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When will the Arctic Extent dip below 1,000,000 Km^2

2018-2019
12 (17.9%)
2020-2025
21 (31.3%)
2026-2030
13 (19.4%)
2031-2040
15 (22.4%)
2041-2060
2 (3%)
2061-2080
0 (0%)
2081-2099
1 (1.5%)
2100-beyond
3 (4.5%)

Total Members Voted: 64

Voting closed: July 27, 2018, 07:46:32 AM

Author Topic: When will the Arctic Go Ice Free?  (Read 130464 times)

philopek

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Re: When will the Arctic Go Ice Free?
« Reply #1250 on: October 12, 2019, 08:34:19 PM »
All good points philopek, but here is an alternate view:   

Those are valid ways to see things. As we all know it's quite complex system about which it's hard or even impossible to tell exactly what happens and certainly even harder to tell exactly when and in which order.

Therefore it's a good thing to think through things from various angles. The only opinions I have serious issues with is "re-glaciation" or a long term rebound while the rest of the planet including it's oceans is getting warmer and gaining momentum doing so.

I for on am very reluctant to discuss whether we lost and/or are currently loosing ice mass, for me it's a fact that we do, while how fast and touching which way-points in the process some can make educated guesses bordering to calculations, most of us can make educated guesses based on observations and information form places like the ASIF and those who promote outrageous provocations for profiling purposes I try to avoid with intermittent success ;)

Thanks for your contribution, very much appreciated, content and attitude wise.

gerontocrat

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Re: When will the Arctic Go Ice Free?
« Reply #1251 on: October 13, 2019, 08:44:10 PM »
By the way, I still think that endless discussions on what charts that use extent & area are best to predict an ice-free Arctic are a waste of time because:-
- CO2 ppm is increasing at an accelerating rate (looks like will at 3 ppm per year this year)
- There is evidence that the Carbon Sinks are not doing so well, (recent post by AbruptSLR re the Southern Ocean & some work I did on carbon sinks c.f. emissions and CO" increases),
- Global Surface ar temps at record levels in an ENSO neutral year plus scary WMO report on recent trends.

BUT - I read the NSIDC talking about a hiatus in extent loss & I think it is WRONG.. Even though they emphasise caveats & the need to look at longer-term trends, it is God's gift to the denier industry.

So here is a 2nd post about it.
____________________________________________

By why stop with your so-called exaggerated years in one direction only?  If your are going to selectively discard data points, why not toss out the high years of 2000 and 2006 also?

Indeed, why not? So I googled to refresh my hazy memory of a Uni course on Mathematical Statistics to fin the standard methodology for identification of outliers. (That course was so long ago for analysis we did it by hand on mechanical machine Babbage would have recognised.)

It got wider - seems to be a big thing in machine learning (AI ?):-

https://machinelearningmastery.com/how-to-use-statistics-to-identify-outliers-in-data/
Machine Learning Mastery
How to Use Statistics to Identify Outliers in Data

Sometimes a dataset can contain extreme values that are outside the range of what is expected and unlike the other data. These are called outliers and often machine learning modeling and model skill in general can be improved by understanding and even removing these outlier values.

- An outlier is an unlikely observation in a dataset and may have one of many causes.
-Standard deviation can be used to identify outliers in Gaussian or Gaussian-like data.
- The interquartile range can be used to identify outliers in data regardless of the distribution.

I followed the recognised  interquartile range method using absolute deviations from the "expected" value from the linear regression used by NSIDC & me in these graphs

For NSIDC Extent it told me to dump an extra year, the very high extent value in 1996.

I did they same analysis or PIOMAS September volume, and it told me to dump 3 years, all very low values, 1981, 1982, and 2012.

The answers re all the same -
- there is barely any change from the linear regression with or without the "outlier years",
- there is no "hiatus" in the steady loss of Arctic Sea Ice extent as implied on the 3rd October  NSIDC analysis (https://nsidc.org/arcticseaicenews/)

Quote
Within the overall decline, it is notable that the most recent 13 years, from 2007 to 2019, have shown very little decline (Figure 3b). Both 2007 and 2012 were extreme low extent years, and variability has been high in this period. However, an earlier 13 year period, 1999 to 2012, shows a rate of decline that is more than double the overall rate in the satellite record. This illustrates the challenge of extracting a quantitative rate of decline in a highly variable system like sea ice, and the benefits of looking at decadal, and not year-to-year variations.
"Para a Causa do Povo a Luta Continua!"
"And that's all I'm going to say about that". Forrest Gump
"Damn, I wanted to see what happened next" (Epitaph)

philopek

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Re: When will the Arctic Go Ice Free?
« Reply #1252 on: October 13, 2019, 11:29:58 PM »
Extremely well explained @gerontocrat

If there is anything where I'm in agreement with the vast majority, which is rare ;) ;) it's that it's a real pleasure and very enlightening to read through your posts.

gandul

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Re: When will the Arctic Go Ice Free?
« Reply #1253 on: October 13, 2019, 11:59:00 PM »
Still you should leave those years there. Well-intentioned mods as yours can give deniers arguments as much as discussing a hiatus. The statistical tendency backed by almost 40 years is clear without needing tweaks.
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gandul

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Re: When will the Arctic Go Ice Free?
« Reply #1254 on: October 14, 2019, 12:03:25 AM »
Also, outliers are more justified when doing a statistical analysis with samples prone to unfrequent but existing large measurement errors, manufacturing defects caused by a distress in the production line, etc.

September average of NSIDC has an intrinsic range of uncertainty that is already very small, so there’s no reason to discard a year against another years, unless you accept discarding the product of nature itself.
No me lo trago

philopek

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Re: When will the Arctic Go Ice Free?
« Reply #1255 on: October 14, 2019, 01:07:44 AM »
Still you should leave those years there. Well-intentioned mods as yours can give deniers arguments as much as discussing a hiatus. The statistical tendency backed by almost 40 years is clear without needing tweaks.

Also a good and valid point but you know what?

While this will take nothing away from your reasoning (not kidding) one of the ways a denier
is distinguished from a realistic and honest thinker is, that it does not matter what we tell them.
because they DENY facts ;) ;)

In other words, your point is valid and Gero's point is valid, and the results are very close and the tendency is obvious (even without tweaks) but since a denier denies ANY valid point, there is no
point in spending a lot of time and energy to find out which of all the valid points we want to
present to a DENIER to DENY ;)

[half kidding but true nevertheless]

Shared Humanity

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Re: When will the Arctic Go Ice Free?
« Reply #1256 on: October 14, 2019, 02:05:34 AM »
Extremely well explained @gerontocrat

If there is anything where I'm in agreement with the vast majority, which is rare ;) ;) it's that it's a real pleasure and very enlightening to read through your posts.

