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Chris Reynolds
UK
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Blaine, Yes, numerical argument should take precedent over verbal. However given this, and given that models are the most comprehensive numerical argument available, is it not significant that in models the growth thickness feedback overcomes volume loss from MYI resulting in a long tail? This is seen in 'forecasts' using PIOMAS, and Overland and Wang have twice shown that models (GCMs) that best repicate the seasonal cycle predict ice free by around the 2030s and no rapid crash in the 2010s or 2020s. Largescale overturning of the Arctic Ocean allowing Atlantic Water to more actively engage in ice loss has often been posited as a mechanism by which a rapid final loss of ice may occur. But this mechanism does not appear in GCMs (as far as I've read), and if it were to appear it might be expected to result in a rapid transition. However it is possible it does occur in some models, only for the heat to be vented in the subsequent autumn and winter (i.e. Tietsche et al's removal of all ice from 1 July). I had thought that small volumes would lead to strong albedo feedback and open water formation due to thinner ice. http://dosbat.blogspot.co.uk/2013/12/go-on-say-something-outrageous.html Consider the following graphic. http://farm8.staticflickr.com/7068/13294163744_ac22107ba2_o.png The blue line shows percentage open water (%OW) formed as a function of April thickness. It can be seen that, going from thickest ice to thinnest, from the right the %OW formation for thick ice is low. But around 2m the %OW increases dramatically. The red line shows average volume for each 10cm April thickness band during the 1980s. It can be seen that in the 1980s the peak volume was well away from the non-linear change in %OW formation around 2m. However now consider the situation since 2007. http://farm8.staticflickr.com/7304/13293955873_7c8482f7b7_o.png Here the peak volume has moved down to the region of non linear change in %OW formation. This has resulted in greater opwn water at the end of the melt season, and greater volatility in response to weather due to interaction between the thickness distribution in April and the steepness of the %OW curve. The problem is, if during each winter ice re-forms to roughly the same thickness the peak volume doesn't get the chance to move down taking even more of the ice into the high %OW formation region. Opposing the possibility of heat building by surviving the winter is the enormous amount of heat that can be vented in autumn after sunset in the Arctic. Consider the behaviour of PIOMAS thickness of ice in the Arctic Ocean. Year Arctic Ocean Volume (k km^3) 1998 25.4 1999 24.5 2000 23.5 2001 24.0 2002 23.7 2003 23.7 2004 22.5 2005 22.7 2006 21.7 2007 20.3 2008 21.1 2009 21.2 2010 20.8 2011 19.3 2012 19.4 2013 19.6 2014 19.3 Now think about the summers of 2009 to 2013, all very, very different. The energy gains of these summers will have been very different, yet all those summers were followed by very similar April volumes. The series is very short (2011 to 2014), but bear with that for a moment: This behaviour suggests to me a very powerful negative feedback with ample capacity to dump energy into the atmosphere, grow ice volume over the winter, and damp the trend of volume loss. Because despite those very different end summer amounts of energy accrued there is no indication of reduction of winter volume growth (the reverse is true).
Toggle Commented Aug 7, 2014 on ASI 2014 update 6: slow times at Arctic Sea Ice
Pete, "Pre-anthro-forcing did ice melt differently?" Good question. I'll think about it. Things that come to mind... Define 'melt' - do we mean the seasonal cycle? Obviously with regards multi-decadal trend the ice hasn't always been declining. Yes there have been recent changes to the seasonal cycle. The holocene climatic optimum when the ice was probably in a worse state than in summer 2012. But that was caused by increased summertime insolation, not a global warming that was year round and affected night time temperatures as well. The Barents Sea and Atlantic ice edge has been declining since at least the early 1900s. When did anthro-forcing start to have an effect?
