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Rob Dekker
California
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Wayne said Despite winds not conducive to compaction, the Beaufort Gyre turned clockwise throughout June, this is an amazing feature making some meteorologist scratch their heads. I'm not a meteorologist, but it made me scratch my head. Especially with the lows over the Arctic we have seen all through June. The only explanation I can give is that if you plot the surface air pressure over many months (specifically Feb through May) on NCEP/NCAR, http://www.esrl.noaa.gov/psd/data/composites/day/ then you will find that there was a sustained high positioned over the Beaufort Gyre, and a low over Alaska, that would have set the Gyre current in motion (and opened up the Beaufort early this year). So it seems that the Beaufort Gyre current has a longer "memory" than most think...
Toggle Commented 2 days ago on 2016 melting momentum, part 2 at Arctic Sea Ice
Guys, the "ice concentration" metric (or more accurately "extent minus area") is only ONE variable that sets the trend for ice loss, or melting momentum. Just plain "ice area" is another one : regression analysis shows clearly that in June, if the Arctic has low "area", that this amplifies melt down to September. Which makes sense : if there is less ice in June, there is more open (dark) ocean, which amplifies albedo feedback. And the third main variable is "land snow cover". This one (especially in June) correlates strongly with the amount of ice that will melt out until September. Which make physical sense again, since snow-free lands absorb a lot of heat, which warms the winds over the land and thus warms the winds that will blow over the ice. All three variables are currently close to 'record' level, which suggests that 2016 will be going low. But it may require a early August GAC to break the record, as happened in 2012.
Toggle Commented 4 days ago on 2016 melting momentum, part 2 at Arctic Sea Ice
OK John, yes, if that is true, it would only add to the 2016 advantage. But I gotta tell you that I've not seen any scientific paper that links the AO to Arctic sea ice decline.
Toggle Commented 5 days ago on 2016 melting momentum, part 2 at Arctic Sea Ice
I probably should have worded that better, but the point is that the expression "extent minus area" is a very good indicator of the amount of melting ponds and lead and open water right next to the ice. That is a very good indicator of short term melting potential. And since "extent minus area" is right now at par or even larger than 2012, everything else considered equal, 2016 will follow the 2012 melting curve, if not outperform it.
Toggle Commented 5 days ago on 2016 melting momentum, part 2 at Arctic Sea Ice
Wipneus at the forum just posted the latest AMSR area and extent numbers : Extent: -88.2 (-582k vs 2015, -430k vs 2014, -1012k vs 2013, -172k vs 2012) Area: -64.6 (-503k vs 2015, -315k vs 2014, -869k vs 2013, -320k vs 2012) This shows that 2016 is still firmly in the lead, both for "area" as well as "extent". It shows that the DIFFERENCE between extent and area (a good indicator of the amount of melting ponds and leads) is still larger now than in 2012. Which simply suggests that melting potential is larger now than in 2012, and 2016 will thus probably continue to drop faster than other years.
Toggle Commented 6 days ago on 2016 melting momentum, part 2 at Arctic Sea Ice
Also, there does not seem to be any physical reason why MASIE's "extent" would drop as a result of this storm. After all, a "low" over the Arctic typically would increase "extent" because of ice dispersion. This low was situated over the central CAB, too far away from the "extent" boundary, so "extent" should not be affected much. For example, Wipneus' "extent" drop was caused mostly by the Hudson and Baffin Bay. So it is likely that MASIE's 200+ extent drop has more to do with their subjective way of estimating ice in the Arctic than with the effect of this (mild) storm.
Toggle Commented 7 days ago on 2016 melting momentum, part 2 at Arctic Sea Ice
Interesting what the effect of this storm had been for the numbers : - MASIE "extent" dropped 270 k - Wipneus CT "area" dropped 143 k - Wipneus AMSR2 "extent" dropped 83 k - Wipneus AMSR2 "area" dropped 153 k So it may be that CAMAS increased, but Wipneus' concentration graph dropped.
Toggle Commented 7 days ago on 2016 melting momentum, part 2 at Arctic Sea Ice
That's right, John. At least " the magnitude of the CMIP5 multi-model mean trend in September Arctic sea ice extent over the satellite era is more consistent with, but still underestimates, the observed one (see also Massonnet et al., 2012; Stroeve et al., 2012; Wang and Overland, 2012; Overland and Wang, 2013)" I have previously suggested that the underestimate of the ice extent decline in GCMs is rooted in the underestimate of decline in land snow cover, which is underestimated by a factor of 2 or 3 in CMIP5 models (Brutel-Vuilmet et al 2013), thereby significantly underestimating albedo feedbacks during the melting season.
Toggle Commented Jun 22, 2016 on 2016 melting momentum, part 1 at Arctic Sea Ice
Let me add that I don't challenge Neven's statement that " it will take special weather conditions for it to break any records near the end of the melting season.". In fact, for SIPN/ARCUS I entered 3.8 M km^2 as the most likely September 2016 average extent. But I'd like to caution against being overly conservative. The state of the ice in 2016 is not good at all, and with albedo feedbacks, the Arctic is right now much more sensitive to weather than it has ever been, so if even an average summer gets us to 3.8, a bit of melt-inducing weather will easily get us much lower.
