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Al Rodger

Talk of jetstreams, Hudson has just published another jetstream paper - (Measurements of the movement of the jet streams at mid-latitudes, in the Northern and Southern Hemispheres, 1979 to 2010 - PDF) showing their pole-ward movement using ozone data. After a very quick skim, I note he gives a figure for the sub-tropical jetstream movements (The tropics have expanded 10 deg of latitude over the period = 40km per year, although Northerners may be relieved to hear that is 2:1 a southerly movement).
Sadly no equivilant figure can be given for the polar jetstreams as the data only extends to 60 deg N&S, although Table 2 quantifies the effect up to 60 deg N&S.

Wipneus
The earth's atmosphere is thinner at the North Pole because of both the colder air mass, and the earth's rotation.

It may be thinner (in km's) but it is denser (in kg/m3, cause it is colder) in the troposphere.
Gravity effect are about 0.5 %, far smaller than the temperature effect.
I think these would make the optical density actually larger from line broadening.
But, as indicated, there are other reasons like water vapor that make the optical density actually smaller.

Artful Dodger

Hi Al,

This topic will be important for Winter 2012/13. Here's a recent paper:

Francis et.al (2009) "Winter Northern Hemisphere weather patterns remember summer Arctic sea-ice extent" (pdf)

From the Abstract:

  • The dramatic decline in Arctic summer sea-ice cover is a compelling indicator of change in the global climate system and has been attributed to a combination of natural and anthropogenic effects.
  • Through its role in regulating the exchange of energy between the ocean and atmosphere, ice loss is anticipated to influence atmospheric circulation and weather patterns.
  • By combining satellite measurements of sea-ice extent and conventional atmospheric observations, we find that varying summer ice conditions are associated with large-scale atmospheric features during the following autumn and winter well beyond the Arctic's boundary.
  • Mechanisms by which the atmosphere "remembers" a reduction in summer ice cover include warming and destabilization of the lower troposphere, increased cloudiness, and slackening of the poleward thickness gradient that weakens the polar jet stream.
  • This ice-atmosphere relationship suggests a potential long-range outlook for weather patterns in the northern hemisphere.

Here's an example of what happens to the atmosphere in high-ice years (red) vs. low-ice years (blue), from Fig. 3:

Figure 3. Poleward gradient in the geometric thickness of the 1000-500 hPa layer [m km1] in (left) the North Atlantic and (right) the North Pacific Oceans during years with above- (red) and below-normal (blue) sea ice during summer. Data extend from September of the extreme ice year to the following March.

Here's the full Citation, with a GRL link:

Francis, J. A., W. Chan, D. J. Leathers, J. R. Miller, and D. E. Veron (2009), Winter Northern Hemisphere weather patterns remember summer Arctic sea‐ice extent, Geophys. Res. Lett., 36, L07503, doi:10.1029/2009GL037274.

Cheers,
Lodger

Artful Dodger

Hi Wipneus,

This is something I should ask Wayne Davidson, but I think that arctic aerosols are a major factor in the lower optical depth of the Northern atmosphere.

Aerosols are monitored by AFI at Ny-Ålesund, Spitsbergen and by NOAA at Barrow, Alaska. I'll be watching the changes as development comes to the North.

Cheers,
Lodger

Chris Reynolds

Artful Dodger,

Check the main graphic of Neven's post, Signs of Artic Change. You mentioned the position of the Jetstream w.r.t. the AUgust storm. This year's summer low pressure anomaly around the Greenland high produced a band that tracked the progress of the Arctic low that produced the August storm. Most years the pattern tracks lows across the land of Siberia.

Artful Dodger

Hi Chris,

There was only one jet core present in the Central Arctic on Aug 3-4, 2012. Look at this series of charts of the polar jetstream:

12080300
12080306
12080312
12080318
12080400
12080406
12080412
12080418

The GAC2012 event was not simply a surface low pressure system. It also had a considerable depression at the 500 mb level (18,000 ft or 5.5 km pressure altitude).

It's this higher level of the atmosphere that the polar jetstream helped to spin up, and contributed to the formation, and the strength, of GAC-2012.

Cheers,
Lodger

Artful Dodger

Peter Wadhams speculative calculation does not work in the real world, since extra heat absorbed due to albedo change stays in the Arctic. This is from the abstract to Kumar et.al (2010) "Contribution of sea ice loss to Arctic amplification"

"Sea ice loss did not appreciably contribute to observed 2007 land temperature warmth equatorward of 60°N. Likewise, the observed warming of the free atmosphere attributable to sea ice loss is confined to Arctic latitudes, and is vertically confined to the lowest 1000 m."

Heat does not move against a temperature gradient. It always flows from warmer to cooler. As long as the Arctic is cooler than the South, the heat stays put, or is radiated to space (the next coolest place).

It's like trying to paint your attic by splashing paint in the basement. It don't work. At least not until the basement is full.