Toggle Commented Aug 6, 2014 on Poof, it's gone at Arctic Sea Ice
Hi Chris, Ahh, I didn't realise your are Epiphyte, good work. I was initially confused as to why you were addressing me! I'm a bit lost by what you say above, surely if the thinner ice than 2013 has melted out that supports PIOMAS volume/thickness? Anyway, there is a fairly fundamental limit to the volume of ice that can be melted. Consider the following graph. https://farm4.staticflickr.com/3856/14548870398_4ae3450902_o.png I did it to show how unusual a total melt out from an average 2m thickness of the pack in April would be, for completeness I'll go over that, but for now... The graph shows the difference between the start and end data of successive ten day periods from January through to December. This is basically the rate of change of sea ice volume. Note how it dips around the summer solstice and peak around the winter solstice. It is worth comparing it with insolation in the Arctic. http://2.bp.blogspot.com/-k_S7N0VlMRg/UH4RNvJ3cjI/AAAAAAAAFjk/lqjQhGqLWOk/s1600/insolation_latitude.gif It is clear that what drives the seasonal cycle of sea ice volume is insolation. Looking at the years listed on the graph, years in the past are deeper blue, lighter blue in recent years. Now take, say, 20 June, which is the difference between 11 and 20 June. Within that band of blues are all years from 1979 to 2014, you can see that from 1979 to 2014 volume loss in the period 11 to 20 June has increased. Early melt season losses have increased significntly, but later in the summer volume loss has decreased. My point is that insolation drives the annual cycle. Things like albedo affect the amount of sunlight absorbed, but the changes these factors have are small. Note that what drives the long term trend of volume loss need not necessarily be linked to what drives the seasonal volume loss. The red plot was intended to show a possible scenario where by an April volume of 19.3k km^3 could be reduced to zero by September. Yes, rapid melt out of peripheral ice floes happens. It does happen on a large scale in models, in the PIOMAS model when ice in April is thinned by 1m across the pack the Arctic Ocean is virtually sea ice free by the end of July. But at present with ice thickness of around 2m for much of the pack (more in the coming winter) the rate of progression of melt is limited by available insolation and the mass of ice that needs to be melted to give largescale ice free conditions early enough for the Central Arctic to have time to experience large extent loss.
Toggle Commented Aug 6, 2014 on Poof, it's gone at Arctic Sea Ice
Thanks Epiphyte, and thanks to Neven for re-blogging. I don't see this as having any impact on the fate of the whole pack though, such rapid disappearances are not uncommon. PIOMAS volume holds no surprises, now above 2007.
Toggle Commented Aug 5, 2014 on Poof, it's gone at Arctic Sea Ice
Steve, Basically it's because first year ice can reform quickly in the winter, whereas it takes years for MYI (multi-year ice) to 'bounce back' from losses. Recent PIOMAS maximum volumes have been about the volume one would expect for a pack with an average thickness of around 2m. I think the previous volume loss trend, which was due to loss of MYI volume, has come to an end. We now have a pack with a residual of MYI that is mainly first year ice. Winter volume losses will level out, summer volume loss, and hence extent/area losses will level out too, I suspect.
Toggle Commented Aug 3, 2014 on ASI 2014 update 6: slow times at Arctic Sea Ice
Pete Williamson, It will take many more years for ice state to return to pre-2007 conditions. 2007 removed a lot of thick ice. Concentrating on extent and area at the expense of volume isn't using all the available information. John Christensen, The AMO might have a role in ice retreat, especially in the Atlantic sector. However the AMO index proper has the signature of AGW driven ocean warming removed. Once that is done one has to wonder whether the the AMO has a role or if it is AGW driven ocean warming that has had a role. http://www.cgd.ucar.edu/cas/catalog/climind/AMO.html Using data from this site: http://www.esrl.noaa.gov/psd/data/timeseries/AMO/ I have plotted the 'detrended' AMO and the raw Kaplan SSTs. https://farm4.staticflickr.com/3895/14831109493_bdccf6c642_o.png The AMO did cross zero on the upslope around 1995, and has crossed zero on the down slope this