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Chris Reynolds
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John, If you're right (the 'if' is not meant to cast doubt, it just means I don't know), then you use the appropriate tool for the job. And in your case the NAO seems appropriate.
Toggle Commented Sep 13, 2014 on PIOMAS September 2014 at Arctic Sea Ice
John Christensen, Hurrell, 2000, Climate: North Atlantic and Arctic Oscillation (NAO/AO). Extract from the Encyclopedia of Atmospheric Science - used in place of the peer reviewed paper I can't find at present. http://www.cgd.ucar.edu/staff/jhurrell/docs/hurrell.NAO.EAS03.pdf "That the NAO and AO reflect essentially the same mode of tropospheric variability is emphasized by the fact that their time series are nearly identical, with differences depending mostly on the details of the analysis procedure." Or checking in my Favourites I find a link to this page: http://www.jisao.washington.edu/wallace/ncar_notes/ "It follows that the NAO and AO are synonyms: they are different names for the same variability, not different patterns of variability. The difference between the terms is in whether that variability is interpreted as a regional pattern controlled by Atlantic sector processes or as an annular mode whose strongest teleconnections lie in the Atlantic sector." Figure 1 on that page is an amusing summary of the relationship.
Toggle Commented Sep 12, 2014 on PIOMAS September 2014 at Arctic Sea Ice
Blaine, The problem I am having is as follows: 1) I have read multiple references in papers, granted mainly winter, if I recall correctly, to AO/NAO like patterns. The formation of the AO/NAO patterns by land/sea masses is likely to apply to other patterns driven by various factors related to Arctic climate change. Yes the 2007 to 2012 summer pattern is like the AO/NAO, but I view it as significantly different enough to justify viewing it differently. 2) The AO/NAO has not in the past driven strong Dipole like behaviour within the Arctic. 3) The AO/NAO has not in the past been associated with the unusually high geopotential heights seen over Greenland. https://farm4.staticflickr.com/3858/15166606982_47c6d17e6b_o.png 4) 2007 to 2012 all fall within the eleven lowest NAO indices for June July August. Excluding 2014 from the 2007 and 2012 due to its complication. Here is average SLP for 2007 to 2012. https://farm6.staticflickr.com/5588/15022681310_66645458a5_o.png Here is average SLP for the ten lowest NAO years excluding 2007 to 2012. https://farm4.staticflickr.com/3883/15186330706_d65cccaf38_o.png I've presented these as averages, not anomalies as some have complained about the 1980 to 2010 anomaly period partly covering 2007 to 2012. The shift to a more Greenland centred behaviour after 2007 seems clear to me. Needless to say, similarity in the Pacific and Atlantic is irrelevant as this is topographically driven, and topography has not changed. Yes the AO/NAO are essentially the same thing. I use the AO because it reflects Arctic Ocean dominant pressure. Summer Pattern Correlation. I've resorted to using correlation because my maths aren't up to PCA, which would have been a preferred method. June July August 1979 -0.440 -0.297 0.386 1980 -0.081 0.738 -0.262 1981 0.516 -0.389 -0.571 1982 0.724 -0.539 0.023 1983 -0.800 -0.134 -0.272 1984 -0.048 -0.114 -0.588 1985 0.249 0.265 0.446 1986 -0.670 -0.081 0.250 1987 0.721 0.209 0.486 1988 -0.557 0.485 -0.241 1989 -0.639 -0.695 -0.032 1990 0.015 -0.334 0.478 1991 0.016 -0.197 -0.862 1992 -0.232 -0.499 -0.388 1993 0.285 0.382 0.048 1994 -0.797 -0.622 -0.442 1995 -0.400 0.657 -0.157 1996 -0.654 -0.733 -0.340 1997 0.795 0.252 -0.600 1998 0.669 0.147 -0.261 1999 -0.636 0.399 0.680 2000 -0.181 0.140 -0.097 2001 -0.304 0.189 -0.166 2002 -0.576 -0.489 0.179 2003 0.254 -0.088 -0.423 2004 0.382 -0.557 0.475 2005 0.463 0.260 0.386 2006 -0.682 -0.097 0.027 2007 0.725 0.759 0.532 2008 0.612 0.774 0.567 2009 0.685 0.784 0.436 2010 0.660 -0.405 0.639 2011 0.787 0.788 0.824 2012 0.633 0.316 0.459 2013 -0.755 -0.126 -0.463 2014 0.470 0.394 0.656 Correlations with NAO by month. Jun Jul Aug 1979 to 2014, -0.870, -0.657, -0.517 2000 to 2014, -0.837, -0.780, -0.580 1979 to 2006, -0.857, -0.574, -0.288 Note the drop in correlation through the summer when the post 2007 period is excluded. However I will defer to your expertise and desist from mentioning the matter again. I'm busy enough with sea ice and the day job.
