Numerical modeling of permafrost dynamics in Alaska using a high spatial resolution dataset

Abstract

Abstract. Climate projections for the 21st century indicate that there could be a pronounced warming and permafrost degradation in the Arctic and sub-Arctic regions. Climate warming is likely to cause permafrost thawing with subsequent effects on surface albedo, hydrology, soil organic matter storage and greenhouse gas emissions. To assess possible changes in the permafrost thermal state and active layer thickness, we implemented the GIPL2-MPI transient numerical model for the entire Alaska permafrost domain. Input parameters to the model are spatial datasets of mean monthly air temperature and precipitation, prescribed thermal properties of the multilayered soil column, and water content which are specific for each soil class and geographical location. As a climate forcing we used the composite of five IPCC Global Circulation Models that has been downscaled to 2 by 2 km spatial resolution by Scenarios Network for Alaska Planning (SNAP) group. In this paper we present the preliminary modeling results based on input of five-model composite with A1B carbon emission scenario. The model has been calibrated according to the annual borehole temperature measurements for the State of Alaska. We also performed more detailed calibration for fifteen shallow borehole stations where high quality data are available on daily basis. To validate the model performance we compared simulated active layer thicknesses with observed data from CALM active layer monitoring stations. Calibrated model was used to address possible ground temperature changes for the 21st century. The model simulation results show the widespread permafrost degradation in Alaska could begin in 2040–2099 time frame within the vast area southward from the Brooks Range except for the high altitudes of the Alaska Range and Wrangell Mountains.