year, so could be taken as being the start and end of a limited period of volume loss. However Kaplan SST suggests that if SSTs are the issue then they cannot explain the last two years of sea ice as a phenomenon of the declining AMO - they remain historically high! Furthermore the start of the recent period of volume loss may have nothing whatsoever to do with the AMO. I have blogged earlier this year about what caused the decline in volume in the PIOMAS model. http://dosbat.blogspot.co.uk/2014/03/what-caused-volume-loss-in-piomas.html Taking the interannual difference between successive september NSIDC extents and plotting together with the cumulative sum of the differences shows that the period where declines in extent outweighed recovery started in the mid 1990s. http://farm3.staticflickr.com/2890/13293791045_5ce2e28c53_o.png However Lindsay & Zhang put forward a theory that this period of decline after the mid 1990s was due to a three stage process. https://farm4.staticflickr.com/3823/13335331354_8b46010cd9_o.png With the trigger, after decades of early thinning, being the PDO and AO indices, and ice albedo feedback taking hold thereafter. I've argued recently that we're at an inflection in winter volume because first year ice growth is taking over from multi-year ice volume loss. If I am correct the reultant steadying of winter and summer volume loss is bound to be misdiagnosed as being due to the AMO going negative. Ho hum. :)
Toggle Commented Aug 2, 2014 on ASI 2014 update 6: slow times at Arctic Sea Ice
Osteopop, Yet during that ten years we have seen 2007 and 2012 both record crashes in summer extent - yet you prefer to ignore them. Now based on two year's weather driven behaviour of the pack you claim we have turned a corner and the ice is recovering? We have various indices and only CO2 shows a linear relationship with annual average ice extent. Any moderately educated person would immediately put CO2 at the tope of the list of prospective causal drivers of the decline. They would then look at the prospects for CO2 decreasing and conclude that the prospects of ice declining are good as long as CO2 continues to increase. Beyond that is a lot of detail, which is why I directed you to the models, which are tools for encompassing the detail. Yes there is an inflection ongoing (IMO), but it will not lead to a recovery of sea ice. There's been an ongoing and lengthy discussion about this over at the forum. Other factors have predictive values on various timescales. But the root cause of the long term decline in sea ice is anthropogenic warming, which is largely driven by CO2 - the largest single factor. The only bias going on here is in your thinking. My thinking remains fluid, and able to be changed based on new evidence - as my recent claim of an inflection in volume loss shows.
Toggle Commented Jul 29, 2014 on ASI 2014 update 5: low times at Arctic Sea Ice
Osteopop said: "The area had one of the colders winters in memory, and plenty of time to build thickness." NCEP/NCAR JFM average surface air temperature for a grid box 60N to 80N, 240E to 300E, covering the Canadian Arctic Archipelago. https://farm6.staticflickr.com/5558/14766811873_a2d6acf6a3_o.png So only one of the coldest years in living memory if you're under 16 years old. Meanwhile, for the whole Arctic (north of 65degN), in NCEP/NCAR 2014 was the warmest JFM winter since 1948. https://farm4.staticflickr.com/3881/14746632382_7318c09036_o.png So how thick was the ice in April 2014? According to PIOMAS it started off about the same as the last four years. http://3.bp.blogspot.com/-8YO1VrUPxaU/U9KJ3zBezSI/AAAAAAAAAu0/97tSS8cRIjM/s1600/CAA.png The CAA is only just entering the period where, historically, loss rates pick up. I have no opinion on whether the NW passage will open up this year.
Steve, Yep, I've been using them too, they are excellent.
Toggle Commented Jul 21, 2014 on ASI 2014 update 5: low times at Arctic Sea Ice
Neven, We'll know by late August whether the MYI transport into Beaufort/Chukchi has impeded ice melt - I'm in no position to correct you or anyone else on that point at the moment. :) I've said it before, but it's worth repeating. Anyone curious about the effects of the warming of the North Atlantic on the Barents Sea need only compare historic sea ice early the last century with recent summer levels. http://brunnur.vedur.is/pub/trausti/Iskort/Jpg/ The decline really is remarkable.
