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Oct 01, 2023

What Arctic ice in Greenland tells us about climate change

Standing atop of the Greenland ice sheet, it was easy to feel as though the whole world was frozen. The glittering, white expanse stretched as far as I could see in every direction, its windswept

Standing atop of the Greenland ice sheet, it was easy to feel as though the whole world was frozen. The glittering, white expanse stretched as far as I could see in every direction, its windswept surface rippling like the ocean.

But I knew the landscape is actually incredibly vulnerable as the planet warms. Each year, NASA analyses show, Greenland loses an average 270 gigatons of ice — enough to fill about 10 million Olympic swimming pools. Scientists say the loss will only accelerate as human-caused pollution continues to heat the planet.

I traveled to this remote corner of the ice sheet this spring alongside a team of scientists who were trying to figure out exactly how much trouble Greenland is in. They camped for two months in subzero conditions while attempting to drill through more than 1,600 feet of ice. Their goal: to uncover rocks from underneath the ice sheet that could tell them about the last time Greenland completely melted — and when that might happen again.

Here’s why that work is so important to the future of the world:

Average temperatures in the Arctic are already 3 degrees Celsius (5.4 degrees Fahrenheit) warmer than they were in 1979, according to a study published last year in the journal Nature. That increase is 4 times greater than the global average for the same time frame.

Scientists say this rapid warming is the result of a feedback loop known as “Arctic amplification,” caused by dwindling ice on the sea surface.

When the surface of the ocean is frozen, the bright white sea ice reflects most of the sunlight that hits it, sending two-thirds of that radiation back into space. Yet as warming waters and rising air temperatures cause sea ice to melt, more incoming sunlight is absorbed by the dark ocean surface. This warms up the water, preventing the growth of sea ice, which means the ocean gets even hotter.

Relative to the 1981-2010 average, the Arctic has lost 595,000 square miles of sea ice — enough to fill the area of Texas, California, Colorado and New York combined. Sea ice also forms later in the autumn and vanishes earlier in the spring. This loss doesn’t only accelerate warming; it harms the people and animals who depend on sea ice to survive. When I was in Greenland, I spoke with residents of the remote northern town of Qaanaaq, who said that dwindling sea ice left them without a stable platform from which they could hunt and fish.

Vanishing land ice — such as ice sheets and glaciers — can also create a feedback loop. But because land isn’t quite as dark as the surface of the ocean, it doesn’t cause as much additional heating. This is partly why the South Pole (which is covered by the Antarctic continent) isn’t warming as fast as the North Pole (which is surrounded by ocean). Antarctica is also protected by the vast, frigid Southern Ocean, and it’s buffered by weather patterns that prevent masses of hot air from intruding over the frozen continent.

Melting sea ice doesn’t contribute to sea level rise, because it is already in the ocean. Think of an ice cube floating in a glass of water — the amount of water it displaces while frozen is roughly equal to the amount of liquid it adds as it melts, so the overall water level doesn’t change.

But the Arctic amplification that results from vanishing sea ice signals deep trouble for the ice that’s on land — particularly the Greenland ice sheet. The warming ocean seeps underneath the ice and melts it from below. Higher air temperatures also lead to increased melting on the surface; earlier this summer, several pulses of warm air caused melting across more than 300,000 square miles of the ice sheet.

When all that land ice melts, its flows into the ocean, raising sea levels by about three-quarters of a millimeter per year. Greenland is losing mass at twice the pace of Antarctica, according to the Intergovernmental Panel on Climate Change.

Joerg Schaefer, a climate geochemist at the Lamont Doherty Earth Observatory and the lead investigator for the drilling project I wrote about, called the Greenland ice sheet “the sickest patient in the climate system.”

A few inches of sea level rise might not sound like a lot, but coastal communities are already experiencing the consequences. Rising oceans can deluge infrastructure and overwhelm neighborhoods even when no rain is falling; a recent National Oceanic and Atmospheric Administration report found that “sunny day flooding” has doubled in the United States in the past two decades. Saltwater is percolating into underground water reserves, killing forests and poisoning farm fields from North Carolina to Bangladesh. One study found that higher average sea levels around New York caused flooding from Hurricane Sandy to reach farther inland and affect 70,000 additional people, adding $8 billion to the cost of the storm.

And melting from Greenland is on track to get a lot worse. Even if the world stopped emitting greenhouse gases today, a study published last year found the ice sheet will lose more than 110 trillion tons of ice by 2100 — triggering nearly a foot of global sea level rise. And in the worst case warming scenarios, newer climate models suggest Greenland alone could cause an additional seven inches of sea level rise by the end of the century. That much melting would swamp New York, deluge Miami and could wipe entire island nations off the map.

