With enough evidence, even skepticism will thaw
As one of Greenland’s largest ice shelves shrinks, a once-doubtful scientist has come around to the role of climate change in melting it.
By Chris Mooney
Dec 30 2016
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.
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.
Hard data, hard to reach
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 PhD 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.