A chunk of ice so big it would cover the island of Manhattan to a depth of 300 metres has broken away from the world’s fastest retreating glacier.

This isn’t the plot to an upcoming end-of-the-world Hollywood blockbuster.

It’s what NASA satellite images showed after 12.5 square kilometres of ice broke off the Jakobshavn glacier in Greenland in mid-August.

Assuming the ice was about 1.4 km deep, that’s a volume of 17.5 cubic kilometres – about the amount it would take to cover the entire island of Manhattan in ice 300 metres thick.

“The calving events of Jakobshavn are becoming more spectacular with time, and I am in awe with the calving speed and retreat rate of this glacier,” said Eric Rignot, a glaciologist at NASA’s Jet Propulsion Laboratory, in a statement.

Ice breaks away from the Jakobshavn every summer. This process, known as calving, has seen the glacier shrink inland by about 600 metres annually in the last few years, NASA said.

But this year could mark “one of the most significant calving events on record,” according to the European Space Agency (ESA), as the new face of the glacier has been pushed inland “to what appears to be its furthest easterly location since monitoring began in the mid-1880s.”

Lev Tarasov, associate professor in the department of Physics and Physical Oceanography at Memorial University, told the Star the drop-off from Jakobshavn is “just another example that glaciers can be a lot more dynamic than most people think of.”

The event, he said, was “like a very big storm.”

“The actual day-to-day rates of break off are controlled more by complexities of cracks in the ice and melting below. There’s a lot of melt at the glacier front where it meets the ocean. If there’s any warm water there . . . you can melt a lot of ice very quickly underneath and that weakens the ice front and can promote very quick calving,” Tarasov said.

The Jakobshavn glacier drains 6.5 per cent of the Greenland ice sheet and produces about 10 per cent of its icebergs. Glaciers in the region have been thinning further inland as Arctic temperatures have gone up, the European Geosciences Union said.

Tarasov explained that scientists cannot directly link glacier calving to a single event, like global warming, but specific factors are driving the phenomenon in Greenland.

This includes warmer ocean water and changing currents bringing that warmer water to the base of the ice sheets. “That seems to be the strongest destabilization component right now for Greenland,” Tarasov said.

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Between 2000 and 2011, Jakobshavn calving caused the sea level to rise by one millimetre, and the glacier has receded more than 40 kilometres between 1850 and 2010.

In the last years, the glacier has also moved at faster speeds than ever before.

NASA estimates that the Jakobshavn glacier could have the largest impact on sea levels than any other feature in the Northern Hemisphere.

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