I agree...great post.

Aporia_filia

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Re: When will the Arctic Go Ice Free?
« Reply #1257 on: October 14, 2019, 11:09:19 AM »
^^^Great post Gero. Great person You.

gerontocrat

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Re: When will the Arctic Go Ice Free?
« Reply #1258 on: October 14, 2019, 09:21:59 PM »
One thing is for sure - the linear trends of PIOMAS volume & NSIDC Area can't go on for many more years.

If they did continue, average September thickness in the year 2030 would be 25 centimetres.

See attached
________________________

In my work on deviations from the average, I came up with the following.

The climate / ice system is complex, but all the processes depend on well-known basic physics. It is the interaction that creates the complexity. And physics imposes limits. E.g. If carbon sinks completely failed, i.e. all CO2 emissions stayed in the atmosphere, the current rate of emissions would produce a maximum annual increase in CO2 ppm of around 5 ppm.

So the deviations from the average trend in a year of extent, area and volume are also limited by the current limits to variations in climate and all the other variables affecting ice loss and gain.

So my speculation that belongs to me is that the maximum variations - both more & less - in the last 40 years are a good guide to the absolute minimum and maximum September minimum possible in the next year.

For Extent that suggests the following ranges....
- a 2020 NSIDC September Average Extent minimum of around 4.3 million km2 +20%/-30%,
- a 2020 PIOMAS  September Average Volume  minimum of around 4.0 thousand KM3 +25%/-40% million WHOOPS.
« Last Edit: October 15, 2019, 06:08:07 PM by gerontocrat »
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Glen Koehler

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Re: When will the Arctic Go Ice Free?
« Reply #1259 on: October 14, 2019, 10:59:29 PM »
     
     Extrapolating any trend line too far beyond the data used to define it is prone to error, but less so for a straight line trend, and much less so for extending a straight line trend by a single data point.  The Wipenus linear Sept. minimum volume trend graph
https://forum.arctic-sea-ice.net/index.php/topic,119.msg232085.html#msg232085
shows the 95% confidence interval for the 2020 ASI September minimum volume as 2.0 to 5.5 million km3.  The +/- 1 standard deviation range shows that the 2020 minimum volume has a 68% chance of being between 3.0 and 4.5 million km3.

     A downward trend at a consistent absolute rate of about 333,000 km3 per year becomes an increasing percentage of the total as the total shrinks.  Back in 1980, losing 0.3M km3 represented less than 2% of the total.  A 0.3M loss between 2019 and 2020 would be a greater than 8% year to year decline.   

     As we approach 3M then 2M annual volume minimums (not that far off according the trendline at 2022 and 2026, respectively), continued declines would become more visually dramatic.  And the ratio of % Extent loss to % Volume loss has to increase as the zero point nears.  The advantage of ASI as a visual marker for global warming will likely become more prominent in media coverage.  Neven may have to start wearing sunglasses in public.   8)

     As Sept. average ice thickness nears 1 meter that suggests (to me at least) that the final phase of September ASI losses may accelerate despite countervailing issues like the final ice being at higher latitude with shorter summer solar input, deeper bathymetry, sparser winter ice allowing more heat loss from ocean to atmosphere etc.  The resistance of sea ice to melt is NOT linear.  It decreases faster than thickness.  1 meter thick ice requires significantly less than 50% of the melting power as 2 meter thick ice. 

      Declining ice quality could be another accelerating factor.   The fortress of hard core MYI ice that used to persist along the northern coast of Greenland and the CAA took a serious hit in 2019, (see https://forum.arctic-sea-ice.net/index.php/topic,2839.msg232342.html#msg232342)
And as far as I know, the CAA garlic press ridging did not really occur in 2019.  The qualitative effect that reduced ice quality will have on the melting pattern in 2020 will be morbidly interesting to watch.

     But that is next year.  Right now the developing story of low refreeze and a possible record low April maximum volume is almost as compelling as summer progression to the September minimum.  So thanks to gerontocrat, Juan C. Garcia and others for continuing to post updates.
« Last Edit: October 14, 2019, 11:39:16 PM by Glen Koehler »

binntho

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Re: When will the Arctic Go Ice Free?
« Reply #1260 on: October 15, 2019, 07:35:38 AM »
As much as I agree with the two eminent posters above, the following sentence intrigued me:

1 meter thick ice requires significantly less than 50% of the melting power as 2 meter thick ice. 

If I understand Glen correctly, he is saying that even if "melting power" (however quantified) increases linearly, the resulting melt does not increase linearly (or, perhaps more precisely, will cease to increase linearly in the near future).

Sounds reasonable, and I'd tend to agree. But it's still unsubstantiated - what is "melting power" and is it quantifiable? I would guess that time would be a factor in "melting power", i.e. the number of days of above-freezing temperatures or with clear skies or with strong wave action would all contribute to increased melt - but at a non-linear rate as Glen indicates? I'm not sure.

Surface area / volume rises non-linearly as volume falls, but is that really a factor when it comes to ASI annual melt?

So what other non-linear factors included in "melting power" could cause 1m thick ice to be significantly easier to melt than 2m thick ice?
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crandles

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Re: When will the Arctic Go Ice Free?
« Reply #1261 on: October 15, 2019, 11:54:09 AM »
1 meter thick ice requires significantly less than 50% of the melting power as 2 meter thick ice. 

If I understand Glen correctly, he is saying that even if "melting power" (however quantified) increases linearly, the resulting melt does not increase linearly (or, perhaps more precisely, will cease to increase linearly in the near future).

...

So what other non-linear factors included in "melting power" could cause 1m thick ice to be significantly easier to melt than 2m thick ice?

A major difference will be albedo, I think. So your "melting power" is incoming solar and LW radiation. More of this is absorbed by thin ice (under .5m ish ?) so takes less than half the time. There are other effects:

2. Ability of waves to break up the ice and increase the surface area relative to volume.

3. Warm water (polyna/open water absorb more radiation) being forced by currents under ice affect melting rate of lets say bottom 1cm. That bottom 1cm is higher proportion of 1m ice than 2m ice.
and probably other effects.

binntho

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Re: When will the Arctic Go Ice Free?
« Reply #1262 on: October 15, 2019, 12:41:13 PM »
1 meter thick ice requires significantly less than 50% of the melting power as 2 meter thick ice. 
So what other non-linear factors included in "melting power" could cause 1m thick ice to be significantly easier to melt than 2m thick ice?