Toggle Commented Sep 11, 2014 on PIOMAS September 2014 at Arctic Sea Ice
Rob, I've looked at the stratosphere with regards the 2007 to 2012 period, but found little conclusive. My hunch remains that the Greenland ridging is a central issue, either a parallel result of the same underlying causal issue, or an element of cause itself. https://farm4.staticflickr.com/3858/15166606982_47c6d17e6b_o.png I've not done the math yet. But I have previously taken average GPH500 north of 20 degN (IIRC) and subtracted it from the Greenland GPH to get an idea of the behaviour of the Greenland ridge when adjusted for the overall rising of the atmosphere with AGW. The result is a striking jump in GPH at 500mb over Greenland. http://farm4.staticflickr.com/3705/10230342105_4765d6ffda_o.png I am still working on this problem.
Toggle Commented Sep 10, 2014 on PIOMAS September 2014 at Arctic Sea Ice
Robert, You can see what you think from a previous post comparing PIOMAS, ASCAT, and the Drift Age Model, here: http://dosbat.blogspot.co.uk/2013/02/ascat-piomas-and-dam.html QuikScat was the previous system before ASCAT. If you scroll below the text on this link you'll see a sequence from 2000 comparing QuikScat in January and PIOMAS in January. http://dosbat.blogspot.co.uk/2013/08/seeking-understanding-vs-spouting-empty.html I use January because any ice that is over 2m in Dec/Jan is very likely to be multi year ice because first year ice hasn't had the time to thicken to 2m by that stage in the winter.
Toggle Commented Sep 9, 2014 on PIOMAS September 2014 at Arctic Sea Ice
Hell, four replies in a row... Robert, I'm not doubting what you say, it's anecdotes like yours that I use to caution myself against getting to concerned with small differences in area/extent/volume. As for the reality of th PIOMAS volume increase. Most of it is in the Central Arctic (Cryosphere Today regions). In ASCAT (a type of satellite radar) multi-year ice shows up as white, first year ice shows up as greyer. http://manati.star.nesdis.noaa.gov/ascat_images/ice_image/ I'll be checking there to compare PIOMAS ice over 2m thick in December and/or in January, if PIOMAS is right then the mass of thicker ice around that time should agree in shape with the white area in ASCAT around that time.
Toggle Commented Sep 9, 2014 on PIOMAS September 2014 at Arctic Sea Ice
Good Lord, how did I miss it. PlanetDufus is repeating the Global Cooling scare in the 1970s carp.... The Myth of The Global Cooling Consensus. Peterson, Connelly, Fleck, 2008, BAMS. Numbers of scientific papers published citing Warming, Neutral, and Cooling. https://farm4.staticflickr.com/3922/15004416149_e727f05a77_o.png "In July 1979 in Woods Hole, Massachusetts, Jule Charney, one of the pioneers of climate modeling, brought together a panel of experts under the U.S. National Research Council to sort out the state of the science. The panel’s work has become iconic as a foundation for the enterprise of climate change study that followed (Somerville et al. 2007). Such reports are a traditional approach within the United States for eliciting expert views on scientific questions of political and public policy importance (Weart 2003). In this case, the panel concluded that the potential damage from greenhouse gases was real and should not be ignored. The potential for cooling, the threat of aerosols, or the possibility of an ice age shows up nowhere in the report. Warming from doubled CO2 of 1.5°–4.5°C was possible, the panel reported. While there were huge uncertainties, Verner Suomi, chairman of the National Research Council’s Climate Research Board, wrote in the report’s foreword that he believed there was enough evidence to support action: “A wait-and-see policy may mean waiting until it is too late” (Charney et al. 1979). Clearly, if a national report in the 1970s advocates urgent action to address global warming, then the scientific consensus of the 1970s was not global cooling." So who was talking about an ice age - the press, as you imply with your reference to the NYT. It was not a consensus amongst scientists. You believe the scare stories you read in the press, imprinted with your own bias from your choice of newspaper. I'll continue to read the actual scientific papers and make up my own mind.
