Arctic Sea Ice : Forum

Cryosphere => Arctic sea ice => Topic started by: Neven on June 01, 2017, 10:39:12 PM

Title: NSIDC 2017 Arctic SIE September average: June poll
Post by: Neven on June 01, 2017, 10:39:12 PM
ATTENTION: There are two polls on the ASIF. This one is for NSIDC sea ice extent monthly/September average minimum (which is also used for the SIPN sea ice outlook), the other (http://forum.arctic-sea-ice.net/index.php/topic,2059.0.html) 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 (http://forum.arctic-sea-ice.net/index.php/topic,1837.0.html).

-----

This NSIDC extent poll will run for 11 days (until June 12th). Until then you can change your vote. There will be a new poll next month.

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

(https://lh3.googleusercontent.com/1odTcAb0nnpkiz82a0ps19PRPqhjcGu3-PcXWg61WbR2f_gBDtOk6Jsfz1EqLa3RA77VV_bPw1-TEuG-HX2zuIqvNx3QwlL_AoUbZ7Sq0_jrVu-hq-czp8QXMTF8zerffTEAi2wpVFfPu02P5Tyxcl_7tUyqxBNZefEJMaMw8TGkiWCYUN883WD5qZttMKqdEGK2MQ1agr2fmcwgJcw-LgyyNHO7__ZBPJdVxbdXHYR3723ECQXi3SIWJqQld_BRPKlva12WB8hg4wRu-r-Mis-KfC-bkLn3V_E_MqZmVAxTPv0KfpB-JFfE5Zb8iBfgco1luhVR8hQjbZe8kOHcXVz6qVzLrX6wYkf96atYqxDvztiwiqGgLWCF0c2zS3iSYLFiyBqFiu6E_JROuApOmZEtr1wJg4T_Axr8-VEJx_XYagiG_TE5qminyR9cMeQ06vpU3Iks1-ici89qM_MflYxB0DywgTIWKC31ZONttITyU1r266_gQYa8PcPn7p3OfEggeXLC6w6X01cJMbPrq2dxVqhQb-GLAbV9dgKrBIPuYGbjdOddt0vlChfMkuY5XycA3iP2Du9Wlrhz8xC9I01X8mVv-g-NiaNL4T80TcyerPn2E-QM=w1014-h546-no)

These are the September minimums for the last 12 years (in millions km2, found here (http://ftp://sidads.colorado.edu/DATASETS/NOAA/G02135/seaice_analysis/Monthly_Sea_Ice_Index_G02135_v2.1.xlsx)):

    2005: 5.59
    2006: 5.95
    2007: 4.32
    2008: 4.74
    2009: 5.39
    2010: 4.93
    2011: 4.63
    2012: 3.63
    2013: 5.35
    2014: 5.29
    2015: 4.68
    2016: 4.72

You can use the comment thread below to motivate your choice, but discuss various SIE/SIA data sets in this dedicated thread (http://forum.arctic-sea-ice.net/index.php/topic,1837.0.html).
Title: Re: NSIDC 2017 Arctic SIE September minimum: June poll
Post by: Neven on June 01, 2017, 10:43:06 PM
Because it's still so early, I'm going to wait the full 10 days before voting. Right now, I have no idea which way this could go.  :)
Title: Re: NSIDC 2017 Arctic SIE September average: June poll
Post by: seaicesailor on June 01, 2017, 11:12:18 PM
For me there a strange mix in the bag, when I commented that I am at a loss in the other thread I felt a bit ridiculous but well now I not alone in not being sure so I dont feel so bad about that anymore...
Minimum volume+early surface melt in American and pacific side+no surface melt in Laptev Kara and CAB+Bering strait and Chukchi open in record time+ high land snow cover in Russia+lots of dispersion+Barents full of ice+ MYI in the launchpad but not quite gone+ Nares making a hole in the Lincoln sea+a beaufort high that wants to stay but lows entering the Arctic with not sure what intention...
Gosh
Title: Re: NSIDC 2017 Arctic SIE September minimum: June poll
Post by: Juan C. García on June 01, 2017, 11:20:02 PM
Because it's still so early, I'm going to wait the full 10 days before voting. Right now, I have no idea which way this could go.  :)

Between 3.25 and 3.75 million km2.
A little lower than 2012. Just to vote for a new record (given the low volume that we have now) and because I know that I will not know, 10 days after today...  8)
Title: Re: NSIDC 2017 Arctic SIE September average: June poll
Post by: Neven on June 01, 2017, 11:34:27 PM
Remember, everyone, you can vote now, and then still change your vote in 10 days.