A major difference will be albedo, I think. So your "melting power" is incoming solar and LW radiation. More of this is absorbed by thin ice (under .5m ish ?) so takes less than half the time. There are other effects:

2. Ability of waves to break up the ice and increase the surface area relative to volume.

3. Warm water (polyna/open water absorb more radiation) being forced by currents under ice affect melting rate of lets say bottom 1cm. That bottom 1cm is higher proportion of 1m ice than 2m ice.
and probably other effects.
I agree that as the proportion of open ocean increases, the rest of the ice will have a harder time resisting things like high SST's in the ice-free areas, and increased wave action etc. all of which adds up to "melting power"

But none of that is directly tied to ice thickness. Changes in albedo of the ice itself (or rather, how much radiation makes it through the ice and into the top layer of the underlying ocean) will be related to thickness, and I'd expect that this would be a big effect when comparing say 0.5m with 0.25m. But is it significant when comparing 2m with 1m?
because a thing is eloquently expressed it should not be taken to be as necessarily true
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kassy

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Re: When will the Arctic Go Ice Free?
« Reply #1263 on: October 15, 2019, 01:45:49 PM »
Quote
1 meter thick ice requires significantly less than 50% of the melting power as 2 meter thick ice.


Most of this ice will be really young and thus saltier and easier to melt with the same ´melting power´.

Þetta minnismerki er til vitnis um að við vitum hvað er að gerast og hvað þarf að gera. Aðeins þú veist hvort við gerðum eitthvað.

binntho

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Re: When will the Arctic Go Ice Free?
« Reply #1264 on: October 15, 2019, 01:58:10 PM »
Quote
1 meter thick ice requires significantly less than 50% of the melting power as 2 meter thick ice.


Most of this ice will be really young and thus saltier and easier to melt with the same ´melting power´.
I'm not at all sure that this is correct. Younger and saltier ice is going to be easier to melt, and younger ice will tend to be thinner, but that is not enough to explain why 1m thick ice in general would melt significantly faster than 2m ice given the same "melting power".

At the start of the melting season, a large proportion of the ice is 1m or less, and this ice tends to melt out every year anyway. The remaining ice starts out at being thicker than 1m or even thicker than 2m. Given constant "melting power", does the melt-rate incrase as the ice gets thinner in such a way that there will be a "significant" difference between 2m and 1m ice?
because a thing is eloquently expressed it should not be taken to be as necessarily true
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macid

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Re: When will the Arctic Go Ice Free?
« Reply #1265 on: October 15, 2019, 02:23:36 PM »
When ice melts, where does the cold fresh water go? Above or under the ice? Do you think it will sink because it's cold binntho? If it doesn't sink, what effect does it have on heat transfer from the sunken, warmer salty layers?

crandles

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Re: When will the Arctic Go Ice Free?
« Reply #1266 on: October 15, 2019, 02:27:56 PM »

But none of that is directly tied to ice thickness. Changes in albedo of the ice itself (or rather, how much radiation makes it through the ice and into the top layer of the underlying ocean) will be related to thickness, and I'd expect that this would be a big effect when comparing say 0.5m with 0.25m. But is it significant when comparing 2m with 1m?

Does it matter to the proposition that 1m takes less time than half time to melt of 2m?

1m = 0.75m slowly melted + 0.25m quickly melted.
2m = 1.75m slowly melted + 0.25m quickly melted.

means 1m takes less than half the time of 2m and the proposition is true.


>But none of that is directly tied to ice thickness

Are you disagreeing with idea that the thinner the ice the smaller the pieces it breaks into? If so, why?

binntho

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Re: When will the Arctic Go Ice Free?
« Reply #1267 on: October 15, 2019, 02:41:52 PM »

But none of that is directly tied to ice thickness. Changes in albedo of the ice itself (or rather, how much radiation makes it through the ice and into the top layer of the underlying ocean) will be related to thickness, and I'd expect that this would be a big effect when comparing say 0.5m with 0.25m. But is it significant when comparing 2m with 1m?

Does it matter to the proposition that 1m takes less time than half time to melt of 2m?

1m = 0.75m slowly melted + 0.25m quickly melted.
2m = 1.75m slowly melted + 0.25m quickly melted.

means 1m takes less than half the time of 2m and the proposition is true.

But this does not follow at all from what I said! When I talk about 0.25m thick ice I mean 0.25m thick ice, not some random 0.25m segment of 1m or 2m thick ice.

Besides, what ever physical processes do you foresee would cause what you propose? Or are you perhaps saying "the last 25cm are going to melt really very fast, and 25cm is of course only 1/8 of 2m meters while it's 1/4 of one meter, therefore the last 1m is going to melt faster than the first 1m". But if that is what you are trying to say, then you are saying something quite different from what Glen was saying, i.e. that given constant "melting power", 1m thick ice would melt significantly faster than 2m thick ice.

Besides, there is no evidence that the last 25cm would melt faster than the penultimate 25cm given the same "melting power", and even if it sounds reasonable, why should it be true?

It's like saying that the last 1Million km2 of ice will melt a lot quicker than it took going from 2M to 1M, because the last 250.000 km2 will melt really fast because the final 50.000km2 is going to vanish almost instantly etc. etc.

Quote

>But none of that is directly tied to ice thickness

Are you disagreeing with idea that the thinner the ice the smaller the pieces it breaks into? If so, why?
Am I? I didn't know that. I'll be the first to admit that 1m thick ice breaks into smaller pieces than 2m thick ice. But does it have any "significant" effect on the speed of melt? I doubt that very much. If we were talking about 0.5m vs. 0.25m on the other hand, the effect would be considerably bigger and might even be called "significant" if there was any empirical evidence to back that up (and of course some generally agreed-upon definition of "significant", i.e. as in "being meaningful", "having an easily recognizable effect" or other such).
because a thing is eloquently expressed it should not be taken to be as necessarily true
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crandles

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Re: When will the Arctic Go Ice Free?
« Reply #1268 on: October 15, 2019, 04:27:31 PM »
Glen Wrote
"The resistance of sea ice to melt is NOT linear.  It decreases faster than thickness.  1 meter thick ice requires significantly less than 50% of the melting power as 2 meter thick ice. "

to me this seems consistent with considering what needs to happen to fully melt out and with you saying

Quote
"the last 25cm are going to melt really very fast, and 25cm is of course only 1/8 of 2m meters while it's 1/4 of one meter, therefore the last 1m is going to melt faster than the first 1m"

If you want to interpret it as something different like: the rate of melting at 1m is faster than at 2m thick then please explain why you are insisting on such an interpretation. FWIW, I doubt there is a significant difference, if this is the interpretation you are insisting on.

