The Bootstrap Sea Ice Concentrations from Nimbus-7 SMMR and DMSP SSM/I-SSMIS, Version 4 data set, accessible through the NASA National Snow and Ice Data Center Distributed Active Archive Center (NSIDC
The NSIDC DAAC is retiring access to its legacy, on-premises data archive and transitioning to the NASA Earthdata Cloud as the primary data archive. View planned retirement dates here.