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 illustrate a clear decreasing trend in sea ice extent since 1978, with annual variations
of approximately 1 million square kilometres or less, until September 2007. The September 2007 ice
extent set a new minimum record with about 25% less ice that the preceding year. 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
(NSIDC).
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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.
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