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.
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.
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
Seke Rob has been treating us with fantastic graphs for many weeks now, and it's high time I picked one out for a highlight. IJIS sea ice extent broke through the 5 million km2 barrier yesterday. This graph shows how many days it has taken to drop from one million to the next from the date of maximum extent onwards (click on the link above for a larger version):
I hope this first attempt at a post works. You probably know me as Gas Glo here though I usually post on the internet as crandles - that wasn't intentional just an effect of choosing to sign in with an existing google group.
Following Larry Hamiltons work on a Gompertz fits, I have submitted a method of updating that as more information about area and volume become available. I have already provided quite a bit of the detail in the posts so please excuse the repetition. Apologies also if you are not into geeky maths stuff.
Anyway enough preamble, here is what my outlook says:
It took a while, but century breaks have started rolling in this month. As you all know (and if you don't, read last year's Century Breaks post) a century break is the name I have given to daily extent decreases as reported by IJIS that surpass 100,000 square km. The name is based on one of the best and toughest sports in the world: Snooker. On the image to the right you see Ronnie 'The Rocket' O'Sullivan, one of the best snooker players of all times. If you want to know why, you can watch the video in this post from last year.
With 4 century breaks so far 2011 is behaving like most recent years, with the exception of 2010, which had already compiled 8 century breaks by the end of June. But it didn't go on to break records as July was a very bad month century break-wise.
Here is everything you need to know about the IJIS century breaks:
Proxy evidence suggests that the recent declines in Arctic sea ice extent and volume are unprecedented over at least the last few thousand years (Polyak et al. 2010). Historical records indicate that the seasonal ice zone, an area of northern seas that is ice covered in winter but not in late summer, has been expanding gradually since 1870, and more rapidly in the past three decades (Kinnard et al. 2008). Reinforcing that conclusion, combined submarine and satellite measurements show that ice has been thinning over much of the Arctic Ocean since the 1950s, so the remaining cover increasingly consists of thinner seasonal ice (Kwok & Rothrock 2009).
These longer-term studies place recent satellite-era change in perspective. Sea ice extent, in particular, has been relatively straightforward to define and measure by satellite. As a result, we have daily time series of extent and area going back into the 1970s, which confirm a recently accelerating decline. Decline has been most noticeable in late summer, but is visible across all times of the year. A cycle plot (Cox 2006) in Figure 1 illustrates changes in average extent and area (NSIDC data) broken down for each month, from November 1978 through March 2011.
Figure 1
Each squiggly line in Figure 1 tracks the mean sea ice extent (blue) or area (orange) for a particular month over roughly the years 1978 to 2011. The vertical axis shows the absolute ice cover in millions of km2. Extent, for example, ranges from values near 16 million km2 in winters of the earlier years, to 5 million km2 or less in summers of recent years.
The declines visible in Figure 1 all are statistically significant. Figure 2 graphs the linear trends separately for each month.
Forecasts, predictions, projections, there are some nuanced distinctions between all these terms. But 'forecasts' alliterates best with 'first', and I'm a sucker for catchy, alliterative titles. Besides, the forecasts for this year's Arctic sea ice extent minimum that I'm going to write about, are meant as stimulating statistical exercises. No more, no less. Let that be a careful caveat.
I'm starting off with a blog post that was written a month ago by Kelly O'Day of the Chartsgraphs blog:
Arctic Sea Ice Extent Forecast for September 2011
In this post, I use a quadratic regression model to forecast the September, 2011 Arctic Sea Ice Extent. The model was developed with 1980 – 2010 data. Links to the R script, source data and how-to article on polynomial regression are provided.
