According to a new study published in the journal Nature Geoscience, rapidly-thawing permafrost in the Arctic is causing sinkholes in a process called thermokarst. “That’s the land that gets ravaged whenever permafrost thaws rapidly,” reports Wired. “As the ice that holds the soil together disappears, hillsides collapse and massive sinkholes open up.” From the report: Today in the journal Nature Geoscience, researchers argue that without taking abrupt thaws into account, we’re underestimating the impact of permafrost thaw by 50 percent. “The amount of carbon coming off that very narrow amount of abrupt thaw in the landscape, that small area, is still large enough to double the climate consequences and the permafrost carbon feedback,” says study lead author Merritt Turetsky, of the University of Guelph and University of Colorado Boulder. Less than 20 percent of northern permafrost land is susceptible to this kind of rapid thaw. Some permafrost is simply frozen rock, or even sand. But the kind we’re worried about here contains a whole lot of water. “Where permafrost tends to be lake sediment or organic soils, the type of earth material that can hold a lot of water, these are like sponges on the landscape,” says Turetsky. “When you have thaw, we see really dynamic and rapid changes.”
That’s because frozen water takes up more space than liquid water. When permafrost thaws, it loses a good amount of its volume. Think of it like thawing ice cubes made of water and muck: If you defrost the tray, the greenery will sink to the bottom and settle. “That’s exactly what happens in these ecosystems when the permafrost has a lot of ice in it and it thaws,รข says Turetsky. “Whatever was at the surface just slumps right down to the bottom. So you get these pits on the land, sometimes meters deep. They’re like sinkholes developing in the land.” “Essentially, we’re taking terra firma and making it terra soupy,” Turetsky adds. […] When these lands thaw, they play host to a number of processes. As ice turns to liquid water, trees flood and die off. Thus more light reaches the soil, further accelerating thawing. This is in contrast to gradual thaw, when the plant community largely stays the same as the ice thaws. Defrosted soil at the surface gets thicker and thicker, but it doesn’t catastrophically collapse.
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Source: Slashdot – Permafrost Is Thawing So Fast, It’s Gouging Holes In the Arctic