" It could mean that either winter weather still has enough of a punch to restore the ice pack " I'd been wondering about that. With the lines in graphs 4 and 5 running parallel through the freezing season it suggests to me that the ice can still put on thickness at the same rate even going back to the 1990's. Well that's how I'm understanding it, I could easily be wrong. Would that be right?

Maybe this paper is describing what you think might come to pass http://www.seas.harvard.edu/climate/seminars/pdfs/Asplin2012.pdf

Totally OT but another lovely arctic image. A really deep arch has formed in the Nares Strait http://ocean.dmi.dk/arctic/images/MODIS/Kane/20130407AQUA.jpg

I've got a question about the Atlantic side of the ice pack. There's been a near straight line stretching from Sevemaya Zemlya Islands (??) to Greenland. The CT comparison tool shows a slower, steadier retreat in his region compared to the recent big changes on the other side. It still looks as though melting in that region is greater than previous years though. Any thoughts on why this is? Or what effect it might have on the final minimum extent?

It's early days but is it possible that the decrease in extent is beginning it's slowdown to the year minimum? http://arctic.atmos.uiuc.edu/cryosphere/arctic.sea.ice.interactive.html I think it's just spotting patterns and happenstance. It will likely accelerate again. It would make for a truly weird season if it did though.

Chris, The same effect occurs using my eyeballed volume numbers. In 2011 ice volume lost in the second half of the season is 8000km3 (18-10). While in 2003 the second half of the season lost 10,000km3 (17-7). Whatever mechanism is responsible for the larger ice melt in the first half of the year is being moderated later in the melt season or on the more central ice. Something of a brake on runaway positive feedbacks possibly?

Following on from AmbiValents thoughts maybe it would be useful to look at the volume of ice that has melted or been export each year. I'll contribute some rounded off numbers from eyeballing Wipneus' POIMAS graphs. https://sites.google.com/site/arctischepinguin/home/piomas All numbers are in 1000 km cubed of ice lost Max (apr) to now (Jul) 2012 11 2011 10 2010 11 2009 9 2008 8 2007 8.5 2006 7 2005 7.5 2004 6 2003 7 2002 7 Max (apr) to Min (sept) 2012 ?? 2011 18 2010 19 2009 18 2008 18 2007 17.5 2006 16 2005 17 2004 16 2003 17 2002 16.5 The volume lost each year is increasing but no obvious sudden increase in loss in any one particular year. Maybe somebody can provide the accurate numbers.

Great stuff. You can go further south in the Atlantic and get confirmation of these trends from the 1990's onwards. For example the Ellett Line covers a region of the Atlantic from Scotland to Rockall where about half the North Atlantic water crossover into the Nordic Seas. http://www.noc.soton.ac.uk/obe/PROJECTS/EEL/latestresults.php That time series has been extended back further to 1948 by Met office shipping measurements to put the post 1990 changes in context. http://icesjms.oxfordjournals.org/content/early/2011/12/13/icesjms.fsr185.short The above is paywalled but the conclusion reads. "The upper waters of the Rockall Trough have undergone a series of significant interdecadal changes over the past 60 years which are summarized below. (i) A relatively warm period existed between 1948 and 1972, with winter surface temperatures of 9.68C. (ii) Subsequently, there was a cooler period (9.28C, uSST) until about 1995. (iii) The start of this cooler period (1972)coincided with the advent of the Great Salinity Anomaly, which itself lasted to about 1982 (minimum S800 ¼ 35.27). (iv) There was a second, less intense freshening in the early 1990s (minimum S800 ¼ 35.30). (v) A steady increase in u800 and S800 (to 108C and 35.41) has persisted from 1995 to almost the present day. This phenomenon, which is reflected throughout the northern North Atlantic, is linked to a changing balance in Subpolar and Subtropical Gyre waters. (vi) Finally, there has been a steady decline in phosphate concentrations since 1996 (from 0.8 to 0.6 mM) that seems to be linked to the increase in Subtropical Gyre water. Most of these changes are linked to the movement and exchange of water masses in the northern North Atlantic, and it is not possible to say whether the upward trends in heat and salinity of the 1990s and the 2000s in the Rockall Trough will restart following their recent slowdown and partial reversal. Further, it is uncertain whether the changes of the past 15 years lie outside the range of natural variability for the past 60 years or whether they can be attributed to anthropogenic warming." It's true that it's not impossible (in part) for the warming to come from the increase heat content but it's also not impossible (in part) to come from dynamical changes highlighted here. I guess the billion dollar question is the relative magnitudes of the 'in parts'.

