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wayne, quoting your "AS far as the guys you cited, they should admit failure," I wonder, why? Of the two researchers JC was highlighting, Wadhams seemed to only be giving a tentative opinion, not what I would consider an actual prediction: "2015 is a very serious prediction and I think I am pretty much persuaded that that's when it will happen." As for Maslowski, he certainly made something that could be considered a quantifiable prediction, i.e., "2016 +/- 3 years;" (and, as I recall, that was qualified as a 95% likelihood)... i.e., the data indicated to him a 95% chance that the arctic would first become "nearly ice-free" at some point in the melt season, in at least one of the years from 2013 to 2019. Why should that be considered a failed prediction? If 2019 should indeed bring the first year that the arctic becomes nearly ice-free at some point, would you still consider Maslowski's prediction to have been proven wrong?
3.4 My last month's guess was 3.8; my rationale is mostly heuristic. Initially I thought that with volume decreasing every year, at some point each successive year could easily yield a new record, culminating with an ice-free (<1m) September in 2016 +/- 3 years. On the other hand, I also supposed that right before the end, the area and extent could indeed rise, like a drink where the few remaining ice cubes have been replaced by a slushee. What I didn't expect was to see PIOMAS volume actually rise this year - so last month I figured all bets are off, and there could indeed be a slight recovery this year - hence, 3.8 However, one thing I am still struck by, is that it seems to me that everyone who has said it would be nearly impossible to break last year's record, either because of the early cool period or statistical methods, is comparing, contrasting or correlating this year to past years... I realize we do not have the advantage of future years' numbers with which to compare, but I do recall a good argument in recent years that there was a significant shift in various graphs between 2005 and 2010 (IIRC), and that 2007 was more likely to be a dragon-king event rather than a black swan. From my admittedly purely gut perspective, are not 2011 and 2012 more likely to be confirmations of this, and not more black swans? If so, I would think that 2013 will more likely correlate to the melt mechanisms of the future (or even less predictably, a present in transition) rather than the past. I realize this is not at all helpful in the quest for an actual reason for a particular prediction or expectation based on the only data numbers we have available, but the call was put out for all input, and this one is mine. One last thing - if GAC2012 melted out an area last year that was going to melt out anyway - just earlier - could PAC2013 be its converse? i.e., it only delayed the melt which was inevitable? I still wonder about the PIOMAS volume, though... I suppose only time will tell.
@John Christensen - quoting from the link: ...the freezing point of sea water varies. For every 5 ppt increase in salinity, the freezing point decreases by 0.28 degrees Celsius (0.5 degrees Fahrenheit); thus, in polar regions with an ocean salinity of 35 ppt, the water begins to freeze at -1.8 degrees Celsius So, for FYI (for which there has not been enough time for the ice to 'freshen' much), both top melt and bottom melt will begin at somewhere between -1.8 and 0 degrees Celsius. For the FYI that survives and becomes MYI, more salt will have been 'washed out', as you say. I don't know if this is the only mechanism by which the salinity of older ice is reduced, but in any event the effect would be that older ice requires a higher temperature to melt.
@John Christensen - Salt/brine migrates out of sea ice over time. See http://j.mp/sea_ice_salinity - follow the link at the end for more fun facts about MYI. (oops - previous post had an interfering semicolon)
@John Christensen - Salt/brine migrates out of sea ice over time. See http://j.mp/sea_ice_salinity; follow the link at the end for more fun facts about MYI.
3.8 million square kilometres. And I am a 1.5 for the last 5 years, 3 here... I can follow some of the math, and I watch it year-round (for that matter, is there an out-season any more, especially considering this last year?) I did not post an estimate in May, but if I had, it would have been 4.0 - I have revised it downward due to 2 impressions: a) I was impressed that, despite cold temps, 2013 maintained almost the same track as 2012 right into the first week of June. b) PAC-2013, and the many who expressed concern that the broken ice would tend to melt out quickly later in the summer. After all I've read here, I've come to the conclusion that extent is least important as a measure of total arctic ice and what it will take to melt the remainder, compared to volume or area. Volume is the closest, but it seems thickness is somewhat overestimated in FYI, so how reliable is the volume estimate? I don't see how minimum volume won't return to setting new records (in spite of the pause it seems to be taking) - has there been any substantive increase in negative feedback, or decrease in positive feedback? I expect area will set a record as well; I'm not really sure why extent is given more press than area or volume - isn't it reported more for navigational purposes than anything else? Has anyone actually modeled what is expected to happen during 'the last days', WRT break-up, divergence, top/bottom/edge melting, etc? Would it be a surprise to see extent flatten or even increase just before the ice disappears completely (slushee will spread out more than ice cubes will)? The bottom line is, I think, if we have a cliff like last year, even extent will set a new record; if there is no special event, it will be second-lowest on record. Just another amateur's guesstimate, of course. Ultimately, though, I think Maslowski will be validated - 2016 +/- 3 years is the beginning of the end of arctic ice. Then, the next experiment begins - when will we need to change all the titles to 'Arctic Sea Water'?
RealityBytes is now following A-Team
Jun 4, 2013
Quoting A-Team: Dan Fahrenheit's scale -- which the US will use until hell freezes over -- was actually more useful: 0ºF is the freezing point of brine (water saturated with salt, 26% ). In other words, liquid water can stick around until −40 °C, as it might in a tight protected brine channel. I didn't know (or forgot) that 0ºF is the freezing point of brine-saturated water - but wouldn't that be -17.7ºC, not -40, for the limit of liquid water? (given std atmosphere of course) (Or did -40 leap to pen because it's where C and F agree?) What is the salinity and melting point, anyway, of typical FYI - how far below 0ºC can we start to actually see melt that does not re-freeze? -John (I'm a long-time reader but rarely find I can add anything - except I've an idea I might be able to present soon, re: explaining things in simple terms that might get more attention - I hope)
Toggle Commented Apr 20, 2013 on Perception of the Arctic at Arctic Sea Ice
Ian: The 'index' at the end was causing the problem. Watch the periods too, make sure they aren't part of the link: http://iup.physik.uni-bremen.de:8084/amsr2 Looking at that link, I have been noticing the 'Laptev Bite' (or was it Bight?) is becoming more of a BigGulp... and although freeze-up is occurring in some places, this seems to keep melting away... I wonder how much of it might still pass the 30% or 15% threshold this season?
RealityBytes is now following The Typepad Team
Sep 19, 2012