Permafrost map for Norway , Sweden and Finland 1

11 The thermal regime of permafrost is sensitive to changes in the climate system. A common, 12 research-based understanding of the permafrost distribution at a sufficient spatial resolution is 13 important to meet scientific, educational and societal demands. We present a new permafrost 14 map for Norway, Sweden and Finland providing a more detailed and updated description of 15 the permafrost distribution in this area. The CryoGRID1 model is implemented at 1 km2 16 resolution, forced by a new operationally gridded dataset of daily air temperature and snow 17 cover for Finland, Norway and Sweden. 100 model realizations are run for each grid cell, 18 based on statistical snow distributions, allowing for the representation of sub-grid variability 19 of ground temperatures. The new map indicates a total permafrost area (palsas excluded) of 20 23 400 km2 in equilibrium with the average 1981 – 2010 climate, corresponding to 2.2 % of 21 the total land area. About 56 % of the area is within Norway, 35 % in Sweden, and 9 % in 22 Finland. The model results are thoroughly evaluated, both quantitatively and qualitatively, as 23 a collaboration project including permafrost experts in the three countries. Observed ground 24 temperatures from 25 boreholes are within ±2 °C from the average modelled grid cell ground 25 2 temperature, and all are within the range of the modelled ground temperature for the 26 corresponding grid cell. The model results are also evaluated qualitatively by the 27 representatives conducting field investigations on permafrost at several sites within the three 28 countries, and are shown to reproduce observed lower altitudinal limits of permafrost and 29 permafrost distributions mapped by the corresponding detailed field investigations. 30