Brief communication: Evaluation of the ESA CCI+ ESMR v1.1 sea-ice concentration product

Abstract. I evaluated a novel NIMBUS-5 Electrically Scanning Microwave Radiometer (ESMR) sea-ice concentration (SIC) data product. 50 Landsat-1 Multispectral Scanner (MSS) images obtained in the Northern Hemisphere during 1974 were manually classified into open water and ice, mapped onto the ESMR product's grid (25 km resolution) and used to compute Landsat-1 SIC. The resulting ∼3300 grid cells, covering mostly compact sea ice, have a mean difference (median), standard deviation, and linear correlation coefficient of −1.4 % (0.0 %), 6.0 %, and ∼0.9, respectively. This suggests using this novel ESMR SIC data product as an extension of existing SIC climate data records back in time.