A MATHEMATICAL APPROACH TO MODELING PALSA FORMATION - INSIGHTS ON PROCESSES AND GROWTH-CONDITIONS

A one-dimensional heat and mass transfer model was designed to simulate the long term aggradation of permafrost and the buildup of segregated ice that take place during the formation of palsas. The soil and climatic conditions used in model runs are the same as those observed in the field near the village of Kangiqsualujjuaq, in Northern Quebec. The model shows clearly that palsas can form under the present climatic conditions under snowfree sites. With assumed steady climatic conditions, model runs indicate that frost heave can produce a palsa a few meters high in about 60 years. After this initial growth period, the palsa can grow higher but at a slower rate until a quasi-steady state is reached after 150-200 years. The model suggests that ice concentrations aggregate near permafrost base. These conclusions generally agree with field conditions known from drilling and geophysics, and the timing is consistent with known ages of radiocarbon dated landforms. Developments of the modelling approach used in this study will help increase the understanding of still unsolved aspects of the processes of palsa formation such as the effect of surface geomorphologic changes and climatic variations on heat and mass transfer in permafrost.