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 What will the NSIDC 2016 Arctic SIE September minimum be?

Between 5.25 and 5.5 million km2
0 (0%)
Between 5.0 and 5.25 million km2
2 (2%)
Between 4.75 and 5.0 million km2
1 (1%)
Between 4.5 and 4.75 million km2
9 (9.2%)
Between 4.25 and 4.5 million km2
23 (23.5%)
Between 4.0 and 4.25 million km2
21 (21.4%)
Between 3.75 and 4.0 million km2
12 (12.2%)
Between 3.5 and 3.75 million km2
13 (13.3%)
Between 3.25 and 3.5 million km2
2 (2%)
Between 3.0 and 3.25 million km2
3 (3.1%)
Between 2.75 and 3.0 million km2
3 (3.1%)
Between 2.5 and 2.75 million km2
1 (1%)
Between 2.25 and 2.5 million km2
1 (1%)
Between 2.0 and 2.25 million km2
3 (3.1%)
Between 1.75 and 2.0 million km2
1 (1%)
Between 1.5 and 1.75 million km2
1 (1%)
Between 1.25 and 1.5 million km2
0 (0%)
Between 1.0 and 1.25 million km2
0 (0%)
Between 0.75 and 1.0 million km2
2 (2%)
Between 0.5 and 0.75 million km2
0 (0%)
Between 0.25 and 0.5 million km2
0 (0%)
Between 0 and 0.25 million km2
0 (0%)

Total Members Voted: 93

Voting closed: August 11, 2016, 01:04:49 PM

Author Topic: NSIDC 2016 Arctic SIE September minimum: August poll  (Read 26717 times)

Neven

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NSIDC 2016 Arctic SIE September minimum: August poll
« on: August 01, 2016, 01:04:49 PM »
ATTENTION: There are two polls on the ASIF. One is for NSIDC sea ice extent monthly/September average minimum (the one that is used for the SIPN sea ice outlook), the other is for JAXA sea ice extent daily minimum (provided by ADS, previously by IJIS). Make sure you are aware of the difference before voting. You can discuss various extent/area data sets in this dedicated thread.

-----

This NSIDC extent poll will run for 10 days (until August 11th). Until then you can change your vote. This is the last poll for this melting season.

Here's how things are currently looking based on data up to July 31st:



These are the September minimums for the last 11 years (in millions km2, found here):

    2005: 5.57
    2006: 5.92
    2007: 4.30
    2008: 4.73
    2009: 5.39
    2010: 4.93
    2011: 4.63
    2012: 3.63
    2013: 5.35
    2014: 5.28
    2015: 4.63

You can use the comment thread below to motivate your choice, but discuss various SIE/SIA data sets in this dedicated thread.
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Neven

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Re: NSIDC 2016 Arctic SIE September minimum: August poll
« Reply #1 on: August 01, 2016, 01:15:03 PM »
I'm going to go down one bin compared to last month's poll: between 4.25 and 4.5 million km2.

I may even change my vote and go down one bin more before the time to vote ends (August 11th), but it will take spectacular events.
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slow wing

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Re: NSIDC 2016 Arctic SIE September minimum: August poll
« Reply #2 on: August 01, 2016, 01:39:00 PM »
Sticking with my last month's prediction of 3.00-3.25 million square kilometres and a new record, beating the previous record of 3.63 in those units from 2012.

So now 2 bins above my prediction in the other thread for the daily minimum for this season, which dropped one bin there for the reasons given in my comment.

Thawing Thunder

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Re: NSIDC 2016 Arctic SIE September minimum: August poll
« Reply #3 on: August 01, 2016, 02:29:27 PM »
I see it second below 2007, but still above 4 million (the daily number I guessed clearly below 4 million, though). So my guess here: 4,0-4,25 million.
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Re: NSIDC 2016 Arctic SIE September minimum: August poll
« Reply #4 on: August 01, 2016, 02:38:11 PM »
SPIE http://cires1.colorado.edu/~aslater/SEAICE/ (a prediction of extent 50 days ahead based on current area) has been running very close to 4.4 since the end of August. This is the right time frame to be using a SPIE type of method, although ideally it would be one based on statistics of daily area and monthly extent rather than daily extent.

Their calculation methods result in monthly extent being somewhat higher than the average of the daily extents in September, so I'm sticking with 4.5-4.75.

seaicesailor

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Re: NSIDC 2016 Arctic SIE September minimum: August poll
« Reply #5 on: August 01, 2016, 04:42:14 PM »
Staying at 4 - 4.25 M km2.

