Buried under the ice
The Washington Post August 25, 2023
Scientists came to Greenland on an unprecedented mission to drill for rocks that would reveal the fate of this fast-melting ice sheet.
Then a sudden crack in the ice threatened to doom their experiment - and imperiled their plan to predict just how devastating sea level rise could be.
Greenland had not been kind to Joerg Schaefer. For 21 days, he had endured howling winds and blistering cold. He sampled ice until his fingers went numb and shoveled snow until his shoulders burned. His shelter was a cramped yellow tent, his bathroom a hole in the ground.
And the experiment that brought him to this ruthless, frozen expanse - an unprecedented effort to drill through more than 1,600 feet of ice and uncover the bedrock below - was teetering on the brink of failure.
A thin, dark fracture had appeared deep in the ice, making it impossible to drill. The team's engineers were trying to repair the hole, but it was far from clear whether the fix would work. Schaefer's hopes - and research that could help predict the fate of Greenland's ice sheet and its contribution to rising seas - clung to the smallest possible chance that the team might still find what they came for.
Now, Schaefer would have to leave with his mission unfinished. A family emergency had called him home to New York, and a helicopter was waiting to take him back to civilization.
"The timing feels completely wrong," said Schaefer, a climate geochemist at the Lamont-Doherty Earth Observatory and the lead investigator for the project known as GreenDrill. "We have been working toward getting that bedrock for literally years. . . . It's pretty heartbreaking now to leave."
The drilling expedition this spring was only the third time in history that researchers had tried to extract rock from deep beneath Greenland's ice. Scientists have less material from under the ice sheet than they do from the surface of the moon. But Schaefer believes the uncharted landscape is key to understanding Greenland's past - and to forecasting the future of the warming Earth.
The Greenland Ice Sheet contributes more to rising oceans than any other ice mass on the planet. If it all disappeared, it would raise global sea levels by 24 feet, devastating coastlines that are home to about half the world's population. Yet computer simulations and modern observations alone can't precisely predict how Greenland might melt. Researchers are still unsure whether rising temperatures have already pushed the ice sheet into irreversible decline.
Greenland's bedrock holds the ground truth, Schaefer said. The ancient stone that underlies the island is solid, persistent and almost unmovable. It was present the last time the ice sheet completely disappeared, and it still contains chemical signatures of how that melt unfolded. It can help scientists figure out how drastically Greenland may change in the face of today's rising temperatures. And that, in turn, can help the world prepare for the sea level rise that will follow.
Schaefer trudged to the drill tent to say goodbye. Inside, four engineers were troubleshooting yet another problem with their massive machine.
"So, you're leaving us?" asked Tanner Kuhl, the project's lead driller.
"I'm not thrilled about it," Schaefer said. He clapped Kuhl on the shoulder. "Keep fighting."
The team was running out of time and money to get through the last 390 feet of ice. Success would require drilling faster than they ever had before. But no one was prepared to give up - not yet. Too much had been invested in their five-year, multimillion-dollar project to collect bedrock samples from around Greenland. Too much was at stake, as human-made pollution warms the Arctic at a pace never seen before.
Reluctantly, Schaefer clambered into the helicopter. He watched as the ground fell away, and the GreenDrill encampment shrank to a tiny splotch of color amid the endless white.
He could only imagine what secrets lay beneath that frozen surface. He could only hope - for his own sake, and for the planet's - that those secrets would someday be known.
The morning of Schaefer's arrival on the ice sheet, three weeks earlier, was luminous and still. Barely a breeze jostled the helicopter that carried him to the field camp in northwest Greenland. Beneath him, the glittering expanse of the Prudhoe Dome ice cap resembled the ocean: Beautiful. Mysterious. Mind-bendingly huge.
Theoretically, Schaefer had already grasped this. The dome's size was one reason it had been selected as a GreenDrill sampling site - the first of three strategic locations around Greenland where he and his colleagues planned to drill for bedrock samples over the next few years. Yet Schaefer was still stunned as the helicopter touched down on the dome's summit. Despite a decades-long career in polar science, this was his first time on an ice sheet.
"It's a monster," he thought. Schaefer tried to imagine all that ice melting and flowing into the ocean. The catastrophic possibility made him shiver.
