Tuesday, 24 January 2012

Dr Jennifer Francis on Arctic weather impacts.

Dr Jennifer Francis recently gave an excellent lecture at the Weather and Climate Summit about the wider impacts of the loss of Arctic sea-ice. I was lucky to see it via the internet last weekend and have waited until now to discuss because the presentation has only just been posted on YouTube.  The video is 1:24 long, but is well worth viewing.


Dr Francis's powerpoint presentation can be downloaded here, probably easiest to right click and 'save as'. The presentation will be most legible run as full screen from powerpoint.


As usual I'll post  link to the video as the Blogger video window is miniscule.
http://www.youtube.com/watch?v=RtRvcXUIyZg


Dr Francis outlines the changes in the Arctic sea-ice as a background to the 'meat' of her lecture. I've already discussed the loss of multi-year sea-ice and the consequent thinning of the Arctic polar ice, you'll find more information here and here. And I've mused upon Maslanik's 2011 paper on recent trends in multi-year sea-ice and the 1990s period of positive Arctic Oscillation, here.

Surface temperature inversions have in the past capped the interaction between sea-ice and the atmosphere. However these have lessened in recent years and now the near-surface warming due to extensive open water is changing the atmosphere in the Arctic. Dr Francis states that the Arctic Dipole is a result of a high amplitude jet stream, that's not what I've gleaned from what I've read and it's something I'll have to mull over.


The reduced pole-equator temperature gradient is leading to weather patterns that are 'getting stuck'. As I've previously discussed, the jetstream has waves on it called Rossby waves, these waves move around the jetstream, the jetstream being formed by the boundary between cold Arctic air and warm subtropical air. However what Francis argues is that due to the reduced pole-equator temperature gradient (because the Arctic is warming, e.g. here) there is a reduced flow along the jetstream, the speed of the Rossby waves has reduced, and the wave amplitude has increased, with peaks moving further into the Arctic (which reminds me of the findings of increased mid latitude storm penetration into the Arctic).

Stu Ostro is mentioned in the questions, parts of the presentation are reminiscent of Stu Ostro's work on troughs and ridges around the Arctic. However Dr Francis is presenting images of troughs and ridges oriented longitudinally (across), whereas Ostro was concentrating on latitudinal ridging (up down), e.g. here, warning 20Mbyte pdf - right click and 'save as'.

The increase in wave amplitude is occurring around the northern hemisphere, however ridge peaks are located mainly just west of Greenland. This seems to explain the warm temperatures being experienced by that region e.g. Nunavut around Baffin Bay, CBC News. So whilst the findings of increased amplitude are hemispheric in nature, North America is the centre of action of the greatest ridging. If this is a persistent pattern into the future it could be important for melt from Greenland, because the atmospheric ridges are driving warm mid latitude air into that area.

Dr Francis also stated that early snow melt is allowing soils to dry earlier and additional warming as a result to feed Arctic Amplification. The early snow melt is correct, but I've not been able to look into soil drying as yet. However this issue immediately brings to mind Hansen's Climate Dice and the worrying connection I see between that and the danger of increasing drought, here. If we are seeing a drying around the Arctic this also has an impact on carbon emissions, as the Arctic warms if it mainly wet then emissions of methane may dominate, however if it is mainly dry carbon dioxide may dominate, and peat fires may add yet more carbon.

I've recently posted about a pre-print I've read by Cohen et al that (in my opinion) convincingly shows that the Arctic Oscillation is strongly connected with the rate of advance of Siberian snowfall, more here. Dr Francis didn't mention this or Cohen's preceding work, indeed she initially framed as a paradox that we've had recent cold winters despite global warming, then said she thought those cold winters were just weather and probably have no significance in terms of climate change.

My working theory remains that of Cohen - that Arctic sea-ice loss, mediated by Siberian snowfall, is responsible for the increasing tendency to cold winters in northern Eurasia, Europe, and the East coast of the US. However Cohen's findings and Francis's findings are not mutually exclusive. The results of the loss of Arctic sea-ice are not simple, nor do they affect each continent in the Northern Hemisphere in the same way.

15 comments:

Kevin O'Neill said...

Chris, did you read Winter Northern Hemisphere weather patterns remember summer Arctic sea-ice extent by Francis et al, 2009?

