Antarctica Is Melting, and Giant Ice Cracks Are Just the Start

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. 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 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. That makes it especially vulnerable to the warming ocean. 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.

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. They themselves don’t add much to sea level, because they’re already floating in the water. But as they weaken, the glaciers behind them flow faster to the sea, and their edges retreat. That’s happening now all around the Amundsen Sea. 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. But even more worrisome is the neighboring Thwaites Glacier, which could destabilize most of the West Antarctic Ice Sheet if it collapsed.

Full story at http://on.natgeo.com/2sjv4Oe

Source: http://nationalgeographic.com

 

 

 

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