Comments 1 to 20:

1. Alpinist at 09:10 AM on 18 November, 2012
   See also http://www.climatecentral.org/news/changing-winds-the-smoking-gun-in-antarcticas-growing-sea-ice-15246 over at Climate Central. Tamino had an extensive series of posts on this as well.
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2. JoeT at 09:33 AM on 18 November, 2012
   A question about the ozone hole: Why is it predominantly over Antarctica? Why not over the Arctic as well? What's curious is that the temperature gradient is increasing in the southern hemisphere, but decreasing in the north.
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3. mercpl at 10:03 AM on 18 November, 2012
   Like JoeT, I was also struck by the statement that the temperature gradient between the Equator and the Antarctic is increasing. This is at opposite of what's happening in the Arctic is it not? I have also read recent reports of the warming of the Antarctic penisula. So are we only talking about the Antarctic Stratosphere? I understand that that has cooled because of the decline in Ozone which is in itself a powerful greenhouse gas. But then again I thought that Ozone levels were increasing because CFCs have been banned. So you could say that I am a bit confused. So here's my take of the explanation. 1. Ozone depletion causes the Antarctic Stratosphere to cool. 2. Cooling Stratosphere causes stronger west to east winds. 3. Stronger winds cause the ice to drift north, opening up more gaps. 4. These gaps encourage formation of new ice resulting in more ice area.
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4. bill4344 at 10:26 AM on 18 November, 2012
   +1 on wanting to see more discussion of why the temp gradient would be increasing - and speeding up winds - in the SH, but decreasing - and causing the giant looping whorls in the jet-stream - in the NH. My assumptions are similar to mercpl's, but I had also believed the Antarctic ozone hole was slowly but significantly repairing. Given that in NH it's generally pointed out that the equatorial rate of warming is slight compared to the dramatic heating of the pole, a not-much-warmer equator and a slowly-healing Antarctic ozone hole would not at first glance appear to make for a steeper temperature gradient. Also: volume!
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5. Bob Lacatena at 10:51 AM on 18 November, 2012
   JoeT, There is greater air exchange between the pole and mid-latitudes in the North Pole than the South, I think primarily because of the differences in land masses. The end result is that ozone depletion is greater at the South Pole (the southern polar vortex creates more of a closed system over the South Pole).
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6. Bob Lacatena at 10:52 AM on 18 November, 2012
   JoeT, In effect, part of what made Hurricane Sandy into what it was is the same thing that is minimizing ozone depletion in the north.
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7. Will MacKinnon at 00:38 AM on 19 November, 2012
   Although the increases in Antarctic ice maximums in no way balances the Arctic ice minimums, a visual study of the ice area/extent graphs does appear to show a link between these two events. Antarctic maximums in 2007 and 2012 correspond (in kind if not extent) with Arctic minimums. Recent explanations of Antarctic maximums ignore this link. Until until a physical link or a statistical anomaly can be shown this will continue to be a crutch for climate miss-informers (I don't believe there is such a thing as an informed skeptic!). Looking at the graphs I believe that there is a link that is not understood at present.
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8. JoeT at 03:06 AM on 19 November, 2012
   Sphaerica, I'm not following your argument. Most of the CFCs were released in the north, so if Antarctica is a closed system, why is there an ozone hole in the south? A quick internet search to my question comes up with an answer that CFC affects ozone at very low temperature and a larger ozone hole is over Antarctica because it is colder there. The question then is moved to -- why is it colder to begin with? It looks like a positive feedback system would also be set up --- if it starts out colder, then the CFCs destroy more ozone. And since ozone is responsible for making the stratosphere warmer than the troposphere, the extra cold would have an even bigger effect. Sooooooo ---- why is the south pole colder to begin with?
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9. Bob Lacatena at 03:45 AM on 19 November, 2012
   JoeT, It's a little more complicated than that. I'm not claiming to be an expert, but... First, yes, it is colder at the South Pole, because Antarctica is a land mass with mountains, surrounded by ocean. The ice is piled on top of this land (snowfall there accumulates), and as you know temperature decreases with altitude. Thus, much of the ice there has no chance of melting, because even under the 24-hour summer sun, it doesn't get above freezing. By contrast, the Arctic is an ocean surrounded (for the most part) by land. As such, snowfall accumulates in the winter, but being at sea level it has the chance to melt back (more or less) in summer. At the same time, in summer the land masses around the Arctic heat and cause weather systems that push north. The oceans around Antarctica cause an entirely different (and more moderated) dynamic. This major difference in geography results in drastically different mechanics at the two locations, and much lower temperatures in Antarctica, which allows polar stratospheric clouds to form, which help to catalyze ozone depletion. My comment about Antarctica being a "closed system" was simply an analogy to the fact that the stronger polar vortex in the south (a result of the difference in land masses and temperatures) helps to contain things (temperatures, CFCs) over Antarctica in contrast to the Arctic, where the more moderated temperatures also allow for more of an exchange of air masses (what become winter storms for those in North America and Europe, but have the equal-and-opposite reaction of injecting warmer air into the Arctic itself). As far as CFCs being emitted in the north... I can't find a reference, but I would doubt that is much of a factor. Like CO2, things released into the air are going to wind up, over time, dispersing fairly evenly. What is of more importance is the creation of the right conditions (very cold temperatures and polar stratospheric clouds in the Antarctic) to allow CFCs to do their dirty work.
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10. Bob Lacatena at 04:03 AM on 19 November, 2012
    JoeT, Please note that this geographic and mechanical difference in the two systems (ocean surrounded by land in the north, land surrounded by ocean in the south) are at the core of the above post (i.e. the apples/oranges aspect of the whole thing). The differences are very dramatic and important.