He knew that such a disaster had happened before. In 2016, Schaefer and his close colleague Jason Briner, a geology professor at the University at Buffalo, were part of a team that analyzed the single bedrock sample that had been previously collected from beneath the thickest part of the ice sheet. The rock contained chemical signatures showing it had been exposed to the sky in the past 1.1 million years. In a paper they published in the journal Nature, the scientists concluded that almost all of Greenland - including regions now covered by ice more than a mile deep - must have melted at least once within that time frame.
"That was a game changer," said Neil Glasser, a glaciologist at Aberystwyth University who has followed Schaefer's research. "It said that the Greenland ice sheet is far more dynamic than we had ever thought."
The findings ran counter to many scientists' belief that Greenland has been relatively stable throughout recent geologic history, as the Earth oscillated between ice ages and milder warm periods known as interglacials. If the ice sheet could melt at a time when global temperatures never got much higher than they are now, it was a worrying harbinger of what ongoing human-caused warming might bring.
For Schaefer and Briner, the discovery also underscored how bedrock could complement findings from ice cores - the long slices of frozen material that had traditionally been the focus of polar science. For decades, scientists had studied air bubbles trapped in ice to uncover crucial clues about the climate at the time the ice formed.
Yet ice cores, by their very nature, could only reveal what happened during the colder phases of Earth's history. They couldn't answer what Schaefer said is arguably the most important question facing humanity now: "What happened when it got warm?"
With GreenDrill - which is funded by the U.S. National Science Foundation - he and Briner aimed to open up a new kind of record, one that didn't melt away. By collecting bedrock samples from around the island, they could gain a clearer picture of exactly when the ice sheet last vanished and what parts of Greenland melted first.
But to get those rocks, they would need to survive for more than a month in one of the most remote and hostile places on Earth.
The effort was shaping up to be harder than anyone had anticipated. It took seven plane trips for the team to haul GreenDrill's equipment onto the ice sheet. Twice they were delayed by blizzards. Then a windstorm halted work on the drill for three full days.
The scientists who oversaw camp setup - Lamont Doherty geologist Nicolás Young and University at Buffalo PhD student Caleb Walcott - already looked exhausted as they welcomed Schaefer to the ice.
They watched Schaefer's helicopter depart in a whirl of windblown snow. Then Young and Walcott led him to one of about a dozen yellow tents that had been staked onto the ice - Schaefer's home for the next three weeks. Its insulated double walls were designed to keep temperatures inside just above freezing. A cot lined with an inflatable sleeping pad would keep him off the frigid tent floor.
Next door stood the larger kitchen tent, which was equipped with propane stoves and a single space heater - the only heat source they would have on the ice. The nearby storage tent was stocked with hundreds of pounds worth of beans, granola bars and other nonperishable foods.
Dozens of green, black and red flags marked paths through the camp; in case a blizzard made it hard to see their tents, the team members were to follow the flags to safety.
As they headed toward the drill tent, Schaefer heard the growl of engines and the whine of machinery. Yet he was unprepared for what he saw when he peered inside.
The Agile Sub-Ice Geological (ASIG) drill was a complex beast - 30,000 pounds of cable, aluminum and steel.
Every component had to be assembled on the ice, from the towering mast to the diesel engines to the system of hydraulic pumps that caused the hollow drill rod to turn.
In the first stage of drilling, the ice was permeable. Engineers drilled a wider pilot hole that could be fitted with an aluminum casing to seal the hole.
As the drill advanced, it reached solid ice. The drill bit was replaced with one that had three angled blades that shaved the ice as it spun.
If allowed to remain in the borehole, the chips of shaved ice would accumulate and trap the drill bit. So the drillers pumped a pressurized fluid called Isopar down the side of the hole until it pushed the chips up through the center of the hollow drill rod.
Engineers would have to drill through more than 1,600 feet to reach the bedrock beneath the ice sheet.
Only then would they be able to collect the rock samples and return them to the surface.
The machine was state of the art; whereas older drills would take years to cut through 1,600 feet of ice, ASIG could achieve the same feat in a matter of weeks. It was one of few drills in the world that could extract bedrock from deep beneath an ice sheet. Yet it had been used successfully just once before, and never in Greenland.
For the first time - but not the last - Schaefer found himself wondering, "What on Earth did we do to get this enterprise up here?"
