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siili

In the curious things happening at the (previous) north pole department, is it the foggy lens plaing tricks with me or have the big yellow thingy taken a plunge?

Artful Dodger

Do we have any Aussie readers with us? Today, the Arctic Sea Ice extent is now smaller than the land area of Australia (7,692,024 sq.km). Remarkably, this is almost exactly half of the sea ice extent on March 31, 2010 (14,407,344 sq.km).

FrankD

At least one, Dodger. I'm poring over satellite pix of the NWP to distract me from Canberra's current frostiness. I've noticed that each year:
1: winters get milder
2: I feel the cold more.
thus maintaining a perfect balance of discomfort....

Smaller than Australia? 'Struth, that small? ;-)

Artful Dodger

FrankD: Bloody oath, mate. It's small enough to ride a bicycle around it in 7 weeks! Cheers ;^)

Kevin McKinney

The buoy seems to be there. . .

Phil263

Hi FrankD mate, I am another oz from the Gold Coast in Queensland. It's pretty chilly in the mornings up here, about as cold as it would be in Scotland at this time of year...

Neven. great site with balanced opinions. I am really enjoying it !

Phil263

Hi FrankD mate, I am another oz from the Gold Coast in Queensland. It's pretty chilly in the mornings up here, about as cold as it would be in Scotland at this time of year...

Neven. great site with balanced opinions. I am really enjoying it !

S2

"It's pretty chilly in the mornings up here, about as cold as it would be in Scotland at this time of year..."

You can easily tell the local kids from the tourist ones on the beach up here (just shy of 58ºN) in July & August. The locals wear wetsuits.

Watts & his pals were recently crowing about how many people were wearing woolies and coats during the British Open a couple of days ago. I guess that none of them have been to St. Andrews in July. :)


Anu

What exactly does the PIOMAS model say about 2010 ?

It said the sea ice volume for 2009, September was 5,800 km^3
http://psc.apl.washington.edu/ArcticSeaiceVolume/IceVolume.php
The PIOMAS anomaly in 2009, September was about -7.5 from the 1979-2009 average. So, the "average" for September is 13,300 km^3

See how the anomaly for 2009 bounced around -7.5 for the whole melt season ? This melt season, it seems to be bouncing around -11. If it stays at 11, then starting from 13,300, this anomaly of 11 gives: 2,300 km^3 !!!

That's just 40% of the ice volume of last year.

http://nsidc.org/news/press/20091005_minimumpr.html
Figure 1. Arctic sea ice extent for September 2009 was 5.36 million square kilometers (2.07 million square miles), the third-lowest in the satellite record.

But what was the average area ?
Volume is area times thickness, whereas extent is just an easier measure of difficult satellite images:
http://www.ijis.iarc.uaf.edu/seaice/extent/AMSRE_Sea_Ice_Area.png
Eyeballing the charts, the average for September 2009 looks like 4.7 million sq km, so I'll say 4.8 to be conservative.

4.8 million sq km * 1 meter = 4,800 km^3, so 5,800 km^3 --> 1.2 meters thick

If 2010 has the same sea ice area in September, that means the ice average thickness will be 0.48 meters vs. 1.2 meters last year.
Most likely, it will be some combination of less area and less thickness than 4.8 million sq km and 1.2 meters. Soon enough, CryoSat-2 will tell us how accurate the PIOMAS model has been this year.

Neven

Cryosat-2 will be a blessing, but this melting season should also tell us something about the PIOMAS model. If the ice really is so much thinner I cannot imagine it to remain spread out until the end of the season and make for a high extent/area like Goddard or the NSIDC team are predicting, ie 5.5 million square km. Not even if these adverse weather conditions remain unchanged till the end.

In fact, when I look at MODIS images and see the state of ice, the rottenness of it along the Siberian coast, the breaking up of all landfast ice in the Canadian Archipelago, the huge hole in the Beaufort Sea and the Emmentaler-like appearance of parts of the interior of the ice pack, I would almost wish for conditions to stay like this for a while longer to see if it can get even worse and the ice, like Wayne Davidson says, all of a sudden starts disappearing in situ, like it did in Hudson Bay. Extent dropping without compaction, if you know what I mean.

But I'd rather see atmospheric conditions reverse back to ice melting mode before the end of the month. If the ice is then still able to maintain an extent above 5 million, this would be evidence that the PIOMAS projection is off.

It will be interesting either way and hopefully Cryosat takes away all further doubt. It will save everybody a lot of time.

Jon Torrance

I can't help wondering whether it's plausible at some point for the ice to get so thin that virtually the whole Arctic Basin ice pack simply breaks into fragments under the action of wind and wave. At which point, I suppose it would depend on the weather whether the fragments would keep swirling around in the Arctic Ocean or whether huge amounts of ice would head elsewhere.

