The frozen cavern is a few hundred feet below the surface of the Greenland ice sheet and near-silent, save for an occasional boom or groan from cracks splintering in the distance or around the scientists’ feet.
Shafts of light reach through the opening, brightening slivers of high blue walls.
This is a moulin, a yawning gap that serves as a portal for meltwater, which plunges under the surface. University of South Florida geology professor Jason Gulley explores these depths with other researchers, hoping to understand how the icy drainage system affects rising seas around the world, including on vulnerable shores back home.
“Nearly every river on the Greenland ice sheet ends in one of these pits,” he said. Scientists need a better sense of where, and how, the meltwater flows.
Gulley, 42, descends on ropes, trying to spot fragile truck-sized blocks of ice that could break off and kill him. Sometimes, his glasses fog; it’s often warmer under the ice, away from gusts that spin up snow around camp. The sheet is nearly half a mile thick.
With other scientists, Gulley has found that moulins are bigger than people guessed. They expand like a bell into vertical caverns, where the researchers follow the beams of their headlamps toward dark edges. The ice melt does not drop right to the bottom but can be stored in vast chambers, where water levels vary — at least in the couple of spaces they have been able to explore. They have dropped into two moulins, in 2018 and 2019.
“We’ll probably never be able to access the entire storm sewer system,” Gulley said. But seeing even the first several hundred feet of a couple of moulins has given them a start, revealing still more questions about the threat from Greenland’s melting ice under climate change.
The caverns form, Gulley said, when a lake or river pours into a crevasse. All the water creates pressure — like a maul splitting wood — eventually forcing open chambers as it works its way down. In the summer, waterfalls gush through the openings. By fall, they dry up, and researchers can rappel inside.
Planet-warming emissions are causing the ice sheet to degrade more quickly, said Sarah Das, a scientist at the Woods Hole Oceanographic Institute, who studies ice in Greenland. The snowfall each year no longer balances out the melt.
In imagining the interior of the sheet, scientists had thought of the pits like narrow shafts, transporting water quickly to bedrock, said Kristin Poinar, a glaciology professor at the University at Buffalo.
Turns out “the system is so much more complicated,” said Kristin Schild, a glaciologist at the University of Maine.
The guesswork adds uncertainty to models of how the ice could change over time — and thus how far seas could rise. The sheet is always moving. When the ice reaches Greenland’s warmer edges, it breaks off to the ocean and melts.
Meltwater at the base, scientists believe, can accelerate this process, reducing friction under the sheet. Think of hydroplaning in a car, Das said. A patch of water makes the tires lose traction. Gulley said higher water pressure at the base is associated with higher sliding speeds.
Moulins are a small component of a big system, Das said, but their exploration is “a really neat piece of the puzzle.” It offers opportunities for analyzing the connection to the sheet’s velocity.
“We can map and understand what’s happening on the surface,” she said. “It’s very hard to get inside a glacier or get under Greenland.”
Gulley enjoys some of the extremes that come with such far out science.
There’s no direct flight from the United States to Greenland, he said. A helicopter costs about $6,000 an hour to fly up to five people to their remote camps.
“You can’t walk there. You can’t walk off,” Gulley said. After a week or two, “you just kind of hope the helicopter comes back to get you when it’s supposed to.”
They have descended in October, when winds howl 40 to 50 mph across the surface of the ice, whipping around their tents. Temperatures routinely plummet below zero — cold enough to store food, like living in a big refrigerator.
Bread goes stale quickly, but vegetables and meat keep.
To lower into a pit, researchers install 22-centimeter (about 9-inch) ice screws, tie up ropes and rappel. They hold to the ice with the help of crampons affixed to their boots and pluck away with axes, preemptively knocking off chunks that could fall on them.
Gulley became interested in moulins as a student working on rocky caves. On a climbing trip in Kentucky, where he lived, he met a man who observed lakes flowing into holes around Mt. Everest. Soon, Gulley was driving up to Canada on weekends, practicing ice climbing.
He struggled to secure funding to explore the Greenland moulins. Grant organizations worried about something so risky. Gulley said he and his colleagues caught a break when an ice climber, Will Gadd, got money for a hybrid science-film project from Red Bull.
“To do this as a private citizen would just be so expensive,” Gulley said. “Most times I’m going on these trips, I’m pretty stoked.”
Even from afar, he thinks often of Greenland. Gulley doesn’t enjoy climbing in gyms, but he spends a lot of time cave-diving in local springs. His Instagram feed alternates between close-ups of manatees and dramatic shots of the ice and northern lights.
But what happens on the ice sheet could shift sea levels in Florida by several feet, he said. Gulley wonders sometimes whether he and other researchers are merely “writing the obituary” of the planet.
In Florida, living through a pandemic, he sees parallels to the current public health crisis. “Climate scientists share a lot of the same frustrations that epidemiologists and doctors have right now,” he said.
They know what people need to do: cut emissions to slow the warming that melts the ice.
“It’s just that there’s no political will to do it,” Gulley said.
This story was produced in partnership with the Florida Climate Reporting Network, a multi-newsroom initiative founded by the Miami Herald, the South Florida Sun Sentinel, The Palm Beach Post, the Orlando Sentinel, WLRN Public Media and the Tampa Bay Times.