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UCMiami

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Re: 2019 vs 2012
« Reply #50 on: July 16, 2019, 07:00:27 AM »
Killian - three letters GAC = Great Arctic Cyclone which hit on Aug2 and devastated huge sections of ice - mostly by bringing deeper warmer waters to the surface and stirring/dispersing the ice.

To be noted also in your listing of rapid extent loss weeks - we just experienced one in July this year losing 1M km2 in a week - 9M to 8M

As posted by Philopek here in the melt season thread:
https://forum.arctic-sea-ice.net/index.php/topic,2591.msg213000.html#msg213000

Killian

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Re: 2019 vs 2012
« Reply #51 on: July 16, 2019, 07:44:21 AM »
I've been wondering what it was about 2012 that made it loose so very much more ice than the other years, turns out that it didn't.

You'd need to include a look at area and/or volume to determine that, not extent.

As for extent, the difference between '12 and '16 comes down to two weeks, one in Spring, one in early July, with nearly 1M km sq reductions. The latter, i was just reminded, was the period of the Great Arctic Cyclone, so there was definitely some very real ice loss during that week. Perhaps not during the first one in Spring.

See above.

binntho

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Re: 2019 vs 2012
« Reply #52 on: July 16, 2019, 07:57:01 AM »
I've been wondering what it was about 2012 that made it loose so very much more ice than the other years, turns out that it didn't.

You'd need to include a look at area and/or volume to determine that, not extent.

Yes, well that was the whole point, the point I was trying to make: You need to look at area to come to that conclusion.

I've been wondering why a year like 2019 is struggling so hard to get any where near 2012 extent wise - based on the misconception that the 20% difference in extent between 1st and 2nd place was based on 2012 loosing 20% more ice than 2016, and struggling to see where such a massive difference in melt could have come from.

But when you look at area, the difference is only 8%. Still a decent number, but nowhere near as massively different compared to 2016 or indeed other years. And most of the difference extent wise is just random (if not quite Brownian) movement of existing ice.
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Killian

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Re: 2019 vs 2012
« Reply #53 on: July 16, 2019, 07:58:19 AM »
Killian - three letters GAC = Great Arctic Cyclone which hit on Aug2 and devastated huge sections of ice - mostly by bringing deeper warmer waters to the surface and stirring/dispersing the ice.

Ah. Right. I should have made that connection. Well, then, the debate about whether it mattered much to 2012 and/or will matter in this or future years is pretty much settled. As I noted above, remove that and the other springtime big loss week, and the difference between '16 and '12 disappears.

But what dropped the extent @ 1M km sq in the spring for the other half of the difference?

Quote
To be noted also in your listing of rapid extent loss weeks - we just experienced one in July this year losing 1M km2 in a week - 9M to 8M

Yes. Well aware. It was pretty warm, and until recently export via Fram and and Nares has been high. Westerlies and the dipoles have always been discussed as the primary causes of the great loss in 2012, but now I'm not so sure - unless those were the causes of the spring 2012 big melt week. I think they explain '12 being otherwise equal to '07 and 2nd to '16 - note the upside-down, flattened Bell Curve shape showing larger than normal losses at the end of the melt season - but the real losses that drove '12 almost 1M km sq lower than 2016 would be came long before Sept.

grixm

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Re: 2019 vs 2012
« Reply #54 on: July 16, 2019, 08:35:43 AM »
DMI's thickness model shows pretty different results to PIOMAS. Where PIOMAS has 2012 and 2019 pretty much tied for volume at this point, 2019 is lagging pretty far behind according to DMI: (click to play)

I asked what the difference between these models are in the PIMOAS thread and why no one seems to talk about DMI, didn't get a response.

oren

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Re: 2019 vs 2012
« Reply #55 on: July 16, 2019, 09:00:15 AM »
A. 2016 also had a GAC of sorts, that contributed a lot to late season area loss. The GAC was later than 2012's.
B. 2016 nearly tied 2012 for area in the CAB, per the UH AMSR2 measure. The difference with 2012 was in other regions (CAA, ESS and maybe others) that didn't clear out in 2016. The CAB "tie" came late and went away fast.
C. 2016 had a very early min date, while 2012 managed to linger to a late min date. On Sep 8th the 2012-2016 difference was much smaller.
D. The early min in 2016 came about partly because of lots of open water and low concentration ice in the region near the pole.

binntho

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Re: 2019 vs 2012
« Reply #56 on: July 16, 2019, 09:02:51 AM »
I asked what the difference between these models are in the PIMOAS thread and why no one seems to talk about DMI, didn't get a response.

I think it's one of those things where only a few people really know the answer, and they've answered it already several times through the years.

