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"Fast ice holding the river back actually increases the effect the river has on sea ice retreat." That could be a (minor) factor in the negative one-year autocorrelation that appears still to be in effect.
Rob D, "...high variability that comes with weather sensitivity of ultra-thin ice..." sounds like a good capsule description of the 2013 melt season - and as you imply, yet another instance where the models may need to play catch-up. We're seeing another manifestation just recently: as Neven observed in the OP, "...a large part of that record amount of first-year ice at the start of the melting season has been preserved..." So there is more remaining to melt towards the end of the season (from more conducive weather, bottom melt, wave action etc.) and the declines in area and extent are relatively steep for this time of year. I expect that PIOMAS will also have a drop in anomaly over the next month or so.
Toggle Commented Sep 10, 2013 on PIOMAS September 2013 at Arctic Sea Ice
Rob and Wili, There was some lively discussion of the "rebound" topic last year at http://neven1.typepad.com/blog/2012/05/arctic-sea-ice-loss-and-the-role-of-agw.html?cid=6a0133f03a1e37970b01630551734e970d#comment-6a0133f03a1e37970b01630551734e970d, referring to a paper by Tietsche et al that found recovery over a two-year interval following a shock. See also Chris Reynolds' discussion at Dosbat http://dosbat.blogspot.co.uk/2012/09/sea-ice-albedo-changes-and-seasonal.html of the Notz and Marotzke paper on AGW vs. other factors. The evidence of 2013 is for two different causes: a rebound early in the year, probably owing to heat loss from open water at the end of the previous melt season, and later a slow melt from cloudy and cool conditions. Whether the latter is natural variability or a longer AGW-related causal chain, as Jai Mitchell suggests, is a good puzzle for the scientists. [fixed links; N.]
Toggle Commented Sep 8, 2013 on PIOMAS September 2013 at Arctic Sea Ice
The excellent series of annotated maps posted by BornFromTheVoid over on the forum raises the question of whether this storm will cause a large area of sea ice to detach, as did GAC-2012. Inferring from wind direction over the next few days together with Coriolis apparent force, a notable candidate is the swathe of relatively thick ice N and E of Severnaya Zemiya. With the current storm less intense and widespread than last year's, and the ice less primed for detachment, I would not expect this area to cut loose in the few days following the cyclone.
Hmmm, the thicker ice (relative to last year) in the Kara Sea is sandwiched between anomalously warm water to the west, on the other side of N.Z. island, and early loss of snow cover to the southeast in Siberia. Wonder how long it will hold out.
Toggle Commented Jun 9, 2013 on PIOMAS June 2013 at Arctic Sea Ice
Peter, your counterexample is flawed on two counts. First, the mean significant wave height averaged over the Mediterranean Sea is less than 1.5 meters, even in winter. Second, if you look at the animation above, it's clear that the ratio of ice edge to water area in the freezing region is far higher than it would be under normal freezing outward from the pole. Your views seem to be at odds with oceanographer Luc Rainville, who was quoted in Discovery News as saying that sea ice muffles all waves "like a big damper."
