![]() If the shelf were to fall apart, the glacier’s slide into the sea would greatly accelerate. The ice shelf acts as a dam, slowing its parent glacier’s flow into the ocean. The decline has caused widespread alarm because experts have long viewed the Thwaites Glacier as the most vulnerable part of the larger West Antarctic Ice Sheet. For the past 20 years, as the planet has warmed, scientists using satellites and aerial surveys have been watching the Thwaites Ice Shelf deteriorate. The shelf is a floating slab of ice, several hundred meters thick, extending roughly 50 kilometers into the Southern Ocean, covering between 800 and 1,000 square kilometers. The Thwaites Ice Shelf begins where the massive Thwaites Glacier meets the West Antarctic coast. But it isn’t, Pettit says: “There are five or six different ways this thing could fall apart.” In satellite images, the center of the ice shelf looks stable. It meant that the ice’s underside was a rolling landscape-not what anyone expected. To Pettit, a glaciologist at Oregon State University in Corvallis, this was significant. When it does, the rest of the West Antarctic Ice Sheet behind it could flow right into the ocean, pushing up sea levels around the planet, flooding coastal cities worldwide.įrom a distance, the ice shelf looks flat, but as Pettit walked she saw the guide flags ahead of her rise and fall against the horizon-a sign that she was walking across an undulating surface. Pettit was studying defects within the ice, akin to hidden cracks in an enormous dam, that will determine when the ice shelf might crumble. But if that were the case, Pettit wouldn’t have been there. ![]() ![]() The Thwaites Ice Shelf appeared healthy on the surface. A row of red and green nylon flags, flapping in the wind on bamboo poles, extended into the distance, marking a safe route free of hidden, deadly crevasses. Pettit was surveying a part of Antarctica where, until several days before, no other human had ever stepped. The brittle snow crunched like cornflakes underneath her boots-evidence that it had recently melted and refrozen following a series of warm summer days. How imminently such a scenario could come to pass is unclear.įinally, while there is disagreement among scientists about climate change’s role in Larsen C’s breaking off, there is little doubt that unchecked manmade warming will, eventually, pose a significant threat to the continent’s ice shelves - and, thus, to the world’s coastal cities.On December 26, 2019, Erin Pettit trudged across a plain of glaring snow and ice, dragging an ice-penetrating radar unit the size of a large suitcase on a red plastic sled behind her. Were they to collapse, uncorked land ice could move (relatively) rapidly toward the ocean, raising sea levels by many feet (the collapse of the entire Western Antarctic Ice Sheet, alone, could raise sea levels by ten feet). In other parts of Antarctica, similar ice shelves are holding back enormous glaciers. While its demise is not, by itself, a catastrophe, it could portend one. And remember, in Mercer’s prophecy, Larsen C is the canary in the coal mine. Adrian Luckman, professor of glaciology at Swansea University, told The Guardian that recent data suggests most of the shelf’s ice has actually been thickening.Īs for the bad news: Some scientists maintain the climate change played a role. But natural variability may be sufficient to explain the mere splitting off of a large chunk of Larsen C. Scientists broadly accept that climate change played a role in the disintegration of Larsen A and B. Icebergs have been breaking off of ice shelves for millions of years. What’s more, it’s far from clear that this event is primarily the product of climate change. But even if it does, it’s not going to have a calamitous impact on sea levels, in and of itself. It’s far from certain that this week’s splitting off will result in the total collapse of Larsen C, as some scientists believe it could still regrow. But Larsen A, B, and C, were all holding back relatively little land ice. Remove the ice shelves, and those glaciers will flow out to sea, and raise sea levels. It’s true that the worry with ice shelves is generally about delayed impact: These masses of ice act as corks keeping Antartica’s glaciers bottled up on land. Let’s start with the good news: Larsen C was already floating before it was separated, and so its breaking off will have no immediate impact on sea levels. But there is also reason to view it as a fulfillment of Mercer’s dark prophecy. There’s reason to think this development is less ominous than it may sound.
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