In 1960, the United States Army launched a program called "Project Iceworm", a plan to build launch sites for nuclear missiles under the northern Greenland ice sheet, to provide the missiles with closer access to the Soviet Union. To test the feasibility of this concept, the Army established a base called Camp Century, a functioning military site consisting of tunnels and chambers carved directly into the ice. However, the site’s engineers soon found that the glacier that the base was built into isn’t a stable mass of ice, but instead flows at a slow rate, deforming the base’s tunnels. This resulted in Camp Century’s abandonment in 1966.

However, the Army only performed a minimal decommissioning of the base in 1967, assuming that the abandoned equipment and a host of toxic materials left behind would be forever trapped in the ice — swept under the proverbial, and supposedly permanent rug, as it were. Examples of the waste material left behind include nearly a quarter-million liters (63,000 gallons) of sewage, 200,000 liters (53,000 gallons) of diesel fuel, PCBs, construction chemicals, and radioactive coolant fluid.

Unfortunately, all of this material could once again be exposed to the environment, thanks to global warming. A new study released by Liam Colgan, a glaciologist at Canada’s York University, says that glacial melt is expected to outpace the addition of new ice from fresh snowfall in the region by 2090, leading to the eventual release of the toxic material into the local marine environment. But the study also warns that material seeping into the ice could cause contamination long before then.

There is also the question of who is responsible for cleaning up the mess, as Colgan feels that the issue could strain relations between Denmark, Greenland, and the United States. At the time of Camp Century’s construction, Greenland was part of Denmark, and gained partial independence in 1979. “It plays into a discussion about the U.S. and Denmark using Greenland for their own purposes, and then the Greenlandic people have to deal with it afterwards,” remarks Kristian Nielsen, a science historian at Aarhus University in Denmark.

Camp Century is also located about 200 km, (125 miles) from the site of the Thule Air Base broken arrow incident that occurred in 1968, where a B-52 bomber, carrying four nuclear bombs, crashed, releasing radioactive material into the environment.