This is Pete Williamson's Typepad Profile.
Join Typepad and start following Pete Williamson's activity
Join Now!
Already a member? Sign In
Pete Williamson
Recent Activity
Chris, a couple of points. You say "That this also plays a role in the 1930s/40s ice loss event (Belleflamme) is interesting as although not shown in the literature, I continue to suspect strongly that the AD is a pattern emerging in response to ice loss." It appears you are saying AD caused the ice loss and ice loss caused the AD. I guess you can have it both ways but it still looks less than an ideal explanation. I think you also need to look a little more carefully at the Belleflamme graphs. The other time when the AD is dominant is the 1950s-1960s not 1930s-1940s as you say. This is not a period when ice losses were so great. In fact, from memory, any attempts to reconstruct ice extents in the 20th century have tended to suggest ice has been relatively stable. Past arguments have been that the 1930s-1940s warming of the NH was too short to have much impact on ice. But I think the Belleflamme adds something to that story. 1940s the NH was warming but atmospheric circulation didnt favour ice loss, outcome stable ice conditions. 1950-1960s Atmospheric circulation favours ice loss but NH temps are cooling, outcome stable ice conditions. Present conditions atmosperics and NH temps favour loss and we see significant loss. At no point do I rule out AGW but I also dont think the data supports the idea that other factors are ruled out, in fact NH warming appears necessary. The model comparisons dont show what impact the dynamical processes have had on the ice because the models cant reproduce the specifc conditions that have occured in the real world. I think this is generally expressed that natural processes are an initial condition problem so remain untested. For example no CO2 runs that are 'forced' with Belleflamme's atmospheric circulation would be a better test. Put another way the natural runs work as a negative control for the anthro runs but they dont themselves work as good simulation of the actual natural conditions that we experienced so they dont really work as a test for natural impacts.
Toggle Commented Oct 24, 2015 on PIOMAS October 2015 at Arctic Sea Ice
Thanks Chris it makes a lot of sense now. But I'm going have to disagree with you on the final sentiments. There seem like plenty of reasons to think a variety of potentially natural processes that have contributed to ice loss along side AGW. Fram Strait export appears to have a positive trend over the past couple of decades. h Atlantic water pulses of warm water seem yet to be attributed and look unconvincing as arising from AGW And atmospheric circulation changes since ~2000 have also favoured ice loss. I understand these processes have themselves been linked with AGW but that too seems yet to be confirmed. Just to be clear I dont discount AGW just see it as part of a complex mix of natural and anthro that have contributed to ice decline. Honestly it surprises me that you have confidence in attributing all this ultimately to AGW.
Toggle Commented Oct 21, 2015 on PIOMAS October 2015 at Arctic Sea Ice
"been pretty amazing, if you are following the IJIS numbers. You can say that again. 1 million km2 in just 6 days! That's pretty impressive. While it is impressive it's not that unusual in October" DavidR, Neven, Just to continue the twaddle about how unusual (or not) the 2015 refreeze has been so far. I took the past 30days from this data set Highest increase in this period is 2008 with 3.13million km sqd. Second is 2015 with 2.73, 2012 3rd with 2.70. The full list looks like this 2008 3.13m km sq'd 2015 2.73 2012 2.70 2013 2.69 2010 2.60 2014 2.45 2002 2.43 2004 2.27 2005 2.20 2003 2.11 2006 2.06 2007 1.88 2009 1.81 2011 1.71 post-2007 mean 2.41 2000's mean 2.30 1990's mean 2.15 1980's mean 1.70 So yeah impressive refreeze so far.
Toggle Commented Oct 20, 2015 on PIOMAS October 2015 at Arctic Sea Ice
Chris, thanks for trying to explain it further but I'm too stupid to understand what you are saying. I tried the Armour paper but that too was beyond me. It did strike me though that a large part of MYI loss in recent years has been to do with ice drift and export as much as to do with warming. IDK if Armour is unpicking the different factors, whether "forcing" in the paper is meant to cover all factors that lead to loss of MYI although it does look like the papers focus is on melting. As I said I dont really understand the paper so these comments are really questions rather than facts.
Toggle Commented Oct 20, 2015 on PIOMAS October 2015 at Arctic Sea Ice I dont know if the image is going to work but I thought it might be interesting to show the relationship between Sept ice area and ice gain during the following refreeze season. The image above shows the NSIDC Sept ice area vs piomas ice volume gain during the following refreeze season (apr vol - previous sept vol). What it shows is that if a winter starts off with a relatively low ice area then more ice tends to form over the refreeze period. The simple physical explanation is that open water is the birth place of new ice and so more open water=more ice formation. In a sense this is acting as a negative feedback on ice loss. The Sept ice area from the data set I'm using is 3.31km sq'd. If this year follows a similar pattern then we might expect that 17.7-18.7 km cubed of ice might form over the coming season and next years max be around 23.5-24.5 km cubed. So above the 2011-2014 lows and within the range of the other post-2007 years. Of course there is a lot of weather to happen between now and then but I thought the relation shown in the graph was interesting.