Toggle Commented Sep 9, 2014 on PIOMAS September 2014 at Arctic Sea Ice
John, I agree. The position A is however somewhat limited, it neglects the critical role of preferrential loss of thick ice (first year ice volume is increasing) and the role that this has had in facilitating ice loss events like 2007 and 2012. Note that there are other volume loss events as big as 2007 (and 2010 - which was not associated with area/extent loss event). http://farm9.staticflickr.com/8438/7911627906_4b1c45096e_o.jpg This is because those earlier volume losses happened with thicker ice, so they were not able to reveal open water leading to massive area/extent losses. The role of AGW is in the long term volume loss, and most of this volume loss has come from loss of older thicker ice. The role of weather driven events like 2007 is in 'taking advantage' of thinner ice. Turning to this year, there are factors such as the Greenland ridging and low/high pressures between Siberian coast and the central pack, both associated with the strong Arctic Dipole between 2007 and 2012. The presence of those factors this year (to me at least) seriously begs the question 'what was different in 2014?'
Toggle Commented Sep 9, 2014 on PIOMAS September 2014 at Arctic Sea Ice
BDS, Read Lindsay & Zhang, 2004, The Thinning of Arctic Sea Ice, 1988–2003: Have We Passed a Tipping Point? http://journals.ametsoc.org/doi/abs/10.1175/JCLI3587.1? My blog post on that paper is here: http://dosbat.blogspot.co.uk/2014/03/what-caused-volume-loss-in-piomas.html L&Z find (fig 3) a small increase in Arctic Ocean thickness from around 2.5m in 1950 to around 3.25 in 1987. By 2004 thickness is down to 2m. Annual average thickness. PlanetDufus, Walsh and Johnson 1978, yes I have previously read it. Your point in linking to it? 1) Check out figure 8. What does that tell you? What would the situation look like using data for the last 20 years? The changes during the 1953 to 1977 period have marked spatial variability. Whereas since 1995 there has been a marked decline of extent in all regions. 2) Check out figure 5. That does not show that 1979 is a high point, in fact that study shoes that the 24 month running mean is greater over the period 1965 to 1973. Yes the overall trend over that period is up, no, that does not mean 1979 is a high point. 3) Stop wasting my time. 4) er... 5) that's it.
Toggle Commented Sep 9, 2014 on PIOMAS September 2014 at Arctic Sea Ice
Sorry Neil, I'm doing a really poor job of understanding and/or of explaining. When you say: "That Ice, of the same area, was not of the same consistency. It was 1mkm^2 more FYI than at the beginning of the 2012 melt season. So how could it be only 40kkm^3 less than 2012. Where did all that extra volume come from?" I read it as more or less what I outlined (as you quote in the comment above) and my answer is the same. Maybe I'm tired. I'll think about it over the next few days. With a bit of luck someone will read this exchange and reconcile us.
Toggle Commented Sep 8, 2014 on Ever sailed to 85N? at Arctic Sea Ice
Neven, You're no dolt. You allow the evidence to form your opinion, that's a sign of intelligence. :) NeilT, JD Allen, Well put. Perhaps it could be put more simply: If people would just drop the political carp and approach the issue of Arctic sea ice loss with an open mind they would find the most exciting area of research in current science. OK, I'll have to comment on the Himalaya issue. I've never read WG2, I'm interested in the science so I stick to WG1. But if WG2 is anything as big as the WG1 (The scientific basis report) to find a screw up in one paragraph is not surprising. In around 2007 when I was seriously doubting my scepticism I downloaded AR3 WG1 Scientific Basis. Chose about ten pages at random and went through the references to see if they supported the text. Since then I use the Scientific Basis as my first port of call when reasrching something AGW related, it is sound, reliable, and conservative. Like the sort of technical consultant you don't regret hiring.
