WUWT commenter Ian Cooper says:
I thought that this site may be of interest to those pondering the warming of the Antarctic Penninsula. I came across this while I was scouring the net to learn more about the Southern Annular Mode (SAM) and it’s influence on our local New Zealand weather/climate. I hadn’t seen this here before, so apologies in advance if someone has already brought this to your attention. I was particularly taken by the second paragraph of this page, which I have copied below.
Due to the southward shift of the storm track, a high SAM index is associated with anomalously dry conditions over southern South America, New Zealand and Tasmania and wet conditions over much of Australia and South Africa. The stronger westerlies above the Southern Ocean also increase the insulation of the Antarctica. As a result, there is less heat exchange between the tropics and the poles, leading to a cooling of the Antarctica and the surrounding seas. However, the Antarctic Peninsula warms due to a western wind anomaly bringing maritime air onto the Peninsula (Fig. 5.9). Indeed, the ocean surrounding the Antarctic Peninsula is in general warmer than the Peninsula itself and stronger westerly winds mean more heat transport onto the Peninsula. Over the ocean, the stronger westerly winds tend to generate stronger eastward currents. Furthermore, the divergence of the currents at the ocean surface around 60oS is enhanced because of a larger wind-induced Ekman transport. This results in a stronger oceanic upwelling there.
From: Universite catholique de Louvain
http://stratus.astr.ucl.ac.be/textbook/chapter5_node6.html
The Southern Annular Mode
The equivalent of the NAM in the Southern Hemisphere is the Southern Annular mode (SAM). Various definitions of SAM have been proposed: a convenient one is the normalised difference in the zonal mean sea-level pressure between 40 oS and 65o S. As expected, the sea level pressure pattern associated with SAM is a nearly annular pattern with a large low pressure anomaly centred on the South Pole and a ring of high pressure anomalies at mid-latitudes (Fig. 5.8). By geostrophy, this leads to an important zonal wind anomaly in a broad band around 55oS with stronger westerlies when SAM index is high.
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Due to the southward shift of the storm track, a high SAM index is associated with anomalously dry conditions over southern South America, New Zealand and Tasmania and wet conditions over much of Australia and South Africa. The stronger westerlies above the Southern Ocean also increase the insulation of the Antarctica. As a result, there is less heat exchange between the tropics and the poles, leading to a cooling of the Antarctica and the surrounding seas. However, the Antarctic Peninsula warms due to a western wind anomaly bringing maritime air onto the Peninsula (Fig. 5.9). Indeed, the ocean surrounding the Antarctic Peninsula is in general warmer than the Peninsula itself and stronger westerly winds mean more heat transport onto the Peninsula. Over the ocean, the stronger westerly winds tend to generate stronger eastward currents. Furthermore, the divergence of the currents at the ocean surface around 60oS is enhanced because of a larger wind-induced Ekman transport. This results in a stronger oceanic upwelling there.
The majority of the effects of SAM could be explained by its annular form and the related changes in zonal winds. However, the departures from this annular pattern have large consequences for sea ice as they are associated with meriodional exchanges and thus large heat transport. In particular, a low pressure anomaly is generally found in the Amundsen Sea during high SAM-index years (Fig. 5.8). This induces southerly wind anomalies in the Ross Sea (Pacific sector of the Southern Ocean) and thus lower temperatures and a larger sea ice extent there (Fig. 5.9). On the other hand, because of the stronger northerly winds, the area around the Antarctic Peninsula is warmer when SAM index is high, and sea ice concentration is lower there .
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Paul Vaughan asked:
“Stephen Wilde, I am curious to hear at some point in time (as the weeks & months unfold) which researchers have most influenced your noticeably sharpened focus over the past few months.”
Leif Svalgaard effectively scotched radiative physics as a cause of real world observations so after some thought it seemed likely that the radiative processes were being trumped by chemical processes.
Various sources showed stratospheric and mesospheric cooling when the sun was more active so the question was whether that was artifially induced by CO2 and CFCs or whether it was natural. Joanna Haigh’s finding of increased ozone above 45km despite a quiet sun potentially produces the required reverse sign solar effect in those two layers and again points to natural chemical processes trumping radiative processes.
Apart from that it is recent real world events that are sharpening the focus. I’ve been going on about reduced jetstream zonality for three years now having first noticed it around 2000. It is now widely commented on.
There are now so many real world developments that fit my narrative that confidence and precision are increasing. Instead of being rebutted by new papers I am finding that they fit in rather neatly.
There are a number of possible events that could screw it up though. I’ll just have to wait and see.
Well I think I have figured out a plausible reason why the Antarctic Peninsula is warmer than the rest of Antarctica.
Looking at that first colored relief map of the Antarctic Continent, it appears that the Antarctic Peninsula actually protrudes outside of the Antarctic Circle; which if I’m not mistaken means that the sun never disappears completely for more than 24 hours.
And that Peninsula also seems to point right at the tip of South America, so it constricts the Atlantic, and Pacific sides of the southern ocean that goes sloshing back and forth through there every day. Those tidal bores, would seem to wash right undeer the floating ice shelves on the East side of the Peninsula (as well as the West), and that could raise, and break those shelves occasionally exposing more of the coastline to those lapping waves. Maybe that’s why Larsen B fell down.
Well it’s just a theory; there might not be any truth to it.
This results in a stronger oceanic upwelling there.
