Massive walls could stop the melting of thawed ice sheets from Antarctica

It would be better for humanity that the huge layers of ice that cover the Antarctic have remained in place. But, as more and more evidence shows that the planet is warming, these sprawling glaciers could seep into the ocean at an accelerating rate, raising sea levels, not in feet but in yards.

To stop the melting ice, some scientists have now proposed an ambitious geoengineering plan: the construction of massive submarine walls to maintain the ice of Antarctica.

As the Earth's temperature continues to rise due to global warming caused by man, it is still not clear how quickly the ice caps could collapse, but the melting of these glaciers is already in progress.

"The big goal would be to slow down or reverse a collapse of the ice cap," Michael Wolovick, a geoscientist at Princeton University and co-author of the geoengineering study released Thursday. The cryosphere, said in an interview.

An uncontrollable flow of ice into the ocean is not considered an immediate threat this decade or the next, but it could very well be either the end of the century or potentially earlier.

"I do not think that kind of thing should be implemented anytime soon," said Wolovick. "But I think we should be concerned about what will happen to humanity beyond 2100."

A particularly worrying glacier is the Thwaites, located in West Antarctica.

"If Thwaites were to collapse, it would take all of Western Antarctica with it," said Wolovick, which means a possible rise in sea level of 3 meters, almost 10 feet.

However, this glacier is already melting at an accelerated rate.

"It's definitely going downhill," said Josh Willis, a NASA oceanographer who studies ice caps and glaciers. "There is a lot of ice there and a lot of potential sea level rise."

"The uncertainty is how fast this is going to go," added Willis, who was not involved in the study.

The walls

The Wolovick study offers two ideas, one or the other being massive infrastructure projects – some of the largest ever attempted.

The researchers used the Thwaites Vulnerable Glacier as a model and performed computer simulations to show how artificial structures could prevent it from flowing freely into the sea.

"The designs are simple," said Wolovick. "It's basically a big pile of land."

The first idea is to build piles of gravel or isolated aggregates 300 meters (nearly 1,000 feet) below the part of the glacier that floats over the ocean, known as the ice platform. .

Submerged submerged mounds would catch ice as it sank, allowing the ice cap to "recast" on this artificial land.

Naturally, the ice shelves – the front of the glacier that floats over the ocean – act like traffic jams. But if they collapse, there is no plug.

Image: Wolovick & Moore, The cryosphere, 2018

So, these great mounds do the business.

Just how much aggregate or "dirt" would that require? The researchers found that the project would require between 0.1 and 1.5 cubic kilometers.

According to Wolovick, when engineers excavated the Suez Canal in the 1860s, one of the largest civil engineering projects in history, they removed about 1 cubic kilometer of land.

For the second idea, the researchers proposed to build a long continuous wall, or threshold, rather than building massive mounds. This option would probably be more successful, said Wolovick, because the wall would not only allow the glacier to "recompose itself", but would also prevent relatively warm ocean waters from infiltrating the glacier and gnawing at the glacier. low.

Image: The National Snow and Ice Data Center

Hot water is a big threat. More than 90% of the heat accumulated on Earth is absorbed by the Earth's oceans. And these relatively warmer waters in the polar regions – even though they are still cold compared to temperate oceans – have already begun to thin the glaciers.

A small wall could block about 50% of these hot water currents, the researchers found. A bigger wall would be even more effective.

And over time, engineers may develop better ways of blocking water or building more advanced structures, rather than simply dropping masses of soil or aggregates on the seabed. .

"It might be possible to do something smarter," noted Wolovick.

It's not only expensive – it might not work

The geoengineering of the planet – especially the ocean – is widely recognized as an extremely difficult endeavor.

"It's tough, it's expensive, and it might not work," Willis said.

And if nations decide to regroup and dump rock masses under the collapsed Antarctic glaciers, warming up could still thaw the ice.

"Even if you build that wall to protect that ice from the ocean, it can still melt the atmosphere," Willis said. "You can slow it down, but you do not stop it."

For this reason, Wolovick emphasizes that weaning greenhouse gases is the essential solution, not glacial geoengineering.

"Ice engineering is not a substitute for carbon emission reductions," he said.

Also, even if the giant walls were working – and the glaciers stopped in their tracks – that would not stop heat waves, drought and storms from carrying a lot more water, Wolovick noted.

Climate change, said Willis, is a global reality that will require a global response.

"The magnitude of climate change is the entire planet," he said. "Trying to put these bandages is a precarious solution."