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

Author Topic: When will the Arctic Go Ice Free?  (Read 139762 times)

Glen Koehler

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Re: When will the Arctic Go Ice Free?
« Reply #1350 on: November 12, 2019, 04:50:20 PM »
Edited quote
Since the third term is a calculated average (and not a finite measure as the other two) then flipping them around makes no sense.

At least we have identified where we disagree,
I submit that mathematically all are true.
E*T=V
E = V/T
T = V/E

It does not matter to their mathematical relationship which one you solve for, the relation stays the same.  In your examples you solve for T based on set values for E and V, and you get a T that is greater than E.  But that is not an inherent requirement.  It is simply an artifact of the values you set for E and V.  You could set E and V to different values and find that the resulting T is less than E.

For example:  As you found
 If E = 0.99 and V = 0.98
then T = V/E = 0.9898
T decline (=1 - 0.9898) is greater than E (1-0.99).

 But
 If E = 0.9898 and V = 0.98
then T = V/E = 0.99
T decline (=1 - 0.99) is greater less than E (1-0.9898)

It does not matter which is directly measured and which is inferred.  Mathematically they are all equally real.  (And BTW, Thickness IS measured.  Volume is calculated from Extent and Thickness).
But if you want to define E and V and then calculate T, that is fine.  Doing so does not require T to be smaller or larger than E.  All that matters is the relative sizes of the E and V values you choose.  Specifically, if E - V is larger or smaller than 1 - E 

For example, if E = 0.9 and V = 0.85,
T = V/E
T = 0.94
T is larger than E
 E - V = 0.05
1 - E = 0.1
E-V is less than 1-E, so T is greater than E

 if E = 0.95 and V = 0.85,
T = V/E
T = 0.89
T is less than E
E - V = 0.10
1 - E = 0.05
E-V is larger than 1-E, so T is less than E


RE:  Oren.  Close but no cigar.  You are using E + T = V. 
It is  E * T =V.
Multiplication vs. Addition.

Addendum to the end game scenario.  Extent losses are largely due to the loss of thin ice at the edge of the pack.
As the pack shrinks, that edge area becomes an increasing proportion of the total pack area.  Circumference to area ratio gets larger.
 
(This is analogous to the surface to volume ratio that lets insects do things we can't, and also why insects have to be small to do what they do, but I digress)

So, as the percentage of the total ice pack subject to edge area losses gets larger, the percentage rate of Extent losses will increase. 

***Not sure about this next statement.  Math fatigue setting in.***
The straight line trend for Extent losses will begin to curve downward unless it is counteracted by a decline in rate of thickness loss around that edge, which does not seem likely.

*** Then again, the absolute amount edge = Extent loss would not increase, and in fact with smaller absolute edge area, absolute Extent losses would decrease.  But the amount of extent loss would be higher ratio relative to the amount of previous year Extent.  So it may just come down to whether you report Extent losses as absolute number of km2 or % of previous year.  Math fatigue now math exhaustion.  This is becoming a "how many angels fit on the head of a pin discussion".  Who cares.  It does not matter. 

    What matters is that the ASI is nosediving.  Because of albedo and other effects, how the Extent trend will evolve is of interest.  Thanks to Notz and Stroeve and their colleagues, we have insight on how the ASI situation will dramatically evolve over the next 10-30 years.  It is a scary, ominous story.  Maybe if the immediacy of ASI collapse is better understood it will help us make difficult decisions to reduce the damage we are doing to ourselves.



« Last Edit: November 13, 2019, 12:45:55 AM by Glen Koehler »

oren

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Re: When will the Arctic Go Ice Free?
« Reply #1351 on: November 13, 2019, 01:44:00 PM »
RE:  Oren.  Close but no cigar.  You are using E + T = V. 
It is  E * T =V.
Multiplication vs. Addition.
Of course. I am using (1-x)*(1-y)=1-(x+y), the first approximation, which works surprisingly well for small numbers.
Note my numbers are "E decline" (1-E) and "T decline" (1-T), per your definitions.
V=E*T=(1-Ed)*(1-Td)=~1-(Ed+Td)
Vd=1-V=~Ed+Td
1.3%=~1%+0.3% in my example.

(Sorry, I am bored... but who wants a cigar anyway?? Yikes!)

Glen Koehler

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Re: When will the Arctic Go Ice Free?
« Reply #1352 on: November 14, 2019, 03:22:00 AM »
This situation is getting worse fast

From today
The Arctic's Most Stable Sea Ice Is Vanishing Alarmingly Fast
By Mindy Weisberger
https://www.livescience.com/arctic-ice-refuge-vanishing.html
https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2019GL083722

From August 2018.
'Archived' heat has reached deep into the Arctic interior, researchers say
By Yale University.
https://phys.org/news/2018-08-archived-deep-arctic-interior.html
https://advances.sciencemag.org/content/advances/4/8/eaat6773.full.pdf
Thanks to ArcticMelt2 for bringing attention to this one with post at
https://forum.arctic-sea-ice.net/index.php/topic,2888.msg236503.html#msg236503

"The upper ocean in the Canadian Basin has seen a two-fold increase in heat content over the past 30 years, the researchers said. They traced the source to waters hundreds of miles to the south, where reduced sea ice has left the surface ocean more exposed to summer solar warming. In turn, Arctic winds are driving the warmer water north, but below the surface waters.

"This means the effects of sea-ice loss are not limited to the ice-free regions themselves, but also lead to increased heat accumulation in the interior of the Arctic Ocean that can have climate effects well beyond the summer season," Timmermans said. "Presently this heat is trapped below the surface layer. Should it be mixed up to the surface, there is enough heat to entirely melt the sea-ice pack that covers this region for most of the year." "

The region discussed in the second article abuts the area described in the first article, i.e. the wedge of thickest overwintering that runs from the north coast of Greenland along the northern edge of the CAA. Not a good place to store a reservoir of warm water.

« Last Edit: November 14, 2019, 05:32:14 AM by Glen Koehler »

Richard Rathbone

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Re: When will the Arctic Go Ice Free?
« Reply #1353 on: November 14, 2019, 05:53:48 PM »

"This means the effects of sea-ice loss are not limited to the ice-free regions themselves, but also lead to increased heat accumulation in the interior of the Arctic Ocean that can have climate effects well beyond the summer season," Timmermans said. "Presently this heat is trapped below the surface layer. Should it be mixed up to the surface, there is enough heat to entirely melt the sea-ice pack that covers this region for most of the year." "


What they don't tell you is

i) the most likely time of year for a mixing event to happen is when there is no ice and the heat would just get lost to space. (like happens with most of the excess heat that gets into the ocean during the summer already, it comes back out in the autumn)

ii) even if Capt. Nemo came along with his magic submarine and mixed it up during mid-winter, it would promptly freeze back over again. Ice keeps the underlying water warm during winter, take the ice away and it cools fast. There would be a year of thinner than normal ice, faster than normal summer melt out, and the impact would have dissipated.

iii) and in both of these cases its a one-off, that 30 years of stored heat has had its brief impact and disappeared to space and its going to take another few decades before its been stored back up again.

