Comments 1 to 19:

1. DeWitt Payne at 11:41 AM on 19 December, 2011
   There has certainly been a shift in the seasonal behavior of NH sea ice area. The new seasonal pattern that appears to have been established in 2007 is significantly different from that observed by satellite from 1979-2006 and appears to be reasonably stable, at least through 2011. That's why the anomaly data for NH sea ice area at Cryosphere Today calculated using the 1979-2008 average, for example, shows big spikes upward and downward starting in 2007.
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2. muoncounter at 11:49 AM on 19 December, 2011
   If you are talking about this Cryosphere Today graph, aren't the 'big spikes upward and downward' the seasonal variation? And isn't the very-well defined trend down?
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3. Tom Curtis at 12:16 PM on 19 December, 2011
   Muoncounter @2, the fluctuations are largely due to seasonal variations. However, between 1997 and 2007 the difference between the winter and summer anomalies was around 1 million square kilometers. Post 2007, it is closer to 1.75 million square kilometers. That is partly because the winter anomaly has not declined since 2007, while the summer anomaly continues its death spiral. However, contrary to DeWitt Payne, I think 5 years is two short an interval to suggest that this is a new seasonal pattern rather than just noise. On the other hand, at some stage in a continuing death spiral of summer ice, we would expect this pattern to emerge. In the near term limit, winter ice will still form extensively, while the summer ice will shrink to near zero. In the medium term we would then expect the winter ice to gradually shrink in area as the summer water temperatures start to climb in the absence of ice. Consequently the pattern over the last few years may be this pattern (continuing winter ice, and low or no summer ice) starting to assert itself. It is just too early to say IMO.
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4. muoncounter at 13:03 PM on 19 December, 2011
   TomC: That's something we discussed on prior Arctic ice threads - summer minimum extent is dropping like a rock, winter maximum extent less so. That has to translate to a more rapid or an extended melt season. Consistent with the results described by Jeff Masters here. As Earth's climate has warmed over the past 30 years, the Northern Hemisphere has seen a dramatic drop in the amount of snow cover in spring (April, May, and June.) Spring is coming earlier by an average of three days per decade, and the earlier arrival of spring has significantly reduced the amount of snow on the ground in May. Less snow on the ground means the land surface can heat up more readily, and May temperatures in Arctic have increased significantly over the past 30 years. Consistent, too, with Arctic amplification and feedback due to the increased area of exposed sea water for more of the year. BTW, my questions in #2 were rhetorical.
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5. jyyh at 16:14 PM on 19 December, 2011
   Let's see if that shows:

   

