Peatlands and forests cover large areas of the boreal biome and are critical for global climateregulation. They also regulate regional climate through heat and water vapour exchange with theatmosphere. Understanding how land-atmosphere interactions in peatlands differ from forestsmay therefore be crucial for modelling boreal climate system dynamics and for assessing climatebenefits of peatland conservation and restoration. To assess the biophysical impacts of peatlandsand forests on peak growing season air temperature and humidity, we analysed surface energyfluxes and albedo from 35 peatlands and 37 evergreen needleleaf forests—the dominant borealforest type—and simulated air temperature and vapour pressure deficit (VPD) over hypotheticalhomogeneous peatland and forest landscapes. We ran an evapotranspiration model using landsurface parameters derived from energy flux observations and coupled an analytical solution forthe surface energy balance to an atmospheric boundary layer (ABL) model. We found thatpeatlands, compared to forests, are characterized by higher growing season albedo, loweraerodynamic conductance, and higher surface conductance for an equivalent VPD. Thiscombination of peatland surface properties results in a∼20% decrease in afternoon ABL height, acooling (from 1.7 to 2.5◦C) in afternoon air temperatures, and a decrease in afternoon VPD (from0.4 to 0.7 kPa) for peatland landscapes compared to forest landscapes. These biophysical climateimpacts of peatlands are most pronounced at lower latitudes (∼45◦N) and decrease toward thenorthern limit of the boreal biome (∼70◦N). Thus, boreal peatlands have the potential to mitigatethe effect of regional climate warming during the growing season. The biophysical climatemitigation potential of peatlands needs to be accounted for when projecting the future climate ofthe boreal biome, when assessing the climate benefits of conserving pristine boreal peatlands, andwhen restoring peatlands that have experienced peatland drainage and mining.
Peatlands and forests cover large areas of the boreal biome and are critical for global climateregulation. They also regulate regional climate through heat and water vapour exchange with theatmosphere. Understanding how land-atmosphere interactions in peatlands differ from forestsmay therefore be crucial for modelling boreal climate system dynamics and for assessing climatebenefits of peatland conservation and restoration. To assess the biophysical impacts of peatlandsand forests on peak growing season air temperature and humidity, we analysed surface energyfluxes and albedo from 35 peatlands and 37 evergreen needleleaf forests—the dominant borealforest type—and simulated air temperature and vapour pressure deficit (VPD) over hypotheticalhomogeneous peatland and forest landscapes. We ran an evapotranspiration model using landsurface parameters derived from energy flux observations and coupled an analytical solution forthe surface energy balance to an atmospheric boundary layer (ABL) model. We found thatpeatlands, compared to forests, are characterized by higher growing season albedo, loweraerodynamic conductance, and higher surface conductance for an equivalent VPD. Thiscombination of peatland surface properties results in a∼20% decrease in afternoon ABL height, acooling (from 1.7 to 2.5◦C) in afternoon air temperatures, and a decrease in afternoon VPD (from0.4 to 0.7 kPa) for peatland landscapes compared to forest landscapes. These biophysical climateimpacts of peatlands are most pronounced at lower latitudes (∼45◦N) and decrease toward thenorthern limit of the boreal biome (∼70◦N). Thus, boreal peatlands have the potential to mitigatethe effect of regional climate warming during the growing season. The biophysical climatemitigation potential of peatlands needs to be accounted for when projecting the future climate ofthe boreal biome, when assessing the climate benefits of conserving pristine boreal peatlands, andwhen restoring peatlands that have experienced peatland drainage and mining.