"Maybe something goes wrong?" he thought. "Maybe we don't get through this ice."
But he was reassured by the unflagging support of the National Science Foundation and the unflappable competence of the GreenDrill team. Briner, the project's co-leader, was a leading scholar of Arctic ice. Kuhl, an engineer with the U.S. Ice Drilling Program, had overseen the only other successful ASIG project, in Antarctica. His partner, Richard Erickson, had more than two decades of experience in minerals drilling. The camp manager, technician Troy Nave, had spent a combined 34 months living at the poles.
And then there was Allie Balter-Kennedy, Schaefer's former PhD student who had defended her dissertation just a month earlier. Though she was many years his junior, Balter-Kennedy had spent much more time doing remote field work. It was she who explained to Schaefer how to stay warm at night - by sticking a bottle of boiling water in his sleeping bag - and who tempered his frustration every time a storm threw a wrench in their plans.
"They are just the ultimate professionals," Schaefer often said of his colleagues. If any group could pull off such a far-fetched experiment, he thought, this one would.
When Schaefer thought about the research that had led him to this remote corner of the planet, it struck him as something out of a fairy-tale.
The story began a long time ago, in a distant corner of the universe, amid the death throes of ancient suns.
When stars explode, they send sprays of high energy particles into the cosmos. A few of these cosmic rays are able to make it through Earth's atmosphere and reach the ground below. And when those particles encounter rocks, they can interact with certain elements to create rare chemicals called cosmogenic nuclides.
These nuclides accumulate in surface rocks at predictable rates. Some are also radioactive, and they decay into new forms on distinctive timelines. This allows scientists to use them as molecular clocks. By counting the numbers of nuclides within a rock, scientists can tell how long it has been exposed to cosmic ray bombardment. And by comparing the ratios of various decaying elements, they can determine when ice began to block the rock's view of the sky.
With this technique, ordinary rocks are transformed into something almost fantastic. They are witnesses, capable of remembering history that occurred long before any humans were around to record it. They are messengers, carrying warnings of how the ice - and the Earth - could yet transform.
"It's like a magic lamp," Schaefer said. "It's pretty crazy that a little piece of rock can tell you the story of this massive sheet of ice."
But cosmogenic nuclides are difficult to study; Schaefer had spent much of his career helping to develop the equipment and techniques needed to detect a few tiny nuclides in a piece of ancient rock.
And - as Schaefer was now learning - rocks from beneath an ice sheet are immensely challenging to obtain.
Days at the GreenDrill field camp began at 6:30 a.m., as Schaefer woke to the sound of engineers turning on the ASIG generators. He dressed quickly in the cold, and grabbed coffee and breakfast in the kitchen tent. With a satellite phone, he checked in with the National Science Foundation support team and got an updated weather forecast: Usually windy. Sometimes snowy. Almost always well below zero degrees Fahrenheit.
Then he bundled back up and headed outside to start work.
Until the drillers hit bedrock, the scientists' primary task was to collect the ice chips pushed up by the Isopar drilling fluid. Schaefer, Young and Balter-Kennedy took turns scooping the ice into small plastic bottles. Back at their lab, they would analyze those samples for clues about Greenland's temperature history - research that would complement their bedrock analysis.
The rest of their time was spent shoveling in a Sisyphean effort to keep the camp from being buried by the endlessly swirling windblown snow.
Fifteen miles away, Briner and his student Walcott had set up another camp closer to the edge of the ice sheet. There, the team was using a smaller Winkie drill to collect a second sample from beneath a much thinner part of the ice cap.
In each sample, the team planned to analyze as many as six different cosmogenic nuclides, but they would focus on two: beryllium-10 and aluminium-26.
When cosmic rays strike a rock, radioactive aluminum accumulates at a much faster rate than beryllium. Yet aluminum-26 also decays faster once the rock has been covered up by ice. If a sample has relatively little aluminum-26 compared to beryllium-10, it suggests that site has been buried under ice for hundreds of thousands of years. But if Schaefer and Briner found a high ratio of aluminum-26 to beryllium-10, it would mean the site had been ice-free in the more recent past.