I'll be the first to admit that 1m thick ice breaks into smaller pieces than 2m thick ice. But does it have any "significant" effect on the speed of melt? I doubt that very much.

This does to some extent depend on circumstances: If there is adequate heat in the water (think middle/end of melt season rather than beginning) surrounding the ice then it is about speed of transfer of the heat to the ice. Here, a high ratio of surface area to volume given by small pieces is very helpful to melting the ice quickly.

However a different situation might be earlier in melt season when the heat is not available in the water and air and you have to wait for sufficient heat to be absorbed. This situation is dominated by albedo so the ice being very thin is more likely to be key.

binntho

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Re: When will the Arctic Go Ice Free?
« Reply #1269 on: October 16, 2019, 07:35:36 AM »
Glen Wrote
"The resistance of sea ice to melt is NOT linear.  It decreases faster than thickness.  1 meter thick ice requires significantly less than 50% of the melting power as 2 meter thick ice. "

to me this seems consistent with considering what needs to happen to fully melt out and with you saying

Well I don't see it as being "consistent" with what "needs to happen" to fully melt out. Linear melting would do just as well.

I understand Glen's statement, "the resistence of sea ice to melt is NOT linear. It decreases faster than thickness" to mean that the resistence of ice to melting decreases as the ice becomes thinner.

For a meaningful discussion, let's assume that "melting" means actual melting, i.e. decrease in volume.

If we were to imagine two bodies of water, identical to each other except for the fact that one starts out with thinner ice than the other, would the same climatological effects cause the volume of the thinner ice to decrease faster than the volume of the thicker ice?

As long as the ice is at 100% extent, I don't see how there could be any difference. But as soon as the ice begins to break up, other factors such as wave action and increased albedo, start to kick in and melting should progress faster. The thinner ice can be assumed to start this process sooner than the thicker, resulting in an overall faster volume drop in the thinner ice if melting reaches the point where the ice starts to break up.

So we could well see significant difference between the two bodies of water is one was covered in 10cm ice and the other in 5cm ice. But would there be any significant difference if one was covered in 2m and the other in 1m? I'm not at all sure that the effect of break up would be sufficient to classify as "significant".

If we take the second part of Glen's statement, "1 meter thick ice requires significantly less than 50% of the melting power as 2 meter thick ice. " at face value, I'm not sure that it holds. That word, "significantly" requires a large effect. And a simplistic (or idealised) comparison of 2m and 1m ice does not automatically lead to a "significant" difference in volume loss given the same climatology.

However, if we understand Glen to be talking about averages, then perhaps it starts to make more sense. This year, the average at maximum was ~1.8m and at minimum just under 1m. The "melting power" of this season has removed 0.8m of average thickness.

So if Glen's idea is correct, then if in some future year, average thickness at maximum is 1m then the same "melting power" as in this year would melt it out totally and with a lot to spare. And the effect should presumably be visible sooner, if we started out at 1.5m then a 2019 "melting power" should result in less than 0.5m.

But looking at Neven's Pijamas chart, every year seems to lose about the same average thickness more or less, around the 0.8 mark, so Glen's idea doesn't really hold up - melting power varies signficantly, loss in average thickness does not vary significantly.
because a thing is eloquently expressed it should not be taken to be as necessarily true
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Tor Bejnar

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Re: When will the Arctic Go Ice Free?
« Reply #1270 on: October 16, 2019, 04:31:46 PM »
From above:
Quote
As long as the ice is at 100% extent, I don't see how there could be any difference.
From the internet (NOAA):
Quote
The underside of the ice cover also responds to the surface melt. Directly underneath melt pools the ice is thinner and is absorbing more incoming radiation. This causes an enhanced rate of bottom melt so that the ice bottom develops a topography of depressions to mirror the melt pool distribution on the top side.
Thinner ice (especially under a melt pond) allows for more warming of the water under the ice, so there is more bottom melt under 1m thick ice than under 2m thick ice (with identical surface conditions).
Arctic ice is healthy for children and other living things.

binntho

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Re: When will the Arctic Go Ice Free?
« Reply #1271 on: October 17, 2019, 07:35:06 AM »
From above:
Quote
As long as the ice is at 100% extent, I don't see how there could be any difference.
From the internet (NOAA):
Quote
The underside of the ice cover also responds to the surface melt. Directly underneath melt pools the ice is thinner and is absorbing more incoming radiation. This causes an enhanced rate of bottom melt so that the ice bottom develops a topography of depressions to mirror the melt pool distribution on the top side.
Thinner ice (especially under a melt pond) allows for more warming of the water under the ice, so there is more bottom melt under 1m thick ice than under 2m thick ice (with identical surface conditions).
Yes I wasn't sure about that one. And I still am not sure - if the sunlight enters through the surface, does it make a difference to the final outcome if it reaches the bottom of the floe or not? At an intermediate state it cleary does, since sunlight reaching the underlying water causes visible bottom melt.

But if the light doesn' reach the underlying water, it must instead go into warming up the ice, causing it to melt quicker towards the end. In fact, I'd assume that more of the sun's energy will go towards final melt if it doesn't reach through the ice, since any energy that hits the water can also be dissipated away from the floe.
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oren

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Re: When will the Arctic Go Ice Free?
« Reply #1272 on: October 17, 2019, 11:33:24 AM »
Not entirely true. I think thicker floes have a somewhat higher albedo.

binntho

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Re: When will the Arctic Go Ice Free?
« Reply #1273 on: October 17, 2019, 12:33:11 PM »
Not entirely true. I think thicker floes have a somewhat higher albedo.
It's obvious when looking at thin ice - the darker water below has a much lower albedo, so thinner ice looks darker when looked at from above.

But I'm still after that elusive "significant" effect where 1m ice is a lot easier to melt than 2m ice. And although I'm reluctant to use such strong language, I'm coming to the conclusion that Glen was talking out of his foundational orifice when he made the following claim:

   The resistance of sea ice to melt is NOT linear.  It decreases faster than thickness.  1 meter thick ice requires significantly less than 50% of the melting power as 2 meter thick ice. 

