The Eumetsat Ocean and Sea Ice Satellite Applications Facility provides a "reprocessed" data set of Arctic and Antarctic sea ice concentration for 1978-2009. Source data are the SMMR and SSM/I passive microwave brightness temperatures. Three algorithms are utilized: the Technical University of Denmark algorithm is applied to the SSM/I data from 1991 onwards; the Bootstrap and the Bristol algorithms are combined for the SMMR and SSM/I data for 1978-1991. The Bootstrap is said to have lower sensitivity to atmospheric noise in areas of open water (helping to delineate the ice edge), while the Bristol algorithm is applied due to its lower sensitivity to ice surface emissivity variability. In general, atmospheric effects are more pronounced for relatively low ice concentrations. More information is available in the documentation and publications linked below.
EUMETSAT Ocean and Sea Ice Satelitte Application Facility. Global sea ice concentration reprocessing dataset 1978-2009 (v1.1, 2011), [Online]. Norwegian and Danish Meteorological Institutes. Available from http://osisaf.met.no.
National Center for Atmospheric Research Staff (Eds). Last modified 20 Aug 2013. "The Climate Data Guide: Sea Ice Concentration data reprocessed from SSMR & SSMI, by Eumetsat." Retrieved from https://climatedataguide.ucar.edu/climate-data/sea-ice-concentration-data-reprocessed-ssmr-ssmi-eumetsat.