Global warming could release radioactive waste stored in an abandoned Cold War-era U.S. military camp deep under Greenland’s ice caps if a thaw continues to spread in coming decades, scientists said on Friday.

Camp Century was built in northwest Greenland in 1959 as part of U.S. research into the feasibility of nuclear missile launch sites in the Arctic, the University of Zurich said in a statement.

Staff left gallons of fuel and an unknown amount of low-level radioactive coolant there when the base shut down in 1967 on the assumption it would be entombed forever, according to the university.

It is all currently about 35 meters (114.83 ft) down. But the part of the ice sheet covering the camp could start to melt by the end of the century on current trends, the scientists added.

“Climate change could remobilize the abandoned hazardous waste believed to be buried forever beneath the Greenland ice sheet,” the university said of findings published this week in the journal Geophysical Research Letters.

The study, led by York University in Canada in collaboration with the University of Zurich, estimated that pollutants in the camp included 200,000 liters (44,000 UK gallons) of diesel fuel and the coolant from a nuclear generator used to produce power.

“It’s a new breed of political challenge we have to think about,” lead author William Colgan, a climate and glacier scientist at York University, said in a statement.

“If the ice melts, the camp’s infrastructure, including any remaining biological, chemical, and radioactive wastes, could re-enter the environment and potentially disrupt nearby ecosystems,” the University of Zurich said.

The study said it would be extremely costly to try to remove any waste now. It recommended waiting “until the ice sheet has melted down to almost expose the wastes before beginning site remediation.”

There was no immediate comment from U.S. authorities.

(Reporting By Alister Doyle; Editing by Andrew Heavens)