If you see a phrase like "two-fold increase in heat content" alarm bells should go off. Its a sign that results have been manipulated to make them seem more impressive than they actually are. Heat content multiples are meaningless because they can be set at whatever value the researcher likes by the choice of baseline. Choose a different baseline and the same data will give a 2% increase or a 10-fold decrease instead. Heat content increase by 0.1 J/kg is meaningful, but doubling isn't.

dnem

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Re: When will the Arctic Go Ice Free?
« Reply #1354 on: November 14, 2019, 06:36:47 PM »

"This means the effects of sea-ice loss are not limited to the ice-free regions themselves, but also lead to increased heat accumulation in the interior of the Arctic Ocean that can have climate effects well beyond the summer season," Timmermans said. "Presently this heat is trapped below the surface layer. Should it be mixed up to the surface, there is enough heat to entirely melt the sea-ice pack that covers this region for most of the year." "


What they don't tell you is

i) the most likely time of year for a mixing event to happen is when there is no ice and the heat would just get lost to space. (like happens with most of the excess heat that gets into the ocean during the summer already, it comes back out in the autumn)

Do we know this is correct? Let's say that after a (hypothetical) very low extent at the end of a strong melt season there is a big storm that strongly mixes the deep heat into the surface layers.  Will all this heat be "lost to space" or might it warm the atmosphere over the next freeze season, resulting in a warm, cloudy winter that retards the freeze enough to tip the system?

Glen Koehler

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Re: When will the Arctic Go Ice Free?
« Reply #1355 on: November 14, 2019, 11:32:42 PM »
      Neven has said he does not like long wordy posts, which this certainly is.  If it violates some ASIF code I am unaware of and it gets snipped, no offense taken.  I wanted to make these excerpts for my own use anyway.

     This post consists of some of the best sentences from the paper cited below.  The whole paper is well worth reading and is written in understandable language.  They do dig into the details of various sensors in the methods section, but you can gloss over that stuff. 

     By the way, if you are not used to reading science journal articles, here is a little secret.  Almost nobody completely understands every sentence.  Sometimes not even the authors.  You learn how to read to get what you can get and when it gets obscure you just move on.  Always good to start with the abstract, then it is fair game to skip to the conclusions, and look at some graphs along the way to decide if you to read the whole thing.  Sorry if this comes across as patronizing.  I just figure a lot of people are not used to professional "science culture", I know I certainly had no clue about it through 7 years of on-again off-again undergrad.  Once you realize it is just people, it becomes less intimidating and more fun.

     As for protocol and rightful use of such extensive quoting, the source article has a license statement that looks favorable. "Original content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence.  Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI."

     These topics arise repeatedly in the forum and Stroeve and Notz do a nice job of laying it on the table.  My guess is that as the paper is over a year old and as they are passengers on this planet too, Stroeve and Notz would approve of using the forum to spread their findings.

Source for all of the excepts below:
Changing state of Arctic sea ice across all seasons
Julienne Stroeve and  Dirk Notz
2018 Environ. Res. Lett.13 103001
https://iopscience.iop.org/article/10.1088/1748-9326/aade56

        Placement of "-------" indicates larger than usual amount of text was skipped prior to following quote.  All right, here we go.
--------------------

    “There are two ways in which the climate system can reduce the amount of sea ice within the Arctic Ocean:  first by local melting within the Arctic Ocean, and second by export of sea ice through outward sea ice drift. As outlined in the following sections, a number of studies have found the local melting of sea ice to be by far the main contributor to the observed loss, and we hence need to identify the main driver for increased sea ice melting if we are to identify the main driver for the substantial sea ice loss in recent decades.”
--------------

"4.2. Stability of the ice cover
    In addition to changes in the external forcing and internal variability, a self-amplification of the ongoing ice-loss could in principle have contributed to the rapid ice loss in recent years. Such self-amplification is usually discussed in the context of so-called tipping points or nonlinear threshold, which are often defined as processes in the climate system that show substantial hysteresis in response to changed forcing.

     The best known example for such possible hysteresis behavior is related to the ice-albedo feedback  mechanism: a reduced ice cover in a given summer will cause increased absorption of solar radiation by the ocean, contributing to further reductions in the ice cover.  Such positive feedback loop can cause the irreversible loss of Arctic sea ice in idealized studies based for example on energy-balance models (see review by North 1984), and have hence been suggested to possibly  be relevant also for the real world.

     However, an analysis of the existing observational record and a substantial number of respective modeling studies with complex ESMs all agree that such a ‘tipping point’ does not exist for the loss of Arctic summer sea ice. For example, Notz and Marotzke (2012) found a negative auto-correlation of the year-to-year changes in observed September SIE. Hence, whenever SIE was substantially reduced in a given summer, the next summer usually showed some recovery of the ice cover. This was further supported by Serreze and Stroeve (2015). Such behavior suggests that the sea-ice  cover is at least currently in a stable region of the phase space, as otherwise one would then expect that any year with a really low ice coverage should be followed by a year with an even lower ice coverage, driven by the ice-albedo feedback mechanism. As shown by Tietsche et al (2011), the contrasting behavior of the real ice cover can be explained by compensating negative feedbacks that stabilize the ice cover despite the amplifying ice-albedo feedback. The most important of these stabilizing feedbacks relates to the fact that during winter the ocean very effectively releases heat from those areas that became ice free during summer, thus over-compensating for any extreme ice loss in a preceding summer. Ice that is formed later in the season also carries a thinner snow cover and can hence grow more effectively during winter (e.g., Notz 2009).  Stroeve et al (2018) suggest, however, that this stabilizing feedback mechanism is becoming weaker and weaker as Arctic winters become warmer and warmer.  Increased winter cloud cover after summer sea ice loss as found by Liu et al 2012 also weakens the stabilizing
feedback, as it reduces the loss of heat from the ocean surface."

« Last Edit: November 15, 2019, 01:12:47 PM by Glen Koehler »

Glen Koehler

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Re: When will the Arctic Go Ice Free?
« Reply #1356 on: November 14, 2019, 11:58:16 PM »
One more time, same source article:
Changing state of Arctic sea ice across all seasons
Julienne Stroeve and  Dirk Notz
2018 Environ. Res. Lett.13 103001
https://iopscience.iop.org/article/10.1088/1748-9326/aade56

New topics.  As before, I think this use is allowed under source article CC license. 
"Original content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence.  Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI."

Here we go:
-------------------

"A study by Burgard and Notz (2017) has found that CMIP5 models disagree on whether the anomalous heating of the Arctic Ocean, and thus the loss of Arctic sea ice, primarily occurs through changes in vertical heat exchanges with the atmosphere (as is the case in 11 CMIP5 models), primarily through changes in meridional ocean heat flux (as is the case in 11 other CMIP5 models) or through a combination of both (as is the case in 4 CMIP5 models). This suggests that our understanding of how precisely the heat for the observed sea ice melt is provided to the sea ice is still surprisingly limited."

