>"On the comments regarding a protective arm of MYI towards the Pacific: I don't get it." Agreed that inflow generally isn't at the surface but what has this to do with it? Surely surface can and does circulate more clockwise than anti-clockwise with Beaufort Gyre regardless of what inflow waters are doing at below surface level. Beaufort melts out but by end of January: http://www.aari.ru/resources/d0015/arctic/gif.en/2012/20120131.GIF vs http://www.aari.ru/resources/d0015/arctic/gif.en/2013/20130129.GIF However, I don't think that is doing recent movement well: http://www7320.nrlssc.navy.mil/hycomARC/navo/arcticictnnowcast.gif is more like it showing lots of thicker ice off Banks Island but not much north of West Alaska/Bering Strait.

Foot soldiers? Buckets and spades? We need to boost our economies with the production of laminated tin foil or something similar. Install with South facing slats so most snow falls through it but sunlight gets reflected .... Also apply to roof space to reflect back to space (or towards nearby solar panels). In fact why start with Greenland, start with dark areas eg above black tarmac roads ... ;)

>"(although, contrary to the other graphs, it doesn't seem to be updated all the way to the end of the month):" If you look at Jan then it is clear the marker is at the middle of the month (and it is the same with their volume graph). So end of April is the midpoint between April and May markers and both graphs therefore appear to run to April 30.

http://www.aari.ru/resources/d0015/arctic/gif.en/2013/20130423.GIF still doesn't show much old thick ice in Beaufort. I think this is wrong with the other sources all agreeing that a big area of old thick ice has moved towards Beaufort. Early in the season it seemed there was very little thick ice there. Now it is looking like a thicker swathe than usual at least on the eastern side. Alaskan edge has little. If that keeps drifting that way, this melt season might avoid records but leave the ice in a terrible state for 2014.

http://www.bbc.co.uk/news/science-environment-22167675 reports “The European Parliament has rejected a plan to rescue the EU’s ailing carbon trading scheme. Members narrowly voted against a so-called “backloading” proposal that would have cut the huge surplus of allowances currently being traded. Because of this excess, the price of carbon on the EU Emissions Trading Scheme (ETS) has plunged to less than 5 euros a tonne. But opponents won the day by arguing the plan would push up energy costs. The price of carbon once stood at 32 euros per tonne.” That article has now been extended. Where now? Doubt the committee will propose a carbon tax instead.

Definitely wasn't 'Connelly' ;) . Yes, Annan and Hargreaves were saying aim for/test data being statistically indistinguishable from ensemble members. Dr Connolley was saying there is a big variation in quality between the models so you need to discard the rubbish ones based on some objective measure of whether the models are any good.

I think Chris Reynolds is using Excel to generate his images. Not sure whether there is any good way of using Excel to generate undithered image. Each pixel has a different area so it wouldn't be too difficult to calculate areas and volumes much better from Excel than by counting pixels off an image.

March Volumes from cell thicknesses: 2013 2012 20.73 20.69 This is presumably average for March, so very similar and could be less at end of March based on daily numbers. A quick analysis: Volume in excess of 0.5m thick in any cell 2013 2012 14.1 14.0 Very similar Volume in excess of 1m in any cell 2013 2012 8.4 8.6 Volume in excess of 1.5m in any cell 2013 2012 3.9 4.3 Volume in excess of 2m in any cell 2013 2012 1.4 1.6 Volume in excess of 1.67m in any cell 2013 2012 2.8 3.25 Volume got down to 3.26 last year equivalent of melting 1.67m from the March thickness of each cell. Not sure how good a method it is to apply that to leave 2013 minimum volume at 2.8 K Km^3. Anyway, the trend of less ice volume in the thickest cells continues.

http://farm9.staticflickr.com/8120/8626552241_5dc1304294_b.jpg Trend has moved day of maximum from 113 to 105. So early/mid May would seem rather late. About day 100 (10 April) would seem an appropriate day if you expect it to be earlier than the trend. This would probably mean little increase from 21.612 on day 90. Gain day 60 to 70 = 0.761 Gain day 70 to 80 = 0.451 Gain day 80 to 90 = 0.455 2012 (late max) had 0.858 0.497 0.498 2011 (early max) had 0.602 0.554 0.431 Probably not sensible to read too much into this but 0.455 of last 10 days is nearer the 0.431 of 2011 which had an early max.

