ASI 2015 update 7: to compact or not to compact

During the melting season I'm writing (bi-)weekly updates on the current situation with regards to Arctic sea ice (ASI). Central to these updates are the daily Cryosphere Today sea ice area (SIA) and IJIS sea ice extent (SIE) numbers, which I compare to data from the 2005-2014 period (NSIDC has a good explanation of sea ice extent and area in their FAQ). I also look at other things like regional sea ice area, compactness, temperature and weather forecasts, anything of particular interest.

The animation on the right consists of NSIDC
sea ice concentration maps, one for each ASI update.

Check out the Arctic Sea Ice Graphs website (ASIG)
for daily updated graphs, maps, live webcam images and
the Arctic Sea Ice Forum (ASIF) for detailed discussions.

September 1st 2015

Look at the sea ice concentration animation at the top right. Notice how the final frame suddenly is whiter than the preceding frame? That's a sign that we have entered the final phase of the melting season, when temperatures drop and melt ponds within the ice pack freeze over again. Sea ice concentration goes up, and the NSIDC SIC map becomes whiter.

But the Pacific side of the Arctic is still bluish. During the past two weeks the disintegration of that part of the ice pack has continued, spurred on by a late cyclone that further stressed the region (see special blog post on the matter) and increased the area that consists of a mix of ice floes and open water. The compaction potential of this region will probably decide where this melting season will end up on the various sea ice area and extent graphs.

And this end result still holds interest, because - somewhat surprisingly - the 2015 melting season could still achieve a top 3 minimum. Surprising, because the melting season started out with more volume, more multi-year ice, saw little and late preconditioning during May and June, and - despite a killer July - there has been relatively little transport and compaction this year.

With melting momentum mostly out of the picture now, it all comes down to compaction.

Sea ice area (SIA)

Here's the latest Cryosphere Today SIA chart, to which I've added preliminary data as calculated by Wipneus:

Given some heavy losses extent-wise in the past week (see below), I had expected CT SIA to follow suit, but nothing really happened after the uptick due to melt pond refreezing, escept for one daily drop of 85K. Nevertheless, the 2015 trend line is still in 6th position and close to other years. Theoretically it could still end up 3rd, but it doesn't look likely. The 2013 and 2014 daily minimums have already been surpassed, with at least one more week of decrease left to go.

Sea ice extent (SIE)

Sea ice extent based on data from the Japanese Arctic Data archive System website, paints a different picture:

Due to some very large drops last week (including two very late century breaks), 2015 is now battling it out with 2007 and 2011. Best of the rest, after the record smashing 2012 melting season, is a distinct possibility. Needless to say, the 2013 and 2014 daily minimums have already been overtaken by a large margin.

Cryosphere Today area per IJIS extent (CAPIE)

With sea ice extent fiercely dropping and sea ice area fiercely stalling, the CAPIE graph is showing something truly spectacular:

CAPIE is a compactness measure. It gives an idea of how compact the ice pack is. Melt ponds and dispersed ice floes give the ice pack a less compact appearance. Because these melt ponds and the open water between dispersed floes get counted for sea ice area, but not for sea ice extent (there needs to be less than 15% of ice in a grid, or else the entire grid area gets counted as 100% ice covered), you get an idea of compactness by dividing area numbers with extent numbers.

CAPIE was really low up until two weeks ago, but things have drastically reversed, a combination of melt pond refreezing, and ice floes on that Pacific side of the ice pack perhaps so far apart that the open water is now getting counted for extent as well. Either way, the 2015 trend line has been shooting through the roof, going from one of the lowest to one of the highest percentages in the 2006-2015 record. Wipneus' compactness graphs (more consistent and better resolution) show the exact same thing.

Regional SIE and SIA

The same Wipneus has yet again sent me several of his home-made sea ice concentration maps, using the highest resolution AMSR-2 data (3.125 km grid) provided by the University of Hamburg.

Here's the first, showing how things have changed in the past two weeks on that Pacific side (red = less ice than two weeks ago, blue = more ice than two weeks ago):

Massive losses in the past fortnight, right where a lot of multi-year was situated. Again, read the special blog post that has more details on what has been happening here this year.

