Over the last year or two, I've been seeing more articles about melting permafrost and how it releases methane into the atmosphere. Methane is a potent greenhouse gas that traps heat in the atmosphere about 20 times more than carbon dioxide. It isn't as persistent as CO2 but there is a lot of it trapped in permafrost in the arctic and antarctic.
You may have seen pictures of arctic buildings that are leaning or have collapsed because the permafrost under their foundations has melted. But there's also permafrost under the seafloor (submarine permafrost) and that is beginning to thaw as the ocean warms.
Yet submarine permafrost is largely unstudied, owing to its inaccessibility—renting out time on a research vessel is not cheap anywhere, much less in the Arctic, and it's much harder to reach for drilling samples. Now, in an alarming paper published last week in the Proceedings of the National Academy of Sciences, an international team of scientists give us a rare look at what’s going on down there. The team used oceanic robots, which look like torpedoes, off the coast of northern Canada and mapped the seafloor with sonar. The scientists repeated this several times over the course of nine years to get a sense of how the topology of the seafloor might be changing and found that it’s undergoing massive upheaval.
The result is the worrisome image shown above—a massive sinkhole indicating that the subsea permafrost has thawed and collapsed. This sinkhole is a giant among dozens of pockmarks the researchers found on the seafloor. Scientists have already documented this violent phenomenon, called thermokarst, on land. Because permafrost is made of soil suspended in a matrix of frozen water, when it thaws the land shrinks, gouging massive holes across the Arctic landscape. And as these images of the seafloor show, it’s also happening underwater.
“I think it's just absolutely remarkable that there are places on the seafloor where changes of this scale are happening at this rate,” says Monterey Bay Aquarium Research Institute marine geologist Charlie Paull, a coauthor on the paper. The entire survey covered an area that’s half the size of Manhattan and tallied 40 holes. (You can see a portion of the area in the image below.) The giant one, he says, “is equivalent to a whole New York City block composed of six-story apartment buildings.”
If you want a more visual exploration of the problem of melting permafrost releasing methane, watch the PBS Nova episode "Arctic Sinkholes".
Colossal explosions shake a remote corner of the Siberian tundra, leaving behind massive craters. In Alaska, a huge lake erupts with bubbles of inflammable gas. Scientists are discovering that these mystifying phenomena add up to a ticking time bomb, as long-frozen permafrost melts and releases vast amounts of methane, a potent greenhouse gas. What are the implications of these dramatic developments in the Arctic? Scientists and local communities alike are struggling to grasp the scale of the methane threat and what it means for our climate future.
I watched this last night and the implications, understated as they are in the show, are quite terrifying.
