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Chris Reynolds
UK
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It's not despair Kevin, it's pragmatism. And no, don't give up, I rarely voice this opinion because I don't want to get in the way of those trying to work for change. So I just keep my doubts to myself, most of the time.
Toggle Commented 7 days ago on PIOMAS April 2014 at Arctic Sea Ice
John, I couldn't put it better than Nick Cohen. http://www.theguardian.com/commentisfree/2014/mar/22/climate-change-deniers-have-won-global-warming And to paraphrase Slartibartfast: "Perhaps I'm old and tired, but I think that the chances of 'getting people to act on AGW' are so absurdly remote that the only thing to do is to say, "Hang the sense of it," and keep yourself busy." Unlike Slartibartfast, I am happy. I'd rather be right than happy, but it's good that the two states are not mutually exclusive :)
Toggle Commented 7 days ago on PIOMAS April 2014 at Arctic Sea Ice
John, PIOMAS doesn't explicitly model FYI and MYI, and doesn't seem to be picking up the MYI being shown as being exported into Beaufort and Chukchi by the Drift Age Model (DAM). This may however be because the MYI isn't that thick, so it might not prove the impediment to melt I have said I expect. HYCOM is showing the MYI export shown in the DAM, but it's showing seriously thick ice there. Comparison with IceBridge would be best, but at present I'm not convinced by this thick ice shown in HYCOM. I think for the grid cell average thickness is not at 3.5m to 4m thick in Beaufort, I think PIOMAS is more likely to be on the nail. But... HYCOM is intended for shipping isn't it? So do those running it intend it to be high biassed in terms of thickness to stop ice breakers running into 'briar patches' of ice too thick for them to handle. Just a WAG. It is hard to get where people are coming from with 'good melt' and 'bad melt'. I've said before I don't get why some follow a system in a death spiral and keep rooting for ice survival. 2013 was an interesting experiment, the experiment is over and the volume pulse lasted a lot shorter than I'd dreamt possible - the ice keeps proving me wrong. But I still find big awe-inspiring crashes more exciting. :) Jim, Check out ASCAT too. http://manati.star.nesdis.noaa.gov/ascat_images/ice_image/msfa-NHe-a-2014098.sir.gif The spur of whiter MYI is visible in Beaufort, but there are cracks in it and it's got nowhere near the brightness (high radar return) as the band off the CAA. That suggests it's dispersed - given that it came from the mass of white off the CAA its dielectric properties shouldn't have changed. More images here: http://manati.star.nesdis.noaa.gov/ascat_images/ice_image/
Toggle Commented Apr 9, 2014 on PIOMAS April 2014 at Arctic Sea Ice
Regional breakdowns of PIOMAS gridded data and thickness distributions for Beaufort/ESS/Central here: http://dosbat.blogspot.co.uk/2014/04/piomas-march-2014.html
Toggle Commented Apr 8, 2014 on PIOMAS April 2014 at Arctic Sea Ice
Crandles, I need to re-read that paper. "From 2004 onward, and in particular in 2006 and 2007, the remaining oldest ice has been confined to a small portion of the Arctic (regions 6 – 8); essentially a relict of the perennial ice cover of 20 years ago." That throws interesting light on the continuing decline of volume in the Central region over recent years.
Toggle Commented Apr 7, 2014 on Research for a novel at Arctic Sea Ice
Sorry, as already pointed out, something left at the pole wouldn't stay there. Prior to the opening of large amounts of open water in Beaufort/Chukchi leading to a breakdown of ice circulation around the Beaufort Gyre typical transit times around the Gyre were 4 to 5 years, add another year for movement to the north of Greenland, that's six years. For the 200 years from 1880 to 2000 that's 33 loops with the object excaping being ejected through the Fram Strait. The best bet for something being found on the pole in recent years that had been deposited in the wider Arctic region would be a floating object down a siberian river, or an object trapped in surface permafrost on the Alaskan/Siberian coast being released with permafrost melt and wave erosion. Or an object on a glacier or land fast ice off the Arctic coast of the islands of the Canadian Arctic Archipelago, or Northern Greenland. Indeed with regards permafrost, you could imagine something bouyant left in the stone age being discovered over a recent winter in the N Pole camp. The mechanism is rather determined by what is to be found at the pole.
