The US government's 2019 Arctic Report Card finds that melting permafrost has made the arctic a net producer of greenhouse gasses:
Especially noteworthy is the report’s conclusion that the Arctic already may have become a net emitter of planet-warming carbon emissions due to thawing permafrost, which would only accelerate global warming. Permafrost is the carbon-rich frozen soil that covers 24 percent of the Northern Hemisphere’s land mass, encompassing vast stretches of territory across Alaska, Canada, Siberia and Greenland.
Warming temperatures allow microbes within the soil to convert permafrost carbon into the greenhouse gases — carbon dioxide and methane — which can be released into the air and accelerate warming. Ted Schuur, a researcher at Northern Arizona University and author of the permafrost chapter, said the report “takes on a new stand on the issue” based on other published work including a study in Nature Climate Change in November.
Taking advantage of the new studies — one on regional carbon emissions from permafrost in Alaska during the warm season, and another on winter season emissions in the Arctic compared to how much carbon is absorbed by vegetation during the growing season — the report concludes permafrost ecosystems could be releasing as much as 1.1 billion to 2.2 billion tons of carbon dioxide per year. This is almost as much as the annual emissions of Japan and Russia in 2018, respectively.
Only, if you can believe, it's worse than that. Because the microbes also produce methane, which gram-for-gram causes about 4 times more warming. And as the region gets warmer, more microbes produce more gas, in a negative spiral.