Maybe I'll vote tomorrow, just in case I forget to vote later.  ;)
Title: Re: NSIDC 2017 Arctic SIE September minimum: June poll
Post by: magnamentis on June 01, 2017, 11:50:40 PM
Because it's still so early, I'm going to wait the full 10 days before voting. Right now, I have no idea which way this could go.  :)

Between 3.25 and 3.75 million km2.
A little lower than 2012. Just to vote for a new record (given the low volume that we have now) and because I know that I will not know, 10 days after today...  8)

thanks, you made me aware that it's overlapping even though it was mentioned, great stuff ;) glad it was adopted, same ballpark like you.
Title: Re: NSIDC 2017 Arctic SIE September average: June poll
Post by: oren on June 02, 2017, 12:19:08 AM
My thinking, based on current record volume and considering most of the extra extent is in the away direction on the Atlantic side, is that we could end up in the vicinity of 2012 extent-wise, while making a new record low volume. It's all written on ice at this stage so no shame is being mistaken. 3.25-3.75, could be much higher or even somewhat lower.
Title: Re: NSIDC 2017 Arctic SIE September average: June poll
Post by: Avalonian on June 02, 2017, 01:08:01 AM
I completely agree that we simply can't predict it yet... but my gut feeling is that we're going to see an exceedingly high Poof Quotient in the later part of the season. When I look for ice that genuinely appears safe... well, I don't see a lot of it. Some of the rest will of course survive, but still... my entirely unscientific feeling is 2.5-3 at this stage. Possibly even lower.
Title: Re: NSIDC 2017 Arctic SIE September average: June poll
Post by: StopTheApocalypse on June 02, 2017, 01:10:18 AM
Regardless of what the poll shows, I think most of us probably agree that the probability of disaster this year, given the very thin ice, is high; the probability distribution is almost certainly skewed towards bad outcomes.
Title: Re: NSIDC 2017 Arctic SIE September average: June poll
Post by: icefisher on June 02, 2017, 02:49:03 AM
My swag is based on a major mid august storm sweeping in from the Pacific with a 948 minimum millibar eye.  Without a major august storm the SIE September average should be 3.75 - 4.00. Multiple storms from both Pacific and Atlantic would be a disaster.  SIE below 2.5.
Title: Re: NSIDC 2017 Arctic SIE September average: June poll
Post by: subgeometer on June 02, 2017, 05:17:45 AM
I hope I'm wrong but I've gone a bit out on a limb and plumped for 2-2.5million km2. It's really just a stab in the dark, but given the current low volume and thin dispersed ice I'd be surprised not to see a new record low, and if conditions are really conducive less than 1 million km2 can't be ruled out  - so I went for somewhere in between
Title: Re: NSIDC 2017 Arctic SIE September average: June poll
Post by: oren on June 02, 2017, 07:48:49 AM
To all low voters who might not be aware, remember this poll is for the monthly average, not for the mid-September low.
Title: Re: NSIDC 2017 Arctic SIE September average: June poll
Post by: Pmt111500 on June 02, 2017, 08:16:47 AM
It looks like I've regained the alarmist position comparing to majority on the site. Nevermind, the US prez election results show that majority doesn't always matter, as does the US decision to abandon an international treaty. I'm off to pollute so my vote has more chances to win and not punish the reputation of my votes. But I'm just a single person so my acts won't matter in the large picture, right?
Title: Re: NSIDC 2017 Arctic SIE September average: June poll
Post by: Sourabh on June 02, 2017, 08:29:49 AM
Neven,

I eagerly wait for early updates on melting seasons before voting. This year, there has not been any updates yet from your side. Are you planning to write a post anytime soon?
Title: Re: NSIDC 2017 Arctic SIE September average: June poll
Post by: DavidR on June 02, 2017, 08:54:00 AM
To all low voters who might not be aware, remember this poll is for the monthly average, not for the mid-September low.
On average this makes about 220K difference. Last year it was almost double that and in 2007 only  half. 2012 was just about average. And that's not taking into account the odd way NSIDC actually  calculate it.
Title: Re: NSIDC 2017 Arctic SIE September average: June poll
Post by: Pmt111500 on June 02, 2017, 09:36:21 AM
<clip>

 And that's not taking into account the odd way NSIDC actually  calculate it.
Oh yeah I forgot that particular piece of inaccuracy. Gotta move my vote one notch up.
Title: Re: NSIDC 2017 Arctic SIE September average: June poll
Post by: Neven on June 02, 2017, 10:00:20 AM
Neven,

I eagerly wait for early updates on melting seasons before voting. This year, there has not been any updates yet from your side. Are you planning to write a post anytime soon?