Toggle Commented Jul 15, 2014 on ASI 2014 update 5: low times at Arctic Sea Ice
Apropos the claim "We have seen 18 years without a rise in global mean surface temperature." It has moved me to publish a post I wrote some time ago. http://dosbat.blogspot.co.uk/2014/07/that-no-warming-since-1998-bollocks-meme.html
Toggle Commented Jul 15, 2014 on ASI 2014 update 5: low times at Arctic Sea Ice
Correction, end of penultimate paragraph. "without anthropogenic forcings (CO2 being the largest single such forcing), CO2 does not decline" should read "without anthropogenic forcings (CO2 being the largest single such forcing), sea ice does not decline"
Toggle Commented Jul 15, 2014 on ASI 2014 update 5: low times at Arctic Sea Ice
Osteopop, "It also seems obvious that we have turned some sort of corner when it comes to Arctic sea ice, since we have seen the winter maximum stall already, and now the summer minimum has started fluctuating wildly and bottoming out." There is a good reason why the winter volume maximum has stalled: Most of the loss of volume has come from loss of multi year ice (thinning). That process is now coming to an end, and winter maximum volume within the Arctic Ocean is becoming dominated by first year ice, with winter volume tending towards that dictated by the thermodynamic thickening of first year ice. More here: http://dosbat.blogspot.co.uk/2014/04/what-is-future-of-arctic-sea-ice-part-2.html "There's unfortunately no one number which has predictive value, there are too many variables, but I believe that at some point we will be able to find some natural relationships which have predictive skill when it comes to sea ice over the long term." This is not correct. Notz & Marotzke looked at four possible indices that might affect sea ice loss. http://farm8.staticflickr.com/7058/6993704168_03751afb94_o.jpg In a similar manner I have plotted the AMO and sea ice extent: http://farm8.staticflickr.com/7081/7142592477_ed4594dbd9_o.jpg Changes in irradiance (from the Sun) are in the wrong direction, the clustering suggests a relationship of more sunlight leading more ice, this is obviously incorrect. The Atlantic Multidecadal Oscillation (AMO), Pacific Decadal Oscillation (PDO) and Arctic Oscillation (AO) show little relationship. Other indices are discussed in Notz & Marotzke and are not likely candidates. However CO2's correlation is good as can be seen in the scatter plot. This doesn't prove that CO2 is causing the sea ice loss, however it does direct the intelligent, open minded, invesigator to put CO2 at the top of the list of possible causal factors. Models, despite their problems with regards sea ice, show a consitent pattern across a variety of different models. http://2.bp.blogspot.com/-yUAq3OcQwfE/Uy34AqBls_I/AAAAAAAAAP0/ndGeBbkh2vM/s1600/WangOverland+2012.JPG In that graphic the red trace is observed September sea ice extent. Coloured traces are model projections of sea ice loss with natural and anthropogenic factors. In each panel the grey traces are projections with natural forcings. Despite the differences between the various models the common qualitative conclusion is that without anthropogenic forcings (CO2 being the largest single such forcing), CO2 does not decline, with anthropogenic forcings the sea ice recedes. The indidual causal pathways through which anthropogenic global warming affects sea ice are complex. However the scatter plot relationship, and the results of numerical models present a clear case that it is humanity that is causing the decline of sea ice. Our CO2 emissions are not going to decline, sea ice is not going to recover. As others have pointed out, you could have played the same game in 2008 and 2009, 2010, 2011 and 2012 would have proven you wrong.
Toggle Commented Jul 15, 2014 on ASI 2014 update 5: low times at Arctic Sea Ice
Osteopop, Crucial to any claim of a continuing recovery of sea ice is understanding what caused it to decline. What do you think caused it to decline?
Toggle Commented Jul 14, 2014 on ASI 2014 update 5: low times at Arctic Sea Ice
k eotw, A large element is likely to be differences in concentration. In 2010 compactness of the pack was far lower than this year.
Toggle Commented Jul 13, 2014 on ASI 2014 update 5: low times at Arctic Sea Ice
PIOMAS data is out, my prediction for 2014 has leapt up. It is now 4.6 to 5.1M km^2 September sea ice extent. Some quick reasoning is given here: http://forum.arctic-sea-ice.net/index.php/topic,917.msg30899.html#msg30899
Toggle Commented Jul 7, 2014 on ASI 2014 update 4: high times at Arctic Sea Ice
