Arctic Ice

Arctic ice reflects light, cooling the Earth

“The 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)

The average September extent of Arctic Sea Ice

Graph: The Average September Area of Arctic Ice (NSIDC)
Graph: The Average September Area of Arctic Ice (NSIDC)

See the latest Arctic Sea Ice graph.

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

The average September extent of Arctic Sea Ice is now declining at a rate of  13.7 percent of the 1979 to 2000 average per decade.

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.

Diagram: The amplifying feedback loop formed when Arctic temperatures increase, ice melts and less sunlight is reflected

This is an amplifying feedback cycle in which:

  • Global warming tends to increase temperatures in the Arctic
  • This tends to melt the Arctic sea-ice and so decrease the amount of sunlight reflected away from the Earth.
  • This tends to increase the area of open water in the Arctic and so increase the amount of sunlight that is absorbed. (The water is far less reflective than the darker water.)
  • 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 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 percent per decade.

Day by day Arctic Sea Ice Extent

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 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 NSDIC 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.


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

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

Updated 9 Sep 2018

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