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Support Brackets Won’t Help These Weakening Shelves

by Michael D. Lemonick

Most people have undoubtedly heard by now that a significant factor in sea-level rise over the next century is likely to be the dwindling of massive ice caps on Greenland and Antarctica.

Most also undoubtedly think it all has to do with the ice melting — which makes perfect sense, since the most basic feature of climate change is a rise in average global temperature.

But what makes sense isn’t necessarily true. In fact, a significant factor in ice loss is that tidewater glaciers have started flowing into the sea faster than they have in the past. The ice is dropping into the ocean, like ice cubes added to a glass of water: the water level rises immediately, without waiting for the ice to melt.

One major reason the glaciers are flowing faster is that the ends sticking out into the sea are being warmed by ocean currents — and as the ends start to melt, they let the rest of the glacier flow more quickly. One report on this phenomenon is based on observations by the ICESat satellite and another comes from the Woods Hole Oceanographic Institution.

Now the US Geological Survey has weighed in with a major study on the ice shelves that sit at the southern end of the Antarctic Peninsula. Ice shelves are huge slabs of ice that form where ice from glaciers on land flows out onto the sea (they’re so thick that they often grind on the sea bottom). Like their cousins in other parts of the world, including more northerly areas of the Antarctic Peninsula, these shelves are weakening and retreating as ocean temperatures rise and currents shift — and that will likely take the brakes of glaciers here as well, letting them drop giant ice cubes into the ocean.

As with much of climate-change research, one study in isolation doesn’t mean a lot. But taken together with the earlier observations, it suggests a worldwide trend in the direction of rising seas.


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