Massive balloons help polar scientists build underground tunnels

In 1967, the United States abandoned a top-secret military base in Greenland because its underground tunnels were caving in under the weight of the ice. It’s a problem familiar to scientists who work in some of the world’s coldest and most remote regions, who must also deal with limited infrastructure and a lack of building materials. Now, arctic researchers have devised a creative solution: inflating giant balloons under the snow to form surprisingly strong—and environmentally friendly—cylindrical tunnels.

The technique works like making a hot dog, says the method’s pioneer, Jørgen Peder Steffensen, a physicist at the University of Copenhagen. “Using snowblowers we cut a trench—that’s the bun,” says Steffensen, who also heads logistics for the East Greenland Ice-core Project (EastGRIP), a research effort focused on understanding the history of the ice sheet. “The balloon is the shape of a giant hot dog, and we inflate it in place below the surface. Then we throw snow back on top”—the condiments, in this analogy—“and the snow hardens on top of that.” Days later, the balloons are deflated and taken away, leaving behind tunnels that provide shelter, workshops, or storage for scientists.

In the past, polar engineers in Greenland and Antarctica used flat wooden beams or curved aluminum shoring to create ceilings above icy walls and floors. Snow would accumulate above and harden. But over time, the ice would deform and contract, leading to sagging ceilings and narrowing walls that could eventually close completely. That’s what happened at the secret U.S. base, known as Camp Century.

The balloon technique has shown several advantages over the conventional method, Steffensen says. First, because of the inherent strength of arches, the cylindrical tunnels contract slightly more slowly than the rectangularly shored ceilings. In one test tunnel formed by a balloon, engineers measured a 25-centimeter-per-year contraction versus a 27-centimeter-per-year contraction for a traditional trench.

And any contraction can be more easily managed in the cylindrical tunnels. Without shoring in the way, team members can cut encroaching walls away with saws to rewiden rooms, without risk of collapse. There’s also an environmental advantage: The metal or wood required for the old technique requires fuel-intensive cargo plane flights, and is many times heavier than the balloons. After ceilings deform, the shoring material generally cannot be retrieved from the ice subsurface, and so researchers must leave it behind.

Steffensen first tried the technique in 2012 on another Greenland base. Last summer, he led the team that built the full tunnel system at EastGRIP, deploying a total of eight balloons. The biggest balloon is 40 meters long, but several can be placed end-to-end to make longer tunnels. After initial drilling tests last summer, this summer’s drilling has fully begun with the tunnels providing consistently cool temperatures. “This is good news for the ice cores, as we would like them to stay as cold as possible,” Steffensen says.

Polar engineers are interested in adopting the technique elsewhere. Engineer Vincenzo Cincotti, who leads logistics for an Italian team at the Concordia Research Station in Antarctica, has purchased two balloons to test making storage facilities next Antarctic summer. Though he believes that the balloon technique will be cheaper than shipping metal or wood, he is eager to know if the drier and colder conditions in Antarctica will affect how the snow hardens to form the icy roofs of the tunnels. “If it works, you can make as many shelters as you need with the balloons,” he says.