Counter defines the center date of time period of observations upon which chart is based (i.e. 1950, Mar 21-31).  Use buttons [>>] and [<<] to browse forward and backward in time. Use [Step]-menu to choose between weekly, monthly, yearly and decadal step during browsing. Use button [2x1] to switch to dual window mode to compare pairs of charts. You may also choose to browse statistics. Use [Scroll] checkbox to (dis)enable autoscrolling. Use [time] checkbox to switch scrolling forward and backward in time. Use buttond [+] and [-] to accelarate or slow down autoscrolling.

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Given array is based on processing 10-days period Arctic and Antarctic Research Institute (AARI)  sea ice conditions charts prepared in World Meteorological Organization SIGRID format (WMO, 1989) for 1953-1992 interval separately  for Arctic West and Arctic East (eastward to 110E). Layer of sea ice total concentration is depicted in polar stereographical projection.