>"I wondered about this negative feedback a long time ago but can't remember anyone coming up with an answer. But I assume that it won't change the imbalance of the heat budget." Reducing the thickness of the ice allows more heat out particularly in Autumn so it does alter the heat budget. So far the heat budget does not seem to have closed, more like it has got worse. The difference in heat flow between 1 cm thick ice and 21 cm thick ice is much greater than between 21 cm and 41 cm. So the negative feedback gets stronger as the ice gets thinner and should be able to do more to close the heat imbalance. Removing sea ice from models causes ice to recover in 2 years. Should we expect similar in the opposite direction? i.e. heat imbalance should thin the ice and allow more heat out but how long should this take balance the heat budget? How does that compare with other changes to heat budget like: -Change in GHG levels -More FYI in place of MYI allowing more heat absorption -thinner ice having lower albedo -temperature rises causing more heat emission

David Vun Kannon asked "what does "essentially ice free" mean in terms of volume?" CT area in million km^2 at minimum divided by average thickness in m at minimum (PIOMAS Volume/CT area) seems to be staying roughly constant at about 1.72. So if area=1M km^2 and the rough constant of 1.72 remains at 1.72 then CT area/t = 1.72 so average thickness(t) = 1/1.72 = 0.58 m So volume = 1M Km^2 * 0.58 m = 580 Km^3 Note that 1M Km^2 area is rather more ice at minimum than if Extent = 1M Km^2 which is perhaps a more usual definition of 'essentially ice free'. (I allowed for this in my calculation on the forum of using 21 K Km^3 volume reduction needed from 31 March rather than 21.612 K Km^3.)

>"interesting [Wipneus fram export] graph. It looks like April-June has really taken off. Why would this be the case? I am no expert but I would suggest: 1. Anomalous high pressure over Greenland observed since 2007. For causes of this I would suggest looking at: a) Dr Jennifer Francis' work on meandering jet streams and blocking events and other related work. b) Tedesco et al 2012 "identify persistent anticyclonic conditions over Greenland associated with anomalies in the North Atlantic Oscillation (NAO)" 2. Lower ice concentration allows faster movement of ice more than compensating for any reduced thickness. 3. Why AMJ? Perhaps more breaking up of ice in this period allowing the persistent anomalous high pressure to have more effect? I am really only guessing here. I would expect that there could well be more effects than I have mentioned.

Wipneus Fram export graph is at https://sites.google.com/site/arctischepinguin/home/piomas/grf/fram.png

>"Maybe it's just me, but March 2013 looks a lot like May 2012." 48 day difference you picked out looks about right to me, good comparison. Definitely less snow on the lower slopes now than 48 days later last year. More advanced in May for some sea ice but similar for others areas. It has been warmer than normal in this region and if we picked Kara which has been colder, the sea ice looks more solid. Still 48 days ahead is a lot!

Sorry Jim 2011 increased 382k from the next day's data (12.713 to 13.095).

Area now down to 13.455 so looks much more likely to be past maximum. Following pattern of any year does not reach a new max. However, following pattern of 2011 from either of next 2 days would do it.

If area follows pattern of a random year movements then 31 out of 34 and all of the last 15 years suggest max has passed. Not quite sure about how expected weather should change that, but it does seem highly likely that max has passed. Perhaps still a very slight chance but if you don't call it until area has fallen by 500k then perhaps you look silly for waiting so long before calling it. So perhaps it is better to call it with a '?' added?

Villabolo, I am not an expert so this may need correction but I would suggest no. Winds and current will move the ice pack. This would generally be expected to keep the pack together held up against CAA. But it might not happen that way. If the pack is moved away from land then certainly some pieces will end up clear of the pack and melt but I would still expect the pack to mostly stay together. The pack edge usually stays fairly distinct. Odd pieces with a lot of ocean around tend to melt quite quickly due to albedo of ocean absorbing lots of heat. Also pieces will break off which are deeper than they are across so that they rotate and take up more surface area. This can fill in some of the area that melts out (though again it will tend to be thinner and therefore be liable to melt out earlier).

>"the melting was substantially stronger than the freeze, in every single year, without any exceptions." Um, maybe I misunderstand but you have realised that the volume max is in April and the volume min is in September so 5 months of melt and 7 months of freeze. Therefore if the volume is anywhere close to being in balance, the melt has to be lot stronger than the freeze. In top right graph of https://sites.google.com/site/arcticseaicegraphs/longterm I count 8 occasions where the volume gain exceeded volume lost. Probably/possibly that is getting less frequent.