On reflection, I suppose that has to be plausible. I just have no idea how thin the ice has to get before it's likely nor, even if I knew that, how close we might be to that point (I'm sure the PIOMAS people are doing the best they can but they're only human - they could be wrong). It does make me wonder if someday we're going to see a really large late summer extent at the same time as a really small area, i.e. a crash in average concentration as the ice pack loses integrity.

siili

Models are easy to get lost in and forget about the difficult reality, but it should give some hints about the connection to compare different modern ones, like PIOMAS and TOPAZ, with things like age-tracking graphs and the temporal change in real radar and visual observations.

If you compare the thickness distribution in the TOPAZ model, which has a daily archive like the pips2 one although only going back to 2008, the loss of the thick ice close to the canadian side is almost complete, and even the divergence center close to the pole looks ok, but then the problems start to appear. Looking at the age-tracking maps and from the slow melt this old ice advected away by the gyre is not along the coast where the model indicates thin ice. Also a common problems to all three models appears to be the very thick ice in the east siberian sea.

So one question then is if something new is happening this year which is hard to track for the models, maybe conected to the thin and rotten state of the ice?

Only time and hopefully cryosat-2 will tell.

Kevin McKinney

It looks to me like a bit of a crash in concentrations now--albeit not as drastic as that envisioned by Jon.

In support of that notion, I'd point to all the points Neven made. This season is just *different.*

Artful Dodger

Jon Torrance July 22, 2010 at 22:42 | "it's plausible at some point for the ice to get so thin that virtually the whole Arctic Basin ice pack simply breaks into fragments under the action of wind and wave"

The "open patches" of ice pack should get a good integrity test from July 24 to July 29 as a large Low pressure system transits the Pole, starting from the Chukchi sea.

In the Beaufort sea, winds at 156W-77N are predicted to peak at 18 kts on July 25 at 15:00 UTC. In the Central Basin, winds at 180W-85N will vary betwen 10-16 kts from July 26-29.

Any interested "Met" watcher can reproduce this forecast and create animations with the free Windows application "UGRIB"

http://www.grib.us/Downloads/tabid/56/Default.aspx

More about GRIB files for weather forecasting from Wikipaedia

Neven

Thanks for linking to that software, Artful Dodger. I've played around with it a bit, but what I'm missing is that spherical Northern Hemisphere view with the North Pole in the middle. I can visualize pretty well, but I'm lazy, you know.

Besides, I have become used to checking the Wetterzentrale model forecasts (was it you who pointed it to me a while back?). I prefer the one from ECMWF beause it has these nice T's (tief=low) and H's (hoch=high) all over it., with pressure levels on the isobars that allow me to judge how low or high a pressure area is.

If I may ask a silly question: there's a colour bar on the right side of the ECMWF map that ranges from 478 to 600. What unit does that represent?

Artful Dodger

Neven said: there's a colour bar on the right side of the ECMWF map that ranges from 478 to 600. What unit does that represent?

Meine Sprachkenntnisse sind Deutsch, Bier und Schnitzel begrenzt, aber man könnte versuchen, Google Translation, ob das hilft.

But if I was forced to guess, I'd say Sea Level Pressure (SLP), in hectopascals (hPA). 478 hPa = 6.93 PSI (about the ambient pressure at 5900 m, or 19400 ft, which is the altitude of the storm track IIRC my Met. training).

http://www.csgnetwork.com/pressurealtcalc.html

Neven

Thanks, but what about the numbers on the isobars, like 1005 and 1020. This is supposed to be millibars, yes? And isn't millibar equal to hPa in numbers?

Do those number perhaps have something to do with geopotential height? That's where looking up 'gpdm' on the German Wikipedia led me.

A plot of geopotential height for a single pressure level shows the troughs and ridges, Highs and Lows, which are typically seen on upper air charts. The geopotential thickness between pressure levels — difference of the 850 hPa and 1000 hPa geopotential heights for example — is proportional to mean virtual temperature in that layer. Geopotential height contours can be used to calculate the geostrophic wind, which is faster where the contours are more closely spaced and tangential to the geopotential height contours.

Oh man, I hate it that I'm not getting this! Brings back all the traumas of not understanding basic physics and chemistry in high school. Couldn't be bothered at the time. Now regrets.

Artful Dodger

Neven said: "but what about..." Yeah, I know. I'm looking for a GRIB -> kml export utility so I can view winds as a Google Earth layer...

Kevin McKinney

". . . Bier und Schnitzel begrenzet. . ."

Hey, a guy's got to have his priorities straight.

And "virtual temperature" is explained here:

http://en.wikipedia.org/wiki/Virtual_temperature

Kind of a normalizing convention, I guess.

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