But I seem to remember the DMI model being considerered somewhat dubious compared to PIOMAS and CryoSAT. And there is actually a whole discussion about those two, PIOMAS vs CrySat
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Yuha

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Re: 2019 vs 2012
« Reply #57 on: July 16, 2019, 09:17:07 AM »
2012 was not unusually compact in September but pretty close to other years except 2016.
The abnormal year in terms of compactness is 2016, which had very exceptional dispersion in late August and early September.

Neven

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Re: 2019 vs 2012
« Reply #58 on: July 16, 2019, 10:46:00 AM »
I can now do a good comparison for July 15 2012 vs 2019, DMI SST anomalies:
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DrTskoul

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Re: 2019 vs 2012
« Reply #59 on: July 16, 2019, 12:06:49 PM »
I can now do a good comparison for July 15 2012 vs 2019, DMI SST anomalies:

Same magnitude, different distribution.... Pacific is burning and there is no ice export to save the winter ....

Richard Rathbone

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Re: 2019 vs 2012
« Reply #60 on: July 16, 2019, 12:34:45 PM »
DMI's thickness model shows pretty different results to PIOMAS. Where PIOMAS has 2012 and 2019 pretty much tied for volume at this point, 2019 is lagging pretty far behind according to DMI: (click to play)

I asked what the difference between these models are in the PIMOAS thread and why no one seems to talk about DMI, didn't get a response.

DMI uses CICE (and HYCOM for the weather forecast), PIOMAS uses PIOMAS.

DMI is a model to predict extent, PIOMAS is a model to measure total volume. Either can be used for another purpose, but its rather more likely to be bad at it than its primary purpose.

DMI don't publish much on their model so my diagnosis of their weaknesses may miss something important and these weaknesses may not be the critical ones.

CICE is a model developed for GCMs which is portable into weather forecast models rather than climate models, and DMI isn't the only group that has had trouble keeping it numerically stable. (I reckon the stability issue probably arises from calculated salinity being extremely sensitive to measurement error in assimilated temperature.)  DMI publish on their model rather less than they tweak it, so its not possible to be sure just what they are doing at the moment, but last time I found something on it they were assimilating a large chunk of climatology as well as data.

DMI has an issue with melting momentum. They hit volume minimum too early and have a much too steep melting curve during the summer. I think this probably derives from their sea model being a weather forecast model rather than an ice melt model and heat that should be going into a near surface sea layer in June/July and getting back to the melt ice in August/September, is being put directly into melting ice.

If you use the same DMI model to compare 2012 and 2019, its probably not too misleading, but you need to be sure its a reanalysis of 2012 using the 2019 model, because otherwise you'll be looking at the difference between their 2012 model and their 2019 model rather than the ice. (and if its a big difference, you'll can't tell whether its real or whether the model is having one of the years in which it goes haywire)

echoughton

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Re: 2019 vs 2012
« Reply #61 on: July 16, 2019, 12:50:28 PM »
Terrific, Comradez!! As for myself, a complete non-scientist who LOVES this stuff and Neven's forum, this is what I'd like to see more of: Videos with narration showing me exactly what I want to see and learn. Keep it up...perhaps edited down a bit more
 8) 8) 8) 8) 8) 8)

oren

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Re: 2019 vs 2012
« Reply #62 on: July 16, 2019, 12:55:02 PM »
RR, thanks for the detailed response about the DMI volume. I know it's very unreliable but couldn't really explain why...

UCMiami

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Re: 2019 vs 2012
« Reply #63 on: July 16, 2019, 05:18:09 PM »
Neven - find the SST anomaly charts very interesting.
Question on this latest - How much do you think the ocean currents vary in the arctic basin both in flow and temperature year to year (not decade to decade as obviously there are world wide changes due to AGW)?

I ask because I wonder how much these anomaly temp charts reflect large melt season variations - where a arctic sea has continued import of ice or slower melt then average the water temp is going to remain depressed. For example I believe the early temp anomaly in the Beaufort was quite high, but as CAB ice export/dispersion has been very high into the beaufort, that anomaly has decreased significantly compared to 2012. Same is seen in Kara but in that case because of slower melt in that seas. But the anomalies seem to quite quickly expand in the same way as soon as ice disappears. I guess it is a chicken and egg sort of issue - does SST rise follow ice loss or does SST rise drive ice loss?

Neven

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Re: 2019 vs 2012
« Reply #64 on: July 16, 2019, 07:59:43 PM »
The things with anomalies is that when a place that would normally be covered with ice in the base period, melts out, SST anomalies will automatically jump through the roof. In that sense, for those DMI maps, SST rise follows ice loss.

Quote
How much do you think the ocean currents vary in the arctic basin both in flow and temperature year to year (not decade to decade as obviously there are world wide changes due to AGW)?

