A few degrees of Arctic warming could trigger massive permafrost thawing

As the Arctic is transformed by climate change, scientists have been working to understand the potential for CO2 and methane emissions to be released from thawing permafrost. This process accelerates global warming in what is known as a reinforcing feedback loop. 

A new study from Stockholm University is unraveling this mystery by analyzing sea floor sediment to estimate permafrost thawing that occurred during climate warming events of the past. The researchers found that only a few degrees of Arctic warming could trigger massive permafrost thawing, coastal erosion, and the widespread release of CO2 and methane.

There is more carbon stored in Arctic permafrost than all of that which is lingering in the atmosphere. To predict future greenhouse gas emissions from permafrost, the Stockholm team turned to the past to see how climate warming at the end of the last ice age affected permafrost.

“Our new study shows for the first time the full history of how warming at the end of the last ice age triggered permafrost thawing in Siberia. This also suggests the release of large quantities of greenhouse gases,” said study lead author Jannik Martens.

“It appears likely that past permafrost thawing at times of climate warming, about 14,700 and 11,700 years ago, was in part also related to the increase in CO2 concentrations that is seen in Antarctic ice cores for these times. It seems that Arctic warming by only a few degrees Celsius is sufficient to disturb large areas covered by permafrost and potentially affect the climate system.”

During a 2014 expedition onboard the Swedish icebreaker Oden, scientists recovered an eight-meter sediment core from more than 1,000 meters below the surface of the Arctic Ocean. For the current study, the experts used radiocarbon (14C) dating and molecular analysis to trace organic remains that were released from thawing permafrost, washed into the Arctic Ocean, and were ultimately preserved in the sediment core.

“From this core we also learned that erosion of permafrost coastlines was an important driving force for permafrost destruction at the end of the last ice age. Coastal erosion continues to the present day, though ten times slower than during these earlier rapid warming period. With the recent warming trends, however, we see again an acceleration of coastal erosion in some parts of the Arctic, which is expected to release greenhouse gases by degradation of the released organic matter,” explained study co-author Professor Örjan Gustafsson. 

“Any release from thawing permafrost mean that there is even less room for anthropogenic greenhouse gas release in the earth-climate system budget before dangerous thresholds are reached. The only way to limit permafrost-related greenhouse gas releases is to mitigate climate warming by lowering anthropogenic greenhouse gas emissions.”

The research team is currently working in the Arctic Ocean again as part of the International Siberian Shelf Study (ISSS-2020) onboard the Russian research vessel Akademik Keldysh. 

The expedition is seeking more answers to how climate change may trigger the release of greenhouse gases from thawing permafrost in the Arctic.

The study is published in the journal Science Advances.

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By Chrissy Sexton, Earth.com Staff Writer