Juan C. García

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Re: NSIDC 2016 Arctic SIE September minimum: August poll
« Reply #6 on: August 01, 2016, 04:57:07 PM »
Staying at 4 - 4.25 M km2.

Me too. A little lower than 2007.
Which is the best answer to Sep-2012 ASI lost (compared to 1979-2000)?
50% [NSIDC Extent] or
73% [PIOMAS Volume]

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

AmbiValent

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Re: NSIDC 2016 Arctic SIE September minimum: August poll
« Reply #7 on: August 01, 2016, 04:58:15 PM »
I chose "one bin above 2012" for both polls.
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icefisher

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Re: NSIDC 2016 Arctic SIE September minimum: August poll
« Reply #9 on: August 02, 2016, 01:04:49 AM »
Raised extent up a little to reflect the continuing dispersal of floes and rubble.  Expect 4.316 within a range of 4.23 - 4.38.  The volume number, the most important, is difficult to assess without any good measurement.  A dart board guess - 4.8 at the October minima?

Peter Ellis

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Re: NSIDC 2016 Arctic SIE September minimum: August poll
« Reply #10 on: August 02, 2016, 01:32:06 PM »
Somewhere between 2007 and 2012.

jdallen

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Re: NSIDC 2016 Arctic SIE September minimum: August poll
« Reply #11 on: August 02, 2016, 06:05:38 PM »
Somewhere between 2007 and 2012.
A good summation of what a majority of us are probably thinking.
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meddoc

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Re: NSIDC 2016 Arctic SIE September minimum: August poll
« Reply #12 on: August 04, 2016, 11:31:35 PM »
Down to 1,75- 2,0 M km2 due to recent dipolish

VeliAlbertKallio

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Re: NSIDC 2016 Arctic SIE September minimum: August poll
« Reply #13 on: August 05, 2016, 12:42:53 AM »
Accepting new US Navy model's faults and putting up 1 million km2 to 2.75-3.00 million km2. However, every observer must remember that the more pulverized the sea ice becomes, the harder it is to estimate melting because the melt is increasingly driven by mixing of pulverised ice with sea water. (Water-sitting 3-dimensional ice surface area grows towards infinity the more pulverized and smaller the pieces of sea ice become - this facilitates ever greater heat transfers between water and ice. Strong winds mix sea water more efficiently in these circumstances. Very strong storm winds would destroy ice now rapidly, while more moderate winds keep ice disappearing steadily.
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Michael Hauber

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Re: NSIDC 2016 Arctic SIE September minimum: August poll
« Reply #14 on: August 05, 2016, 06:06:18 AM »
Sticking to with just a bit below 07 and voting for 4-4.25
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Re: NSIDC 2016 Arctic SIE September minimum: August poll
« Reply #15 on: August 05, 2016, 06:42:22 PM »
I'll have a triple thanx: 3.75 to 4 one more time, cheers!!!
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Tealight

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Re: NSIDC 2016 Arctic SIE September minimum: August poll
« Reply #16 on: August 05, 2016, 07:38:59 PM »
The July NSIDC area decrased at average rate, but the extent/area ratios were at -1SD so my August forecast is lower than the actual area. This divergence is similar to 2010, which predicted the final area value within 90km2 so it doesn't mean the model is totally off.

Daily minimum Area
+1SD: 2.862
avg: 2.751
-1SD: 2.628

Average NSIDC September extent
+1SD: 4.58
avg: 4.40
-1SD: 4.205

Attached is the July forecast vs observation and the August forecast for the remainding season.
« Last Edit: August 05, 2016, 08:48:27 PM by Tealight »

Sleepy

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Re: NSIDC 2016 Arctic SIE September minimum: August poll
« Reply #17 on: August 07, 2016, 08:58:36 AM »
4.25-4.50

budmantis

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Re: NSIDC 2016 Arctic SIE September minimum: August poll
« Reply #18 on: August 08, 2016, 05:52:14 PM »
3.5 to 3.75 which will only happen if the weather from this point forward is favorable for melting and compacting.

Juan C. García

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Re: NSIDC 2016 Arctic SIE September minimum: August poll
« Reply #19 on: August 09, 2016, 09:09:44 PM »
Going up one bin, before the poll ends.  ::)
Now on the 4.25-4.5 range.
Which is the best answer to Sep-2012 ASI lost (compared to 1979-2000)?
50% [NSIDC Extent] or
73% [PIOMAS Volume]

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

P-maker

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Re: NSIDC 2016 Arctic SIE September minimum: August poll
« Reply #20 on: August 10, 2016, 07:10:54 AM »
Still waiting for an unknown sequence of unprecedented events to move the # < 3.5 M km2.