Ocean currents and the heat they transport into the Arctic, are the big known unknown. A couple of years ago, I wrote an extensive blog post on Ocean Heat Flux, and my guess is nothing has changed much since then.
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Neven

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Re: 2019 vs 2012
« Reply #65 on: July 16, 2019, 08:04:53 PM »
I have a special treat for this thread, and that's the old MODIS composite maps from Environment Canada. Unfortunately, the archive doesn't seem to be complete, but I referred to these maps a lot in 2012, so I managed to retrieve an old image from the ASIB that can be compared to the latest period for this year. Unfortunately it's not in high resolution.

Shapes are different and 2012 seems to have more holes towards Siberia. As said by others in the melting season thread, the ice seemed to look worse in the CAA and western Beaufort in 2012, but it's not easy to make out (click for a larger version):
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ArcticMelt2

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Re: 2019 vs 2012
« Reply #66 on: July 17, 2019, 03:47:53 AM »
https://twitter.com/seaice_de

Quote
#Arctic sea ice is now similar to the year 2012 in terms of total area and extent.
However, the regional pattern is different: the Chuckchi, parts of East Siberian, and Laptev Sea are rapidly melting while there is more ice left in the Barents Sea, Beaufort Sea, and Hudson Bay.


FishOutofWater

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Re: 2019 vs 2012
« Reply #67 on: July 17, 2019, 04:29:26 AM »
SST, ice and weather are coupled and non-linear so you need to look at them together, not as independent things and not just in the Arctic. Warming in the north Pacific combined with southerly winds into Alaska has advected heat into the Arctic and the Bering strait over the last 2 years. The loss of ice in that region appears to working its way north, leading to more ocean heat and the potential for more ice loss. This all may be coupling with shifting storm tracks.

Moreover, El Niños are getting stronger releasing more heat. Some of the warm water from an El Niño works it way up the Pacific coast to the coast of Alaska. We can see that effect now on the SST anomaly maps.

oren

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Re: 2019 vs 2012
« Reply #68 on: July 17, 2019, 04:32:15 AM »
Cross posting NSIDC sea ice age animations from the melting season thread, for posterity's sake.

* What happened in 2012 between end-June and the late minimum. Lots of old ice was eaten up, especially in the Beaufort/Western CAB. FYI from the direction of Siberia was eaten up despite small initial Laptev bite. Note age was advanced by 1 year in the second image.
* What happened in 2016 between end-June and the early minimum. Lots of old ice was eaten up, especially in the Beaufort/Western CAB.  FYI from the direction of Siberia was eaten up despite small initial Laptev bite.
* Comparing end-June between 2012, 2016 and 2019. This year has much less old ice, and a lot of it is at the border of the Atlantic. With a bit of wind or current, this ice could be gone, the Western CAB could be eaten faster than previous years, and the FYI from Siberia to the pole might offer no resistance, with a larger initial Laptev bite.

Click to animate.
« Last Edit: July 17, 2019, 05:12:09 PM by oren »

El Cid

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Re: 2019 vs 2012
« Reply #69 on: July 17, 2019, 09:47:59 AM »
Uni Bremen misses pics from 2012, the first available is 2012 July 23 (shown on second pic). I compared it to 2019 July 16 (first pic). I know there is still one week to go and the comparison is therefore not totally fair but I would say that 2012 looked much-much worse than 2019

Killian

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Re: 2019 vs 2012
« Reply #70 on: July 17, 2019, 02:21:19 PM »
I made these to make my arguments/comments visual as I can be too verbose and am impatient with editing. I wasn't going to post them, but it is being argued elsewhere that the GAC didn't do diddly squat. It certainly did more than did and squat, so far as I can tell.

Hopefully, these help clarify what I think I happened in 2012 and what the real difference was - that week in June and the week of the GAC. Everything else seems to be relatively common, and randomly present or not, for all of the low extent years.

That is, some forcings dominant some years, other forcing dominant others, but 2012 had two anomalous weeks compared to '07 and '16.

Cheers

FrostKing70

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Re: 2019 vs 2012
« Reply #71 on: July 17, 2019, 02:53:35 PM »
Oren,

Looks like the 2019 picture was replaced with a duplicate of the 2012.   Would you please update the post to show 2019?

Juan C. García

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Re: 2019 vs 2012
« Reply #72 on: July 17, 2019, 02:58:20 PM »
Oren,

Looks like the 2019 picture was replaced with a duplicate of the 2012.   Would you please update the post to show 2019?
I thought that too, but if you click them, you will notice that they are different.
Which is the best answer to Sep-2012 ASI lost (compared to 1979-2000)?
50% [NSIDC Extent] or
73% [PIOMAS Volume]

Volume is harder to measure than extent, but 3-dimensional space is real, 2D's hide ~50% thickness gone.
-> IPCC/NSIDC trends [based on extent] underestimate the real speed of ASI lost.

