ИСТИНА

The city of Igarka is located in Arctic Siberia, in Krasnoyarsk region, Russia. The city is situated near the southern boundary of continuous permafrost, in forest tundra. Landscape conditions, warming influence from the nearby Yenisei River and local climatic conditions through the Pleistocene-Holocene resulted in the formation of the underlying discontinuous permafrost. The discontinuous permafrost zone is characterized by the presence of tundra spaces with permafrost and forested areas without permafrost. The thermal regime under natural conditions outside city, range from -0,5 to -1 ºC in the forest-tundra, up to -1,5 ºC tundra parts (peat mounds).Permafrost in this region can reach up to 300 m thick. In loamy deposits, according to our observations, small ice lenses thickness is 5-7 cm occur. The natural landscape is characterized by two main cryogenic processes: frost heaving of grounds and thermokarst. The city if Igarka grew and developed both size and population until the collapse of the Soviet Union, followed by a crisis in all areas of city life. The port went into decline, the timber processing plant closed and the old areas of the city demolished or burned. Population has also undergone rapidly, including massive out migration, following the collapse of the Soviet Union to today: in 1931 - 3000 people; 1967 – 18000 p.; 1989 - 18820 (max.) p.; 1996 – 14900 p.; 2005 – 8000 p.; 2015 – 5117 peoples. Continued severe decline in population was contributed by decision of local government to close the city. The remaining buildings have significant geotechnical problems: the deformation of structures under differential settlement of frozen pile foundations, destruction of underground utilities, subsidence and frost-heaving on roads and sidewalks, collapsing bridges and others. As long as the city was developing, the timber plant processing, the port was active and the local Permafrost Laboratory operating, dangerous cryogenic processes in the built-up area were being monitored, the necessary engineering and permafrost geotechnical solutions were implemented to stabilized and maintained situation. After the city fell into decline, permafrost-ecological conditions also deteriorated. There is no apparent recovery of permafrost at the site of the demolished districts,it has re vegetated primarily as forest vegetation– indicator of taliks. When the historical section of the city was still populated there was regular snow removing and water drainage (precipitation 550 mm / year, of which 300 mm falls as snow),protecting underlying frozen ground. Nowadays, the ground is insulated by snow cover in the abandoned parts and there is some increase in water infiltration into the ground. These changes have triggered thermokarst processes causing increases surface water logging in the old quarter in Igarka central parts, have resulted in increased of deformation of the remaining buildings.Succession of non-tundra vegetation does not promote the conservation and restoration of permafrost (Fig. 1): the actively overgrown by parvifolia shrubs (increasing snow accumulation, minimized the influx of winter cold into the ground), tundra landscapes and natural pine forests are not reversed. Approximately 40% of the built-up area consisting of an abandoned sawdust storage area (they stretch 5 km along the Yenisei river), where the chemical decomposition of waste is going. In fact, if the city were to be revived, these areas cannot be used for a perspective development. It will be necessary to explore new territory for development. Is there any chance of revitalizing the city of Igarka as the base city with the development of oil and gas fields? How will local permafrost behave after the city was razed? What can be done to help quickly restore the "fragile" natural forest tundra and typical tundra landscapes? To investigate these questions have been carried out field observations and surveys, route works, full-scale study of permafrost in the Igarka permafrost museum and examination of archival materials. These annual field studies were complimented by remote sensing and repeated photography. This comprehensive evaluation of the socio-economic and environmental changes that have occurred in Igarka affords valuable perspective on a common situation facing a number of urban areas in the Russian Arctic.