Toggle Commented Sep 8, 2014 on PIOMAS September 2014 at Arctic Sea Ice
Right, I'll try to wade through the carp to salvage something of interest (WTF have the Himalaya got to do with the Arctic - unless we're talking Rossby wave breaking???). Robert, I've heard others say the same sort of thing. I've also noticed areas of apparently no ice on MODIS that have ice in NSIDC. Two things to note: 1) The CAA has always been tricky because there is so much coast, coast presents problems with the sensors, looking at raw NSIDC Concentration data there is generally ice shown all around the UK - now we know that isn't there. NSIDC mask out this data, but it is possible the mask doesn't catch all such spurious data. 2) In the area of the CAA an NSIDC grid box is typically around 640kmsq in area. That's 25 X 24 km. It is conceivable that you could fly over a grid box and not be able to see the entire grid box - I'm not 100% convinced about that but it is a possibility. Actually I'll add another: 3) No remote sensing product is perfect, even different sea ice products from the same platform give different figures. My solution to this is rather amateurish, I stick to one product on the assumption that whatever problems apply now apply in the past. So at least comparisons in time are likely to catch changes. It is possible that 2014 has been overestimated, but my guess is it will be a small effect. I am by no means as expert as the Polar Science Team, but I process the gridded PIOMAS data they provide and, frankly, spend an unhealthy amount of time sat at my laptop playing around with data extracted from the gridded data. When there is an inconsistency, such as that which led Dr Zhang to re-work to V2.1, I tend to notice it too (I did with that). I've got lots of oddities I can't explain, but all look like problems with my comprehension, not the model. Personally I don't think PIOMAS is wrong this year. I'm looking at the atmosphere for the answer as to why 2014 was such a boring melt season.
Toggle Commented Sep 8, 2014 on PIOMAS September 2014 at Arctic Sea Ice
Wayne, There certainly is an argument for thicker ice having a role this year, expecially in the East Siberian Sea. The Drift Age Model, HYCOM and ASCAT showed the tongue of MYI entering the Pacific Sector. However 2010 had a similar event, and June/July average compactness was 0.685, whereas this year it was 0.733, a significant increase (June July average compactness for 2007 to 2012 was 0.681).
Toggle Commented Sep 7, 2014 on PIOMAS September 2014 at Arctic Sea Ice
KZ, It's not ad hominen. An ad-hom is what some people do when they can't dismiss their opponent's arguments with evidence and reason. I can dismiss their arguments with evidence and reason, I just can't be bothered anymore, mole-whaking is futile and merely fuels the mistaken belief that they have a point worth discussing. Calling such people dolts is an insult, not and ad-hom attack. Iceman and David R have tried to move discussion in a fruitful direction, Wayne has now contributed. How about your contribution?
Toggle Commented Sep 7, 2014 on PIOMAS September 2014 at Arctic Sea Ice
Neil, The statement regards thickness was related to a tag onto the reply to you about people claiming that later open water will mean less winter ice, I'm just saying it is not necessarily so. The critical issue is that thicker ice thickens far less than thin ice or open water forming new ice. Hence the following: Start Thickening 0.1m 1.35m 100% 0.5m 1.02m 75% 1m 0.75m 56% 2m 0.46m 34% That is to say, 0.1m thick ice at minimum in September leads to 1.35m growth (with constant -10degC surface temperatures), whereas for 1m thick ice in September the thickening is around half of that, 0.75m. These are for the same temperature of -10degC, nothing extra-cold needed. Using whole Arctic volume. Year.April...September 2011 22.7 4.3 2012 23.4 3.7 2013 23.3 5.4 2014 23.1 7.2 So what you are saying is that after 2012's September minimum the ice grew back by April 2013 to almost the same volume as in April 2012. Then with more second year ice after summer 2013, the April 2014 figure was still around the same. What I am saying is that even with the different minimums of 2011 to 2013, most of the area involved is going to be virtually first year ice, in all of thos years end of season extents in Beaufort round to Barents was such that those seas were virtually sea ice free. So most of the thickening was to thermodynamic levels, call that around 2m (although it varies across the seas). However within the Central Arctic is where you find most of the different thicknesses of ice and hence most of the volume difference in September, because almost all the other seas had melted out. The Central Arctic winter extent is around 4.45M km^2. The Artic Ocean extent is around 10.2M km^2. So within the peripheral seas over half the volume is set by the thermodynamic growth from open water or very thin ice. Then within the Central Arctic the thickness/growth relationship takes precedence because by September that is where the thicker ice is. You may have noticed that when I reposted the initial thickness/ thickening figures I put a percentage agains each one. For thin ice in the peripheral seas (or periphery of the central Arctic pack), say around 50cm, the thickening is 75% of what it is for open water (the 0.1m thick initial), but for 1m thick you're only getting half the thickness, or volume, increase. And for ice around 2m the volume gain is only about 1/3 of what it is for open water. So add more thicker ice at the end of the season and this thcker ice (within Central region) only accounts for volume gain in under half the Arctic Ocean, and then, the thicker the ice is the less it contributes to overall volume increase the following winter. So that is how I would explain the apparent incongruity of recent volume minimums as judged against the maximums that follow.