With that analysis, the researchers would then be able to compare the exposure histories of each drilling site. They could determine how much warming it previously took for the ice sheet to retreat the 15 miles between Winkie and ASIG, which would give them a sense of how fast Prudhoe Dome might disappear someday.
"That's a really important element of GreenDrill," Briner said. "We're drilling more than one site so we can look at different parts of the ice sheet . . . and we can ask, 'What does it say about the shape of the whole ice sheet if this part is gone?'"
As Schaefer settled into the rhythm of camp, his body adjusted to the incessant polar sunlight and the relentless manual labor, leaving his mind free to wander. Often, he found himself fixating on the ice sheet - its incomprehensible vastness, its unfathomable fragility. How could something this immense and forbidding be so vulnerable? How could a landscape so obviously capable of killing a person be at risk because of humanity?
Yet in the years since Schaefer and Briner published their 2016 paper, Greenland's vulnerability had become more and more clear. This year was shaping up to be one of the island's worst, with melting in the southern part of the ice sheet on track to set a new record.
Meanwhile, research showed how the melting process is self-reinforcing: Dark pools of water on Greenland's surface absorbed the sun's heat, rather than reflecting it. The diminishing height of the ice sheet exposes the surface to the warmer air at lower altitudes. If the ice shrinks far enough, it could enable the rising ocean to infiltrate the center of the island, which is below sea level. That warmer water would melt the ice sheet from below, accelerating its decline.
Under the worst case warming scenarios, the melting Greenland ice sheet is expected to contribute as much as half a foot to global sea level rise by the end of the century. It would swamp Miami, submerge Lagos and deluge Mumbai. In New York City, where Schaefer lives with his wife and two children, coastal flooding would inundate the subways, destroy sewers and power plants and wash away people's homes.
This knowledge made Schaefer's quest feel less like a fairy-tale than a medical drama - an urgent effort to understand the sickest part of Earth's embattled climate system.
"We are basically taking biopsies," he said, "which will hopefully tell us how sensitive the patient is to ongoing warming - and how much warming is fatal."
As soon as he saw the looks on the drillers' faces, Schaefer realized something had gone terribly wrong.
For three weeks, they'd been making slow but steady progress through the ice sheet, reaching nearly 1,300 feet below the surface. But suddenly, the pressure in the borehole started to drop. The Isopar wasn't able to push the ice chips up through the drill rod, and Kuhl feared the fluid must be leaking through a crack in the hole.
Schaefer knew the word "fracture" was like "Voldemort" - the name of the villain in the Harry Potter series. Like the name, a fracture inspired so much dread that the scientists avoided even mentioning it.
Yet there was no denying the thin, dark fissure in the ice that appeared about 250 feet down when Schaefer dropped a camera into the borehole. His heart sank. If they couldn't find a way to isolate the fracture, they wouldn't be able to maintain enough pressure to push chips out of the hole, and drilling would grind to a halt.
"Basically game over," Schaefer wrote in his waterproof field notebook.
He went to bed that night with his mind racing. The fracture shouldn't have happened, he thought. Ice was supposed to be able to withstand pressures far greater than what Kuhl and Erickson were using. Did this mean the ASIG drill didn't work as well in Greenland? Would it threaten all of the other drilling they had planned?
The next morning, he woke to the howling of the wind.
Another unseasonable blizzard had descended on Prudhoe Dome, blotting out the endless icescape with an impenetrable cloud of white. When Schaefer peered out of his tent, he could barely see the colored safety flags that were supposed to guide him through camp.
The team gathered in the kitchen tent, listening to the eerie whistle of snow blowing over ice and the snapping of flags in 50 miles-per-hour gusts.
Schaefer got a satellite message from Briner: Conditions were even worse at the Winkie Camp, where the fierce wind had ripped a hole their kitchen tent, scattering supplies and burying cooking equipment in snow.
It wasn't safe to work on the fracture. It wasn't safe to even be outside for more than a few seconds. All they could do was wait for the storm to end.
Schaefer tried to combat the growing worry that he had led his team into disaster. He had underestimated the complexity of drilling through so much ice. He hadn't reckoned with the possibility of so much bad weather.
In his lowest moments, it felt as though Greenland had been conspiring against him.
But after three days, the wind finally died down. The air cleared. And Kuhl had come up with a plan to fix the fracture.
