Daniel, Can you please point out where I talked about subsea clathrates? To the best of my (admittedly limited) knowledge, the term "clathrates" is used to describe a form of "cage compound" in which some other compound can be trapped. In the context of global warming, the term usually refers to methane clathrates, in which methane is trapped within a water ice structure. Under the sea, this requires considerable pressure to remain viable, but, in permafrost, the low temperature is all that is needed to retain its structural integrity. You seem to be engaged in some kind of crusade against the Arctic Methane Emergency Group, of which I am not a proponent. Let's just summarise shall we? In response to Susan's comment, I wondered aloud if the temperatures involved in the wildfires may have caused some clathrate destabilisation in the surrounding permafrost area. By way of response, you appear to have tried to take the piss, by intimating that clathrates only occur in sub sea regions. When I pointed out that clathrates can and do occur in permafrost, you have simply gone on a rant. It would therefore appear that if anyone dares to use the word "clathrate", you treat this as some form of red rag to a bull. Further discussion would therefore appear to be a total waste of time. PS Feel free to have the last word.

For quite a few years, it has been my understanding that clathrates are contained within permafrost as well as in the ocean. As a starting point, might I suggest that you have a quick look at... https://en.wikipedia.org/wiki/Arctic_methane_emissions or https://en.wikipedia.org/wiki/Methane_clathrate#Continental In the second of those links, there is a section which reads... "In their Correspondence in the September 2013 Nature Geoscience journal, Vonk and Gustafsson cautioned that the most probable mechanism to strengthen global warming is large-scale thawing of Arctic permafrost which will release methane clathrate into the atmosphere.[47] While performing research in July in plumes in the East Siberian Arctic Ocean, Gustafsson and Vonk were surprised by the high concentration of methane.[48] Perhaps you could also please indicate where I suggested that clathrates acted as a causal agent in these wildfires. My query related as to whether or not there had been any destabilisation of the permafrost carbon deposits as a consequence of the wildfires.

Susan, That "Modis active wildfire pixel counter" graph was a tad on the worrying side. This year was more than double the previous highest, and about 6-7 times higher than the 2002-2016 mean value. Wonder if there is any significant clathrate contribution?

@ Neil T & Hans G I've just posted a little chart pertaining to global sea ice extent on the ASIF's 2017 melting season thread. (See #3562) http://forum.arctic-sea-ice.net/index.php/topic,1834.3550.html Notice anything about the periodicity with which the humps seem to appear?

Sam said... "The arctic is already in full meltdown headed for catastrophic melt. That much is clear for anyone to see looking at the data. We do not need more CO2 for that. Yet we will have much more released before we are done. The complete loss of the artic ice and disruption of both the atmospheric and the oceanic circulation is a done deal." On that depressing theme, a group of scientists from the Max Plank Institute of Meteorology published a paper in the Journal of the American Meteorological Society last year. Its title rather says it all: "On the Potential for Abrupt Arctic Winter Sea Ice Loss". http://journals.ametsoc.org/doi/full/10.1175/JCLI-D-15-0466.1 N.B. The CO2 trajectory assumed in said paper is RCP8.5 There is some discussion of this in the "Year-round ice-free Arctic" thread on the ASIF.

Ah, but you have forgotten my weasel-words caveat "... if around today, he might have ...". I was working in Amsterdam at the time of the last (or at least, the most recent) Elfstedentocht, and remember how it briefly dominated the news.

Ja, dat klopt. Alternatively, he might have said "Owww! That hurt, I must remember not to try that again!" Or, if around today, he might have wondered if he'd ever get to see another Elfstedentocht

@ Neven & Rob D "Higher than every ear since 2006" Would that represent an extremely close shave? ;-)

I realise that there are some seriously polarised views, both here and, even more particularly, on the ASIF, concerning the rapidity of Arctic Sea Ice decline over the next few years. Those with such views - of whichever persuasion - might benefit from a quick perusal (followed by a slower, more considered perusal) of the following GRL publication. The title of the paper is... "False alarms: How early warning signals falsely predict abrupt sea ice loss" http://eisenman.ucsd.edu/papers/Wagner-Eisenman-2015b.pdf Make of it what you will.