Toggle Commented Apr 7, 2014 on Research for a novel at Arctic Sea Ice
Jai, I should have said 'hindcast' - forecasting past years to test the method. The ten day PIOMAS differences is simply calculated from the main PIOMAS daily series. It's just V(n) - V(n-9) for ten day increments in n. You could work with the difference between current day and previous and it will produce a noisier version of the same curve. Working with monthly data is fine, it has the advantage of reducing short term noise. Daily temperature is available from NCEP/NCAR but it's in netcdf format. I use Panoply, from which csv copies of data can be obtained. But daily data means that's not a very efficient way of working. I don't know which programming langauges have ready made netcdf extraction routines. Now I'm not as tired as last night I've put my finger on why those difference plots seemed relevant. It's the relatively small size of interannual variation compared to the bulk of energy going into the ice. Also various factors go into those small changes: Temperature of the atmosphere and ocean, cloud cover, ice albedo. Bringing ice movement back into the equation you've got convergence/divergence of the pack, and ice export (Fram/Bering but also transport by the Beafort Gyre).
Toggle Commented Apr 5, 2014 on Forecast me not at Arctic Sea Ice
Jai, So in this plot: http://oi61.tinypic.com/35c3g92.jpg Am I correct in interpreting the blue line as your method's 'prediction'? BTW - you are careful to remove trends before obtaining correlations aren't you? If you don't do that you'll get false high correlations due to trends in synch and counter synch. Some chap at the forum was getting really high correlations for predictions using volume, and he was just matching the extent and volume declining together. This graph shows PIOMAS volume changes in ten day increments throughout the year. http://farm8.staticflickr.com/7446/9703421624_eb542d20ee_o.png Neglecting transport for a moment and considering it as energy - it's apparent why the volume cycle changes as it does, it's almost in lockstep with insolation. http://2.bp.blogspot.com/-k_S7N0VlMRg/UH4RNvJ3cjI/AAAAAAAAFjk/lqjQhGqLWOk/s1600/insolation_latitude.gif The lag is slight, with sea ice volume loss happening only a couple of weeks after peak insolation. Looking more closely at each of the ten day increments on that graph each year can be seen. What can also be appreciated is that mid season the interannual variation is small compared to the overall heat flux going into melting ice. It seems somehow relevant to me... Nightvid, I Agree.
Toggle Commented Apr 4, 2014 on Forecast me not at Arctic Sea Ice
Sofouuk, I've been watching this because I think it could be comparable to 2010. The similar export of MYI in 2010 was a large (possibly the main) factor in the 2010 volume loss event.
Toggle Commented Apr 3, 2014 on Forecast me not at Arctic Sea Ice
Jai, Why not try removing the trend in sea ice extent? We know that the trend in sea ice extent/area is strongly related to the trend in volume, as indicated by the relationship between volume and extent at minimum: http://2.bp.blogspot.com/-TA4qFR0WL1A/Uy3G1FUQS6I/AAAAAAAAAPU/VSrpuRhbE-Q/s1600/Extent+&+Vol.png This is to be expected because due to open water formation efficiency it's the volume loss that is the driver of sea ice loss. So surely what you need to be doing is looking at the residuals from the trend in sea ice loss. i.e. what causes the variations from the trend, not what causes the trend itself. As I understand it, that's where to look for improving seasonal prediction.
Toggle Commented Apr 3, 2014 on Forecast me not at Arctic Sea Ice
Jai, Sorry forgot to add - I know of no easily useable daily temperature data, unless you want to use netcdf.
