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Pete Williamson
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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 6 days ago 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
Blaine sorry for the delay but I tried a bit of scientist bothering and emailed PolarPortal about the apparent discrepancy between the GRACE data and reported mass balance. Here is their reply, it seems like the GRACE data for the 2013 summer is unavailable (they just infilled the grapg for that period) "Your question is really good, and the answer is actually quite simple: The GRACE mission is already way past the originally intended duration, but the satellites are still flying. But systems do fall out once in a while and, as an example, the 2013 summer data are unavailable due to power system problems. The 2013 summer data are thus missing from the Polar Portal GRACE figure. The linear interpolation across the summer negative peak suggests an extremely low (even no) loss summer and therefore is very misleading. We will work on a different way of representing this."
Toggle Commented Jun 10, 2014 on Greenland 2013 in review at Arctic Sea Ice
Blaine I'm surprised to hear God isn't involved in the calculation ;) I hope you'll bare with me a little longer because I'm trying to get my head around all the different 'data' source. GRACE - this is gravity measurements from satellites and gives the overall change is mass. This requires a model to convert the raw satellite data into changes in mass? We (I mean you) are happy with this data? SMB - This is model output of snow accumulation, evaporation, melting sublimation(?) at the surface? Based on weather inputs to a model(temp, wind, snowfall etc). You are saying you think this may have gone a bit wonky for the 2013 season? Discharge/carving/melt at glacier front. - Annual estimates are based on ....what method? Or this just derived from the difference between GRACE and SMB? Or calculated independently for each season? There seems to be a mismatch. I'm not seeing how that is arising. Or are you saying it's not clear which bit is off? thanks
Toggle Commented May 30, 2014 on Greenland 2013 in review at Arctic Sea Ice
Thanks for the explanation. So if I understand you could describe the 2013 season as relatively quiet season for Greenland. A typical (recent) year is that there is there is normally a rather large nett accumulation of mass at the surface. This is offset by an even larger mass carving and melting in the ocean terminating glaciers. The 2012-2013 season there was a smaller net accumulation at the surface (but still positive). The winter looked normal but summer showed a greater nett loss than normal. But there was very little iceberg carving that year so overall the total mass of Greenland changed very little. Although surface mass balance is obviously a big factor it looks like variability in carving events can really swing things one way or another when it comes to overall mass change of Greenland ice.
Toggle Commented May 29, 2014 on Greenland 2013 in review at Arctic Sea Ice
Thanks for the link, lots of pretty images. I'm confused though. The website has this mass balance graph on it I always assumed this was the total mass change of the icecap, that is how this GRACE data has been presented. It shows little mass change over the full melt/accumulation cycle for 2013. This is in contrast to the previous large 2012 season. Yet the report says there has been a lerge mass loss (equal to 1.2mm) So what am I not understanding?
Toggle Commented May 27, 2014 on Greenland 2013 in review at Arctic Sea Ice
Magma says "This is starting to look like yet another example of bistable behavior with tipping points" The curious thing is why with all these tipping points it seems the earth was perched on the edge waiting for humanity to push it over. Why shouldn't the tipping point be now or in 20oC time?
Toggle Commented Mar 21, 2014 on PIOMAS March 2014 at Arctic Sea Ice
Interesting the discussion drifted to PIOMASS. If ice bridges can be characterized as dynamical processes, with no clear relation to thermodynamics. And if they contribute to overall ice volume by regulating ice loss through the Nares strait, I think I've read maybe 10% of the exported ice leaves via Nares. And if there formation can be quite variable, I've read the date of their formation and collapse can vary. Then I'm wondering if anybody knows if PIOMAS can take account of these types of dynamical changes in calculating ice volume. Maybe the final impact is quite small and these sorts of variations are contained in the error bars?
Toggle Commented Feb 2, 2014 on 2014 Nares Strait ice bridges at Arctic Sea Ice
Wili said "So should we be using these CryoSat numbers or the lower PIOMAS numbers ........ (Of course, both show dramatic ice loss over the decades.)" Sorry the pedant in me couldn't let this slide by. It's not possible for a satellite that's been generating data for 4 years to tell us anything over the decades. Just 4 years! My wider point can be summed up by something a lecturer at university once said, from a google search it appears to originate from the geneticist William Bateson. Bateson's advice was to "treasure your exceptions". My understanding of that is to take note of observations that confound your expectations, it's data like this that has the potential to give greater insight into what is occurring more generally in the arctic. Yet most commentary seems to want to do little more than label this data point as weather and then move on. Also I see ESA's point that the MYI has undergone a recovery but their data suggests to me that the 'recovery' is much more extensive than that (Barentz being the exception). The map for 2013 shows cyan/green extending much further into the Arctic than previous years and for that phenomenon to be homogenous over all the regions were ice is present. Shorthand, the ice is thicker everywhere (almost)! And finally a question. Why do we have to call this weather? The great clearout of MYI in 2007 was weather. Why can't we say all the post-2007 data is weather given the large impact that year and subsequent storms etc have had. It seems rather one sided to invoke weather for the years when ice loss is less.