Almost a decade ago, Schaefer and GreenDrill’s co-director, University at Buffalo geologist Jason Briner, got a rare chance to analyze a rock sample that had been extracted from underneath the thickest part of the Greenland ice sheet. They found that the rock had been exposed to sunlight within the last 1.1 million years — which meant that, under climate conditions not so different from the ones we live in now, Greenland was almost completely ice-free.

Right now, Greenland contains enough ice to raise sea levels by about 24 feet. A complete remelting of the ice sheet is not going to happen in our lifetimes, but the potential consequences for future generations would be catastrophic. According to an analysis by Climate Central, that much sea level rise would erase 440,000 square miles of land where more than 375 million people currently live. The National Mall would be underwater. Shanghai, Amsterdam and the entire bottom half of Florida would vanish.

But direct observations and computer models alone can’t precisely predict how much Greenland will melt as a result of modern climate change.

“Some models say that north Greenland melts a lot” when the planet gets warm, Briner told me. And some models say, ‘No, no, no, north Greenland is really robust — that’s a survivor up there.”

GreenDrill — the project that brought the Schaefer and Briner (and me) to the top of the ice sheet — aimed to clear up that uncertainty by analyzing Greenland’s bedrock for clues about its behavior in the past.

Rocks that have been buried by ice sheets bear chemical signatures of the last time they saw sunlight. By collecting material from different parts of Greenland, the GreenDrill team hopes to identify which parts of the ice sheet vanish first when temperatures start to rise. Their findings can help improve the models that scientists use to forecast how Greenland will melt amid human-caused warming — and what that means for how much sea levels will rise.

“You can read these records almost like a history book,” said Allie Balter-Kennedy, a glacial geologist at Lamont Doherty and another member of the GreenDrill team. “It’s important for knowing about Earth’s history, but hopefully even more important for projecting into the future.”

Extracting those crucial bedrock samples from underneath the ice took millions of dollars and a team of 12 scientists and engineers. Some, like lead driller Tanner Kuhl of the U.S. ice drilling program, were top experts in their fields. Others, like Balter-Kennedy and University at Buffalo PhD student Caleb Walcott, were promising scientists at the very beginnings of their careers. Together, they journeyed to remote field camps on the ice sheet to accomplish a task that had never been done before.

“I am just constantly impressed by the human quality of this team,” Schaefer said.

For more than a month, GreenDrill team members slept on cots in unheated tents and cooked their meals on propane stoves. All their drinking water had to be melted down from snow. They couldn’t shower or make phone calls. Even though the sun shone 24 hours a day, the temperature rarely rose above 0 degrees Fahrenheit.

Reaching the remote location was its own logistical adventure. It took four flights on commercial airlines and a helicopter ride arranged by the U.S. National Science Foundation for photojournalist Bonnie Jo Mount and me to reach the GreenDrill field camp for our reporting this spring. An unseasonable blizzard delayed our arrival on the ice sheet by almost a week.

While we waited in town for the weather to clear, the scientists on the ice sheet were dealing with blowing snow and 50 mile-per-hour gusts — plus a crack in the ice that jeopardized the whole experiment. One of the drill sites was on a slope, and Briner recalled how frigid winds would stream off the ice, threatening to blow their tents away.

“It was a little terrifying,” Briner said. “But for every challenge and every freak out I might have when I’m in a bad storm, there’s just as many rewards. … It’s inspiring to be working in such pristine, dramatic, striking landscapes.”

Yet during my three days on the ice sheet, I saw just how much determination it takes to work in these harsh conditions. Machines are less effective and break more easily in the cold. Batteries die faster. Every task takes longer, because it has to be done while wearing clumsy gloves or with numb fingers. The simple act of getting dressed in the morning turned into an ordeal, as I piled on layers of long underwear, then a sweater and fleece pants, then ski pants and a puffy jacket that made me look like the Pillsbury Dough Boy.

There’s a reason scientists have never before tried to extract multiple bedrock samples from beneath more than 1,000 feet of ice, Schaefer told me: “It’s really not easy.”

But he said the project was worth the risk, because people need to know how much the ice sheet may melt as the planet continues to warm.

“The Greenland ice sheet is probably patient number one in the climate system,” Schaefer said. And GreenDrill is “basically a biopsy” that will reveal how much trouble the ice sheet is in.