Toggle Commented Apr 2, 2014 on Forecast me not at Arctic Sea Ice
Jai, NCEP/NCAR temperature series by month can be obtained here: http://www.esrl.noaa.gov/psd/cgi-bin/data/timeseries/timeseries1.pl NCEP NCAR temperature is a reasonable reflection of the actual temperature as measured by GISS for example. Select: Air Temp Surface Latitude? 70 to 90 Longitude? 0 to 240 * Monthly Area weight grids - YES * Raw Data You can choose a different region, like north of 80 degN. I chose 0 to 240 because that leaves out the land temperatures of northern Greenland and the CAA. Give it a few seconds and that should give you tabulated data by month. I assume you know how to calculate the anomalies, just in case: Say you want to use the GISS baseline of 1951 to 1980. for each month calculate the average temperature for the period 1951 to 1980, then each months temperature is an anomaly of temperature when the monthly average is subtracted from the figure for each year, i.e. Anomaly = MonthValue - BaselineAverage.
Toggle Commented Apr 2, 2014 on Forecast me not at Arctic Sea Ice
Jim (econnexus), I've got similar references in papers. PIOMAS data can help, for example I still think the extensive late survival of ice in Chukchi/ESS in 2010 was due to the large export of MYI earlier that year from the central Arctic region. But I've been unable to get further than such post hoc interpretations. When I try numeric methods to improve predictions I find the improvements are not substantial, e.g. an R2 going from (IIRC) roughly 0.8 to 0.85.
Toggle Commented Apr 2, 2014 on Forecast me not at Arctic Sea Ice
Ghoti, 2013 was the perfect example of weather. PIOMAS volume 'jumped' relative to 2012 in May due to weather and didn't fall back until this February - due to weather. Up until May 2013 sea ice thickness was such that with a re-run of 2012's weather it's hard to see how we wouldn't have had a repeat of 2012. Jai, Sorry, you've lost me with that stuff you're doing. There are mathematical techniques for extracting relative roles of various factors - but it looks like rather a lot of work to me at present. Liam, Agreed, or perhaps more intuitively - for a given average thinning from April to September (say 2m), the closer average April thickness gets to that average thinning the easier open water is formed, and the greater weather impacts that alter seasonal thinning can have on open water formation. Anyone interested... I've been playing around with PIOMAS main daily volume series. Taking the interannual volume changes from year to year for the daily volume minimum from 2000 to 2013 I can make a series of yearly volume changes. If I make a guestimate of 2014 daily minimum volume of say 4.120k km^3 (might be lower, might be higher) I can then take random choices from the list of interannual volume changes from 2000 to 2013, and use them to make random series of volume loss from 2015 to 2050. So I now have a series of artificial volume loss trajectories, based on the past volume loss behaviour of recent years. I can then work out when in each of the 25,000 artificial series the first occurence of zero volume occurs. So I tally how often this happens for a single year, to get an occurrence distribution of when the first time volume reaches zero. This is shown in the graph below. https://farm6.staticflickr.com/5581/13586618575_d71e1093f3_o.png Of course this tells us nothing about whether future year on year volume losses will be typically greater, or less, than in the period from 2000 to 2013. What it is intended to do is to answer the following question: If the interannual volume losses can be taken as indicative of the net energy gain of the ice/ocean system, if this net gain persists into the future - how long until the volume falls to zero? In the spirit of that question, if I leave out 2007, 2010, and 2012 as not being indicative of the net energy gain, but outliers due to special circumstances then the occurrence distribution of when the first time volume reaches zero is as follows: https://farm8.staticflickr.com/7029/13587126243_6051fdaee5_o.png With a slower decline to zero in the 2020s, rather than a peak around 2020. For what it's worth I find the length of the tail unconvincing due to my interpretation of volume loss implying net energy gain in the ice/ocean system.
Toggle Commented Apr 2, 2014 on Forecast me not at Arctic Sea Ice
Just caught a bit of Dr Zhang talking about using NCEP CFS to make PIOMAS predict - interesting.