@ NeilT & Hans Despite my frequent protestations that I am unconvinced by the idea of a 5-year cycle, I nonetheless feel it is incumbent upon me to point out when others - especially those far more knowledgeable than I - might beg to differ. Whilst responding to a comment on the ASIF IJIS thread earlier today, I cited a GRL article from way back in 2003. As it had been some time since I had last looked at that paper, it seemed worthwhile to refresh my memory of what was being said therein. Just above Fig 1, there is a sentence which reads ... "The 365-day running mean of the daily anomalies suggests a dominant interannual variability of about 5 years". http://onlinelibrary.wiley.com/doi/10.1029/2003GL018031/full

@ NeilT "I have an issue with the last stat for 2016 as chartic says it was 4.13 and this csv says it was 4.72" Neil, that Charctic value of 4.137 million sq kms is the lowest running 5-day average figure, whereas the value quoted in the monthly summation .csv file represents the monthly average. NSIDC use a legacy averaging technique which many people find unsatisfactory. This is predicated upon applying the 15% cut-off rule temporally, rather than just spatially. In other words, if a particular grid-cell was seen as being ice-covered for 15% of the swathe-path passes during the month, the monthly averaging technique would count this towards the monthly total. In other words, if a region of, say, 2 million sq kms was seen as ice covered for just the first 2 and the last 3 days of September, then that 2 million sq kms would be ice-covered for >15% of the measurement period, and would therefore count towards the monthly average. On the other hand, if the same grid cells had been covered for all 30 days of September, NSIDC's monthly averaging technique would report these two scenarios as having the same extent. Personally, I think that averaging the daily values over the month would give a more realistic summation. For what its worth, here are the 1979-2016 September averages (in millions of sq kms) Col 1 = year, Col 2 = published, Col 3 average of Sept dailies, Col 4 = difference. 1979 7.22 7.051 -0.169 1980 7.86 7.667 -0.193 1981 7.25 7.138 -0.112 1982 7.45 7.302 -0.148 1983 7.54 7.395 -0.145 1984 7.11 6.805 -0.305 1985 6.94 6.698 -0.242 1986 7.55 7.411 -0.139 1987 7.51 7.279 -0.231 1988 7.53 7.369 -0.161 1989 7.08 7.008 -0.072 1990 6.27 6.143 -0.127 1991 6.59 6.473 -0.117 1992 7.59 7.474 -0.116 1993 6.54 6.397 -0.143 1994 7.24 7.138 -0.102 1995 6.18 6.080 -0.100 1996 7.91 7.583 -0.327 1997 6.78 6.686 -0.094 1998 6.62 6.536 -0.084 1999 6.29 6.117 -0.173 2000 6.36 6.246 -0.114 2001 6.78 6.732 -0.048 2002 5.98 5.827 -0.153 2003 6.18 6.116 -0.064 2004 6.08 5.985 -0.096 2005 5.59 5.504 -0.086 2006 5.95 5.862 -0.088 2007 4.32 4.267 -0.053 2008 4.74 4.687 -0.053 2009 5.39 5.262 -0.128 2010 4.93 4.865 -0.065 2011 4.63 4.561 -0.069 2012 3.63 3.566 -0.064 2013 5.35 5.208 -0.142 2014 5.29 5.220 -0.070 2015 4.68 4.616 -0.064 2016 4.72 4.505 -0.215 As one would expect, the average of the daily values gives a lower monthly figure - in every year - than the value published by the NSIDC. In almost all cases, the rank either remains unchanged, or varies by a single position if one employs averaging of the daily values. A notable exception is 2016, which goes from 5th to 3rd lowest. Regarding the putative 5-year cycle which you and Hans tend to favour, I personally still remain unconvinced about this. As we have discussed on an earlier thread, whilst the rolling annual average also supports your hypothesis, I don't yet feel the forensic trail is long enough to be certain one way or the other. I also have this horrible feeling that 2018 or 2019 could end up worse than this year.

@ John Bilsky "Just took a 12 second plunge in the Beaufort Sea at Prudhoe Bay ..." If these "in-situ observations" are being supported by the NSF, I really think that you should significantly extend the plunge duration. ;-)

@ Jim H Thanks for that side-by-side comparison Jim - I'm sure to sleep better tonight! ;-) @ Rob "... September SIE average will be some 5.4 M km^2 ..." Wow. That is bigger than any of the NSIDC September averages since 2006. We both know that SIE projections prior to June/July tend to lack skill, but that suggests that your algorithm perhaps places undue significance on snow cover - at least when that variable is appreciably at odds with the SIE conditions at the time of year. I'll watch with interest how your SIPN values evolve over the coming months. @ everyone. I know this is OT, but the BBC Horizon programme will be doing a special this evening concerning the enforced relocation of the BAS Halley station on the Brunt Ice Shelf. The title will be... Horizon: Antarctica - Ice Station Rescue http://www.bbc.co.uk/programmes/b08tj2zr The programme should be available on line shortly after its transmission this evening.

