How Explosives, a Robot, and a Sled Expose a Doomsday Glacier

Two Decembers ago, Erin Pettit layered up, slapped on goggles, cued up an audio book, and went on a hike—across Thwaites Glacier in Antarctica. Behind her, she dragged a sled loaded with a ground-penetrating radar, which fired pulses through a thousand feet of ice and analyzed the radio waves that bounced off the seawater below, thus building a detailed image of the glacier beneath her feet. Pettit—a glaciologist and climate scientist at Oregon State University—hiked alone through the snow, sometimes eschewing headphones for the absolute auditory stillness of the most remote landscape on Earth. “It was actually kind of an amazing, meditative field season,” she says, “I just bundled up, I went out there and pulled my sled, and just walked for miles and miles.”In case you were worried, her colleagues always knew where Pettit was; every so often someone would roll out on a snow machine to bring her supplies or to swap out the radar’s battery. Sure, the team could have covered more ground by towing the radar behind the vehicle, but the vibrations would have introduced noise to the data. And by walking slowly, Pettit could maximize the resolution of the radar images. Every night, she’d return to camp, download that data, and begin to parse it. “And then the next day, I would go out and do the same thing—walk this peaceful, quiet walk,” says Pettit. She hiked up to 12 miles each day for over two weeks, for a total of 135 miles. “I was thinking: I'm walking on top of 300, 400 meters of ice that's on top of the ocean, and on this piece of ice that was unlikely to be there for much longer.”That’s because Thwaites—aka the Doomsday Glacier—is deteriorating fast, losing 50 billion tons of ice to the sea each year. Stretching 75 miles across the coast of Antarctica, encompassing an area about the size of Florida, it’s currently responsible for 4 percent of global sea level rise. (It straddles land and sea: The bit on land is known as an “ice sheet,” but where it floats it’s an “ice shelf.”) If it melted completely, the glacier would not only contribute over 2 feet of sea level rise, but as it slid into the ocean, it would also tug on the glaciers surrounding it, further destabilizing them. That’d add another 8 feet of sea level rise.Scientists are racing to understand how Thwaites is disintegrating, and to figure out how much time humanity has before the thing causes disastrous sea level rise. The ice shelf could crumble in three to five years, which will dramatically accelerate the decline of the rest of the glacier. Each new satellite image of Thwaites shows deeper and longer fractures that are growing up to 6 miles a year, and they’re heading toward thinner ice.

Erin Pettit leaves camp with a ground-penetrating radar in tow Photograph: Karen Alley