Toggle Commented Sep 7, 2014 on Ever sailed to 85N? at Arctic Sea Ice
Iceman, Good topic to discuss. From my most recent blog post. http://dosbat.blogspot.co.uk/2014/09/piomas-august-2014.html Considering Wipneus's graph of Fram export in PIOMAS. The largest possible contribution to the difference between August 2013 and 2014 volume is under 8.7%. So we can put aside Fram. Temperatures have been unusually low. http://1.bp.blogspot.com/-aEt5MI-gNqs/VAwF2-kLgOI/AAAAAAAAA9c/8KZeXoXNn9k/s1600/Air%2BTemp%2BSfc.png Aloft, at the 850mb level 2014 is seen to be a bit warmer than 2013, but not as warm as the 2007 to 2012 years. However 2014 pressure is similar to the 2007 to 2012 'summer pattern' 2007 to 2012 summer pattern. http://farm8.staticflickr.com/7366/9465607999_8edc13ef51_o.png 2014. http://3.bp.blogspot.com/-fel0SxFdSMA/VAwF2qF-0rI/AAAAAAAAA9g/5Ekc7pdStHY/s1600/Sfc%2BPressure.png The correlation between the summer pattern and 2014 is back up, after 2013, along with the other 2007 to 2012 years. https://farm4.staticflickr.com/3878/14980420577_b05a8877dc_o.png That makes 2014 look like a high melt year due to the dipole between low pressure across Siberia, and high over the Arctic Ocean that is associated with the summer pattern. But this year the Atlantic Ocean deviated from the pattern with high pressure (what role has that played?). 500mb geopotential height (500mb GPH) was back up this year, which fits with the idea 2014 was a summer pattern year. https://farm4.staticflickr.com/3858/15166606982_47c6d17e6b_o.png I suspect the steering of the jet caused by this has had a role in the wet summers that marked 2007 to 2012 in the UK and NW Europe. But this summer has been dry in comparison. And taking the difference between 2007 to 2012 and 2014 in 500mb GPH. https://farm4.staticflickr.com/3904/15143965926_2ecb1031d2_o.png Across Siberia looks like a negative PNA. https://farm4.staticflickr.com/3895/14980424927_10d9a643f6_o.gif While across the US and Atlantic looks like a negative MEI ENSO(La Nina). https://farm4.staticflickr.com/3849/15167001145_2fd2025f9a_o.gif Which is odd because both those indices have been moderately positive for June July August. If you see another interpretation to those last three please let me know. With temperature over sea ice one has to be cautious, loss of ice cover in summer reveals ocean which warms above zero degC. However the bulk of extra volume this year is due to the Central Arctic (78% of the total PIOMAS volume increase from 2012 is from grid box thicknesses between 2.0 and 3.9m thick in the Central Arctic), that's away from the ice edge off the CAA. So I don't think we're looking at the ice driving temperature, I think temperature, and hence weather, has driven 2014. This comment has been long enough so I'll wrap up, but before I do here are two plots. Both are NCEP/NCAR 2014 minus 2007 to 2012. When both were produced I got the same comment from the system 'This plot is not dissimilar to the PNA'. Sfc temperature. https://farm6.staticflickr.com/5575/14980781407_bb611aa94e_o.png Does this show (Beaufort Chukchi, ESS cooling in 2014 due to more ice, same in Kara and Barents. Sfc pressure. https://farm6.staticflickr.com/5552/14980626079_d4385ede79_o.png
Toggle Commented Sep 7, 2014 on PIOMAS September 2014 at Arctic Sea Ice
