Evaluation of the HadISST1 and NSIDC 1850 onward sea ice datasets with a focus on the Barents-Kara seas

ABSTRACTIn recent years, long-term continuous sea-ice datasets have been developed, and they cover the periods before and after the satellite era. How these datasets differ from one another before the satellite era, and whether one is more reliable than the other, is important but unclear because the sea-ice record before 1979 is sparse and not continuous. In this letter, two sets of sea-ice datasets are evaluated: one is the HadISST1 dataset from the Hadley Centre, and the other is the SIBT1850 (Gridded Monthly Sea Ice Extent and Concentration, from 1850 Onward) dataset from the National Snow and Ice Data Center (NSIDC). In view of its substantial importance for climate, the winter sea ice in the Barents and Kara seas (BKS) is of particular focus. A reconstructed BKS sea-ice extent (SIE) is developed using linear regression from the mean of observed surface air temperature at two adjacent islands, Novaya Zemlya and Franz Josef Land (proxy). One validation illustrates that the proxy is substantially coher...