Klondike Kat

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Re: 2019 vs 2012
« Reply #73 on: July 17, 2019, 03:20:01 PM »
Very nice Killian.  You may want to add 2011 for comparison, especially from mid-June through July.

FrostKing70

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Re: 2019 vs 2012
« Reply #74 on: July 17, 2019, 03:22:45 PM »
Yes, you are correct.  I thought they were static, didn't realize they were clickable!

gerontocrat

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Re: 2019 vs 2012
« Reply #75 on: July 17, 2019, 04:16:40 PM »
I thought to have another look at 2012, specifically August and the GAC. So no comparison with 2019.

You can see from the graph that in August extent reduced by far more than area. hence dispersion was greatly reduced.
You can see by the gif that the ice that remained at the end of August was far more compact than at the beginning.

That says to me that the 2012 extent minimum flatters to deceive. Remaining ice, though definitely at a record low, was not completely a freak event.

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gerontocrat

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Re: 2019 vs 2012
« Reply #76 on: July 17, 2019, 04:45:14 PM »
And by the way, when is comes to dispersion, 2019 at the moment is following 2012 pretty closely.
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philopek

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Re: 2019 vs 2012
« Reply #77 on: July 17, 2019, 07:26:46 PM »
Uni Bremen misses pics from 2012, the first available is 2012 July 23 (shown on second pic). I compared it to 2019 July 16 (first pic). I know there is still one week to go and the comparison is therefore not totally fair but I would say that 2012 looked much-much worse than 2019

One week is a lot of time and then please consider the fact that 2019 does have very little dark purple left where 2012 was still very dark, compact and concentrated.

This hints at something we may have difficulties to asses right now because it's a first of it's kind.
Apparently 90% of the remaining ice is not at 100% concentration anymore but lower, in parts even significantly lower.

Adding this fact and the missing 7 days makes me take your assumption with a grain of salt.

Also we have to be careful not to compare apples with pears. Distribution is much different, the area where a surplus of ice, compared to 2012 is located, (Atlantic side) storms are frequent and violent and can total several weeks in total until the end of the melting season and last but not least, the ice in general is thinner and more fractured.

I'm not saying this is correct and that is not, I'm just saying that one can look at the same picture form more than one side, let's wait and see.

« Last Edit: July 17, 2019, 07:32:49 PM by philopek »

Killian

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Re: 2019 vs 2012
« Reply #78 on: July 18, 2019, 12:06:57 AM »
...2012 extent... Remaining ice, though definitely at a record low, was not completely a freak event.

This is a Straw Man argument. I can't recall anyone claiming a freak accident, or even implying it or anything like it.

What I - I won't speak for others, but I get the sense you are responding to my points primarily - have said is the *difference* between '12 and '07/'16 can be explained by the excess -950k loss during two anomalous periods, one of which has not been addressed by anyone. The GAC only accounts for half the difference in final extent. The June massive loss must also be accounted for. All else seems to be mostly explained by general weather variations, all the things we talk about that are dominant one year, not the next and vice-versa. They seem to kind of balance over seasons/years.

'07 lost slowly early then accelerated. '16 lost steadily over a long period of seemingly somewhat higher than average loss, and '12 had two big drops and an extended end of season trough compared to '16's nearly V shape.

That is, it's all just variation, but nothing too specific that is that one big gotcha. 2019 is tracking '11, '16 and '07 pretty well. Then there's '12.

To put this simply, address the average losses the weeks before and after the GAC and the double the average loss the week of the GAC.... or don't. But until someone does, it's all just a bunch of statistics supporting already-held beliefs.

I think two things we can do will help elucidate the 2012 and 2019 seasons differences *and* tell us some interesting things about the ASI in general:

1. What caused the June 6~13, 2012 ASIE 900k+ drop happen? Why do no such drops occur in any other low year, '10, '11, '16?

2. Do we see the same patterns for those two weeks in ASIA? Do any such drops occur in ASIA in any other low year, '10, '11, '16?
« Last Edit: July 18, 2019, 12:48:47 AM by Killian »

Killian

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Re: 2019 vs 2012
« Reply #79 on: July 18, 2019, 12:35:54 AM »
Very nice Killian.  You may want to add 2011 for comparison, especially from mid-June through July.

Thanks. 2011 and 2007 are really very similar. They diverge a bit in June and July, and '11 has a nearly perfect inverted bell shape while '07 is skewed a little to the right, but really track quite closely to each other, so '11 doesn't seem to add any info except to reinforce the abnormality that was 2012.

