Greenland's thaw melts a climate-change skeptic

PETERMANN ICE SHELF, Greenland – Half a decade before he took this trip to the farthest reaches of the north, Andreas Muenchow had his doubts about whether warming temperatures were causing one of the world's great platforms of ice to melt and fall apart.

He even stood before Congress in 2010 and balked on whether climate change might have caused a mammoth chunk of ice, four times the size of Manhattan, to break off from this floating, 300-square-mile shelf. The University of Delaware oceanographer said he wasn't sure. He needed more evidence.

But then the Petermann Ice Shelf lost another two Manhattans of ice in 2012, and Muenchow decided to see for himself, launching a project to study the ice shelf intensively.

He was back again in late August, no longer a skeptic. It was hard not to be a believer here at 81 degrees north latitude, where Greenland and Canada very nearly touch. The surface of the bumpy and misshapen ice was covered with pools and puddles, in some cases frozen over but with piercing blue water beneath. Streams carved through the vast shelf, swelling into larger ponds or even small lakes.

The meltwater was a sign the ice shelf was growing more fragile, moving closer to the day when it might give up more city-size chunks of ice.

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The Petermann Ice Shelf serves as a plug of sorts to one of Greenland's largest glaciers, lodged in a fjord that, from the height of its mountain walls down to the lowest point of the seafloor, is deeper than the Grand Canyon. There's enough ice piled up behind Petermann to raise oceans globally by nearly a foot someday.

The question for Muenchow is no longer whether Petermann is changing – it's how fast it could give up still more ice to the seas. That's why he and British Antarctic Survey colleague Keith Nicholls ventured here by helicopter to take the measure of the Petermann shelf, which had been shifting and surging in a way that damaged the scientific instruments they had left behind a year earlier – behaving as though it didn't want to be known.

Greenland is the largest island on Earth and home to its second-largest ice sheet after East Antarctica. It's pouring 281 billion tons of that ice into the ocean each year, a major contribution to rising seas. Much of the loss comes from some 200 outlet glaciers, which extend out to the sea like fingers of the larger ice sheet.

The great fear is that Greenland's ice loss is accelerating, and that's why much attention has been directed at Petermann. One expert has called it one of the island's three major "floodgates," and the only one that has not yet opened. In part, the Petermann Ice Shelf has been slower to disintegrate simply because it is in a much colder place.

But that is beginning to change, and Muenchow and Nicholls are trying to understand the mechanics of how it might break apart.

They are old-school scientists, focused on gathering hard data in the world's most remote places. Each has a "great record in terms of publications," says Marco Tedesco, a Greenland researcher at Columbia University's Lamont-Doherty Earth Observatory.

Muenchow, who was born in Germany, traveled to the United States to pursue oceanography and got his Ph.D. studying the Delaware River. But before long he became infatuated with the idea of probing places that few have reached before, despite the hardships of leaving family and the comforts of home. The search took him five times to the Nares Strait, a tiny ocean passageway between northwest Greenland and Canada near Petermann Glacier.

"To me, this hardship is pleasure as it always shatters prior expectations," he explained later. "The only constant, it feels, is change and new insights. This drives me. Perhaps I am addicted to it. . . . The field work gives me this chance or opportunity to 'reset' and take a new look at what I thought I knew or I knew I did not understand."

Nicholls, meanwhile, is an expert in his own sort of extreme pursuit – using hot water to drill holes hundreds of feet through the enormous ice shelves of Antarctica and now Greenland, and then analyzing data from the ocean beneath them.

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They first worked together in 2015 as part of a major National Science Foundation-sponsored ship voyage to Petermann, where Muenchow was taking ocean measurements and Nicholls was busy drilling through the ice. Now, they had returned as part of a much smaller mission to recover data and determine why their instruments had gone dead. Two Washington Post journalists accompanied them with the support of the foundation which, in keeping with its policies, provided transportation and accommodations.

Their expedition began a day earlier from the United States' Thule Air Base and the small village of Qaanaaq, Greenland's most northern permanent settlement. This time they sought to reach Petermann by helicopter. The 300-mile journey was so long they had to break it in stages, picking up fuel from caches they strategically placed a year earlier when they had visited aboard a foundation-supported icebreaker.

As they crossed the desolate landscape, their Air Greenland chopper finally emerged from a series of inland canyons into the air above the ice shelf, which was streaked with thick veins of blue ice amid a sea of white, the landscape covered with meltwater pools. It was as though a fly had suddenly buzzed in through the window of a cathedral. The ice shelf was its sprawling floor, and it was rimmed on either side by enormous, symmetrical mountain walls sculpted into shapes resembling flying buttresses.