Kelly's forecast - based on a quadratic regression model of September sea ice extent for the 1980 – 2010 period - is that September 2011 SIE will decline 0.36 below 2010 levels, to 4.54 million km^2, with a confidence band of +- 0.59. The forecast was inspired by Tamino‘s post on Arctic Sea Ice decline called 'Death Spiral', that some of us might recall. Tamino's prediction for the 2010 minimum SIE made in July came in very close to the actual number (edit: Tamino made a prediction for the 2011 SIE minimum back in October 2010, see update at the end of this blog post):
Now that the melting season is over it is time to follow up on the Century Breaks post I did in the first few weeks of the blog. Here's an overview of the last 6 years:
Total century breaks:
2005: 14
2006: 8
2007: 20
2008: 12
2009: 14
2010: 11
The score for this year was rather disappointing, as 2010 was leading the other years by a fair margin at the end of June, having scored 8 century breaks already. But here's what happened in July:
Century breaks in July:
2005: 10
2006: 3
2007: 11
2008: 4
2009: 11
2010: 2
And then a last century break on August 1st.
This reflected the disappearance of the Arctic Dipole Anomaly at the beginning of July, bringing low temperatures and clouds to the Arctic which blocked out the Sun while it was at its peak. Atmospheric patterns made the Beaufort Gyre stall and even reverse, practically eliminating all ice transport through Fram Strait. At a certain point, even the ice transport through Nares Strait reversed. I still find it amazing that despite this the 2010 minimum extent came in so low, and was actually artificially high.
So that was the story for century breaks this year. I'll finish the blog post with something amazing and very funny that happened a few days ago at the World Open in Glasgow. After potting a red and a black snooker genius Ronnie O'Sullivan asks the referee what the bonus is for scoring a maximum break of 147 points. If you haven't seen this (and like snooker), watch it and have a laugh:
I'm regularly writing updates on the current sea ice extent (SIE) as reported by IJIS
(a joint effort of the International Arctic Research Center and the
Japan Aerospace Exploration Agency) and compare it to the sea ice
extents in the period 2005-2009. The IJIS graph is favoured by almost
everyone, probably because it looks so nice compared to other graphs
(like the one by Arctic ROOS, the University of Bremen and the Danish Meteorological Institute).
All the years have a nice colour of their own which makes it easy to
eyeball the differences between trends. Most of the betting on minimum
SIE is based on the IJIS data. NSIDC has a good explanation of what sea ice extent is in their FAQ.
September 15th 2010
Let's leave the playground metaphore for a while. Let's leave the seesaws, the swings, the slides and the trampolines. Let's go back to the fat lady. She's singing alright, but who is she and what's the song she's singing?
Sorry, couldn't help myself. Click 'play' and continue reading.
After slowing down a bit the extent decrease turned into an increase of 50K over the past 3 days, but atmospheric patterns are very fickle. Three days of weird weather, winds blowing towards the pole, and some of that compaction potential could be put to work. Despite the freeze-up kicking into gear, we still might see a slightly lower minimum extent. Keep an eye on the updated animations of the western and eastern Arctic.
The current difference between 2010 and the other years is as follows:
2005: -524K(10,313)
2006: -783K (11,473)
2007: +707 (20,234)
2008: +256K (24,632)
2009: -278K (14,096)
Between brackets is the average daily extent decrease for the month
of September until this date. 2010's
average daily extent decrease for September is currently 23,627 square
km per day.
If 2010 loses as much sea ice extent as...
2005 did after this date it will bottom out at 4.79 million square km.
2007 did after this date it will bottom out at 4.96 million square km.
All the other years had of course bottomed out by now.
Cryosphere Today
sea ice area has increased quite a bit and will probably not drop below the 3 million square km mark. It currently stands at 3.128 million square km. The anomaly compared to the 1979-2008 mean is still relatively big though and could increase some more to accentuate the double dip we witnessed this year:
The increases in area combined with the decreases in extent are starting to show on our CAPIE (Cryosphere area per IJIS extent) graph. The 2010 trend line is likely to go up now, showing that there might finally be some real compaction going on. How much is hard to tell as at this point water between ice floes is also freezing up here and there. The CAPIE percentage is currently 62.58%:
One counterintuitive sign that the freeze-up is starting for real is increasing air temperatures. This is because the water has to release its heat to the air before it can start to freeze up. The DMI graph of air temperature north of 80 degrees latitude is showing this first uptick:
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