Mountain permafrost distribution in Dovrefjell and Jotunheimen, southern Norway, based on BTS and DC resistivity tomography data

The influence of climate and topography on the distribution of permafrost within the Dovrefjell and Jotunheimen areas, southern Norway, is analysed. A dataset of 972 BTS (bottom temperature of winter snow) measurements was analysed in relation to altitude, potential direct incoming radiation, aspect, snow depth, curvature and slope. To confirm and characterise permafrost-transition zones indicated from the BTS measurements, miniature temperature data-loggers, borehole temperatures, one-dimensional DC resistivity soundings and two-dimensional DC resistivity tomography were used. In addition, small-scale variance analyses upon the BTS values were performed using spatial-statistical methods. Results confirm that BTS values are highly correlated with altitude. Based on analysis of BTS data, the lower limit of possible permafrost is 1490 m a.s.l. on Dovrefjell and 1460 m a.s.l. in Jotunheimen. The relation between altitude and BTS suggests that the climate conditions on Dovrefjell and in Jotunheimen are similar with respect to permafrost distribution. Potential direct incoming radiation (PR) has a minor influence on BTS. A significant correlation between both surface moisture and surface type conditions in summer and BTS measurements were found. The results from Jotunheimen suggest that 20-45% of the variance in BTS results that are not explained by altitude are explained by small-scale spatial variance within a 20-30 m range. The results from the BTS measurements and the two-dimensional DC resistivity tomography were highly consistent.