Numerical simulation of Permafrost Depth at the Mol site

In the Safety and Feasibility Case 1, future climate changes are considered in several safety statements. One particular case of climate change involves the future development of permafrost in the Mol area. Geological evidence undoubtedly points to the presence of permafrost during previous cold periods (Beerten, 2010). Progradation, maintenance and degradation of permafrost may induce changes in the performance of the deep repository system such as groundwater flow changes, changes in porewater chemistry etc. Whereas the lateral extent of permafrost can be deduced from surface features, not much is known about the maximum depth of permafrost during a cold stage. The calculated permafrost thickness ranges between 150 m and 210 m around 60 ka, and between 160 m and 215 m around 19 ka. During the coldest stages of the last glacial, only the first few meters of the Boom Clay were frozen without considering snow or vegetation. The permafrost depth with vegetation (tundra) and snow is at least 60 m less.