Abstract
Boreal and subarctic peatlands are an important dynamical component of the earth system. They are sensitive to climate change, and could either continue to serve as a carbon sink or become a carbon source. Climatic thresholds for switching peatlands from sink to source are not well defined, and therefore, incorporating peatlands into Earth system models is a challenging task. Here we introduce a climatic index, warm precipitation excess, to delineate the potential geographic distribution of boreal peatlands for a given climate and landscape morphology. This allows us to explain the present-day distribution of peatlands in Western Siberia, their absence during the Last Glacial Maximum, their expansion during the mid-Holocene, and to form a working hypothesis about the trend to peatland degradation in the southern taiga belt of Western Siberia under an RCP 8.5 scenario for the projected climate in year 2100.
Highlights
Index for “measuring” climate suitability for peatland expansion: warm precip excess (WPE), which is defined as Pw − 0.7PET, where Pw is precipitation during the warm period of the year
At g = 10 m, half of the watershed area is suitable for peatland expansion when WPE is equal to 30 mm/yr (Fig. 2, lower right corner)
30 mm/yr could be considered a level of WPE that “turns on” the process of massive peatland expansion in Western Siberia
Summary
Index for “measuring” climate suitability for peatland expansion: warm precip excess (WPE), which is defined as Pw − 0.7PET, where Pw is precipitation during the warm period of the year. The fraction of land that could be occupied by peatlands depends on climatic conditions. Peatlands may not become geographically widespread until WPE exceeds a certain threshold set by landscape morphology. To find this WPE threshold we apply a model based on the Dupuit-Forchheimer theory of groundwater movement[29] (see Methods). This theory, starting from the seminal work of Ingram As climate input we use the fields of mean monthly temperature and precipitation simulated by MPI-ESM (refs 20, 21) for present-day, mid-Holocene, LGM, and 2100 climate
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