Sterks

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Re: NSIDC 2016 Arctic SIE September minimum: August poll
« Reply #21 on: August 10, 2016, 01:46:00 PM »
Hello all. I'm a new member and wanted to cast my vote. This is 4.5 to 4.75 million of km2. No other reason that the extent is not dropping as was being expected by the forum people, and extrapolating from other slower years this is what I find.
Nothing else just my first contribution to the forum. Thank you.  :)

OSweetMrMath

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Re: NSIDC 2016 Arctic SIE September minimum: August poll
« Reply #22 on: August 10, 2016, 07:20:24 PM »
My time series model for sea ice extent is relatively stable this year, so although the July extent came in slightly higher than predicted, I am still predicting that the September extent will be in the 4.5-4.75 range.

Dundee

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Re: NSIDC 2016 Arctic SIE September minimum: August poll
« Reply #23 on: August 10, 2016, 11:47:01 PM »
My vote falls at 4-4.5. Not a very exciting projection, but the most popular.

A straight line least squares projection from currently published 1979-2015 final summary numbers works out to 4.69, the standard deviation of residuals is 0.558.

After running many correlations between published daily ice metrics and the September average, so far it looks like the residual between daily NSIDC extent and its expected value (based on long term trend) is the best early August indicator of the September result. A few of the other residuals are plotted below. As the melting season progresses the best indicator shifts, and forecast ability improves (as expected - the daily residuals into September are of course very closely correlated to the average for the month). I did not look at everything by any means but of the dozens of things I did look at, the most informative are on the chart.

I've also included a plot of the resulting straight line fit between early August daily and September monthly numbers, and it doesn't look too bad.

Plugging in the numbers the refined forecast, corrected based on yesterday's extent, works out to 4.47. The standard deviation of residuals for similarly corrected projections going back to 1979 is 0.252, a significant improvement over 0.558. It should possible to get better predictions day by day, but the cutoff for the poll is arriving, so 4.47 is it.

The problem is this. The residuals are not normally distributed and the closer to the maximum the worse they get. The minimum and nearby months are declining faster than the rest of the year. The standard deviation of all daily residuals in September is somewhat less than the standard deviation of residuals for the monthly average. Normal statistics say a monthly average will be better behaved than that for any given day but, for September, averaging over 30 days does nothing to improve the behavior of the numbers. Large residuals from a statistically improbable number of very low ice years (relative to trend) completely overshadow any averaging out of the much smaller day to day variability.

It would be great if we could identify the outlier years in, say, May, but based on the factors I've checked so far, I can't really say even this late in the season that 2016 will not jump off a cliff and be an extreme melt year.

So if it is a normal year the minimum at 4.5ish will be low but not remarkably off trend. If it is the one in five to ten years that are bizarre, it could easily break 2012. I haven't the foggiest idea which way it will go but, looking only at statistics, I haven't found anything that convincingly justifies the little voice that says things will drop through 4.5.



 

epiphyte

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Re: NSIDC 2016 Arctic SIE September minimum: August poll
« Reply #24 on: August 11, 2016, 04:59:47 AM »
I went up a bin from last month, to 3.25-3.5. Still think that a new record is possible.

Neven

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Re: NSIDC 2016 Arctic SIE September minimum: August poll
« Reply #25 on: August 13, 2016, 04:21:32 PM »
I have just calculated the final result of this poll. Below are the results for all three polls this year. It's interesting to see how the general ASIF opinion developed. I think if it weren't for a handful of people who keep voting below 1 million, never mind what the ice does, the group predictions would be even more decent.

Thanks for voting, everyone!
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slow wing

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Re: NSIDC 2016 Arctic SIE September minimum: August poll
« Reply #26 on: August 14, 2016, 01:52:38 AM »
I have just calculated the final result of this poll. Below are the results for all three polls this year. It's interesting to see how the general ASIF opinion developed. I think if it weren't for a handful of people who keep voting below 1 million, never mind what the ice does, the group predictions would be even more decent.

Thanks for voting, everyone!
Neven, thanks for this collation and, more broadly, for this wonderful forum and blog.

With the greatest of respect though, 2 people out of 98 voted 0.75-1.00 million km2 and nobody voted below that.

There is no indication that those 2 were anything other than sincere and, personally, I don't find their prediction to have even been infeasible, let alone indecent.