Sourabh, I've taken a break from blogging (http://neven1.typepad.com/blog/2016/11/sabbatical-i-wish.html) this year (except for posting monthly PIOMAS updates), so you'll have to glean the info from the 2017 melting season thread, and other corners of the Forum.
Title: Re: NSIDC 2017 Arctic SIE September average: June poll
Post by: Richard Rathbone on June 02, 2017, 01:06:21 PM
Too early to do anything but extrapolate the trend. Figure 3 in http://nsidc.org/arcticseaicenews/2016/10/rapid-ice-growth-follows-the-seasonal-minimum-rapid-drop-in-antarctic-extent/ (http://nsidc.org/arcticseaicenews/2016/10/rapid-ice-growth-follows-the-seasonal-minimum-rapid-drop-in-antarctic-extent/)

Since last year was almost exactly on the trend, that makes it 4.5 in round numbers for this year.
Title: Re: NSIDC 2017 Arctic SIE September average: June poll
Post by: Paddy on June 02, 2017, 09:20:46 PM
Gone with "same as the lowest we've had" [3.5 to 4.0], like on the other poll. But it really is way too early to tell.

EDIT: Moved down one bar on each poll having seen some of the analyses on here.
Title: Re: NSIDC 2017 Arctic SIE September average: June poll
Post by: RikW on June 06, 2017, 09:45:18 AM
I've got a bad gut feeling about this melting season. And though Extent numbers don't drop very fast currently, World View pictures doesn't look good. I fear we will be in for a bad surprise but based on the numbers that feeling can't be logically true yet. So I just go for the 2012 record :)
Title: Re: NSIDC 2017 Arctic SIE September average: June poll
Post by: Sterks on June 06, 2017, 02:24:54 PM
Being consistent with my volume prediction, and with the belief bathymetry imposes hard limit to the minimum extent, I vote on a record or near record value: 3.25 - 3.75 m km2.
Title: Re: NSIDC 2017 Arctic SIE September average: June poll
Post by: Archimid on June 08, 2017, 12:12:19 AM
I voted with the pack. Right now is so hard to tell anything.
Title: Re: NSIDC 2017 Arctic SIE September average: June poll
Post by: Chuck Yokota on June 08, 2017, 03:35:07 AM
I voted 2.25-2.75 million because I think volume will be driving extent this year.  1000 km3 = 1 million km2 x 1 meter thick.
Title: Re: NSIDC 2017 Arctic SIE September average: June poll
Post by: Rob Dekker on June 08, 2017, 06:14:19 AM
I'm going out on a limb here, but I just entered my vote as 5.4.

Reason is mostly the massive land snow anomaly that was reported for May :
http://climate.rutgers.edu/snowcover/chart_anom.php?ui_set=1&ui_region=nhland&ui_month=5 (http://climate.rutgers.edu/snowcover/chart_anom.php?ui_set=1&ui_region=nhland&ui_month=5)
(https://diablobanquisa.files.wordpress.com/2017/06/may.png)

In my regression formula, that snow anomaly, combined with the moderate ice area/concentration numbers, results in 5.4 M km^2 (NSIDC) extent left over in September.

Now, I don't put much confidence in this prediction, for various reasons :

1) May is early to make predictions, and the standard deviation of my prediction is 460 k km^2, which is only moderately better than a simple linear trend (SD 550 k km^2). In other words, the prediction does not have much 'skill'. June should be a lot better.

2) 2017 is so far running at record low volume numbers (by PIOMAS) due to the warm winter. Quick calculations suggest that First Year Ice is some 10% thinner than in prior years. Once melting starts seriously, this should accelerate the decline in SIE, and even with average volume melt could easily lead to record low volume (and SIE) numbers this year.

3) Snow melts quickly, so this May anomaly may not last long. If it disappears in June, then point 2) may take over and we may see some serious cliff in July.

