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Polar ice tipping points

Irene Quaile, Deutsche Welle
Petty Officer 2nd Class Mariana O'Leary / USCG

As I get ready to head up to Tromso for the Arctic Frontiers conference and prepare my accreditation for the next routine round of climate talks here in Bonn in March, I find myself with plenty of food for thought.

It seems like not that long ago that scientists were telling us that although the Arctic is clearly melting fast, there was no need to worry about the Antarctic ice melting. But for the past 15 years or so, scientists have been observing that glaciers in West Antarctica are out of balance. Ice shelves have been breaking off and the calving fronts of glaciers have been retreating, draining huge amounts of ice into the ocean. This week I was interested and concerned to read about the results of a modeling effort, using three different types of model, indicating a key Antarctic glacier was melting irreversibly.

The Pine Island Glacier in the Antarctic hit the headlines last year when a giant iceberg broke off it. It is a key glacier because it is actually responsible for some 20 percent of the total ice loss from the region. Now scientists have found the glacier is melting irreversibly – with dramatic consequences for global sea levels. For an article for Deutsche Welle entitled "Antarctic’s glacier retreat unstoppable," I interviewed Gael Durand of the French University of Grenoble, one of a team of scientists who have just published the new study:

“We show that the Pine Island Glacier will continue to retreat and that this retreat is self-sustaining. That means it is no longer dictated by changes in the ocean or the atmosphere, but is an internal, dynamic process,” Durand told me. This will mean an increasing discharge of ice and a greater contribution to global sea level rise. “It was estimated at around 20 gigatons per year during the last decade, and that will probably increase by a factor of three or five in the coming decade. That means this glacier alone should contribute to the sea level by 3.5 to 10 millimeters (0.14 to 0.39 inches) a year, accumulating to up to one centimeter (.39 inches) sea rise over the next 20 years. For one glacier, that is colossal," says Durand.

The last report by the Intergovernmental Panel on Climate Change warned of the implications if the glaciers of West Antarctica were to become unstable. “Here,” says Durand, “we have proof that that is already happening with this one.”

At the Arctic Frontiers conference two years back, I heard a lot of interesting discussions about climate tipping points. Professor Carlos Duarte, director of the Oceans Institute at the University of Western Australia and research professor with the Spanish National Research Council, talked to me at length about tipping points. Let me quote him briefly:

“Tipping Points – or thresholds – are levels of pressures beyond which small response of a property of interest becomes abrupt. Once a system or ecosystem or earth system crosses beyond a threshold, the changes, e.g. in the extent of ice or rate of warming, accelerate greatly, and once the threshold is crossed, it is sometimes very difficult to return to the original state even if pressure is released or reduced.”

We discussed the possible tipping points and warning signs outlined in a key piece of research by Timothy Lenton and others. Some would argue that tipping points have already been crossed in the Arctic region, which is known to be warming at least twice as fast as the rest of the earth. One of Lenton’s other key factors is the West Antarctic ice sheet becoming unstable. Now the “eternal ice” down south could be reaching a kind of “tipping point” in places. Yes, I know this only applies to a particular region of the West Antarctic, but the implications of irreversible glacier melt there are already huge. Greenland and that West Antarctic ice sheet play a key role in storing masses of fresh water, which would have huge implications if they melted. With marine glaciers, like the Pine Island Glaciers, the melt of white ice to expose more dark ocean surface underneath would further increase warming by absorbing solar heat instead of reflecting it back.

With the European Union in the news today for considering moving away from binding climate targets, and little progress in sight towards an effective new climate agreement scheduled to be agreed in Paris in 2015, this all puts me in a pensive mood, as I get ready to head north and focus on the implications of the changing climate for “Humans in the Arctic.”

This story is posted on Alaska Dispatch as part of Eye on the Arctic, a collaborative partnership between public and private circumpolar media organizations.

Irene Quaile works as a journalist for Deutsche Welle, Germany's international broadcaster.

This commentary is posted on Alaska Dispatch as part of Eye on the Arctic, a collaborative partnership between public and private circumpolar media organizations.

The views expressed here are the writer's own and are not necessarily endorsed by Alaska Dispatch, which welcomes a broad range of viewpoints. To submit a piece for consideration, e-mail commentary(at)alaskadispatch.com.