Which is a pity since I quite liked the rest of his post - the two posts,  Gerontocrat's at #1258 and Glen Koehler's at #1259 were extremely good, but when you make big unsubstantiated claims then the rest of what you are saying becomes somewhat tainted.
because a thing is eloquently expressed it should not be taken to be as necessarily true
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wili

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Re: When will the Arctic Go Ice Free?
« Reply #1274 on: October 17, 2019, 02:41:44 PM »
Wouldn't that depend also on the quality of the ice? How salty or slushy it is, for instance?
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Archimid

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Re: When will the Arctic Go Ice Free?
« Reply #1275 on: October 17, 2019, 06:13:20 PM »
I found this nice study on the thickness and transmittance of solar energy on sea ice.
 
Quote
But the present study suggests that the transmittance through bare, melting ice is also significant, and our calculations suggest that as much as 3% of the incident radiation may penetrate 3 m thick ice while 15% may penetrate 1 m thick ice.

Transmission and absorption of solar radiation by Arctic sea ice during the melt season

https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2006JC003977
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Tor Bejnar

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Re: When will the Arctic Go Ice Free?
« Reply #1276 on: October 17, 2019, 09:17:08 PM »
I appreciate your concern, binntho.

I don't know if this helps any, one way or another:
One of the factors affecting ice melt is its temperature profile (or 'average' temperature).  During (let's say a snow-less - to remove one variable) winter, the top of a floe will be something like -40ºC and the bottom ice will be something like -1.8ºC (with the coldest ice at the top surface).  By summer, the top will warm all the way to 0ºC, the bottom will remain  -1.8ºC, and the profile will show the coldest ice somewhere in between.  Even as top melt and bottom melt progress, the coldest ice will be found somewhere in between (until the coldest ice is the -1.8ºC ice at the bottom).

My conjecture: it is likely, but not a requirement, that the coldest mid-ice temperature in 2 m thick ice will be colder than the coldest mid-ice temperature in 1 m thick ice, and therefore the heat required to melt 2 m thick ice will be more than twice that required to melt 1 m thick ice.
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Archimid

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Re: When will the Arctic Go Ice Free?
« Reply #1277 on: October 18, 2019, 11:40:40 AM »
Thin ice melts faster than thick ice.  See this image from the previously linked reference:




Even at 3 m thick ice, 3% of incident radiation on Aug 6th somewhere on the Beaufort Sea makes it to the oceans. At 1 m as much as 15% makes it to the ocean.  The thinner the ice gets from there the more energy the ice lets through.

Then you start taking into account mechanical strength, fractures on the ice and geometry...
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binntho

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Re: When will the Arctic Go Ice Free?
« Reply #1278 on: October 18, 2019, 12:03:43 PM »
Even at 3 m thick ice, 3% of incident radiation on Aug 6th somewhere on the Beaufort Sea makes it to the oceans. At 1 m as much as 15% makes it to the ocean.  The thinner the ice gets from there the more energy the ice lets through.

Then you start taking into account mechanical strength, fractures on the ice and geometry...
I think we can all agree that thin ice melts faster than thick ice under most real world circumstances, particularly due to mechanical effects.

But the original source of my nitpicking was the word "significantly" when comparing 2m ice to 1m ice and I've not seen anybody posting anything supporting that claim. We all seem to have a rather vague feeling that the thinner the ice, the easier it is to get rid off, but on the other hand, nobody seems to be able to quantify this or to give empirical evidence.

As for how much energy makes it through the ice, to me it seems counterintuitive to say that the less energy retained by the ice (i.e. because it is thinner), the faster it will melt. The energy that gets through into the underlying water will contribute to bottom melt, but some if the energy will be dissipated away from the ice.

Glen originally talked about "melting power", so if we imagine that there was some sort of melting power unit (MPU) then his claim is that if it takes 200 MPU to melt a particular area of 2m thick ice, then a same-sized area of 1m thick ice will need "significantly" less than 100 MPU.

And this may be correct, but cannot be explained by difference in Albedo between 1m and 2m thick ice. While the ice is thicker, the energy goes into warming the interior, as the ice gets thinner bottom melt kicks in. Because the 2m thick ice has gone throught the "warming the interor" stage that the 1m thick ice missed out on, the 2m should be ahead on points - but given that thicker ice has more cold interior to warm up, perhaps the net result is nil.

I'm sorry about the endless nit-picking, but Glen's claim was intriguing and bold, and sounded reasonable. But there doesn't seem to be any real evidence to support it.
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oren

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Re: When will the Arctic Go Ice Free?
« Reply #1279 on: October 18, 2019, 12:19:09 PM »
Personally I would not use the word significantly in that context, but bear in mind that 95 or 99 instead of 100 MPU might seem significant to some. It's subjective.
Personally I would also avoid nitpicking this to death and beyond...

binntho

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Re: When will the Arctic Go Ice Free?
« Reply #1280 on: October 18, 2019, 01:50:17 PM »
Personally I would not use the word significantly in that context, but bear in mind that 95 or 99 instead of 100 MPU might seem significant to some. It's subjective.
Personally I would also avoid nitpicking this to death and beyond...
Heard and understood!  :-[
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gerontocrat

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Re: When will the Arctic Go Ice Free?
« Reply #1281 on: November 05, 2019, 03:02:07 PM »
The  Central Arctic Sea - 3.22 million Km2 from  NISIDC Extent & Area Data,  4.48 million Km2 from Wipneus Volume data (different mask files).

In the end the occurrence of a BOE mut be principally about the Central Arctic Sea. So here are a couple of graphs looking at the current state thereof.

Central Arctic Sea Open Water (derived from NSIDC AREA data) looking at open water trends since 1980.

- The average open water for the year until 2006 was 5%. It has increased since 2007 to a more variable circa 10%
- For the three minimum ice months Aug-Oct the open water percentage until 2006 was in the range of under 10% to under 20%. In recent years the range has been from 20 to 30%, in 2019 just over 20%.
- In the early melting season (May-July) the open water percentage has risen from mostly under 5% to approaching 10%, 2019 at just under 10%.
- Winter open water (Feb-April) is unchanged at mostly well under 5%

When looking at area (and extent) the Central Arctic Sea has been only marginally impacted by AGW and consequent sea ice loss. Indeed, a case can be made for a hiatus since 2007 (in contrast with nearly all the other 13 seas in the NSIDC database).