Wayne (as opposed to Wayne K) :-) A mini-debate has started on the IJIS thread of the ASIF concerning air temps above ice. As this is a subject on which you have commented several times on the ASIB (unless I've mis-remembered - an increasingly common event these days, I'm forced to admit) perhaps you might care to share your thoughts on that thread? See comments #4294 and onward on... https://forum.arctic-sea-ice.net/index.php/topic,230.4250.html

@ NeilT & Hans G "Hans and I have been ruminating on a cyclical melt which is evolving..." Gents, I've just posted something pertaining to this idea on Espen's IJIS thread (#4260) on the ASIF. https://forum.arctic-sea-ice.net/index.php/topic,230.4250.html I'd appreciate your thoughts.

@ Wade It is not letting up either. Since my last post on this thread, the NSIDC monthly global sea ice extent and area records have been broken for January, February and March. (The April area and extent figures will be out round about May 2nd or 3rd, and they will both be new monthly records.) The rolling 12-month average for extent has dropped from 22 million sq kms (Jan - Dec 2016) to 21.7 million sq kms (Apr 2016 - Mar 2017). The rolling 12-month average for area has dropped from 16.47 million sq kms (Jan - Dec 2016) to 16.3 million sq kms (Apr 2016 - Mar 2017). To put this in context, the average annual extent (1979-1999) was 24.18 million sq kms, and for area was 18.82 million sq kms. That's a 10.3% reduction in extent, and, more worryingly, a 13.4% reduction in area. However, there was some "low hanging fruit" - especially in the Antarctic - which made it easier to break records. Last year's Antarctic numbers from April through to August were nothing special, so global records over that period are on the cards - even without any spectacular losses in the Arctic.

@ Rob & NeilT I took a wild swing at answering the "Volume versus area/extent" question on the ASIF. https://forum.arctic-sea-ice.net/index.php/topic,1834.900.html Comment #949 My simplistic number crunching came down on the side of volume.

For those unaware of "March for Science" mentioned above by Rob... https://www.marchforscience.com/mission/

@ Susan See the Arctic Image of the Day thread on the forum. http://forum.arctic-sea-ice.net/index.php/topic,416.800.html Comment #835 and onwards.

@ John C Good to see that the Daily Malicious has truly got its finger on the pulse. In that article (dated 18th April) the DM states that... "Earlier this year it was reported that Moscow is starting to build nuclear icebreakers as it vies for dominance in the polar region with traditional rivals Canada, the United States, and Norway as well as newcomer China." Despite the DM's "earlier this year" bollox, the first I heard about Russian plans to build a new class of nuclear icebreaker was way back in 2013. http://barentsobserver.com/en/arctic/2013/11/russia-lays-down-worlds-largest-nuclear-icebreaker-06-11 Scheduled completion of the first in class (the Arktika) has slipped from this year, but it is expected to be launched during 2018. Work is under way on the next two (to be called Sibir and Ural), and Rosatomflot is giving consideration to a fourth and fifth vessel. http://www.interfax.com/newsinf.asp?pg=2&id=722756 That is, of course, in addition to new conventional-powered ice breakers for the Russian Navy. The first of these, the Ilya Muromets, was launched in June of last year. http://www.defensenews.com/story/defense/naval/2016/06/11/russia-unveils-new-navy-icebreaker-arctic-military-focus/85747556/ You just can't beat the Daily Malicious for breaking news, can you? Going from the sublime to the ridiculous, it is quite astonishing to realise that there are some on the forum who think that the Arctic will be ice-free all year round within the next 6 or 7 years. So, if that were true, there should be some nuclear powered vessels going for a song by about 2023, or thereabouts. There's no helping some people.