I myself voted well below the relatively decent August mean and median of 3.87 & 4.17 million km2, respectively. My vote was both considered and sincere, even if inexpert, and I'm not going to apologise for it.

While politicians, deniers and lobbyists may disagree with me, the only indecency here - and it is a gross indecency - is what is happening to the Arctic, with human fingerprints all over it.

So please use the word 'conservative' if you must, rather than 'decent'. In my view, 'conservative' anyway doesn't equate with good science. Instead, the evidence is overwhelming that the Arctic sea ice is disappearing, year-by-year within the fluctuations, even though that is not the conservative thing to do.

philiponfire

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Re: NSIDC 2016 Arctic SIE September minimum: August poll
« Reply #27 on: August 14, 2016, 02:09:47 AM »
I have just calculated the final result of this poll. Below are the results for all three polls this year. It's interesting to see how the general ASIF opinion developed. I think if it weren't for a handful of people who keep voting below 1 million, never mind what the ice does, the group predictions would be even more decent.

Thanks for voting, everyone!
there is a number of people who clearly have no idea what they are voting on. I suggest that next year you introduce a cut off point of 2.5 million for this poll. arbitrary I know but then so is the upper limit.

Archimid

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Re: NSIDC 2016 Arctic SIE September minimum: August poll
« Reply #28 on: August 14, 2016, 02:35:52 AM »
As a 0 voter, if voting for such number is to be considered indecent, then may suggest that such number is not included?  I still think that back in June,  0  ice by September was not an absurd bet. It was unlikely, but possible with huge consequences. In July it was much less likely, but the volume numbers seemed to be plummeting at the time, so I took the low probability/high "payoff" again.

Because the 0 depends on the ice opening up early, in August I no longer voted 0. There is simply not enough time for sunlight to accumulate even if there was big melt going on. So in August I defaulted to what I have seen the models predict. The low probability event is so low that it could be 0.
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seaicesailor

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Re: NSIDC 2016 Arctic SIE September minimum: August poll
« Reply #29 on: August 14, 2016, 04:55:33 AM »
I have just calculated the final result of this poll. Below are the results for all three polls this year. It's interesting to see how the general ASIF opinion developed. I think if it weren't for a handful of people who keep voting below 1 million, never mind what the ice does, the group predictions would be even more decent.

Thanks for voting, everyone!
For these cases with absurd tails (as with the unequal distribution of incomes) it is the median what matters and as you see it is very close to the peak of the distribution.
I wouldnt remove the bins down to 0, does it really matter? You would end up with a big bunch of voters on the < 2.5 M km2 bin causing similar distortion.

Neven

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Re: NSIDC 2016 Arctic SIE September minimum: August poll
« Reply #30 on: August 14, 2016, 11:19:06 AM »
I have just calculated the final result of this poll. Below are the results for all three polls this year. It's interesting to see how the general ASIF opinion developed. I think if it weren't for a handful of people who keep voting below 1 million, never mind what the ice does, the group predictions would be even more decent.

Thanks for voting, everyone!
For these cases with absurd tails (as with the unequal distribution of incomes) it is the median what matters and as you see it is very close to the peak of the distribution.
I wouldnt remove the bins down to 0, does it really matter? You would end up with a big bunch of voters on the < 2.5 M km2 bin causing similar distortion.

Exactly, it makes it more difficult to calculate average and median.

I didn't mean decent as in 'following etiquette' or 'being polite'. I just meant closer to the final result. As in: That's a pretty decent result. Didn't mean to offend anyone.

If people want to vote below 1 million km2, I'm of course fine with that. I don't mind the poll results being lower, we're all worried, and I myself will almost always vote a bit lower than conservative. But at a certain point it should be clear that the Arctic will not go below 1 million km2.

Again, I don't mind people voting that low, not at all. I'm just saying that the average/median vote will be closer to the minimum if they don't. This year.

Of course, there will come a melting season when low voters will turn out to be right. But a lot of the people who vote conservative now, will be voting a lot lower then too. Because we have a pretty good view of what's going on, short-term. Not perfect, but pretty good.
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echoughton

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Re: NSIDC 2016 Arctic SIE September minimum: August poll
« Reply #31 on: August 14, 2016, 12:13:49 PM »
Thanks Neven...you said

"I have just calculated the final result of this poll. Below are the results for all three polls this year. It's interesting to see how the general ASIF opinion developed. I think if it weren't for a handful of people who keep voting below 1 million, never mind what the ice does, the group predictions would be even more decent."

