The City Under the Ice: How a Secret Cold War Base Ended Up Rewriting Greenland’s Past

In April 2024, a NASA Gulfstream III flew east from Pituffik Space Base in northern Greenland with an unusual radar strapped to its belly. The team aboard was testing whether the instrument could see through the ice sheet to the bedrock more than a mile below. About 150 miles out, over a stretch of ice so flat and white it looks like the edge of the world, something lit up in the data that was not rock at all. It was a grid of straight lines and boxes, buried about 100 feet down.

“We were looking for the bed of the ice and out pops Camp Century,” said Alex Gardner, a cryospheric scientist at NASA’s Jet Propulsion Laboratory who helped lead the project. “We didn’t know what it was at first.”

What they had found was a town. Sixty-five years earlier, the U.S. Army had carved a small city into the Greenland ice sheet, with streets, bunk rooms, a chapel, a theater and its own nuclear power plant. The Army called it a research station. In secret, it was the first step toward hiding hundreds of nuclear missiles under the ice. The missiles never came, the ice swallowed the town, and the most valuable thing the soldiers left behind turned out to be a long tube of ice and a few jars of mud that sat forgotten in freezers for half a century.

A city cut out of snow

The site was chosen in May 1959, about 138 miles inland from the ice-sheet edge near Thule Air Base, more than a mile above sea level. Winter temperatures there fall below minus 60 degrees Fahrenheit and storms can blow at well over 100 miles an hour. Building on the surface made little sense. Snow drifts bury anything that stands up. So the Army Polar Research and Development Center decided to build down.

The method was called cut-and-cover. Swiss-made rotary snow millers known as Peter plows chewed long, deep trenches into the snowpack and blew the snow out in a high plume. Crews then set curved steel arches over each trench, and the Peter plows sprayed more snow on top, where it hardened into a roof. Inside the finished tunnels, prefabricated wooden buildings sat on timber foundations, with air gaps all around them so their warmth would not melt the walls.

By October 1960 Camp Century had 21 trenches with a total length of nearly two miles. The longest, called Main Street, ran about 1,100 feet. The camp had a hospital, a mess hall, a laundry, a barbershop, a library, a recreation hall that doubled as a theater, and a chapel. Fresh water came from a well that an Army research engineer named Raul Rodriguez devised: steam was piped deep into the snow to melt an underground pool, which was then pumped up as needed. Sewage went into a pit dug in the ice.

Camp Century was not a secret. The Army wanted the world to see it. The Saturday Evening Post profiled it in 1960. National Geographic ran a cutaway diagram. The Boy Scouts of America and Danish scouting each sent a teenager to spend the 1960 winter season there as a junior scientific aide: Kent Goering, a 17-year-old Eagle Scout from Neodesha, Kansas, and Søren Gregersen from Denmark. The Army even made a film about the camp for its television series The Big Picture.

A nuclear reactor in kit form

The showpiece was the power plant. In January 1959 the Army hired the American Locomotive Company, better known for building trains, to design a nuclear reactor that could be flown or hauled to a remote site, bolted together, run, and taken away again. The result was the PM-2A, for “portable, medium power.” It traveled to Greenland on ten skids and in 18 crates, each sized to fit a cargo plane, with every pipe and cable ending in a flanged joint or plug.

Tractors dragged the parts across the ice on sled trains that crawled along at a couple of miles an hour. Assembly in the reactor trench took about ten weeks, and at 6:52 a.m. on October 2, 1960, the reactor went critical for the first time. On November 12 it began making electricity. Its core held fuel enriched to 93 percent uranium-235, and it delivered about 1.5 megawatts to the camp, plus steam for the water well. A diesel plant of the same size would have burned well over a million liters of fuel a year, every drop of it hauled across the ice.

