Abstract: Using sea ice concentration data published by National Snow & Ice Data Center (NSIDC), interannual and interdecadal variability in the extent of Arctic sea ice between 1979 and 2012 is analyzed. We demonstrate: 1) the linear rate of decline of sea ice extent (SIE) is fastest during autumn, followed by summer, winter and spring. Melt speed from 2000 is greater throughout the year with the exception of spring, compared with the period of time between 1979 and 2000. 2) Melt speed in the Pacific sector is greater during summer and autumn due to loss of multiyear ice, whereas in the Atlantic sector, melt speed is greater during spring and winter because of rising sea temperatures. 3) The extent of melting is greater in the Eastern Hemisphere than in the Western Hemisphere, rendering the Northeast Passage navigable earlier than the Northwest Passage. The decrease of melting rates in spring months over the recent years was attributed to the factors in the Western Hemisphere.  4) The ice cover between 1989 and 1998 was found to be identical with its climatological pattern, while between 1979 and 1988 the spatial range in Barents Sea and East Siberian Sea was greatest. In contrast, significant decrease of sea ice concentration was observed between 2009 and 2012 with a larger magnitude in the East Hemisphere, especially in Chukchi Sea during summer and autumn. The concentration of sea ice in the Bering Sea, however, was greater during spring due to southward wind driven. Finally, 5), the abrupt change in Arctic sea ice cover is more obvious during winter and spring than during summer and autumn. The abrupt year change in 2003. According to the wavelet analysis, the periodicity of sea ice extent change is almost 6 years.

Key words: sea ice, concentration, sea ice extent, spatial distribution, abrupt change