Ten miles north of Fairbanks, Alaska, deep in the recesses of an excavated hillside, geochemist Thomas Douglas brandished a 20,000 year-old stick with the kind of enthusiasm that can only be mustered by a scientist.
"There's something really special about this place," he said, surveying the narrow, 360-foot long, eight-foot high passage known as the Permafrost Tunnel.
The Permafrost Tunnel, a research facility constructed and operated by the US Army, was built between 1963 and 1969, and it "offers a unique research platform for scientists and engineers who wish to study a frozen environment over 40,000 years old," according to the Cold Regions Research and Engineering Laboratory, a division of the US Army Corps of Engineers.
More than 70 papers have been written about the Permafrost Tunnel. Researchers come here to study everything from mining and geotechnical engineering to paleontology and geocryology. Even NASA scientists come here to test out machinery intended for Mars.
The tunnel is midway through a construction project that will allow climate scientists to 3D map the tunnel's permafrost features and conduct warming experiments.
I visited the tunnel in March 2016 to catch up with scientists on the progress they're making, and the new research projects scheduled for later this year.
Over a seven-year period in the 1960s, the US Army Cold Regions Research and Engineering Laboratory dug through a hillside in Fox, Alaska, to study excavation in permafrost.
Ultimately driven by Cold War fears, the Army never intended to study the fate of the frozen soil in the face of a changing climate, but rather hoped the experience would help with underground military installations. It was a well-known fact permafrost could absorb shocks from explosions and remain intact, making the Army optimistic the tunnel could later be used as a shelter or storage.
Today, the entrance to the tunnel is marked by an unassuming red shed off of Steese Highway, and access is tightly controlled.
Early on, the Army realized it would need to refrigerate the tunnel. Once you cut into permafrost, disturbing the active, vegetative layer that insulates the frozen soil, it quickly begins to thaw. "We keep it about -4 degrees Celsius in here," said Thomas Douglas, a geochemist who works at the tunnel. In the summer, they use a chill room, and in winter they blow cool outside air into the back of the tunnel. "Climate change is not affecting the tunnel at all," he said. "Some day this may be the only permafrost left in the area."
"One of the coolest parts of the tunnel is this green grass," said Douglas, grabbing a fistful of 20,000 year-old blades, covered in a thick layer of loess. "There's lots of organic material oozing out of the wall, but this is the only spot where where we have chlorophyll."
An ice wedge takes hundreds, if not thousands, of years to form. Created when rainwater and snowmelt flow into cracks in the soil, freezing and thawing for centuries to come, these wedges are abundant in Alaska's North, where 70 to 90 percent of the ground can be ice. Climate change is causing these structures to melt much faster than expected, and scientists worry the residents of places like Barrow may soon see land slump and subside below sea level.
Douglas surveys a series of boreholes drilled into the Permafrost Tunnel. Road building in Alaska is made especially difficult thanks to permafrost, and massive ice wedges that can thaw and melt when disturbed by construction work. To determine whether or not an ice wedge is hidden below the ground's surface, engineers will drill holes every 328 feet. But it's pretty easy to miss these frozen behemoths, which rarely span more than 30 feet.
The Permafrost Tunnel doesn't only attract climate change researchers and engineers, it's also of increasing importance to NASA. Scientists from around the world come here to use the facility as an analog for the conditions on Mars. While the Mojave Desert has been used to study soils that have the same geochemical content as those on Mars, the soils there have one big shortfall—they're not frozen."If you want to look at frozen soils and do things like sublimation, test drill bits and rover wheel designs, or watch these soils over time, the tunnel is wonderful because it's frozen and accessible year-round," Douglas said.
This part of the Alaskan Interior was never covered by the Pleistocene Ice Sheet. Twelve thousand years ago, it served as a grassy safe haven for megafauna—woolly mammoths, steppe bison, and ancient horses. Today, their bones are found with surprising abundance around the Permafrost Tunnel. "I've seen bone collections in the Goldstream Valley that are unbelievable," said Matthew Sturm, a geophysicist who studies snow. "Miners could wash out full garbage cans of Pleistocene bones in a single shift."
In the 1920s and '30s, many of those bones made their way to New York's Museum of the Natural History by the trainload. "This was an amazingly verdant place at one time. It's all vanished now," said Sturm. "We killed off these enormous creatures just by changing grass and mosses. If there's not a lesson there, boy, I don't think there is one."
When permafrost thaws ("Thaws, not melts," said Sturm. "A frozen turkey doesn't melt, it thaws") it quickly turns into a mucky brown mixture. In the area around Fairbanks, the permafrost is "discontinuous," meaning permafrost often only forms in spots that are sheltered and cooled by thick vegetation or mountains. Come summer, the sun can thaw the permafrost for weeks or months at a time, leading to slumping, uneven ground.
Beginning in 2011, engineers began to expand the Permafrost Tunnel, citing an increased need for understanding how permafrost will respond to global warming, and the role thawing permafrost will ultimately play in exacerbating carbon levels in the Earth's atmosphere. Permafrost stores roughly 30 percent of all land-based carbon on the planet. As permafrost decomposes, it releases that carbon into the air, creating a dangerous feedback cycle. The new tunnel, which engineers plan to connect to the old 1960s tunnel, will allow scientists to 3D map complex permafrost features, like ice wedges, and provide side rooms for permafrost warming experiments.