The second image shows the situation in the Canadian Arctic Archipelago:

Heavy losses there too in the past two weeks, but it seems the Northwest Passage's main route still hasn't entirely cleared, with wisps of sea ice from McClintock Channel still lingering and being pushed out into Viscount Melville Sound. The western entrance is also still more or less blocked by ice in the Beaufort Sea. This animation of satellite images shows how the ice moved in the last three days:

We have to wait and see whether the Northwest Passage will be completely open. Still, a lot of ice has disappeared from the CAA this year (perhaps even more than in 2012), another zone where ice should be oldest and thickest:

Finally, another Wipneus comparison map, showing the level of compaction (and probably some bottom melting too, as the ice probably isn't very thick there, despite seeing good weather for ice retention all melting season) on the Siberian-Atlantic side of the Arctic in the past two weeks:

It remains to be seen how much more compaction can take place here. As commenter and fellow Arctic blogger Diablobanquisa points out on the Forum, it seems refreezing at the edges is already taking place.

Weather conditions

And now for the weather...

This animation of Danish Meteorological Institute SLP images shows events in the past two weeks:

 

The big high pressure area that was announced in the previous ASI update, came into existence and dominated the Arctic until that cyclone showed up, sliding in via Bering Strait. Both mainly caused dispersal instead of compaction and transport. How low this melting season ends up and when the minimum will be reached, now depends almost entirely on compaction.

As I wrote back in 2010, at the end of the first melting season that was covered here on the ASIB, in this blog post dedicated to the influence of atmospheric pressure on the final outcome:

The Beaufort Gyre, the clockwise movement of the ice pack from the Pacific side of the Arctic towards the Atlantic side, is dependent on a high over the Beaufort Sea. Combined with a low over the Siberian coast, preferably between the Kara and Laptev Seas, the Transpolar Drift Stream is activated and transports a lot of ice through Fram Strait. The stable positioning of these two poles opposite each other is known as the Arctic Dipole Anomaly.

This is what you get when that happens:

 

The sea ice gets compacted towards the coasts of Greenland, Ellesmere Island and the rest of the Canadian Archipelago, and it gets transported towards Fram Strait where it melts out in warmer southern waters. A double whammy, as the American expression goes.

Let's see what the ECMWF weather forecast model has in store for the coming 6 days (click for a larger version, and go to the ASIG Forecasts page for daily forecasts):

This set-up looks like it could cause a lot of compaction on the Pacific side of the Arctic, especially after a couple of days when strong winds are forecast. However, on the other side, this will also entail transport of the ice pack towards the Atlantic Ocean, causing dispersal. Sea surface temperatures are high over there, but at this point in the melting season I'm not sure how much ice can still be melted. Still, without compaction not much will happen, and this might just be enough to push 2015 really low on extent and area graphs. Don't expect any spectacularly big drops, though.

On the DMI 80N temperature graph we're not seeing any spikes or anomalously warm temperatures yet, a sign that the water is releasing its heat so that it can refreeze. On the contrary, it's dipping below the average (not Arctic-wide, but above 80°, in the heart of the ice pack):

These freezing temperatures are going to stay confined to the ice pack proper the coming week, as shown on these temperature maps forecast by the GFS model, provided by Climate Reanalyzer (on the ASIG Forecasts page you can view the anomaly graphs, and see that the Arctic will stay anomalously 'warm'):

Of course, it's not just surface air temperatures that are anomalously 'warm', the same goes for sea surface temperatures, as visible on the latest DMI SST anomaly map:

Practically all of the ice pack is surrounded by relatively warm waters, which still should make for some bottom melt. Unfortunately I don't have images for 2012 and 2014 at the start of September, but this configuration is clearly running a lot hotter than in 2013:

Conclusion

As said, the final shape of the ice pack and thus the minimum depend entirely on how much compaction can be conjured by weather conditions. If the winds blow the right way, 2015 could still achieve a draw with previous record years like 2007 and 2011. If they don't, things will probably end up at the 2008 or 2010 level.

But 100K more or less, 2nd position or 5th position, doesn't matter really all that much when it comes to drawing conclusions about what this melting season constitutes for the bigger picture. The fact is that this melting season will have managed to end up remarkably low given conditions preceding and during the first half of the melting season. A lot of multi-year ice has been melted, the volume rebound has been reversed and both passages are (as good as) open.

What we learn from this, is that a lack of preconditioning can still be offset by a warm July and a stormy August, although it makes new records nigh impossible, given the high bar 2012 has set. One can imagine what happens when preconditioning is (above) average followed by some freak weather, especially if the Arctic sea ice pack doesn't get the time and space to recover. 

Enjoy the Arctic sea ice, it's the only Arctic sea ice you've got.

