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Rob Dekker
California
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Hans, About this polynya, I presented a different theory, that it may be caused by the Coriolis forces driving the Atlantic warm water upward while making a U-turn at that very location against the Gekkal Ridge : http://forum.arctic-sea-ice.net/index.php/topic,1834.msg125728.html#msg125728
As Wipneus reports on the ASIF : According to NSIDC NT sea ice concentration, extent in 2017 is currently the 8th lowest, area is 7th. Looks like we are not going to see any records broken this year.
Lewis, thanks. One point of clarification : I include land snow cover in my model since it clearly affects albedo and thus the heat budget over the Northern Hemisphere. Snow on ice affects the albedo much less and thus in my opinion is not that important for the heat budget.
Thank you Lewis, for this nice overview of prediction models. Early in the melting season, we saw this large negative anomaly of volume, which was caused by an exceptionally warm winter. Luckily, the summer registered a rather cool melting season, which I think is partially caused by that large positive land snow anomaly that Rutgers Snow land recorded : http://climate.rutgers.edu/snowcover/chart_anom.php?ui_set=1&ui_region=nhland&ui_month=6 Some 4 million km^2 of land snow more in June than last year. That has got to leave a significant dent on absorbed heat in the Northern Hemisphere. So I think that the negative volume anomaly in winter and the positive land snow anomaly in summer balanced each other out and we end up with a September SIE that is neither exceptionally low nor exceptionally high. Other years we may not be so lucky.
When you look at the images I posted, it will tell to upgrade the photobucket account to one that supports 3rd party hosting. Photobucket charges $400/year for that and I'm not going to pay that amount of money. So, to look at the images I posted, right-click the image and open in a new window. Thanks !
I find it fascinating to see how low volume makes conventional wisdom (with regards to the influence of weather conditions on extent decrease) partially moot. I remember noticing it for the first time in 2012. Yes. We will probably never know how close to total oblivion we came in 2012, but it may have been pretty darn close. And now in 2017, with most of the major indicators (land snow cover, ice concentration, and ice 'area') suggesting a 2013/2014 'recovery' year was in the works, while 'extent' is still running close to record low, it is blatantly clear that we have dodged a canon ball as you suggested before.
Toggle Commented Aug 11, 2017 on PIOMAS August 2017 at Arctic Sea Ice
Incidentally, in that image, you can also see the 'dipole' that has been dominating the 2017 summer.
Toggle Commented Aug 11, 2017 on PIOMAS August 2017 at Arctic Sea Ice
OK, it looks like 'photobucket' wants me to pay $400/year to be able to post images from my photobucket library. I am not amused, since I've been posting a LOT of such images over years in the ASIB comment sections (including the ones I really care about, like the 1935-2014 thread. Some $10/year would be OK. But $400 is just ridiculous. Let me see what I can do with the old images, but for now, here is the NCEP/NCAR spacial image that belongs in my previous comment :
Toggle Commented Aug 11, 2017 on PIOMAS August 2017 at Arctic Sea Ice
DavidR said : According to the NOAA-ESRL measurements 2017 has been colder than 2013 and 2014 in both the Arctic and the high Arctic (80N+) over most of the May - Jul period and on average. Thanks David, for pointing this out ! As for the where this 'cold' resided during this summer, here is the NOAA spacial plot (May-July, 60-90deg) : Note that the cold was most intense around the Laptev shoreline, incidentally the same location where the land snow lasted longest, and created that significant land snow anomaly this June : http://climate.rutgers.edu/snowcover/chart_anom.php?ui_set=1&ui_region=nhland&ui_month=6
Toggle Commented Aug 11, 2017 on PIOMAS August 2017 at Arctic Sea Ice
Hi Bill, On July 5 you posted the September SIE numbers using the 'daily average' method as opposed to the standard NSIDC method of calculation. On the Forum you asked me to run these numbers through my method to see if the 'daily average' method is better 'predictable'. I just posted the results on the forum here : http://forum.arctic-sea-ice.net/index.php/topic,1834.msg121896.html#msg121896 Result is that no, the 'daily average' method is not better predictable than the standard NSIDC SIE numbers. However, NSIDC 'area' numbers ARE better predictable, obtaining a beautiful 270 k km^2 SD of the residuals. That method still predicts that 2017 will end up where 2013 and 2014 were, so it still predicts a 'rebound' year. But, as noted above, we really should be starting to see a major 'stall' in SIE decline really soon now for that prediction to remain somewhat believable...
