Walls have kept humans safe for centuries, and now they may serve as a way to slow rising sea levels.
At least that's the suggestion from a study published in the journal Cryosphere, from the European Geosciences Union. The scientists say a series of geoengineered walls on the seafloor could reduce the flow of warming waters to undersea glaciers, thus slowing the melting of the glaciers.
It wouldn't solve the problem of disintegrating glaciers or sea level rise, but it could help buy us some time while we continue our efforts to reduce our carbon emissions.
The great glacier wall
Combating climate change and its effects through nature is a process called geoengineering. Such projects, like cloud seeding, seek to influence the climate on a large scale. The walls proposed by study authors Michael Wolovick of Princeton University and John Moore at Beijing Normal University in China, are an example of geoengineering on a more targeted scale to prevent glacier collapse.
"We were imagining very simple structures, simply piles of sand or gravel on the ocean floor," Wolovick said in a statement.
It sounds simple, but the walls would shore up a complex system of ocean floor and warm water flows to keep the glaciers from melting. A natural barrier on the sea floor and the glacier's own ice shelf helps to keep warm water from reaching the glacier itself. However, that warm water can flow down certain slopes, melting the ice sheet at its base and, eventually, working its warmth on the glacier.
The walls of sand or gravel suggested by the researchers would do the same thing as the natural barrier: Anchor the ice shelf. The ice shelf would ground itself along the wall, like it does with a naturally occurring barrier. Without access to the base of the ice shelf, the warm water wouldn't cause the shelf to retreat or reduce the glacier's mass by melting it.
The researchers' simple design involves mounds of the material roughly 300 meters (984 feet) using between 0.1 and 1.5 cubic kilometers of aggregate, depending on the strength of the material. This is similar to the amount of material excavated to build the Suez Canal in Egypt (1 cubic kilometer) or in Dubai's Palm Islands (0.3 cubic kilometers).
To test these walls, Moore and Wolovick ran computer simulations to test what the walls' impact would be on Antarctica's Thwaites glacier, one of the largest glaciers in the world at between 80 and 100 kilometers (50 to 62 miles) wide. This particular glacier is melting fast, and, according to Wolovick, it "could easily trigger a runaway [West Antarctic] ice sheet collapse that would ultimately raise global sea level by about 3 meters."
The models suggest that even their simple design of columns of rock and sand has a 30 percent chance of preventing such a runaway collapse for the foreseeable future. The walls also increase the possibility of allowing the ice sheet to regain lost mass.
"The most important result [of our study] is that a meaningful ice sheet intervention is broadly within the order of magnitude of plausible human achievements," Wolovick said.
A more complicated design, one that would be difficult to achieve given the harsh conditions of the ocean floor, would create a 70 percent chance of blocking 50 percent of the flow of warm water to the ice sheet, according to the models.
Don't start collecting sand yet
Despite the success of the models, Wolovick and Moore aren't recommending we get to work on these walls any time soon. Even the simple mounds would require significant engineering to work in the ocean. Their goal was to prove that this idea was feasible and to encourage others to improve on their designs.
"We all understand that we have an urgent professional obligation to determine how much sea level rise society should expect, and how fast that sea level rise is likely to come. However, we would argue that there is also an obligation to try to come up with ways that society could protect itself against a rapid ice-sheet collapse," Wolovick said.
To that end, both researchers maintain that reducing greenhouse gas emissions is the priority when it comes to combating climate change, in part because reducing such emissions has benefits beyond just saving glaciers from underneath. It would also reduce rising ambient temperatures that could melt the glaciers from above, too.
"The more carbon we emit, the less likely it becomes that the ice sheets will survive in the long term at anything close to their present volume," Wolovick concluded.