Along the shelf's central aisle ran one of Petermann's most distinctive features – a 30-mile-long meltwater river. A year ago, Muenchow and Nicholls had established three scientific data-collection stations on its banks – drilling through the football-field-thick ice and extending ocean sensors, attached to a long cable, into the dark and half-mile-deep waters beneath the shelf. These were to detect whether warming ocean water was causing a double-whammy of damage to Petermann by melting it from below, even as the warm air temperatures melt it from above.

But the main station had stopped feeding back any data in February. Now, Muenchow and Nicholls were here to see what had happened.

Muenchow sat in the second row of seats in the helicopter with earphones on to muffle the noise.

His chief fear, he had explained before the trip, was that this might just be a mop-up mission: That the flowing ice might have damaged the stations beyond repair, snapping the cables extending into the ocean below, and that there would be no data to retrieve.

Muenchow said he had prepared himself to be devastated if the data was lost. But he said he would give himself about "15 minutes" to mourn before adjusting to see what could be salvaged.

As nervous as he was about their equipment, Muenchow was much more in his element here than he had been in 2010, testifying before Congress. Then, Muenchow's scientific caution and compunction for rigor didn't translate very well for a political audience.

Petermann glacier had just lost a chunk of its ice shelf, and NASA satellite images of the enormous ice "island" were circulating widely. At the hearing, Jay Inslee (D), then a congressman and now the governor of Washington, pressed Muenchow to be more outspoken about what was happening to the planet. The scientist demurred.

The evidence "does not conclusively prove that this specific event is global warming," Muenchow testified. The logic was simple – breaking off large pieces might just be something Petermann glacier does occasionally, if you go back far enough in time.

But two years later, another vast island of ice cleaved from Petermann. That's when Muenchow began to change his mind. The shelf had by then lost 23 miles of its prior length, reaching a record low in size.

"It's two extreme events in six years, so something is happening," Muenchow said.

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In science – unlike in politics – being hesitant when you don't know something, and being willing to change your mind in the face of new evidence, are virtues. He has since joined a growing wave of researchers working to learn more.

Climate change doubters have continued to suggest – from a distance – that Petermann's huge ice losses are just normal glacier behavior. Muenchow himself, no dogmatist about the matter, can still entertain the case for skepticism, in part because the glacier has never been as well observed as it now, by scientists and satellites. Conceivably, it lost as much ice during previous periods as it has lost in the present. Muenchow doubts that – the idea that the glacier has shifted to a new state, he says, is supported by the "preponderance of the evidence."

Petermann is looking suspicious again: At its front edge near the ocean, it features several additional cracks, including one that penetrates further toward the center than the others, arcing inward toward the central river and the shelf's thinnest region.

"I already see the beginning of a third break-up," Muenchow said.

When ice shelves break away, the ice that had once fed the shelf instead flows directly into the ocean, helping to raise sea levels throughout the world. In the case of Petermann, that plug runs about 30 miles in length, floating over the fjord, to a "grounding line." This is where the shelf ends and the ice touches the sea floor in 2,000-foot-deep waters. Farther back, the ice gets thicker and deeper.

Scientists worry about possible "marine ice sheet instability" in the region, which would allow warm ocean water to melt the base of the glacier and chase it backward – hastening its losses along the way.

It's not clear where the retreat would end. Oregon State University geologist Alan Mix said researchers have recently discovered that behind Petermann glacier lies an enormous, ancient canyon that is nearly 500 miles long and cuts all the way to the center of the Greenland ice sheet. It was probably carved by a river long ago.

So if the ice shelf collapses and Petermann glacier starts breaking off large icebergs and retreating backward, the ocean could someday gain access to this canyon.

"You can think about this as a huge drain of Greenland," Mix said of the Petermann fjord. "This is where the water gets out."

As the helicopter circled the researchers' central station, Nicholls spotted the non-responsive device first. Its weather beacon listed at a 30-degree angle, felled by the moving ice. That would explain why the station had not transmitted data in six months.

Nicholls turned to his partner in the helicopter and drew a finger across his neck in a sign recognized universally: dead.

Half an hour later, Muenchow was on the ice, busily using a hacksaw to cut through the weather station's steel pole to try to free it. "I'm making progress," he huffed, the temperatures at around 39 degrees in the early afternoon of an August day that, this far north, won't ever lose its light.

Muenchow retrieved a memory card and plugged it into his computer. It was the moment of truth.

And also, it turned out, one of pure scientific joy – the data was there, and the sensors were still recording more.

After realizing that the last recording was just a few hours old, Muenchow was speechless. He covered his mouth with his hands.

