Future permafrost conditions along environmental gradients in Zackenberg, Greenland

Abstract. The future development of ground temperatures in permafrost areas is determined by a number of factors varying on different spatial and temporal scales. For sound projections of impacts of permafrost thaw, scaling procedures are of paramount importance. We present numerical simulations of present and future ground temperatures at 10 m resolution for a 4 km long transect across the lower Zackenberg valley in northeast Greenland. The results are based on stepwise downscaling of future projections derived from general circulation model using observational data, snow redistribution modeling, remote sensing data and a ground thermal model. A comparison to in situ measurements of thaw depths at two CALM sites and near-surface ground temperatures at 17 sites suggests agreement within 0.10 m for the maximum thaw depth and 1 °C for annual average ground temperature. Until 2100, modeled ground temperatures at 10 m depth warm by about 5 °C and the active layer thickness increases by about 30%, in conjunction with a warming of average near-surface summer soil temperatures by 2 °C. While ground temperatures at 10 m depth remain below 0 °C until 2100 in all model grid cells, positive annual average temperatures are modeled at 1 m depth for a few years and grid cells at the end of this century. The ensemble of all 10 m model grid cells highlights the significant spatial variability of the ground thermal regime which is not accessible in traditional coarse-scale modeling approaches.