---------
~ (words are quotes but citations removed for clarity) **Focusing first on the atmosphere, changes in the sea-ice cover can occur through dynamical changes that drive ice export, thermodynamical influences , or a combination of both.**
---------

"Williams et al (2016) found winter preconditioning continues to play a large role in September sea ice  variability. In particular, winter ice export out of Fram Strait is strongly correlated to the anomaly of the following September SIE, allowing for the possibility of forecasting sea ice conditions in September several months in advance."

-------
" Ding et al (2017) provides the most recent characterization of the role of atmospheric variability on the observed summer sea ice, showing that trends in atmospheric circulation patterns in summer (i.e. a more anticyclonic circulation pattern) have increased the downwelling longwave radiation towards the surface as a result of a warmer and moister atmosphere. They further suggest that these circulation changes dominate summer ice variability rather than feedbacks from a changing sea ice cover."

--------
"The Atlantification of the eastern Eurasian Basin may therefore provide an additional factor
behind sea ice reductions in that region, perhaps on the same order of magnitude as atmospheric thermodynamic forcing."

(skipping Pacification, they discuss it, but no succinct summary quotes.)

-------
    "The large Eurasian and North American rivers input warm freshwater (on average 15 °C) with a distinct seasonal  cycle along the shallow shelf seas (e.g. Carmack et al 2016). Peak discharge occurs in June and this  water is immediately available to melt ice, helping to break up the fast ice. River discharge also adds a large amount of chromophoric dissolved organic matter, which absorbs sunlight at short wavelengths (Griffin et al 2018), further warming the surface layers of the ocean and increasing ice melt.  On the other hand, increased ice melt and freshwater input increases summer stratification, allowing for more heat to be trapped in the upper ocean, which in turn delays ice formation in autumn."

--------------
"While it is understood that changes happening within the Arctic do not stay there, it is less certain whether current Arctic warming is already driving an increase in storm frequency and extreme weather events across the mid-latitudes, including extreme heat and rainfall events, and more severe winters."

-------
"Conclusions
Through novel analysis and a review of recent studies, we have examined the ongoing ice loss of Arctic sea ice across all seasons. We have established the following key results:

1. With respect to the 1981–2010 reference period, relative ice loss has been more significant during autumn, winter and spring the last two years than during summer (figure 1).

2. The ice cover has not only retreated in its areal extent, it has also become much younger (figure 4) and thinner (figure 5) in recent years. In April 2018, only about 2% of the winter sea-ice cover consisted of sea ice older than 5 years, compared to almost 30% of the April sea-ice cover in 1984.

3. The thinning of the ice cover and the overall warming of the Arctic have increased the likelihood
of rapid ice-loss events during summer in recent years (figure 6). On the other hand, the larger expanses of open water have similarly increased the likelihood of rapid ice-growth events during autumn.

4. The increasing relative loss of winter sea ice is in part related to the fact that more and more regions of the Arctic Ocean completely lose their sea-ice cover during summer (figure 2). This limits the potential for a further acceleration of summer sea ice loss, and causes accelerating sea ice loss during winter.

5. Accelerated sea ice loss during all months of the year is additionally driven by a lengthening of the melt season. As assessed for the Arctic as a whole through April 2018, melt onset is occurring 3 days earlier per decade, and freeze-up is happening 7 days later per decade (figure 3). Over the 40 year long satellite record, this amounts to a 12 day earlier melt onset and a 28 day later freeze-up.

6. The recent winter sea ice loss is driven by increased inflow of warm air from the south and an overall warming of the Arctic, which both have substantially reduced the number of freezing
degree days in recent years (figures 8 and 9).

7. The primary cause of the ongoing changes in all months are anthropogenic CO2 emissions, with a clear linear relationship between sea ice loss and cumulative anthropogenic CO2 emissions in all
months (figure 7). The sensitivity ranges from an ice loss per ton of anthropogenic CO2 emissions
of slightly above 1m2 during winter, to more than 3m2 throughout summer."

-------   
 "Extrapolating the linear relationships into the future, we find that the Arctic Ocean completely loses its ice cover throughout August and September for an additional roughly 800 ± 300 Gt of anthropogenic CO2 emissions. For an additional 1400 ± 300 Gt of anthropogenic CO2 emissions, we estimate the Arctic to become sea-ice free from July throughout October (see Notz and Stroeve 2018 for details on these estimates, in particular regarding the uncertainty arising from internal variability).

Given today’s emission rate of about 40 Gt CO2 per year, the time window is closing very rapidly to preserve Arctic sea-ice cover all year round."
« Last Edit: November 15, 2019, 12:49:37 AM by Glen Koehler »

El Cid

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Re: When will the Arctic Go Ice Free?
« Reply #1357 on: November 15, 2019, 08:05:04 AM »
     
"Once temperatures have risen enough to prevent ice formation during winter, the Arctic Ocean can  rapidly change from an ocean largely ice covered in winter to an ocean that remains ice free throughout winter."

This quote is priceless. It basically says: when there can be no ice, there will be no ice. Talk about tautology :)

Glen Koehler

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Re: When will the Arctic Go Ice Free?
« Reply #1358 on: November 15, 2019, 01:12:12 PM »
      Yeah that one kind of stuck out to me too.   But in my haste I didn't think about it long enough to realize that by removing it from its surrounding context it wasn't adding value. I think the larger point was that the transition of the Arctic seas, and the Arctic as a whole, from one mode and system state to a new condition happens gradually for a long time, then all of sudden it's done.  Similar to thin edge ice hanging on for a long time until it seemingly goes poof. 

       But you are right, the statement standing alone just looks dumb due to my editing, not the author's original intent.  I have taken it out since by itself it doesn't add value.   

         My editing glitches aside, the Stroeve and Notz, and the Notz and Stroeve 2018 papers together serve as a good comprehensive and fairly up to date (changes every day!) primer to the ASI story.  It addressed a lot of the questions I had in an understandable plain language way, and the authors are recognized experts in that arena.  Both articles are free online with open access (no paywall). 
« Last Edit: November 15, 2019, 09:35:18 PM by Glen Koehler »

gerontocrat

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Re: When will the Arctic Go Ice Free?
« Reply #1359 on: November 15, 2019, 01:39:37 PM »
After looking at graphs of individual seas and making comments on them, this is the quote that seems valid, and  even more so, for many of the individual seas.

Changing state of Arctic sea ice across all seasons
Julienne Stroeve and  Dirk Notz

Quote
5. Accelerated sea ice loss during all months of the year is additionally driven by a lengthening of the melt season. As assessed for the Arctic as a whole through April 2018, melt onset is occurring 3 days earlier per decade, and freeze-up is happening 7 days later per decade (figure 3). Over the 40 year long satellite record, this amounts to a 12 day earlier melt onset and a 28 day later freeze-up.
[/size]

The summer melt turns from a V shape  into a U shape
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vox_mundi

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Re: When will the Arctic Go Ice Free?
« Reply #1360 on: November 15, 2019, 02:29:38 PM »
Arctic Ocean May Be Ice-Free for Part of the Year As Soon As 2044
https://phys.org/news/2019-11-arctic-ocean-ice-free-year.html



... For their study, Thackeray and co-author Alex Hall, a UCLA professor of atmospheric and oceanic sciences, set out to determine which models are most realistic in how they weigh the effects of sea ice albedo feedback, which they figured would lead them to the most realistic projections for sea ice loss.