The engineers could deepen the upper part of the borehole, which was sealed with the aluminum casing, so that the casing extended to cover up the crack. They could also switch the way Isopar circulated through the borehole to minimize pressure on the ice.
It took the drill team two days to make the repair. A week after the fracture first appeared, they tried refilling the borehole with fluid. It held. The project was still alive - but just barely.
Schaefer got more good news the following day, when Briner arrived from the Winkie camp.
"I brought you a present," Briner said, grinning. He opened a long cardboard box to reveal 79 inches of sediment and pebbles mixed with chunks of a large bolder. Despite the blizzard, the Winkie team was able to extract their rock core from beneath 300 feet of ice.
"Are you kidding me?" Schaefer gasped. The sediments could include traces of plants and other clues to the ancient Greenlandic environment. And the boulder pieces contained plenty of quartz - perfect for cosmogenic nuclide analysis. It would give the team crucial clues about what had happened at the ice sheet's vulnerable outermost edge.
Schaefer reached out to shake hands with Elliot Moravec, the lead Winkie driller. "Thank you man," he said. "That's a really great sample."
With the Winkie core in hand, Moravec and his partner Forest Rubin Harmon were also free to help Kuhl and Erickson keep the ASIG machinery running.
Yet now the team had another enemy: time. There was less than a week until they were supposed to start taking down the camp. They also had to redrill through the frozen ice shavings that fell into the borehole during the repair process. Yet they couldn't go too fast, or they risked triggering another fracture.
"It's slow motion, drilling through the slush," Kuhl said, shouting over the whine of the drill.
Then the noise stopped. Kuhl and Erickson peered into the borehole: They'd hit another blockage.
Kuhl grimaced. "There's almost no chance we get this done now," he said. "But who knows? We'll keep trying and maybe something will work."
By the time Schaefer was set to depart, progress was still painfully slow.
"Leaving these guys alone now feels really shitty," the scientist said. But his family needed him at home, and flights out of Greenland were so infrequent there was no option for him to take a later plane.
Schaefer shook his head. Three weeks ago, he thought this was a medium-risk, high-reward project - that the effort and expense were absolutely justified by the scientific value of the rocks they would uncover.
Now, knowing the true level of risk, facing down the very real probability of failure, he couldn't avoid the question: Was it all worth it?
The Manhattan streets were packed with people, ringing with conversation and birdsong. The air was warm. The late spring breeze was gentle.
Yet Schaefer felt ill at ease as he paced the rooms of his narrow New York apartment. His mind was still 2,500 miles away.
Back at Prudhoe Dome, Balter-Kennedy was overseeing the last-ditch efforts to salvage GreenDrill's field season. She sent Schaefer daily updates via satellite messenger, but the news wasn't good. On Friday, the drillers only managed to cut through about 40 feet of ice. On Saturday, they pulled up the entire apparatus and switched to a different type of drill rod - to no avail.
Sunday morning in New York dawned sunny and mild. In Greenland, it was the last day before planes were supposed to start taking their equipment off the ice. The complex operation could not be delayed - and even if that was an option, conditions would soon become too warm for the team to safely drill.
By the time his phone buzzed with Balter-Kennedy's regular evening check-in, Schaefer was braced for failure. He had already rehearsed what he would tell the team: This didn't change how hard they worked, or how much he appreciated them. They'd tried to do something no one had done before. They had learned valuable lessons for next year. And the world desperately needed the information buried beneath Greenland's ice - no matter the risk, their efforts were worth it.
But when Schaefer answered the satellite call, Balter-Kennedy was ecstatic. The team got through more than 150 feet of ice that day - an all-time record for the drill they were using. They were 90 percent of the way to bedrock.
Schaefer felt as though his heart had stopped beating. The rest of the conversation was a blur, as Balter-Kennedy explained how the engineers finally overcame the blockages that had slowed their progress. Erickson, the longtime minerals driller, suggested they try using a drill bit that is usually reserved for rocks. It was an outside-the-box suggestion from someone unaccustomed to drilling through ice - but it worked.
"The ASIG is back in the race," Schaefer said that night. "And with all the overwhelm and confusion that I have inside me, it's clearly much, much better than the big emptiness I would have if it would be called off."
Still cautious, he added: "Which of course, can still occur. The slightest problem now and it's over. But they are within striking distance. It could still happen."
