Future trajectories of peatland permafrost under climate and ecosystem change in northeastern Canada

Peatland permafrost ecosystems include culturally and ecologically important habitat 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, the Northern Ecosystem Soil Temperature model is used to simulate future ground temperature trajectories for nine peatland permafrost landforms along the Labrador Sea coastline. Ground temperatures are modeled for each site from 2024 to 2100 under six scenarios, which account for differences in future land cover, snow, and climate warming (RCP4.5). All scenarios incorporating a change in ecosystem characteristics or climate result in total 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 study sites exhibit wide variations in thaw rates due to differences in latitude, geomorphological characteristics, and initial permafrost thicknesses. While most sites experience active layer thickening, four of the nine sites also see the development of supra-permafrost taliks, but this occurs almost exclusively in the four 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.