Cheers

gerontocrat

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Re: 2019 vs 2012
« Reply #80 on: July 18, 2019, 06:52:27 AM »
...2012 extent... Remaining ice, though definitely at a record low, was not completely a freak event.

This is a Straw Man argument. I can't recall anyone claiming a freak accident, or even implying it or anything like it.

I get the sense you are responding to my points primarily -

Er, no, I was not. Nor to anybody else's. I was responding to that I noticed that while 2012 extent minimum was 800,000 km2 (20%) less than 2016 (the 2nd lowest year), area minimum was only 200,000 km2 (5%) less than 2016, i.e. simply following up my own observation.

Looking at the graphs suggested that this happened in August, and during the GAC. So I had a look at what happened in August to extent and area. The answer was that low concentration ice was destroyed and the remaining ice was left as a compact triangle. Hence area decreased far less than extent and dispersion decreased, instead of increasing until minimum as is "normal".

That makes 2012 very unusual, perhaps unique in the satellite record, freakish, if not a freak. I am debating with myself the extent of 2012's freakishness, not with anyone else. Extent loss from now to minimum in 2012 was 28% more than average, far more than any other year. Freaky. Area loss from now was just 8% above average, not freakish at all.

So 2012 is like the Curate's Egg, freakish in parts.
« Last Edit: July 18, 2019, 07:14:17 AM by gerontocrat »
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Killian

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Re: 2019 vs 2012
« Reply #81 on: July 18, 2019, 09:06:22 AM »
...2012 extent... Remaining ice, though definitely at a record low, was not completely a freak event.

This is a Straw Man argument. I can't recall anyone claiming a freak accident, or even implying it or anything like it.

I get the sense you are responding to my points primarily -

Er, no, I was not. Nor to anybody else's.

My poor assumption.

Quote
I was responding to that I noticed that while 2012 extent minimum was 800,000 km2 (20%) less than 2016 (the 2nd lowest year), area minimum was only 200,000 km2 (5%) less than 2016,

JAXA and NSIDC, respectively, it seems. Interesting divergence, but 2012 was when most of us realized the future usefulness of extent data was possibly going to be dubious. As you and Friv are pointing out, a lot of loose ice got munched by the conditions then the GAC, so it makes sense, really.

For me, the interesting question is what is most different between the various years that might hint that, when we see that sort of event it might signal something. As I've said, take out those two weeks of extent losses where 2012 falls nearly 1M km, there is virtually no difference with '16, '11, '07. and they all spend big chunks of the year somewhat in sync.

Put another way, if the June drop never happens, the difference is cut in half or more. Why such a big drop that time of year when no other year has a similar drop?  I think we get the GAC thing: Preconditioned ice with extraordinarily dispersed >15% concentration ice that was exterminated by the cyclone. Friv is right about that, as you noted here also. (Whether that ice would have melted anyway is somewhat (a tiny bit) debatable; maybe it would have compacted, etc...)

But, there have been cyclones before and since.... why so different?

And what the heck happened from June 6th to the 13th?

Quote
Extent loss from now to minimum in 2012 was 28% more than average, far more than any other year. Freaky.

Yeah, but you already know why, as you stated above.

In case you haven't seen it, from now till the the end of the post-GAC drop in 2012, Aug 9th, the differential between 2012 and 2018 is only -103k/day vs. 100k/day. Now *that's* weird. Why similar? '18 had pretty steady, nearly monotonic losses while 2012 had really slowed down and was meandering all over, barely losing any extent (though apparently losing a lot of area) until the GAC.

Over 23 days they vary by only 3k a day... wow. You're right, '12 was weird.

What was going on the 2nd week of June?

oren

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Re: 2019 vs 2012
« Reply #82 on: July 18, 2019, 10:26:57 AM »
And what the heck happened from June 6th to the 13th?

What was going on the 2nd week of June?
2012 had a lot of extra ice in the Bering, and it went poof. Basically meaningless. When you come from high, you have lots to fall.
And the Kara + Hudson + Baffin + Barents started major losses. And some movement in Beaufort. And the Laptev Opened. My initial bet is that a wind pattern caused some of these losses.

In general, I think looking for patterns in extent is problematic. Extent is not real ice. IMHO area would be much better to analyze (and of course volume/thickness even better, if we had accurate data).

bluice

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Re: 2019 vs 2012
« Reply #83 on: July 18, 2019, 12:39:27 PM »
Uni Bremen misses pics from 2012, the first available is 2012 July 23 (shown on second pic). I compared it to 2019 July 16 (first pic). I know there is still one week to go and the comparison is therefore not totally fair but I would say that 2012 looked much-much worse than 2019
I find it interesting that the ”triangle” of ice that remained at Sep 2012 minimum was visible as solid purple ice already in late July. Everything else melted, including the enormous strong purple ridge north of 70N from Beaufort to Chukchi to ESS.

