Coastal Erosion at Kharasavey Gas Condensate Field, Western Yamal Peninsula

The purpose of the work is to quantify the process of the Kara Sea permafrost coasts destruction near the Kharasavey settlement and the port of Kharasavey gas condensate field at Western Yamal under the conditions of changing climate and human impact, and to estimate possible rates of further destruction. For this purpose, the spatial and temporal variability of coastal destruction rates has been investigated since 1964, the geomorphological and permafrost structure of the coastal zone has been studied, the time series of the main hydrometeorological parameters affecting the retreat rates have been calculated. The estimation of coastal retreat rates was carried out on the basis of the field data of the authors and analysis of multitemporal aerospace imagery (1964, 1977, 1988, 2006 and 2016). To characterize the hydrometeorological factors of the coastal dynamics, the wave load on the coastal zone (from 1979 to 2016) was calculated using data on the direction and speed of the wind and the duration of the ice-free period. To assess the thermal factor of coastal destruction, the freezing and thawing indexes were used. Since the 1980s there is an increase in the hydrometeorological potential of the coastal destruction. An increase in the annual sum of negative temperatures (freezing index) provides less cooling of deposits in winter period. With an increase in the sum of positive air temperatures (thawing index) this leads to accelerated thawing of sediments during the summer period, preparing the material for mechanical removal by waves. Due to the increase in the duration of the ice-free period and the frequency of winds with directions favourable for waves generation in the coastal zone, the total wave load on the coast increases. Intensive destruction of coastal segments composed of icy loams in 2006-2016 is due both to natural factors and to the human impact imposed on them (dredging in the mouth of Kharasavey River, the seizure of material for construction needs from the beach and coastal bluff). It is recommended to use tideflat and beach in the area of the Cape Burunny, located at a distance from the infrastructure of the port and settlement, as a source of sand material. Despite the low values of the hydrometeorological forcing of the coastal destruction in 1977-1988, it was during this period that the maximum retreat rates of the coast were observed. An analysis of the spatial arrangement of the retreated sections showed that the most likely cause of the increase in the rates of retreat was human impact (for instance, dredging for the needs of the port at the mouth of the Kharasavey River could led to a deficit of sediment in the northward section). The first detailed data obtained on the spatiotemporal variability of the coastal dynamics for this area allowed a joint analysis of natural factors and man-made loads affecting the rate of coastal destruction. A forecast was made for further development of the coast in conditions of continued development and climate change.