Figure 11. (a) Simulated permafrost active layer depth (defined by the maximum of the monthly thaw depth in the permafrost region, m) and (b) the observed permafrost spatial distribution from International Permafrost Association (IPA). The 0 to 4 in (b) stand for no permafrost, continuous (90–100%), discontinuous (50–90%), sporadic (10–50%), and isolation (<10%), respectively.