Toggle Commented Oct 16, 2015 on PIOMAS October 2015 at Arctic Sea Ice
Lawerence, I think your rushing to dismiss BDS's question about Antarctic ice question as a "gotcha" question. There's one thing to ask a question and analyse the data and then there is a separate question to come to a conclusion that the answer comes from ignorance/dis-information/political bias. You should be really happy to test that conclusion. BDS's question has the potential to do that. For example Clinton supporters answers might just be matching reality because their political belief is humanity is screwing up the planet and the arctic data seems to confirm that. The Antarctic question would test whether they really do have knowledge of the climate rather than then knee-jerking about human impact on the environment. It's not that I particularly think Clinton's supporters are an more or less irrational than GOPers (although Tim makes an intersesting points with respect GMOs) but researchers should always be prepared to test their conclusions/assumptions.
Vaughn, I dont doubt the plausibility of the ideas you've laid out but the question is really how much they dominate. I like this paper which seems to try to put the recent circulation changes into a 100+ year perspective. I think its important because although others have done a similar analysis for the recent period(with similar results), this seems to be the first work to give the longer time frame. Most of their attribution discussion focuses around the recent period but I think there are interesting insights from earlier times. Their fig2 is the main finding and circulation patterns 2 and 4 are the interesting "ice melting" patterns. In the 1930s/40s there was some warming of the NH with an arctic amplification pattern but their results suggest the "ice melting patterns" were less frequent. In the 1950s/60s the frequency of "ice melting patterns increased in a similar way to the present but the temp records suggest temperature in the NH cooled somewhat and the arctic amplification pattern disappeared. Essentially these two earlier periods appear to be behaving in the opposite way to how you outline warming may have been working in recent years. This is the type of work that makes me wonder a) The extent to which the warming pattern is influencing the circulation changes b) The extent to which the warming is attributed to forcing and dynamical circulation changes. Clearly as you suggest the two processes are likely to influence each other but it also seems plausible that circulation changes have 'natural' origins. And clearly a warming world can influence ice loss more directly and thru other feedbacks. I struggle to know just which processes are dominant.
Toggle Commented Oct 4, 2015 on 2015 minimum overview, part 2 at Arctic Sea Ice
From the conclusion "..... a more or less average 2015 melting season ....." The real issue for me is trying to put that particular comment into a long term context. From the (small amount of) science done in this area the tendency seems to be that the circulation patterns in the recent past ( say ~ post 2000) have tended to be at an extreme, showing patterns that favour ice loss. What represents " more or less average" in recet times does not necessarily mean the same thing when compared with longer term reconstructions(?). At the same time there seems to be competing evidence about whether these changes in circulation patterns are natural or CO2 forced or a bit of both.
Toggle Commented Oct 3, 2015 on 2015 minimum overview, part 2 at Arctic Sea Ice
Did you notice PIomas posted a note on their website on the 2015 ice volume minimum. "The sea ice extent minimum for 2015 was likely reached on Sept 11. Sea ice volume minimum was reached a day later with a total volume of 5670 km3 . This value is about 1200 km3 below the volume minimum of the 2014 which showed a subtantial rebound in ice volume. The value for 2015 is 300 km3 above the value for 2013 and constitutes a continuation of the long-term declining trend (see fig 1) with shorter term variability in both directions (e.g. 2012 and 2014)."
Toggle Commented Sep 26, 2015 on 2015 minimum overview, part 1 at Arctic Sea Ice
"where the flash melting during the past 2 days on the Pacific side of the Arctic is apparent" Your animation seems to show compaction of the ice as the concentration seems to go up. Labelling it as only melting seems a bit off.
Toggle Commented Aug 28, 2015 on Arm's race (and a storm) at Arctic Sea Ice
Neven if what you say is true and in general continues thru the melt season it might make for an interesting test year. I've wondered to what extent dynamical and thermodynamical processes have contributed to ice loss post-2007 (maybe even post-2000). Can heat minus export produce the extreme lows? Is lack of export alone enough to allow for another 'recovery' year? Its not that I dont think a warmer world melts Arctic ice, just that the heat in conjunction with 15years of weather patterns have given us a (substantial?) overshoot on ice loss that warming alone would have done. There was some recent research that suggested that weather patterns in the Arctic had been unusual since around 2000 (I think compared with 100+ years previous) and that 2013 (and 2014?) represented a reversal of that persistent pattern. And also that those weather patterns (teleconnections?) have had a sizable impact on ice loss.
