Numerical simulation of the impacts of climate warming on a permafrost mound

A finite-element, one-dimensional, heat conduction model, which takes thaw settlement into account following drainage of excess water produced by the melt of ice lenses at the permafrost boundaries, is used to assess the thermal response of a permafrost mound in Northern Quebec to different scenarios of climate warming. In addition to the cryostratigraphy of the mound, the unfrozen water content, thermal conductivity and volumetric heat capacity of the marine sediments comprising the mound were integrated in the simulation. Warming rates from 0.03 to 0.01degreesC/year are predicted in the mound for a gradual linear increase in mean annual air temperature of 0.05degreesC/year over a 100 year period. Downward thawing occurs at the permafrost table at rates of 1-13 cm/year but there is also upward thawing from the permafrost base at rates of 2.4-5.8 cm/year. The thermal response of permafrost is not linear with time. At the end of the 100 year period, thaw settlement predicted was 1.4 m and the active layer was 3.22 m thick over a talik of 1.46 m thick. This is in comparison to an active layer of 2.14 m thick over a talik of 1.86 m if thaw settlement is not considered in the simulation. Thaw settlement, the direct result of ice melting in permafrost, brings permafrost nearer to the surface and accelerates its thawing. It should be included in any numerical simulation. Copyright (C) 2004 John Wiley Sons, Ltd.