The timing and duration of ice-onset on lakes and river channels is a relevant climate signal since it is strongly driven by the air temperature. Space-borne imaging radar is a suitable tool for the detection of freeze processes, as the backscattering of radar waves is highly dependent on the dielectric properties of the surface. For this study, a time series of high-resolution TerraSAR-X images recorded during fall and winter 2012 was analysed. The images cover several lakes and river channels located in the central Lena Delta, North Siberia, Russia. On the basis of radar signature analysis and of classification results from visible inspection of the images we discuss the potential of change detection and intensity-thresholds for the separation of thin ice covers and water surfaces.