Arctic sea ice is in the midst of a record-breaking melt season. This is yet another symptom of human-caused climate change progressing much faster than scientists anticipated.
Every year, the frozen surface of the Arctic Ocean waxes and wanes, covering the largest area in February or March and the smallest in September. Over the past few decades, these September minima have been getting smaller and smaller. The lowest sea ice extent on record occurred in 2007, followed closely by 2011, 2008, 2010, and 2009. That is, the five lowest years on record all happened in the past five years. While year-to-year weather conditions, like summer storms, impact the variability of Arctic sea ice cover, the undeniable downward trend can only be explained by human-caused climate change.
The 2012 melt season started off hopefully, with April sea ice extent near the 1979-2000 average. Then things took a turn for the worse, and sea ice was at record or near-record low conditions for most of the summer. In early August, a storm spread out the remaining ice, exacerbating the melt. Currently, sea ice is significantly below the previous record for this time of year. See the light blue line in the figure below:
The 2012 minimum is already the fifth-lowest on record for any day of the year – and the worst part is, it will keep melting for about another month. At this rate, it’s looking pretty likely that we’ll break the 2007 record and hit an all-time low in September. Sea ice volume, rather than extent, is in the same situation.
Computer models of the climate system have a difficult time reproducing this sudden melt. As recently as 2007, the absolute worst-case projections showed summer Arctic sea ice disappearing around 2100. Based on observations, scientists are now confident that will happen well before 2050, and possibly within a decade. Climate models, which many pundits like to dismiss as “alarmist,” actually underestimated the severity of the problem. Uncertainty cuts both ways.
The impacts of an ice-free Arctic Ocean will be wide-ranging and severe. Luckily, melting sea ice does not contribute to sea level rise (only landlocked ice does, such as the Greenland and Antarctic ice sheets), but many other problems remain. The Inuit peoples of the north, who depend on sea ice for hunting, will lose an essential source of food and culture. Geopolitical tensions regarding ownership of the newly-accessible Arctic waters are likely. Changes to the Arctic food web, from blooming phytoplankton to dwindling polar bears, will irreversibly alter the ecosystem. While scientists don’t know exactly what this new Arctic will look like, it is certain to involve a great deal of disruption and suffering.
Daily updates on Arctic sea ice conditions are available from the NSIDC website.
ClimateSight 
Thank you Kate for this important post.
Might this suggest that we should extend our climate models to include both increased time and black swan events?
Is it time to construct an open source climate modeling project?
I would be a big fan of an open source climate modelling project. However, I think it has been tried before and never got off of the ground.
As for black swan events, how are you going to include them? By their very nature they are unknowable.
Nice one Kate. The thing that strikes me most about that second graph is that the last 5 years have all been greater than -2Std. Dev. removed from the 1979-2000 average. This suggests to me that a shift has occurred – the 1979-2000 average no longer applies. This is what Hansen et al (2012) have found to be the case with temperatures, so why would be surprised?
http://lackofenvironment.wordpress.com/2012/08/07/the-reason-we-keep-getting-double-six/
Thanks for the summary.
Two additional points that I believe may be the largest threats from the seasonal disappearance of Arctic sea ice:
(a) Disruption of NH wind patterns. There is increasing attention given to this, with some suggestion that open Arctic ocean makes the jet stream wavier, which in turn is more likely to get “stuck” in a blocking pattern that leads to more extreme weather.
(b) Acceleration of methane thaw in both terrestrial permafrost and (possibly) submarine methane clathrates.
Typo alert:
“While scientists don’t know exactly what this new Arctic will look like, it is certain to involve a great deal of disruption and suffering.”
should be:
“While scientists don’t know exactly what this new Arctic will look like, it is certain to involve a great deal of disruption and suffering, except on the part of the oil industry, who will be celebrating their access to new riches-at-the-cost-of-everyone-else all the way to the bank.”
Where have you been, Pendantry? Now that you’re back, I realise how much I have missed your masterful use of irony and sarcasm! In all honesty, I think there are few that come close to your level of expertise; as is surely evidenced by this remark (of yours)!
Aww… shucks.
It’s worth also mentioning the impact it appears to be having on Northern hemisphere weather conditions and the jet stream. This is ongoing research of course, but it looks likely the stickiness of the jet stream – and thus much of the extreme weather events right across the US, UK and Europe – may be connected to these changes in the arctic. I suspect it means we’re committing ourselves to many decades of chaotic weather flipping between drenchings and bakings and occasionally mixing the two. I have no evidence for that except that poked complex systems don’t usually manifest stable behaviour until some while after you stop poking them.
well done kate
Kate, it may be an indication of how fast change is happening. In the 2 weeks since you wrote: “The lowest sea ice extent on record occurred in 2007, …” The record has fallen, is it worth inserting a note?
Readers will follow a link to that correction anyway. “Arctic sea ice extent breaks 2007 record low” at http://nsidc.org/arcticseaicenews/