Abstract. In 2008, an information portal was developed, which presents and annually updates data on active-layer thickness (ALT) measurements at Russian sites included in the international CALM monitoring project. The data presented on the portal serve as a basis for the preparation of annual Climate Reports published by Roshydromet. The analysis of the data for all years showed that positive ALT trends are observed at 69 out of 71 monitoring sites. They are most pronounced in the north of the European territory of Russia (up to 37 cm/10 years) and in Western Siberia (up to 48 cm/10 years). In the other sectors, they are noticeably lower against the background of large interannual variability. Attribute analysis showed that in the north-European Russia the main factor is the increase in air temperature, while in Siberia, especially in Yakutia, the increase in winter precipitation plays a more important role.     

Keywords: permafrost, monitoring, active-layer thickness, CALM monitoring sites, Russian North