Thackeray and Hall assessed 23 models' depiction of seasonal ice melt between 1980 and 2015 and compared them with the satellite observations. They retained the six models that best captured the actual historical results and discarded the ones that had proven to be off base, enabling them to narrow the range of predictions for ice-free Septembers in the Arctic.



Chad W. Thackeray et al. An emergent constraint on future Arctic sea-ice albedo feedback, Nature Climate Change (2019)
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Glen Koehler

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Re: When will the Arctic Go Ice Free?
« Reply #1361 on: November 15, 2019, 10:03:16 PM »
After looking at graphs of individual seas and making comments on them, this is the quote that seems valid, and  even more so, for many of the individual seas.

Changing state of Arctic sea ice across all seasons
Julienne Stroeve and  Dirk Notz

Quote
5. Accelerated sea ice loss during all months of the year is additionally driven by a lengthening of the melt season. As assessed for the Arctic as a whole through April 2018, melt onset is occurring 3 days earlier per decade, and freeze-up is happening 7 days later per decade (figure 3). Over the 40 year long satellite record, this amounts to a 12 day earlier melt onset and a 28 day later freeze-up.
[/size]

The summer melt turns from a V shape  into a U shape

     Interesting graphical insight gerontocrat.  Seeing those V curves turn into flat bottomed U shapes is a useful visualization of the concept of individual Arctic seas reaching cumulative losses to the point of having temporary ice extinctions.

      Another insight arises from reading your quoting item 5 about the Arctic as a whole gaining 10 days of melt season per decade (starts 3 days earlier, ends 7 days later per decade).  That trend gives a shorthand way of projecting dates for when additional BOE landmarks will occur.  If that rate continued, then once we have September regularly going below the 1M km2 BOE threshold, then every 3 decades after that, at the 1979-2018 melt season expansion rate, the duration of the BOE period would expand by another 30-days.

      I suppose the added low ice/BOE period would be an additional 9 days before and 21 days after the date of annual minimum.  Seems to me that the low ice period would continue to expand forward and backward from the current mid-Septemberish date for annual minimum at the same ratio as before.  Or will that the ratio change as the ice-free period runs into the darkening days of October vs. the sunny dog days of August?  Why is the observed ratio not not the same on either side of the annual minimum, i.e. why 3 days earlier start but 7 days later finish instead of 5 & 5?

     Correlation of global average surface temperature and cumulative CO2 emissions with Arctic sea ice decline stated in the Notz and Stroeve 2018 article at  .....
https://forum.arctic-sea-ice.net/index.php/topic,2348.msg236344.html#msg236344
   ( Oy, citing my own ASIF posts - all I need now is the ability to Like them and my little bubble of narcissism would be complete.  Maybe we should give Trump a special ASIF member privilege to do that in hopes that it would provide a relief valve for his apparently bottomless need for affirmation, and cut back on his Twitterbation.  By now he must be developing the apocryphal hairy thumbs. 
Double oy - I usually discover later than what I criticize in others is often a reflection of some aspect of myself!  So I am ending this digression right now.)

..... suggest a much faster expansion of melt season for the Arctic as a whole than a new month every 30 years.   I suspect that is because the 3 days earlier - 7 days later per decade trend, being based on the 1979-2018 record, is slower than the rate of melt season advancement more recently.  I'll take a second look at Notz and Stroeve to see what date estimates can be extracted for when BOE for Aug, Oct, and July might be expected based on current trends. 
« Last Edit: November 17, 2019, 09:29:18 PM by Glen Koehler »

Klondike Kat

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Re: When will the Arctic Go Ice Free?
« Reply #1362 on: November 17, 2019, 01:58:37 PM »
After looking at graphs of individual seas and making comments on them, this is the quote that seems valid, and  even more so, for many of the individual seas.

Changing state of Arctic sea ice across all seasons
Julienne Stroeve and  Dirk Notz

Quote
5. Accelerated sea ice loss during all months of the year is additionally driven by a lengthening of the melt season. As assessed for the Arctic as a whole through April 2018, melt onset is occurring 3 days earlier per decade, and freeze-up is happening 7 days later per decade (figure 3). Over the 40 year long satellite record, this amounts to a 12 day earlier melt onset and a 28 day later freeze-up.
[/size]

The summer melt turns from a V shape  into a U shape

     Interesting graphical insight gerontocrat.  Seeing those V curves turn into flat bottomed U shapes is a useful visualization of the concept of individual Arctic seas reaching cumulative losses to the point of having temporary ice extinctions.

      Another insight arises from reading your quoting item 5 about the Arctic as a whole gaining 10 days of melt season per decade (starts 3 days earlier, ends 7 days later per decade).  That trend gives a shorthand way of projecting dates for when additional BOE landmarks will occur.  If that rate continued, then once we have September regularly going below the 1M km2 BOE threshold, then every 3 decades after that, at the 1979-2018 melt season expansion rate, the duration of the BOE period would expand by another 30-days.

      I suppose the added low ice/BOE period would be an additional 9 days before and 21 days after the date of annual minimum.  Seems to me that the low ice period would continue to expand forward and backward from the current mid-Septemberish date for annual minimum at the same ratio as before.  Or will that the ratio change as the ice-free period runs into the darkening days of October vs. the sunny dog days of August?  Why is the observed ratio not not the same on either side of the annual minimum, i.e. why 3 days earlier start but 7 days later finish instead of 5 & 5?

..... suggest a much faster expansion of melt season for the Arctic as a whole than a new month every 30 years.   I suspect that is because the 3 days earlier - 7 days later per decade trend, being based on the 1979-2018 record, is slower than the rate of melt season advancement more recently.  I'll take a second look at Notz and Stroeve to see what date estimates can be extracted for when BOE for Aug, Oct, and July might be expected based on current trends.

I think it is the opposite.  Precisely because these seas have bottom out during the summer, they cannot    contribute to a decreased minimum.  The additional melt must stem from the remaining ice - namely the CAB, which still exhibits a V-shape.  This should slow the rate of melt in the near future. 

binntho

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Re: When will the Arctic Go Ice Free?
« Reply #1363 on: November 18, 2019, 09:23:20 AM »
Edited quote
Since the third term is a calculated average (and not a finite measure as the other two) then flipping them around makes no sense.

At least we have identified where we disagree,
I submit that mathematically all are true.
E*T=V
E = V/T
T = V/E

It does not matter to their mathematical relationship which one you solve for, the relation stays the same. 

Sorry to not having been able to participate in this discussion, when travelling to the source of the Nile (or at least the Blue part of it) one is not always within range of usable Internet.

Just to restate why we are discussing this:
  • I stated that if volume was declining faster than extent then thickness would be declining faster than extent as well
  • You said no
  • I worked out the mathematics for the proposition above and proved me right, at least so I thought!
  • You said no
[li]I've looked at it again and perhaps I wasn't entirely correct in my former statements
[/li][/list]

Having said that, I don't see any obvious mathematical reason for why the three relationships you show should also hold for differentials. And although I've forgot how to prove it mathematically, I'm pretty convinced that I'm right. Except that I'm not.

