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Rob Dekker
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Neven, what happened ?
Toggle Commented 4 days ago on In memoriam: Andrew Slater at Arctic Sea Ice
And the NSIDC Sept. average SIE in all likelihood will be in the 4.25-4.5 range, probably very close to Rob's prediction. My prediction (back in June) was 4.1. In reality, I think the NSIDC Sept. average SIE will end up much closer to 4.4, which was Andrew Slater's projection, and the average of SIPN.
Toggle Commented 4 days ago on ASI 2016 update 7: minimum time at Arctic Sea Ice
About predictions : When your model is consistently making skillful predictions, it increases your understanding of the system. For me personally, as a participant in SIPN, I have come to respect Dr. Slater's modeling as an example of how to do better forecasts of September ice extent. He used ice-concentration as a precursor for September extent, and was very successful in doing so. This year, his forecast (of 4.4 M km^2 for September average) will again be pretty darn close to "spot-on", which suggests he is on the right track in understanding the system better than anyone else. I sincerely hope that his work (incorporating land snow cover in the model) will be continued by his colleagues. Dr. Slater, I miss you. May you rest in peace.
Toggle Commented Sep 20, 2016 on In memoriam: Andrew Slater at Arctic Sea Ice
Bill said Like many others, I also thought the response was a tad over the top. I read the post by Kevin and Tamino's response. I don't see anything "over the top" there. I think that Tamino did not understand the point that Kevin was making about the 15% cut-off. And frankly speaking, neither do I. Regarding the "pole-hole" argument, this 24k (AMSR2) or 29k (NSIDC) difference is a very small speck on the radar. Jim Hunt has shown that there was a lot of low concentration ice at the NP this year, but it would be hard to argue that this was less than 15% concentration. So this pole hole would NOT have influenced ice "extent" at all, and would have influenced ice "area" only by something less than 24-29 k km^2. Something that would get lost in the noise. So again : What's the big deal ?
Toggle Commented Sep 20, 2016 on ASI 2016 update 7: minimum time at Arctic Sea Ice
Kevin said : Tamino - much as I usually respect him - assumed I was a denier and basically called me an idiot. Do you have a link to that ? Regarding the "Pole Hole", NSIDC' pole hole has reduced to 29 k km^2 since 2008. What's the big deal ?
Toggle Commented Sep 19, 2016 on ASI 2016 update 7: minimum time at Arctic Sea Ice
wayne said : Does the computer see what we can? Is that what the computer recognizes? Then there is a problem. Sorry, wayne. You lost me.
Toggle Commented Sep 18, 2016 on ASI 2016 update 7: minimum time at Arctic Sea Ice
Jim said : When they feel able to head across the North Atlantic to Bristol remains to be seen. After all they went through, I'm sure they can pull off the last leg of their circumpolar journey. Congrats for these lads !
Toggle Commented Sep 18, 2016 on ASI 2016 update 7: minimum time at Arctic Sea Ice
Congratulations to Northabout in completing passing the NE passage AND the NW passage in a single season. The first British vessel to do so. Great accomplishment, and an indication of the state of Arctic sea ice this melting season.
Toggle Commented Sep 17, 2016 on ASI 2016 update 7: minimum time at Arctic Sea Ice
viddalo, Listened to that Bristol radio episode. For starters, just to be sure, are you the Norwegian guy speaking ?
Toggle Commented Sep 17, 2016 on ASI 2016 update 7: minimum time at Arctic Sea Ice
Wayne and John, you guys are seriously confusing the thread here. John said : Just pointing out that the '15% method' allowing about 85% to be counted as ice does not apply to the sea ice area calculation, which Neven also has clarified to you. That is incorrect. Neven explicitly stated that the 15% cut-off also applies for 'area' calculations : I believe he is correct for NSIDC's "area" calculation, but for CT area I'm not so sure. Wayne said a lot of things about the 15% cut-off rule, but may be best summarized with this quote : The 15% rule is past its time, we must go to the highest resolution possible readings, count sea ice or water per acceptable area (as small as resolution allows). First of all, the 15% rule is independent of the resolution that satellites measure ice concentration. Good old SSMIS NSIDC may run at 25 km^2 resolution, and modern AMSR2 at 3 km^2 resolution, but the 15% rule applies to both. That is because the 15% rule is there because to uncertainty in microwave measurements by the satellite. If we would lower that threshold, then "false-ice" starts to pop up in various unexpected places. Even with the 15% rule, you can still see "false ice" pop up every now and then (on the Bremen AMSR2 images for example) and that is why extent/area providers have to use masks to avoid that such "false-ice" detections affect the resulting extent and area numbers too much. Either way, wayne, it is REALLY not clear what exactly your problem is with the 15% rule.