John Christensen, Average summer SLP anomaly 2007 to 2012 (this overlaps the anomaly period but the same calculation, without overlapping makes a similar pattern). https://farm4.staticflickr.com/3880/14313435867_40a8fc5a6a_o.png Average summer SLP anomaly for 2013. https://farm6.staticflickr.com/5077/14313435857_2d7ff333f1_o.png Average SLP anomaly for 18 June to 3 July 2014. https://farm4.staticflickr.com/3883/14409258310_197b3156e8_o.gif This year, after the shift on 18 June, is looking like another summer typical of 2007 to 2012. Where it is not typical is over the North Atlantic through to Europe, we'll see how that shapes up, but so far 500mb geopotential height has not been unusually large over Greenland. And what has been happening from 2007 to 2012 is not the Arctic Oscillation / North Atlantic Oscillation. It just looks like it because the loading pattern picks up similar features, notably the high over the Arctic. Here is the summer (JJA) SLP anomaly for years prior to 2007 with an AO index of less than -0.2. https://farm3.staticflickr.com/2933/14409382649_04e3225f57_o.png Here is the summer SLP anomaly for years after 2007 with an AO index of less than -0.2. https://farm3.staticflickr.com/2940/14409359788_af73750daa_o.png Note the lack of deep low tendency over Asia in the post 2007 data, note the close ring of responding lows around the Arctic high. Note the more intense shift over Greenland and the deeper low tendecy over the UK and Western Europe post 2007. That UK low is due to the jet being steered by the Greenland ridging that has been anomalous in recent years. James Screen has examined European summer rainfall and compared the atmospheric pattern associated with wet European summers and loss of sea ice. In the following graphic 'observed' is the pattern due to wet summers, 'simulated' is the pattern simulated in response to loss of sea ice. http://farm6.staticflickr.com/5550/10579354246_c9e27915a6_o.png If you didn't know which was which could you tell, I couldn't. Image from this paper. http://iopscience.iop.org/1748-9326/8/4/044015 I mentioned anomalous Greenland ridging, this can be seen in 500mb Greenland geopotential height. https://farm9.staticflickr.com/8265/10230835075_3a4e20f2df_o.png Here is the monthly correlation of gridded SLP north of 20degN with the summer pattern for average SLP summer (JJA) 2007 to 2012, the 'summer pattern correlation'. https://farm8.staticflickr.com/7411/10230252184_d85e7d9bc5_o.png And here's a comparison of summer pattern correlation and summer AO index. https://farm8.staticflickr.com/7394/10230252234_678aa34280_o.png The two are not the same. I maintain that we have a new pattern that looks like the AO, but is not, and is due to sea ice loss.
Toggle Commented Jul 7, 2014 on ASI 2014 update 4: high times at Arctic Sea Ice
Henry, I used May temperatures north of 80 because most people here use the DMI Arctic Temperature plots, and they're north of 80 too. Here's a plot of temperature north of 70 (grid area weighted), which covers the Arctic Ocean, but takes in more of the surrounnding land. https://farm6.staticflickr.com/5077/14593659054_10dbd96e14_o.png Plot from here: http://www.esrl.noaa.gov/psd/cgi-bin/data/timeseries/timeseries1.pl Your calculation with regards losses from a date to the end of the season applied to the same date this year is something I keep an eye on. However as I've said on the forum several times: The period of largest summer losses is 2007 to 2013 - that's the dataset we can reasonably draw comparison with for the 2014 melt season, due to the massive changes since 2007. This is a short period and I am far from convinced that it shows us all of the potential variability of the thinned ice after the volume losses of 2007 and 2010. My spreadsheet used for the SIPN prediction I made in June, using May PIOMAS data, is now ready for the July prediction, using June PIOMAS data. If I assume that in 2014 the May/June PIOMAS volume loss is the same as in 2013, the resulting prediction is: Upper.. 4.848 Central 4.311 Lower.. 3.774 And "<" indicates previous minimae within the prediction bounds. 2007, 4.300 < 2008, 4.730 < 2009, 5.390 2010, 4.930 2011, 4.630 < 2012, 3.630 2013, 5.350 Now that is only a prediction, it suffers from the same issue of the limited number of years available (post 2007) as does the method of subtracting previous summer losses from current extent/area. The advantage I claim for my prediction technique, limited though that may be, is that it use volume. Volume/thickness governing the effectiveness with which open water can be produced by a given thinning during the melt season. I've only used 2007 to 2012 data to 'train' the method, using 1979 to 2013 data to derive the basic relationship between volume early in the season and September extent. And in all the years 2007 to 2012 the hundcasts are successful - by definition because I've used the stats for the 2007 to 2012 period to 'train' the method. It may turn out that 2014 is another 'muted melt' year like 2013. But the weather (SLP) so far has been close to the 2007 to 2012 average, not like 2013.