But overall, I am optimistic that this land snow anomaly will at least slow down the decline of SIE this melting season, and if the anomaly sustains over June, then 5.4 M km^2 is not unrealistic.
Title: Re: NSIDC 2017 Arctic SIE September average: June poll
Post by: johnm33 on June 08, 2017, 11:23:51 AM
I went for 2-2.5 the ice looks smashed so as things warm a little more I expect rain and lots of it. With the ice as it is I suspect widespread distribution of salt, from flash frozen spray, to accelerate melt, and to greatly increase surface area until meltponds form. With things as they are in Lincoln and CAA I anticipate tidally driven export becoming a serious factor too.
Title: Re: NSIDC 2017 Arctic SIE September average: June poll
Post by: Nightvid Cole on June 08, 2017, 08:16:23 PM
I went higher this year, I think it will not go below 4.5 M. This is because I looked at NASA worldview and right now the Arctic is whiter than any other recent year at this time, even 2013 and 2014. This indicates very little melt ponding and the great majority of the sun's rays hitting the Arctic are bumped back out to space.
Title: Re: NSIDC 2017 Arctic SIE September average: June poll
Post by: magnamentis on June 08, 2017, 08:25:06 PM
I went higher this year, I think it will not go below 4.5 M. This is because I looked at NASA worldview and right now the Arctic is whiter than any other recent year at this time, even 2013 and 2014. This indicates very little melt ponding and the great majority of the sun's rays hitting the Arctic are bumped back out to space.

your opinion is all yours but please stick to facts, even with all the fragmentation extent is around 4th lowest and volume is lowest. sound a bit like either playing advocatus diaboli or going for the opposite as a win-win statement, if wrong, no-one is surprised and if right one's the guy.

the ice is in the worst state ever, this is the fact and images do not always tell the entire truth nowadays. a bit more or less contrast and all looks totally different, many enough examples
floating around here.
Title: Re: NSIDC 2017 Arctic SIE September average: June poll
Post by: Rob Dekker on June 09, 2017, 03:57:05 AM
I went higher this year, I think it will not go below 4.5 M. This is because I looked at NASA worldview and right now the Arctic is whiter than any other recent year at this time, even 2013 and 2014. This indicates very little melt ponding and the great majority of the sun's rays hitting the Arctic are bumped back out to space.

I tend to agree.
Compare this year's pan-Arctic picture :
https://lance3.modaps.eosdis.nasa.gov/imagery/subsets/?mosaic=Arctic.2017157.terra.4km
where there is pristine white ice and snow covered land all along the Siberian coastline,
with the picture from the same date last year :
https://lance3.modaps.eosdis.nasa.gov/imagery/subsets/?mosaic=Arctic.2016157.terra.4km
where a snow-free Siberia and blue ice suggest that melting was in full swing all along Siberia.

That May snow anomaly certainly has a significant effect, suggesting that there are fewer melting ponds, especially along the Siberian coast, than last year.

And last year ended up at 4.7.
Title: Re: NSIDC 2017 Arctic SIE September average: June poll
Post by: magnamentis on June 09, 2017, 11:38:53 PM
I went higher this year, I think it will not go below 4.5 M. This is because I looked at NASA worldview and right now the Arctic is whiter than any other recent year at this time, even 2013 and 2014. This indicates very little melt ponding and the great majority of the sun's rays hitting the Arctic are bumped back out to space.

I tend to agree.
Compare this year's pan-Arctic picture :
https://lance3.modaps.eosdis.nasa.gov/imagery/subsets/?mosaic=Arctic.2017157.terra.4km
where there is pristine white ice and snow covered land all along the Siberian coastline,
with the picture from the same date last year :
https://lance3.modaps.eosdis.nasa.gov/imagery/subsets/?mosaic=Arctic.2016157.terra.4km
where a snow-free Siberia and blue ice suggest that melting was in full swing all along Siberia.

That May snow anomaly certainly has a significant effect, suggesting that there are fewer melting ponds, especially along the Siberian coast, than last year.

And last year ended up at 4.7.

you mentioned the key word that is mostly responsible for the "visual" errors in assessments

"SNOWCOVER"

that snow cover spoils the view and once gone the effect you mentioned will be pulverized.

also snowcover is exactly what i had in mind when i said that images don't show the entire truth,
just think about glaciers and their snow covered fissures and crevasse. looks all homogeneous from the air but beware from believing it and go for a careless walk LOL
Title: Re: NSIDC 2017 Arctic SIE September average: June poll
Post by: Tealight on June 10, 2017, 12:51:09 AM
@Rob

Maybe you can develop a new or modified formula which includes PIOMAS volume. It is definitely a useful metric to describe the state of the sea ice .


