Future Trajectories of Peatland Permafrost Under Climate and Ecosystem Change in Northeastern Canada

Peatland permafrost ecosystems include culturally and ecologically important habitats for plants and wildlife. Widespread degradation of palsas and peat plateaus suggests vulnerability of these landforms to climate warming, but ecosystem changes, including landscape greening due to shrub expansion and related changes in snow distribution, are also expected to impact permafrost persistence. In this study, a process-based one-dimensional transient model is used to simulate an ensemble of future ground temperature trajectories for seven palsa and two peat plateau study sites along the Labrador Sea coastline. Ground temperatures are modeled from 2024 to 2100 under nine scenarios, which account for differences in future land cover, snow, and climate warming (RCP4.5 and RCP8.5). All scenarios incorporating a change in ecosystem characteristics and/or climate result in loss of permafrost at all sites by 2100, with some sites experiencing loss of permafrost by 2036. Although permafrost thaw occurs at all sites under most scenarios, the sites exhibit wide variations in thaw rates due to differences in latitude, geomorphological characteristics, and initial permafrost thicknesses. Most sites experience active layer thickening, but four of the nine sites also see the development of supra-permafrost taliks, though this occurs almost exclusively in the scenarios that incorporate ecosystem change. The development of taliks under these scenarios and the earlier loss of permafrost suggest that peatland permafrost in coastal Labrador may be more sensitive to ecosystem change than climate warming alone. These results provide important insights into the future evolution and climate sensitivity of permafrost peatlands in the discontinuous permafrost zone.