A database for depicting Arctic sea ice variations back to 1850

Arctic sea ice data from a variety of historical sources have been synthesized into a database extending back to 1850 with monthly time-resolution. The synthesis procedure includes interpolation to a uniform grid and an analog-based estimation of ice concentrations in areas of no data. The consolidated database shows that there is no precedent as far back as 1850 for the 21st century's minimum ice extent of sea ice on the pan-Arctic scale. A regional-scale exception to this statement is the Bering Sea. The rate of retreat since the 1990s is also unprecedented and especially large in the Beaufort and Chukchi Seas. Decadal and multidecadal variations have occurred in some regions, but their magnitudes are smaller than that of the recent ice loss. Interannual variability is prominent in all regions and will pose a challenge to sea ice prediction efforts. Keywords: Arctic, climate change, ice extent, sea ice.