Rapid climate change in the Northern Hemisphere cryosphere threatens ancient permafrost carbon. Once thawed, permafrost carbon may migrate to surface waters. However, the magnitude of permafrost carbon processed by northern freshwater remains uncertain. Here, we compiled '1800 radiocarbon data of aquatic dissolved organic carbon (DOC) and particulate organic carbon (POC) in the Arctic and Qinghai -Tibet Plateau (QTP) to explore the fate of permafrost carbon under climate warming over the past 30 years. We showed that the contribution of aged carbon has significantly increased since 2015. Approximately 70 % of DOC and POC was derived from aged carbon for QTP rivers. In Arctic waters, an average of '67 % of POC was derived from aged carbon, however, '75 % of DOC was derived from modern carbon, mainly due to low temperatures and protection by vegetation limiting the export of aged DOC. For both regions, DOC 14 C age was positively correlated with the active layer thickness, whereas the POC 14 C age was positively correlated with the mean annual ground temperature, suggesting that gradual thaw accelerated the mobilization of aged DOC while abrupt thaw facilitated the export of aged POC. Furthermore, POC 14 C age was positively correlated with the soil organic carbon density, which was attributed to well-developed pore networks facilitated aged carbon output. This study suggests that permafrost carbon release is affected by both permafrost thermal properties and soil organic carbon density, which should be considered in evaluation of permafrost carbon -climate feedback.

来源平台：JOURNAL OF ENVIRONMENTAL SCIENCES