National Geographic : 2017 Jul
48 national geographic • july 2017 glacier is already losing a couple of cubic miles of ice per year—small potatoes, in Antarctic terms. But Donald Blankenship, a University of Texas glaciologist who oversees the aerial survey, fears it could blow up. In 2016 his team reported evidence from the bedrock that Totten repeatedly has retreated 100 to 200 miles inland from its current position— meaning it might help explain why sea level was This past January a twin-propeller DC-3 made a series of flights from Australia’s Casey Station along the East Antarctic coast. Built in 1944, the plane was packed with modern scientific equipment. As it flew over the Totten Glacier, a radar recorded the thickness of the ice. Anoth- er instrument recorded tiny changes in Earth’s gravitational field—clues to the topography of the seafloor under the glacier’s floating ice shelf. Now and then a crew member opened the plane’s rear door, knelt in the windy opening, and tossed out a torpedo-shaped object. As the device splashed into the water, it split in two: One part floated, sending radio signals back to the plane, while the other part reeled down 2,600 feet of wire, measuring the water temperature all the way down. Until recently the East Antarctic Ice Sheet was considered secure; unlike West Antarctica, it sits on high ground. But mapping with ice- penetrating radar has revealed a low-lying re- gion cut by glacially carved channels that drop as far as 8,500 feet below sea level—perfect for guiding warm ocean water deep into the heart of the ice sheet. The Totten Glacier is the largest coastal outlet in this region. If it collapsed, global sea level could rise 13 feet—“roughly as much as all of West Antarctica,” Rignot points out. “One glacier alone.” In January 2015, the Australian icebreaker Au- rora Australis became the first ship to reach the front of Totten. Like the Palmer at Pine Island in 1994, it found deep, warm water flowing under the ice shelf, at a rate of 4.5 cubic miles a day. The If Totten Glacier were to collapse, sea level could rise 13 feet—threatening many of the world’s largest cities.