My model prediction is 4.1 million km2, but I have an interdecile range of 3.2 - 5.1. The high snow cover slows down melt in my model as well, but due to the record low sea ice volume it still predicts a second place with a slight chance of a new record low.

If my model is correct then there is a 10% change we get below 3.2 million and 10% change above 5.1 million.

For the daily sea ice area minimum I get 2.513 million km2
Range:   1.964 - 3.112


Title: Re: NSIDC 2017 Arctic SIE September average: June poll
Post by: Rob Dekker on June 10, 2017, 08:40:34 AM
@Rob

Maybe you can develop a new or modified formula which includes PIOMAS volume. It is definitely a useful metric to describe the state of the sea ice .
Yes. I have some ideas for that, but did not have the time to validate them.

Quote
My model prediction is 4.1 million km2, but I have an interdecile range of 3.2 - 5.1. The high snow cover slows down melt in my model as well, but due to the record low sea ice volume it still predicts a second place with a slight chance of a new record low.

If my model is correct then there is a 10% change we get below 3.2 million and 10% change above 5.1 million.

These numbers suggest that the standard deviation over the residuals in your method are about 550-600 k km^2. Is that correct ?
If so, your method has little 'skill', since a simple linear trend has 550 k km^2 SD.
With 460 k km^2 SD, my method has little 'skill' too, and neither do most of SIPN projections.

Maybe May is just too early for skillful predictions of September SIE.
Title: Re: NSIDC 2017 Arctic SIE September average: June poll
Post by: seaicesailor on June 10, 2017, 11:06:03 AM
I voted 3.5-4.0 M km2.
This is the first June in years that goes so clearly anticyclonic, and while the HP has been pulling air from the continent with the cold anomaly and not many melt ponds are really visible, it still has brought over zero temps to a significant portion of the Arctic (snow melting, ice warming up, bottom melting soon to kick up). This situation will be sustained for days.

Also, significant portion of the Pacific side is open water, and there is plenty of insolation.

The land snow cover has so clearly delayed melt in ESS and Laptev, and I guess all the warmth coming from Eurasia will lack some punch during the summer. That is a very important factor.

Still let's see what happens with all that ice thinner in average as never before, with the thicker MYI sitting too close to the Atlantic Ocean.

By the way, the NSIDC now computes the monthly average as the average of daily extents. This would have yielded around 4.3 M km2 in 2016.
Title: Re: NSIDC 2017 Arctic SIE September average: June poll
Post by: Richard Rathbone on June 10, 2017, 12:46:43 PM


By the way, the NSIDC now computes the monthly average as the average of daily extents. This would have yielded around 4.3 M km2 in 2016.


Thats not what their documentation says.

http://nsidc.org/data/docs/noaa/g02135_seaice_index/#jan-2017 (http://nsidc.org/data/docs/noaa/g02135_seaice_index/#jan-2017) says they made a change to how they calculated the monthly figure, but they still take an average concentration for the month and calculate the extent from that, not from the daily extents. Its also clear elsewhere in that document that they calculate extents from average concentrations for both the daily and the monthly extents.

There was a rumor I saw somewhere on the forum or blog that it had happened, but I think someone misunderstood what the change in January was.

Title: Re: NSIDC 2017 Arctic SIE September average: June poll
Post by: seaicesailor on June 10, 2017, 12:55:06 PM
Alright, thanks for the correction, I was one of the deluded then.
Title: Re: NSIDC 2017 Arctic SIE September average: June poll
Post by: Steven on June 10, 2017, 02:34:23 PM
I voted for 4.0-4.5 million km2.

This is based on multiple linear regression with the following two predictor variables:


I used data for the last 20 years.  The regression gives an estimate of 4.27 +/- 0.9 million km2  (95% prediction interval)  for the September 2017 NSIDC extent.
Title: Re: NSIDC 2017 Arctic SIE September average: June poll
Post by: magnamentis on June 10, 2017, 07:37:36 PM
I voted for 4.0-4.5 million km2.

