In recent history, sea ice coverage in the Arctic has decreased. One of the SOS datasets in this demo shows three dates in September from 1987 through 2013.
Since September has the minimum sea ice extent, comparing September from a number of years allows scientists to observe patterns.
2012 saw the lowest recorded sea ice minimum, surpassing the previous lowest year, 2007. 2012's extent was about 16% less than that of 2007.
2007-2012 saw the six lowest sea ice minimum extents in recorded history.
The graph to the left shows Arctic sea ice extent from January through December. The different types of lines represent different years, with the solid black line representing the average from 1981-2010. 2012 shows the lowest extent. 2013 and 2014 are higher than 2012, but still below the average.
Although Arctic sea ice is decreasing, sea ice extent in Antarctica is actually increasing slightly.
The change has been less drastic in the Antarctic, with a 1.1% increase per decade, compared to the 3-4% decrease per decade in the Arctic.
However, this increase in sea ice extent has not been consistent over the entire continent of Antarctica. Some areas have seen an increase in coverage, while other areas have seen a decrease.
It is uncertain whether this trend in Antarctica represents a meaningful change (like the decrease of extent in the Arctic), due to the high amount of variability, both in geography and year-to-year variability in extent.
In addition to a change in overall extent, recent years have seen a decrease in thickness of Arctic sea ice.
The graph at right shows satellite images of Arctic sea ice from 2004-2008. Red indicates the thickest ice, while dark blue indicates thinner or no ice. Also graphed are thicknesses of multi-year ice, first-year ice and overall thickness.
