Arctic Sea Ice

Freezing in the Dark

As the polar night sweeps down Novaya Zemlya, Arctic sea ice area has been growing by more than 60,000 km² per day. For now, ice area in the Kara and other marginal seas remains anomalously low, but months of freezing lie ahead. Perhaps the freezing will be interesting to watch, like the melting. So far, this fall's freeze-up has paced 2007, while staying just ahead (Figure 1).

 

Figure 1

Figure 2 takes a longer view, comparing the October 21 ice area with previous years. Although 2011 currently shows around 400,000 km² more ice than the lowest year, 2007, it has 400,000 km² less than the third-lowest year, and 700,000 less than the fourth. These recent years marking “the modern area of ice” still stand apart from from 2006 and earlier values.

Figure 2

 

Donations

This post has taken me a bit longer than anticipated, because I really had a hard time picking a suitable island in the South Pacific to be bought with the donations that came in through the tip jar. But then I had a streak of conscience and ahem, realized I don't want to be on an island in the South Pacific with sea level rising and potential freak weather patterns. So here's all the info on money coming in, going out, and what I propose to do with what's left.

I was initially hoping to get enough donations to cover this year's hosting costs for the blog and do the same thing next year, but to my great surprise a lot more came in: 945 USD through ChipIn and a further 50 USD directly through PayPal (of which 30 were Canadian dollars, which is almost the same as USD). A total of 995 dollars. Once more I'd like to express my gratitude to all donators, not only for the amount, but also for the trust conveyed.

As for the costs: PayPal charges a commission, as does Neteller for its virtual credit card (no plastic thingy, and endless paper waste) that I used to pay for the TypePad hosting costs of 149,50 USD. Just this week I upgraded my account at FollowThatPage that is a great tool for monitoring webpages. And I donated 50 USD on behalf of the Arctic Sea Ice blog to Greenman3610 for making a great video of the 2011 sea ice minimum.

October 2011 Open Thread

Unlike last year the Arctic Sea Ice blog isn't going into full hibernation.

We are sleeping with one eye open...

There will be a new open thread at the start of every month to discuss the recent going-ons in the Arctic (ice, SSTs, weather, etc) and interesting news pertaining to it.

For instance, right now there's a lot ado about the big Arctic ozone hole we witnessed last winter/early spring because of a paper by Manney et al. that has just been published in Nature: Unprecedented Arctic ozone loss in 2011.

I remembered reading about this a few months back, but was reminded by this Alfred Wegener Instute press release (in German) that has a very good explanation of why it happened: extreme, prolonged cold in the stratosphere, causing the formation of clouds that allow CFCs to destroy ozone. A strong Polar Vortex kept all that cold in the Arctic, as is mentioned in this BBC article. Dr. Jeff Masters has an excellent Wunderblog post on this that explains exactly what happened and why it's so dangerous.

Some other recent bad news is that the AMSR-E sensor aboard the Aqua satellite has stopped producing data. I'm not sure what the consequences of this will be, but it doesn't look good.

It would be great if we could discuss these and other things here.

NSIDC Arctic sea ice news September 2011

Yesterday the National Snow and Ice Data Center (NSIDC) released its September analysis.

Some interesting tidbits:

The summer sea ice melt season has ended in the Arctic. Arctic sea ice extent reached its low for the year, the second lowest in the satellite record, on September 9. The minimum extent was only slightly above 2007, the record low year, even though weather conditions this year were not as conducive to ice loss as in 2007. Both the Northwest Passage and the Northern Sea Route were open for a period during September.

PIOMAS September 2011 (volume record lower still)

The PIOMAS graphs at the Polar Science Center of the Applied Physics Laboratory at the University of Washington have been updated. It reached an all-time low of 4.4 thousand km3 last month, but went down some more as we can see on Larry Hamilton's stack graph (Larry also wrote a great blog post discussing these numbers):

So the new record minimum volume is 4.0 thousand cubic kilometers.

Here is the current volume as modeled by the folks from the APL/PSC:

And the volume anomaly:

Let me stress that these volume numbers aren't observed data, but are calculated using the Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS, Zhang and Rothrock, 2003). The real numbers probably aren't off by much, and I base this on some snippets of information like the ice thickness measured at the North Pole by the Polarstern crew and buoy information, but we can't know for sure until the CryoSat-2 team starts churning out some well-calibrated numbers and ice thickness maps.

Commenter graphs

As always Wipneus was faster than the speed of light (or neutrinos if you prefer) and updated his graphs. Here is his graph showing all the yearly trend lines in the period 2002-2011:

September 2011 sea ice volume, looking back and ahead

Last spring I proposed Gompertz curves as simple models for thinking about past and future trends in Arctic sea ice extent, area and volume. Extent and area predictions made using these models in April came close to the observed September means:

NSIDC extent — predicted 4.4, observed 4.6

UB extent — predicted 4.6, observed 4.6

NSIDC area — predicted 3.1, observed 3.2

But the April volume prediction, based on what seemed at the time to be a pessimistic model, turns out to have been too high:

PIOMAS volume — predicted 5.2, observed 4.2

As estimated by researchers at the Polar Science Center of the University of Washington, using the PIOMAS model (website, data), the mean volume for September 2011 was only 4.2 thousand km³. Figure 8 shows this result together with a new Gompertz curve, which points toward a September 2012 mean of 4.0 thousand km³. Whereas the earlier model showed volume reaching very low levels (below 2 thousand km³) around 2016, this new version crosses that line one year sooner.

 
Figure 8

September 2011 sea ice extent, looking back

Daily changes in the graphs, maps and numbers assessing sea ice are entertaining to follow. The day-to-day discrepancies between output from different research teams get close scrutiny by those of us on the outside, trying to learn more about what’s happening to the ice. Seen from the step-back view of monthly averages, however, daily disagreements blur into substantial agreement. Figure 4 illustrates by plotting time series of September means for five main indices produced by the National Snow and Ice Data Center (NSIDC: website, data), the University of Bremen’s Institute of Environmental Physics (Uni Bremen: website, technical paper), IARC-JAXA Information Systems (IJIS: website, data) and the Polar Research Group at the University of Illinois (Cryosphere Today: website, data). So far as I know, Figure 4 is the first graphic to show these five September series together. Disagreements among the indexes appear minor; all five vary together around declining area or extent trends that steepen over the period of observation.

 
Figure 4

September 2011 sea ice extent, looking ahead

The mean extent of Arctic sea ice for September 2011, calculated from the University of Bremen time series (website; technical paper), was 4.6 million km². A Gompertz curve that I estimated last April based on Uni Bremen data for 1972 through 2010 gave a predicted September 2011 mean of ... 4.6 million km². Encouraged by this lucky guess (and that’s what it was!), I here offer an even earlier and more naive prediction for the UB September 2012 mean ... 4.3 million km², with a confidence interval of ±.8 (Figure 1).

Figure 1