The next day, Schaefer had to hold himself back from bombarding Balter-Kennedy with requests for updates. Instead, his thoughts drifted to the laboratories at Lamont Doherty where his team would analyze the GreenDrill bedrock - if they ever got it.
He could already imagine the steps that would come next.
First, the scientists would slice samples from the main core. Next would be a weeks-long chemical procedure designed to rid the sample of unwanted material, leaving behind only the elements the scientists had chosen to analyze. Finally, the samples would be sent to labs in California and Indiana, where they'd be shot through particle accelerators and weighed to determine the proportion of cosmogenic nuclides.
Within about six months, the GreenDrill team would know when the ASIG bedrock last saw daylight. And those results would illuminate whether Prudhoe Dome's future is simply grim - or completely catastrophic.
Schaefer hoped he would find that the ASIG site hadn't been ice-free since the interglacial periods that punctuated the Pleistocene epoch, more than 100,000 years ago. But it was possible that this region melted during the Holocene, the 11,700-year stretch of mild temperatures that began at the end of the last ice age and continues through today.
"That would be another level of devastating," Schaefer said. Modern temperatures are quickly surpassing anything seen during the Holocene epoch. If Prudhoe Dome couldn't survive those conditions, then under human-caused climate change, it may soon be doomed.
Five days after Schaefer's departure, ASIG hit the bottom of the ice sheet - 1,671 feet below the surface. Now the drillers would switch to a bit that could cut cores out of rock, while Balter-Kennedy and Walcott scrambled to pack up the rest of the camp. All Schaefer could do was wait.
He alternated between agitation and exhaustion - first pacing his apartment, then collapsing on the couch, then springing up to pace again. On a whim, he wandered into the soaring Gothic sanctuary of the Cathedral of St. John the Divine. It had been Balter-Kennedy's idea: When he complained of his helplessness on one of their satellite calls, she jokingly suggested he could pray for the team.
So, although it had been years since he set foot in a church, he paused to light a candle for Greendrill.
Finally, in the very early hours of Wednesday morning, he got the messages he had been waiting for.
"We have 3 m of bedrock!!!"
"Going down for 4.5 now"
Hands shaking with adrenaline, Schaefer could barely type his response.
"Ukidin?? Not real! Omg! YESYEYES!! WowFantastic!!!U literally change Ice/Sheet Science! All undercyour lead! That's why u joined!"
A few hours later, Balter-Kennedy called on the satellite phone. In her usual, even-keeled tone, she described how the drillers worked through dinner and deep into the night. They had nearly 10 feet of sediment and another 14.5 feet of pristine bedrock - more material than Schaefer even dreamed was possible.
But when she hurtled into questions about departure logistics, Schaefer interrupted her. He wanted to make sure she had a chance to appreciate the moment. "You guys just opened a new era," he said.
Afterward, he pulled up the voice notes app on his phone.
"What can I say?" he murmured into the microphone. "Science - it's not well paid. It has a lot of problems. But it's so fulfilling."
Schaefer thought of the bedrock that Balter-Kennedy described to him: gorgeous cylinders of pale gray quartz and glittering chunks of garnet. These were their "moon rocks," he said - the first material from an unexplored landscape.
It seemed fitting that the project's youngest scientists - Balter-Kennedy and Walcott - oversaw the breakthrough. They had poured so much of themselves into this experiment. Their careers, and their lives, would be shaped by what was learned.
And now that GreenDrill had proven it was possible, the next generation of researchers would be able to collect even more samples from underneath the ice. They could peer into history no human had witnessed. They could start asking the questions that only rocks can answer.
What they find will almost certainly be frightening, Schaefer knew. It will shed new light on the dangers facing humanity. It will highlight the urgency of tackling problems science alone can't solve: how to transition away from polluting fossil fuels, how to protect vulnerable people from climate disasters like sea level rise. There was far more work to be done.
But for now, in the darkness of his apartment, he simply basked in the joy of discovery.
"It all worked out," he said, his voice slurred by tears and exhaustion. "And the entire, the entire -" he paused. "It was worth it."
Sarah Kaplan and Bonnie Jo Mount traveled to a remote field camp on Prudhoe Dome, in the northwestern corner of the Greenland ice sheet to report this story.