The reactor ran for 33 months, with one early scare. In January 1961 an explosion at the SL-1, an Army test reactor in Idaho, killed its three operators. The PM-2A shared a key design feature with SL-1, a central control rod that could start the reactor on its own if it was pulled out too far, so the Atomic Energy Commission held up its restart until an interlock was fitted. After that it ran well, including one stretch of more than 2,500 hours without a break through the winter of 1962 and 1963.

The secret under the cover story

Officially, Camp Century existed to test Arctic construction, try out the portable reactor and support science on the ice cap. That is what the United States told Denmark, which governs Greenland. The full plan was far larger, and Denmark was never told.

In 1960 an Army study titled “Strategic Value of the Greenland Icecap” laid out Project Iceworm. The Army proposed digging about 2,500 miles of tunnels under the ice and spreading up to 600 nuclear missiles through them, spaced four miles apart, over an area of 52,000 square miles, roughly three times the size of Denmark. The missiles would be a shortened, two-stage version of the Air Force’s Minuteman, which the Army planned to call the Iceman. They would be moved around the tunnel network so that the Soviet Union could never be sure where they were. “The missile force is hidden and elusive,” the study said.

The plan rested on a deliberately vague diplomatic note. In November 1957, when the U.S. ambassador raised the storage of nuclear weapons in Greenland, Danish Prime Minister H. C. Hansen replied that since no concrete plan had been submitted, he had no comment. Washington read that as a quiet yes. Iceworm stayed hidden for nearly four decades. It came to light only after the 1968 crash of a B-52 carrying four hydrogen bombs near Thule pushed the Danish parliament to order an inquiry, and the Danish Foreign Policy Institute published the documents in 1997. It was the same kind of Cold War secret as the CIA’s attempt to raise a Soviet submarine, kept quiet for years behind a cover story.

The ice would not hold still

Iceworm was killed by money, Pentagon rivalries and the Navy’s new Polaris submarines, but above all by the ice itself. An ice sheet looks solid, but it flows. Under its own weight, snow and ice slowly creep like a very stiff liquid, the way pitch does in science’s slowest experiments. Britain had learned something similar during the war, when it tried to build an aircraft carrier out of ice and found that ice, even reinforced ice, slowly sags under its own weight.

At Camp Century the walls squeezed inward and the ceilings sagged downward month by month. Measurements showed the main trench losing about an eighth of its cross-section every year. Heat made it worse. The reactor’s warm water tanks softened the surrounding snow, and by mid-1962 the reactor room’s ceiling had dropped so far that it had to be raised five feet. Keeping the tunnels at their original size meant trimming and hauling away about 20,000 cubic yards of snow a year, an Army report estimated, much of it with hand tools. The sewage pit leaked, too. Liquid waste spread up to 170 feet sideways through the snow, and the smell crept into nearby bunk rooms.

For a missile base meant to last for years, the ice was an impossible foundation. In July 1963 the Army shut the reactor down for maintenance and never restarted it. Crews pulled out the core that autumn and took the plant apart in the summer of 1964. The ship carrying it backed away from the Thule pier at midnight on July 26. Camp Century ran on diesel as a summer-only camp for a while longer and was abandoned in 1967. The Army left behind the buildings, the tunnels and the waste, assuming that the snow would bury them forever.

The core that outlived the camp

While soldiers fought the ice, a small team from the Army’s Cold Regions Research and Engineering Laboratory was drilling into it. The team, which included engineer B. Lyle Hansen and glaciologist Chester Langway, worked from a trench of its own, first with a thermal drill that melted its way down and later with a cable-suspended electromechanical drill. Section by section, the cylinders of ice came up, were logged, and packed into freezers.

In July 1966 the drill reached the bottom of the ice sheet, 1,387 meters (about 4,550 feet) down. It was the first core ever drilled through the full thickness of the Greenland ice. The drillers kept going for another 12 feet into the frozen soil and rock beneath, then stopped.

