This site uses cookies. By continuing to use this site you agree to our use of cookies. To find out more, see our Privacy and Cookies policy.
Skip to the content

[IOP] A community website from IOP Publishing

environmentalresearchweb blog

Arctic sea ice: observations and models suggest open water in September by mid-2040s

by Liz Kalaugher

In 2016 Arctic sea ice extent set a new record low, and every single month that year had an Arctic sea ice extent more than two standard deviations – corresponding to over 1 million square km of ice – below the long-term mean. That’s according to Julienne Stroeve of the University of Colorado, US, and UCL, UK, speaking at the European Geosciences Union meeting in Vienna.

Stroeve, who came back from Arctic field work on Friday, reported that both the first year sea ice and the multiyear ice that she measured were thinner than usual. As she left, strong winds were starting to create open water. “I think it’s going to be an exciting summer,” she said.

As the ice thins, it becomes more vulnerable to atmospheric conditions. Since 2007 Arctic sea ice extent has shown larger variability, making it harder to predict the ice cover in September. But at some point the ice may become so thin that atmospheric circulation doesn’t matter anymore, Stroeve explained.

Over the long term, the ice has retreated by 14% per decade, with the ten lowest summer sea ice extents all occurring within the last ten years. And the last seven months, including January through March of 2017, have been the longest consecutive run of unusually low sea ice extents.

Stroeve’s calculations, based on field observations, indicate that each metric ton of carbon dioxide entering the atmosphere melts three square metres of ice. That makes the ice more sensitive to greenhouse gases than models suggest. And it reveals that emission of a further 1000 Gigatonnes of carbon dioxide (which would be likely to create a 2 degree temperature rise) would create an ice-free Arctic in summer. At our current emission rates of roughly 30-40 Gigatonnes per year, that would mean an ice-free Arctic in September by 2045.

This date agrees with a climate model-based projection by James Screen of the University of Exeter, UK, and his colleague Daniel Williamson, who estimated that the first ice free September will be in around 2046, for a temperature rise of 2.1 degrees. This date would come forward to 2040 if emissions were higher or be delayed until 2050 if they were lower. And natural variability makes it accurate only to within 20 years. Screen’s earliest possible ice-free scenario was in the mid-2020s, for a temperature rise of 1.7 degrees.

Screen has calculated that if we keep to the UN “stretch target” of 1.5 degrees of warming, the probability of the Arctic being ice-free in summer is less than 1%. But for 2 degrees of warming, the chances are 39%, or “toss a coin” as he put it, and for 3 degrees, the probability is 73%, “likely” in IPCC terms.

This is in line with field observations of ice extent being more sensitive to climate change than models project – Stroeve’s observation-based calculations projected an ice-free Arctic in summer for 2 degrees of temperature rise, whilst Screen’s modelling indicates a 39% chance.

So what’s our temperature rise trajectory? Business-as-usual emissions would bring a global average temperature rise of 3-5 degrees by the end of the century, Screen detailed, whilst current emissions pledges to the UN would see temperature rises of 2.6-3.1 degrees. We’ve already raised temperatures by 0.9-1 degrees so we have around half a degree to go before hitting the UN stretch target.

“If we really want to save Arctic sea ice, we need to push for 1.5 degrees, not 2,” said Screen.

This entry was posted in EGU 2017. Bookmark the permalink.
View all posts by this author 

Leave a comment

Your e-mail address will not be published.


  • Comments should be relevant to the article and not be used to promote your own work, products or services.
  • Please keep your comments brief (we recommend a maximum of 250 words).
  • We reserve the right to remove excessively long, inappropriate or offensive entries.

Show/hide formatting guidelines

Tag Description Example Output
<a> Hyperlink <a href="">google</a> google
<abbr> Abbreviation <abbr title="World Health Organisation" >WHO</abbr> WHO
<acronym> Acronym <acronym title="as soon as possible">ASAP</acronym> ASAP
<b> Bold <b>Some text</b> Some text
<blockquote> Quoted from another source <blockquote cite="">IOP</blockquote>
<cite> Cite <cite>Diagram 1</cite> Diagram 1
<del> Deleted text From this line<del datetime="2012-12-17"> this text was deleted</del> From this line this text was deleted
<em> Emphasized text In this line<em> this text was emphasised</em> In this line this text was emphasised
<i> Italic <i>Some text</i> Some text
<q> Quotation WWF goal is to build a future <q cite="">
where people live in harmony with nature and animals</q>
WWF goal is to build a future
where people live in harmony with nature and animals
<strike> Strike text <strike>Some text</strike> Some text
<strong> Stronger emphasis of text <strong>Some text</strong> Some text