Impermafrost - Coming Carbon Release From Arctic Soils Far Faster Than Last State Change 10,000 BCE

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Now 42, Cory first set foot in Toolik 15 years ago when she herself was a student. Ever since, the arc of her career has tracked rising concern about the fate of permafrost and the carbon it contains. Trained in photochemistry, Cory often sees things others do not. Previously, for example, scientists thought mostly about the carbon dioxide released by microbes that, in soils, operate totally in the dark. But from the moment she arrived at Toolik, Cory saw a landscape awash in light. For a few months of the year, 24 hours a day, Arctic waters are quite literally sun-struck, which turns out to be relevant to the release of carbon from permafrost. Starting in 2010, Cory linked up with Michigan’s George Kling and Byron Crump, a microbiologist from Oregon State University, to explore the biochemical and geochemical impacts of light. One set of experiments involved collecting water samples from seven active thermokarst sites. After removing impurities with a filter, the team put the samples into plastic pouches and left them outside to bask in the sun. This “sun tea” was then presented to bacteria sieved from the same thermokarst-infused water.

This sunlight treatment, the scientists found, substantially boosted the microbes’ ability to convert the dissolved carbon compounds in the samples into carbon dioxide. The mechanism? Light, ultraviolet light in particular, is a breaker of chemical bonds. Like a kitchen knife, it slices and dices organic molecules into smaller, more palatable bits. A second series of experiments focused on the microbial communities cultured from Arctic soils. Most effective at decomposing light-treated organic carbon were those that emerged from thawed chunks of permafrost where they’d remained dormant, or even—as some believe—sluggishly active for centuries.

But microbes are just part of the story. In a study of more than 70 lakes, streams, and rivers, including the Sag, Cory and her colleagues have established that exposure to sunlight alone can turn carbon into CO2, without any microbial involvement. The rate at which this happens varies with the cloudiness of the sky, the thickness of the ice cover, and the depth and clarity of the water. But on average, they found, this abiotic conversion may account for about a third of all the carbon dioxide currently released by Arctic surface waters. It’s a photochemical pathway that will increase in importance as rising temperatures accelerate the thawing of permafrost and the melting of sunlight-occluding ice.

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The last time our planet confronted such a consequential upheaval was around 12,000 years ago, when the last ice age ended in a rolling thunder of warmth. On a geological timescale, the changes that followed were fast—sea levels rose, weather patterns changed, species migrated poleward—but measured against the lifetime of an itinerant hunter-gatherer, they would have been all but imperceptible. This time around, the rate of transformation and its impacts on our densely settled planet are becoming obvious within a generation, especially in the Far North, where air temperatures have been rising at a clip of 0.5 °C per decade. The natural world is now responding in ways that amplify that warming. Dwindling sea ice is changing the color of the Arctic Ocean, uncovering dark blue waters, which absorb solar heat rather than reflect it. The loss of ice is likewise exposing the permafrost-rich coastline, and the remote communities along it, to storms and frenzied waves. In the boreal zone, wildfires stimulated by record heat and drought have burned through millions of hectares of trees and released the carbon once locked into wood; they have also turned thick layers of forest duff to ash, ripping away the summer insulation that once protected the permafrost.

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https://www.hakaimagazine.com/features/impermanence-permafrost/