That shouldnt’ be news if you’ve visited this site this summer. I’ve maintained a running series on this critical issue as I’ve been collecting and watching resources on it (August discussion, July discussion). The same can’t be said for the corporate media, of course. The Rocky Mountain News finally took note of the situation, but wrote only five short paragraphs on it. Thankfully, there is no “other side of the story” in the piece. I am going to discuss the situation in much more depth than the Rocky did, leaning on those resources I mentioned above.
First, take a look at a graphic of the arctic ice concentration, provided by the University of Illinois.
These data were measured by NASA satellites. This extent is very low when compared to the climatological standard, a comparison made by the National Snow and Ice Data Center in their most recent write-up. Another useful figure is a time series graph provided by the NSIDC. This is their figure as of today, comparing the climatological pattern, the 2007 lowest extent and 2005, the previous 2nd lowest extent. The easy conclusion climate change deniers and delayers will reach is 2008 wasn’t as bad as 2007, so everything is fine and we need not do anything. Anticipating that, allow me to present additional data.
The following graph is a one-year time series of northern hemispheric sea ice area.
Compared to the range seen throughout the year, this demonstrates that there is no significant difference between 2007′s record low figure and this year’s figure. Both plummeted to about 3 million sq. km. The lower part of the graph shows the deviation from the climatological mean. By mid-October last year, the deviation increased from -2 to -3. Dredging up old statistical lessons, last year’s event was incredibly rare. It remains to be seen if something similar occurs this year. The fact that we’re once again seeing a -2 deviation is indicative of how uncommon and serious this summer’s melt was. As I wrote about a couple of weeks ago, the Arctic ice became an island for the first time in recorded history.
In fact, this summer’s melt was actually more impressive than last year’s melt in one respect: the total amount of ice that melted was actually greater as the following graph demonstrates.
Early in 2007, the northern hemispheric ice area covered ~13.25 million sq. km. before melting away to 3 million sq. km. Earlier this year, the area covered by ice totaled 14 million sq. km. and again melted away to 3 million sq. km. That’s 11 million sq. km.! Imagine for a moment if the winter-time recovery wasn’t as strong as it was. The record low area seen last year would likely have been blown away by 750,000 sq. km. Actually, the more I look at the graph, the more it looks to me like this summer’s melt is a record in terms of total area melted in one season. The melt during the 1980s appears to be on the order of 10 million sq. km. per year. More than that, the general trend of this graph since 1979 is not good: the areal extent is heading further down with time.
That downward trend is more obvious when an anomaly graph is examined, as below.
1978-2000 serves as the climatological baseline. Since 2000, the downward trend of sea ice area can be easily seen. The anomaly for this year is currently teetering between “recovery” between 0 and -1 standard deviations and another temporary collapse toward -3 standard deviations, which happened last year. The difference betwen 2006-2007 and 2007-2008 is even more apparent on the graph also. The area anomaly recovered all the way to -0.5 from -3 in the span of six months last winter. This summer, due largely to the weakened ice from last summer, the ice melted to a similar areal extent as last year. The specific locations of melt were different, as expected, but the pattern held up, as scientists predicted early this year. The ice could delay its recovery due to the immense heat content of the oceans (relative to the climatological mean) once again. Sea surface temperature anomaly maps show very warm waters around Canada and Greenland, for example.
The three previous graphs are automatically updated daily at the University of Illinois at Urbana-Champaign’s Polar Research Group’s website.
I will say that it makes sense for the Rocky to wait to run this story until the melting season was over, as it allows for discussion to take place at a relevant point in time. I will also say again that it was nice to see an article citing scientific information only, not ideological rhetoric from deniers/delayers. The extent of coverage is, in my opinion, too light. This situation can best be described as unprecedented. That warrants more than five light paragraphs of coverage.
This story is far from over. Will ice be able to stage a recovery like it did last year, thin though it turned out to be? When will the next ice shelf calving occur? Ice extent is faring somewhat better in the southern hemisphere. When will that situation change? I’m also keeping an eye out for Greenland ice and glacier science articles.