Indeed this is the main reason I voted for 5--5.25....to try to mitigate the minimalists...LOL

Neven

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Re: NSIDC 2016 Arctic SIE September minimum: August poll
« Reply #32 on: August 14, 2016, 11:47:53 PM »
Don't vote tactical, just vote what you think the minimum will be.

If I remove all the votes below 3 million and above 5 million (14 out of a total 98 votes), which by August were clearly highly improbable (IMO), I get an average of 4.09 and a median of 4.11.

That's just playing with the numbers. It doesn't necessarily mean a thing.
« Last Edit: August 14, 2016, 11:54:44 PM by Neven »
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slow wing

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Re: NSIDC 2016 Arctic SIE September minimum: August poll
« Reply #33 on: August 15, 2016, 12:54:16 AM »
...there is a number of people who clearly have no idea what they are voting on...

...If I remove all the votes below 3 million and above 5 million (14 out of a total 98 votes), which by August were clearly highly improbable (IMO), I get an average of 4.09 and a median of 4.11...
This is the part I am missing: how it is already clear.

The forecast is for the Arctic Basin on spin cycle for the rest of August. So the extent will drop below 3 million km2 due to bottom melt if only there is sufficient heat in the water. (Where 'sufficient' is defined by that sentence.)

My understanding is there isn't data available to demonstrate that one way or the other, so we must make our best guesses. But I must be wrong on that so can the people saying it's clear please provide that data source.

Neven

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Re: NSIDC 2016 Arctic SIE September minimum: August poll
« Reply #34 on: August 15, 2016, 01:23:02 AM »
Just look at 2012. Conditions for large losses were much better (and they happened), but 2012 ended at 3.63 million km2 (off the top of my head, I'm too lazy to scroll up). So, how can 2016, being behind 2012 so much already on the last day of the poll, after the melting season so far (clouds, clouds, clouds) and given PIOMAS numbers, satellite images, surface air temps, etc, etc, etc, possibly go below 3 million for the NSIDC September average?

It's already a highly interesting melting season that might go really low even though weather conditions weren't conducive to melting most of the time when it mattered (June, July). Why isn't this worrisome enough? Why does it have to be some Hollywood scenario nobody foresaw, except for the guys who foresee it every year? And what has to happen the year after that to keep things worrisome? Or will we then be bored by the Hollywood scenario, just like we are with real Hollywood scenarios?
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seaicesailor

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Re: NSIDC 2016 Arctic SIE September minimum: August poll
« Reply #35 on: August 15, 2016, 01:32:26 AM »
...there is a number of people who clearly have no idea what they are voting on...

...If I remove all the votes below 3 million and above 5 million (14 out of a total 98 votes), which by August were clearly highly improbable (IMO), I get an average of 4.09 and a median of 4.11...
This is the part I am missing: how it is already clear.

The forecast is for the Arctic Basin on spin cycle for the rest of August. So the extent will drop below 3 million km2 due to bottom melt if only there is sufficient heat in the water. (Where 'sufficient' is defined by that sentence.)

Just one remark, if you notice ( as others noted before, and just I posted a gif in the main thread) the center of the storm falls well at the center of the pack. That means this time it will be grossly inflated (if that is a good word) and there will be a lot of ice transport into the ESS bite, the Beaufort sector, and the Atlantic front. It is not only bottom melt, it is whether these seas have enough heat to melt the castaways before September.
It will be slower drop for sure (I did not say smaller but I think so too), I can safely speculate in this thread :-)
Also, this is coming one week later. One week of melting season in August is a very long time.

slow wing

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Re: NSIDC 2016 Arctic SIE September minimum: August poll
« Reply #36 on: August 15, 2016, 01:51:47 AM »
Thanks for your reply, Neven. All I would say is each year is different. There are pluses and minuses for 2016 relative to 2012 and there are even bigger unknowns. For instance, the ice distribution is just different.

Independent to my views, for example, on 8 August the poster Quantum drew his guess at the final ice envelope that to me looks eminently reasonable and also less than 3 million km2 (for scale the latitude=85N circle is slightly less than 1 million km2). His post is at here.

