Compléter Complete polarpedia termVersion en ligne Fill in the gaps in polarpedia term - SEA ICE EXTENT par Anna Wielgopolan 1 median decreased decade Arctic Sea Ice Extent ( SIE ) index [ mln km2 ] provides a quick look on changes in sea ice in the . It provides daily , consistently processed ice extent and concentration from images taken by Nimbus 7 satellite since 1979 . The values of the SIE Index are calculated by summing the area of all grid cells 25x25km with 15% or greater ice concentration . The daily index shows ice extent with an outline of the typical extent for that day based on a 30 - year ( 1981 - 2010 ) . Since 1979 winter Sea Ice Extent in the Arctic has about 3 percent per .