This is based on multiple linear regression with the following two predictor variables:

  • PIOMAS volume at the end of May
  • sea ice area on 8 June as calculated by Wipneus (https://sites.google.com/site/arctischepinguin/home/sea-ice-extent-area/data) from gridded NSIDC sea ice concentration data

I used data for the last 20 years.  The regression gives an estimate of 4.27 +/- 0.9 million km2  (95% prediction interval)  for the September 2017 NSIDC extent.

whenever something extraordinary happend and/or will happen data and patterns from the past will not have helped but will give the uninitiated a feeling of safety.

things are different and so will be the outcome while this most not be the outcome of extent.
last year things were different and the outcome was different, but mostly the winter climate as well as the ice volume was affected.

however, there was a huge reduction in ace over all which did not really show well in extent minimum but sooner or later, the ever reduced volume as well as genereal "quality" of the remaining ice will show in extent numbers and since it will happen once that the 15% threshold will be passed ist will be a sudden drop, something like an ASID ( abrupt sea ice drop ) LOL
Title: Re: NSIDC 2017 Arctic SIE September average: June poll
Post by: Neven on June 10, 2017, 11:53:03 PM
For now I have voted 'Between 4.0 and 4.5 million km2'. I'll be sure to vote lower next month if I see a couple of parameters move that way (SSTs, ice pack turning blue, PIOMAS, and of course, SIE measures themselves).
Title: Re: NSIDC 2017 Arctic SIE September average: June poll
Post by: Rob Dekker on June 11, 2017, 04:38:22 AM
I voted for 4.0-4.5 million km2.

This is based on multiple linear regression with the following two predictor variables:

  • PIOMAS volume at the end of May
  • sea ice area on 8 June as calculated by Wipneus (https://sites.google.com/site/arctischepinguin/home/sea-ice-extent-area/data) from gridded NSIDC sea ice concentration data

I used data for the last 20 years.  The regression gives an estimate of 4.27 +/- 0.9 million km2  (95% prediction interval)  for the September 2017 NSIDC extent.

Steven, your method suggests a SD of 450 k km^2, which is really good for a May -> September projection.

Did you consider entering in SIPN ? Entries are still open until Monday 6pm :
https://www.arcus.org/sipn/sea-ice-outlook/2017/june/call (https://www.arcus.org/sipn/sea-ice-outlook/2017/june/call)
https://goo.gl/forms/kKSpPgjyD9B4I1IC3 (https://goo.gl/forms/kKSpPgjyD9B4I1IC3)
Title: Re: NSIDC 2017 Arctic SIE September average: June poll
Post by: Thomas Barlow on June 11, 2017, 04:46:27 AM
I chose between 3.0 and 3.5 million because I think the volume in Arctic Ocean is record low, and could crash (leaving  peripheral areas to make up the damage a bit).
Title: Re: NSIDC 2017 Arctic SIE September average: June poll
Post by: Tealight on June 11, 2017, 11:15:21 AM
These numbers suggest that the standard deviation over the residuals in your method are about 550-600 k km^2. Is that correct ?
If so, your method has little 'skill', since a simple linear trend has 550 k km^2 SD.
With 460 k km^2 SD, my method has little 'skill' too, and neither do most of SIPN projections.

Maybe May is just too early for skillful predictions of September SIE.

I never really calculated the standard deviation for extent. My model is albedo based and it can only calculate how much ice melts, but not how it is distributed over the month of September. The conversion from my area numbers into extent is more of a guessing game.

What I found out is that the compaction ratio alone influences the NSIDC September extent at least as much as the remaining melt conditions.

Normal variation for me due to compaction ratio is +-200k, but last year was extreme with +900k. Because of the very mobile ice pack I increased my forecast range this year to hopefully catch the final NSIDC extent number.
Title: Re: NSIDC 2017 Arctic SIE September average: June poll
Post by: Albatross on June 11, 2017, 06:43:25 PM
Long time lurker...finally made my first post and voted for a minimum between 3.5 to 4.0 mil km2. Albatross from SkS.
Title: Re: NSIDC 2017 Arctic SIE September average: June poll
Post by: Neven on June 11, 2017, 06:48:36 PM
Welcome to the ASIF, Albatross. I've released your profile. And thanks for voting.
Title: Re: NSIDC 2017 Arctic SIE September average: June poll
Post by: Steven on June 11, 2017, 08:37:04 PM
Steven, your method suggests a SD of 450 k km^2, which is really good for a May -> September projection.

Did you consider entering in SIPN ? Entries are still open until Monday 6pm :
https://www.arcus.org/sipn/sea-ice-outlook/2017/june/call (https://www.arcus.org/sipn/sea-ice-outlook/2017/june/call)
https://goo.gl/forms/kKSpPgjyD9B4I1IC3 (https://goo.gl/forms/kKSpPgjyD9B4I1IC3)

Rob, I wasn't intending to submit this to the SIPN.  The method I used isn't really new, since I'm obviously not the first one who uses sea ice volume and/or area at this time of year to predict the September minimum extent.

