How a massive wall in Antarctica could keep sea-level rise

Thwaites Glacier acts as a giant cork that holds back the West Antarctic ice sheet.

(NASA/James Yungel)

Glaciers are mighty rivers of ice, which can carry boulders on their backs and gravel valleys in the rugged mountain ranges. But now, scientists say that the human being might need to think about trying to solve these formidable forces of nature.

Based glaciers in the Arctic and Antarctic perhaps the most targeted — and, surprisingly enough, the cheapest way to slow the rise of the sea level in a warming world, according to a new paper in the journal Cryosphere. A seawall, or even just a series of artificial mountains for the glacier to sit against could hold unimaginable quantities of meltwater, the research suggests.

In contrast to building seawalls and dikes on the coasts of the world, engineering glaciers could slow rise of the sea level at the source, leveling the playing field between the rich countries and the poorer countries. [Images: Greenland’s Gorgeous Glaciers]

But the idea of engineering glaciers leaves some scientists uncomfortable, especially because of the potential for unintended side-effects. Talk of geo-engineering may also be the public a false sense of security, said Valentina Roberta Barletta, a post-doctoral researcher, who study ice-sheet dynamics at the Technical University of Denmark.

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“As a theoretical exercise, it’s okay, it’s good,” Barletta, who was not involved in the current study, told Science. But, she said, “play with the public opinion about this kind of stuff, it can be a little dangerous.”

Runaway melting

The authors of the new paper certainly do not intend their research to be taken as an excuse to shrug off the effects of the emissions of greenhouse gases. For one thing, said study co-author Michael Wolovick, a postdoctoral researcher at the university of Princeton University, try to slow down the flow of glaciers, does nothing to stanch the other catastrophes of climate change, the acidification of the ocean for drought and floods to the inevitable sea level rise that is not because of the melting of the ice, but from seawater expanding as it gets warmer.

But glaciers are no small potatoes, as far as the climate change. Unfortunately for humanity, the Antarctic ice sheet is what is called “overdeepened.” The edges are pressed against the seabed that is shallower than it is in the middle. If you travel from the edge of the ice cap to the centre, the sea floor would slope away from under you. The point where the ice transitions to be anchored on the country is called the grounding line.

Antarctica’s glaciers are the bridge between the ice shelf and the ocean. As the temperatures rise and the glaciers melt, their grounding lines retreat and the seabed they are retreating to is deeper than where they started. This means that the ice has the tendency to start floating, like an ice cube in a glass, says John Moore, a professor of climate change at the University of Lapland and the chief scientist at the College of Global Change and Earth System Science at Beijing Normal University. And floating ice is more likely to melt than grounded ice.

It is a positive feedback system: The more the ice melts, the more likely it is to melt even more. If this ‘marine ice sheet instability” on the way, and some scientists think it is, even if all carbon emissions came to an abrupt stop, the ice would still be gone, Moore said.

“You think, ‘Well, we wave goodbye to the ice cap, or are there really no alternatives?'” he said.

The stop of the glaciers

Waving is a bad option. Even a sea level rise of 3.9 feet (1.2 meters) in the next century could swamp coasts and create a million climate refugees per year, the researchers wrote. A few hundred million people would likely have to temporarily relocate each year, on the flight to flooding. A 2014 study in the journal Proceedings of the National Academy of Sciences estimates that the protection of the coasts all over the world, the costs will be between $12 billion and $71 billion per year.

The outlet glaciers and ice streams that dump all of these meltwater in the sea are relatively small compared with that coastline, Wolovick and Moore said.

“The ice streams and outlet glaciers are very high leverage points in the climate system,” Wolovick said.

The researchers used a very simple computer model to find out whether engineering of the glaciers would even be possible. They are considered to be two possible solutions: First, they can build a submarine wall that would keep hot water from near the base of the ice, where it do the most damage; second, they could make a series of small artificial mounds, which would catch against the glacier, which, grinding, or stop to hover. These structures are built with a dirt and rock, or from near the sea, or maybe broken into of elsewhere. [Images of Melt: Earth’s Vanishing Ice]

Because there are a lot of questions about how glaciers calving off icebergs and how they slide against the bedrock, the researchers ran several scenarios, the change of these variables. They chose Antarctica’s Thwaites Glacier as a test case because it is a huge “cork” holding back the West Antarctic ice sheet.

“Thwaites Glacier is the largest, the most difficult,” Moore said. “If it works at Thwaites, really what we’re saying is that other, smaller glaciers should be easy.”

In 100 percent of the scenarios, a seawall that blocked all the hot water from circulating in the neighbourhood of the glacier kept Thwaites collapse, the researchers found. A seawall that blocked half of the warm water worked 70 percent of the time. In a heartening find, just studding the sea with mountains to grind up the glacier, without blocking the water completely worked 50% of the time.

Unimaginable solutions

The scenarios used in the research were very simplified, Barletta said. In the real Antarctica, there would be many more potential feedback loops to take into account in the model. Her research has found, for example, that the sea floor itself may pop up as the glaciers retreat, the relief of the weight of pushing the base down. In the short term, at least, the rising sea floor could have its own grounding point for the retreating glaciers.

“It is quite easy to see that [geoengineering] could have a number of other effects other than the stop of a glacier,” Barletta said. “If you think that all of this thermal energy that is stopped, where is it going? Another glacier? Is the change of the ocean current? What is there to do? We know nothing about.”

Although it might seem that scientists are more focused on Antarctica and the Arctic than ever before, there is actually less of the infrastructure on the poles now than at the height of the Cold War, when the military considered them strategically valuable, Moore said. Nations need to open their checkbooks again to advance research on how ice sheet, collapse of the work, ” he said. Should East Antarctica ice collapse, the world would be a sea level rise of 11 feet (3.4 m). West Antarctica contains enough ice to send the sea level up to 62 feet (19 m). (Scientists do not expect these levels to 2200 or 2300 even in the worst-case climate-change scenarios.)

“Certainly, much of the knowledge that we need in order to be able to do this kind of work is what we need, even if we choose not to do this kind of work,” Moore said.

A scheme such as the researchers examined in the new study would be best tested on a small glacier in Greenland first, Moore said.

This is not the first glacial geo-engineering, arrangement, Wolovick said. Other possibilities include huge sea water pumps arrangements that would pull water from the ocean and put it on top of the ice caps to re-freeze. Some scientists have suggested drying schemes to try to remove seawater under the base of grounded ice, Wolovick said, or attempts to thicken the sea ice in front of glacial outlets to reduce how quickly icebergs calving. But it will be decades if not a century, before geo-engineering, glaciers is technically feasible, he said.

Although these ideas do not negate the need to get carbon emissions under control, they represent a more sophisticated approach to geo-engineering, Moore said. Rather than trying to change the whole atmosphere for the cooling of the globe, geoengineers can find, small, but with a high value, targets. As for the concern about the conscious change of the planet? That ship has sailed, Moore said.

“We do the climate of the Earth,” he said. “We need to take responsibility for it.”

Original article on Live Science.

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