ИСТИНА

The report presents the results of field and laboratory studies of permafrost transient layer characteristics within key study polygon of Eastern Chukotka coastal plains. The transient layer underlies the active layer and is characterized by an increased ice content, which determines its protective characteristics under conditions of short-period fluctuations in air temperature. Transient layer plays key role in thermokarst and thermal erosion, which are one of the most widespread dangerous processes for engineering facilities and infrastructure in the Arctic. Within the key area, the relief and Quaternary sediments were studied, surficial drilling was conducted, and the isotopic composition of the ice exposed in the boreholes was analyzed. As a result, variations in the transient layer thickness, its cryolithological structure, and the composition of stable oxygen isotopes were determined. Depending on the geomorphological conditions and lithological composition of the sediments, the transient layer thickness reaches 1.2 meters, while its gravimetric moisture content varies within wide range: from 70-150% in loamy sediments to over 1000% in peat. The stable oxygen isotopes composition (δ18O) in the transient layer is identical for all cores and varies from –11.4 to –14.0‰ that may be considered as diagnostic feature of this object in further studies.