Twentieth century sea ice data from the Nordic Seas (the Atlantic Sector of the Arctic) are examined using a simple index of variations in sea ice extent. The index measures overall sea ice extent variations in the Nordic Seas between 1901 and 1977. Variations in the marginal ice zone during the melt season are shown to reflect regional air temperature changes. Reduction of the index data using principal component analysis highlights sub-rcgional heterogeneity in melt season sea ice extent variations. An important spatial pattern of variation is one in which sea ice extent in the Barents Sea varies out of phase with that in the central Greenland Sea. This alternating pattern has a quasi-periodicity of around three years. Time series analyses of other sea ice records indicate significant quasi-periodicities in the region of between 3 and 4 years and 2.5 years. Three years may be a key time scale of variation in the Atlantic Sector of the Arctic seasonal sea ice 7one.
KEY WORIIS Sea ice index Arctic Nordic Seas Greenland Sea Barents Sea
The research discussed here was undertaken mostly while the author was working in the School of Environmental Sciences and Climatic Research Unit of the University of East Anglia, Norwich.