Coupled Hydrological and Thermodynamical Modelling of Permafrost Dynamics: Implications for Northern Peatlands

Peatlands cover about 3 Mio km2 north of 40° N, with an estimated one-third of that area in zones of continuous permafrost and another 40% in discontinuous, sporadic, and isolated permafrost zones. Anticipated changes in the temperatures and distribution of permafrost and increasing active layer thickness as a result of a warming climate can therefore potentially impact the carbon dynamics in peatlands and thereby influence the peat net accumulation rates and methane emissions. We assess the large-scale changes in permafrost formation in Northern regions using a coupled hydrological and thermodymanic model that simulates hydrological budgets as well as soil temperatures for the entire soil column taking into account hydraulic and thermal properties of different soil types and using global climate drivers. Predicted soil temperatures and soil moisture dynamics are validated against a large set of observations in Alaska and Northern Eurasia as well as active layer measurements from the Circumpolar Active Layer Monitoring (CALM) program representing a wide range of climate conditions, soil properties and landscape characteristics. We test the sensitivity of the model to parameters and input data, present maps of the future geography of peatlands and permafrost regions, and report results of simulations for a number of different climate drivers derived from climate model outputs for a set of IPCC scenarios