Comments

[Neven]

Due to circumstances I'm going to be off-line for a week, but I expect to be back around the time the minimum hits.

[D]

The CFSv2 model predicts a very warm winter in Canada this year so that the areas that melted out this summer will build back less ice than normal this winter. This years huge loss on the Canadian side followed by a very warm winter will set the table for a record minimum next summer or the year after as much warmer water than normal that's building in the north Atlantic pushes into the Arctic ocean.

The long range models do show strong high pressure over the Pacific side of the Arctic ocean so there is some chance of ice recovery on that side, but it may be offset by the massive amount of heat coming off the Pacific from the huge El Nino.

Yes, in the big picture first, second or third place means nothing. The long term trend of sea ice loss is continuing. The short term recovery that followed the record melt of 2012 is over.

[Jim Hunt]

JAXA extent for September 1st is below 2007, and hence now in second place behind 2012. My own musings on the 2015 minimum:

http://GreatWhiteCon.info/2015/09/the-2015-arctic-sea-ice-minimum-extent/

incorporating the latest GWC video, in this case of the Arctic basin as a whole:

http://youtu.be/DK7a4IknvVU

There is a large potential fetch across the East Siberian, Chukchi and Beaufort Seas should any further cyclones occur in the area over the next few weeks.

[There is also] a 1000 hPa central pressure low spinning over the Laptev Sea. It’s currently not very deep, and it’s not over the East Siberian Sea either, but watch that space.

[Bill Fothergill]

"JAXA extent for September 1st is below 2007, and hence now in second place behind 2012"

Yep, and it looks as if it will stay that way for at least the next couple of days at least, as the JAXA figure for 4th Sept 2007 is only about 45k below 1st Sept 2015.

The Bremen chart has also been showing 2015 below 2007 for the last couple of days.

So, Jim, how is your bosom buddy Steve/Tony coping with this latest "return to the 90's"?

[John Christensen]

Sorry for the slightly OT remark, but found this hilarious article:

http://www.theguardian.com/us-news/2015/sep/01/us-icebreakers-arctic-sea-traffic

Obama says:
“The Arctic is at the leading edge of climate change, a leading indicator of what the entire planet faces,” Obama said. “Climate change is no longer some far-off problem. Climate change is already disrupting our agriculture and ecosystems, our water and food supplies, our energy and infrastructure.”

And the Alaska GOP senator Lisa Murkowski adds:
“Today’s series of Arctic initiatives announced by the White House - especially with regards to addressing our lackluster icebreaker fleet - is a step forward. The highways of the Arctic are paved by icebreakers,” Sullivan said. “Right now the Russians have superhighways and we have dirt roads with potholes."

Amazing how the message of climate change can be combined with turning it into a highway supported by heavy icebreakers..

[John Christensen]

It was evidently Dan Sullivan's (The other Alaska GOP senator) comment, and not Lisa Murkowski..

[P-maker]

John,

"hilarious" may not be the right word here.

I would rather call it a tragedy, that by the time these ice-breakers will come afloat, the ice may have gone, and they will be better suited for ploughing through the dead bodies in the Mediterranean - see http://edition.cnn.com/2015/08/27/africa/migrant-bodies-wash-up-in-libya/ ...

[Sam]

The entire ice sheet is rotating counter clockwise westward just above Canada at a rate of 17 km per day. Stunning.

[Jim Hunt]

Hi Bill,

"Steve"/Tony has been studiously ignoring me, whilst his many merry minions have been calling me a number of nasty names. He's also been opining that this very blog conveys "mindless BS from the usual Arctic hysterics". Chapter & verse can be found at:

http://GreatWhiteCon.info/2015/08/arctic-sea-ice-approaching-normal/#comment-211659

and/or

http://forum.arctic-sea-ice.net/index.php/topic,1372

[Colorado Bob]

“Sea ice around Greenland acts as a ‘switch,’ causing that region to respond more quickly than the rest of the planet does by insulating the air from heat stored in the deep ocean,” said Yuko Okumura, a UTIG research associate and a co-author on the study.

Ancient Cold Period Could Provide Clues About Future Climate Change

AUSTIN, Texas — Researchers at The University of Texas at Austin have found that a well-known period of abrupt climate change 12,000 years ago occurred rapidly in northern latitudes but much more gradually in equatorial regions, a discovery that could prove important for understanding and responding to future climate change.