Toggle Commented Apr 1, 2014 on Forecast me not at Arctic Sea Ice
Jai, there may be something to your idea of warm winters preceding crashes, but it's far from the only factor so it's taken a bit of fiddling to bring out a link. https://farm8.staticflickr.com/7454/13566424623_4bd64e76fb_o.png To make that plot I've taken the interannual differences for NSIDC Extent September average extent. I've also calculated NCEP/NCAR Jan/Feb (JF) average temperature anomaly north of 80degN, and Jan/Feb/Mar (JFM) average temperature anomaly north of 80degN. Anomalies are relative to the GISS baseline of 1951 to 1980. The horizontal axis of the plot is the sequence of values for each year's extent difference. The vertical axis is of temperature anomaly. The most negative interannual losses - typically associated with new record years (left of the plot) are associated with large temperature anomalies, but not all the time. Hence the range of temperature increases for more negative interannual extent losses. Whereas at the right side of the graph - gains from the previous year the variance is more restrained. As I say, other factors are clearly at play, 4 out of 5 of the largest peaks in late winter temperature are associated with negative interannual extent changes - but this may be at least partly because of the recent warming associated with a period of net ice loss. To help the interested decide if there's anything to it, here's a time series: https://farm4.staticflickr.com/3740/13566778813_5b82c76575_o.png *** With regards prediction. I think it's helpful to use the trend, with what is deemed an appropriate function (exponential, quadratic, etc) as the baseline and see if that can be improved upon. The initial thickness in April, whether for regions or the whole PIOMAS domain is, in my experience, little better a predictor than the best-fit trend. i.e. the initial thickness mainly carries information about the trend, not the deviation from the trend. Initial thickness do not seem to deviate in any given year such that they strongly influence deviation from the trend. I tend to agree with Dr Stroeve that melt season weather is a major (the major?) factor in determining the deviation from the trend.
Toggle Commented Apr 1, 2014 on Forecast me not at Arctic Sea Ice
Jai, I might be foolish on this issue, and I accept I could be wrong. As far as I am aware there is no data on sediment temperatures during MIS11. The only attainable option would be modelling. In doing some digging amongst the papers I have I find that temperature of the upper ESS sediment is already at just below zero. See Shakhova 2013, figure 3: http://www.see.ed.ac.uk/~shs/Methane/Shakhova%202013.pdf If we take the black trace as indicative of temperatures before the inundation at the start of the holocene, and the red as conditions now. It seems the warming has already happened, in under 10,000 years. However Romanovskii 2004 shows (fig 3) that the relic permafrost underlying Shakohva et al's bore hole is much deeper. http://lin.irk.ru/pdf/6679.pdf That also indicates that their model gives a decline in the depth of the zero isotherm during MIS11. As I understand it, it is the fate of the relic permafrost that determines the possibility of a massive methane release (on short time scales). I am a bit rusty on methane, I've not read much about it since writing a series of blog posts on the subject. So I may be missing something or mis-remembering the papers I've just cited. With regards whether there was a methane emission during the MIS11: We can look to Greenland ice core records, I've only managed to find this dataset: ftp://ftp.ncdc.noaa.gov/pub/data/paleo/icecore/greenland/summit/gisp2/gases/gispch4.txt That only goes back to 110k years ago. MIS11 was 420k to 370k years ago. However Vostok goes back much further, and shows no methane pulse during MIS11 that exceeded present day concentrations. http://www.giss.nasa.gov/research/features/200409_methane/core1.gif idunno, That may be a factor. But the relic permafrost is very deep.
