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Climate warming in high‐latitude regions is thawing carbon‐rich permafrost soils, which can release carbon to the atmosphere and enhance climate warming. Using a coupled model of long‐term peatland dynamics (Holocene Peat Model, HPM‐Arctic), we quantify the potential loss of carbon with future climate warming for six sites with differing climates and permafrost histories in Northwestern Canada. We compared the net carbon balance at 2100 CE resulting from new productivity and the decomposition of active layer and newly thawed permafrost peats under RCP8.5 as a high‐end constraint. Modeled net carbon losses ranged from −3.0 kg C m⁻²(net loss) to +0.1 kg C m⁻²(net gain) between 2015 and 2100. Losses of newly thawed permafrost peat comprised 0.2%–25% (median: 1.6%) of “old” C loss, which were related to the residence time of peat in the active layer before being incorporated into the permafrost, peat temperature, and presence of permafrost. The largest C loss was from the permafrost‐free site, not from permafrost sites. C losses were greatest from depths of 0.2–1.0 m. New C added to the profile through net primary productivity between 2015 and 2100 offset ∼40% to >100% of old C losses across the sites. Differences between modeled active layer deepening and flooding following permafrost thaw resulted in very small differences in net C loss by 2100, illustrating the important role of present‐day conditions and permafrost aggradation history in controlling net C loss.

 

Abstract. Geography and associated hydrological, hydroclimate and land-useconditions and their changes determine the states and dynamics of wetlandsand their ecosystem services. The influences of these controls are notlimited to just the local scale of each individual wetland but extend overlarger landscape areas that integrate multiple wetlands and their totalhydrological catchment – the wetlandscape. However, the data and knowledgeof conditions and changes over entire wetlandscapes are still scarce,limiting the capacity to accurately understand and manage critical wetlandecosystems and their services under global change. We present a newWetlandscape Change Information Database (WetCID), consisting of geographic,hydrological, hydroclimate and land-use information and data for 27wetlandscapes around the world. This combines survey-based local informationwith geographic shapefiles and gridded datasets of large-scale hydroclimateand land-use conditions and their changes over whole wetlandscapes.Temporally, WetCID contains 30-year time series of data for mean monthlyprecipitation and temperature and annual land-use conditions. Thesurvey-based site information includes local knowledge on the wetlands,hydrology, hydroclimate and land uses within each wetlandscape and on theavailability and accessibility of associated local data. This novel database(available through PANGAEA https://doi.org/10.1594/PANGAEA.907398; Ghajarniaet al., 2019) can support site assessments; cross-regional comparisons; andscenario analyses of the roles and impacts of land use, hydroclimatic andwetland conditions, and changes in whole-wetlandscape functions and ecosystemservices.