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Pete Williamson
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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
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.