Weatherdem's Weblog

Bridging climate science, citizens, and policy

State of the Poles – 9/7/10

1 Comment

The state of global polar sea ice at the beginning of September 2010 is once again very poor compared to climatological conditions (1979-2008). The Arctic ice extent is far, far below average for this time of year.  The Antarctic sea ice extent is above average, but not nearly so much as was the case at the beginning of August.  Unfortunately, global sea ice extent has fallen to ~18 million sq. km., something that has happened in only 2 previous Septembers: in 2007 and 2008.  The Northwest Passage and the Northern Sea Route are largely free of ice, allowing the Arctic Ocean to potentially be circumnavigated.

Each month and each year that goes by provides additional proof that the Arctic has entered into a new state; a different state than has existed for 1,000 years or more.  Monthly and yearly weather conditions have varied considerably over the past few years, as one would expect, but the end result has been nearly the same regardless of any specific condition: Arctic sea ice is declining year-over-year.  It is declining at a rate that exceeds scientific estimates from just a few years ago.  Climate change deniers keep prattling on about increasing sea ice, in direct contradiction to the physical realities before them.  I think most of the areas that have sea ice this September will not have sea ice by 2020.  Specific weather or geologic events might delay the year that occurs slightly, but I don’t think it will take too much longer to witness an Arctic Ocean that is essentially ice-free.

Arctic Ice

In August, rapid melting of sea ice that is less than one year old continued.  Additionally, weather conditions developed during August that assaulted multi-year ice.  This ice is thicker and takes more energy to melt.  Just like the past few years, conditions have been sufficient to melt an increasing volume of ice that is longer lived.  If the Arctic’s recent past is any clue, it will become easier in upcoming years to keep melting ice that forms in the previous winter, thus reducing the availability of longer-lived, more stable sea ice.

September 3rd represented a milestone in poor Arctic sea ice conditions.  On Sep. 3rd, Arctic sea ice extent fell below the seasonal minimum for 2009 to claim third lowest value on record, behind 2007 (the record lowest) and 2008.  In the days since, ice extent has continued to fall and is close to challenging 2008 for 2nd lowest, a dubious honor to achieve.  About the only good news is that the rate of melting has been slowing down in recent weeks and the seasonal minimum for 2010 should be reached in the next couple of weeks.  The Arctic Ocean does have quite a bit of energy in the form of heat to release into the atmosphere before sea ice can form again.  The relatively large expanse of dark blue ocean has had a large opportunity to absorb solar radiation again this year.

To give you a better idea of how Arctic ice volume has changed over the satellite record, click the following link, which shows that ice volume has been decreasing for decades, but has really worsened in the past 5 years.  The graph shows how a particular day’s ice volume compares to the climatological record, which in this case extends from 1979-2009. This time series is extremely disturbing.  It is one of the biggest pieces of evidence to support my postulation that the Arctic will be essentially ice free within a decade.  A system like the Arctic Ocean can only take so much forcing year after year before its characteristics fundamentally change.

Antarctic Ice

The state of Antarctic sea ice at the end of August 2010 was actually close to its state at the end of July, though the intervening daily changes were pretty large.  In the middle of August, for instance, Antarctic sea ice extent jumped way up to register a day-of-year maximum in the satellite record.  This situation caused a denier’s heart to flutter, mostly because they don’t understand the difference between weather and climate.  The explanation for the increase that excited this denier, and the almost immediate subsequent decrease in extent was actually due to local weather conditions as a result of the Antarctic Oscillation.  The denier didn’t care one whit what the scientific cause was, of course, nor do they truly care about transparency and honesty.  They only cared that for one brief moment in time, some data seemed to confirm their pre-conceived, biased view on climate change, which is based solely on extremists’ talking points.

Another commenter tried to lecture me on talking about the viability of Antarctic ice because I hadn’t personally measured its thickness.  I suppose the years of measured Antarctic ice can’t provide anybody the opportunity to discuss things like typical ice thickness and its tendency to nearly completely melt every austral summer.  Just like the Arctic, if the Antarctic sea ice were thicker, it wouldn’t melt every year.  Since the vast majority of it melts on a yearly basis, it can’t be that thick.  Little things like basic physical laws govern this behavior, not my attitude or viewpoint or anything else as ridiculous.

#####

Here are my State of the Poles posts from August and July.

You can find the NSIDC’s September report here. The page is dynamic, so if you’re reading this after September 2010, that month’s report will show up first. If that’s the case, you can look for whatever report you’re looking for on the top pull-down tab on the right-hand side of the page.

Arctic Pictures and Graphs

Here is a satellite representation of Arctic sea ice conditions from yesterday:

Compare that with the similar picture from early August:

As you can see, another dramatic change in sea ice conditions occurred between early August and early September. Large regions of 90%+ sea ice concentration has given way to open water (which absorbs heat, instead of reflecting it) and areas of 40%-80% sea ice with melt water on top of it continue to be present, which does much of the same thing.  The seasonal minimum ice extent will look something like the top graphic, considering there isn’t much more time before it occurs.  By the time my next Pole post is written, some areas will look a little better than the September version.  The August graphic is actually useful in another way.  It shows conditions that were just slightly worse than the average conditions observed over the past 30-plus years.  The seasonal minimum used to be a little larger in extent than what that bottom graphic displays.  So you can pretty easily see how the Arctic has changed: this year’s seasonal minimum will be somewhat less than what is shown in the September graphic and the climatological minimum is somewhat more than what is shown in the August graphic.