Neil, Most of the area is now represented by first year ice, so most of the volume is set by the thickening for first year ice. Then the thicker ice will thin less over the melt season. So adding that in produces less ice over the melt season, removing it makes more new ice. As I've already been looking at this. Say you have a surface temperature of -10degC applied for 210 days (not realistic - I'm working on that). For increasing initial ice thickness the growth over those 210 days reduces. Start Thickening 0.1m 1.35m 0.5m 1.02m 1m 0.75m 2m 0.46m That's start thickness at day 1, and the thickening over those 210 days from the start thickness. The simple model I use can be compared with PIOMAS, I've done so for the East Siberian Sea. Working monthly (I only have monthly temperature data). The May 2012 average thicknesses for PIOMAS and for the simple model are: PIOMAS 2.31m Monthly model 2.48 The simple model has no snow, so it tends to overshoot. I've been told by people disagreeing with the slow transition idea that later open water will cause the pack thickness in April/May to reduce. Delay the transition to sub zero temperatures and the start of thickening until later in the winter. I'm working on temperature adjustment for that but using monthly temperature. Here's the actual NCEP/NCAR temperatures for the ESS and my adjustment based on no ice forming until December. Actual Adjusted -0.40 -1.80 No ice -7.74 -3.00 No Ice -22.46 -9.00 No Ice -28.55 -14.00 * -26.66 -26.66 -29.33 -29.33 -24.41 -24.41 -12.97 -12.97 -3.12 -3.12 And by May the thickness is 2.44m, similar to when PIOMAS and the simple model are run with 2012 profiles. In the ESS during autumn surface temperatures for month N+2 show little correlation with month N, even after a large perturbation like 2012. In 2012 ice growth in the ESS had started by October.
Toggle Commented Sep 7, 2014 on Ever sailed to 85N? at Arctic Sea Ice
Neil The rate of ice growth is proportional to 1/thickness. So thinner ice grows much faster than thicker ice. Start off with a lot of open water/very thin ice and you get extremely vigorous ice growth in the early winter. PIOMAS is just doing what it has been doing with ice volume from 1979 onwards - getting it pretty well correct.
Toggle Commented Sep 7, 2014 on Ever sailed to 85N? at Arctic Sea Ice
Has somebody opened up a portal to the dolt-dimension (i.e. WTFWT)? Oh, I remember, it was you Neven.... Still it's your blog. ;)
Toggle Commented Sep 7, 2014 on PIOMAS September 2014 at Arctic Sea Ice
Arcticio, Try this conference abstract: http://adsabs.harvard.edu/abs/2013AGUFM.C54A..05S "The long-term Fram Strait sea ice area export obtained from passive microwave satellite observations since 1982 shows no significant trend. However, for the last decade 2001-2009 a positive trend in sea ice area export can be observed." I've emailed you a copy of the paper Jim's linked to. If you don't have it I could send you a copy of the Smedsrud paper, "Recent wind driven high sea ice export in the Fram Strait contributes to Arctic sea ice decline." Which starts: "We use geostrophic winds derived from reanalysis data to calculate the Fram Strait ice area export back to 1957, finding that the sea ice area export recently is about 25 % larger than during the 1960’s. The increase in ice export occurred mostly during winter and is directly connected to higher southward ice drift velocities, due to stronger geostrophic winds." Lack of Fram export is a factor in this year's poor melt season, but I can't put numbers to it. The PIOMAS IceVel files are only updated to 2013 and it's a variable I've never looked at. Wipneus has looked at it though. Mmm, maybe there's a way to infer without IceVel.