Good to have US data back. Sans Barentz, it looks like the European side of the Arctic is going through something of a recovery. It'll be interesting to see if it can spread into Barentz Sea as well
AFU I don't see why on this issue you should think that JC is at odds with your thinking. The mainstream seems to, at least in part, invoke 'internal variability' to explain the pause, all the Wyatt paper seems to be doing is trying to put flesh on the bones of that idea. The stadium wave may not turn out to be the explanation but something has to. The present situation where variability is seen as little more than the residual in an analysis has to be put behind us. The pause is going to be the impetous for others to get involved ( actual others are already there)
Except that it does appear as though the Atlantic waters moving north to the Arctic peaked in temperature around 2007. A "recovery' in the ice extent in the Barentz/Kara would make sense, everything else being equal.
So the possibility of another crystal-ball gazing game in the arctic. This graph shows that the winter maximum of the CT ice area hasn't broken 14 million for 10 seasons Given the spooky melt season this year what are the chances that that particular upper limit might be breached.
Toggle Commented Sep 21, 2013 on Pinpointing the minimum at Arctic Sea Ice
Beaufort Sea continues to look interesting. Just from eyeballing the CT area chart it looks like this year wouldn't be out of place in the late-1980's and late-1990s. It looks like for each year since 2007 the Beaufort Sea has been in negative anomaly territory for more than half the year. This year it's looking like it's going to be negative for little more than 2 months. Given the endless observations of cracked and rotten ice in the region it seems rather remarkable.
Toggle Commented Sep 19, 2013 on Pinpointing the minimum at Arctic Sea Ice
Just meant to add the survival of alot of the Beaufort Sea ice make contribute to that. Cheers
Neven, I think at some point you're going to have to stop being surprised at the lack of melt (or the persistence of extent) this year :P It looks like this might be a 'new high' post the 2007 MYI clear out. It may be better understood as part of the natural variability and if we want to understand what's going on then we should be looking at the average extent since 2007 rather than expecting records to be broken. There is probably too much focus on record-breaking in the arctic. Given that ice can persist (or fail to persist) for 5 years or more suggests we should be trying to understand processes on that timescale as well. Not only has a lot of FYI survived but so has much of the SYI (2nd) which is going to start showing up in the MYI category next year. It possible that at least a bit of a 'recovery' in the MYI is on the cards.
alert wili knows about the 'experiment'. Initiate alpha one zero! Now, do it now!
Toggle Commented Aug 19, 2013 on ASI 2013 update 7: cold and cloudy at Arctic Sea Ice
Blaine the papers hint at were Serreze is coming from. "The most obvious feature is strong variability." "Arctic cyclone activity displays significant low-frequency variability" If you understand what those sentences mean and then try to put the past two summer season into that context then you can see why it might be easy to be misled over the direction of the trend. It seems like a lot of climate science is like this, crudely put we need lots of data in order to pull any signal from the noise. Just from the papers you link to it would seem safest to say there is no clear trend. We would have to see the detail behind his claim of a drop in cyclone activity to judge it in the context of others work. All that said I would love to see an arctic cyclone activity data set that continued through to present day, the recent years of low ice extent would give more insight. I actually emailed John Walsh (bad me for scientist bothering) to see if he had extend his CAI beyond the 2002 year in the publication, unfortunately not! I really don't get why people are reacting so badly to what Serreze has said here.
A strange day today On the ASIB there seems to be something of a celebration because the public believe arctic climate change affects their weather when the scientists are clearly still debating this, and when L Hamilton says that belief is in part shaped by what the weather was like when they were interviewed. A (lack of) logic that would normally have consensus-believers frothing. And over at WUWT they are celebrating the outputs from climate models, because they show something other than CO2 might be causing the changes in the arctic. Where is the consistency?
Toggle Commented Aug 14, 2013 on Perception of the Arctic 2 at Arctic Sea Ice