Deep permafrost carbon pools and their vulnerability to mobilization

Arctic landscapes underlain by permafrost are threatened by climate warming and may degrade in different ways, including active layer deepening, thermal erosion, and development of thermokarst features. In Siberian and Alaskan late Pleistocene ice-rich permafrost, rapid and deep thaw processes cause surface subsidence due to loss of ground ice and mobilisation deep organic matter. With thawing, formerly freeze-locked organic matter is remobilized. This contributes to the carbon-climate feedback by reactivation of old carbon as greenhouse gases. The permafrost carbon climate feedback has been a process of global significance in the past and may contribute to acceleration of climate warming. In my research, I studied the carbon pools of the deep and ice-rich Yedoma permafrost, which is widespread in Siberia, Alaska and parts of NW Canada. I led data synthesis efforts and analysed field data to estimate that the Yedoma presently stores between 83±12 and 129±30 Gt of frozen organic carbon. During the last glacial period, such deposits potentially stored about 657 ± 97 Gt of organic carbon. Focusing on the estimates for the present and including deposits in degradation features we found ~398 Gt thaw-susceptible carbon in the Yedoma domain. While the Yedoma domain is covering only 7 % of the permafrost region, it represents more than 25 % of the frozen soil carbon pool of the permafrost zone