Toggle Commented Jul 8, 2015 on ASI 2015 update 4: massive heat at Arctic Sea Ice
thanks Neven, I guess what I was saying ( badly) is that its actually unsurprising that the SST should be so high given that the Bering Sea had low ice cover and the strait has been ice free for long now than in recent years. I guess my point is there are other regions that maybe compensate for that region this year, such as the Siberian coast but that doesnt show up on this sort of chart because ice covered areas are masked out. I guess, for me, this sort of chart can be visually deceptive. Clearly what you say is right, although when I look at the 2012 chart you link to it looks ablaze everywhere except Bering and in that sense overall 2015 looks more like the rebound years ( ie regionally mixed) rather than the more consistent warm low year of 2012.
The issue I have is that roughly we at are at the stage where many of the ice metrics suggest the ice could quite easily follow a path to a low final ice extent or one similar to the recent rebound years. Also generally many of the 'weather' metrics seem to be relatively benign. I'm not seeing any reason to get over-excited by a large melt this year. BTW I have a question about the 'HUGE' SST. With ice extents clearly low in recent years, compared to the 1980s and 1990s isnt it always going to be the case that the SST in area with open water is going to be higher than when its covered by ice, anywhere where there is anomalously low ice (such as Bering strait this year) is going to show as large SST anomalies. The phase change between ice covered and open water seems to make interpretation of those dark, pinkish reds problematic. For example the siberian coast this year would likely show as much colder SST because there is more ice there this year than compared to recent years except that it doesnt show because the ice covered area is screened out. This type of chart seems to accentuate the hot.
Sorry OT Have people had a chance to read the full paper above. They are reporting that post-1979 ice decline has avery large internal variability component. Bottom line is 49% from Combo f Atlantic waters and arctic dipole (1979-present). And 44% from pacific waters 2001-present. I dont know how this is summed to give a total attribution to dynamical changes, but it looks very large.
Toggle Commented Apr 2, 2015 on The Ns are calling the maximum at Arctic Sea Ice
"The big question now, of course, is whether the thinning will continue at this rate or slow down. Hopefully this will become clear in years to come." Yep. For example the paper is about thinning ice doesn't say whether its melting or floating away. There is also no timeline so while we have the average rate of change there is no sense of variability over time. I'm doing something I generally really hate, which is to criticize a piece of science for what it doesnt contain rather than look at what it does. I guess Im greedy for the bigger picture answers.
Toggle Commented Mar 6, 2015 on Thinner and thinner at Arctic Sea Ice
I remembered a paper published a while back that gave some insights into variability in ice arch formation in the Nares Strait. Even in the short length of years covered by this paper you can see in table 1 that arch formation can be very variable from as early as early December thru to April. Given that conditions can be such that arches fail to form thru most of the winter it doesn't seem that much of a stretch to think arches could form and break up within the winter season. Actually reading more carefully in section 4 they talk about the formation of short lived arches in unusual parts of strait. Still this years observation is interesting.
Toggle Commented Feb 16, 2015 on Erase and rewind at Arctic Sea Ice
Neven to stretch your basketball analogy a bit further, any team that ignores rebounds is going to lose the game! ( caveat I know as little about basketball as I do about climate science) I would have thought the past two years would have taught us a little more about the role of internal variability/dynamics on arctic ice.It seems particularly interesting because its moving in the opposite direction to the way we might expect radiative forcing to affect the ice.
Toggle Commented Nov 16, 2014 on PIOMAS November 2014 at Arctic Sea Ice
Given that some of the discussion here is about atmospheric circulation/dynamics I thought I'd draw peoples attention to this new paper in discussion Recent summer Arctic atmospheric circulation anomalies in a historical perspective A. Belleflamme, X. Fettweis, and M. Erpicum The Cryosphere Discuss., 8, 4823-4847, 2014 it looks at recent changes in circulation over the arctic, how it may affect ice melt and compares it to the past >100years. heres my summary of it, people can disagree with what I've highlighted as important. The paper is looking at the frequency of daily high pressures over different parts of the arctic. It identifies two patterns (type2 and type4) that it shows have doubled in the 2007-2012 period compared to the long term average. these type are highs over Beaufort and highs over Greenland, these are both good for increases in melting sea ice and GIC. They construct an historical record of these circulation patterns and compare this recent event to past events. They find similar departures for these two patterns in the past although given we are still going through the present anomaly its not possible to say whether the present is outside 'natural variability'. They do mention though that these departures are seen ~100 years ago when presumably both the global and arctic temperatures were cooler. What does this study prove? I like to think whats plausible as there seems to be enough uncertainty and insufficient data to make firm conclusions (as is often the way). It seems plausible (maybe even likely) that multi-annual to decade changes in atmospheric circulation have contributed to the post-2007 melt. I think if you look at their graphs you could say that the type2 circulation has been high since 1980s with the present departure coming on the back of that and the type4 has been increasing since the late 1990's Attribution of what cause these changes (crudely is it natural or anthro or a bit of both) is impossible from this paper but to me it seems evidence points to it (at least) in part being natural. For example similar events occurred at the end of the 19th century when presumably global and arctic temps were lower and sea ice was higher. How the future develops might help to understand this. they note just what a huge reversal 2013 was. The daily occurance of these two circulation patterns went from way above the historical average to way below. I;m guessing 2014 is similar. presumably if this continues forward in the future then we may get a better idea how the present circulation anomalies compare to historical events and also to what extent its natural and to what extent its had an impact on declining ice.
