Thermal State of Permafrost in the Northern Yakutya: modern state and dynamic during the last 50 years

One of the fundamental tasks of permafrost science is investigation of permafrost responce on the climate changes. Geothermal observation in the boreholes on the Yakutian coastal lowlands carried out since 80th years of the last century. Existant network allows us to estimate both spatial and temporal changes of the geothermal field. Investigated region covers the area from the Lena delta to Kolyma and characterized by cold continental climate (mean annual air temperature -13.5 to -14°C) and continuous permafrost distribution. Active layer 0.3-1 m. Recently, the network for continuous geothermal observation was established. It includes 10 boreholes located on the different latitudes, natural zones and landscapes. Modern thermal state of permafrost in this region is following: Mean annual ground temperature on the top of rest of Late Pleistocene accumulative planes varies in the range from -12.3° on the latitude 72°50' north to -9.9° on the latitude 69°30' north. Latitudinal zonality here is about 1° on the degree of latitude. Within the Alas depression mean annual ground temperature is a little bit warmer (-10° on the 71°40' north and - 7° on the 68°50' north). Comparison of modern observations and published data shows that most significant changes of the geothermal field take place on the Kolyma lowland. Since the 1980th permafrost temperature increase here on 1.5-2°C. At the same time thermal state of permafrost in the western part of region is more stable. Also there are some sites where modern landscape changes (vegetation succession) leads to the stabilization of permafrost temperature. Current research supported by NSF grants ARC-0520578 and ARC-0632400.