"That's good news," Nicholls deadpanned.

Muenchow started clapping softly.

It would take weeks, after the scientists got back home, to analyze the data. But they already knew it would give them an unprecedented image of the behavior of ocean waters in the deep cavity beneath the ice.

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There is still some mystery about how warm waters might be reaching and interacting with the Petermann Ice Shelf.

The Atlantic's warm, salty waters reach this fjord through a convoluted route that takes them north off Greenland's eastern coast, along a full circuit of the Arctic Ocean, and ultimately south through the Nares Strait. Here, warmer Atlantic-originating waters are found at the greatest depths because their saltiness gives them more density, while fresher and colder Arctic waters lie at the surface.

The warm waters then penetrate beneath the ice shelf and to the base of the glacier, and are somehow managing to melt and thin it at a rate of 30 to 40 feet per year. And the Atlantic waters in the area are getting still warmer over time.

But the fundamental question is what's pulling the Atlantic waters in and causing them to touch the shelf?

One key idea, Nicholls suspected, turns on all the wetness atop Petermann – a sign of ever-rising Arctic air temperatures. "Our major hypothesis," he said, is that some of this water is running off somehow, entering the ocean, and in the process, helping to draw in the warm water that causes the most extensive melting.

It isn't clear where the fresh water is spilling out, but it could be further up the fjord from here, at the grounding line. That would mean cold, fresh and buoyant water is suddenly pouring into warm, salty Atlantic-originating water at extreme, dark ocean depths. This interaction is probably very turbulent and dramatic, and it could be the key to growing melting.

"Because the base of the ice shelf is sloping upwards, this water flows quickly up the bottom of the ice shelf, and as it does that, it mixes and stirs in the warm water from beneath," said Nicholls.

This may help explain the most dramatic feature atop Petermann – its central river. It has a frozen surface in some areas, but flowing water underneath. It's noisy – constantly the source of cracking, crashing and sliding sounds. It's fed by a seemingly endless network of ice-banked tributaries that, amid above-freezing temperatures on the second day of the team's trip, were roaring with water.

But why is it here in the first place? The reason seems to be below the surface, where ocean waters have carved an undersea channel into the bottom of the shelf. That changes the surface of the shelf, too, because thinner ice won't float as high above the surface of the water. The result is a depression or chasm at the surface, which meltwater, flowing downhill, naturally fills.

This river, and the channel beneath it, seems implicated in the ice shelf's undoing. According to Muenchow, the previous major ice loss events seemed to occur whenever a crack in the shelf, coming in from the side, finally extends as far as the river.

After an intense 24 hours of work in near-freezing temperatures – tearing apart, rebuilding and reprogramming scientific stations, and consigning four out of nine ocean sensors to a watery oblivion – the researchers had one remaining quest to complete.

With their time on the ice dwindling, they wanted to install a radar that measures the ice's thickness roughly a mile from the main station. This would let them compare the shelf's thinning in different places.

The helicopter had dropped off equipment at the spot, but to save fuel and flying time, they decided to hike the distance, guided by a GPS device.

The hike was at a slight incline, out of Petermann's riverine depression and into higher terrain. At one point, the trek required crossing a small, flowing tributary. Nicholls used the long bamboo poles and drill bits he was carrying to test the opposite ice bank, making sure it provided a good foothold, before they did so.

After three hours of work, trouble arose. A cold rain had arrived, turning the ice treacherously slick. "The one thing you do not want is rain on an ice shelf," Nicholls said.

The water complicated the trip back to the helicopter. The team made it to within about a football field of the aircraft but could go no further, blocked by a rain-swollen series of streams flowing so fast that their roars were audible.

So with time running short before the pilots would start out to look for them, the researchers had to backtrack half a mile, where they found a crossing at higher ground.

Returning to the helicopter, they considered the expedition a success – while the scientists had to jettison two scientific stations, they repaired one and established another. Most of all, they retrieved key ocean data. But they acknowledge that in the vastness of the Petermann Ice Shelf, those are still just two small points taking measurements.

A month and a half later, as he was about to embark from Alaska on a research vessel bound for a different part of the Arctic, Muenchow told The Post what the data from beneath Petermann revealed.

A sensor in 3,000-foot-deep waters had found that in the warm, salty Atlantic layer, temperatures were even warmer than just a year earlier, in 2015. Those waters are likely flowing toward Petermann glacier's grounding line and helping to melt the shelf from below.

"The temperatures at the bottom end of the array continue to increase," said Muenchow. "It's getting warmer."

In a recent paper he and Nicholls pointed out that several other glaciers in Greenland have already lost their ice shelves. Their work suggests that Petermann is now following this path.