INFLUENCE OF THE DEPTH HOAR LAYER OF THE SEASONAL SNOW COVER ON THE GROUND THERMAL REGIME

Snow cover is a good insulator since it has low thermal conductivity. The structure of the seasonal snow cover usually consists of higher-de nsity layers at the top with coarse, lower-density depth hear layers a t the base. Because of its much smaller thermal conductivity, changes in depth hear fraction can have a significant impact on the insulating effect of the seasonal snow cover. A one-dimensional finite differenc e conductive heat transfer model with phase change was applied to inve stigate the effect of variations in the depth hear fraction of the sea sonal snow cover on the ground thermal regime. The snow cover was trea ted as a single layer with the effective thermal properties determined with considerations of the effect of the wind slab and depth hear lay er. The model was applied to investigate the thermal regime of the act ive layer and permafrost from October 5, 1986, through July 13, 1991, at West Dock near Prudhoe Bay, Alaska. Results indicate that the calcu lated temperatures on the ground surface, in the active layer, and in deep permafrost are in excellent agreement with the measured temperatu res. A sensitivity study shows that in permafrost regions, variations in the depth hear fraction from 0.0 to 0.6 can increase the daily grou nd surface temperature 12.8 degrees C and the mean annual ground surfa ce temperature by 5.5 degrees C and delay the active layer freeze-up b y several months. In nonpermafrost regions an increase in the depth he ar fraction from 0.0 to 0.6 can increase the daily ground surface temp erature by 8.4 degrees C and the mean annual ground surface temperatur e by up to 2.4 degrees C and reduce the seasonal freezing depth by up to 80%.