Editing IPCC:AR6/WGII/Chapter-10 (section)

===== 10.4.6.3.7 Permafrost thawing and associated risks =====

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In Northern Eurasia, observed and projected climate-change impacts are especially pronounced. On land, the presence of permafrost, which occupies substantial areas of eastern Russia, Mongolia and mountain regions of China, creates specific challenges for economic development and human activities. By 2050, it is likely that 69% of fundamental human infrastructure in the Pan Arctic will be at risk (RCP 4.5 scenario)( ''medium confidence'' ), including more than 1200 settlements ( [[#Hjort--2018|Hjort et al., 2018]] ). The majority of the population and the absolute majority (85%) of large settlements on permafrost are located in Russia, and 44% of those are expected to be profoundly affected by permafrost thaw by 2050 ( [[#Streletskiy--2019|Streletskiy et al., 2019]] ; Ramage et al., 2021). Under RCP8.5, the climate-induced decrease of bearing capacity and, in regions with ice-rich permafrost, thaw subsidence, is projected to affect 54% of all residential buildings on permafrost with a combined worth of 20.7 billion USD; 20% of commercial and industrial structures and 19% in critical infrastructure with a total worth of 84.4 billion USD (Streletskiy, 2019). Transport infrastructure in Russia and China are impacted by thaw subsidence and, to a lesser degree, from frost heave, which add significant operational costs and limit accessibility to remote settlements (Porfiriev et al., 2019; Ni et al., 2021).

Especially in Russia, significant populations and fixed infrastructure assets are located in urban centres on permafrost that is degrading significantly. Two major risks associated with permafrost degradation are loss of permafrost bearing capacity and ground subsidence ( [[#Streletskiy--2015|Streletskiy et al., 2015]] ). The former determines the ability to support foundations of buildings and structures and is a vital characteristic of sustainability of the economic centres, while the latter impacts the ability of critical infrastructure (roads, railroads) to provide transportation and support accessibility of remote populations and economic centres on permafrost. The proximity of some settlements to the coasts or areas with uneven topography may further increase risks associated with permafrost degradation as ice-rich coasts characterised by high rates of coastal erosion, while settlements located on slopes may experience higher rates of mass wasting processes.

Changes in climate have resulted in permafrost warming and increased thaw depth in undisturbed locations ( [[#Biskaborn--2019|Biskaborn et al., 2019]] ), but in built up areas these transformations have been exacerbated by human activities ( [[#Grebenets--2012|Grebenets et al., 2012]] ). Norilsk, the largest city built on permafrost above the Arctic Circle ( [[#Shiklomanov--2017b|Shiklomanov et al., 2017b]] ), was found to have one of the highest trends of near-surface permafrost warming ( [[#Streletskiy--2012|Streletskiy et al., 2012]] ). Anomalous high temperatures and earlier snowmelt in 2020 may have contributed to oil storage collapse and the resulting spill of 20,000 tons of diesel fuel in Norilsk area (Rajendan et al., 2021). The ability of foundations to support structures has decreased by 10–40% relative to the 1960s in the majority of settlements on permafrost in Russia ( [[#Streletskiy--2012|Streletskiy et al., 2012]] ) and is expected to further decrease by 20–33% by 2050–2059 relative to 2006–2015 ( [[#Streletskiy--2019|Streletskiy et al., 2019]] ).

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