NSCAT Ku-band microwave observations of the Arctic sea ice cover are described on their potential use for estimating ice extent and timing of spring melt. A simple comparative analysis of the NSCAT Arctic sea ice extent and high-resolution Radarsat imagery suggests that the SSM/I 25% ice concentration contour appears to be a good indicator of the winter Arctic ice edge. For spring melt-onset, a comparative study of NSCAT sea ice observations and NCEP/NCAR surface air temperature indicates that Ku-band backscatter of the snow cover over multiyear ice has a clear and steep change as the surface air temperature rises above freezing. This signature of melt onset should provide useful large-scale estimates of the dates of melt onset with spaceborne scatterometer data. A more extensive validation of the potential of this dataset is suggested. ¿ 1998 American Geophysical Union