Permafrost thaw liberates frozen organic carbon, which is decomposed into carbon dioxide (CO₂) and methane (CH₄). The release of these greenhouse gases (GHGs) forms a positive feedback to atmospheric CO₂ and CH₄ concentrations and accelerates climate change^1,2. Current studies report a minor importance of CH₄ production in water-saturated (anoxic) permafrost soils^3,4,5,6 and a stronger permafrost carbon–climate feedback from drained (oxic) soils^1,7. Here we show through seven-year laboratory incubations that equal amounts of CO₂ and CH₄ are formed in thawing permafrost under anoxic conditions after stable CH₄-producing microbial communities have established. Less permafrost carbon was mineralized under anoxic conditions but more CO₂–carbon equivalents (CO₂–Ce) were formed than under oxic conditions when the higher global warming potential (GWP) of CH₄ is taken into account⁸. A model of organic carbon decomposition, calibrated with the observed decomposition data, predicts a higher loss of permafrost carbon under oxic conditions (113 ± 58 g CO₂–C kgC⁻¹ (kgC, kilograms of carbon)) by 2100, but a twice as high production of CO₂–Ce (241 ± 138 g CO₂–Ce kgC⁻¹) under anoxic conditions. These findings challenge the view of a stronger permafrost carbon-climate feedback from drained soils^1,7 and emphasize the importance of CH₄ production in thawing permafrost on climate-relevant timescales.

多年冻土融化后释放出冻结的有机碳，该有机碳分解为二氧化碳（CO ₂）和甲烷（CH ₄）。这些温室气体（GHGs）的释放形成了对大气中CO ₂和CH ₄浓度的正反馈，并加速了气候变化^1,2。目前的研究报告表明，在水饱和（缺氧）的多年冻土^3,4,5,6中产生CH _4的重要性不大，而从排水（有氧）的土壤^1,7产生的更强的多年冻土碳气候反馈更为重要。在这里，我们通过七年的实验室孵化展示了相等数量的CO ₂和CH ₄在稳定的产生CH _4的微生物群落建立之后，在缺氧条件下的永冻土层融化过程中形成了碳纳米管。少多年冻土炭在缺氧条件下矿化但更多的CO ₂ -碳当量（CO ₂被形成为比好氧条件下-Ce）CH时的较高的全球变暖潜能（GWP）₄是考虑到⁸。根据观察到的分解数据校准的有机碳分解模型预测，到2100年，在有氧条件下（113±58 g CO ₂ –C kgC ^-1（kgC，千克碳）），多年冻土碳的损失更高。作为高产量的CO ₂ -Ce（241±138 g CO ₂–Ce kgC ^-1）在缺氧条件下。这些发现挑战了从排水土壤^1,7得到的更强的多年冻土碳气候反馈的观点，并强调了在与气候有关的时间尺度上，CH _4的生产对于解冻多年冻土的重要性。