This paragraph deals a bit with precipitation:

Of particular interest is the influence of summer seaice variability and loss on northern hemisphere precipitation, as future changes in freshwater resources are a vital concern in many regions. Precipitation data are noisy by nature and tend to be less reliable, particularly in mountainous areas and high latitudes where much of it falls as snow. A regression of actual summer sea ice extent with precipitation data yields a noisy yet significant tendency for increased precipitation over much of the region north of approximately 40 N. More revealing and illustrative is the composited difference in winter-mean
precipitation after summers when ice extent was less than and greater than 1 standard deviation from the 1979 – 2006 mean. A coherent area of negative anomalies is evident over a large region of the northeast Atlantic Ocean extending into northern Europe as well as over much of the U.S. and Alaska.

Chris R said...

Thanks for that. It's been over a year since I read that paper and figure 4 is a detail I'd forgotten, figure 3 being the 'take home' message I remember.

I wonder how much else I've forgotten from the papers I've read. :(

It might be informative to try to compile the papers showing links between observed weather patterns and Arctic sea-ice loss.

Have you any thoughts about the AD / jetstream link?

Kevin O'Neill said...

"...any thoughts about the AD / jetstream link?"

No. :)

I think this is why scientists use computer models. Computers don't forget. I've been breaking in a new laptop and haven't transferred pdfs of climate papers onto the new one. I read a paper now and wonder if it's familiar because I've read it before or if it just echoes similar research. It doesn't help that I've never been a note taker.

I haven't been able to put all of the research together into one coherent set of bullet points. The closest I get is:
* Increased GHGs lead to global warming (and stratospheric cooling)
* These effects are amplified in the Arctic; as a result we see
* Arctic Sea-ice decreases and a smoothing of the latitudinal temperature gradient
* These in turn have direct and indirect effects on both regional and global weather (jetstream, Rossby Waves, AO, AD, snow cover, etc.)

Throw in the chaotic nature of the system, numerous feedbacks, and the intermingling of different effects. What we're left with is a need for a global climate computer simulator :)

Sorry, not much help. Just restating the obvious. The chicken or egg conundrum seems to be a regular feature of every piece of the climate system.

Kevin O'Neill said...

A new paper: IMPACT OF SEA ICE COVER CHANGES ON THE NORTHERN HEMISPHERE Jaiser et al, 2012, Tellus A

We showed that Arctic heating anomalies due to low sea ice concentrations in late summer (August/September) trigger changes in baroclinic systems in autumn because of an earlier onset of baroclinic instability that influences the structure of large-scale planetary waves in the following winter. The baroclinic structure of the direct response in autumn is linked to different patterns of pressure anomalies at the surface and in the mid-troposphere, which are related to the decrease in sea ice concentration. Decreased static stability and changed meridional temperature gradients induce an earlier onset of baroclinicity north of 75 N with greater amplitude.

They do mention snow cover, but more as a secondary effect. This seems much more in line with Francis' reasoning.

Kevin O'Neill said...

My favorite sentence from Jaiser et al:

As shown by Sempf et al. (2007), these interactions are the main drivers for seasonal and decadal-scale changes between positive and negative AO phases, which can be considered as atmospheric flow regimes resulting from chaotic wandering of the trajectories in phase space on the ruins of merged attractors.

... on the ruins of merged attractors...

That sounds like a great paper all by itself :)

Chris R said...

Thanks Kevin,

I've not got around to reading it but will do as soon as I've posted the posts on methane - that's why I've gone quiet recently.

I still think Siberian snowcover remains a factor in cold winters, 2009/10 being an example that's supported strongly. I note that Cohen is a co-author on Jaiser et al.

However until I've read the Jaiser paper properly I can't comment. Actually I'll print it off and see if I can read it on the bus tomorrow.

Chris R said...

Kevin,

I've finally read the paper, thanks for recommending it to me.

The first unrelated point is that they don't interpret the Graversen et al / Screen & Simmonds disagreement as I have been (which probably means I'm wrong). I've been working on the assumption that Graversen's paper showed that the influx of sub Arctic air was responsible for tropospheric warming, but Screen & Simmonds showed this not to be the case by deomonstrating the source of the warming was from the boundary layer (i.e. open ocean replacing sea-ice). However according to Jaiser et al Graversen did a second paper that showed the same result using a different dataset. I'll have to look at Screen & Simmonds again. The problem is that Graversen 2008b is probably paywalled as it's an on line supplemnet at Science.

One thing that strikes me about Jaiser et al is that they use 1990-2000 as a period of high ice, 2000-2010 as a period of low ice. However the AO was +ve in the former period and neutral in the latter. So I can't help but wonder how much of Jaiser et al's results could be due to the different AO modes. On first reading I don't see this addressed.