Toggle Commented Jul 23, 2017 on Melting momentum: May 2017 at Arctic Sea Ice
2017 is still dropping rapidly, keeping pace with 2007 and 2012. If this continues much longer then my hypothesis that June land snow cover and ice concentration are a good predictor for September SIE will be debunked.
Toggle Commented Jul 15, 2017 on Melting momentum: May 2017 at Arctic Sea Ice
P-maker, back in the 80's, in June the melt line would be outside the Arctic Basin, where there is no MYI.
Toggle Commented Jul 15, 2017 on PIOMAS July 2017 at Arctic Sea Ice
I have another theory, and one we can possibly test : Notice that the reduction in volume loss since the 80's happens mostly during July (see Wipneus' "Arctic Ice Volume Anomaly" graph here) : https://sites.google.com/site/arctischepinguin/home/piomas And remember that in recent years, July is when the melt starts to eat seriously into the Arctic Basin, which during the 80's the melt line was still outside the Basin. So if PIOMAS underestimates the thickness of ice in the periphery of the Arctic Basin (and possibly overestimates the thickness of ice outside the Basic), then PIOMAS would record less ice loss during July in recent years, compared to earlier decades. The estimate does not need to be much : just a 20% error in thickness would explain the (PIOMAS recorded) reduced ice volume melt during July. Does that make sense ?
Toggle Commented Jul 15, 2017 on PIOMAS July 2017 at Arctic Sea Ice
Excellent points, D. Thinner ice could indeed imply increased sensitivity on insolation. That could explain the rapid decline of volume during June of the recent years that is so clearly visible in Wipneus' volume anomaly graphs : https://sites.google.com/site/arctischepinguin/home/piomas But that still does not explain why volume loss in the second half of the melting season (July to September) is actually less than in the 80's.
Toggle Commented Jul 14, 2017 on PIOMAS July 2017 at Arctic Sea Ice
Sorry guys, I'm not sure about that last claim. I'm not sure which year had the least volume loss since the start of July through September. Yet the first claim (that volume loss seems to decrease over time) still stands.
Toggle Commented Jul 13, 2017 on PIOMAS July 2017 at Arctic Sea Ice
And may I note that the volume loss line with the LEAST volume loss is 2012, which happens to be the year with the MOST extent loss.
Toggle Commented Jul 13, 2017 on PIOMAS July 2017 at Arctic Sea Ice
There is something puzzling about the Sea Ice Volume Projection graph as shown by Jim Pettit : http://neven1.typepad.com/.a/6a0133f03a1e37970b01b8d29304f5970c-pi Notice that the recent years (2010-2016) show significantly LESS volume melt than the earlier years (80's or 90's line). Does anyone have a physical reason for that odd difference ?
Toggle Commented Jul 13, 2017 on PIOMAS July 2017 at Arctic Sea Ice
AnotherJourneybyTrain, I am a great admirer of (the late) Drew Slater's probabilistic model. Also note that his model tends to bounce around a bit on the short term, since it is based on ice concentration only, which varies rapidly. For example, it just bounced back sharply to 4.93 for August 29. Let us see where the ice takes us.
Toggle Commented Jul 11, 2017 on Melting momentum: May 2017 at Arctic Sea Ice
Neven said suggests still 5.41 M km^2 for September 2017 Wow, Rob, that's even higher than David Schröder's 5.1 (4.6 to 5.6) million km2. Higher than every ear since 2006, and higher even than rebound years 2013 and 2014. I know. It's a pretty outlandish projection, but that is what comes out if you run the numbers. Very important to note is that my model does not include "ice thickness" (or "ice volume"). Since we had a pretty unprecedented warm winter, ice may be 10% thinner than previous years, which is is not captured in my model. So we may end up in the "happy middle" as was posted before, where volume and albedo effects even out. Something in the mid 4's.
