These valid ice masks provide a way to remove spurious ice caused by residual weather effects and land spillover in passive microwave data. They are derived from the National Ice Center Arctic Sea Ice Charts and Climatologies data set and show where ice could possibly exist based on where it has existed in the past. There are 12 valid ice masks, one for each month, in netCDF-CF 1.6 compliant files with all associated metadata. The data are on a 304 x 448 grid.