Quantum also explains his working and you can see he has followed that. In my view, reasoned predictions such as that of Quantum should not be simply set aside as 'clearly' unreasonable, as if by decree.
« Last Edit: August 15, 2016, 02:04:57 AM by slow wing »

Neven

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Re: NSIDC 2016 Arctic SIE September minimum: August poll
« Reply #37 on: August 15, 2016, 09:48:38 AM »
Not by decree, I agree.
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Richard Rathbone

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Re: NSIDC 2016 Arctic SIE September minimum: August poll
« Reply #38 on: August 15, 2016, 03:01:19 PM »
Slater's reporting his mean for September as 4.39 for the 50 day ahead forecast.

http://cires1.colorado.edu/~aslater/SEAICE/

I think he's using a mean of the daily values rather than the monthly extent which is calculated in a different manner and would normally give a higher value than the daily mean in September.

The map currently up there is normally a 50 day ahead one, so you might need to look today in order to see the September mean one.

epiphyte

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Re: NSIDC 2016 Arctic SIE September minimum: August poll
« Reply #39 on: August 16, 2016, 07:33:21 AM »

Just look at 2012. Conditions for large losses were much better (and they happened), but 2012 ended at 3.63 million km2 (off the top of my head, I'm too lazy to scroll up). So, how can 2016, being behind 2012 so much already on the last day of the poll, after the melting season so far (clouds, clouds, clouds) and given PIOMAS numbers, satellite images, surface air temps, etc, etc, etc, possibly go below 3 million for the NSIDC September average?


I didn't vote below 3M - but I was in the 3.5-3.25 bin, which would be a record and is lower than most - so playing devils advocate, a few examples of unlikely but possible factors which could take it below 3M:

- the melt season could end two weeks late. (it did after all start two weeks early, so who is to say that's impossible....)

- The unprecedented level of fragmentation might permit rough seas in the CAB for the first time in memory, which would invalidate existing model assumptions re: surface temperature & salinity, and hence mis-predict the magnitude of end-of-season bottom melt.

- PIOMAS volumes for the last ~1M of modeled thickness may have always been systematically off by a few decimeters at this point in the season, or density & melt-rate for thin ice may be poorly understood, in a way that has been obscured in the past by forcing modeled thickness to zero for observed open water. (I'd venture that none of the very few buoys out there were initially placed on new or partially melted-out ice, which has accounted for much of the extent in recent years, and apart from those, there's radar, which is finicky and tells us nothing about density, satellite images, which tell us nothing about thickness, or even much about the difference at fine granularity between extent and area, and surface air temps, which tell us nothing more than "all the ice hasn't melted yet").

... In other words a less-than-perfect volume model would be undetectable until after the fact, and would make uniformly thin ice less predictable, paving the way for a potential late-season surprise)

- the widely-distributed open water and unusually (unprecedentedly) warm southern latitudes might engender more severe weather than heretofore observed (which to some extent seems to possibly be happening right now).

...In this context it's worth noting that the surface area of the Northern Hemisphere is ~255 million sq. km, much of which is the warmest it has been in recorded history. So although the likelihood of a change in the weather, encouraging unusual melt due to mixing between ~1% of the surface which is covered with very thin ice and the anomalous energy accumulated over the summer across the other 99% might be unquantifiable, it hardly seems "impossible".

I could go on, but hopefully the above is enough to help to reinforce something that is self-evident from the day-to-day accuracy of, for example, the ECMWF 5-day forecast: Science is quantifiable, but reality is chaotic. IMO we have for several years been in the regime where the difference between ice and no-ice quite plausibly comes down to chaos. If you have ever said at this time of year "it all depends on the weather" then at some level you know this to be true.

Quote

It's already a highly interesting melting season that might go really low even though weather conditions weren't conducive to melting most of the time when it mattered (June, July). Why isn't this worrisome enough? Why does it have to be some Hollywood scenario nobody foresaw, except for the guys who foresee it every year? [...]


IMO the most interesting part of the melt season will always be the end, because that is the time in the year at which the science of the models can most visibly come into conflict with the chaos of reality. If my own predictions have so far tended to come in on the low side it is simply a reflection of this... Hollywood scenarios are not required or expected!

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Re: NSIDC 2016 Arctic SIE September minimum: August poll
« Reply #40 on: August 16, 2016, 11:59:25 AM »
@epiphyte

Your arguments could be valid for sea ice area and to some degree the daily minimum sea ice extent, but not the NSIDC September average extent which this poll is about.

NSIDC sea ice extent monthly/September average minimum (the one that is used for the SIPN sea ice outlook)

Quote from: SIPN sea ice outlook
(To be consistent with the validating sea ice extent index from NSIDC, if possible,
 please first compute the average sea ice concentration for the month and
then compute the extent as the sum of cell areas > 15%.)

