Support the Arctic Sea Ice Forum and Blog

Poll

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 64492 times)

petm

  • Grease ice
  • Posts: 571
    • View Profile
  • Liked: 248
  • Likes Given: 21
Re: When will the Arctic Go Ice Free?
« Reply #950 on: August 12, 2019, 03:55:13 AM »
Actually that is not so much a heat input as a reduction in heat output.

Sure, but same difference, literally. (When discussing a model that requires a certain change of net "input" to achieve a certain threshold, wrt a factor that wasn't considered in the model. If you catch my drift...)

Klondike Kat

  • Grease ice
  • Posts: 596
    • View Profile
  • Liked: 29
  • Likes Given: 35
Re: When will the Arctic Go Ice Free?
« Reply #951 on: August 12, 2019, 04:16:50 AM »
Quote
Actually that is not so much a heat input as a reduction in heat output.

It is both and input and a reduction of heat output, depending on context.

But really, when you have more heat, and a reduction in heat output, looking at it as input is probably a good thing.

That depends on whether it reduces the heat input also.  It may be a wash.

Archimid

  • Nilas ice
  • Posts: 2171
    • View Profile
  • Liked: 196
  • Likes Given: 161
Re: When will the Arctic Go Ice Free?
« Reply #952 on: August 12, 2019, 04:34:31 AM »
It doesn't look like it. This year will be an excellent test. Will it be like 2012-2013, a record high ice formation, or be like 2016 followed by anemic growth that lead to the lowest max on record?

The next large confluence of oceanic cycles will also be a great test.
I am an energy reservoir seemingly intent on lowering entropy for self preservation.

sja45uk

  • New ice
  • Posts: 16
    • View Profile
  • Liked: 2
  • Likes Given: 17
Re: When will the Arctic Go Ice Free?
« Reply #953 on: August 12, 2019, 05:01:29 AM »
That pattern shows accelerating loss of Sept ice volume. I don't believe that pattern is appropriate.

Following graph is not aggressive enough, but is a better fit and doesn't have R2 anywhere near 99.99%

Based on the increase in CO2, I can see no good reason for you to fit a curve that comes to an asymptote rather than continues to accelerate downwards. Your curve fit seems too dependant on the latest value and seems (to me) to make an unjustified assumption about future values. If you have a physical mechanism that justifies not fitting a linear or exponential, I would be interested to know what it is. Ultimately of course, I suspect it will have to bottom out at close to zero ice in the area, and the refreeze will be delayed longer and longer. How long that will take I am not qualified to guess, but we do not seem to be acting to prevent it happening.

crandles

  • Nilas ice
  • Posts: 2389
    • View Profile
  • Liked: 52
  • Likes Given: 42
Re: When will the Arctic Go Ice Free?
« Reply #954 on: August 12, 2019, 12:30:32 PM »
That pattern shows accelerating loss of Sept ice volume. I don't believe that pattern is appropriate.

Following graph is not aggressive enough, but is a better fit and doesn't have R2 anywhere near 99.99%

Based on the increase in CO2, I can see no good reason for you to fit a curve that comes to an asymptote rather than continues to accelerate downwards. Your curve fit seems too dependant on the latest value and seems (to me) to make an unjustified assumption about future values. If you have a physical mechanism that justifies not fitting a linear or exponential, I would be interested to know what it is. Ultimately of course, I suspect it will have to bottom out at close to zero ice in the area, and the refreeze will be delayed longer and longer. How long that will take I am not qualified to guess, but we do not seem to be acting to prevent it happening.

I don't believe the horizontal extrapolation, I believe it will continue downwards while ghgs are rising.

1. There is discussion in the literature of Multi year Ice (MYI) ceasing to make it around the Beaufort Gyre allowing it to last for a decade and have time to thicken. The quantity of thick MYI fell dramatically over ~2000-2012.

2. When first year ice (FYI) melts out, then each winter it pretty much grows back to normal thickness. When thick MYI reduces to FYI thickness, you don't really get any regrowth as the ice thickness is already at the equilibrium thickness where upwelling heat balances outgoing heat. This means that getting rid of ice volume that is thick MYI can happen relatively fast, but reducing FYI is a long slow process.

3. Winter ice thickness negative feedback: Reduce the ice thickness and more heat flows out of the ocean. This is a fast process, see delays to start up of winter refreeze only being a little later now than 30 years ago. Also even when all the sea ice is removed from models allowing lots of heat to build up in the ocean over the summer, the refreeze still starts by November. Basically there is plenty of time over the winter to vent any heat build up that is likely to occur. Freeze up will become a little later, but thinner ice allows faster heat loss so while there is a deficit in ice thickness, ice forms at a faster rate so tend to catch up in thickness. Reducing the thickness in winter is a long process (once down to FYI thicknesses).

4. Models. Models are good at some things but bad at others. Levels of ice can be all over the place. So one model might says 2070 but another 2040, so on this, it is a bad idea to trust models. However they pretty much all agree that as ice declines towards 0 ice in September, the rate of ice loss slows down. This seems a pretty reliable result to me. Not impossible that all the models are wrong, but you need some pretty strong reasoning to discount what we see from models.

5. Since proposed has the data supported or debunked which ideas? Such sigmoid/gompertz curves have been discussed here since at least 2011 and probably earlier. How have the alternative ideas of accelerating decline versus gompertz shape fits proceeded? See a pair of graphs, 5th row of
https://sites.google.com/site/arctischepinguin/home/piomas

The 4 parameter gompertz I used is debateably better than the 3 parameter gompertz shown there, but what is not in doubt is that either gompertz fit is better than the exponential or any other accelerating downwards fit.

6. If the gompertz fits were just fitting noise and given lack of correlation of noise between maximum and minimum, I think it likely that fitting a curve to September and April volume would be likely to have to have differences in timings to fit the noise. The time of the point of inflection point (around 2005) is within a year between April and September fits. This suggests to me that there is a real pattern going on not just noise.


Not quite sure I can genuinely count all that as 6 different lines of evidence. Nevertheless, how many do I need?


>"not seem to be acting"
Perhaps a little overstated, but I agree we are not doing enough / not acting fast enough on action to reduce AGW.


Shared Humanity

  • Young ice
  • Posts: 3812
    • View Profile
  • Liked: 316
  • Likes Given: 37
Re: When will the Arctic Go Ice Free?
« Reply #955 on: August 13, 2019, 02:25:06 AM »
It doesn't look like it. This year will be an excellent test. Will it be like 2012-2013, a record high ice formation, or be like 2016 followed by anemic growth that lead to the lowest max on record?

The next large confluence of oceanic cycles will also be a great test.

2016 had insanely high temps in the Fall and early Winter. I remember it happening at the time. 2012 had positive anomalies (heck every winter does now) but not as high.

Shared Humanity

  • Young ice
  • Posts: 3812
    • View Profile
  • Liked: 316
  • Likes Given: 37
Re: When will the Arctic Go Ice Free?
« Reply #956 on: August 13, 2019, 02:31:20 AM »
Thank you crandles...