With the Nares Ice bridge still holding, just, and forming around the 10th of december. http://ocean.dmi.dk/arctic/images/MODIS/Kane/201112100040.ASAR.jpg I make that about 197 days of stoppage and counting. That put's it above the average, 188 days, for recent years according to this great paper. http://rkwok.jpl.nasa.gov/publications/Kwok.2010.GRL.pdf But it looks like the bridge would have to last until the start of July to match the norm for break-up in recent years. The unusual early formation date is what seems to making the stoppage days look good.

It is intriguing to think about the difference between the Bering Sea and the Barentz Sea beyond just this year. This is maybe not the best way to display long term trends, there may be seasonal trend and so on, but these two satellite era records from CT of the two seas illustrate the striking difference. http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/region.all.anom.region.2.jpg http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/region.all.anom.region.6.jpg Nevens description of positive feedback loops that go on and on don't really get to the heart of it. Sure you could have annual variability that put a stop to this in the Bering Sea but it appears to be stalled for the whole 30 years. My bet is like Mike with the avection of heat in Atlantic waters into the Arctic as being the signficant driver here. This eventually makes it all the way to the Chukchi Sea through currents in the Arctic but the Bering Sea is cut off from this process. But I'm below novice on the physical processes of the arctic, I'm ready to be educated.

Thinking about it I guess that could just be snow melt revealing less homogeneous ice underneath??

I'd been watching Nares Ice bridge as well expect I hadn't looked for a week or two. Things look like they;ve changed around the bridge a fair bit. It's been like this since March http://ocean.dmi.dk/arctic/images/MODIS/Kane/20120524TERR.jpg Then over the course of a week it turns into this http://ocean.dmi.dk/arctic/images/MODIS/Kane/20120612TERR.jpg (more of that blue ice)

Kevin McKinney, "But has NH warming actually stopped since 2000? There are statistically non-significant *warming* trends by most measures." Specifically I said warming had stopped in 0-60oN. Honestly it has, check all the data sets on KNMI Climate Explorer. I'm happy to agree with a non-significant warming trend for the NH but that includes the Arctic. Your point about ocean heat content and Atlantic advection is important so I checked them. Here is the NH (0-60 degree N) OHC since 1980 http://i47.tinypic.com/50l8xw.png And here is a plot of changes in temp of Atlantic Waters thru' Fram Strait. http://i48.tinypic.com/26114i1.png It's a screen grab from this 2012 paper http://icesjms.oxfordjournals.org/content/early/2012/04/18/icesjms.fss056.short?rss=1 But I'd still suggest that since 2007 (and most likely a couple of years before) we aren't seeing the same increases in energy being advected into the Arctic than prior to that and ultimately this is the engine that's going to drive arctic warming and melting. Interesting the Beszczynska-Moller paper points out there are time lags asociated with the energy entering the Arctic from the Atlantic so the idea of melting in the pipeline from the warm water pulse in 2006 looks likely. I guess what I was objecting too was a discussion that focuses solely on internal arctic process like sea-ice feedbacks, sea ice condition etc. It seemed to me it can start to look like it's describing runaway positive feedbacks rather than just positive feedbacks. If you take Neven's analogy of loaded dice then the loading just doesn't happen once it needs to be further loaded to achieve the next state. I'm just pointing out that loading has slowed (I actually think it's stopped) since the 2007 low. But maybe the dice have already been loaded enough to melt all the ice by internal feedbacks. I'm happy to be convinced on that argument. "Finally, how likely is a serious 'cold snap?'" I was really trying to avoid predicting were sub-arctic NH temps will go in the near future. But this discussion seems to be about were sea-ice will go in the near term (e.g. extrapolation of trends over the next decade or so) and I thought it was important to point out that the engine driving the whole process had seriously slowed compared to the galloping pace in the 1980's and 1990's.

In the spirit of 'indications' and 'suggestions'. I wanted to lay out a just so story based on physical processes and maybe people can tell me where I'm going wrong. So to start, simply speaking, the arctic warms due to extra energy being transported north from a warming sub-polar NH. Positive feedback processes work on top of this in the Arctic to amplify this warming. A good place to start is to look at what is happening in tropical and mid-latitude NH. If you take a look at 0-60 degrees N using any data set on KNMI climate explorer you can see a warming NH since late 1970's but that warming has paused since the turn of the century. If you look at the arctic (60-90oN) amplified warming since the late 1970's is clear. It's a little harder to say what's happening more recently due to the much larger inter-annual swings and the short time period but it looks as if warming has also slowed since about 2005. Somebody earlier pointed out that model studies suggest that some ice processes act on a very quick time scale. The example went something like if you remove all the ice in a model that the system quickly forgets this pertubation in a few years. Sorry I can't find who or where the point was made. That suggests to me that important ice feedback processes may be happening on a fairly quick time scale, for the sake of my just so story lets say 5 years. This also looks true when you consider the temperature profile of the arctic over the whole 20th cenury. It seems to very quickly turn around, think about the early/mid 20th century warming of the arctic. So here's the just so story. A warming NH sends more energy into the arctic this stops when the NH stops warming around the turn of the century. The Arctic continues to warm due to positive ice feedbacks until 2005 (or so). The Arctic is now in a new 'equilibrium' WRT NH temperature as a whole. We are in a phase were year to year changes in the arctic ice are in response to weather. Given that 2007 was an extreme weather year in the arctic this could represent a low for the present regime. As caveats I could say that it's very possible that there is still more warming of the arctic 'in the pipeline' from feedbacks that could melt more ice. But in order to be sure that arctic ice is going to continue on it's downward trajectory it seems that we need to see a resumption of warming in the lower NH. At the very least it seems like what is happening outside the arctic has been neglected so far in this discussion and I'd be interested in knowing what importance people think that has? (Apologies if this is actually uninformed BS ;) )

