The magnitude of future emissions of greenhouse gases from the northern permafrost region depends crucially on the mineralization of soil organic carbon (SOC) that has accumulated over millennia in these perennially frozen soils. Many recent studies have used radiocarbon (¹⁴C) to quantify the release of this “old” SOC as CO₂ or CH₄ to the atmosphere or as dissolved and particulate organic carbon (DOC and POC) to surface waters. We compiled ~1,900 ¹⁴C measurements from 51 sites in the northern permafrost region to assess the vulnerability of thawing SOC in tundra, forest, peatland, lake, and river ecosystems. We found that growing season soil ¹⁴C‐CO₂ emissions generally had a modern (post‐1950s) signature, but that well‐drained, oxic soils had increased CO₂ emissions derived from older sources following recent thaw. The age of CO₂ and CH₄ emitted from lakes depended primarily on the age and quantity of SOC in sediments and on the mode of emission, and indicated substantial losses of previously frozen SOC from actively expanding thermokarst lakes. Increased fluvial export of aged DOC and POC occurred from sites where permafrost thaw caused soil thermal erosion. There was limited evidence supporting release of previously frozen SOC as CO₂, CH₄, and DOC from thawing peatlands with anoxic soils. This synthesis thus suggests widespread but not universal release of permafrost SOC following thaw. We show that different definitions of “old” sources among studies hamper the comparison of vulnerability of permafrost SOC across ecosystems and disturbances. We also highlight opportunities for future ¹⁴C studies in the permafrost region.

中文翻译：

---

评估多年冻土融化后旧土壤碳的动员潜力：来自北部多年冻土地区的14 C测量值的综合

北部多年冻土区未来温室气体的排放量在很大程度上取决于在这些多年生冻土中累积了数千年的土壤有机碳（SOC）的矿化作用。最近的许多研究都使用了放射性碳（¹⁴ C）来量化这种“旧的” SOC以CO ₂或CH ₄的形式释放到大气中，或者以溶解的颗粒有机碳（DOC和POC）的形式释放到地表水中。我们对北部多年冻土地区的51个站点进行了约1,900个¹⁴ C测量，以评估冻原，森林，泥炭地，湖泊和河流生态系统中SOC解冻的脆弱性。我们发现生长季土壤¹⁴ C‐CO ₂排放通常具有现代的特征（1950年代后），但是排水良好的含氧土壤在最近的融化之后增加了来自较旧资源的CO ₂排放。湖泊排放的CO ₂和CH ₄的年龄主要取决于沉积物中SOC的年龄和数量以及排放方式，并表明从积极扩张的喀斯特喀斯特湖中先前冻结的SOC大量损失。多年冻土融化导致土壤热侵蚀的地区，老年DOC和POC的河流出口量增加。仅有有限的证据支持释放先前冻结的SOC以CO ₂，CH _4的形式释放，以及来自用缺氧土壤解冻的泥炭地的DOC。因此，该合成表明融化后多年冻土SOC的广泛但非普遍释放。我们表明，研究之间对“旧”源的不同定义妨碍了多年冻土SOC在整个生态系统和扰动之间的脆弱性比较。我们还重点介绍了多年冻土地区未来¹⁴ C研究的机遇。