Ground freeze-thaw, snow and roads in northern Sweden

Sammanfattning: In this thesis freeze-thaw along roads in northern Sweden is examined. The examinations are put in a context of changing climate and its amplification towards the Arctic region on earth. The research focuses on the impact of a warmer climate on ground freeze-thaw and in exten- sion road maintenance in the region. The investigation is presented through two scientific papers, where the first examines how ground temperatures are developed during a single frost season experiment, where a natural accumulation of snow cover and a continual removal of snow cover occur respectively.In the second paper, ground temperature data from sub-Arctic Sweden that has been logged by the Swedish Transport Administration, has been collected and freeze-thaw cycles have been calculated and analysed. The results are related to regional landscape factors and are in the context of regional climate change discussed to reach understanding of challenges for road maintenance in the region and opportunities to reach resilience.The results in Paper 1 show that also a thin cover of snow has impact on the freeze-thaw frequency, duration and intensity that occur in and on the surface of the ground. Furthermore the results show that the ground temperatures rise in due to an increase in snow cover amounts and that this process occurs in several steps.Paper 2 shows that the occurrence of ground freeze-thaw is affected by the proximity to open waters. Warmer temperatures in the air may cause later ice freeze-up and earlier ice break-up on lakes, rivers and on the Gulf of Bothnia and roads in northern Sweden are in general situated on the coast or near rivers. Ground temperatures around 0 °C has a high negative impact on road stability and a warmer and wetter climate in northern Sweden may thus increase road deterioration. The economic development in Sweden stays dependent on extraction of natural resources in sub-Arctic Sweden and thus it is of major concern to main- tain and improve road infrastructure in the region.