Sea Ice Extent (SIE) index [mln km2] provides a quick look on changes in sea ice in the Arctic. 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) median. Since 1979 winter Sea Ice Extent in the Arctic has decreased about 3 percent per decade.