Additional Area Loss for a BOE - Calculation
- A BOE is usually defined as less than 1 million km2 of Arctic Sea Ice Extent (NSIDC data).
- This would be almost entirely in the Central Arctic Sea.
- Sea Ice Concentration at sea ice minimum usually about 70 %,
- So 1 million km2 extent implies sea ice AREA of about 0.7 million km2.
- This would give an open water percentage of nearly 80% (1 -0.7 / 3.22)
- This is about double the maximum open water percent of nearly 40% in 2012, and more than triple the maximum open water percentage in 2019 (about 25%)

Central Arctic Sea Ice VOLUME  (Area from Wipneus data = 4.48 million km2

In complete contrast to Central Arctic Sea Ice AREA, since 1980 the minimum monthly average volume has reduced from about 10 thousand km3 to about 4 thousand km3, i.e. a loss of 60%. (Even winter volume has dropped from around 14 to 10 thousand km3).

BUT, once again, in contrast with most other seas, is there a hiatus from around 2010?
______________________________________________________

So there you are. Lies, damned lies & statistics? Dodgy arithmetic? Or is there a long way to go to a BOE.
__________________________________________________________________________
Quote
Open Water Graph Notes:-
I made graphs for each sea to track the progress of the gradual transformation of the Arctic Seas from Ice Desert to Open Water environment.

Calculation
The data is shown is calculated from the average sea ice area for each period divided by:-
- the total area of the sea if totally enclosed by land or other seas (e.g. Central Arctic, Kara),
Or
- the maximum ice extent recorded since 1980 (e.g. Bering, Baffin, Barents, Greenland).

This gives the percentage of ice coverage. Open water is then 100% minus that percentage
[/quote]
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Klondike Kat

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Re: When will the Arctic Go Ice Free?
« Reply #1282 on: November 05, 2019, 04:22:28 PM »
Very nice Gerontocrat.  The open water graphs look more like a phase change occurred around 2007 that anything else.  The volume shows a smoother change.  Either way, the indcation is that a BOE is not imminent, and may not occur at all.

nanning

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Re: When will the Arctic Go Ice Free?
« Reply #1283 on: November 05, 2019, 06:49:12 PM »
A BOE as specified by gerontocrat will happen because the whole system is changing towards an equable NH. Jetstream behaviour, atlantification, pacification (have you been paying attention KK?).
Maybe just a 'perfect storm' is needed for a BOE. But as 80% open water is very bad, 50% open water is also bad.
The likelyhoods are increasing.
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Re: When will the Arctic Go Ice Free?
« Reply #1284 on: November 05, 2019, 08:11:36 PM »
Very nice Gerontocrat.  The open water graphs look more like a phase change occurred around 2007 that anything else.  The volume shows a smoother change.  Either way, the indcation is that a BOE is not imminent, and may not occur at all.

Bruh......Do you need a pair of glasses? Because I think your not understanding this stuff
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Klondike Kat

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Re: When will the Arctic Go Ice Free?
« Reply #1285 on: November 05, 2019, 08:21:19 PM »
Very nice Gerontocrat.  The open water graphs look more like a phase change occurred around 2007 that anything else.  The volume shows a smoother change.  Either way, the indcation is that a BOE is not imminent, and may not occur at all.

Bruh......Do you need a pair of glasses? Because I think your not understanding this stuff

The percent open water has not increased in over a decade.  Do you see the purple trend line in the volume graph?  Neither graph is popinting towards a BOE anytime soon.  Perhaps you need to borrow my glasses to see them more clearly. 

Wherestheice

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Re: When will the Arctic Go Ice Free?
« Reply #1286 on: November 06, 2019, 12:34:00 AM »
Very nice Gerontocrat.  The open water graphs look more like a phase change occurred around 2007 that anything else.  The volume shows a smoother change.  Either way, the indcation is that a BOE is not imminent, and may not occur at all.

Bruh......Do you need a pair of glasses? Because I think your not understanding this stuff

The percent open water has not increased in over a decade.  Do you see the purple trend line in the volume graph?  Neither graph is popinting towards a BOE anytime soon.  Perhaps you need to borrow my glasses to see them more clearly.

I’m not gonna debate with someone who has poor logic and thinking skills. Don’t @ me
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Wherestheice

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Re: When will the Arctic Go Ice Free?
« Reply #1287 on: November 06, 2019, 12:36:25 AM »
Very nice Gerontocrat.  The open water graphs look more like a phase change occurred around 2007 that anything else.  The volume shows a smoother change.  Either way, the indcation is that a BOE is not imminent, and may not occur at all.

Bruh......Do you need a pair of glasses? Because I think your not understanding this stuff

The percent open water has not increased in over a decade.  Do you see the purple trend line in the volume graph?  Neither graph is popinting towards a BOE anytime soon.  Perhaps you need to borrow my glasses to see them more clearly.

See a trend??
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be cause

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Re: When will the Arctic Go Ice Free?
« Reply #1288 on: November 06, 2019, 01:16:54 AM »
it even looks bad upside down , with or without glasses . N'ice . b.c.
2007 + 5 = 2012 + 4 = 2016 + 3 = 2019 ...

Klondike Kat

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Re: When will the Arctic Go Ice Free?
« Reply #1289 on: November 06, 2019, 01:58:47 AM »
Very nice Gerontocrat.  The open water graphs look more like a phase change occurred around 2007 that anything else.  The volume shows a smoother change.  Either way, the indcation is that a BOE is not imminent, and may not occur at all.

Bruh......Do you need a pair of glasses? Because I think your not understanding this stuff

The percent open water has not increased in over a decade.  Do you see the purple trend line in the volume graph?  Neither graph is popinting towards a BOE anytime soon.  Perhaps you need to borrow my glasses to see them more clearly.

I’m not gonna debate with someone who has poor logic and thinking skills. Don’t @ me

Then I suggest you stick with me.  I see you are unwilling to accept the graphs that gerontocrat posted.  Too bad.  You would find that he is quite adept at these time of things.  Counter his graphs with something that does not describe what he has posted seems rather disingenuous.  Did you even read his post?  May I suggest improving your scientific skills, rather than resorting to insults and blind faith.

Archimid

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Re: When will the Arctic Go Ice Free?
« Reply #1290 on: November 06, 2019, 03:53:33 AM »
I think the hiatus is clear and obvious from Gerontocrat's graphs. Without the hiatus the Arctic would've been about ice-free by now.

The reasons for the hiatus are also relatively clear.

During summer the thick ice is gone so there isn't much easy volume to lose. The remaining volume of ice is in the Central Arctic Sea, protected from maximum irradiance and WAA by the oldest ice in the Arctic.

During winter, thin ice thickens faster than thick ice making the Arctic ice behave more like Antarctic ice.

And that's where we are. At least two heatsinks must be saturated before the march towards the first BOE can continue.

