ИСТИНА

The coastal retreat is occurred due to thermal erosion which could consist of thermal denudation or/and thermal abrasion of the coastal deposits. Thermal abrasion intensity depends on several main factors in the permafrost area, i.e.: the tidal activity mostly and ice regime, properties and composition of the seashore rocks, seawater temperature and its salinity. Thermal denudation depends on radiation-heat transfer to the surface of slope, mechanical properties of grounds, ice content in ground and lithology of deposits. It also influenced by the rate of debris transfer by seawater to the accumulation zone. The ice activity of the sea effect significantly the retreat of the seashore (Are, 1980; Zachar, 1982; Dallimore et al., 1996; Jones et al., 2009; Arp et al., 2011 et al). On the other hand, the most important phenomena are ice cover duration and ice coverage during the summer season. The easiest to erode are sand, loam clays and silty clay. These sediments are typical for marine and alluvial genetic types of Quaternary sediments on Kara seacoast. They often have high ice content represented by ice layers, ice wedges and massive ice texture of frozen ground (Badu et al., 2013; Belova, 2014; Isaev et al., 2016). The debris transfer by the seawater is the considerable factor of the thermal abrasion activity as well as for the thermal denudation process.