Toggle Commented Jun 22, 2016 on 2016 melting momentum, part 2 at Arctic Sea Ice
Thank you Neven, great post, but I'd like to add a few notes. When I look at the "regional graphs", I noticed that for the Central Arctic Basin (CAB) (the area where the September minimum will end up) that "extent" in 2016 is about the same as it was in 2012, but "area" in 2016 is lower than 2012. Which suggests that in the CAB the ice concentration at this time is LOWER than it was in 2012. That kind of makes sense, when you look at the fragmented mess of the CAB that has been feeding the mess in the Beaufort over the past month, and also the fragmented ice in the CAB that is still moving into the area North of Svalbard. So what caused the ice concentration to be higher now than it was in 2012 ? If you look at the regional graphs, only the Laptev appears as clearly having a higher area/extent ratio at this time. That's probably because this year the Laptev did not melt as quickly as in 2012. Other than the Laptev, 2016 is still ahead of next runner up 2012 for extent. And ice concentration in the CAB is still below 2012.
Toggle Commented Jun 22, 2016 on 2016 melting momentum, part 2 at Arctic Sea Ice
Oops. That would be chapter 12 : https://www.ipcc.ch/pdf/assessment-report/ar5/wg1/WG1AR5_Chapter12_FINAL.pdf
Toggle Commented Jun 22, 2016 on 2016 melting momentum, part 1 at Arctic Sea Ice
John, Yes. the sea ice projections (using CMIP5 models) are in AR5, WG1 report, chapter 12 "Long-term Climate Change: Projections, Commitments and Irreversibility". https://www.ipcc.ch/pdf/assessment-report/ar5/wg1/WG1AR5_Chapter11_FINAL.pdf Check figure 12.28b, in section 12.4.6.1, on page 1088. I know. It's almost as if they want to hide it. But it's there at least. And the 3.1 - 4.8 bet range in 2016 is still well below model projections (albeit a bit less below model projections from CMIP3 models compared to reality/observations.
Toggle Commented Jun 22, 2016 on 2016 melting momentum, part 1 at Arctic Sea Ice
And here is one that includes 2012 : http://neven1.typepad.com/.a/6a0133f03a1e37970b017744cf5360970d-pi
Toggle Commented Jun 21, 2016 on 2016 melting momentum, part 1 at Arctic Sea Ice
John, you are no "ignorant". Here is a graph of actual Arctic sea ice extent versus IPCC model projections : http://www.realclimate.org/images/seaice10.jpg
Toggle Commented Jun 21, 2016 on 2016 melting momentum, part 1 at Arctic Sea Ice
This is a little bit off-topic, but William Connelly has put up a post about the sea-ice bet on the 2016 September minimum I made with him 5 years ago : http://scienceblogs.com/stoat/2016/06/13/the-sea-ice-post/ Note that the bet's void range is 3.1 - 4.8, and considering that the September minimum will likely fall within that range, we likely both be wrong. But considering that this entire range is quite outside the IPCC projected range for 2016, the models still underestimate reality, which is a grave point of concern in my opinion.
Toggle Commented Jun 21, 2016 on 2016 melting momentum, part 1 at Arctic Sea Ice
Excellent overview, Neven, as always. I trust that in part 2 you will cover other variables that affect melting momentum as well. After all, the "melting ponds" in May, as Dr. Schoder's model uses, is not the whole story. For starters, there are not that many melting ponds in May, and while it is true that "melting ponds" act to amplify melt over time, things like polynia and leads and edge fragmentation also amplify ice melt because they are essentially 100% concentration "melting ponds", with the difference that they cause bottom-melt, so you don't see the effects until the floes around go "poof" much later on. For example, Dr. Schroder's model does not capture the mess in the Beaufort at all, where during May massive amounts of heat were accumulated (some 50 TW as I estimated) and is currently a destruction zone for even the thick MYI floes that get pushed in there. That is why I put more trust in Dr. Slater's model, which is based on 'ice-concentration', which captures melting ponds as well as leads and open water next to the ice. And for SIPN numbers in 2015, Dr. Slater's numbers were a lot closer than Dr. Schroder's numbers. However, even ice-concentration in May (by itself) does not correlate very well with ice extent in September either. I don't have the numbers in front of me, but the correlation has something like R=0.35 for the 1992-2015 period (based on NSIDC ice concentration numbers). What I would hope is that Dr. Schoder and Dr. Slater get together and figure out the strength and weakness in each of their models, then include "land snow cover" as a variable, and see if that improves the standard deviation of the predictions of their models.