The ice went to the Danish physicist Willi Dansgaard, who had discovered that the ratio of heavy to light oxygen atoms in snow records the temperature of the air it fell from. In 1969 he and his colleagues published “One Thousand Centuries of Climatic Record from Camp Century on the Greenland Ice Sheet,” the first long climate history ever read from ice. It showed the last ice age in detail and hinted at sudden, violent swings in temperature, the events now named after Dansgaard and his Swiss colleague Hans Oeschger. Ice cores have been read that way ever since, including the sulfur layers left by eruptions like the one behind the Year Without a Summer.

The jars at the back of the freezer

The frozen soil from the bottom got far less attention. A couple of early studies looked at its pebbles and found traces of freshwater algae, hinting that the ground had once been free of ice. But there was no way to date it, and interest faded. The core moved from an Army freezer to the University at Buffalo, where Langway ran an ice core lab. By the 1990s, frustrated that almost nobody was asking for samples, Langway told the Danes to come and take the ice, “otherwise it goes into Lake Erie.” The cores were shipped to the Niels Bohr Institute in Copenhagen.

In 2017, as staff prepared to move the collection to a new freezer, Jørgen Peder Steffensen and Dorthe Dahl-Jensen opened two boxes oddly labeled “Camp Century sub-ice.” Inside were about 30 glass jars, which Steffensen took to calling cookie jars, holding dirty lumps of frozen sediment. It took a moment to sink in: this was the ground from beneath the ice sheet, collected in 1966 and never properly studied. “There’s less of this stuff than there is Moon rocks,” the University of Vermont geologist Paul Bierman told Science.

When Bierman’s colleague Andrew Christ looked at the first samples under a microscope in 2019, he saw twigs, leaves and moss, perfectly preserved. Plants could only have grown there if the ice was gone. A 2021 study in PNAS showed that northwestern Greenland had been ice-free and green at least once within the last million years. In 2023 the team pinned down the date in Science, using a technique that measures how long mineral grains have been hidden from sunlight: about 416,000 years ago, during a long warm spell called Marine Isotope Stage 11. The ice at Camp Century had vanished, and tundra grew there for up to 14,000 years.

That matters for the present. For the ice to disappear from that spot, the team’s models show, enough of Greenland must have melted to raise global sea level by at least 1.4 meters (about 4.6 feet). Carbon dioxide then sat between about 265 and 280 parts per million for some 30,000 years. Today it is above 420. Drilling deep for answers rarely goes to plan, as the Soviet engineers who sank the deepest hole on Earth found, but few holes have repaid their drillers so handsomely, or so late.

What is still down there

The camp the Army abandoned is still in the ice, crushed and deeper every year. A 2016 study led by William Colgan, now at the Geological Survey of Denmark and Greenland, estimated what it holds: about 200,000 liters of diesel fuel, some 24 million liters of wastewater including sewage, PCBs, and an unknown amount of low-level radioactive waste. Army records indicate that some 47,000 gallons of low-level radioactive liquid from the reactor were discharged into the ice. The study warned that if warming turned the site from a place where snow builds up into one where it melts away, the waste could eventually re-emerge.

Later monitoring has been more reassuring, at least for this century. Since 2017 a Danish climate monitoring program has kept a weather station and instruments at the site. Its measurements show that snowfall there still outpaces melting and that meltwater has not soaked down anywhere near the buried camp. “There is no risk that the debris will come to the surface due to melting before 2100,” Colgan has said. Denmark and Greenland agreed in 2018 to spend 180 million kroner clearing other abandoned American sites in Greenland. Camp Century, at least 100 feet down, is beyond reach for now.

NASA’s 2024 radar view may never be more than a curiosity. Its real purpose was to learn how to map the bed of ice sheets, which scientists need in order to predict how fast they will melt and how high the seas will rise. But it gave the world its clearest look yet at the town the Army built to hide missiles, abandoned to the ice, and accidentally turned into one of the most important climate archives ever drilled. The city under the ice was supposed to be invisible. In the end, what it found was more lasting than anything it was built to hide.

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