'Upside-Down Rivers' of Warm Water Are Carving Antarctica to Pieces

By Brandon Specktor - Senior Writer 5 hours ago

Antarctica's ice shelves are under attack at their most vulnerable points.




On Antarctica's East Getz Ice Shelf, monstrous fractures seem to form in the same places year after year. A new study suggests this reliable breakage may be the effect of underwater "rivers" of hot, buoyant water attacking the ice shelf's most vulnerable points.(Image: © Karen Alley/The College of Wooster and NASA MODIS/MODIS Antarctic Ice Shelf Image Archive at the National Snow and Ice Data Center, CU Boulder.)


Earth's frozen places are losing ground fast. In Antarctica, melted ice spills into the ocean at rate of about 155 billion tons (140 billion metric tons) per year — an amount so confoundingly huge that it's easier just to call it "chilling" and "unprecedented," as a recent U.N. report did. Those numbers will only increase as humans continue polluting the air with record amounts of heat-trapping greenhouse gases.

On the frontlines of this warm-weather siege are the world's ice shelves. Perched all around the edges of Antarctica and Greenland, ice shelves help stem the tide of melting glaciers by growing outward over the ocean like thick balconies of frost. Nearly 600,000 square miles (1.5 million square kilometers) of ice shelves surround Antarctica alone, through which 80% of the continent's melting ice passes. However, a new study suggests, those dams of ice may have a fatal flaw in the face of Earth's increasingly warming oceans.

In a study published yesterday (Oct. 9) in the journal Science Advances, researchers used satellite imagery to look at Antarctica's shear margins — fragile areas near the edges of ice shelves where huge cracks tend to spread — and found a troubling pattern. Certain cracks seemed to emerge in the same spots year after year, often stretching clear across the tips of their ice shelves and carving huge chunks into the sea. These cracks were often accompanied by long, sagging troughs and large holes in the ice — suggesting that some natural force under the shelves is causing the same regions to buckle and break every year.

According to Karen Alley, lead author of the new study, it appears that vast currents of warm, buoyant water are carving "upside-down rivers" into the bottoms of the ice shelves, nibbling away at their already weak edges.

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