Give it perhaps 40 years, this will be an issue after the Winter ice disappears. Then the Arctic ocean may be warmer than peripheral seas at the end of Summer, and heat/water vapour will flow downhill...

Bdwo

"Heat does not move against a temperature gradient. It always flows from warmer to cooler. As long as the Arctic is cooler than the South, the heat stays put, or is radiated to space..."

But a lot of the heat gained in the tropics is transported to the poles before being radiated into space - and with warmer poles, and lower gradient, less gets transported poleward. Jacking up the temperature locally at the poles by decreasing albedo results in less transport of heat poleward and warmer temperatures globally even without any changes elsewhere.

I wonder if the larger annual variation in ice freeze/melt will cause large annual cycles in the AMOC, and if more open (esp. summer) water will change the balance between latent and sensible heat transport in the atmosphere - with concomitant changes in the weather.

Andy Lee Robinson

Was a nice surprise to see Newsnight used my animation, even if they didn't use my proper name!
Updated version to Sep 2nd:
http://youtu.be/EnCy-R7mLHI

wayne

Lodger,

Nice sketch, what is missing or needs correction is the 45 N bit, and also the extra cyclones brought by the Jet stream at 70 N. and Northwards. These cyclones are brought up because its warmer from over all thinner ice during winter, and from wider open sea surface during summer.

I like the solar insolation bit, you may add the atmosphere is much much cleaner up here, making an even smaller OD.

Artful Dodger

Thanks, Wayne.

Enjoyed your post on the 'cold North pole'. I think this has huge repercussions for the ultimate fate of the pack ice North of Greenland/Ellesmere Island.

A persistent high over BG, combined with frequent lows over the central pack due to open water, means a reversal of the normal clockwise rotation of the gyre.

Inside, c-clockwise rotation leads to sea ice advection through Fram strait of the oldest sea ice, instead of its preservation.

A catastrophic change over a decadal timescale, but already visible in its effects this year:

http://iabp.apl.washington.edu/maps_daily_tracknsidc.html

Stay frosty, mate!

Cheers,
Lodger

wayne

Lodger

The flow of ice in the remaining pack is really odd, out of normal especially along the Archipelago NW coast. unrecognizable is a better word. Yet the ice extent melt was greater than sunnier 2007. This points out solidly to an irreversible downward melt rate. Sorry about the summer rain projection for UK and Ireland, but is likely that winters will be milder and more frequently settled.

dorlomin

Peter Lilley the rent a quote skeptic brought in for this TV program has an interesting new job.

Recently appointed non Executive Chairman of an oil exploration company.

Hat tip to Leo Hickman.
http://www.tethyspetroleum.com/tethys/newscontent.action?articleId=2355562

Artful Dodger

Congrats, Andy Lee. Your 3D sea ice volume video has been featured on Joe Romm's Climate Progress Blog. Well done!

http://thinkprogress.org/climate/2012/09/11/832161/arctic-death-spiral-the-video/

Looking forward to your '3D Death Spiral' video!

Cheers,
Lodger

Andy Lee Robinson

Thanks Lodger - let's hope it'll go viral and draw attention to what is really happening up there.
The new one is still in development - not a trivial process with thousands of parameters to play with, but hope it'll be ready soon.

Neven

Great work, Andy. Sorry for not giving it a platform on the blog here. I was too busy and then forgot about it. I'll post the new one in a separate blog post as soon as you're done.

Al Rodger

Andy Lee,
As well as BBC2's Newsnight, I would also expect to see your excellent PIOMAS animation appearing on the "BBC documentary entitled 'Operation Iceberg', to be broadcast in October," that was announced within the Susan Watts item on Newsnight (& which the Newsnight item appears to have been compiled from).

Al Rodger

Carbon Brief have posted a transcript of the Newsnight Programme. They do describe it as "a rough transcript" elsewhere on their site, so be warned. One correction I spot from the off - Natalie Bennett is not an MP. She did try in 2010 in 'Holborn & St Pancras' but only came 4th. (Her predecessor was the MP.)
http://www.carbonbrief.org/blog/2012/09/transcript-newsnight-on-the-arctic

Al Rodger

Hi Andy Lee,
Carbon Brief have a vistor from the BBC production team on their comment thread.
I mentioned (& linked) your up-thread "jolly complaint" about not using your real name.
http://www.carbonbrief.org/blog/2012/09/bbc-makes-a-locally-sourced-meal-of-discussing-arctic-sea-ice-melt#comment-653018607

Andy Lee Robinson

Neven, thanks - I'll let everyone know here. Hope you enjoyed your holiday in spite of its timing!

Al, thanks for your support and the plug. I am following the carbonbrief article too, suffering from information overload with 200+ open tabs, and many distractions managing my servers!
I think I've read every twitter message that has ever been posted since July!

I'm not too bothered about attribution — visceral satisfaction is enough — the main thing is that it gets seen and shared by as many people as possible.

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