  • E/V = T
does not in my mind imply
  • (((1-δE)/δt)/((1-δV)/δt)) = (1-δT)/δt
as e.g. if solved algebraically:
  • ((1-δE)/δt)/((1-δV)/δt) = (1-δE)/(1-δV) ≠ (1 - δ(E/V))/δt = (1-δT)/δt


where t is time. In other words, from the fact that Extent divided by Volume gives Thickness, it does not automatically (or obviously) follow that the rate of decline of Extent divided by rate of decline of Volume gives the resulting rate of decline of Thickness.

Hovewer, experimenting with Excel seems to show without a doubt that

((1-δE)/δt)/((1-δV)/δt) = (1-δE)/(1-δV) = (1 - δ(E/V))/δt = (1-δT)/δt

Which means that the relationships E/V = T holds for the rate of changes also.

Quote
In your examples you solve for T based on set values for E and V, and you get a T that is greater than E.  But that is not an inherent requirement.  It is simply an artifact of the values you set for E and V.  You could set E and V to different values and find that the resulting T is less than E.

Quite right, there is a crossover when (EROC - VROC) > EROC / VROC

In other words, if the difference between the two rates of change (ROC) becomes smaller than the ratio between them, the ROC of thickness falls behind the ROC of extent.

So it looks like retreat on all fronts for the party which I am in the habit of referring to by using with the perpendicular pronoun.
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binntho

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Re: When will the Arctic Go Ice Free?
« Reply #1364 on: November 18, 2019, 09:24:21 AM »
The above is a long-winded way of totally hiding that what I am actually saying is: "I was wrong". 8)
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binntho

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Re: When will the Arctic Go Ice Free?
« Reply #1365 on: November 18, 2019, 09:27:55 AM »
I think it is the opposite.  Precisely because these seas have bottom out during the summer, they cannot    contribute to a decreased minimum.  The additional melt must stem from the remaining ice - namely the CAB, which still exhibits a V-shape.  This should slow the rate of melt in the near future.
Why should it slow the rate of melt? The CAB will start showing U shapes also, and there will be a seamless transition of U's from the periphery to the center, all following the straight and narrow (and strait) linear relationship between global temperatures and sea ice.
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Klondike Kat

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Re: When will the Arctic Go Ice Free?
« Reply #1366 on: November 18, 2019, 03:01:27 PM »
I think it is the opposite.  Precisely because these seas have bottom out during the summer, they cannot    contribute to a decreased minimum.  The additional melt must stem from the remaining ice - namely the CAB, which still exhibits a V-shape.  This should slow the rate of melt in the near future.
Why should it slow the rate of melt? The CAB will start showing U shapes also, and there will be a seamless transition of U's from the periphery to the center, all following the straight and narrow (and strait) linear relationship between global temperatures and sea ice.

But will it?  Look back at gerontocrat's graphs.  While the peripheral seas have transitioned to the U-shaped melt, the CAB has not.  In fact, it has not changed significantly in a decade.  Both the volume and extent have shown a similar pattern throughout the 2010s, while the rest have degenerated.  Once the peripheral seas reached their u-shaped curve, the CAB stagnated.

binntho

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Re: When will the Arctic Go Ice Free?
« Reply #1367 on: November 18, 2019, 03:18:48 PM »
I think it is the opposite.  Precisely because these seas have bottom out during the summer, they cannot    contribute to a decreased minimum.  The additional melt must stem from the remaining ice - namely the CAB, which still exhibits a V-shape.  This should slow the rate of melt in the near future.
Why should it slow the rate of melt? The CAB will start showing U shapes also, and there will be a seamless transition of U's from the periphery to the center, all following the straight and narrow (and strait) linear relationship between global temperatures and sea ice.

But will it?  Look back at gerontocrat's graphs.  While the peripheral seas have transitioned to the U-shaped melt, the CAB has not.
But it will. It takes time. The U's are creeping into the peripherals, and will eventually overtake the center. If you think they won't, then please explain why? Is there a barrier between the (arbitrarily defined) periphery and center?

Quote
Once the peripheral seas reached their u-shaped curve, the CAB stagnated.

Really. Why. Did the u-shape of the peripheries cause the stagnation? How does that work? What mechanism is involved?

Sorry about being a bit snarky, but deducing things from eyeballing charts without having any plausible mechanism or theory to explain what you see is not enough for me. All the major forces involved indicate that the ice should just continue to melt, generally from south to north, so the peripheries should of course show the effects sooner, but there is nothing that stops that same effect from moving northwards. If you think there is, then tell me!
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crandles

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Re: When will the Arctic Go Ice Free?
« Reply #1368 on: November 18, 2019, 03:31:37 PM »

But will it?  Look back at gerontocrat's graphs.  While the peripheral seas have transitioned to the U-shaped melt, the CAB has not.  In fact, it has not changed significantly in a decade.  Both the volume and extent have shown a similar pattern throughout the 2010s, while the rest have degenerated.  Once the peripheral seas reached their u-shaped curve, the CAB stagnated.

I suggest we need to characterise the top of the U shapes in the peripheral seas. If the top of the U is not really recovering back up to the same level or only noticeably later then we could suggest that the peripheral seas may not do the job of protecting the CAB quite as well and eventually this will lead to CAB doing the same. However the peripheral seas are getting up to the same level and not much later. (The later you push out the bottom of the U then the steeper the side so it isn't clear that this means the top of the U gets much later.) So the peripheral seas are providing pretty much the same protection until quite late in the melt season.

Sufficiently late in season such that there is little chance of melt out of CAB? Well maybe: perhaps it depends on slight timing differences. To me it looks like there are big timing differences going from V to U at the bottom of the curves but at the top of the curves there appears less difference in timing. It seems to me possible that this could continue with the differences in timings getting smaller and smaller such that very little progress is made towards CAB melting out.

I conclude we should give more weight to what you see at the top of the U curves rather than the bottom.

El Cid

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Re: When will the Arctic Go Ice Free?
« Reply #1369 on: November 18, 2019, 03:31:41 PM »
"Is there a barrier between the (arbitrarily defined) periphery and center?"

yes, batyhmetry, and it is not at all arbitrarily defined. It is probably no coincidence that the past 10 years the remaining sea ice is more or less the same as the deep sea arctic. Yes, it will change, and it will melt out eventually. The only question is when. It seems to me that extrapolating from shallow seas to deep seas does not work. At least it has not worked yet...

binntho

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Re: When will the Arctic Go Ice Free?
« Reply #1370 on: November 18, 2019, 03:53:28 PM »
"Is there a barrier between the (arbitrarily defined) periphery and center?"

yes, batyhmetry, and it is not at all arbitrarily defined. It is probably no coincidence that the past 10 years the remaining sea ice is more or less the same as the deep sea arctic. Yes, it will change, and it will melt out eventually. The only question is when. It seems to me that extrapolating from shallow seas to deep seas does not work. At least it has not worked yet...
So the old "bathymetry" argument. If a sea is deeper in the middle then the peripheries are going to be shallower, stands to reason.