The research, published Sept. 2 in Nature Communications, focuses on the Younger Dryas, a cooling period that started when the North Atlantic Current, an ocean current, stopped circulating. The event caused Earth’s northern hemisphere to enter into a deep chill, with temperatures in Greenland dropping by approximately 18 degrees Fahrenheit in less than a decade.

http://news.utexas.edu/2015/09/02/ancient-cold-period-could-provide-clues-on-climate-change

[Bill Fothergill]

Interesting article Bob.

The fact that the consequences of climate change can quickly appear at high latitudes is pretty much a no-brainer, thanks to the feedbacks that give rise to what has become known as Arctic Amplification.

However, I had no idea about the longevity of downstream effects at lower latitudes. Recovery from such "disturbances" would appear to display a hysteresis that would be well-nigh impossible to predict just by sitting on one's backside and prognosticating.

You just can't beat some good empirical data. (Yep, I see the tautology in that sentence.)

As I'm sure most people on this site already know, the Younger Dryas is thought by many to have been caused, at least in part, by the partial drainage of Lake Agassiz. A later partial drainage has also been linked to the 8.2 ky event.

[Colorado Bob]

Bill Fothergill -

The Younger Dryas has always been of interest to me. There are several sites in North America where huge deposits of blow sand are the finger print of it. One at Lubbock , Texas is over 2 meters thick.

[Bill Fothergill]

@ Jim H
"... his many merry minions have been calling me a number of nasty names ..."

Another audaciously awesome alliterative attempt?

Here's a little crumb of cold comfort you can toss their way from the Cryosphere Today Arctic SIA database...

QUESTION: What was the total number of days - prior to the year 2000 - on which the daily value for area was at least 500k sq kms lower than the 30 year average for the day?

ANS: 242

QUESTION: How many days has that happened thus far (i.e. as at day 244) during 2015?

ANS: 244

Yep, to quote "Steve"/Tony "... The Arctic is making a rapid return to the state it was in during the 1990s... "

Perhaps the poor thing is getting confused by the fact that 242 and 244 are quite similar numbers? As his article was posted about a week ago, the CT database would only have been up to about Day 238 at the time, and therefore one could argue that it was approaching 242.

NB Spoiler: Out of the 242, 3 happened in 1984, 11 in 1989 and the rest in the 90's.

[Jim Hunt]

Bill, Tony et al.

NSIDC (daily) extent has dropped below 2007 also. Meanwhile The latest edition of Arctic Sea Ice News has just been published:

http://nsidc.org/arcticseaicenews/2015/09/steady-decline-summer-minimum-approaching/

The NSIDC say:

[Our] forecast places the upcoming daily sea ice minimum between third and fourth lowest, with fourth more likely. There is still a possibility that 2015 extent will be lower than 4.3 million square kilometers, the third lowest sea ice extent, surpassing the 2011 sea ice extent minimum, and a small chance of surpassing 2007, resulting in the second-lowest daily minimum.

[AbbottisGone]

OK, Bill, I am meditating on those numbers as we speak.

I am thinking: there is some natural downward variation of course but those numbers do seem 'steep'. (...does a bit more hand waving/ chin scratching)

I've always wanted to ask, but didn't know where: can a time series of 'r' values help the science decide?

--> wrt what I'm not exactly sure but just the concept of a time series of 'r' values has played with me lateley as ultra-cool! (No, I don't really know what an 'r' value is but I am under the impression it's important).

cheers!

We could see if the science is tightening up sort of thing, ya know!??!

THE ONLY other thing that is really bugging me lately is The Guardian seems to be reporting that there is no money for Glacier Research ( http://www.theguardian.com/environment/2015/sep/01/the-shrinking-glaciers-of-austria ).

Am I the only one that finds this a bit weird given the funny rates of change we are seeing in other indicators and the seemingly conflicting narrative that Glaciology is a superior indicator of climate change as compared to sea ice for example!??!

[Bill Fothergill]

@ AiG "... but those numbers do seem 'steep' ..."

OK, let's see if I can explain why that "steepness" is exactly what one would expect.

The easiest way to start is perhaps to consider the hypothetical case of some unspecified "thing" that is monotonically reducing in size at a constant rate. Let's say that between 1981 and 2010, the average value of the "thing" was 10 million units, and that it is dropping at a steady 50,000 units each year, or just under 140 units every day.

Let's now switch to anomalies, rather than absolute values: given that the baseline is the 1981-2010 average, then every measurement of the "thing" prior to about 31st Dec 1995/Jan 1st 1996 would have a positive anomaly, and every subsequent measurement would be in negative territory.