I did get a couple of answers back in Oct 12 from one of the CPDN climate scientists, Friederike Otto: http://climateprediction.net/board/viewtopic.php?f=36&t=5927&start=191

>"if you have a model that can't replicate" Yes there is certainly an issue that isn't completely solved by thinner ice rather than area changes. >"long-term Arctic amplification" I don't know whether to dismiss this as not hugely important at the timeframe I am thinking about. (Long time ago, uncertain forcings etc....) I see Dr Roy Spencer on his blog saying tropical regions warm 3 times too fast. That would really be a problematic tuning problem if that has to be done to get the global temperature series about right the tropics warm too fast and the poles too slowly. Shouldn't really believe it is that bad a problem, should I? Yes, I would also certainly like to see such feedback from a modeler. (Maybe one day I will figure out how to get modelers to come to the CPDN forum.)

>"if the models can't first get the sea ice loss right it doesn't seem they would be very reliable in projecting the aftermath." If you reduced the sea ice area without changing water temperatures, I can imagine that introducing artifacts and it might be difficult to tell what weather was caused by the artifacts and what by the lack of sea ice in summer. So rather than doing that I was thinking it might be better to reduce the thicknesses of the ice to get the volume down to an amount that can melt out. Some tweaking of the thickness amounts should allow some sort of reasonable melt out pattern to occur. It is then a case of running a model with atmosphere and top ocean layer (slab ocean?) allowed to vary but with those sea ice extents and thicknesses prescribed. This atmosphere model would have to be done many times over with slight variations in initial conditions to get climate risk information. The impacts we are interested in, floods and droughts, come from atmospheric weather. Is this possible without introducing major artifacts? This would probably only cover a few years after sea ice disappears for the first time. Then you would make the ice thinner again to melt out faster in a full GCM to provide new prescribed ice extent and thickness data for the atmosphere model to cover a later as yet unspecified time period merely relating to when the ice cover disappears at that speed. Cannot get a huge amount of advance warning like this but I suggest some is better than none. It may not be reliable to go far out in time like this but can't the atmosphere model produce something like an indicator regarding flood and drought risk? Such an atmosphere model would not be trying to get the sea ice right (it is just given something we think is reasonable to avoid artifacts) and we are only hoping for it to give reasonable indicator of atmospheric effects.

Not sure if it is worth posting http://lance-modis.eosdis.nasa.gov/imagery/subsets/?mosaic=Arctic.2013057.terra.4km There are no dates on the video. If you compare to http://lance-modis.eosdis.nasa.gov/imagery/subsets/?mosaic=Arctic.2012087.terra.4km and http://lance-modis.eosdis.nasa.gov/imagery/subsets/?mosaic=Arctic.2012097.terra.4km pointing out that these pictures are 30 and 40 days later during 2012. 51 days seems a little over the top to me. Perhaps 40 days?

Bob you seem to arrive at 36000 acres to house 40% of 4143TWh. Wikipedia comes up with a 9000 acre wind farm: "The Alta Wind Energy Center in California is the country's largest wind farm at 1020 megawatt (MW) capacity.[8] It consists of 342 wind turbines manufactured by General Electric, and Vestas. In 2012 it surpassed the Roscoe Wind Farm in Texas when additional phases of the project were completed. The project is located in Kern county and covers a 9,000-acre (36 km2) area.[25] [26]" 36000 acres is 4 times 9000 acres. 4* 1020MW = 4080 MW. That seems some way short of 1600TW. Maybe that isn't the most efficient wind turbines or most efficient use of land area. Still a factor of 400 takes some making up. I could easily have got some figures/understanding wrong but with this just being one wind farm and US wind production being just 5%, I think you might be being a little too optimistic. May well still be doable in countries like US with lots of space/arid land. Planning battles in densely populated countries like UK seem particularly acute.

Thanks for the comments. Interesting variety. >"Cumulative ‘winter power’ is still on the weak side." How should temperatures be weighted to arrive at 'winter power'? Early in the freeze season, the ice thickness is well below equilibrium and there is rapid growth but the final equilibrium thickness depends on temperatures in Feb/March/April? Does that mean negligible weight should be attached to temperatures in Jan and prior? >"They[cracks] do not seem to be anomalies..." Are you saying it isn't a one off single crack or are you saying the cracking is normal having occurred in previous years? What effects do you expect the cracks to have? (Maybe that is just restating John's interesting question.) "Moisture is there" having risen would suggest volume shouldn't be catching up as it appears to have done in Jan. So first reaction is perhaps the data prefers moisture isn't there due to NAO. However perhaps the volume is catching up due to cracks and water vapour is not playing much of a role. Probably lots more data that could change interpretation of what is happening.