But what is missing is any plausible link between ocean depth and how much the sea ice melts, unless we are talking about less than 50 - 100 meters which does not apply to Beaufort, Barents or Kara seas and about half of Laptev, Eas Siberian and Chukchi seas.
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El Cid

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Re: When will the Arctic Go Ice Free?
« Reply #1371 on: November 18, 2019, 05:08:24 PM »
"Is there a barrier between the (arbitrarily defined) periphery and center?"

yes, batyhmetry, a
So the old "bathymetry" argument....

But what is missing is any plausible link between ocean depth and how much the sea ice melts, unless we are talking about less than 50 - 100 meters which does not apply to Beaufort, Barents or Kara seas and about half of Laptev, Eas Siberian and Chukchi seas.

Unfortunately I am not versed in fluid physics and stuff like that so I won't pretend I can give you an explanation though I remember reading some studies detailing the reasons: the main point was that somehow the warm Atlantic/Pacific water can "unstratify" shallow seas but it is much more difficult to do the same to deep seas

Klondike Kat

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Re: When will the Arctic Go Ice Free?
« Reply #1372 on: November 18, 2019, 05:38:59 PM »
"Is there a barrier between the (arbitrarily defined) periphery and center?"

yes, batyhmetry, and it is not at all arbitrarily defined. It is probably no coincidence that the past 10 years the remaining sea ice is more or less the same as the deep sea arctic. Yes, it will change, and it will melt out eventually. The only question is when. It seems to me that extrapolating from shallow seas to deep seas does not work. At least it has not worked yet...
So the old "bathymetry" argument. If a sea is deeper in the middle then the peripheries are going to be shallower, stands to reason.

But what is missing is any plausible link between ocean depth and how much the sea ice melts, unless we are talking about less than 50 - 100 meters which does not apply to Beaufort, Barents or Kara seas and about half of Laptev, Eas Siberian and Chukchi seas.

I am not any better versed in this argument than El Cid.  However, I will say that lacking a plausible mechanism in no way minimizes the deductions from the data.  We cannot ignore the data, just because we do not understand why.

dnem

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Re: When will the Arctic Go Ice Free?
« Reply #1373 on: November 18, 2019, 08:36:40 PM »
lacking a plausible mechanism in no way minimizes the deductions from the data.  We cannot ignore the data, just because we do not understand why.

C'mon, you'd be the first to jump on the "correlation does not imply causation" bandwagon if the data were saying something different.

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Re: When will the Arctic Go Ice Free?
« Reply #1374 on: November 18, 2019, 09:45:26 PM »
A reminder of minimums and bathy since 2012. I would say there is some correlation on the atlantic side.

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Re: When will the Arctic Go Ice Free?
« Reply #1375 on: November 18, 2019, 11:16:03 PM »
lacking a plausible mechanism in no way minimizes the deductions from the data.  We cannot ignore the data, just because we do not understand why.

C'mon, you'd be the first to jump on the "correlation does not imply causation" bandwagon if the data were saying something different.

Wrong!  The data is correct, whether we understand it or not.  We cannot ignore the truth, just because we cannot describe it.

oren

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Re: When will the Arctic Go Ice Free?
« Reply #1376 on: November 19, 2019, 03:31:13 AM »
A reminder of minimums and bathy since 2012. I would say there is some correlation on the atlantic side.
Indeed. And no correlation on the ESS/Beaufort fronts.

binntho

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Re: When will the Arctic Go Ice Free?
« Reply #1377 on: November 19, 2019, 08:02:20 AM »
A reminder of minimums and bathy since 2012. I would say there is some correlation on the atlantic side.
Indeed. And no correlation on the ESS/Beaufort fronts.
I'm afraid that this supposed "correlation" is only due to the fact that both the ice and the deep ocean tends to be towards the middle at the end of the melting season. A bit like the correlation between global temperatures and Caribbean piracy (one of the fundamental tenets of pastafarianism).

To my eyes, the correlation seems to be very speciuos judging from the images above, and the apparent correlation on on the Atlantic side could have more to do with the island groups there than the bathymetry around them. Ice happens on  the surface, and islands breach the surface.
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oren

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Re: When will the Arctic Go Ice Free?
« Reply #1378 on: November 19, 2019, 10:07:49 AM »
Actually the Atlantic side correlation is probably due to physical reasons, as has already been discussed here upthread. Heavy Atlantic water sinking below light Arctic water at the point where the bathymetry allows, unless Arctic water has been heavily mixed and even then it just moves the front rather than eliminate it.
Elsewhere it's probably as you say - the CAB, where September ice is mostly found, happens to be over deep water, so a general correlation is to be expected.  However deep water does not explain the shape of mid-September ice, as uniquorn's animation clearly shows, so no causation.

El Cid

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Re: When will the Arctic Go Ice Free?
« Reply #1379 on: November 19, 2019, 11:25:43 AM »
... Heavy Atlantic water sinking below light Arctic water at the point where the bathymetry allows, unless Arctic water has been heavily mixed and even then it just moves the front rather than eliminate it.

That would imply however that bathymetry DOES play a significant role. Total melting of the CAB in this case can happen in the following two cases:

a) the attack from the pacific side is successful (we probably need a longer season for that or something else I can not think of)
b) mixing does happen on the Atlantic front for some reason (seems unlikely for now)

either way, it still seems to me that linear extrapolation for BOE is useless due to the sinking of Atlantic water under Arctic water (ie. bathymetry)

binntho

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Re: When will the Arctic Go Ice Free?
« Reply #1380 on: November 19, 2019, 11:34:40 AM »
Warm water does not sink because of bathymetry but because it meets water that is ligher (either because it is fresher or because it is less salty - or both).

A warm current can be quite thick and bathymetry obviously affects that where it is shallow enough (probably around 1000m), and once it reaches colder climes I suspect a lot of turbulence is involved as the surface waters lose heat and start sinking, with lower and warmer waters rising instead.
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Shared Humanity

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Re: When will the Arctic Go Ice Free?
« Reply #1381 on: November 19, 2019, 02:43:02 PM »
I also think that Greenland has an impact on the sea ice. This relatively high albedo mass of ice should result in a localized climate that is generally colder across all seasons and would serve to protect sea ice on the Canadian side of the basin. It isn't an accident that the last remaining thick MYI tends to hang out along the Greenland coast and the CAA. The CAA also plays a role here as it has snow cover and higher albedo far longer than other areas of the Arctic.

binntho

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Re: When will the Arctic Go Ice Free?
« Reply #1382 on: November 19, 2019, 03:10:04 PM »
I also think that Greenland has an impact on the sea ice.

But perhaps not as expected! The wind direction is mostly from the Atlantic and in over the ice. As the incoming air gets pushed up, it loses most of it's water vapor as precipitation, which releases a significant amount of latent heat. Once the air plummets back on down on the other side, it's temperature will have increased.

