| Summary: | Recent observations indicate a warming of permafrost in many northern regions with the resulting degradation of ice-rich and carbon-rich permafrost. Permafrost temperature has increased by 1 to 3 deg C in the Northern Hemisphere during the last 30-40 years. To assess possible changes in the permafrost and the active layer dynamics we developed a robust coupling of a GIPL (Geophysical Institute Permafrost Lab) transient model and modified version of the pan-Arctic Water Balance Model (P/WBM) developed at the University of New Hampshire. Through explicit coupling of the Permafrost Model with the Water Balance Model we are able to simulate the hydrological budgets, temporal and spatial variability in soil water/ice content, active layer thickness, and associated large-scale hydrology that are driven by contemporary and future climate variability and change. Coupling of the GIPL model with a suitably-scaled hydrological model captures thresholds and highly non-linear feedback processes induced by changes in hydrology and the temperature regime over the panArctic. Input parameters to the model are spatial datasets of mean monthly air temperature, snow properties or SWE (Snow Water Equivalent), prescribed vegetation and thermal properties of the multilayer soil column, and water content. The climate scenario was derived from an ensemble of five IPCC Global Circulation Models (GCM) ECHAM5, GFDL21, CCSM, HADcm3 and CCCMA. The outputs from these five models have been scaled down to 25 km spatial resolution with monthly temporal resolution, based on the composite (mean) output of the five models, using the IPCC SRES A1B CO2 emission scenario through the end of current century. The model takes into account the geographic distribution of organic soils and peatlands, vegetation cover and soil properties, and is tested against a number of permafrost temperature records for the last century. We estimated dynamics of the seasonally thawed volume of soils within the two upper meters for the entire North Eurasia using a coupled, ...
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