When they do, more warm water ends up near the edge of the ice sheet, which means more ice melts away. Sometimes, those winds-cousins of the famous raging band of Southern Ocean winds known as the Roaring 40s-slacken or even reverse. The main thing that controls whether warm water makes it to the edge of the ice sheet, it turns out, is the strength of the winds a little bit farther offshore, in the heart of the icy, bitter Amundsen Sea. Stunning drone footage shows how an iceberg the size of Houston, Texas is holding on by a thread. Over decades, the temperature of the water has waxed and waned, driven in part by natural climate cycles that send different water masses close to the edge of the ice sheet at different times, cycling through from cold to a little less cold every five years or so. Just how warm the ocean is, though, matters a lot. The glaciers have been receding because their snouts spill over the edge of the continent into the surrounding ocean, which is warmer than the ice. ( See what a 10 billion ton chunk of ice looks like in this video). Pine Island Glacier and Thwaites Glaciers, for example, are losing about 100 billion tons of ice each year, and more in bad years. In the past decades, some glaciers in the region have been retreating shockingly quickly. That’s not likely to happen anytime particularly soon, scientists think, but some parts of the ice sheet are particularly vulnerable, in danger of crossing a crucial “tipping point” if they retreat too far. If it all melted away, global sea levels would rise by about 10 feet or more. The massive West Antarctic ice sheet holds something like 6 percent of the world’s fresh water frozen in its guts. “We now have evidence to support that human activities have influenced the sea level rise we’ve seen from West Antarctica,” says lead author Paul Holland, a polar scientist at the British Antarctic Survey. Sometimes, those winds have weakened or reversed, which in turn causes changes in the ocean water that laps up against the ice in a way that caused the glaciers to melt. In a study published Monday in Nature Geoscience, a team of scientists showed that over the past century, human-driven global warming has changed the character of the winds that blow over the ocean near some of the most fragile glaciers in West Antarctica. Now, a team has unraveled evidence of that human influence. But while the science was clear that human influences on climate would affect the ice down the line, it has been hard to tell whether human-driven global warming has affected the melting already underway. Their collapse could send sea levels up by at least a foot by 2100-and potentially much more.įor years, scientists have watched and learned that those glaciers are crumbling and melting, the rate speeding up over the decades and imperiling the stability of the entire ice sheet. The towering glaciers of West Antarctica hold the fate of the world’s coasts in their flanks.
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