Toggle Commented Sep 16, 2016 on ASI 2016 update 7: minimum time at Arctic Sea Ice
NeilT said For instance if I subject the surface of water to -100c it's going to freeze before the heat from the water column, 20m below, can transfer through to the freezing point? That is possible, but remember that the heat transfer from the warm (mixed layer) water below will be mostly done by convection. Equilibrium is reached once the ice will bottom-melt as fast as the super-cold atmosphere can transfer heat through the (thin) ice layer. Until of course the heat of the mixed layer runs out, because that is when convection stops. Did you do the experiment (with ice cubes in salt/fresh water) ?
Toggle Commented Sep 16, 2016 on ASI 2016 update 7: minimum time at Arctic Sea Ice
On August 31 I said : Because of this, I suggest a late "minimum" this year. Man, was I wrong about that one..
Interesting side note : during melting, heat CAN be trapped below the ice. If waters are very still, then a thin layer of cold fresh melt water can form right below the ice, which can block the heat from warmer salty water below from reaching the ice/water boundary. This is why an ice cube in salt water will actually melt slower than an ice cube in fresh water (where convection will move the water around). You can try that experiment at home. The insulation-effect is destroyed if you stir the water. This is another reason why in stormy weather ice melts faster.
Toggle Commented Sep 15, 2016 on ASI 2016 update 7: minimum time at Arctic Sea Ice
Bill said : an energy bleed rate of 200 Watts/sq metre at the surface would take almost 5 days to lose 84MJ - and about 3 times as long if 250 MJ needs to be lost out of that water column. Thanks for correcting my calculation, Bill ! Much appreciated. As for ice forming over a warm mixed layer, basic physics would say that is not possible. After all, convection would set in if surface water is colder than mixed layer water. So we would expect that 20 meter water column too loose all its heat before freezing can set in (even freezing by snow falling on the water). Heat can definitively be trapped below the halocline (at some 20-50 m below the surface) and that heat can come out during a storm, but in the mixed layer salinity levels are not different enough to 'trap' any heat AFAIK.
Toggle Commented Sep 15, 2016 on ASI 2016 update 7: minimum time at Arctic Sea Ice
navegante said They were showing more than three degrees C over norm (which is -2C the lowest). That is +1C or more of absolute SST, even above fresh water melting point!? So that is why I find surprising how fast the refreezing was. Your statement is correct. Even when the upper mixed layer is only 20 meters, if the water is 3 C over freezing, there is 84 MJoule/km^2 to get rid of before it can freeze over. With even an over-estimated 200 W/m^2 heat loss to space, it will take 5 days for that water column to cool down to freezing. So that water that just froze over was colder than 1 C, or it had more than 5 days to cool down. Either way, that DMI SST map is suspect.
Toggle Commented Sep 14, 2016 on ASI 2016 update 7: minimum time at Arctic Sea Ice
What ? Andrew Slater died ? No, no, no ! That can't be. He is a young guy, at the peak of his life, brilliant scientist. Famous for his work on all aspects of the Cryosphere, notably Arctic sea ice, permafrost and land snow. And a great contributor as IPCC WG1 author. Please tell that this is not true ! Please !
Toggle Commented Sep 13, 2016 on PIOMAS September 2016 at Arctic Sea Ice
wayne said It is very serious if there is dispersion, like this year. We are merely talking about 2.55 million square kilometers per 4 million margin of error. As noted before, if you are concerned about the margin of error that the sea ice "extent" metric causes due to ice "dispersion", then please, my all means, switch to sea ice "area". After all, sea ice "area" is indifferent to ice dispersion, and especially now that the melting ponds are freezing over, provides a good metric for how much ice there is in the Arctic.
Toggle Commented Sep 11, 2016 on PIOMAS September 2016 at Arctic Sea Ice
Kevin wrote : Yes, this is exactly the same thing I wrote (not having read wayne's comment yet) about the marginal ice zones. The marginal ice zones used to be on the periphery of the pack. Now they're just about everywhere. Maybe sea ice "area" is a better metric than "extent" for the sort of analysis that you and wayne are suggesting.
Toggle Commented Sep 10, 2016 on PIOMAS September 2016 at Arctic Sea Ice
Wayne, the 15% rule for extent is reasonable, given that the satellite observation error is in that same ballpark. If they would lower that threshold, you would see a lot of "false ice" interfering with the data. Also, regardless of the level (15% or 20% or 30%), if the same threshold is used for all historic data, you can make a fair comparison between years. And that is exactly what NSIDC data provides.
