A dangerous feedback loop between Arctic warming, permafrost melt, and greenhouse gas emissions could soon start spiraling out of control, according to new research.
Climate change models have long predicted that melting ground in the Arctic will expose old organic material to air and microbes, causing it to decompose, which will result in emissions of carbon dioxide and the potent greenhouse gas methane. It’s a scary proposition; there is currently almost twice as much carbon locked in permafrost than in all of Earth’s atmosphere.
The potential problem is immense, and so is the challenge for researchers trying to measure this feedback loop. Most studies focus on predicting the future, although permafrost has been degrading sometimes spectacularly for decades. Measuring gases rising up from Arctic ground is hard to do, especially when you consider that the carbon decomposed from old organic material will mingle with that from newer sources before it leaves the ground.
Katey Walter Anthony, an ecologist with the University of Alaska Fairbanks, and a team of researchers came up with a partial workaround for this problem by focusing their attention on thermokarst lakes, which are pools of meltwater over permafrost. In wintertime, methane released from the bottom is trapped as bubbles in the ice on the surface, making it easier to sample and measure.
The resulting article, published online Monday in Nature Geoscience, estimates for the first time the carbon feedback loop from permafrost melt around Arctic thermokarst lakes. The researchers found a clear correlation between surface area expansion of the lakes — an indicator of permafrost degradation — and the volume of methane and carbon dioxide emitted from ice and soils. Carbon dating showed that age of methane in the bubbles encased in ice matched the age of the surrounding permafrost.
These are good indications that the researcher’s methods and assumptions are fairly sound. However, this is only the first stab at a very complex problem, and reaching a conclusion that encompasses entire Arctic region based on measurements from 37 lakes in three countries is risky business. That uncertainty is reflected in the authors’ wide-ranging estimate: between 0.2 and 2.5 billion metric tons of carbon released from areas of thermokarst expansion across the Arctic in the last 60 years. That’s not counting carbon emitted from terrestrial regions of permafrost melt, which cover a much greater area.
It seems like a big number, but if the predictions of other researchers come true, that’s only a very small tip of a very large iceberg. Studies have predicted carbon emissions from permafrost between 100 and 900 times larger than anything seen on Earth for at least 11,700 years. “Our research indicates that the dramatic increase in permafrost carbon emissions that is expected to imminently occur shows no sign of having commenced,” the authors write.
That’s not good.