10.4.4.3 Permafrost
The permafrost thawing will continue over vast territories of North Asia under the projected climate change scenarios (Izrael et al., 2002b). The transient climate model simulations (Pavlov and Ananjeva-Malkova, 2005; FNCRF, 2006) show that the perennially frozen rocks and soils (eastern part of the permafrost terrain) and soils (western part of the terrain) may be completely degraded within the present southern regions of North Asia (see Figure 10.5). In northern regions, mean annual temperature of frozen soil and rocks and the depth of seasonal thawing will increase in 2020 by as much as 4°C for the depth of 0.8 m and by at most 2.2°C for the depth of 1.6 m (FNCRF, 2006; Izrael et al., 2006). The change in the rock and soil temperatures will result in a change in the strength characteristics, bearing capacity, and compressibility of the frozen rocks and soils, thaw settlement strains, frozen ground exploitability in the course of excavation and mining, generation of thermokarst, thermal erosion and some other geocryological processes (Climate Change, 2004).
Permafrost degradation will lead to significant ground surface subsidence and pounding (Osterkamp et al., 2000; Jorgenson et al., 2001). Permafrost thawing on well-drained portions of slopes and highlands in Russia and Mongolia will improve the drainage conditions and lead to a decrease in the groundwater content (Hinzman et al., 2003; Batima et al., 2005b). On the Tibetan Plateau, in general, the permafrost zone is expected to decrease in size, move upward and face degradation by the end of this century (Wu et al., 2001). For a rise in surface temperature of 3°C and no change in precipitation, most Tibetan Plateau glaciers shorter than 4 km in length are projected to disappear and the glacier areas in the Changjiang Rivers will likely decrease by more than 60% (Shen et al., 2002).