Toggle Commented Jul 7, 2014 on ASI 2014 update 4: high times at Arctic Sea Ice
Sorry Henry, Another clarification: "I still think that reading too much into the season from June state isn't sound" should have been written as: "I still think that reading too much into the season from June state extent or area isn't sound"
Toggle Commented Jul 6, 2014 on ASI 2014 update 4: high times at Arctic Sea Ice
Henry, May was just as cool in 2014 as in 2013. https://farm3.staticflickr.com/2915/14582988864_ddef37ed9b_o.png Yet as in 2013 PIOMAS volume anomalies dropped. http://3.bp.blogspot.com/-yfNN9im-DaE/U5M_31LgNSI/AAAAAAAAAc4/VxQB-8r3qdk/s1600/PIOMAS+Spring+Vol.png That being the spring volume loss, which has started to be more aggressive after the 2010 volume loss. That this spring loss happened in 2013 despite much cooler temperatures indicates that ice state is the dominant factor. In this blog post... http://dosbat.blogspot.co.uk/2014/01/post-2007-summer-melts-ice-or-atmosphere.html I have looked at ice state and atmosphere as candidates for the increase in seasonal area/extent loss since 2007. Despite the change of weather in 2013, losses between months were still predominantly greater than the 1980 to 1999 average (as seen in anomalies from that average). CT Area. http://2.bp.blogspot.com/-PJnjxkd-QJo/Ut1843a7YCI/AAAAAAAAALM/e9SO8ZD9pIE/s1600/CT+Area+IM+Anoms.png NSIDC Extent. http://4.bp.blogspot.com/-k-gNlEROWRo/Ut1840XJqXI/AAAAAAAAALQ/FY8wMUCjYWw/s1600/NSIDC+Ext+IM+Anoms.png Which implies that while 2013 had an effect, ice state in the post 2007 situation was the dominant factor. Looking at Wipneus's area and extent data based on NSIDC gridded concentration, I think people (not just you) are expecting too much of the ESS in June. For the East Siberian Sea (ESS), the 1980 to 1999 average loss of extent from 1 June to 30 June was 10.45k km^2. 2014 saw an increase, not a loss, of 9.03k km^2, whereas, for example 2012 had a loss of 12.3k km^3. For comparison, average July losses for the ESS from 1980 to 1999 were 150k km^2, even 2013 lost 212k km^2, 2012 lost 274k km^2. In 2007 July saw a loss of 618k km^2. So I think it is too early to draw conclusions about the rest of the season based on June extent or area losses in the ESS. Especially in view of the May ice thickness from the ESS through to the Beaufort Sea. It is worth pointing out that while June 2014 losses in Kara are small (73k km^2 vs avg loss from 2010 to 2013 of 342k km^2), next door in Laptev June losses have been the greatest on record (since 1979), at 150k km^2 they dwarf the 50k km^2 losses in June of 2012. In a nutshell, I still think that reading too much into the season from June state isn't sound, and that we will see ice state play a strong role this melt season as in 2011 and 2012. Neither of those years was really good melt weather. Yet 2011 was a tie with 2007 (considering all indices of extent & area), and 2012 was a large new record. PIOMAS will give an indication, but without that June data - I expect thinner ice this year to give enhanced ice area & extent loss over what one would expect for the pre 2010 period. I guess I'm betting on a melt rate similar to 2011 and 2012. If I apply the day to day losses of extent in those years from 4 July 2014 and caculate the minimum, applying 2011 gives a minimum of 4.33M km^2, applying 2012 gives a minimum of 3.71M km^2. This rules out 2013. 2007 and 2011 are within that range, and 2008 and 2010 are close to the upper bound. 2012 is close to the lower bound - but I suspect (the literature is somewhat split on this) that the August Cyclone had a role in the 2012 low being as low as it was. So I'm saying that something in the region of 2007 or 2011 is very likely this year, as long as the weather doesn't turn 2013ish. I don't expect that to happen, I think this year's summer average SLP will be more like the 2007 to 2012 average than 2013. Sorry for another long winded reply.
Toggle Commented Jul 6, 2014 on ASI 2014 update 4: high times at Arctic Sea Ice
Sorry Henry, When I said 'impossible to call' I should have clarified. Without PIOMAS data and without knowing whether the highs (that are predicted to re-assert will continue all summer), I am finding it impossible to say whether 2012 is totally unobtainable. As can be seen from my earlier comment - I don't think a re-run of 2013 is at all a realistic prospect.
