"The ice extent values are calculated from the ice type data from the Ocean and Sea Ice, Satellite Application Facility (OSISAF), where areas with ice concentration higher than 30% are classified as ice....
Sun., Nov. 16, 2014, "Sea ice extent in recent years (in million km2) for the northern hemisphere, as a function of date."
"Please notice, that the sea ice extent in this plot is calculated with the coastal zones masked out. To see the absolute extent, go to this page." [See plot below which includes ice concentration above 15%]
"Sea ice extent in recent years for the northern hemisphere.
The grey shaded area corresponds to the climate mean plus/minus 1 standard deviation."
"The plot above replaces an earlier sea ice extent plot, that was based on data with the coastal zones masked out. This coastal mask implied that the previous sea ice extent estimates were underestimated. The new plot displays absolute sea ice extent estimates. The old plot can still be viewed here for a while."
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DMI page notes for second plot: "Northern Hemisphere Sea Ice extent" [15% ice concentration]
"Total sea ice extent on the northern hemisphere during the past years, including climate mean; plus/minus 1 standard deviation. The ice extent values are calculated from the ice type data from the Ocean and Sea Ice, Satellite Application Facility (OSISAF), where areas with ice concentration higher than 15% are classified as ice.
The total area of sea ice is the sum of First Year Ice (FYI), Multi Year Ice (MYI) and the area of ambiguous ice types, from the OSISAF ice type product. The total sea ice extent can differ slightly from other sea ice extent estimates. Possible differences between this sea ice extent estimate and others are most likely caused by differences in algorithms and definitions."
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DMI page notes on first plot [30% ice concentration]:
"The ice extent values are calculated from the ice type data from the Ocean and Sea Ice, Satellite Application Facility (OSISAF), where areas with ice concentration higher than 30% are classified as ice.
The total area of sea ice is the sum of First Year Ice (FYI), Multi Year Ice (MYI) and the area of ambiguous ice types, from the OSISAF ice type product. However, the total estimated ice area is underestimated due to unclassified coastal regions where mixed land/sea pixels confuse the applied ice type algorithm. The shown sea ice extent values are therefore recommended be used qualitatively in relation to ice extent values from other years shown in the figure."...via Steven Goddard, 11/15/14, "Arctic Sea Ice Extent At Its Highest Level In Over A Decade"
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