This is the most interesting and important sentence in the above article.
Stephen Wilde says:
February 6, 2011 at 5:48 am
So a cooling stratosphere with an active sun and a warming stratosphere with a less active sun just has to be the natural order of things and if we have affected it at all then our contribution is probably too small to measure.
Hi Stephen, I think your on the right track but there is a conundrum. The Sun has been quite for at least 12 months, during that time we see 2 opposites occurring. The north polar stratosphere is warmer with a weaker vortex and a negative AO over that period. This is creating the jetstream movement that is cooling the top hemisphere.
But in the south the opposite is occurring, we have a cooler stratosphere with a strong vortex and a highly positive AAO (SAM) which is contracting the southern jet stream (which strengthens the La Nina). Both hemispheres are showing what you would expect in regard to ozone. There is a lot less at the south pole. There has to be another factor involved that is controlling the ozone quantities other than just total solar EUV output.
I have plotted the monthly AO/AAO index in an attempt to flush out some trends. On the whole the two patterns follow each other in their overall trends but the baseline can vary for each index. The trends happening now and back around 1979 are interesting showing a larger divergence between the indexes during low EUV. The December values being more relevant for the northern hemisphere winter.
Thanks Geoff. I’ve been aware of that conundrum for a while and concerned in case it indicated different responses at each pole from solar variations. Generally I have been assuming similar if not identical responses.
However as you say ” the two patterns follow each other in their overall trends but the baseline can vary for each index”.
So I agree that the characteristics of the Antarctic upper atmosphere lead to it responding slightly differently for some reason but not so much as to invalidate my general global scenario.
Clearly the southern oceans heavily influence the lower atmospheric layers but the solar effects seem to predominate above 45km as suggested by the findings that Jo Haigh has publicised.
I’d be inclined to look at how the solar effects on ozone quantities above 45km vary at the southern pole as compared to at the northern pole but the data is not currently available. Those Haigh findings were quite a surprise since ozone above 45km is not supposed to increase when the sun is quiet.
I’m sure that investigations are ongoing.
Russian scientists have been publishing about meridional vs. zonal circulation regimes for 7 decades. (This certainly is not a “new” concept.)
Major recent development:
Le Mouël, Blanter, Shnirman, & Courtillot (2010) have shone a bright light on the CORE role of SUBannual processes.
Limiting focus to higher timescales is like ignoring the role of the piston in an engine! [Or more precisely: the role of 2 antiphased pistons & their spatiotemporal aliasing in a dynamically asymmetric cylinder.] “Anomalies” are fatally misleading for researchers unaware of their limitations.
While I take issue (at a fundamental level) with some of the assumptions built into the following conceptualization, Sidorenkov’s p.433 [pdf p.10] supplements Leroux (1993) and might trigger awareness of the NEED to consider SUBannual processes:
Sidorenkov, N.S. (2005). Physics of the Earth’s rotation instabilities. Astronomical and Astrophysical Transactions 24(5), 425-439.
http://images.astronet.ru/pubd/2008/09/28/0001230882/425-439.pdf
Le Mouël, Blanter, Shnirman, & Courtillot (2010) have taken things to a whole new level, but it is evident in discussions here that participants are (so far) lacking the background to appreciate the seminal findings. Perhaps Leroux’s (1993) figures 8-15 & Sidorenkov’s exposition on heat engines will help with dot connection.
[Note for those thinking about this more deeply: I’m very, very far from being convinced that a linear decomposition (based on questionable assumptions) of the overlapping heat engines is the approach most likely to facilitate increasingly penetrating insight.]
Stephen Wilde says:
February 8, 2011 at 1:27 am
Stephen I am not sure if you are still viewing this thread, but I came across a paper that has some answers to the conundrum. Its a very big informative read by Baldwin et al, but the main thrust is that the QBO and planetary waves control the NH polar vortex and have very little influence on the SH vortex. Of interest the authors speculate that there is a solar component in the QBO as well as a strong possibility that EUV could modulate the NH planetary waves, this could explain the divergence on my graph. The planetary waves seem to be the major driver in breaking up the NH vortex which in turn influences the AO. I couldn’t find any secular changes in stratospheric temps or ozone in the last 2 decades that would affect the NH polar vortex. A different story for the SH vortex though that seems to be in a different league.
Also of interest was if the planetary wave is strong enough it does not matter what phase the QBO was in, it still affected the NH vortex.
Useful stuff, Geoff.
Thanks.
South-polar temperatures by satellite (http://vortex.nsstc.uah.edu/data/msu/t2lt/uahncdc.lt ) should be less vulnerable to human distortion and manipulation than surface measurements. Since their inception in December, 1978, they indicate a cooling trend of 0.08 degrees C per decade.
“If your result needs a statistician then you should design a better experiment”
I believe Rutherford also said Science is either physics or stamp collecting.
I was trained in the physical sciences so I see where Ruthorfords prejudices are coming from.
Physicists dealt with simple systems that were almost exactly reproducable and therefore statistical treatments of experiments were not required. This was in the days before the quantum revolution and the uncertainty principle changed physics forever.
Other sciences deal with complex systems for which an entirely reductionist approach – separating the phenomenon to be studied from everything else going on in the system is not possible. I learned that when I moved into biomedical research.
Climate is another messy system where all the contributing factors cannot be teased out and studied seperately. Statistics are required.