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Collapse of the ice titans

Monitoring Greenland's melting glaciers from a 15-metre long sailboat.

In early August, a 260-kilometre-square chunk of ice broke off the Petermann Glacier — the largest iceberg to calve in the Arctic Ocean since 1962.

Richard Bates. Credit: Richard Bates

The collapse didn't surprise Richard Bates, a geophysicist from the University of St Andrews, UK. During a visit to Petermann last summer, with glaciologists Jason Box of the Byrd Polar Research Center at Ohio State University in Columbus and Alun Hubbard of Aberystwyth University, UK, the three noted rifts and meltwater — a sign of pending collapse. They installed time-lapse cameras atop the 900-metre-high cliffs and placed eight Global Positioning System (GPS) units along the glacier's centre line to monitor the event.

The researchers returned to Greenland late last month to retrieve the equipment and make other oceanographic and geophysical measurements, but were thwarted in their attempts to reach Petermann by ice. Nature caught up with Bates soon after he stepped off the Gambo, the sailboat that voyaged to the north end of Humboldt Glacier, which the team is also studying.

What did you see while sailing up the Greenland coast?

We saw a lot of calving glaciers. One 400-metre-long section of the glacier broke off just after we surveyed it. On our way to the Humboldt Glacier we got close to some major calving. It can seem very dangerous to have such a small boat in front of these glaciers, but you can be a lot more reactive and nimble than in large research vessels. But once you're stuck in the ice, you're stuck. We were pushing it a bit last week.

What work did you have planned for this trip?

Greenland's glaciers are breaking up. Credit: Richard Bates

We worked our way up from central Greenland — the Lille, Store and Rink glaciers. We took time-lapse measurements and looked at the submerged portion of the glacier to see how fast the front is changing. We've been finding out that the submarine melt rates can be 20–100 times faster than the above-surface melt rates. We're using a laser scanner to measure the changes above the water and using sonar to look at the melt rates below the water.

What do you see underwater?

We see features that we suspected were there, such as an underwater cave system that represents the end of the drainage network of the glacier. The technology that we're getting together is showing that we can get information that we never had before. As we get the methodology worked out, we'll be able to apply this very quickly and easily elsewhere. We can't predict what is going on with the glaciers without understanding the whole of the ice cap. These techniques could make us less reliant on big research vessels. We've been doing this on small boats and it is a lot cheaper.

Why study the Petermann and Humboldt glaciers?

Petermann is one of Greenland's longest glaciers and Humboldt is one of the widest.

At the Humboldt Glacier we're looking at how quickly things are changing. It makes them both very interesting to study. We're doing time-lapse photography with cameras and taking GPS data, and also oceanic measurements of the warm ocean currents coming up from the south. Why would Petermann break up — particularly this year — in such a large chunk? The ocean-current measurements could provide that answer.

We had wanted to get back to Petermann. The whole point of leaving the equipment was to record the glacier's movement throughout the year. We need to extract it. Not getting there is not going to kill the programme — the data are still sitting there. But it would have been nice to do more oceanic measurements in the Petermann fjord. I suspect we have a big slug of warm water sitting there.

What will that information from the Petermann Glacier add to what you already know?

The Petermann Glacier broke off at pretty much where we thought it would, where the rivers were flowing. The GPS data and the cameras will show the whole process of how it broke up. It will tell us a lot about the mechanics and triggers of the break-up. In the satellite images we can see that it broke off, but where was the greatest strain? What was the trigger? Those are the crucial questions in understanding break-up.


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Greenland ice sheet yields biggest iceberg in decades

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Richard Bates

Jason Box

Meltfactor blog

Alun Hubbard

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Hoag, H. Collapse of the ice titans. Nature (2010).

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