Each year, the Thwaites Glacier–a massive chunk of ice roughly the size of Florida that sits on the western edge of Antarctica–shrinks back thousands of feet as it melts, pushing sea levels higher. The glacier could eventually completely collapse, even if humans stopped pumping greenhouse gases into the atmosphere now. If the entire West Antarctic Ice Sheet collapsed, global sea levels could rise as much as 15 feet, and create catastrophic conditions in coastal areas.
A new study looks at a potential intervention: Could a long underwater wall help prevent the glacier’s collapse, or at least slow it down? Researchers studied two general designs. In one case, a long pile of sand and aggregate would stretch along the ocean floor in front of glaciers, helping prevent warming ocean water from hitting the base of ice and melting it. (Surface water is colder, and less of a problem for glaciers in Antarctica now.) In another design, 984-feet-high mounds or columns on the sea floor wouldn’t form a complete wall, but could help buttress the glacier and resist the flow of ice.
The modeling in the study–which is very preliminary–suggests that both approaches might work. In many experiments, the glacier the researchers modeled collapsed in around 150 years without an intervention. With a massive wall, it could potentially last at least 1,000 years (the models only looked 1,000 years into the future). A smaller wall that blocked only about half of the warm water could give the glacier a 70% chance of lasting that long. The isolated mounds could give it a 30% chance.
The study isn’t advocating for the walls to be built. But the researchers wanted to begin a conversation in the scientific community and offer up a model that other researchers could improve on, potentially leading to a plan that could eventually be implemented.
Even the simplest design would probably be the largest civil engineering project ever attempted. Still, “it’s plausibly within the order of magnitude of human achievements,” says Michael Wolovick, one of the study’s authors, who worked on the modeling as a postdoc at Princeton University.
The project might use as much aggregate as the massive palm-shaped artificial islands built off the coast of Dubai, or Hong Kong International Airport, which was also built on an artificial island. The cost could conceivably be in a similar range, perhaps $10 to $100 billion dollars. But if it worked, it would be less expensive than the changes needed to protect the world’s cities from sea level rise–and certainly less than the cost of allowing climate change to proceed unchecked.
“[Some] models say that society would end up spending several tens of billions of dollars every year around the world on traditional coastal protection,” says Wolovick. “So addressing the problem at the source might actually be a cost-effective response in comparison.”
The idea is not in any way a replacement for cutting emissions. “Even perfect glacial geo-engineering would do nothing about ocean acidification and droughts and floods and heat waves and extreme weather and all the rest of it,” he says. As the atmosphere warms, melting more water on the surface of the glaciers, the intervention would also be more likely to fail. A warmer climate would also make other parts of Antarctica vulnerable, so more interventions would be needed. And the long-term future of ice sheets will depend on cumulative CO2 emissions.
“In the long run–I’m talking sort of a 1,000-year timescale–if humanity doesn’t get emissions under control, then the only viable goal of glacial geo-engineering would be to manage the collapse and try to make it a slow collapse instead of a fast collapse,” says Wolovick. “We would not be able to prevent an ice sheet collapse in the long run if humanity doesn’t get emissions under control.”