Even though the average ice condition may be better this year than 2012 (which is debatable), the triangle isn’t really solid anymore. There are weaknesses all the way to the pole as well as along the northern shores of Greenland and Ellesmere. Just as preconditioning + weather took everybody by surprise in 2012, I believe that given the right circumstances 2019 might surprise us but in a different way.

I don’t know about extent or area records, but it would be huge to get serious melt and/or polynyas inside the 2012 triangle. That would have far bigger consequences for the future regardless if the record was not made because some areas of, say CAA or Barents, didn’t fully melt this year.

Edit: corrected to 2012 minimum
« Last Edit: July 18, 2019, 03:04:38 PM by bluice »
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Klondike Kat

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Re: 2019 vs 2012
« Reply #84 on: July 18, 2019, 01:54:32 PM »
And what the heck happened from June 6th to the 13th?

What was going on the 2nd week of June?

In general, I think looking for patterns in extent is problematic. Extent is not real ice. IMHO area would be much better to analyze (and of course volume/thickness even better, if we had accurate data).

It would be nice to have accurate data in these areas.  Until then, extent is the most accurate, as problematic as it may be. 


Phil.

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Re: 2019 vs 2012
« Reply #85 on: July 18, 2019, 02:53:28 PM »
Uni Bremen misses pics from 2012, the first available is 2012 July 23 (shown on second pic). I compared it to 2019 July 16 (first pic). I know there is still one week to go and the comparison is therefore not totally fair but I would say that 2012 looked much-much worse than 2019
I find it interesting that the ”triangle” of ice that remained at Sep 2019 minimum was visible as solid purple ice already in late July. Everything else melted, including the enormous strong purple ridge north of 70N from Beaufort to Chukchi to ESS.


I assume you mean 'at Sep 2012 minimum'

bluice

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Re: 2019 vs 2012
« Reply #86 on: July 18, 2019, 03:05:22 PM »

I assume you mean 'at Sep 2012 minimum'
Thanks. Now fixed.
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Glen Koehler

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Re: 2019 vs 2012
« Reply #87 on: July 28, 2019, 03:41:39 AM »
Screenshots from
"Arctic Sea Ice Score Card: Extent, Area, Concentration, Volume, & Thickness - 2019 vs. 2012"
17-page PDF at http://204.197.0.54/MEmodel/NSIDC-PIOMAS2012vs2019-July26.pdf
(but that server is misbehaving 7/27/2019, should be fixed by Monday).





2012vs2019 NSIDC concentration images
« Last Edit: July 28, 2019, 06:52:26 AM by Glen Koehler »

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Re: 2019 vs 2012
« Reply #88 on: July 28, 2019, 03:55:56 AM »
4 more screenshots - Area, Concentration (opposite of Dispersion), Volume, Thickness


 



« Last Edit: July 28, 2019, 07:11:42 AM by Glen Koehler »

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Re: 2019 vs 2012
« Reply #89 on: July 28, 2019, 04:08:00 AM »
Last of 3 posts (and a half dozen updates to fix glitches).
   Yearly average ratios across Extent-Area-Volume-Thickness
...and the winner (so far) is.... (but you already knew)

 
Observations/Speculation: 
   -- 2012 stands alone as the lowest overall with two 1st place and two 2nd place rankings among the four categories.
   -- 2019 is second to lowest, with two 1st, one 2nd, and one 3rd place rankings.  2019 would require a lot of catching up in Extent and Area in the remaining weeks of melt season to take 1st place away from 2012.
   -- 2016 and 2011 are close to each other for 3nd lowest overall ranking, followed by 2017 and 2010 in a virtual tie. 
   -- The sequential rankings of 2010 (#6), 2011 (#4), and 2012 (#1) suggest that the 2012 minimum record was the culmination of a three year sequence of predisposing bad melt years vs. being entirely due to conditions in 2012 alone.
   -- Volume rankings are closely correlated with Extent and Area.  Thickness rankings less so.
   -- Nine of the 10 lowest ranking years have been in the last decade (all except 2007 at #9). 

Definition of terms, caveats, top 20 rankings for each category, and a few other things in the full PDF. Including a still photo from great video of what ice looks like at the edge of the Extent line.
Figure 2.  Ice condition near edge of the Extent limit.  Photo taken at 75N, 150W on October 29, 2016.  Credit: “Waves propagating through Arctic sea ice.”  By IBWOvids. 





Lots of calcs involved and done in a hurry, so errors possible.  Corrections and suggestions appreciated.  Now that the spreadsheet is set up, occasional updates should be pretty easy if folks are interested.

