A discontinuous record of monthly sea ice area is calculated from a series of satellite-based sensors, covering the period from 1974 to 2015 with missing years for 1975, 1977 and 1978. Sea ice area for the period 1973 to 1977 was determined from daily brightness temperatures monitored by the ESMR instrument mounted on the NIMBUS-5 satellite (Parkinson et al., 2004). For the period January 1979 to May 2015, sea ice observations were obtained from the SMMR and SSM/I and SSMIS instruments mounted on various satellite platforms (Cavalieri et al., 1996, updated yearly). These data are freely available from the US National Snow and Ice Data Centre (NSIDC) website (Cavalieri et al., 1999; Fetterer et al.).