ИСТИНА

Arctic coasts composed of perennially frozen deposits are extremely sensitive to climate and human impact. They retreat with the average rates of 1 – 2 meters per year depending on climatic and permafrost conditions. Recent decades, there is a tendency to increase of coastal retreat rates, especially it is noticeable in the area of resource development. Based on multi-temporal ultra-high resolution aerial and satellite imagery we consider the coastal dynamics during several time lapses, in natural condition and under the human impact, and discuss their temporal variability. Besides planimetric (m/yr), we calculated volumetric (m2/m/yr) retreat of erosional coasts using ArcticDEM. In addition, we estimated influence of geomorphological, lithological and permafrost composition of coasts on spatial ariations of their dynamics. The coasts of the Ural key site retreat with the higher mean rates (1.2 m/yr and 8.7 m2/m/yr for 1964 – 2016) in compare with the Yamal key site (0.3 m/yr and 3.7 m2/m/yr for 1968 – 2016) due to their complex lithology, higher ice content and lower coastal bluffs. Retreat of Ural cost is faster and of Yamal coast is slower than the average linear rate for the entire Arctic (0.5 m/yr). In planimetric rates 2 – 4m laida and low (6 – 8 m height) terraces retreat faster than high (more than 10 m height) terraces, on the contrary in volumetric scale retreat of high terraces is much more considerable. Concerns to lithology, sandy coasts are eroded more intensively than loamy and peaty. A clear contribution of outcrops of massive ice beds and wedge ice to coastal dynamics has not been detected. Since 1960s the coastal retreat shows a growth of rates on the both coasts, that we associate with the climate warming in the Arctic. Beyond that, during the period of 1960s – 2005 the growth was slight, while during 2005 – 2016 it was rapid, that may be explained by the enhanced wave and thermal action or by the beginning of the resource development in last decade. Originally accumulative sectors of coasts remained relatively stable during the period of 1960s – 2005, but a considerable part of them begun to retreat after 2005, that we relate with the changing weather conditions and/or the emerged human impact.