The method I used performs better than a simple linear trend of September extent.  But there are certainly better methods.  E.g., Schroeder et al. (http://www.homepages.ed.ac.uk/shs/Climatechange/Arctic%20ice/melt%20pond%20ice%20forecast.pdf)'s method based on modeled May melt ponds has a better forecast skill than mine.  But apparently their forecasts tend to be somewhat too high in recent years.
Title: Re: NSIDC 2017 Arctic SIE September average: June poll
Post by: CameraMan on June 12, 2017, 01:16:53 AM

The land snow cover has so clearly delayed melt in ESS and Laptev, and I guess all the warmth coming from Eurasia will lack some punch during the summer. That is a very important factor.

Agreed, but delay is not avoidance.   ESS and Kara look to take a hit this week, and given how thin much of the ice is, I'm thinking much will melt out by Sept, even with a late start.   Extent hasn't shown the drops yet, but more "ice" is becoming rubble and slush.

So I'm also guessing 3.5 - 4   Hoping that I'm wrong and more survives.
Title: Re: NSIDC 2017 Arctic SIE September average: June poll
Post by: Yuha on June 12, 2017, 03:32:40 AM
4.0 - 4.5 as half way between 2012 and 2016.
Title: Re: NSIDC 2017 Arctic SIE September average: June poll
Post by: Rob Dekker on June 12, 2017, 07:56:38 AM
Rob, I wasn't intending to submit this to the SIPN.  The method I used isn't really new, since I'm obviously not the first one who uses sea ice volume and/or area at this time of year to predict the September minimum extent.

The method I used performs better than a simple linear trend of September extent.  But there are certainly better methods.  E.g., Schroeder et al. (http://www.homepages.ed.ac.uk/shs/Climatechange/Arctic%20ice/melt%20pond%20ice%20forecast.pdf)'s method based on modeled May melt ponds has a better forecast skill than mine.  But apparently their forecasts tend to be somewhat too high in recent years.

Schroeder's May melt pond method has a SD of 500 k km^2 :
https://www.arcus.org/files/sio/25659/sio-2016-june_cpom_schroeder-feltham-flocco-tsamados.pdf (https://www.arcus.org/files/sio/25659/sio-2016-june_cpom_schroeder-feltham-flocco-tsamados.pdf)

Your method is better than that, and thus I would encourage you to enter in SIPN.
Title: Re: NSIDC 2017 Arctic SIE September average: June poll
Post by: greatdying2 on June 12, 2017, 10:09:37 AM
3 to 3.5: With so much thin ice there is a very good chance that this year will blow right past the previous record.
Title: Re: NSIDC 2017 Arctic SIE September average: June poll
Post by: DavidR on June 12, 2017, 10:12:55 AM
Rob, I wasn't intending to submit this to the SIPN.  The method I used isn't really new, since I'm obviously not the first one who uses sea ice volume and/or area at this time of year to predict the September minimum extent.

The method I used performs better than a simple linear trend of September extent.  But there are certainly better methods.  E.g., Schroeder et al. (http://www.homepages.ed.ac.uk/shs/Climatechange/Arctic%20ice/melt%20pond%20ice%20forecast.pdf)'s method based on modeled May melt ponds has a better forecast skill than mine.  But apparently their forecasts tend to be somewhat too high in recent years.

Schroeder's May melt pond method has a SD of 500 k km^2 :
https://www.arcus.org/files/sio/25659/sio-2016-june_cpom_schroeder-feltham-flocco-tsamados.pdf (https://www.arcus.org/files/sio/25659/sio-2016-june_cpom_schroeder-feltham-flocco-tsamados.pdf)

Your method is better than that, and thus I would encourage you to enter in SIPN.
I agree, submitting your estimates to  SIPN encourages you to think through and quantify your thoughts and to go back and review them later to look for the reasons you were wrong.  I  would say a standard deviation of 500K is about average for both the amateurs and the professionals.  There really are far to many unknown variables in play this early in the year to get  much  closer.
Title: Re: NSIDC 2017 Arctic SIE September average: June poll
Post by: N00bi-Wan on June 12, 2017, 12:31:47 PM
Voted for 3.25 - 3.75, mostly based on Jim Pettit's volume projections (http://forum.arctic-sea-ice.net/index.php/topic,119.msg115901.html#msg115901).