However, if we restrict our interest to anomalies that are at least 500,000 units below the mean, then, at a drop rate of 50,000 per annum, we would need to wait until Dec 2005/Jan 2006. Until then, we would not see any (negative) anomalies greater than half a million, but from then onwards, every measurement would exceed this threshold.

That is the simple, hypothetical case - although the numbers might sound vaguely familiar - but now let's look at reality. There are many types of variable at play when thinking about Arctic Sea Ice, and these can vary in magnitude and timing. However, let's concentrate on 3 distinct classes...

1) Seasonality: As we* live on a planet with pronounced axial tilt, or obliquity, seasons come and go on a 12 monthly cycle. This produces the biggest "change signal" amplitude. For example, using the 30 year average for sea ice area on the CT database, the max - min range is about 14.1 to 4.7 million square kilometres. (*Well, some of us do, but we get the occasional visitor from elsewhere.)

2) Chaotic: Superimposed upon the seasonal cycle, there is a chaotic signal that ranges in its time effects from days to years. This signal is about one order of magnitude less than the seasonal signal, but can still easily represent variations comfortably in excess of 1 million sq kms from one date to the same date the following year. Most of us simply call this "weather".

3) Climactic: On a year-to-year basis, this is easily the smallest signal, as it is yet another order of magnitude down on even the chaotic signal. I happen to have the NSIDC figures to hand, and the climactic trend figure for SIA is only about -51k sq kms/annum. Owing to the fact that it is so much smaller than the other perturbations mentioned, it takes time - typically decades - for such a signal to unambiguously emerge from the background noise. (NB Just to make it more complex, this climactic variation also exhibits a degree of seasonality.)

Because of the noise, you do not get a "clean" transition from one state to another: instead, although still pronounced, the transition is smeared over a few years.

As I said earlier, CT had 242 instances of a daily anomaly <-0.5 million sq kms in the entire 1979-1999 period. The next 15 years were as follows...

2000 (36)
2001 (44)
2002 (113)
2003 (135)
2004 (106)
2005 (295)
2006 (353)
2007 (365)
2008 (260)
2009 (265)
2010 (310)
2011 (365)
2012 (294)
2013 (282)
2014 (355)

From 2005-2014, the average was 314/annum, and it will continue to rise. The reason why the relatively small Climactic signal gradually rises out of the noise is that it is cumulative, rather than cyclic or chaotic.

You can see the effect graphically by looking at this CT chart...
http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/seaice.anomaly.arctic.png

I hope that helps explain why the dataset is so back-loaded when looking at anomalies.

cheers billf

[AbbottisGone]

Very Interesting, cheers. We all like numbers and this gives me much food for thought.

[AbbottisGone]

Flippantly I could say it appears nothing grows(or shrinks as the case may be) exponentially but I say that with a little more than a bit of hopefully not chargrined panic.

[AbbottisGone]

*ahem, back to the point!

You say that we expected the steepness of these numbers..

I found what you wrote more than interesting(and informative) but why did we expect these sorts of numbers?

[Bambara]

"From 2005-2014, the average was 314/annum, and it will continue to rise."

Well it can't continue to rise too much more, 314 is getting close to 365 and by definition it can't be higher than every day.

[Kris]

Bambara wrote:

to 365 and by definition it can't be higher than every day.

Quite right. And after all, to me it looks more like a rather valueless statistic only good to please deniers.

Meanwhile ADS-JAXA shows an uptick two days in a row. [+ 20.000 square km and 'only' + 300 square km].

Thus, albeit the remains of "the arm" are bound to melt out, it's about sure this year will be the 3th or 4th lowest, with the 4th rank as the most probable.
And let me remind you that it is fare worse as it looks like, as this year has been a disastrous one for the multi-year and thick ice.

Incidentally, to day at Tiksi a horrendous temperature of 18 ºC, so it ain't finishd yet.

[Voyageur]

Bill F.,
From a lurker who mostly learns and is grateful to many of the regular posters here, ... a rare interjection to say: your post on the three classes of variables was a most useful and enlightening explanation. Many thanks,
Paul

[Bill Fothergill]

@ Bambara "Well it can't continue to rise too much more, 314 is getting close to 365 and by definition it can't be higher than every day"

Yep, I am aware of the number of days in a year. The point was that it is becoming a rarity to see daily CT values that are within half a million sq kms of the long term average, and that such an event is becoming increasingly rare.

The progression continues (albeit with an obvious lag) at higher anomaly values. Over the 2005 - 2014 period, CT averaged...

