Permafrost Weakening as a Potential Impact of Climatic Warming

摘要

The warming weakening of permafrost strength as a result of different scenarios of climatic warming ranging from 0 to 5℃ over the next century has been predicted using a one-dimensional geothermal model. These predictions are based on the results of an intensive geotechnical program carried out in a warm ice-rich silty permafrost in Northern Quebec. The dependency of permafrost strength on temperature was assessed from cone penetration tests performed at regular intervals over a 2-month period during the seasonal warming of the upper permafrost layer in spring 2000. A thcrmomechanical subroutine taking into account this dependency has been then added to the one-dimensional geothermal model for the simulation of the weakening of permafrost strength as it warms. A warming rate of 0.02℃/year over the next century leads on a slow decrease in permafrost strength corresponding to a relative loss of strength of about 50%. For a warming rate of 0.05℃/year, the strength weakening is much more pronounced and almost reaches the unfrozen state at the end of the warming period corresponding to a relative loss of 98%.