Melting Permafrost May Soon Cause Arctic to Emit as Much Carbon as Large Industrial Nations

ON 10/31/2022 AT 02:18 AM

A new study of permafrost melting and methane has determined the pace of global heating could push total carbon releases from the Arctic this century to as high as some of the biggest industrial nations have emitted in total since the industrialized age began.

A thermokarst lake with methane bubbling

Methane bubbles up from the thawed permafrost at the bottom of the thermokarst lake through the ice at its surface. Researchers in the current study have discovered the Arctic could release catastrophically large amounts of CO2 and Methane well before the end of the century. Photo: NASA

The analysis, headed up by biological and climate scientists at Northern Arizona University and the International Permafrost Carbon Network, made its predictions by first looking at the rate of Arctic heating under differing scenarios regarding fossil fuel emissions. Using data about the amounts of carbon and methane trapped in various levels of permafrost present in various regions of the Arctic, it then analyzed what might happen as the methane and CO2 would be released from currently frozen plant matter, ice and other frozen forms of methane.

The study also considered mitigating factors when plant matter begins to regrow as the land masses heat up, a phenomenon which would result in some carbon absorption by this greening of the Arctic. The study also looked at the potential for rapid carbon dioxide and methane releases as entire blocks of permafrost might suddenly release large amounts of trapped gases, as the equivalent of frozen “corks” could give way and let previously trapped large bubbles escape into the air all at once. Other conditions such as underground thermal erosion were also considered in the modelling, as a possible cause of further sudden CO2 and NH4 releases. Other issues also built into the model account for hydrological dynamics and certain biochemical tipping points only present within what the researchers call the “permafrost zone”

Other aspects of the model considered the differing nature of permafrost structures depending on where they were located within the Arctic region. That too was considered in making the ultimate calculations.

As an example of that modelling detail, the scientists carrying out the research determined that surface permafrost area will decrease by 69 +/- 20 percent not long after mid-century.

The scientists also note that between 40% to 70% of radiative forcing — the heating effect — of melting permafrost would come from the methane stored in the permafrost. That is because of the much higher heat trapping effects of the presence of methane vs. carbon dioxide in the atmosphere.

Under the best-case scenario, the scientists using data such as this, the scientists determined total Arctic carbon emissions from CO2 and methane sources might hit 55 petagrams (Pg) (61 billion tons) by the end of the century. A worst-case scenario, assuming global temperatures would rise by as much as 6 to 8 degrees C after mid-century, says the permafrost melting and subliming could have dumped 232 Pg (256 billion tons) into the atmosphere by 2070 and beyond.

The study also notes that there are multiple ways these emissions could spike faster and by larger amounts. As they explain, when what used to be frozen ground either erodes or subsides, the carbon previously stored there can move into the atmosphere via microbial respiration or via explosive methane releases. These are just a few of many non-linear shifts which can irrevocably change the future trajectory of permafrost carbon release.

By comparison, according to Our World in Data, the United States, the top cumulative source of carbon emissions in the world, has emitted 399 billion tons of carbon dioxide and equivalents since the late 18th century. That converts to 362 petagrams of carbon for 25% of cumulative total emissions to date. The European Union, in second position with 22% of global cumulative emissions for the same period, has released 353 billion tons (320 Pg) of CO2 and equivalents. China is at number three with 200 billion tons (181 Pg) of CO2 and a net 12.7% of all emissions.

What this adds up to is that, as Guido Grosse, head of the permafrost research section of the Alfred Wegener Institute in Potsdam, Germany, and a co-author of the study, said, “Permafrost emissions [from the Arctic] will be a large and substantial contributing factor to atmospheric greenhouse gases, no matter which of the possible scenarios becomes reality.”

They will be huge and equivalent to the sum total of all emissions to date by some of the biggest industrialized countries on the planet.

We also will not be able to stop this catastrophic release of carbon.

“Once permafrost carbon emissions increase in response to climate warming as some models predict, there won’t be a way for us to stop that process,” said Roisin Commane, assistant professor of Earth and environmental sciences at Columbia University and another co-author of the new study.

Permafrost and Climate Change: Carbon Cycle Feedbacks from the Warming Arctic,” by Edward A.G. Schuur, et. al, was published in October 2022, in Volume 47 of the Annual Review of Environment and Resources.