Toggle Commented Sep 9, 2016 on PIOMAS September 2016 at Arctic Sea Ice
I find the PIOMAS update on ice volume a lot more believable than the DMI ice volume update : Note the sudden drop in ice volume from 'average' to almost record low in the second half of August. This while in 2015, over the same period, DMI suggested that ice volume was increasing rapidly. With such fluke adjustments (undoubtfully caused by assimilation of actual ice concentration observations) DMI's volume graph is mostly providing fodder for climate science deniers (as it DID last month), and is a hassle for the rest of us trying to explain that DMI's volume data should be taken with a grain of salt. I wish DMI would simply report PIOMAS numbers and discard their own mediocre volume product.
Toggle Commented Sep 5, 2016 on PIOMAS September 2016 at Arctic Sea Ice
Jim, ""Could Northabout Sail to the North Pole?"" In the forecasts : it looks like Northabout will have mostly tail wind (smooth sailing) across the the remainder of the NW passage once they have their repairs done in Tuk. As for the theoretical trip to the NP, your AMSR2 image suggest that beyond 86N there is a fairly low concentration ice path all the way to the NP, which is quite unusual by itself (so Serreze is right in my opinion). But again looking at the forcasts link above, that strech of low concentration ice may become more "open" water in the week to come. Temp forecast (for the NP area) is well above normal, which means there will not be much ocean water freezing yet. There won't be much melting either though, since the sun is quickly loosing strength now. But the winds over that low concentration ice will be mostly towards Wrangel Island, which means (Coriolis force) that ice movement will be towards the Laptev, which will further lower the ice concentration in that band. How much dispersion, and will it be enough for a clean open path to the NP ? That is hard to tell, but we should know in about a week and before the real refreezing starts in the NP area.
Toggle Commented Sep 4, 2016 on 2016 Mega-Dipole at Arctic Sea Ice
Cato said He is not even respected by his own colleagues. Where does this remark come from ?
Toggle Commented Sep 3, 2016 on 2016 Mega-Dipole at Arctic Sea Ice
I'm sorry that I came across quite harsh with my Feynman quote and statement that climate models need to be "discarded" if they can't even predict the past. What triggered this is my discontent with many IPCC GCM models and their inability to predict Arctic Sea Ice development. Since 2007 it was already suspected and by 2012 is was absolutely clear that we should discard a good number of these models since they simply do NOT predict even the past few decades with even the slightest degree of competence : And it was not just ice extent, but also ice volume is heavily underestimated : These are the models that appear in the IPCC reports and, as prof. Wadhams again clarifies in his interview (above), they create the false impression that Arctic sea ice in summer will disappear somewhere at the end of this century, while in fact the trend of volume decline suggest that summer sea ice in the Arctic will be gone in the next 5 years or so. In fact, the past volume trend line hits virtual-ice-free around 2016, and we may have just been saved by two outliers (2013 and 2014) and perhaps saved by the bell (cold June and July) in 2016 as well. Yes, these models can be improved. And it is not even unclear where they need to improve. For starters, they should get (the trend) in loss of land snow cover right, since that impacts sea ice cover very significantly (as the statistical models suggest). Also, some of these models don't even have melting ponds. I suggest that the GCM IPCC models get a frank review, and that we discard the ones that cannot even predict the past couple of decades. THAT is what I meant with Feynman's comment, and I believe that we do mankind a great favor is explaining how much more serious the developments in the Arctic are than the currently used GCMs suggest.
Toggle Commented Sep 3, 2016 on 2016 Mega-Dipole at Arctic Sea Ice
Bill, since 2016 is now 9 days ahead of 2007 on ADS/JAXA, and still going down briskly, I put my bets on 2nd place.
Abbott said : The point about experiments is curiously missing from all this 'climate science' is it not, btw? While it is true that humanity is running one single 'experiment' (there is no Planet B), the issue of experiments depends on the question you are asking. For example, when we are asking to predict September sea ice using data from earlier months, every year is a new experiment. Since we have consistent data since at least 1979, we have run 36 experiments already. Any model projecting the outcome of the next 'experiment' (Sept 2016) can and should be tested for past performance. And if it can't predict the past, it should be discarded. That is the nature of Feynman's statement.
Toggle Commented Sep 2, 2016 on 2016 Mega-Dipole at Arctic Sea Ice