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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 130122 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: Today at 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: Today at 05:32:14 AM by Glen Koehler »

Richard Rathbone

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Re: When will the Arctic Go Ice Free?
« Reply #1353 on: Today at 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: Today at 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?