Here is the time series graph of Arctic sea ice extent with the +/- 2 standard deviations as a light-gray envelope around the climatological average through yesterday. This month’s version, thanks to the NSIDC report, also shows conditions of recent years:

The 2010 extent is challenging record lows and is clearly very far below the 2nd standard deviation area.  I can’t emphasize that second point enough, it seems.  The difference between the Arctic’s deviation from past extremes is much larger than the Antarctic’s deviation from past medians.  That is, the distance between the Arctic’s 2010 line (in blue) and the bottom of the light gray shading is significantly larger than the Antarctic’s 2010 line and the solid gray line (the Antarctic’s time series can be found further down in this post).  What this time series graph tells us is the past handful of years have witnessed a very different kind of sea ice behavior in the Arctic compared to the recent past.  This alternate time series shows that the Arctic’s sea ice area is running a 1.6 million sq. km. deficit compared to climatological conditions.  Today’s extent is sitting at just a hair over 3 million sq. km., when the average is 4.7 million sq. km.  If this year’s value dips below 3 million sq. km., it would only do so for the 2nd time in recorded history; the first was the stunning year of 2007.  This anomaly time series graph shows how different 2010 has been from recent years: ice area has spent a considerable amount of time at around -1.5 million sq. km., much longer than any year so far.  2007 saw a larger deficit, to be sure, and perhaps it spent more cumulative time at or below -1.5 million sq. km., but 2010′s anomaly looks very different from 2009′s or 2008′s, when the area anomaly hovered closer to -0.25 million sq. km. earlier in the calendar year.

The alternative Arctic sea ice extent time series that I recently found shows conditions since 2002, with different years represented by different colored curves. It provides additional context for comparing current conditions against those from the past. One of the striking things that came through was the record-setting extent of ice in early April 2010 (red curve; the largest areal extent occurring at the latest calendar date on record) shifting to the record-setting low extent of ice in June 2010 and maintaining a 2nd lowest extent on record throughout July 2010. We only have another 6-8 weeks to find out where 2010′s final areal extent will land with respect to other recent years.

Antarctic Pictures and Graphs

Here is a satellite representation of Antarctic sea ice conditions from yesterday:

For comparison purposes, here is the similar picture from August:

Here is the time series graph of Antarctic sea ice extent with the +/- 2 standard deviations in light gray and the climatological mean in dark gray through yesterday:

There are some interesting things to note about these graphs.  First, the Antarctic sea ice extent has undergone a very large increase since mid-March.  Typically, it does so anyway, as seen by the mean value in dark gray in the time series graph.  But the extent has stayed above normal, indeed at or above the +2 standard deviation throughout the austral winter season.  As I wrote above, this condition was largely due to the uncharacteristically strong Antarctic Oscillation, which has kept the oceans around Antarctica dark and stormy, allowing for ice to build up horizontally away from the continent.  You can pretty easily tell when that strong Antarctic Oscillation started winding down in the time series graph: around the 2nd week of August.  After that, sea ice extent actually decreased somewhat and then has bounced around the same value.  It is worth noting that the values measured after the Oscillation started returning to a less extreme state remain higher than the climatological mean.  Furthermore, they have remained above the +2 standard deviation envelope also.  That said, the difference between the value measured in the 2nd week of August that was clearly above the deviation envelope isn’t as large or as long-lived as the difference measured in the Arctic.

The Arctic sea ice extent has been very significantly below the average value for a number of years in a row nowThe Antarctic sea ice extent has bounced around the average value during that same time period.  It hasn’t spent anywhere near the same amount of time above or below the mean that the Arctic’s extent has spent below its mean.  It hasn’t been anywhere near as far away from the mean, especially on a regular basis, as the Arctic’s extent has.  The year-after-year Arctic sea ice loss that has been recorded during the past few years (regardless of month of year, which means the signal is very strong indeed) is a result of the warming trend seen in the Arctic over the past 30 years or so. That warmth has accumulated over the Arctic more so than over the Antarctic to date. Without changes to global greenhouse pollution rates, the Antarctic is only biding its time until its land-based ice sheet undergoes its own melt scenario, which will have real-world consequences that its sea ice sheet melt doesn’t.

Cross-posted at SquareState.

About these ads

One thought on “State of the Poles – 9/7/10

  1. Pingback: State of the Poles – 10/4/10 « Weatherdem’s Weblog

Leave a Reply

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

WordPress.com Logo

You are commenting using your WordPress.com 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 )

Google+ photo

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

Connecting to %s

Follow

Get every new post delivered to your Inbox.

Join 290 other followers