Toggle Commented Sep 6, 2014 on Ever sailed to 85N? at Arctic Sea Ice
And the first commenter takes the prize for dumbass of the thread.... well done that man ;) I've had today free and have spent most of the day delaying writing up a PIOMAS August summary and looking at the atmosphere this year. I'm seriously confused! I now doubt the PNA cuts it, although the graph shows dominant negative swing over the last three years... http://www.cpc.ncep.noaa.gov/products/precip/CWlink/pna/month_pna_index.shtml This summer was a mildly positive PNA (about 0.5 sigma). Greenland 500mb GPH is back up to similar levels as the 2007 to 2012 years. Also the 'summer pattern' correlation makes 2014 look like a 2007 to 2012 year. But the temperature for JJA was around the same as 2013, and well below the typical for summer in the 2000s. 500mb GPH plots for 2014 minus 2007 to 2012 looks kind of ENSOish, but the sign's wrong over Siberia. Hard to see any semblance of the PNA or NAO in it. It's very puzzling, aside from temperature itself (surface and 850mb), everything looks like it was a good melt year atmosphere wise. One oddity, taking the geopotential height for 500mb around 64degN latitude, whereas 2007 to 2013 show level or a hump around Greenland, 2014 stands out as a significant dip, well below the other post 2007 years (and in anti-phase to 2012). In that respect 2014 looks more like a 1990s or early 2000 year than a post 2007 year. I do wish someone (NOAA/MetOffice/whoever) would provide an index of the Arctic Dipole strength. I don't think I'm up to principle component analysis.
Toggle Commented Sep 6, 2014 on PIOMAS September 2014 at Arctic Sea Ice
John, But again four of the six are in the post 2010 period, and as I showed this period significantly increases the correlation. But in the post 2010 period there has been unusually strong dipole activity (at least in June according to Overland, and more generally in the summer due to the Siberian coastal low pressure tendency and Arctic Ocean/Greenland high). Furthermore in the post 2007 years there is the complication of a drop in thickness, which would increase open water formation efficiency and independent of the NAO cause an increase in summer losses. So I'm sorry but I don't consider your argument to be strong.
Toggle Commented Sep 6, 2014 on Ever sailed to 85N? at Arctic Sea Ice
Sorry second line should read: Therefore it is safe to say that in summer 2014 Laptev sea has had less ice extent than during any summer since 1979.
Toggle Commented Sep 5, 2014 on Ever sailed to 85N? at Arctic Sea Ice
There are 91 days from 1 June to 30 August (I've not had the chance to update since 30 August), of these 91 days, during 82 days Laptev Sea Extent has been the lowest on record. Therefore it is safe to say that in summer 2014 Laptev sea has had less ice extent than at any time since 1979. It could be argued that this was a random event. Strong winds from Siberia opened a polnya in winter, this was then extended during the melt season by ice albedo feedback, resulting in record recession of the ice in Laptev. Such a view is defensible, but it is too narrow. During June for the period 1980 to 1989 average sea ice thickness in Laptev was 2.07m (PIOMAS), 1997 to 2006 had an average June thickness of little less, at 2.01m (statistically indistinguishable). However after the crash of 2007, PIOMAS June average thickness from 2007 to 2014 in Laptev had dropped to 1.33m. So a more accurate assessment would seem to be that the initiation of the record low extent in Laptev was due to a random event, but without the substantial post 2007 thinning there would likely not have been the aggressive expansion of open water due to the ice albedo effect.
Toggle Commented Sep 5, 2014 on Ever sailed to 85N? at Arctic Sea Ice
John Christensen, Using extent data. R2's as in my earlier (long) post. 1979 to 2006 AO is 0.0907, NAO is 0.0135 1979 to 2014 AO is 0.1768, NAO is 0.2852 So even with extent data the relationship between AO and NAO, and the 1 June to 30 Aug extent loss behaves the same as area. There is little relationship between summer AO/NAO and sea ice loss during the period 1979 to 2006, it is only by including post 2007 data with the full period 1979 to 2014 that the relationship strengthens. In the above post I said I used 1979 to 2013, that was wrong, when I came to paste in the etent data it was 1979 to 2014. Using extent as opposed to area still suggests that the period after 2007 strongly affects the relationship, however once again drawing conclusions here is risky because we cannot determine what part of summer extent loss after 2007 is due to thinner ice and increased open water formation efficiency, and what part is due to weather.