"The Arctic continues to warm at a rate that is currently twice as fast as the global average. . . . Warming is causing perennially-frozen ground (permafrost) to thaw, with permafrost in many locations currently reaching record high temperatures. . . . . Organic carbon contained in soils of the permafrost region represent a climate-sensitive carbon reservoir that is affected by warming air and ground temperatures and permafrost thaw. . . . The northern permafrost region holds almost twice as much carbon as is currently in the atmosphere. Additional net releases of carbon dioxide (CO2) and methane (CH4) to the atmosphere as a result of warming and faster microbial decomposition of permafrost carbon have the potential to accelerate climate warming."
Schuur, T. "Permafrost and the Global Carbon Cycle." Arctic Report Card: Update for 2019, edited by J. Richter-Menge et al., National Oceanic and Atmospheric Administration, 22 Nov. 2019.
"Large quantities of organic carbon are stored in frozen soils (permafrost) within Arctic and sub-Arctic regions. A warming climate can induce environmental changes that accelerate the microbial breakdown of organic carbon and the release of the greenhouse gases carbon dioxide and methane. This feedback can accelerate climate change, but the magnitude and timing of greenhouse gas emission from these regions and their impact on climate change remain uncertain. Here we find that current evidence suggests a gradual and prolonged release of greenhouse gas emissions in a warming climate and present a research strategy with which to target poorly understood aspects of permafrost carbon dynamics" (171).
Schuur, E. A. G., et al. "Climate Change and the Permafrost Carbon Feedback." Nature, vol. 520, no. 7546, Apr. 2015, pp. 171-79.
"Overall, thawing permafrost in the Arctic appears to be an important additional source of heat-trapping gases to the atmosphere, more so than undersea hydrates. Climate and carbon cycle models are beginning to consider permafrost processes. While these models disagree on the exact amount of the heat-trapping gases that will be released into the atmosphere, they agree that: (i) the amount of such gases released from permafrost will increase with the amount of global warming; and (ii) the warming effect of thawing permafrost is significant enough to be considered in estimates of the remaining carbon budgets for limiting future warming" (773).
Canadell, Josep G., et al. "Global Carbon and Other Biogeochemical Cycles and Feedbacks." Climate Change 2021: The Physical Science Basis, Intergovernmental Panel on Climate Change, 2021, pp. 673-815.