Just for clarification is the term "self-acceleration" used in this paper the same thing as 'polar amplification'. Thanks

Thanks Peter Ellis, very interesting. And I guess compared with a few submarine tracks, a few dozen aircraft flyovers and a handful of in situ ice thickness measurements every year, the Cryosat data is orders of magnitude higher. It seems important when one is criticizing the Cryosat to keep in mind what the alternative is. Thanks for the live blogging Neven.

Sorry another question. I see "natural variation" talked about a lot in climate blogs and I was wondering what people think that means in respect to arctic sea ice. Are we just talking about seasonal/annual variations that might move metrics away from a long term trajectory for a year or so, things like AO. Or are there 'regime changes' or dare I say 'oscillations' that may alter the rate of change (or even the sign) for a decade or more? I can imagine internal changes promoting 'regime changes' but I'm curious if people consider an external processes that might work on these time scales?

I have a question. If the Bering Strait (BS) remains iced up longer than usual does that have an impact on how the melt/export season develops? I don't hear anything about ice being exported thru' the BS but does it have any effect on how ice is transported around the basin?

Heraclitus, My understanding is that it's very difficult to predict Sept minimum this early in the season. There are many dynamical processes that contribute to ice loss that can't be predicted so far in advance. If you're interested in prediction and have an afternoon to waste reading up on it then this site might be good. They've been involved in minima prediction for a few years and get input from many research groups. http://www.arcus.org/search/seaiceoutlook/2011/summary

Thanks Chris I'm glad you carried on with the answer, very interesting. I've wondered what would the ice thickness data look like without the conditions that caused the big clearout of ice in 2007. For example would it be possible to run an experiment where the 2007 data is replaced by a more neutral set of data then go back to the real world data in 2008 onwards?

ignore the above I mis-understood the website Thanks

Chris Reynolds, You seem to know alot about PIOMAS and ice volume so I'll direct this to you. The PIOMAS website (and the kwok paper) states that the model assimilates ice thickness observations. Presumably this data contributes in some way to the ultimate output of the model. The Kwok paper you link attempts to validate the model output by comparing it to ice thickness observations. To my mind there seems to be a circular process going on here. Obs are used to constrain the model and then later used to validate it. But it could be argued that they have only validated a very tiny part of the model output (the part that coincides with an obs) while the vast majority of the output from the model is unvalidated. This wouldn't be a problem if it can be assumed that this tiny part is no different to the rest of the output from the model. But this isn't necessarily true because this also happens to be the part of the output that is most likely affected by the assimilation of obs data points. This is confusing me somewhat but I hope I've got across the problem as I see it.

Neven, "..... but an even higher and later maximum, and I'm shutting down the blog" The CT interactive graph (http://arctic.atmos.uiuc.edu/cryosphere/arctic.sea.ice.interactive.html) shows 1982, 1999, 2010 and 2011 all show resurgences in ice area even after day 90 (as late as day 99) which come very close to beating the earlier maximum. You could be risking your blog over this.

So this is my problem. You have a plausible hypothesis as outlined in Budikova 2008 and then you have a couple of years that show the conditions that would confirm the hypothesis and then you get papers such as Overland 2011 that starts "Recent Arctic changes are likely due to coupled Arctic amplification mechanisms with increased linkage between Arctic climate and sub-Arctic weather." Which in their words was based on "Winter 2009/10 and December 2010". There seems to be some horrible urge to jump to conclusions as quickly as possible. Can somebody tell me why this won't go the same way as 'arctic death spirals' based on hasty conclusion drawn after the 2007 minimum?

The warm tongue is fascinating. On the numbers in the final list they look big but it looks like the natural variability in this region is fairly amazing. Take just the first site you list, Longyearbyen, Svalbard. It only has max/min data starting 1976 but it has recorded temperature range for March of >50oC (+6 to -42). I hope that put's some perspective on things. http://www.yr.no/place/Norway/Svalbard/Longyearbyen/climate.month03.html