Toggle Commented Nov 12, 2012 on Bilateral freezing at Arctic Sea Ice
hmmm, it seems that the surrounding ice would reduce wave action in the enclosed open water. This would cause 1) faster re-freeze in that locale; 2) smoother surface, probably even more than is normally characteristic of first-year ice. If the smooth area survives ice pack dynamics during the winter, it would have different ponding behavior the following spring. See the Perovich & Poshenski study on how FYI differs markedly from multi-year ice in its seasonal albedo and melt pond formation. SekeRob commented on the latter; "...it's nice and smooth and promotes much larger and interconnecting ponding than ... MYI." In a similar vein, Flocco et.al. in JGR found that ice beneath ponds melts up to three times faster than bare ice. Higher melt rate, earlier start. You can see this as a steep downslope in the anomaly graphs. There's a lesser but still reinforcing factor that Lodger pointed out in the _PIOMAS September 2012 (minimum)_ thread: Earth' solar aphelion comes after the northern summer solstice, so ToA solar irradiance is slightly higher before the solstice than after. This consequence of the Earth's elliptical orbit multiplies the effect of lower albedo early in the melt season. So there are two trends that appear to go in in opposite directions, on just slightly different timescales. The first is widening seasonal percentage swings in sea ice area, as illustrated by Jim Pettit's graph. crandles noted one possible cause in an earlier post: "One way you can get more ice at maximum in the seasonally ice free version is that it misses out on autumn/fall snow cover which is excellent insulation compared to just ice." On a y/y time scale, Arctic ice extent (though not volume) has had a one-year negative autocorrelation. For some discussion sans consensus, see the thread _Arctic sea ice loss and the role of AGW_. I think Chris R also addressed the topic in his Dosbat blog. This rebound behavior - especially following record ice loss years - is one reason Notz & Martotzke ruled out self-acceleration as a dynamic in sea-ice cover. (see their Figures 1(b) and 1(d), paper available here.) The correlation seems to have weakened in recent years. For September extent, if not for March, it may have even flipped to positive. A big question for 2013 is whether the recent pattern continues. The combination of trapped heat (noted above by Apocalypse4Real) and lower albedo from earlier and more widespread ponding seems to favor another extreme low in sea-ice cover. That could be a harbinger of self-acceleration taking hold. "Accentuate the positive," as the happiness researchers like to say - except here we are dealing with climate feedbacks.
Toggle Commented Nov 12, 2012 on Bilateral freezing at Arctic Sea Ice
I was wondering how the climate models fare at predicting minima, and how much improvement CIMP5 shows over CIMP3. Haven't found anything conclusive, however... The CIMP3 models, used as the basis for the IPCC AR4 (2007) report, were way off but in a surprising way. If you look at the month-by-month model values (Fig 1 in Stroeve et.al. 2012, http://www.agu.org/pubs/crossref/2012/2012GL052676.shtml), their errors vs. observed mean increase markedly from January through April. So where reality wrong-footed the models was not so much the amount of peak-to-trough melt (by area/extent), but the lack of re-freeze afterwards. The CIMP5 ensemble has a similar monthly pattern of errors - at least on data through 2011 - though to a lesser degree. This reinforces the idea that we need to figure out what caused the melt anomalies to shift earlier in the season.
Toggle Commented Sep 9, 2012 on Minimum open thread at Arctic Sea Ice
Great post, Chris. btw I think you mean "if the surface temperature rises, that heat flux reduces... " The hunt for a sole silver bullet is tantalizing. But if we assume that the big volume drop in 2010 was caused by an interaction among several elements rather than mainly by a single one (such as WACC), we may find other clues implied by successive y/y changes. Re: FYI frozen onto bottom of thick ice - during the the day 140 - 170 interval, aren't we looking at slower formation of this FYI rather than faster melt? In the month before the solstice, total volume has been roughly flat in recent years, while area/extent accelerates downward: so freezing must be occurring within the pack. If so, the lower heat flux through thicker ice would support crandles' hypothesis, not counter it. Maybe comparing the time-shift in downtrends will yield some insight. Following the big drop in ice thickness in 2007, the downslope in volume anomaly has been earlier and/or steeper than before. This seems consistent with either less-rapid freezing of FYI under thick ice (each passing year, less MYI where this can form) or with more rapid progression of edge melt from the peripheral oceans to the Arctic Basin (@Chris R 3 September 2012 10:22 on Dosbat blog). Comparing to the volume/area chart, http://tamino.files.wordpress.com/2012/09/thick_yy.jpg there's a deviation from Feb-Apr 2010 that seems plausibly explained by WACC. But as pohjois noted in the Tamino blog, "it is year 2009 which is the first example of the new regime – maximum early in the season..." So it looks as though WACC was additive to some influence on ice thickness that was already operating in summer 2009, with possible foreshadowing in prior years.
