The Arctic includes an ocean covered by sea ice.
The area of Arctic sea ice is largest in March each year, and at its lowest each September.
The NSIDC also publish this graph, which is normally updated every day.
More graphs and other data are also available from the Arctic Data Archive System, operated by the Japanese Arctic Environmental Observation Center.
The total volume of Arctic sea ice has declined dramatically over time.
New research shows the decline in Arctic sea ice area since 1850:
Research suggests the remarkable decline of Arctic sea ice over the last century is far beyond anything seen for a long time.
(This post was updated August 2017)