Toggle Commented Mar 27, 2014 on PIOMAS March 2014 at Arctic Sea Ice
The IceBridge data portal is here: http://nsidc.org/icebridge/portal/ Large text files containing ice and snow thickness (and other data), with time date, and latitude/longitude of each sample are available here: http://nsidc.org/data/idcsi2
Toggle Commented Mar 26, 2014 on Mission possible at Arctic Sea Ice
Jai, Steve, I did point out the major difference between orbital forcing and AGW forcing in my reply above - orbital (precessional) implies reduced winter insolation that counters the summer increase in insolation. Keeping the subject to the ESS, I don't disagree that we are about to invoke massive emissions of carbon from land permafrost, but due to thermal interia considerations land warming will proceed faster than sea floor. The arctic ocean forms a cap of insulating ice during the winter, and growth is all the more vigorous the colder the overlying atmosphere is. So sea temperatures are kept relatively high during the winter, and by no means is all heat gain from increased melt and insolation in summer lost. Integrate this process for thousands of years (Melles et al MIS11 superinterglacial was about 20k years long) and I still maintain that whatever inundated permafrost in the ESS that had been substantially below freezing prior to inundation would have ample time to get to zero degrees C. Having in at least one instance 20,000 years to do so. As this warming occurs the methane stability zone between geothermal heat below, and warming from above would progressively reduce. Yet in all this time there was not a methane blow out, with catastrophic GW and a run away into a hypthermal state. Once again, I am not saying there will not be massive emissions from the ESS, I am saying I am very sceptical of claims of imminent catatrophic release causing massive (further) GW this century. I agree with Archer that it will be a chronic process, large emissions keeping raditive forcing up for centuries, possibly millenia. As I see it the real problem begins as continental shelves around the world start to release their methane stocks. That is highly improbable this century, and as it happens what will be seen is a gradual increase in atmospheric CH4. Within that gradual climb will be pulses as 'pockmarks' are formed by localised destabilisation and eruptions of methane. It is verging on the inherently improbable that simultaneous destabilisation globally would happen within a century. During the End Permian it took something of the order of 10,000 years.
Toggle Commented Mar 26, 2014 on PIOMAS March 2014 at Arctic Sea Ice
Jai, You said: "...we know that this was driven by summer insolation and not by greenhouse gasses so the winter temperatures were much cooler than today." I don't think this is necessarily the case. Most of the current Arctic Amplification is due to sea ice loss. Rather than refer to the Screen 2010 paper on this subject I'll refer to Serreze et al 2009, "The emergence of surface-based Arctic amplification". The authors find: "To summarize: 1) Starting in the late 1990s and relative to the 1979–2007 time period, Arctic Ocean SAT anomalies in the NCEP reanalysis turned positive in autumn and have subsequently grown; 2) Consistent with an anomalous surface heating source, development of the autumn warming pattern aligns with the observed reduction in September sea ice extent, and temperature anomalies strengthen from the lower troposphere to the surface; 3) Recent autumn warming is stronger in the Arctic than in lower latitudes; 4) Recent low level warming over the Arctic Ocean is less pronounced in winter when most open water areas have refrozen; 5) There is no enhanced surface warming in summer; 6) Conclusions 1–5 hold for both the NCEP and JRA-25 reanalyses, the major difference being that temperature anomalies in JRA-25 are somewhat smaller." It is reasonable to expect that for the Holocene climatic optimum and Holsteinian and Eemian that the same process was at work. It is very fundamental - open water during the summer stores an immmense amount of solar heat which is then vented to the atmosphere over autumn as the ice forms, and the resultant thinner ice also vents heat to the atmosphere over winter (NCEP/NCAR shows low level warming over the ice in recent winters). This is the cause of the marjority of warming. However at mid latitiudes winter insolation would probably have been reduced due to the precessional cycle driving the summer increase in insolation. So there may have been less warm influx from mid latitudes. Siberia may have been colder in winter than in recent years. As I discussed in this blog post: http://dosbat.blogspot.co.uk/2012/12/lake-elgygytgyn-and-arctic-warming.html We seem to be about at the lower limit of the Holocene Climatic Optimimum temperatures (about 1 to 2 degC warmer than 'at present' - the difficulty is when do Melles et al refer to as present, 1951 to 1980 or preindustrial?). However they also find Arctic super-interglacials which were 4 to 5 degC warmer than 'at present' - temperatures are for July. My point is that those temperatures were applied for centuries (possibly a millenia or two) and there was no methane blow out. DCS, You're striding so far ahead it's hard for me to keep up! I'll re-read what you say later in the week when I'm a bit fresher in mind.
Toggle Commented Mar 25, 2014 on PIOMAS March 2014 at Arctic Sea Ice
Jai, I'm very sceptical of the claims made in Shakhova's EGU presentation that: "...we consider release of up to 50 Gt of predicted amount of hydrate storage as highly possible for abrupt release at any time. That may cause ~12-times increase of modern atmospheric methane burden with consequent catastrophic greenhouse warming." My reasons boil down to: I am not convinced that the reasoning that leads to the 50Gt is sound. Pockmarks caused by eruptions indicate sporadic largescale releases, but not as big as 50Gt. The pockmarks are limited in extent - suggesting the process does not continue across a given region. Similarly with slides of sediment. There were no large methane emissions during periods such as the holocene climatic optimum, or during the Eemian or Holsteinian warm periods (when the Greenland was substantially reduced). For what it's worth I agree with David Archer that methane emissions from the continental shelves are likely to be chronic, not catastrophic.