Terry, good point on multi-year ice. In addition to more portals for advection as the archipelago fastness weakens, there could be a snow-cover mechanism for self-acceleration. This from a Nature Climate Change (July 2012) piece summarizing Perovich and Polashenski (Geophysical Research Letters 39), which Neven referenced in the Arctic sea ice loss and the role of AGW thread: http://www.agu.org/news/press/jhighlight_archives/2012/2012-05-15.shtml#three "Seasonal ice tends to accumulate only thin layer of 5cm of snowpack [vs. 20-30cm for MYI]... melts more quickly in the early summer, revealing ice and melt ponds... albedo of seasonal ice drops to 0.3.... Over the course of the entire season, nearly 40% more energy enters an ocean system with seasonal sea-ice cover than one with multiyear ice..." Chris R, the indicator that Notz & Marotzke use is whether a strong excursion is followed by a reversal. (Granted this is a bit simplistic, as self-acceleration mechanisms could operate on a periodicity of longer than one year - or shorter). The big YtY drop was in September 1997; '98 is significant for the lack of reversal. However, that series was an isolated instance until recently. So I agree with their conclusion, on data through 2010, that external forcing - namely CO2 - was mainly driving sea ice loss. The question is whether the last few years will prove to be the beginning of a persistent SA influence. I see this topic has already been pretty thoroughly thrashed in the AGW thread back in May, so I'll wait for the experts to parse the latest data. Ice volume is probably a better indicator than area/extent, as you and others have argued. However, as volume trends down, there is less latent heat of fusion to carry the memory signal from one year to the next. So we need to look for other heat stores (e.g., R. Gates on thermal gradient across the ocean skin layer) and other possible mechanisms of SA - if the melt continues beyond what external forcing would cause.
Thanks for the graphic and link, Lodger. Notz & Marotzke, 2012, "Observations reveal external driver for Arctic sea-ice retreat" http://www.mpimet.mpg.de/fileadmin/staff/notzdirk/2012GL0510 On the topic of self-acceleration vs. external forcing, Notz and Marotzke state: "... the observational record is incompatible with self-acceleration dominating the observed sea-ice evolution. In the time series of year-to-year changes (Figure 1), every strong negative year-to-year change in sea-ice extent is followed by a positive year-to-year change and vice versa." Not entirely true, viz. September 1997-98 in their Figure 1. Now we have another instance in 2011-12. Per the discussion of bifucation (above and in other thread), 1998 was an early indication, and 2012 a confirmation, that self-acceleration is becoming a contributing factor. Albedo flip is one possible cause, methane spike another.
The steep drop in recent days is probably attributable to the extra edge area of the two big detachments. Now those are mostly gone and the remaining thicker ice won't melt much, except for advection through the Fram Strait. Once that slows down after the next few days, we'll see nearly flat graphs through the end of the melt season.
Yes, heat absorbed by Earth's system as opposed to transferred from one part to another (e.g., heat from deeper water melting surface ice). So duration factors in the amount of time that extra open water remains from the cyclone until re-freeze (or Arctic sunset). Whether it's surface or bottom melting doesn't matter as long as there's less ice than there would have been absent the storm. The amount would be some fraction of your calculated result - after adjusting from extent to area - on Neven's assumption that some or all of the "flash melt" ice eventually would have gone anyway.
Toggle Commented Aug 14, 2012 on August SEARCH Contribution Update at Arctic Sea Ice
iceman is now following Neven
Aug 14, 2012
Chris, that's a useful calculation to estimate the total heating effect of the cyclone. For simplicity we could go for gross rather than net, which would require an estimate of amount of heat the storm expelled through the troposphere (among other things). First approximation would be: reduction in area, ~ 0.33 M Km^2 x duration of ice loss, say through the end of the melt season x change in albedo x insolation at latitude (how to account for average cloud cover?) Sound about right?
Toggle Commented Aug 14, 2012 on August SEARCH Contribution Update at Arctic Sea Ice
iceman is now following The Typepad Team
Aug 14, 2012