The paper as a whole stretched my knowledge. Whilst I know what baroclinic & barotropic mean in words, my understanding isn't good enough to translate that into a wider understanding. The translation of an initial (autumn) baroclinic (frontal type synoptic situation) into a subsequent (winter) barotropic (stable - non frontal synoptic) response is something I've read about before in connection with this matter. Just found the ref - 'The Seasonal Atmospheric Response to Projected Arctic Sea Ice Loss in the
Late Twenty-First Century' - Deser et al, 2009. PDF That's another case of models finding something that has later been observed. However whilst I understand the individual paragraphs of Jaiser et al, I still don't fully grasp the whole picture and it's details (hence implications).

I'm going to read Jaiser et al again and if I can't work out my problem regarding the AO then I'll consider contacting Judah Cohen about it.

If you're interested in pursuing this issue then I recommend: Dagmar Buddikova's "Role of Arctic sea ice in global atmospheric circulation: A review" PDF

I could do with re-reading some of these papers. It's been years since I did a load of reading on the atmospheric implications os sea-ice loss.

PS- while looking for information about Eady Waves I came across this paper. Which is quite large. A glance over it shows the main problem I have in this field - the maths is rather daunting and until you understand the maths behind the principles, you don't properly grasp the basic principles.

Lazarus said...

That for the link to the vid. I'm trying to catch up on so many blogs I have only just go to this.

Jet Stream blocking seems more and more common. I hadn't heard about it until a few years back (2009?) when the UK had an unusually cold winter (the coldest since 1963 If I remember correctly) while the Arctic was positively balmy.

Then the meteorologists were blaming blocking for diverting the Jet Stream and causing the cold snap. Since then I have seen it used to explain several 'global weirding' events.

Chris R said...

Hello Lazarus,

I too suffer from blog-backlog.

I'm looking forward to seeing what Francis publishes on this.

I'm not sure how much blocking has increased, I think you're hearing more because it's being talked about more. From the Hovmoeller diagrams in the Francis slide shows the changes are still small. There are trends but they're eas to miss in the noise of variability.

I think we're only seeing the start of this, which is part of the fun - seeing what you can get right about impacts to come.

PS - I'm going to watch the second part of Liz Bonin's BBC documentary about animal intelligence - catch it on iPlayer if you've missed it. (There I go dumping more things to watch on you)

Kevin O'Neill said...

Chris - thank for the link to the Buddikova research summary - I'd run across it before and forgotten about it. The Duffy thesis is *not* something I'll be exploring in the near future.

I can only follow it in a general sense - and even at that I was having to look up way too many terms. I never got far enough to be stumped by the math :)

Chris R said...

In due course I'll be doing some more posts on the issue of the wider atmospheric impacts. But not immediately - it's not like there's any rush.

PS - noticed you referenced one of my posts over at Barely Science. It'll be interesting to see if Goddard approves the reply to some of the comments there.

Jennifer Francis said...

Hello Chris, Kevin, and all -- I've enjoyed reading your comments on my presentation and related papers. I have a GRL paper coming out in a week or two. Send me an e-mail and I'll send you a pdf: francis@imcs.rutgers.edu

Chris R said...

Hello Jennifer, glad you popped by and enjoyed reading our amateur musings. I've enjoyed reading your papers. I'll be emailing you.

Фара Уст said...

Это не исследование, а банальный бабий бред. Поскольку струйные течения формируются как результат суперпозиции барических систем. При этом надо понимать, что все значимые барические образования формируются и живут в результате воздействия краткосрочных локальных изменений гравитационного поля планеты!!! Поэтому все теории о глобальности антропогенного влиянии на климат в принципе ошибочны. Земля сама управляет климатическими процессами. А Дженифер передайте, что она обычная глупая баба, желающая известности, поскольку других оценок её измышления не заслуживают.

Chris Reynolds said...

To translate the above comment (using Google Translate):

"This is not a study, but a banal woman's nonsense. Since the jet streams are formed as a result of the superposition of pressure systems. It should be understood that all of the relevant pressure systems are formed and live as a result of the impact of short-term local changes in the gravitational field of the planet! Therefore, all the theories of global anthropogenic influence on the climate in principle wrong. The land itself is run by climate processes. And Jennifer, pass it the usual stupid woman that wants fame as other assessments of its allegations do not deserve."

My response.

Unevidenced, poorly reasoned nonsense.

1) The Jet is influenced by surface conditions, it forms pressure systems.

2) You introduced the gravitational field. Nobody else has mentioned it.

3) Anthropogenic change is real and ongoing.

And on that final point I'll be marking all further posts by you as spam because this is a denialist free blog.

Take it to WUWT.