Toggle Commented Mar 24, 2014 on PIOMAS March 2014 at Arctic Sea Ice
Fufuf, All good points, but search for "BSRN station on Greenland" on this page and you'll see a link to a page with incoming and reflected sunlight at Greenland summit graphed. The difference between them (absorbed) is very small, but multiplied over the whole of Greenland the clear skies of the GBI do cause a substantial amount of sunlight to be absorbed, resulting in large changes in run off. Hansen has been concerned (rightly) that as the climate around Greenland warms the risk of rain (not snow) could cause a massive increase in run off. watch for that when the Arctic transitions to seasonally sea ice free. watch for increases in melt on the northern flank as well! I do agree that the WAIS and Greenland combined could well cause more then 2m of SLR in the rest of the century. My disagreement is with those claiming just Greenland could cause that.
Toggle Commented Mar 23, 2014 on PIOMAS March 2014 at Arctic Sea Ice
That's the problem of posting when tired, thanks Al.
Toggle Commented Mar 22, 2014 on PIOMAS March 2014 at Arctic Sea Ice
Jai, I chose a 2000m column and -30degC due to the plot from GRIP shown in the paper (Dorthe Dahl Jensen) Al Rodger linked to. "I believe that a 3 meter rise by 2100 is an optimistic scenario due to non-linear responses to non-linear warming events." As for shelf collapse in the WAIS, I've not read enough to engage in a constructive discussion. But I've not read any scientists saying as much, so at present I am highly sceptical. Al Rodgers, Surface area of the earth, 510,072,000km^2, or ~5.1X10^14 sqr metres. (1000 X 1000 metres in a km^2) 1W/m^2 = 1 joule/sec over any square metre, in a century that's: 60 X 60 X 365 X 100 = 1.31X10^8 seconds or 1.31X10^8 joules (a Watt is 1J/sec) per sqr meter for a century. Multiplying those joules by the surface area of the earth gets me: 6.681X10^22 or 67ZJ. That's much bigger than your figure. But Greenland is only 0.4% of the earth's surface. Antarctica is only 2.7%, being in the Southern Ocean, whose thermal mass reduces southern hemisphere warming (along with other oceans) the sensible warming, hence heat fluxes won't be so large. In the NH you have Arctic amplification, I think that's a factor of between two and three, call it three. But even multiplying 0.4% by 3 (1.2%) is still a very long way off 20% of the total energy imbalance. Steve, But the main land ice sheets didn't have the geographical constraints of Greenland. That is why Pfeffer et al concentrated on the 'gates' in the mountains, with Greenland being a bowl (depressed by the weight of ice) surrounded by containing higher ground, their Map 1. Pfeffer et al found Greenland's contibution to SLR could be 0.8 to 2.0m by 2100, with the higher end only being feasible if outlet glacier flow was set to the highest conceivable levels. I feel I should point out that in 'In Defence of Milankovitch' Roe finds that the rate of change of ice sheet extent during the glacials/interglacials varied in lockstep with insolation. Although that doesn't tell us anything about rates this century.
Toggle Commented Mar 21, 2014 on PIOMAS March 2014 at Arctic Sea Ice
Rick, I knew I'd read of a BSRN station on Greenland. There's a graph on this page: http://www.polartrec.com/expeditions/solar-radiation-on-the-greenland-icesheet-2011/journals/2011-06-05 Search for the string - Graph of Incoming and Shortwave Reflected Radiation at Summit Station, Greenland . Due to the ice being white the absorbed solar radiation is actually far less than 250W/m^2.
Toggle Commented Mar 21, 2014 on PIOMAS March 2014 at Arctic Sea Ice