A substantial part of the Asian coast line borders seasonally sea-ice covered waters. This chapter deals with the sea-ice cover along the northern shores facing the Arctic Ocean. Long-term year-round, sustained monitoring of this sea-ice cover is, on the one hand, crucial for shipping, off-shore activities, near-coastal transport, and marine safety. On the other hand, it is crucial to better understand recent and predict future sea-ice cover changes—changes which already have an impact on coastal erosion and regional as well as large-scale weather conditions. This chapter deals with observations of the sea-ice cover in the Siberian sector of the Arctic Ocean and its changes obtained from data of satellite passive microwave sensors. In addition, ways are presented to monitor polynyas and fast ice by means of microwave, optical, and infrared satellite remote sensing. Polynyas form frequently along the fast-ice cover of the Asian Arctic coast during winter. Their role for the Arctic Ocean sea-ice volume and ocean water mass modification is discussed. Furthermore, methods to estimate sea-ice thickness by means of satellite observations are described and illustrated for thin ice.