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Construction Corner: Creating walls to keep glaciers from the sea

Korky Koroluk
Construction Corner: Creating walls to keep glaciers from the sea

For years now, scientists have been telling us that we need to take a global approach to global warming, doing many things instead of looking for a single magic bullet.

But maybe — just maybe — it’s time to take a more focused approach and tackle one particular problem that has emerged in the last decade as perhaps the most important of all, rising sea levels.

It’s that idea that has driven Michael Wolovick, a researcher at Princeton University in New Jersey, to spend the last two years looking for ways to stabilize glaciers in Greenland and Antarctica.

What he has come up with is an idea for building walls to prevent glaciers from reaching the sea. It sounds simple, but when you start thinking about it, it becomes more complex by the minute.

Wolovick presented his work in December at the annual meeting of the American Geophysical Union. Since then, articles about it have appeared on the websites of the Earth Institute at Columbia University and The Atlantic.

In those articles, Wolovick makes clear his is not a concrete proposal. Instead, he says it’s a “promising idea” for further research.

Wolovick is suggesting the construction of what he calls “sills,” which would be large piles of material sitting on the seafloor across the face of glaciers that flow into the sea.

“It’s nothing particularly technologically advanced,” he says. “I’m imagining something like a big pile of sand or other loose aggregate and maybe an outer layer of boulders to protect against tides.”

But Wolovick is a glaciologist, not an engineer.

Engineers who have looked at his work tell us there would be nothing simple about the idea if it ever became an actual project.

The sills —walls — would need to be well protected. That protection might take the form of boulders and concrete elements or additional sills built in front of, or at an angle to, the main sill in order to redirect currents that might compromise its effectiveness.

The work would, of course, be done underwater, perhaps under a floating layer of ice. Little is known about the seafloor in those areas, but it could be unstable and soft in places. All those factors would be added to what already would be a mega-engineering project.

The problem arose because glaciers that extend from land into the ocean are exposed to both warming air and water. That relatively warm seawater melts glaciers from below in addition to the melting that occurs from the air above. That thawing thins the ice until it breaks free and floats away.

That in itself does not contribute to sea-level rise since the shelves were already floating. But when they break, they clear the way for more ice to flow into the sea.

In the Antarctic, geology is important. The West Antarctica Ice Sheet is grounded on bedrock that is below sea level and slopes towards the centre of the continent.

That means glaciers store most of the water close to their centres since that’s where they’re tallest. This creates a sort of runaway mechanism.

For each metre that the ice recedes, it introduces more water to the ocean than the previous metre did. At the same time as the glacier retreats, the tremendous weight of the glacial flow would still push it forward toward the ocean.

Collapse, when it comes, is likely to be abrupt and would send global sea levels up by more than four metres. That would flood land that is presently home to 153 million people, many of them in North America.

For now, Wolovick’s idea is a thought experiment, not a project, not even a proposal. But it is important because it provides us with an idea of the sort of engineering work that will become necessary if we continue our indifference in the face of our warming world.

Korky Koroluk is an Ottawa-based freelance writer. Send comments to editor@journalofcommerce.com.

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