This is of course the famous Foehn effect, and can often be seen clearly in e.g. Nullschool animations when circumstances are right.
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Re: When will the Arctic Go Ice Free?
« Reply #1383 on: November 19, 2019, 04:44:52 PM »
Ice cover on the north-east Greenland coast, the Fram export, correlates more than confidently with bathymetry as well, but in the opposite way.. south flowing cold fresh arctic water fills the entire volume of the sea there and leaves no room for warm atlantic water to enter. A horizontal halocline salinity gradient, protecting the ice. In the artic basins I bet there's all kind of funny slopes, upwellings, overturning currents as a result of bathymetry, quite dynamic.

Isn't the slow rate of the CAB decrease simply a case eating cake from the outside like a caveman would? I don't see nature having any inclination to slice the arctic ice as if it were a birthday pie.

binntho

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Re: When will the Arctic Go Ice Free?
« Reply #1384 on: November 19, 2019, 05:30:27 PM »
Ice cover on the north-east Greenland coast, the Fram export, correlates more than confidently with bathymetry as well, but in the opposite way.. south flowing cold fresh arctic water fills the entire volume of the sea there and leaves no room for warm atlantic water to enter.

I think you are confusing bathometry with the Coriolis effect here. The cold outgoing current is moving south, hence tends towards the west, while the warm ingcoing current is moving north, hence tends to towards the east.

But since cold currents typically follow the seafloor, then bathymetry is obviously coing to effect them significantly. The same doesn't follow for the surfacehugging warm currents.
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Re: When will the Arctic Go Ice Free?
« Reply #1385 on: November 19, 2019, 05:57:02 PM »
I think you thinking we are confused all the time is a little bit of projection :) Why cold current flows south there is irrelevant to the an argument for potential effects of bathymetry on ice melt rate, so I didn't address that.

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Re: When will the Arctic Go Ice Free?
« Reply #1386 on: November 19, 2019, 06:09:27 PM »
A reminder of minimums and bathy since 2012. I would say there is some correlation on the atlantic side.
Wow, uniquorn - you've done some great images in the past, but this one sets a new standard.  Really great work.  Thanks.

Shared Humanity

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Re: When will the Arctic Go Ice Free?
« Reply #1387 on: November 19, 2019, 07:39:22 PM »
A reminder of minimums and bathy since 2012. I would say there is some correlation on the atlantic side.
Indeed. And no correlation on the ESS/Beaufort fronts.
I'm afraid that this supposed "correlation" is only due to the fact that both the ice and the deep ocean tends to be towards the middle at the end of the melting season. A bit like the correlation between global temperatures and Caribbean piracy (one of the fundamental tenets of pastafarianism).

To my eyes, the correlation seems to be very speciuos judging from the images above, and the apparent correlation on on the Atlantic side could have more to do with the island groups there than the bathymetry around them. Ice happens on  the surface, and islands breach the surface.

I get that you feel strongly that there is nothing unique about the ice in the basin that tends to remain at the minimum nor is there any reason to suggest that the ice that tends to exist at the minimum is any more difficult to melt than ice in the peripheral seas.

If you look at the animation, it is clear that ice generally survives the melt season, even the most severe melt seasons, along the coast of the CAA and northern Greenland from McClure Strait to the Fram. This ice at minimum extends to and generally beyond the north pole. This persistent behavior suggests that there are very real reasons that this ice is more difficult to melt. Persons here have suggested bathymetry, the shorter season for sunlight, proximity of Greenland and CAA which serves to anchor or at least minimize movement of the ice pack. You resolutely refute every suggestion provided and then insist that those here provide reasons for suggesting the ice is more resilient. Whatever the reason or reasons, the simple fact is this ice has proven to be more resilient than the rest and there are reasons for this.

Shared Humanity

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Re: When will the Arctic Go Ice Free?
« Reply #1388 on: November 19, 2019, 07:47:20 PM »
To my eyes, the correlation seems to be very speciuos judging from the images above, and the apparent correlation on on the Atlantic side could have more to do with the island groups there than the bathymetry around them. Ice happens on  the surface, and islands breach the surface.

But the islands in fact exist right where they exist, correct? As does the CAA and Greenland exist right, in fact, where they exist. These islands don't, in fact, exist in the middle of the Beaufort and I dare say they likely will never exist there as they seem perfectly happy to exist where they do.

Having said that, the existence of these islands has an obvious effect. They serve to constrict the flow of ice from the Arctic to the Barents where it all would most certainly melt in the summer. These islands then are one reason among many that contributes to the persistence of ice near the pole. They make it more difficult to melt than if it could flow freely into the Barents.

(The CAA and Greenland effect the ice in a similar way but to a larger degree.)

« Last Edit: November 19, 2019, 07:58:47 PM by Shared Humanity »

Shared Humanity

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Re: When will the Arctic Go Ice Free?
« Reply #1389 on: November 19, 2019, 07:54:08 PM »
Let's play a game, a thought experiment. Let's imagine that the entire NH consisted of one vast ocean, no continents or islands to impede the flow of water or the movement of ice. Who here feels that we would already be seeing BOE every year?

(raises hand)

This is, however, not the NH we have. Why do the Beaufort, ESS, and Laptev so readily melt when the basin is proving more resilient?

(Hint: There are reasons. Feel free to pick and choose yours.)



I would argue that bathymetry, proximity to the pole and topographical features which impede the flow of water and the movement of sea ice are a few of those reasons. By the way, these reasons are not going away.

Because I believe these things, there are some new developments over the past few years that concern me. The garlic press is one. The lift off of all MYI from the coast of the CAA and Greenland is another. This ice use to hug the coast but the thickest MYI can now be found drifting north.
« Last Edit: November 19, 2019, 08:13:17 PM by Shared Humanity »

Shared Humanity

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Re: When will the Arctic Go Ice Free?
« Reply #1390 on: November 19, 2019, 08:27:35 PM »
The Beaufort, ESS, Laptev and Kara Seas are all south of 80 degrees. The increased insolation has to be a contributing factor to their melting out just as ice north of 80 degrees is less prone to melting.

binntho

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Re: When will the Arctic Go Ice Free?
« Reply #1391 on: November 20, 2019, 07:20:19 AM »
I think you thinking we are confused all the time is a little bit of projection :)
  ;)
Quote
Why cold current flows south there is irrelevant to the an argument for potential effects of bathymetry on ice melt rate, so I didn't address that.
I wasn't addressing that either. I was addressing this:

Quote
... correlates more than confidently with bathymetry as well, but in the opposite way.. south flowing cold fresh arctic water fills the entire volume of the sea there and leaves no room for warm atlantic water to enter.
There is no warm atlantic water that is trying to enter there, since the warm atlantic water is flowing north and will therefore be to the east. The cold current, flowing south, will hug the western coast if the bathymetry allows (which it does in this case).

However recent events seem to indicate that warm waters do cross the Fram strait close to or at the surface, as can be seen in the Mercator salinity maps over the years. There is a persistent polynia close to the North-Eastern corner of Greenland, indicating upwelling of warm water.