Given human made, CO2 induced global warming. Given Arctic Amplification. Given permafrost and methane activation, local to the Arctic. Given the disturbances in atmospheric currents inducing WAA. Given the lowered Albedo of Arctic Ocean. Given the Greenland crack.

 I don't think it will take long before the hiatus ends.

About the only thing working in our favor is the fall snow increase slightly lowering continental albedo.
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binntho

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Re: When will the Arctic Go Ice Free?
« Reply #1291 on: November 06, 2019, 06:51:16 AM »
Gerontocrat, being one of your biggest admirers I am absolutely sure that you yourself are aware that just because some curve seems to fit the data, e.g. in the following, there is still no reason to think that the curve somehow represents reality. You can make an x^3 curve visually fit data from a few decades, fine, but without some thorough reasoning behind any claim that sea ice behaves according to a third power exponential law, it's just playing around with graphics. Which can be fun but doesn't tell us anything whatsoever about what is going on.



And the never-ending and thoroughly debunked hiatus just doesn't seem to want to go away. Archimid, your reasoning is faulty - the thick ice is not "gone" during summer, and neither research nor logic supports the claim that thick ice is easier to melt than thin ice. Or that the arbitrarily defined "Central Arctic Sea" is somehow different from all the other seas. The entire Arctic freezes every year, and every year a little more of it melts, on average in the long run, and statistical flukes and annual variance doesn't change those facts.




And seeing as how the underlying cause (i.e. global warming) has been as close to linear as makes no difference tuntil very recently, melt should also be as close to linear as makes no difference.

But seeing as how global warming does seem to be taking a kick upstairs these last 5 years or so, I'd expect melt to take off as well.



So perhaps the x^2 trendline in this image is showing the way?



because a thing is eloquently expressed it should not be taken to be as necessarily true
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binntho

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Re: When will the Arctic Go Ice Free?
« Reply #1292 on: November 06, 2019, 06:51:43 AM »
A BOE as specified by gerontocrat will happen because the whole system is changing towards an equable NH.
No it isn't.
because a thing is eloquently expressed it should not be taken to be as necessarily true
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El Cid

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Re: When will the Arctic Go Ice Free?
« Reply #1293 on: November 06, 2019, 07:39:08 AM »
A BOE as specified by gerontocrat will happen because the whole system is changing towards an equable NH.
No it isn't.
For all, raging about an equable climate, I suggest reading this:

https://www.seas.harvard.edu/climate/eli/research/equable/climate.html

and all the other pages there. They have a nice collection which explains the science behind equable climate.

Shorthand: Nobody exactly knows why it happened, but there are competing theories, some more believable, some less. But you need much more warming than currently to get there

Klondike Kat

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Re: When will the Arctic Go Ice Free?
« Reply #1294 on: November 06, 2019, 02:43:26 PM »
Binntho,
Careful.  You are making the mistake that others have; namely using data for the entire Arctic to describe the CAB.  Recent climatic changes have been sufficient to melt a significant portion of the ice in the peripheral seas, but the central Arctic is a different story.  We may get there eventually, but to quote Archimid, "At least two heatsinks must be saturated before the march towards the first BOE can continue."

gerontocrat

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Re: When will the Arctic Go Ice Free?
« Reply #1295 on: November 06, 2019, 03:07:04 PM »
Gerontocrat, being one of your biggest admirers I am absolutely sure that you yourself are aware that just because some curve seems to fit the data, e.g. in the following, there is still no reason to think that the curve somehow represents reality. You can make an x^3 curve visually fit data from a few decades, fine, but without some thorough reasoning behind any claim that sea ice behaves according to a third power exponential law, it's just playing around with graphics. Which can be fun but doesn't tell us anything whatsoever about what is going on.

I put two different trend lines to show exactly what you are saying. the x3 trend shows the volume loss stopped, the x2 trend shows the volume continuing to decrease. I'm for x2 - annual increases in ppm getting higher, little sign of any real decrease in CO2 emissions, my data saying the carbon sinks are soaking up less than half of CO2 emissions while the literature says more than half.

I spent some time a month or two ago on this thread to show that there is no hiatus when it comes to sea ice loss in the whole Arctic. (see my graph used in the post by "Wherestheice" on Nov 5). I looked at the Central Arctic Sea to see if there is a contrast between the Central Arctic Sea and the 13 other seas in the NSIDC / PIOMAS data.

But to me the data does suggest that there is a contrast - for example one sees that seas such as the Chukchi, the ESS, the Laptev and the Kara have longer open water periods (i.e. extending the time when sea ice extent, area and volume is very low), while the Bering is now basically an open water sea. But the Central Arctic Sea is still basically an icy desert where sea ice area and extent are as yet only marginally impacted by AGW+polar amplification.

Volume is also showing that contrast since 2007 and, I think, will be the key. When thickness declines enough, area and extent will collapse. (That's my speculation that belongs to me). Or will it be earlier open water in the surrounding seas causing gradual nibbling away of the edges of the Central Arctic Sea ice?

When? NOT A CLUE - a pure guess is within the next 10 years.
_________________________________________________________
ps: I am gratified to see some of my graphs sprayed around this thread.  I sometimes wonder what happens to the stuff I throw at the forum.
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Glen Koehler

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Re: When will the Arctic Go Ice Free?
« Reply #1296 on: November 07, 2019, 12:50:22 AM »
Apologies for taking so long to reply... I'll spare you my usual excuses, though I don't doubt they would impress you with their earnest sincerity and momentous import of the ways I manage to waste time ...

   Here is the reasoning why I proposed that the last 1 meter of ASI from 1m average thickness would melt to 0m faster than from 2m to 1m average thickness:
    -- As we lose the older thicker MYI, the remaining ice has higher percentage of younger, and thus saltier and easier to melt FYI.  Everybody seems to agree on that.

e.g. As interstitial noted at
https://forum.arctic-sea-ice.net/index.php/topic,2709.msg201895.html#msg201895
       Thinner ice, presumably with higher portion of First year Ice...
"has pockets with high salt concentrations in it. Some of the pockets even most may not of frozen solid.
   ...When the temperature climbs above -21C the pockets of high salt concentration melt first. The temperature is still too low to melt the pure ice.
   ... This is how multiyear ice is formed each freeze and thaw cycle of salty water can more and more salts out until it is pure ice with no salts. That makes the multiyear ice fresher and more melt resistant."