The NSIDC average monthly extent is a highly inflated average and in my view doesn't reflect the actual ice conditions very well.

Here is an example:

Daiy sea ice concentration of one cell
60   50   50   50   50   40   40   30   30   20   20   20   10   10   10   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0

average: 16.3%
Therefore this cell counts as 100% ice covered for September

As you can see the cell melted out completly by 15th September, had low concentration to begin with, but still counts 100% of the cell area as sea ice.

If you have a persistent ice floe with 100% concentration then it only needs to stay 4.5 days in a cell to count towards the monthly average ice cover. As the arctic ice becomes more and more fragmented and mobile this artificial ice extent increase will become more and more pronounced.
« Last Edit: August 16, 2016, 12:06:39 PM by Tealight »

Richard Rathbone

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Re: NSIDC 2016 Arctic SIE September minimum: August poll
« Reply #41 on: August 16, 2016, 03:07:08 PM »
@epiphyte

Your arguments could be valid for sea ice area and to some degree the daily minimum sea ice extent, but not the NSIDC September average extent which this poll is about.

NSIDC sea ice extent monthly/September average minimum (the one that is used for the SIPN sea ice outlook)

Quote from: SIPN sea ice outlook
(To be consistent with the validating sea ice extent index from NSIDC, if possible,
 please first compute the average sea ice concentration for the month and
then compute the extent as the sum of cell areas > 15%.)

The NSIDC average monthly extent is a highly inflated average and in my view doesn't reflect the actual ice conditions very well.

Here is an example:

Daiy sea ice concentration of one cell
60   50   50   50   50   40   40   30   30   20   20   20   10   10   10   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0

average: 16.3%
Therefore this cell counts as 100% ice covered for September

As you can see the cell melted out completly by 15th September, had low concentration to begin with, but still counts 100% of the cell area as sea ice.

If you have a persistent ice floe with 100% concentration then it only needs to stay 4.5 days in a cell to count towards the monthly average ice cover. As the arctic ice becomes more and more fragmented and mobile this artificial ice extent increase will become more and more pronounced.

NSIDC monthly extent is not an average extent, it is an extent based on the average of concentration measurements during the month. (NSIDC aren't always clear on this point themselves outside their technical pages, so confusion about it is common.)


Juan C. García

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Re: NSIDC 2016 Arctic SIE September minimum: August poll
« Reply #42 on: August 16, 2016, 10:08:27 PM »
@epiphyte

Your arguments could be valid for sea ice area and to some degree the daily minimum sea ice extent, but not the NSIDC September average extent which this poll is about.

NSIDC sea ice extent monthly/September average minimum (the one that is used for the SIPN sea ice outlook)

Quote from: SIPN sea ice outlook
(To be consistent with the validating sea ice extent index from NSIDC, if possible,
 please first compute the average sea ice concentration for the month and
then compute the extent as the sum of cell areas > 15%.)

The NSIDC average monthly extent is a highly inflated average and in my view doesn't reflect the actual ice conditions very well.

Here is an example:

Daiy sea ice concentration of one cell
60   50   50   50   50   40   40   30   30   20   20   20   10   10   10   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0

average: 16.3%
Therefore this cell counts as 100% ice covered for September

As you can see the cell melted out completly by 15th September, had low concentration to begin with, but still counts 100% of the cell area as sea ice.

If you have a persistent ice floe with 100% concentration then it only needs to stay 4.5 days in a cell to count towards the monthly average ice cover. As the arctic ice becomes more and more fragmented and mobile this artificial ice extent increase will become more and more pronounced.

NSIDC monthly extent is not an average extent, it is an extent based on the average of concentration measurements during the month. (NSIDC aren't always clear on this point themselves outside their technical pages, so confusion about it is common.)

I discussed this subject before. Even I made some graphs about it.
In October, the difference between "Real Average" and "NSIDC Average" can be more than 1 million km2:

http://forum.arctic-sea-ice.net/index.php/topic,1274.msg53243.html#msg53243

http://forum.arctic-sea-ice.net/index.php/topic,357.msg8312.html#msg8312

Edit: On the second link, there are several graphs that follow the first link message.
« Last Edit: August 16, 2016, 10:17:03 PM by Juan C. García »
Which is the best answer to Sep-2012 ASI lost (compared to 1979-2000)?
50% [NSIDC Extent] or
73% [PIOMAS Volume]

