The Ice in the Arctic region on the northern hemisphere during the past years is expanding swiftly. The extension of the ice values is calculated from the ice type data.
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 Ocean and Sea Ice, Satellite Application Facility (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.
The sea ice extent data from 1979 till today is composed by a Climate Data Record (CDR, OSI-409a), an Interim CDR providing updates with one month delay to the CDR (ICDR, OSI-430) and an operational setup that calculates sea ice extent for the period between the ICDR and today.
Further Reading: (Danish Meteorological Institute) — Arctic Sea Ice Extent
(OSISAF) —- Technical And Scientific documentation–Read the technical and validation report.