Rob, The argument I posited can, of course, operate in the opposite sense. In the example I gave using a floe which was 5 grid cells in width, the monthly extent would register as 27 grid cell units, despite the fact that the actual size of the floe was 5 units. Consider what would happen in the example I gave if the width of the floe was 4 grid cell units rather than 5. Day 01: XXXXOOOOOO OOOOOOOOOO OOOOOOOOOO OOOOO Day 02: OXXXXOOOOO OOOOOOOOOO OOOOOOOOOO OOOOO . . Day 30: OOOOOOOOOO OOOOOOOOOO OOOOOOOOOX XXXOO Day 31: OOOOOOOOOO OOOOOOOOOO OOOOOOOOOO XXXXO Under that scenario, the NSIDC monthly averaging technique would register no cell with occupancy greater than ~ 13%, and would consequently assign an overall zero value for the month. However, owing to the inherent asymmetry caused by the 15% selection rule, the over-estimates and under-estimates will not simply tend to cancel each other out. The first example I gave caused an over-estimate of 22 grid cell units, whereas the second only introduced an under-estimate of 4 units.

Typo alert: The grid cell layout in the comment above should read... Day 01 Day 02 . . Day 30 (NOT 31!) Day 31 Once again, I would just like to say "D'oh!".

@ Rob "... in as far as you[r] floe does not reduce the ice concentration in the pixel it left behind below 15% ..." Yes, that's precisely what I meant when I used the term "edging effect". Unfortunately, I entirely failed to explain what I meant by this term. {D'oh!} Exactly the same condition applies at the leading edge as one approaches the month end. Perhaps I can explain best by means of an example. Consider a floe which is 5 grid cells wide in the E - W direction, and one grid cell in length measuring N - S. Imagine that this cell drifts (say) west to east at a rate of one grid cell/day, and that the 30 grid cells to the east are clear of ice. Using an "X" to indicate ice, and an "O" for open water, in a 31-day month, these 35 grid cells would appear as follows... Day 01: XXXXXOOOOO OOOOOOOOOO OOOOOOOOOO OOOOO Day 02: OXXXXXOOOO OOOOOOOOOO OOOOOOOOOO OOOOO . . Day 31: OOOOOOOOOO OOOOOOOOOO OOOOOOOOOX XXXXO Day 31: OOOOOOOOOO OOOOOOOOOO OOOOOOOOOO XXXXX Numbering these cells 1-35 from left to right, the percentage occupancy reads... Cells 1 & 35 ~3% Cells 2 & 34 ~6% Cells 3 & 33 ~10% Cells 4 & 32 ~13% Cells 5-31 (inc) ~16% Under these, admittedly extreme, conditions, the floe - which has a grid cell size of 5 units - would rack up 27 units in terms of the monthly extent, as cells 5-31 are ice-covered for >15%. ..... Regarding the Stnd Devs of your residuals (250k km^2 for SIA versus 340k km^2 for SIE), there is an intriguing equality which can pop out of the numbers. Using NSIDC monthly values, the 1979-2016 grand averages for September SIA and SIE are 4.64 million km^2 and 6.31 million km^2 respectively. When I'm looking at SDs for different sized objects, I usually do an informal normalisation by dividing each SD by the arithmetic mean size of the relevant object. 250/4640 = 0.053879 340/6310 = 0.053883 I expected the "normalisation" to produce a closer result, but that's just bloody spooky.

@ Al & Rob One of the ways in which this "boost" can be boosted is with increased mobility of the ice - which is exactly what we are experiencing. Imagine a largish floe which is being merrily transported along in a vaguely continuous fashion, but is neither melting nor growing. Now consider what happens if the transport rate is such that the trailing end of the floe reaches the position previously occupied by the leading edge, but about 5 or 6 days later. Over the course of a month, the swathe path covered by such a moving floe would be approximately 5 or 6 times the actual dimensions of the floe itself. However, using the NSIDC monthly averaging technique, the entire swathe path would be classified as ice-covered extent, as (apart from edging effect) each grid cell would have been covered for the requisite time. Under such conditions, the monthly extent clocked up for the floe would therefore be approximately 5 or 6 times the actual size of said floe. Obviously, the transport rate chosen for the above example represents a worst-case scenario. Nonetheless, it would be easy for a slower-moving floe to drift over a swathe path which considerably exceeds its own dimensions. Consequently, under the existing NSIDC averaging technique, it would be the swathe path dimension which gets included in the overall monthly average, rather than the actual floe dimension.

There is an old saying about "pictures speaking louder than words". I can think of many examples to back this up, but undoubtedly one of the best can be found amongst Jim Pettit's plethora of PIOMAS representations. http://iwantsomeproof.com/extimg/siv_annual_max_loss_and_ice_remaining.png @ Neven - given Jim's OK to utilise his material, I think that would be an excellent candidate for inclusion in future PIOMAS updates