ИСТИНА

In the Pechora and Kara Sea, two types of coastal permafrost dominate. The first one is characteristic for typical thermoabrasional coasts. As a result of relatively quick coastal erosion on the thermoabrasional shores, a so-called “overhang” of the coastal frozen grounds is conserved in the contact zone between the sea and the ice-sea bottom, which is usually spread 1-2 meters into the sea. The annual contact of sea ice with the bottom ground helps to preserve this permafrost “overhang”. Seawards, up to the depths of 15-20 m, thawed grounds usually prevail. The heat impulse of the warm period is spread namely up to this depth. During the last 6 thousand years, the shallow water area has thawed completely. For greater sea depths, numerous relicts of ancient sub-aerial permafrost have been documented at depths not less than 10 m from the bottom ground surface. The second type of coastal permafrost is characteristic for coastal bars and island barriers, which are wide-spread in the south of Pechora Sea and on the Yamal coast of the Kara Sea. In contrast with the thermoabrasional coasts, the “overhang” here is represented by seasonally frozen grounds forming in the contact zone between the sea ice and the bottom. Constantly frozen ground is represented only in the central part of the coastal barrier. No frozen grounds are usually observed behind the barrier, on the laida and the lagoon, mostly influenced by the sea. The coasts of the Pechora and Kara Seas, which are composed of disperse deposits, are not resistant to erosion. In natural conditions such coasts may retreat with a rate of 1 to 2 m a year. Under the influence of human activities, this rate can double and even triple. Over the last twenty years the human impact on the natural coastal geosystems has noticeably increased due to the latest oil and gas development on the sea shelf and coasts of the Russian North. A range of facilities – oil terminals for drilling and production platforms, submerged pipelines, ports and other industrial features and residential infrastructure are currently being operated in the coastal and shelf zones. In most of the cases, permafrost or litho- dynamic features of the coastal zone had not been taken into account during the construction or operation of these facilities. This results in a disturbance of the sediment transport in the coastal zone, which triggers active erosion of both the shore itself and the coastal slope beneath. The operated facilities themselves are then threatened as their destruction is possible and often no new facilities can be constructed and function in the area afterwards. The operating companies have to bear forced nonmanufacturing expenses to protect or move their facilities of oil and gas industry to new areas. There is a whole series of examples for of the Pechora and Kara Seas where human impact has already brought in negative effects which have lead to permafrost degradation and erosion rate increase.