Toggle Commented Jun 18, 2016 on 2016 melting momentum, part 1 at Arctic Sea Ice
On the subject of PIOMAS development you pointed you stated : You can see this in the PIOMAS data, the loss of multi year ice (thickest) in April aligns with the decline in September extent. and pointed at this graph : http://3.bp.blogspot.com/-tQEfQOe1g6Q/VWdl1ipLvHI/AAAAAAAACAA/88Gdz05FQwI/s1600/Loss%2Bof%2Bthick%2Bice%2Bdrives%2Bextent%2Btrend.png and asked : Now why do you think that would be? MYI by definition survived the prior year's melting season, so thick ice in April will naturally follow last year's minimum extent. (Assuming MYI does not change much in thickness). Your graph is this another indicator that MYI is being killed (which Bitz & Roe as well as Armour et al already suggested). The problem is that there does not seem to be a slowdown of this decline in volume and extent. And neither is there any physical reason why there would be a slow down on a warming planet. PIOMAS suggests that some 700 km^3 annually melts out more than winter freeze adds. And this is very consistent despite freeze-growth negative feedback. The issue may come down to finding out if summer heat melts volume, or if summer heat melts extent.
Toggle Commented Jun 15, 2016 on Crisis in the Cryosphere at Arctic Sea Ice
Hat tip to Wipneus at the forum : NSIDC is back in business. Yeah !! http://nsidc.org/arcticseaicenews/2016/06/satellite-data-transition-complete/ Their numbers are now calibrated to the F-18 instrument, and their sea ice index numbers are also updated. Can somebody tell the CT guys ?
Toggle Commented Jun 15, 2016 on ASI 2016 update 2: closing the gap at Arctic Sea Ice
Chris, I seem to be annoying you, which was never my intent. So this will be my last post on this subject. Regarding Bitz & Roe I have no problem with that paper, nor its conclusions. I think it is a fine piece of work, which indicates convincingly that thick ice is more sensitive to climate perturbations than thin ice. They use a 1D ice growth/melt model to show their point that but I see no reason why it would not be true in the real world. However, they do neither investigate, nor conclude if will be a slowdown in extent (or even volume) after that thick ice thins out. That is outside the scope of the paper. Armour et al attempts to investigate a system of MYI and FYI and their survival ratios affect longer term controls and sensitivity to climate perturbations. It is a mathematical exercise, since there is no physical model involved. I am impressed what they achieved with so few input variables, including finding a time constant by turning the perturbation formula into an AR(1) process. But is remains a math exercise, and therefor their statement that "If this occurs, the Arctic sea ice system would move toward a regime of decreased memory and decreased sensitivity to climate forcing" is simply not sustained by evidence. Maybe that is why they put it in the "Discussion" section and NOT in the "Conclusions" or the Abstract. So if you were to accept ANY advice from me at this point, please take that statement in Armour et al with a very large grain of salt.
Toggle Commented Jun 15, 2016 on Crisis in the Cryosphere at Arctic Sea Ice
Thanks Neven, I hope you are right, but I'm not so confident. I think even an average summer season will still put 2016 close to 2012 by the start of August, as per Dr. Slater's model. And Wipneus' latest AMSR2 assessment still put 2016 currently 135 k km^2 ahead of 2012 on area.
Toggle Commented Jun 14, 2016 on ASI 2016 update 2: closing the gap at Arctic Sea Ice
Thanks Neven, May I note that currenty 2016 is still in the lead for ice extent and area and volume, possibly rivaled only by 2012. Just saying.
Toggle Commented Jun 14, 2016 on ASI 2016 update 2: closing the gap at Arctic Sea Ice
John said (regarding Screen et al) : So the MJJ cyclones have a positive correlation with Sept ice extent, but the lack of MJJ cyclones (clear skies) have an even stronger negative correlation with Sept ice extent, as seen in 2007, 2012 - and to a lesser degree July '15. That is interesting. It seems that that confirms the findings of climate models, which suggest that there will be more "variability" in ice extent as it reduces. Just that the lower it goes, the more sensitive it gets.
Toggle Commented Jun 14, 2016 on ASI 2016 update 2: closing the gap at Arctic Sea Ice
Chris said In essence the issue is that FYI grows back in a single winter. MYI takes years to form. Therefore MYI has a longer memory than FYI. Armour et al defines that memory differently, and either way, it does not say anything about the response to climate forcing. Which is the key to you hypothesis that there is a flatting in ice extent after 2007. Look at it back to basics : Since FYI melts out faster than MYI, we would expect sensitivity to climate forcing to INCREASE, not decrease as Armour suggests, as the Arctic transitions to an ice free state.
Toggle Commented Jun 14, 2016 on Crisis in the Cryosphere at Arctic Sea Ice
Chris said : I have pointed it out - the whole paper. I'm sorry Chris. That is the very definition of what you accuse me of (being "evasive").
Toggle Commented Jun 14, 2016 on Crisis in the Cryosphere at Arctic Sea Ice
We are not even done talking about Armour et al, and why it does not provide evidence for a slowdown in ice retreat on a warming planet, when the next paper is mis-quoted : The 2015 paper Chris just cited shows how the effective increase in heat capacity as the ice cover thins could cause a slow down in the rate of loss of sea ice. It really does not say that, D. It only finds that there is no "increased rate of retreat" as the ice disappears.
Toggle Commented Jun 14, 2016 on Crisis in the Cryosphere at Arctic Sea Ice