<-0.75 million sq kms on 238 days/annum
<-1.0 million sq kms on 157 days/annum
<-1.25 million sq kms on 80 days/annum

All these numbers will increase as the Arctic progresses to a "new normal".

@ Kris "And after all, to me it looks more like a rather valueless statistic only good to please deniers"

You are certainly welcome to your own opinion, but I'm at a loss as to how you figure this is "only good to please deniers".

If you were to look further up the thread to Sept 3, you will see that is where the subject was first broached. This was done during a bit of friendly banter between Jim Hunt and myself regarding a certain well-known denier.

The reason I expanded on the "metric" was that I was asked to by AbbottisGone.

@ Voyageur

Thanks Paul, you're very welcome.

[AbbottisGone]

Kris, how do we best look at the evolving story on multi-year ice?

There were graphs saying that multi-year ice had made a come back recently,... and now that has died off you are saying!

These graphs on multi-year ice seem to not be constantly updated,... or do I just not know where to look?

[AbbottisGone]

Finally, what is a better indicator: a time-series on Multi-year-Ice or Glacier volumes?

[Kris]

AbbottisGone wrote:

... or do I just not know where to look?

Apparently, as our Neven himself already wrote quite a few comments about that matter this very year.

And other than this blog, just compare the Dansk DMI and Uni-Bremen charts from March-April to these of July-August-September.

And although it isn't mandatory at all, you always could have a start here at the 1st of the month parade.

And to sum up, early last winter about 50 % of the multi-year ice had been shifted to the Beaufort- and Chukchi Sea. All of that transport has vanished now.
The remaining 50 % at the Greenland and Canadian Archipelago coasts has been divided in half, more as a half actually.

On top of that, virtally all of that remaining MY ice has been broken into countless ice shelves.

All of these factors together lead to my conclusion it never has been as bad as this year, not even 2012.

Incidentally, today [=yesterday] again an uptick noted at ADS-JAXA, so that's 3 days in a row an uptick now.

[AbbottisGone]

Cheers for the links Kris,

So 'concentration' is multi-year ice? This is what's confusing me.

[Jim Hunt]

Kris - JAXA extent has resumed a modest downtrend, with a drop of 24,374 km2 yesterday:

http://GreatWhiteCon.info/2015/09/the-2015-arctic-sea-ice-minimum-extent/#comment-211819

AIG - It seems you're still confused about concentration? Here's the NSIDC FAQ on "terminology":

https://nsidc.org/cryosphere/seaice/data/terminology.html

[AbbottisGone]

Ok, thanks. So concentration is not multi-year ice. I was getting confused because people seemed to be talking about multi-year ice and then referencing concentration statistics/maps.

Do people use concentration as a proxy for multi-year ice because multi-year ice statistics don't seem to be updated that often... or am I once again making a wrong guess?

(I could suppose it may inform on multi-year ice in an indirect manner ... I suppose concentration is a useful statistic somehow...)

[NeilT]

AIG,

Concentration is nothing more than the ratio of ice to open water. Any ice. Even 1" thick ice counts to concentration.

I think if you look back people will have been referencing concentration in areas where it is already known that there is multi year ice.

I.e. the more area of ice in a place which is MYI, means there is likely to be more MYI.

Conversely if an area mapped to have MYI suddenly loses concentration, then it's a good bet that a lot of MYI has melted. Or blown away.

That's the only relationship I can see. Concentration is not used as a "proxy" for ice age at all.

As far as I know there are 5 ways in which MYI is mapped.

Bore holes
Aircraft direct radar depth measurement
Submarine sonar soundings
Ice Freeboard measured by Satellite
Radar Backscatter measured by Satellite, where the different ages of ice give different signatures.

There is one other measurement but it's so general as to not really be helpful with the ice pack and that's the GRACE satellites. Which are more helpful with Greenland and Antarctica. As this image shows..

http://www.nasa.gov/mission_pages/Grace/multimedia/chart20121129.html

[AbbottisGone]

Thanks,.. separate statistics that can be used in concert!

Also, interesting on the methods of detection for multi-year ice.

[Tanada1945]

I was looking at the surface wind forecast for the next week,

http://globalweatherlogistics.com/seaiceforecasting/gfs.1000mb.vectors.arctic.html

What do you make of it? The lines seem close together which means high wind speeds, but everything seems very cyclonic in shape. It might always look this way and I didn't notice but I am not sure so I am asking, is the pro or con for the compaction effect?