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

magnamentis

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Re: NSIDC 2016 Arctic SIE September minimum: August poll
« Reply #43 on: August 17, 2016, 01:55:14 AM »
which would invalidate existing model assumptions

i think that's the point all the time this year, old models simply seem to fail, while the numbers may be more or less correct as to extent and area i think thickness calculations are flawed and the fragmentation does not flow appropriately into old algorithms.

however, i won't lean out of the window to far as it's really not easy to tell but i'm still convinced that we are in for a greater surprise. to repeat and avoid misunderstandings, my vote i still second to 2012 in extent and area but once thickness will be calculated correctly i say that 2016 is in reality a new record in volume, even though the
stats and graphs don't show yet.

abbottisgone

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Re: NSIDC 2016 Arctic SIE September minimum: August poll
« Reply #44 on: August 22, 2016, 05:05:46 AM »
Don't vote tactical, just vote what you think the minimum will be.

If I remove all the votes below 3 million and above 5 million (14 out of a total 98 votes), which by August were clearly highly improbable (IMO), I get an average of 4.09 and a median of 4.11.

That's just playing with the numbers. It doesn't necessarily mean a thing.
I was just about to suggest that you could release two sets of figures,... but then I thought better of it  ;D

Thanx for posting those numbers aswell: interesting alright!
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Re: NSIDC 2016 Arctic SIE September minimum: August poll
« Reply #45 on: August 22, 2016, 05:13:19 AM »
Thanks for your reply, Neven. All I would say is each year is different. There are pluses and minuses for 2016 relative to 2012 and there are even bigger unknowns. For instance, the ice distribution is just different.

Independent to my views, for example, on 8 August the poster Quantum drew his guess at the final ice envelope that to me looks eminently reasonable and also less than 3 million km2 (for scale the latitude=85N circle is slightly less than 1 million km2). His post is at here.

Quantum also explains his working and you can see he has followed that. In my view, reasoned predictions such as that of Quantum should not be simply set aside as 'clearly' unreasonable, as if by decree.
Yeh, I read that: that was quite ingenious I thought. Yes, there may be better methods but I thought that was actually a really intelligent way to go about it: atleast to double check what others were saying.

I liked it.
..
But I left school and grew my hair
They didn't understand
They wanted me to be respected as
A doctor or a lawyer man
But I had other plans..........

Tealight

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Re: NSIDC 2016 Arctic SIE September minimum: August poll
« Reply #46 on: September 23, 2016, 03:11:30 PM »
Although it is still a few days until the SIE September minimum is announced it is save to say that most of us voted too low. Currently NSIDC Extent is at 4.58 and it can only get bigger until the end of the month. My vote was 4.25-4.5 million km2.

Interestingly for daily NSIDC sea ice area my forecast was around 150k too high. 2.55 forecast vs 2.40 observed. I already assumed a high "average extent" to "daily area" ratio of 1.6 like in 2010 and 2012, but 2016 will likely have a ratio of 2.0 or more.

Here is a list of other years "daily area" to "average extent" ratio

2007200820092010201120122013201420152016
1.461.541.521.601.591.631.481.481.47(2.00)

« Last Edit: September 24, 2016, 12:44:25 AM by Tealight »

Sleepy

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Re: NSIDC 2016 Arctic SIE September minimum: August poll
« Reply #47 on: September 24, 2016, 07:26:17 AM »
Although it is still a few days until the SIE September minimum is announced it is save to say that most of us voted too low. Currently NSIDC Extent is at 4.58 and it can only get bigger until the end of the month. My vote was 4.25-4.5 million km2.
Same here, one should have gone up two bins compared to the ADS poll but considering how this season has progressed and the state of the ice it simply felt too much, even in August.

seaicesailor

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Re: NSIDC 2016 Arctic SIE September minimum: August poll
« Reply #48 on: September 24, 2016, 09:35:09 AM »
Although it is still a few days until the SIE September minimum is announced it is save to say that most of us voted too low. Currently NSIDC Extent is at 4.58 and it can only get bigger until the end of the month. My vote was 4.25-4.5 million km2.
Same here, one should have gone up two bins compared to the ADS poll but considering how this season has progressed and the state of the ice it simply felt too much, even in August.
Will be very difficult that the NSIDC Sep extent goes above 4.5 M km2 so you were spot on.

Feeltheburn

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Re: NSIDC 2016 Arctic SIE September minimum: August poll
« Reply #49 on: September 25, 2016, 02:27:28 AM »
As of 9/23, if my adding machine input is correct, the average is 4.330 million km2.  The average is likely to stay within the range of 4.25-4.50, but possibly just exceed 4.50 by a hair.
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