Toggle Commented Sep 11, 2014 on PIOMAS September 2014 at Arctic Sea Ice
Correction: the metric i looked at in the past was ice gain ( increase from minimum to maximum). I don't know what the seasonal losses look like for each year making me even more curious to see how this year stacks up
Toggle Commented Aug 19, 2014 on PIOMAS August 2014 at Arctic Sea Ice
One interesting metric might be the total volume of ice to melt ( or be exported) this season compared with previous years. With the maximum volume in March being one of the lowest and the minimum volume (september) looking like it will be at the higher end of the post-2007 years then it could be that volume loss might be at the lower end of the whole. I looked at this number in the past and found that the pre-2007 years all generally had quite similar seasonal volume losses while post-2007 the numbers became more variable. It would be interesting to see whether this year has returned to the pre2007 volume losses or possibly is even lower. Somebody who has the piomas data could do this calculation upto the present date or maybe its one to save foor the end of the season
Toggle Commented Aug 19, 2014 on PIOMAS August 2014 at Arctic Sea Ice
I thought my original position was consistent with AGW theory. without extra heat in an accessible place in the NH then there is no reason for the Arctic to keep warming. Of course internal feedbacks may still be in play but at some point a new equilibrium is going to be reached until warming recommences.I dont have any firm idea how long (or how much) feedbacks continue to amplify warming beyond the initial external forcing but I do think nobody is suggesting its a runaway process.
Toggle Commented Aug 5, 2014 on ASI 2014 update 6: slow times at Arctic Sea Ice
Pre-anthro-forcing did ice melt differently?
Toggle Commented Aug 5, 2014 on Poof, it's gone at Arctic Sea Ice
jdallen_wa I have to be brief and write in note form i dont have citations was using KNMI climate explorer to look at data sets e.g. For the NH midlatitudes I took Hadcrut4 (20N to 60N) and get this OHC for the Atlantic is NODC I get this For AMOC, yep I like the Elliott line work, I think there is more insight to be gained from it than just the quote you highlight. But as well as that work there is also a study called US AMOC/UK RAPID which is shorter but shows a similar situation. You need to hunt for poster and publications based on that study (Id give you a fuller answer if I was on a more user friendly device sorry)
Toggle Commented Aug 1, 2014 on ASI 2014 update 6: slow times at Arctic Sea Ice
It doesn't seem too implausible to think come mid-Sept that we might be in pre-2007 territory WRT CT area although lower does seem more likely. General conditions in the NH midlatitudes more resemble the early 2000's than post-2007 conditions. Tropospheric temps are unchanged for ~15 years. Atlantic Ocean surface temperature, heat content and the heat being transported by the AMOC north all seemed to show peaks in the mid to late 2000's with present conditions a little cooler. Given these are the sources of heat for the Arctic it seems about right that arctic ice should start to return to pre-2007 condition unless things at mid-latitude change. Of course there are internal feedbacks, these may or may not have worked their way through the system for the earlier warmer period, so there may be more melting from that. All things being equal though it seems a small increase in ice, say back to 2003-2006 conditions wouldn't be outside expectations.
Toggle Commented Jul 30, 2014 on ASI 2014 update 6: slow times at Arctic Sea Ice
Neven you made a passing nod but I think it's worth highlighting. The Barentz Sea has been ice-free for much of this season and had one of the lowest maximum extents. Yet as you're SST graphs show the ocean surface temps are far, far lower this year than in recent years. Given that in the past an explanation for the hot temperatures was sun beating down on ice free ocean then what would be an explanation for these lower temperatures?
Toggle Commented Jul 15, 2014 on ASI 2014 update 5: low times at Arctic Sea Ice