Arctic Ice

The area covered by Arctic sea ice

Graph: The Average September Area of Arctic Ice (NSIDC)
Graph: The Average September Area of Arctic Ice (NSIDC)
  • The graph shows the average of the “Area of Arctic Sea Ice during September” each year.
  • The area shown is in millions of square kilometres.
  • The yearly “September extent” is shown as the area covered by Arctic sea ice reaches a minimum during September.  The area increases during winter and decreases in summer.

The average September extent of Arctic Sea Ice is declining at 13.7% of the 1979 to 2000 average per decade.

The latest graphs of sea ice extent show the same decline.
See the latest Arctic Sea Ice graph.

Arctic ice reflects light, cooling the Earth

“Arctic ice plays an important role in maintaining the Earth’s temperature. The shiny white ice reflects light and heat that the ocean would otherwise absorb, keeping the Northern Hemisphere cool.”
(US National Snow and Ice Data Centre: NSIDC)

Warming of the Arctic is causing further warming

A dangerous spiral is becoming established in the Arctic: warming of the Arctic is causing further warming.

More global warmingMore ice melt
More open water & more sunlight absorbed. Less ice & less sunlight reflected.

This cycle is an amplifying feedback loop in which:

  • Global warming tends to increase temperatures in the Arctic.
  • This tends to melt the Arctic sea-ice, decreasing the amount of sunlight reflected away from the Earth.
  • This tends to increase the area of open water in the Arctic, and increase the amount of sunlight that the Arctic absorbs.
  • This tends to add to global warming, and the cycle repeats. 

Note that this feedback can run in reverse, with cooling leading to more sea ice, leading to the reflection of more sunlight, leading to further cooling.

The Arctic is warming fast

The Arctic has warmed twice as fast as the rest of the globe.
It is not sustainable for us to have Arctic sea ice decreasing by 13.7% per decade.

Arctic Sea Ice Area: Daily graph

See the latest daily ice cover changes over the current calendar year – and compare this to previous years on the “US National Snow and Ice Data Centre” (NSIDC) web page.

Here is a photo of this interactive web page on 6 April 2015.
You can click on the graph to enlarge it.

Graph: Arctic Sea Ice Extent (NSIDC)
Graph: Arctic Sea Ice Extent (NSIDC)
  • The graph shows “Arctic Sea Ice Extent”: the area over which there is more than 15%  of sea ice, measured in “millions of square kilometres”.
  • The dotted green line shows the sea ice area for each day of the record low year of 2012.  You can see that the ice area was greatest in mid-March 2012.  It was lowest in mid-September.
  • The blue line from 1 Jan to 5 April shows the ice cover for 2015.  The 2015 line ends on 5 April as I took the photo on 6 April.
  • The thick black line is the average extent for each calendar day from 1981 to 2010
  • The grey area on the graph shows two standard deviations on each side of the average.
  • This NSIDC web page is interactive, e.g. you can click on any year in the list on the right of the page, to see how ice cover moved over that year.


A regime shift is taking place as the Arctic sea ice melts (ABC: 13 Jan 2021)

Crash course: Arctic Sea Ice: US National Snow & Ice Data Centre (NSIDC)

Arctic sea-ice loss accelerates Arctic warming: Scientific American: 2010

Updated 13 Jan 2021

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