Ongoing Arctic warming changes arctic landscapes in various ways. It potentially alters the organic matter supply to lakes in the Arctic. Arctic warming may increase vegetation density in the catchments of lakes and thus increase of the organic matter supply to the lakes can be expected. Furthermore, warming may cause an increase of ground temperature and deepening of the active layer in permafrost soils, and thus activate various cryogenic processes including thermodenudation (Leibman et al. 2015). We present results of study of colored dissolved organic matter (CDOM) in thermokarst lakes of the central Yamal peninsula (Western Siberia, Russia) and the interconnection of CDOM with lake and catchment characteristics. We used a complex approach including field observations, laboratory measurements, and high spatial resolution optical and synthetic aperture radar (SAR) remote sensing and geographical information system (GIS) data analysis. CDOM absorption and spectral slope values, and suspended particulate matter concentrations (SPM) in several thermokarst lakes were obtained during 2011 – 2015 field campaigns. Availability of very high spatial resolution (GeoEye-1, WorldView-2) and high spatial resolution (SPOT5) optical satellite images as well as high resolution TanDEM-X DEM data, TSX and ALOS PALSAR SAR satellite images for the study area allowed to produce a large dataset of lake and catchment-related parameters (n=18). CDOM absorption at 440 nm in 363 lakes was retrieved from optical satellite images (correlation with in-situ data: R^2=0.68, n=24) using the band ratio method of Kutser et al. (2005). We also detected that increased turbidity in some of the lakes due to wind events in some of the optical satellite acquisitions affect the accuracy of retrieved CDOM values. The statistical analysis “boosted regression tree” was applied in order to find the most important variables controlling the CDOM concentration in central Yamal thermokarst lakes. The results show the following most important variables: the lake area/lake catchment area ratio, the elevation of the lake (i.e., floodplain or non-floodplain lake), median value of the Normalized Difference Vegetation Index (NDVI) of the lake catchment, activity of thermodenudation (thermocirques above the shore line) and total snow water equivalent (SWE) in the lake catchment. In this analysis we used a representative data of approximately 350 square kilometers including all geomorphic terrace levels and the floodplains of Se-Yakha and Mordy-Yakha rivers. Annual concentrations of CDOM in Yamal thermokarst lakes also differed. We found the clear relation of CDOM absorption values to climatic controls (summer air temperature and atmospheric precipitation) and recent activation of thermocirque in the study region. The enhanced erosion of the lake cliffs and enhanced atmospheric precipitation may increase the inflow of fresh terrestrial organic matter into the lakes from the surrounding catchments. Activation of thermocirques controls the additional input of SPM and CDOM into the lake water influencing also the lake color. References: Kutser T, Pierson DC, Kallio K, Reinart A, Sobek S. 2005. Mapping lake CDOM by satellite remote sensing. Remote Sensing of Environment 94: 535–540 DOI:10.1016/j.rse.2004.11.009 Leibman MO, Khomutov AV, Gubarkov AA, Mullanurov DR, Dvornikov YA. 2015. The research station “Vaskiny Dachi”, Central Yamal, West Siberia, Russia – A review of 25 years of permafrost studies. Fennia 193: 3–30.