11/16/2023 0 Comments Antarctic ice shelf breaking off![]() ![]() During their five weeks of studying it, the ice under their boots thinned by another seven feet. Each morning they saw new cracks, an inch wide and seemingly bottomless, cutting across its surface. But Truffer’s team wanted to bore holes all the way through the ice shelf, so they could measure the heat eating at it from the seawater below.Īs the researchers lay in their tents at night, in the middle of a 4,000-mile arc of coastline that lacked a single permanent outpost, they heard loud pops and bangs coming from the ice. The ice had long been considered too dangerous to visit. Their plan was to spend two months on the ice shelf they would be the first humans to spend even a single night. The team, led by glaciologist Martin Truffer of the University of Alaska, proceeded to set up camp. Photograph by Laurent Ballestaįinally the scout was satisfied: There were no buried crevasses that might swallow a landing party. The brown patches above are microalgae, which cling to sea ice and photosynthesize in the spring. Tethered to the plane by a rope and harness, he probed the snow with an eight-foot rod.Ī diver watches an emperor penguin as it swims nearby. After the plane landed, a single person disembarked. The pilot dragged the plane’s skis through the snow, then lifted off and circled back to make sure he hadn’t uncovered any crevasses. In December 2012 a red-and-white Twin Otter plane skimmed low over the Pine Island Ice Shelf. Getting the predictions right requires measurements that can be made only by going to the ice. “But we have to be careful not to waste too much time doing that.” ![]() “We have to get these numbers right,” Rignot says. The question is whether it will take 500 years or fewer than a hundred-and whether humanity will have time to prepare. Rignot has studied the region for more than two decades, using radar from aircraft and satellites, and he believes the collapse of the West Antarctic Ice Sheet is only a matter of time. “These are the fastest retreating glaciers on the face of the Earth,” says Eric Rignot, a glaciologist at the NASA Jet Propulsion Laboratory in Pasadena, California. But even more worrisome is the neighboring Thwaites Glacier, which could destabilize most of the West Antarctic Ice Sheet if it collapsed. The Pine Island Ice Shelf, about 1,300 feet thick over most of its area, is a dramatic case: It thinned by an average of 150 feet from 1994 to 2012. That’s happening now all around the Amundsen Sea. But as they weaken, the glaciers behind them flow faster to the sea, and their edges retreat. They themselves don’t add much to sea level, because they’re already floating in the water. The ice sheet is held back only by its fringing ice shelves-and those floating dams, braced against isolated mountains and ridges of rock around the edges of the basin, are starting to fail. If all that vulnerable ice were to become unmoored, break into pieces, and float away, as researchers increasingly believe it might, it would raise sea level by roughly 10 feet, drowning coasts around the world. That makes it especially vulnerable to the warming ocean. The ice sheet is draped over a series of islands, but most of it rests on the floor of a basin that dips more than 5,000 feet below sea level. Together they drain a much larger dome of ice called the West Antarctic Ice Sheet, which is up to two and a half miles thick and covers an area twice the size of Texas. The Pine Island Ice Shelf is the floating terminus of the Pine Island Glacier, one of several large glaciers that empty into the Amundsen Sea. See the Giant Crack in Larsen C Ice Shelf That Yielded Antarctica Iceberg But around the Amundsen Sea, a thousand miles to the southwest on the Pacific coast of Antarctica, the glaciers are far larger and the stakes far higher. That’s why a Delaware-size iceberg just broke off the Larsen C Ice Shelf and why smaller ice shelves on the peninsula have long since disintegrated entirely into the waters of the Weddell Sea. On the Antarctic Peninsula, the warming has been far greater-nearly five degrees on average. ![]() The water there has warmed by more than a degree Fahrenheit over the past few decades, and the rate at which ice is melting and calving has quadrupled. In 20 a 225-square-mile chunk of it broke off the end and drifted away on the Amundsen Sea. Its edges are shredded by rifts a quarter mile across. Its buckled surface is scarred by thousands of large crevasses. Seen from above, the Pine Island Ice Shelf is a slow-motion train wreck. It was first published on Jand updated on July 12 with news of the Larsen C break. This story appears in the July 2017 issue of National Geographic magazine. ![]()
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