Toggle Commented Jul 5, 2014 on ASI 2014 update 4: high times at Arctic Sea Ice
Henry1, I'm finding it impossible to call right now. In the Arctic Ocean, compaction (=Area/Extent) has shot up as area has failed to fall but extent has fallen over the last few weeks. This cannot be maintained, compaction falls in the summer. Losses of extent are not unusual for recent years in most of the Arctic Ocean in June, however loss of area has been more normal for the 1980 to 1999 period. It is in July that greatest extent losses occur, and losses in June imply high losses in July - in line with recent years. The extremely good melt weather has backed off over the last few days, reducing extent losses. However GFS and ECMWF both show the strong highs that have led to high losses from 18 June to 30 June returning. Limiting consideration to the immediate vicinity of the Arctic Ocean, 18 to 30 June has been quite reminiscent of 2007, more like that year than any since. A lot depends on how much thinning has happened in this June. May thickness (PIOMAS) in Beaufort, Chukchi, and the East Siberian Sea was of the order of 50cm down from May 2012 and May 2013. Add the fact that the weather is far more conducive to melt than it was in 2013, and seems likely to remain so for at least another week (it may become the pattern typical of July and August), and I think concluding that area failing to drop below past normals is risky. My 2014 CT Area prediction was made using the long term average losses from June 20 to minimum and the deviation from that average for the 2007 to 2012 period. It worked last year, against the expectations of many. This year I suspect it may fail. If I had to bet on it I'd say that Area will start to drop faster than the bseline average (I use 1980 to 1999), as we get further into July. My heuristic prediction for CT Area is 3.3 to 2.9M km^2, I've lowered the bottom end of the range because current information suggests to me that 2014 could easily match 2007 and 2011. Weather-wise this is not 2013, and CT Area anomalies continuing level (as they have been for the last week) suggests a 2013 finish to the season. This is not, in my opinion, realistic.
Toggle Commented Jul 5, 2014 on ASI 2014 update 4: high times at Arctic Sea Ice
Rob, I've done a blog post on the spring volume loss in PIOMAS back in February this year. http://dosbat.blogspot.co.uk/2014/02/the-piomas-spring-volume-loss.html I didn't manage to pin down the exact cause, but it seems to be associated with the thinning of ice and movement from ice of 2 to 3m thick into the 1 to 2m thickness band. Most regions in the Arctic Ocean participate, but the Central Arctic region is the greatest single contributor. Crandles pointed out that in an SIPN presentation Dr Blanchard Wrigglesworth shows results from PIOMAS when April thickness is artificially thinned by 1m. http://www.arcus.org/sipn/meetings/workshops/april-2014 You'll need day 1 morning 1 from 57min onwards. What happens in PIOMAS is that when current April ice thickness is thinned by 1m, the ice rapidly retreats such that by the end of July the only remaining ice is the residual thick multi year ice off the northern coast of the Canadian Arctic Archipelago. This is then slower to melt, the resulting shape in terms of anomalies would be similar to what is being observed now, with an aggressive spring volume loss, and after about 21 June (solstice) anomalies rise as the late summer losses are similar to the past climatology. However in the experiment where ice is thinned by 1m the spring volume loss must be much more aggressive as a proportion of total volume. Basically thinner ice melts faster in the spring than thick ice. The exact reason for this - I don't know. However the increase in June NSIDC Extent losses after 2010 seems to me to imply that what is happening in PIOMAS is real.
Toggle Commented Jul 5, 2014 on ASI 2014 update 4: high times at Arctic Sea Ice
http://barentsobserver.com/en/energy/2014/06/extreme-ice-conditions-future-oil-areas-18-06 Errant ) and . on the link above. Thanks for the info Bibken.
Toggle Commented Jul 4, 2014 on ASI 2014 update 4: high times at Arctic Sea Ice
Well it's not even checkmate with June numbers, the weather could shift. I won't say this is interesting - it's just the sort of thing that interests me. ;) Using PIOMAS gridded data. Arctic Ocean Sea Ice volume loss from May to June. 1980 to 1999 average loss is 1.8k km^3, from 2007 to 2009 it's 2.48k km^3, from 2010 to 2013 it's 3.63k km^3. Even 2013 had a loss of 3.06k km^3 from May to June. 2012 lost an eyewatering 4.17k km^3!! June 2013 average SLP was more like early June 2014. http://farm8.staticflickr.com/7407/9194158060_57c1543648_o.gif My guess is that June 2014 will have lost more than June 2013. If I put 3k km^3 loss off May's volume into my prediction method for NSIDC September average extent, I get 4.89 to 3.81M km^2. That rules out 2012, 2013, and argues against 2009 and 2010, but includes but includes 2007, 2008, and 2011.* Fingers crossed for good melt weather and a June loss in the Arctic Ocean of over that for 2013. *As I've pointed out already on the forum, I doubt that we have seen the full range of possible outcomes of weather acting on thinner ice since 2007 and then 2010. I suspect that 2013 shows us the higher limit but havve doubts that 2012 really shows us the lower limit of what is possible.
Toggle Commented Jul 4, 2014 on ASI 2014 update 4: high times at Arctic Sea Ice