Impact of climate warming on the ground surface temperature in the sporadic permafrost zone of the Tatra Mountains, Poland and Slovakia

This paper examines the influence of climate change on the temperature of a debris slope surface in the zone of sporadic permafrost occurrence in the Tatra Mountains. This involved applications of linear regression equations which describe statistical dependence of the ground surface temperature (GST) upon the current air temperature in snow-free periods, or upon the previous air temperature and snow depth. These equations are validated using the daily air temperature and snow depth at a reference synoptic station and GST at 5 sites located in different topographic conditions. In order to estimate mean winter half-year, mean summer half-year and mean annual GST at these sites in hydrological years 1955–2010, archival meteorological data were used. The maximum errors in these estimations, determined for two reference years, were 0.5 °C, 0.2 °C and 0.1 °C respectively. The results show that the debris slopes thermal sensitivity to climate warming decreases with the increase of: a) shading, 2) altitude, and 3) depth of seasonal snow cover. In general, the changes of the air temperature influence the changes of mean annual ground surface temperature more in snow-free periods than in snow periods, whereas the degradation of orographically conditioned permafrost patches occurs faster in the places where snow cover is thin during the whole winter. The decrease of the depth of a thick snow cover may be accompanied by the decrease of its bottom temperature, despite the increase of the winter air temperature. We infer that in special orographic-nival conditions, the increase of mean annual air temperature may be accompanied by the decrease of mean annual ground surface temperature.

► Climate of the Tatra Mountains is warming.
► Thermal sensitivity of debris slope depends on shading, altitude and snow depth.
► Changes in GST mainly depend on air temperature in snow-free periods.
► The decrease of the snow depth may be accompanied by the decrease of the GST.
► Thin snow cover favours both aggradation and degradation of permafrost.