Effect of Surface Covers on Heat Fluxes to the Soil in West Spitsbergen

Climate warming changes in heat fluxes within the atmosphere–surface cover–soil system and affects the thermal state of permafrost. A comparison of heat fluxes from the atmosphere to the soil during the period with positive air temperatures and from the soil to the atmosphere during the cold period makes it possible to assess the permafrost stability. Snow and moss cover are important factors influencing heat fluxes. The influence of surface fluxes on heat fluxes is estimated based on mathematical modeling and numerical experiments on the model. The processing of data from field measurements of soil temperature made it possible to determine the heat fluxes for the cold and partially warm periods of the year. A comparison of the data from model calculations and measurements of heat fluxes showed a satisfactory agreement. The difference between them from December to February did not exceed 4%; in November and March, 9 and 8%, respectively. In 2023/24, during the period with negative air temperatures lasting 255 days with an average air temperature of −7°C, soil heat losses amounted to 76.5 and 92.3 MJ/m2 with snow thickness of 1.14 and 0.63 m, respectively; the average values of heat fluxes from October to March were 4.9 and 5.9 W/m2. According to model calculations, with an average daily positive air temperature of 6.8°C, the loss by the soil in winter is 10 MJ/m2 less than the heat flux into the soil in summer, which leads to permafrost degradation. At snow cover depth of 0.5 m, the heat input into the soil in summer coincides with the heat loss in winter. With a higher snow cover depth, the heat flux from the soil to the atmosphere decreases, soil cooling decreases, and permafrost degradation will occur. The same processes will occur when the snow cover is 1-m-deep and the moss cover is less than 3-cm-thick. For a moss cover of greater thickness, the thermal stability of permafrost rocks is preserved. Numerical experiments on the model estimated the heat fluxes and the thickness of the active layer for different snow and moss cover thicknesses and atmospheric air temperatures.