and a second advance, during the last 100 years or so, is recorded at the margins of a number of glaciers draining the ice caps in central and southeastern Ellesmere Island.

Copland and colleagues concluded that
the disintegration was caused by several factors,
mostly related to global warming...

"...We are crossing climate thresholds, and these may signal the onset of
accelerated change ahead," Vincent said Thursday.

"What surprised us was how quickly it happened," Copland said. "It's pretty alarming. Even 10 years ago scientists assumed that when global warming changes occur that it would happen gradually so that perhaps we expected these ice shelves just to melt away quite slowly, but the big surprise is that for one they are going, but secondly that when they do go, they just go suddenly, it's all at once, in a span of an hour."

"There's significant oil and gas development in this region as well..."