   -- But here is the main reason - the Thorndike (1975?) chart showing the differential rate at which ice of different thicknesses increases thickness, that Chris Reynolds posted to explain the Slow Transition hypothesis.  To me it says that unless there is some hysteresis effect, then that curve in reverse shows that thin ice also melts MUCH faster for the same amount of heat input.  For a given amount of heating energy, e.g. melting degree days in summer, more ice is lost per unit of energy in summer by thin vs. thick ice, just as more ice is gained by thinner ice for the same amount of freezing degree days during the winter.

      Here is the Thorndike chart

(And you know its good because it is Neven's account icon!)

     Here is my reversed version, with zoom into the last 2 meters.


     Seems to me that the Thorndike chart, when reversed, shows the amount of ice lost for the same amount of heat added to ice of different thicknesses.  Just as the original chart shows the amount of ice gained for the same amount of heat lost from ice of different thicknesses. 

     Thus, I am using Chris Reynolds' Slow Transition evidence to reach an opposite conclusion.

     This is a simple case of Teslacle's Deviant ("What comes in, must go out") to Fudd's First Law of Opposition ("If you push something hard enough, it will fall over") -- for you Firesign Theatre fans.  Seriously though, as a thermodynamic equation, what works in one direction should work in the reverse unless there is some hysteric effect at work.  (e.g. Teslacle was right!  This could be Vulvaire's Correlate to Teslacle - "What went out, comes back in.")

     Another chart adapted from an ASIF post by Jim Hunt
https://forum.arctic-sea-ice.net/index.php/topic,2709.msg201631.html#msg201631
shows the same phenomenon. I didn't reverse this one, but you can do that in your head.

   
     The only argument against a quicker final meter melt notion is that the because the CAB is at higher latitude, the melting process will stall as the Arctic ice melt reaches the high latitude end game.  And I might buy that idea if humanity was intelligent enough to stop pumping greenhouse gases into the atmosphere at an increasing rate, but not seeing evidence that we will, one can only suppose that warming will continue, and in fact that the rate of warming is increasing.

     I admit that gerontocrat's open water chart (up thread at https://forum.arctic-sea-ice.net/index.php/topic,2348.msg235525.html#msg235525) requires a huge rate increase in CAB September open water to have a BOE anytime soon.

      But the cumulative evidence argues that that is indeed what will happen.  While gerontocrat's CAB volume trend chart shows it reaches zero a few years later (ca. 2040?) than the whole-Arctic Wipneus volume chart (2032), it is not that much later.  That suggests that the CAB does not have enough extra resistance against melt to combat the inexorable warming and Arctic amplification underway. 

   As Tor Bejnar noted at
https://forum.arctic-sea-ice.net/index.php/topic,933.msg113144.html#msg113144
"I have also long considered the 'quick' loss of summer ice in the non-CAB regions over the past 30 years (e.g., the Beaufort going, in August, from 2/5th coverage to none between 2013 and 2016) not to be predictive of how fast CAB ice will be lost.  I think this discussion of bathymetry adds some geophysical creds to Chris's theses.  This doesn't mean, however, that I'm 'now' convinced Chris is right.  I think other issues like CO2-equivalent, mobility and storminess (emphasis added GK) may well 'over' compensate for the bathymetry-related suppression of warm water currents remaining near the ocean surface."

     As Bruce noted at
https://forum.arctic-sea-ice.net/index.php/topic,778.msg32178.html#msg32178
"Chris, I don't see any reason for the rate of summer melt increase to flatline, slow down, or even be linear. As the ice thins, the surface/volume ratio increases, which should increase the rate of melt. The thick MYI held off major assaults in 2017 and 2012, but that ice is nearly gone. What we have now is this "mesh ice" that spreads out as the edges melt (which, though it is a negative feedback (because it keeps more of the ocean covered with ice), is a short-lived one). That spreading increases the surface (both top and bottom) that can melt."

    In a second instance of using Chris Reynolds' evidence to reach an opposite conclusion, I will reinterpret a chart he posted at at https://forum.arctic-sea-ice.net/index.php/topic,933.0.html


   Read his post to see how he uses that to argue for the slow transition.  To me it shows that  September ASI volume hits zero ca. 2027, even earlier than the Wipneus chart.

   As for the hiatus, I think we've beat that to death.  I'll just repeat that 10 yearly data points is simply not long enough to make statistically valid conclusions for data with high interannual variability.  I will go out on a limb and bet that the 2012 minimum volume record has a 50% chance of being replaced in 2020, likely won't last beyond September 2021, and almost certainly won't last  beyond Sept. 2022. 

    That said by the guy who expected the October slow refreeze to continue based on GFS forecast showing continued high Arctic temperature anomalies over the last 10 days, when just the opposite happened.  I guess I was confusing the tail and the dog - my new guess is that the air temp. anomalies were high because the water transitioning to ice was giving off heat to warm the air above it. 


« Last Edit: November 07, 2019, 04:54:36 PM by Glen Koehler »

GoSouthYoungins

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Re: When will the Arctic Go Ice Free?
« Reply #1297 on: November 07, 2019, 04:30:01 AM »
Glen, in general I think you analysis is good. BUT, the ice to the east of land masses is tough to melt. And the ice north of 85 degrees and not near the atlantic or pacific is hard to melt.

The freezing season near the pole brings a darkness and cold that is hard to comprehend.

We are in the process of "flipping a switch" where the arctic gets much warmer...but certain (large) areas will continue to be very icy cold for much longer. Not THAT much though.
big time oops

Klondike Kat

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Re: When will the Arctic Go Ice Free?
« Reply #1298 on: November 07, 2019, 04:43:06 AM »
I agree that Glen has presented an excellent analysis.  It may come down to whether the high latitude endgame or thin ice scenario wins out.  My only qualm about his post is his claim that 10 yearly data points is not long enough to make statistically valid conclusions during the hiatus, yet that is exactly what he does for the previous 10 years when the ice is declining.  Yes, the volume reached zero in 2040, if the second order curve is used.  However, the third order curve (which has a better data fit), pushes that date much further into the future. 

As GSY stated, the darkness and cold is hard to comprehend.  It appears that same statement applies to the data.

oren

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Re: When will the Arctic Go Ice Free?
« Reply #1299 on: November 07, 2019, 10:52:28 AM »
Glen, at the root of your well written post is the reversal of the Thorndike chart, which I think is wrong. The physical behaviors of melting and freezing in the Arctic are different due to the effect of the buffer of the water below the ice. Also a lot of the melting is due to direct insolation while the temperature stays near zero. So while I would tend to think thinner ice melts more easily than thicker ice for a given "melting power", this heuristic chart reversal cannot be used as the reasoning for that.