Weatherdem's Weblog

Bridging climate science, citizens, and policy

Global Ice Climatology

Leave a comment

A few weeks back, I wrote a post exploring the state of Arctic ice in a climatological sense.  I will repeat the main focus of that post first before moving on to something new.  In five years time, over 2 Trillion tons of ice has melted.  That’s ice over land, not the sea.  That melted ice eventually raises sea levels, unlike sea ice.  The rate of melt has exceeded the worst-case scenarios used in the last IPCC report.  The Arctic is losing ice mass over land at a faster rate than many expected.

Okay, now for something a little bit new.  In the comments of that post, Bryan St. James suggested I read about a post on Daily Tech Science dealing with Arctic sea ice.  That blog’s thrust: the areal extent of sea ice at the end of 2008 was the same as it was in 1979, so global warming advocates are being alarmists.  They point to the University of Illinois’ Arctic Research Center page’s long-term sea ice graph.  I applaud their citation of observational data.

First, I want to thank Bryan St. James for the comment and suggestion.  I read the post and looked at the graph again.

Second, I come to a different conclusion than DTS.  Or more accurately, my conclusion(s) go a bit further than those made on DTS.  The graph does show the areal extent of sea at the end of 2008 is at nearly the same value as it did at the end of 1979.  Without any other anaysis, it seems to be a rather empty conclusion to me.

I think what matters more is the minimum sea ice value per year.  In three of the past four years, for instance, the minimum area of sea ice was about 14-15 million sq. km.  The minimum of 1979 and 1980 was closer to 16 million sq. km.  The fact that the minima in recent years is noticably lower than it was 30 years ago is fairly significant to me.  The minima in recent years present a trend.  Last year, the minima wasn’t as low – it also was close to 16 million sq. km.  That value looks to be outside of the trend described above.  What I am waiting for then is the value of the minima this year.  The areal extent is currently decreasing.  When the minima is reached, some additional conclusions can be drawn.

Additionally, I would point out the bottom of the graph which shows the sea ice areal extent anomaly.  Again, the trend matters more than the singular value at any point in time.  And that trend is significant: a negative anomaly is present.  That anomaly has been present for the better part of 8 years now.  The past 8 years looks quite different than the previous 20+ years.  It’s that trend that has scientists and activists worried.  The trend was predicted by climate models, but it once again occurred much sooner than the models have indicated, on the order of 30-100 years.  That’s also significant.

Another point I want to make is the following: this is only one variable.  And it is likely to be a less important variable than sea ice volume is.  The areal extent has and will osciallate on a yearly basis, barring a catastrophic climate change which would leave the poles ice free year round.  The most recent studies I’ve read indicate that isn’t likely to happen for decades to centuries.  But ice volume in the Arctic has shrunk noticeably in recent years, as I wrote about here.  So ice areal extent can have very similar values as years past and no problem seems to exist.  But ice volume decreasing is more worrisome.  It indicates that recent weather patterns in consecutive years has changed from past patterns.

I will also mention that the recent areal anomalies have reached ~3 million sq. km. in the past two years as minima.  That’s a big deviation from the long-term mean.  And in fact, the recent record refreezing of Arctic sea ice would not have been possible if it weren’t for the excessively low areal extent at the end of the boreal summer.  Far from allaying my concerns, that refreezing is indicative of a shifting system from one stable oscillation to something that can’t be fully characterized yet.

Taken together with other results, which I will get into in other posts, the state of global sea ice seems to me to be on a precipice.  The Arctic appears to be entering a different climatological regime.  Parts of the Antarctic appear to be doing the same.  I don’t think enough concern is present in the public’s mind.


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s