Basically, since warm currents hug the surface, they are well able to cross cold bottom-hugging cold currents, the bathymetry is irrelevant.
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 #1392 on: November 20, 2019, 07:37:20 AM »
 
I get that you feel strongly that there is nothing unique about the ice in the basin that tends to remain at the minimum nor is there any reason to suggest that the ice that tends to exist at the minimum is any more difficult to melt than ice in the peripheral seas.

I do have strong feeling, but not on this subject. What tends to raise my hackles is the tendency too often seen (and so very human) to see patterns in everything, to over-interpret correlations without any notion of causation, to make spurious claims without proper foundation and then maintaining and repeating those claims even when they are shown to be dubious or even plain wrong.

There are many recent examples: The supposed stall, the supposedly "easy" and "difficult" to melt ice types, the supposed effect of bathymetry. All of these "supposeds" stem from our hyperactive pattern-matching abilities. We humans are simply incredibly good at seeing and finding patterns and apparent correlations. But what is lacking is the causality. What are the mechanisms behind these supposed patterns? If you cannot explain the causality, then most likely the pattern only exists in your mind.

Which is not to say that the causality isn't there! Perhaps there was a stall, but then why? Glen Koehler has done a fantastic job of finding real evidence for the fact that ice melts the same everywhere. So any causality behind a stall seems to be very unlikely.

As for bathymetry, I have seen no research that points either way. I do remember some very significant contributers to this forum (people putting in real scientific work) pointing to the apparent correlation between the edges of the continental shelves and the summer mininum. But so far nobody has been able to point to the causality, the mechanism involved. The Laptev bite may be caused by bathymetry, but precisely how? I've not seen any attempts at explaining the underlying mechanism.

So that's why I keep on needling those who think that once you see a correlation, you have discovered a law of nature. It's simply not so.
because a thing is eloquently expressed it should not be taken to be as necessarily true
St. Augustine, Confessions V, 6

macid

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Re: When will the Arctic Go Ice Free?
« Reply #1393 on: November 20, 2019, 02:28:18 PM »
Dear binntho, the patterns I see is what makes my world, it is not a flaw but a feature. Please look at the 2012 year of uniquorn's gif. I could be motivated by constructive talk to overlay some non-minimum ice cover maps to better exemplify how much the ice edge follows the bathy there. Point is, yes there is an effect of bathy on melt rate, what that is depends on.. to be discussed if you like, preferably constructively.

SH echoed my main point his the last comment, CAB melt rate is slower because it's most North and coldest, last to melt. The arctic doesn't get sliced like a pie when it disappears slowly. I don't believe I'm making new laws of nature here?

binntho

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Re: When will the Arctic Go Ice Free?
« Reply #1394 on: November 20, 2019, 02:36:46 PM »
Dear binntho, the patterns I see is what makes my world, it is not a flaw but a feature.
I never said otherwise.
Quote
Please look at the 2012 year of uniquorn's gif. I could be motivated by constructive talk to overlay some non-minimum ice cover maps to better exemplify how much the ice edge follows the bathy there. Point is, yes there is an effect of bathy on melt rate, what that is depends on.. to be discussed if you like, preferably constructively.
Constructively or deconstructively makes no difference. If you think there is a mechanism then please share it with us.

Quote
SH echoed my main point his the last comment, CAB melt rate is slower because it's most North and coldest, last to melt. The arctic doesn't get sliced like a pie when it disappears slowly. I don't believe I'm making new laws of nature here?
Well, yes, that's the world we inhabit: Colder towards the pole, melt progresses from the south to the north. But it doesn't stop or slow down stop at some arbitrary line drawn between the periphery and the center. But if you think there is some factual barrier caused by bathymetry, then please explain.

Waiting with baited breath, yours truly ...  ;)
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 #1395 on: November 20, 2019, 05:37:09 PM »

Waiting with baited breath, yours truly ...  ;)
Go brush your teeth then?

uniquorn

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Re: When will the Arctic Go Ice Free?
« Reply #1396 on: November 20, 2019, 08:56:16 PM »
A possible mechanism for correlation of bathy with summer ice edge from Svalbard to FJL and possibly to SZ. The first animation shows this year's ice drift from oct1-nov18. The east oops, west spitsbergen current is probably not in doubt on this thread. It's effects can be seen on the surface clearly at times during the animation and, in my view, also beneath the ice as leads or lower concentration up until the line where the 'warm water waterfall' falls into the Nansen basin. There may be some mixing but I think the dense, high salinity water sinks quickly to at least 75m, taking the heat with it. edit: Ice colour, normally white, has been inverted to make it easier to see the bathymetry.
2018 from here was a better example but you have to imagine the bathy and forgive the very basic science. Studying that particular argo float data in detail may answer some questions (or raise many many more) 
« Last Edit: November 21, 2019, 03:17:09 PM by uniquorn »

johnm33

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Re: When will the Arctic Go Ice Free?
« Reply #1397 on: November 20, 2019, 10:50:36 PM »
binntho, I think where I most differ with you is that you give the impression your only considering surface and near surface waters. For me there is no resident water in the Norwegian sea, it's constantly being renewed by 'gulf stream/nad' waters from further south, so that water occupies the whole depth. Moving north/east it splits into energetic fractions the densest flowing north along the steep contours of the Barents shelf towards and around Svalbard then east along the shelfs contours and here the turbulence it creates in the waters coming off the shelf causes weak ice to melt. The energetic potential of the lightest fraction [recently at 60degN, @500mph surface speed now 68degN, @370mph] rounding Norway loses some of it's kinetic energy to heat but never enough to allow it to return by the same route, thus there's a constant but variable flow off the shelf into Nansen.
 Enough images here

gerontocrat

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Re: When will the Arctic Go Ice Free?
« Reply #1398 on: November 20, 2019, 11:16:27 PM »
And a posting this evening from Abrupt SLR @ https://forum.arctic-sea-ice.net/index.php/topic,2205.msg237666.html#msg237666

and I quote the first paragraph:-
Quote
The linked article/reference indicates that the Arctic Ocean could be seasonally ice free between 2044 and 2067, by constraining the relationship between sea ice extent and sea ice albedo feedback (SIAF) and found that: 'The relationship is strengthened when models with unrealistically thin historical ice are excluded.'  Obviously, this stronger relationship projects greater Arctic Amplification and consequently greater values of ECS than previously assumed by consensus climate science:

Title: "Arctic Ocean could be ice-free for part of the year as soon as 2044"

https://phys.org/news/2019-11-arctic-ocean-ice-free-year.html

and another link:- http://newsroom.ucla.edu/releases/arctic-sea-ice-melting-2044

and an image.


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binntho

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Re: When will the Arctic Go Ice Free?
« Reply #1399 on: November 21, 2019, 10:33:13 AM »

Waiting with baited breath, yours truly ...  ;)
Go brush your teeth then?
A somewhat unfortunate spelling error. Should have been "bated breath" of course! ;D

But I presume that you have no idea as to any mechanism behind why there should be any correlation between the edge of the continental shelf and the summer ice edge. Well never mind, neither does anybody else that I've seen.
because a thing is eloquently expressed it should not be taken to be as necessarily true
St. Augustine, Confessions V, 6