« Last Edit: July 28, 2019, 08:40:08 AM by Glen Koehler »

binntho

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Re: 2019 vs 2012
« Reply #90 on: July 28, 2019, 07:57:03 AM »
Great posts! There is definitely less ice this year than 2012 so far (volume) and it is also thinner even if spread over a smaller extent. But then, area is more or less the same now as 2012.

Exciting to see how this pans out!
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oren

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Re: 2019 vs 2012
« Reply #91 on: July 28, 2019, 08:09:21 AM »
Thank you GK. Impressive.

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Re: 2019 vs 2012
« Reply #92 on: July 28, 2019, 12:28:11 PM »
Very nice, Glen. That's the way to do it.
Il faut comparer, comparer, comparer, et cultiver notre jardin

echoughton

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Re: 2019 vs 2012
« Reply #93 on: July 28, 2019, 12:42:53 PM »
Excellent, Glenn!!
Now are those numbers on the scorecard rankings? Like ...there were 16 other years when the temperature was warmer? 11 other when the volume was less? etc (not sure if I recalled those exact numbers correctly)
Thanks,
Eric

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Re: 2019 vs 2012
« Reply #94 on: July 28, 2019, 02:58:01 PM »
Loved your post Glenn.


Not to discount any of the work you've done, but the combined ratios ranking felt a little unfair.  My reasoning is that you have 2 types of ranking, 2D and 3D.  Perhaps the value rather than the ranking is more relevant.

A simple example of how this might look:

2D ratios = f(Ra, Re)
3D ratios = f(Rv, Rt)

Fitness Ranking --> f(f(Ra, Re), f(Rv,  Rt))

EX: 
   Let f(Ra, Re) = avg(Ra, Re)
   Let f(Rv, Rt) = avg(Rv, Rt)
   Let f(f(Ra, Re), f(Rv,  Rt)) = avg(Ra, Re) * avg(Rv, Rt)

2012: 1.035
2019: 1.185
2016: 1.175*1.19 =  1.398
...   

Just a thought, and thanks for the excellent post.

Edit: the 2nd year listed above was supposed to be 2019, changed from a repeated 2012
« Last Edit: July 28, 2019, 05:18:52 PM by cognitivebias2 »

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Re: 2019 vs 2012
« Reply #95 on: July 28, 2019, 05:18:28 PM »
Now are those numbers on the scorecard rankings?

Hi Eric
  Left column of each table is ordinal rank.  Ratio is each year's minimum relative to the all time minimum for that measure.  The projected 2019 volume is the all time low volume, so its ratio for volume is 1.00 (i.e it matches itself).  The 2012 min volume was 5% larger than that so it has a ratio of 1.05 for volume.

Glen Koehler

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Re: 2019 vs 2012
« Reply #96 on: July 28, 2019, 05:55:32 PM »
Perhaps the value rather than the ranking is more relevant.

2D ratios = f(Ra, Re)
3D ratios = f(Rv, Rt)

Fitness Ranking --> f(f(Ra, Re), f(Rv,  Rt))

EX: 
   Let f(Ra, Re) = avg(Ra, Re)
   Let f(Rv, Rt) = avg(Rv, Rt)
   Let f(f(Ra, Re), f(Rv,  Rt)) = avg(Ra, Re) * avg(Rv, Rt)

2012: 1.035
2019: 1.185
2016: 1.175*1.19 =  1.398

Hi cognitive
   I just took the simple average of the 4 ratios for each year.  Those ratios are based on values not ranks.

   I can see utility in separating out the 2D and 3D combined ratios.  I don't see advantage of multiplying the 2D * 3D vs. to get the overall combined score vs. just taking the average of the 2D and 3D scores.  They each have two components so every measure gets the same weight by using simple average.  Same is true for multiplying.  I don't think multiplying would change the combined rankings and the final value would be less intuitive, i.e. more difficult to relate to the individual component values.  But if there is an advantage to multiplying 2D * 3D I will consider an explanation for what that advantage is and use if it makes sense to me.

   I thought about differential weighting since Volume seems to me to be the best overall indicator for health of the ice.  But every measure has its pros and cons.

    Extent gets blown up and down by the wind, so in some sense isn't a strong indicator.  But it is the only one that is directly lmeasured.

    Area has more info, but in the full document I repeat cautions from NSIDC about Area getting fooled by melt ponds.

    Volume would be the best if we had a direct measure, but we don't.  We have the PIOMAS model which is an estimate subject to errors as are all model estimates.

    Thickness as I understand it is extrapolated from a relatively small number of direct measures so also has estimate error.

     If I sound like I know what I'm talking about, don't be fooled.  This is just how it all looks to me from reading at NSIDC and PIOMAS sites and ASIF of course.