   The X-axis is the fraction of the year. It looks like the Arctic Ice amount is affected little by ENSO events, if at all, so Atlantic heat transport and general atmospheric warming would be the largest melters of the Arctic Ice.
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6. jyyh at 16:16 PM on 19 December, 2011
   that's the running average of Ice up north. don't know where that part of the text went.
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7. jyyh at 17:49 PM on 19 December, 2011
   As the average winter max is somewhere at 13-14 Mkm2, extrapolating the running average graph to somewhere between 6.5-7 Mkm2 would mean the earliest year of ice free summer (at least in sept) up there. Just guessing here, of course, a major volcano would likely delay that for a couple of years, and an enormous eruption somewhat longer still. http://www.wunderground.com/blog/JeffMasters/comment.html?entrynum=2003# discusses of the meteorological effects of ice free arctic.
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8. CBDunkerson at 23:16 PM on 19 December, 2011
   I don't think there is any chance of the Arctic 'stabilizing' to a 'new normal' any time soon. Even if greenhouse gas levels magically leveled off we'd continue to see continued ice loss and related changes for decades, if not centuries, to come. I recall a study a year or two ago which concluded that if Arctic temperatures/conditions returned to 'normal' the sea ice could recover and therefor there was no 'death spiral'... which never made much sense to me because it should be obvious by now that there isn't going to be any 'return to normal'. That 'normal' is gone. The conditions which allowed it no longer exist.
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9. Daniel Bailey at 00:04 AM on 20 December, 2011
   CBD, I believe you refer to the Tietsche et al 2011 paper. Note that a limitation of Tietsche is that the presumption is that stable CO2 concentrations have been achieved and equilibria with temps then reached. We are far, far from those conditions. Tietsche thus remains an academic construct.
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10. cRR Kampen at 06:32 AM on 20 December, 2011
    Given the Arctic ice volume trend, it appears the ice cannot exist other than purely seasonal at present climate conditions already. I disagree with the title "Arctic settles into new phase" entirely. There is no 'settlement' - yet.
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    Moderator Response: [John Hartz] The headline was written by NOAA's press office.
11. funglestrumpet at 06:51 AM on 20 December, 2011
    This all fits with the report of giant (one kilometer dia) methane plumes rising to the surface in the Artic that have been discovered by Russian scientists. That's the trouble with tipping points, they slip by so silently - a bit like crossing the event horizon of a large black hole, you don't realise until it's too late. (I have never put a hyperlink in before and after reading in the tips section that if I get it wrong, it will screw up the page, I won't try this time either. The address off my computer is: http://news.yahoo.com/blogs/sideshow/giant-plumes-methane-bubbling-surface-arctic-ocean-163804179.html. I imagine that there is a more academic report somewhere.)
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12. cRR Kampen at 07:49 AM on 20 December, 2011
    #11, the methane thing in the Arctic becomes the single and by far most alarming change in existence re AGW - if we see methane concentrations rise sharply on a global scale in the next couple of years. Personally, I fear for the absolute worst.
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13. John Hartz at 08:05 AM on 20 December, 2011
    cRR Kampen: If you have not already done so, you may wish to peruse “As Permafrost Thaws, Scientists Study the Risks” published in the New York Times on This in-depth article portrays in words and in photos what's happening to the permafrost in the Arctic. It is part of the NY Times' Temperature Rising series. To access “As Permafrost Thaws, Scientists Study the Risks”, click here.
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14. John Hartz at 08:31 AM on 20 December, 2011
    funglestrumpet; The paper you are referring to is: "Recent changes in shelf hydrography in the Siberian Arctic: Potential for subsea permafrost instability" JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 116, C10027, 10 PP., 2011 doi:10.1029/2011JC007218 The "Key Points" of the paper: •Our data provide evidence of drastic bottom layer heating over the coastal zone •We attribute this warming to changes in the Arctic atmosphere •Recent climate change cannot produce an immediate response in subsea permafrost The Abstract and additional information about this paper is available here.
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15. John Hartz at 08:43 AM on 20 December, 2011
    The findings of "Recent changes in shelf hydrography in the Siberian Arctic: Potential for subsea permafrost instability" cited in my previous post are incorporated into a new SkS article, "Abrupt Climate Change - Causes" by Agnostic that will be posted in the near future.
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16. ManOfFireAndLight at 08:55 AM on 20 December, 2011
    @John Hartz Hopefully you can find out a bit more (including some actual data) about this: http://www.independent.co.uk/news/science/methane-discovery-stokes-new-global-warming-fears-shock-as-retreat-of-arctic-releases-greenhouse-gas-6276278.html
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17. John Hartz at 10:29 AM on 20 December, 2011
    ManOfFireAndLight: The Independent(UK)article that you have provided a URL for is based on the paper "Recent changes in shelf hydrography in the Siberian Arctic: Potential for subsea permafrost instability" which I cited in my post #14.
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18. barry1487 at 16:08 PM on 20 December, 2011
    Re the first few comments on seasonal behaviour of ice cover: it has seemed to me that the closer track of anomalies to the changing seasons in recent times is mostly a result of thinner ice responding more quickly. If so, this should be more evident in the melt season than during recovery, and I think that can be seen in the CT graphic.
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19. cRR Kampen at 07:13 AM on 21 December, 2011
    John et al, thank you for the additional lecture. Btw I noticed the authorship of the title but only responded to the title's content. #18, that's what is sharpening the annual cycle of anomalies. Catastrophe theory (the mathematics/physics interpretation) is imo a useful concept. E.g. around a threshold average thickness below which, in summertime, ice cover breaks up and melts vastly more quickly. Positive feedback like open sea area, menacing the protective fogs and low stratus over the pack.
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