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11. JoeT at 06:31 AM on 19 November, 2012
    Sphaerica, Good explanations. Thanks. I'm almost there. One last thing will clinch it for me. You explained very well why the ice in Antarctica is colder than the Arctic. However, why is the stratosphere over the Antarctic colder than the stratosphere over the Arctic?
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12. gws at 08:24 AM on 19 November, 2012
    JoeT Stratospheric T at high latitudes is determined by a stratospheric circulation called the polar vortex. It forms each winter over the respective pole. Over Antartica, the vortex is strong as its structure remains nearly undisturbed by undulations at lower levels in the atmosphere. The shape of the Antarctic continent aids in this setup as the vortex takes on a size and form similar to the continent below it. Once formed, it isolates the polar stratospheric air mass from air at lower latitudes and it progressively cools in the dark winter. In the northern hemisphere, undulations (waves) below the stratosphere driven by temperature differences and geography of the surrounding landmasses prevent a stable vortex formation. The vortex usually remains intact only for a few days before air from lower latitudes mixes in again. Therefore, the Artic stratosphere is usually warmer and an "ozone hole" rarely forms. Stable Artic vortices do, however, form, such as in winter 1997/98 and recently in 2011/12, when drastic Artic stratospheric ozone losses occurred as a result.
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13. vrooomie at 08:31 AM on 19 November, 2012
    gws, as a geologist, I appreciate your simple, but clear and concise, explanations of this phenomenon. The NP and SP (and by extension the NH and the SH) are really two quite different animals, for all the reasons you list. Another one to keep in mind is that the S. polar summer maximum is at perihelion, whereas the N. polar summer is at aphelion. Were it not for that fact, the summers in the desert SW of the US would be unbearable. It's all quite complex, and deniers rarely admit as much, which just clouds the water...so to speak!
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14. Bob Loblaw at 08:35 AM on 19 November, 2012
    JoeT: Note that the polar ozone holes develop in the spring, when sunlight is returning to an area that has spent months in darkness. The chemical reactions are largely photo-driven [primarily UV light], after a build-up of certain molecules that don't persist in sunlight. As soon as UV radiation is available again, the reactions start and ozone is rapidly consumed. The long polar night leads to low temperatures in general - the polar regions lose IR radiation to space, and the only sources of radiation to counteract that loss will be either thermal energy stored in the system locally - atmospheric, or in the ice/land (south) or ice/ocean (north)- or energy brought in from sub-polar areas (atmospheric or ocean currents). If locally-stored energy is lost to space, the system has to cool. If energy brought in from sub-polar regions is not enough, cooling will continue. Thus, the antarctic represents a system where other energy sources can't counterbalance the IR losses as well as in the arctic, so the antarctic gets colder. Both regions exhibit strong temperature inversions near the surface (i.e., coldest at the surface, instead of coldest at the top of the troposphere), and the stratosphere is not immune to this pattern. As the surface and lower troposphere cool, so will the stratosphere. After all, the normal stratospheric heating by UV absorption (the reason the stratosphere exists in general) isn't happening in the polar night. To put it simply, the stratosphere isn't independent of the surface.
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15. Daniel Bailey at 08:50 AM on 19 November, 2012
    Additionally, IIRC, the stratosphere over the Arctic is closer to sea level than that over the Antarctic. This is primarily due to the fact that the Arctic is essentially all at sea level while Antarctica is a monolithic ice cube resting on bedrock, immersed in a warming saltwater bath. Thus, the Arctic gets heat imported to it via the oceans (some 40% of sea ice melt there is via bottom melt). Due to its altitude, Antarctica gets no such pipeline of energy delivered to it. The accumulation zone on Antarctica is too high for melt ponds to form, while melt-ponding on the Arctic sea ice helps deliver some 18-20% more energy into the ocean below the ice, also helping warm that body of water indirectly.
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16. Doug Hutcheson at 13:52 PM on 19 November, 2012
    I see Harrison Schmidt of Heartland is keeping the faith. What annoys me about humanity is that people equate the honorific 'Dr.' with infallibility. I know many PhDs publish here, but none of them asks us to believe them as a matter of faith: they ask us to look at the data and decide for ourselves. They also admit when they don't know, or when they are found to be wrong. I don't trust anyone who claims to be infallible.
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17. JoeT at 14:17 PM on 19 November, 2012
    Thanks to all who responded. It's much clearer now what's going on. Also, to Doug H, I have to say it was enormously disappointing to see Harrison Schmitt (they misspelled his name in the credits, but correctly when he was speaking) as the representative of the Heartland Institute. Schmitt of course is one of last people --- and the only scientist -- to walk on the moon. Years ago, we had a nice conversation about mining He3 on the moon as fuel for a fusion reactor. Now it's just sad to see him this way.
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18. Bert from Eltham at 14:45 PM on 19 November, 2012
    My dear old dad told me years ago, 'always remember son it is the incorruptible man who has the highest price! The rest of us settle for what we can get. I urge you to hold out for the best price! That way you remain pure! Bert
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19. chriskoz at 22:47 PM on 19 November, 2012
    JoeT@17, Indeed, I'm just disgusted by learning from wikipeadia about Schmitt saying in 2009 Heartland conference that "climate change is a stalking horse for Nazism". He is very low on the ladder of denial, lower than anyone I know of, who holds a climate-related degree (geology in this case). This is OT, but I kinda wonder if being an astronaut increases the predisposition for denialism: we have a recent sample of active denialism by retired NASA astronauts and now we have Schmitt from that group, who has virtually hit the bottom of denial... What would a cognitive psychologist say about it?
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20. gws at 00:37 AM on 20 November, 2012
    correction the last arctic stratospheric ozone loss episode occurred not 2011/2012 as I said above, but spring 2011 Nature article here
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