    By the way, full document did not get the final corrections.  Will try to get the finalized PDF version posted tonight.  The tables shown in the post above have all the corrections I could find. 
     I hope to update all the estimates when the July PIOMAS Volume and Thickness data come out in early August.  I wish there was daily update of PIOMAS Vol and Thick, or even weekly. Great to have Wipneus providing mid month Vol.  Did not see his mid month Thickness value, so most recent I had was from way back in June 30.

    One thing that jumps out to me is the notion that 2012 had help from 2010 and 2011 softening up the ice.  Heading into 2012, 2011 and 2010 were #1 and #2 in the all time combined ranking.  Heading into 2020, it looks like 2018 and 2019 will be #7 and #2 (and 2017 at #5).  Less of a setup than 2012 had. 

    But apart from all the number crunching the big picture is obvious and alarming.  The ship is taking on water, the house is on fire.  Pick your favorite metaphor and talk about what you see in Neven's most excellent ASIF with people you interact with.  Political action requires people talking about it as  the necessary first step. Research shows most people never talk about the climate crisis. Politicians tell me they don't hear much about it from their constituents, and that only the squeaky wheel gets attention and action.  As the AIDS activists realized, silence is death.  It is already too late to prevent bad consequences, but we can prevent worse consequences.  We have to try.
 What else ya gonna do? (end of sermon).
« Last Edit: July 28, 2019, 06:14:34 PM by Glen Koehler »

cognitivebias2

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Re: 2019 vs 2012
« Reply #97 on: July 28, 2019, 06:13:48 PM »
Apologies Glen...

I had focused on "
 -- 2012 stands alone as the lowest overall with two 1st place and two 2nd place rankings among the four categories.
   -- 2019 is second to lowest, with two 1st, one 2nd, and one 3rd place rankings.  2019 would require a lot of catching up in Extent and Area in the remaining weeks of melt season to take 1st place away from 2012."

and thought you were using the total of the ranking ordinals rather than the combined ratios to rank years.  I retract my suggestion. 

I should have studied it more before posting. 

UCMiami

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Re: 2019 vs 2012
« Reply #98 on: July 28, 2019, 06:37:12 PM »
Ton of data and nicely organized.
It is important to note that the numbers displayed for 2019 are simply applying the average ending to 2019. The numbers missing are the average lost to date for 2011-2018 rather than the average of the total loss to minimum so a percentage loss from maximum at this date is available.

I would have liked to see that number so as to create a ranking of 2019 and then use that concept to adjust 2019 projection based on how 2019 has fared vs. average remaining melt.

That sounds a little convoluted - more simply put: If 2019 melt season to date has been above average, then why project the 2019 end of season as being just average rather than projecting it to be equally above average? Gerontocrat's post for today identifies extent loss for 2019 as 6.9% greater than average from the 2019 maximum. Would it not be more reasonable to use that same 6.9% greater than average loss for the rest of the year.

It is all projection and as they say in investing past performance is no guarantee of future performance but it would make more sense to base the projections on the current year than on an average of past years wouldn't it? There is some validity to the current year building momentum and to the current condition of ice compared to ice from what ice was on average over the past 8 years.

EDIT : I think this was the issue Neven expressed with the NSIDC 2019 projection from a few weeks back - it was simply concluding 2019 would be average at year end, when it was not average to that date.

philopek

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Re: 2019 vs 2012
« Reply #99 on: July 28, 2019, 07:49:58 PM »
Ton of data and nicely organized.
It is important to note that the numbers displayed for 2019 are simply applying the average ending to 2019. The numbers missing are the average lost to date for 2011-2018 rather than the average of the total loss to minimum so a percentage loss from maximum at this date is available.

I would have liked to see that number so as to create a ranking of 2019 and then use that concept to adjust 2019 projection based on how 2019 has fared vs. average remaining melt.

That sounds a little convoluted - more simply put: If 2019 melt season to date has been above average, then why project the 2019 end of season as being just average rather than projecting it to be equally above average? Gerontocrat's post for today identifies extent loss for 2019 as 6.9% greater than average from the 2019 maximum. Would it not be more reasonable to use that same 6.9% greater than average loss for the rest of the year.

It is all projection and as they say in investing past performance is no guarantee of future performance but it would make more sense to base the projections on the current year than on an average of past years wouldn't it? There is some validity to the current year building momentum and to the current condition of ice compared to ice from what ice was on average over the past 8 years.

EDIT : I think this was the issue Neven expressed with the NSIDC 2019 projection from a few weeks back - it was simply concluding 2019 would be average at year end, when it was not average to that date.

I second this suggestion because it makes sense, perhaps one could even place the numbers
side by side, means on column with the numbers based on average future melt and another column with the 7% higher melt.