Beneath much of the Arctic resides vast stores of greenhouse gases, locked up for millennia in icy soils. With this in mind, a pair of studies provides a double whammy of bad news: Not only are these frozen reservoirs thawing out more extensively than previously thought, but at this stage, there’s little that can be done about it.
Carbon dioxide and methane are indubitably the two most potent greenhouse gases. Vast reservoirs of both exist within the world’s permafrost, which is hydrated soil that has remained below the freezing point for two or more years.
Organic matter trapped there is broken down by microbes as their environment warms and thaws, and they produce plenty of both as a waste product. When the oxygen levels are low, methane is often the waste product of choice. Although it doesn't last anywhere near as long as cabron dioxide in the atmosphere, methane is more than 30 times as effective at trapping in heat within our atmosphere, which makes it a potent driver of global warming when there's enough of it.
Remarkably, these permafrost soils hold almost twice as much carbon than that found in the atmosphere – and a new study, published in Nature Geoscience, shows them thawing all across the northern hemisphere. This suggests that plenty of this methane is escaping skywards, which has implications for how quickly our planet will warm in the near future.
Thanks to consistently warmer summers, permafrost in Russia, Alaska and Canada is being “uncapped;” icy wedges that form at the top of the permafrost were observed to be almost universally melting even in the coldest regions of the Arctic. These wedges make up around 20 percent of the upper permafrost volume, so their melting is exposing massive areas of concealed, deeper permafrost.
“The scientific community has had the assumption that this cold permafrost would be protected from climate warming, but we’re showing here that the top of the permafrost, even if it’s very cold, is very sensitive to these warming events,” Anna Liljedahl, the lead author of the study and a researcher at the University of Alaska in Fairbanks, told the Washington Post.
Permafrost is melting in even the coldest regions, and by 2100, massive amounts of greenhouse gases will be released skywards. Liljedahl et al./Nature Geoscience
Importantly, permafrost isn’t the only icy prison for greenhouse gases. Around 56 million years ago, there was a mysterious, sizeable, global spike in atmospheric carbon. One of the prevailing theories is that this occurred when a huge cache of frozen methane beneath the seabed was destabilized by the already warming oceans, causing it to release its contents into the atmosphere as both methane gas and carbon dioxide. This, in turn, caused dramatic global warming, and a similar turn of events could happen today if the permafrost stores are unleashed.
The initial uptick in global temperatures could potentially further destabilize both reservoirs of frozen greenhouse gases, which in turn would release more trapped gas, and so on. Once this cycle reaches a certain tipping point, it may be impossible to prevent - although at this point, it's not clear how likely this is, or what exactly the tipping point itself even is.
In any case, is there any way to avoid - prolific methane effusion, aside from agreeing to cut greenhouse gas emissions on a global scale? Some have suggested that plants, which would begin to proliferate in a warmer Arctic, could end up soaking up the escaping carbon dioxide, acting as a biological buffer to this increasingly troubling phenomenon.
Another study was commissioned to ask 100 Arctic researchers if this was plausible, and they gave a resounding answer: no, it’s not. The research, published in Environmental Research Letters, concluded that “the permafrost region will become a carbon source to the atmosphere by 2100 regardless of warming scenario.”
This means that, whatever happens, a vast chunk of its carbon will inexorably escape to the atmosphere by the end of the century. However, they do point out that up to 85 percent of permafrost carbon release could be stopped if human emissions are “actively reduced.”