Sea Ice Extent Minimum.
The graphics on the right show the mean September sea ice extent on the northern hemisphere.
The plotted values correspond approximately to the sea ice area that 'survived' the summer melt
in the respective years
The graph illustrates a decreasing trend in sea ice extent since 1978, with annual variations
of occationally more than 1 million square kilometres. The 2012 sea ice minimum extented set a new minimum record.
The 2012 September minimum ice extent was only approximately half the mean sea ice extent from the period 1979-2000, - often
referred to as a relative stabil period for the sea ice extent. The blue trend
line in the figure has a negative slope of approximately 60000 km2 per year. The data are provided
by National Snow and Ice Data Center's web site
Mean September sea ice extent in millions of km2 for the northern hemisphere
since 1978 (NSIDC). This is a comparable measure to annual minimum sea ice extent.
The blue line indicate the decreasing trend in September ice extent.