Thermal properties of sediments in the East Siberian Arctic Seas: A case study in the Buor-Khaya Bay

The temperature and thermal properties of shelf sediments from the East Siberian, Laptev, and Kara Seas were determined from field investigations. The sediments were in an unfrozen cryotic state (ice-free) and showed negative temperatures, ranging from −1.0 to −1.4 °C. These temperatures imply the presence of widespread subsea permafrost from the shelf to the continental slope of the East Siberian Arctic Seas, reaching ~1000–1500 km off the coast. The thermal conductivity and heat capacity of sediments (up to a depth of 0.5 m) from the Eastern Arctic Seas averaged 0.95 W/(m·K) and 3010 kJ/(m³·K), respectively. We also conducted temperature and thermal conductivity measurements of the upper sediment horizons of the permafrost in the Laptev Sea shelf (drilling depth of 57 m). The analysis of sediment cores ensured the determination of thermal conductivity with depth. We also analyzed the influence of moisture content, density, particle size distribution, salinity, and thermal state on sediment thermal conductivity. The thermal conductivity of unfrozen cryotic (ice-free) sediments was predominantly dependent on the contents of silt and clay. In general, unfrozen cryotic sandy sediments had a thermal conductivity range 1.7–2.0 W/(m·K), a moisture content of ~20%, and a density of 2.0–2.2 g/сm³. Frozen (ice-containing) sediments showed higher thermal conductivities of 2.5–3.0 W/(m·K), with a density of 1.9–2.0 g/cm³ and a moisture content exceeding 25–30%. The high thermal conductivity of sand was associated with low salinity (0.1–0.2%), high ice content, and moderate unfrozen water content.