Toggle Commented Jul 8, 2017 on Melting momentum: May 2017 at Arctic Sea Ice
Let me add that in June, there were two periods of a week each that created a dipole with some serious ice compaction. That brought the extent numbers down considerably. The data on 'area' and land snow cover and ice concentration suggest that once the weather turns more neutral or cyclonic, 'extent' will start to stall, and there is not enough heat (melting momentum) to continue the rapid extent decline that we have seen so far.
Toggle Commented Jul 7, 2017 on Melting momentum: May 2017 at Arctic Sea Ice
I seem to be one of the few with an rather optimistic outlook for September minimum. A month again, my entry (based on May data) for SIPN was 5.4 M km^2 for the NSIDC average September : https://www.arcus.org/files/resize/sio/27252/sio2017_june_fig1_n33-700x509.png That was mostly caused by a very large land snow anomaly (4 million km^2) in land snow cover, and moderate 'area' and 'ice concentration' numbers over May. Now the June numbers are in, and the land snow cover anomaly was still there. Here is the Rutger's snow lab data : http://climate.rutgers.edu/snowcover/chart_anom.php?ui_set=1&ui_region=nhland&ui_month=6 The anomaly is still huge : some 3.5 M km^2 more than last year and a larger amount of land snow cover than since 2004. This anomaly has to have an impact on the albedo feedback in June, and thus the amount of heat that warms the Arctic never made it this year. Most of us know that ice 'extent' is not a very good predictor, and 'area' is better. There NSIDC's 'area' number for June came in pretty high (8.51 which is 8.54 after the 'pole hole' adjustment) is higher than most years over the past decade. As a result, the formula I use for June prediction of Sept average (explained here) : https://www.arcus.org/files/sio/25738/sio-2016-july_dekker.pdf suggests still 5.41 M km^2 for September 2017. The difference with May numbers is that the standard deviation of the (hindcast) prediction is 342 k km^2, which is considerably better than the 550 k km^2 SD for a linear trend. This year appears to be a serious test for my (mostly land-snow cover based) prediction method.
Toggle Commented Jul 7, 2017 on Melting momentum: May 2017 at Arctic Sea Ice
Sea Ice Prediction Network finally published the June report (based on May data) https://www.arcus.org/sipn/sea-ice-outlook/2017/june The median Outlook value for September 2017 sea ice extent is 4.43 million square kilometers. Looks like an "in-the-middle" prediction, possibly balancing low volume data with low melting pond data.
Toggle Commented Jul 4, 2017 on Melting momentum: May 2017 at Arctic Sea Ice
A bit dated, but since PIOMAS numbers are now released mid-month as well (thank you Dr. Zhang!) we had a PIOMAS update June 15. Wipneus reports on the PIOMAS forum thread : the volume gap with 2012 has been deminished from about 1. 48 down do 0.38 [1000 km3] Which is quite surprising, but explains a lot : It appears that 2017 has lost much of its lead in volume loss due to moderate melt in the Arctic over the first weeks of June. I can't suppress the notion that this is caused by the lack of melting momentum that Neven already talked about, and I believe that this is at least partially caused by the land snow cover anomaly, which keep things cool in the Arctic. We are not out of the woods yet though. The latest PIOMAS numbers are still record low, and although a significant land snow cover remains, it is still too early to exclude an extreme outcome in September. If this (persistent) land snow cover is an indication, 'extent' should really start to level off over the coming weeks, away from its current position among the top three. We will see...
Toggle Commented Jun 23, 2017 on PIOMAS June 2017 at Arctic Sea Ice
Hans, Why not explain your prediction beforehand ? Is it PIOMAS record low volume ? Also, 2012 doesn't decline that much over the next 10 days. Only 67 k/day if I recall. If you claim a significant decline over the next 10 days, why not go with 2010 ?
Toggle Commented Jun 18, 2017 on Melting momentum: May 2017 at Arctic Sea Ice
Another problem with incorporating 'remaining volume' or 'FYI thickness' in my linear regression method against 'extent' is that there may be non-linear effects : if ice melts, it adds to 'extent' as long as it has ANY thickness. After that it disappears quite suddenly.
Toggle Commented Jun 12, 2017 on PIOMAS June 2017 at Arctic Sea Ice