Volume is unprecedentedly low, but moreover the severe deficit in FDD during the freezing season altered the quality of sea ice. It's more vulnerable than ever.

My intuition thus is that, even more than in 2016, bottom melt will be the real killer this melting season.

A record or near record NSDIC September SIE seems then in order.
Title: Re: NSIDC 2017 Arctic SIE September average: June poll
Post by: gerontocrat on June 12, 2017, 02:37:50 PM
In the total certainty that I shall be shot down in flames I am going for 4.2 million km2. Pourquoi ?
The June cliff, like the British summer, is being promised a few days down the line but keeps on not happening. So I have ignored the extraordinary melt from now to minimum that occurred in 2007 and 2012. So for 2017,I end up with a fairly ordinary melting season, but does reflect that the rate of melt is increasing over the years.

However, herewith a quick and crude "reductio ad absurdum".
NSIDC says that September extent has reduced by about 13 percent per decade. PIOMAS reckon September volume has decreased by about 20 percent per decade.

What if this continued for 50 years from 1979?
Volume at zero.
Extent still at 35 % of 1979.
Absurd.

At some point something has gotta give. I just don't think it is this year.

Title: Re: NSIDC 2017 Arctic SIE September average: June poll
Post by: epiphyte on June 12, 2017, 05:22:44 PM
3-3.5M sq.km for me, for what it's worth, with my oft-repeated caveat that if and when it goes, it will all go at once. So I don't really have much confidence in my own prediction - it's mid-way between two extremes, but that doesn't make it more likely - It's like predicting a draw in a game of Russian roulette.

It could have happened last year (IMO we missed by about two weeks), and it could definitely still happen this year. If it does then Sep extent will be shockingly low - likely <3M. If it doesn't, then we pulled the trigger on an empty chamber, again, and the Sep extent could be much higher. 

Laptev, for example, looks to me to be in the process of being 'bitten' despite all the snow to the south, the only sub-freezing surface temps in the whole Arctic, and the apparently high-albedo surface.

I'm considering also that most of the peripheral extent, especially in Laptev & ESS, is very new (i.e. grew from open water during (an unusually mild) March and April, to fill the void left by the MYI exiting the Fram). The normal early-springtime offshore-onshore oscillation which accelerates ridging, and hence volume build-up, early in the year seems to me to have been replaced with continuous dispersal, fragmentation and a relentless march North. Add in the insulating and albedo-raising effect of early snowfall and, models notwithstanding, we could be looking at >1m km2 of tissue-thin ice which could vanish in literally hours.

So um. yes.
Title: Re: NSIDC 2017 Arctic SIE September average: June poll
Post by: Yuha on June 12, 2017, 08:04:02 PM
4.0 - 4.5 as half way between 2012 and 2016.

Decided at last minute to drop down one bucket to 3.75 - 4.25 which too contains the halfway point. The change of mind was based on seeing some darkened ice in Worldview (north of Chukchi Sea) and Wipneus' latest PIOMAS analysis.
Title: Re: NSIDC 2017 Arctic SIE September average: June poll
Post by: Steven on June 12, 2017, 10:41:29 PM
Rob, I wasn't intending to submit this to the SIPN.  The method I used isn't really new, since I'm obviously not the first one who uses sea ice volume and/or area at this time of year to predict the September minimum extent.

The method I used performs better than a simple linear trend of September extent.  But there are certainly better methods.  E.g., Schroeder et al. (http://www.homepages.ed.ac.uk/shs/Climatechange/Arctic%20ice/melt%20pond%20ice%20forecast.pdf)'s method based on modeled May melt ponds has a better forecast skill than mine.  But apparently their forecasts tend to be somewhat too high in recent years.
Schroeder's May melt pond method has a SD of 500 k km^2 :
https://www.arcus.org/files/sio/25659/sio-2016-june_cpom_schroeder-feltham-flocco-tsamados.pdf (https://www.arcus.org/files/sio/25659/sio-2016-june_cpom_schroeder-feltham-flocco-tsamados.pdf)

Your method is better than that, and thus I would encourage you to enter in SIPN.

Are you comparing hindcasts or forecasts?

Schroeder et al.'s method has a standard deviation of 330 k km2 for the residuals of the hindcasts, and it has a forecast error for the last few decades* of about 500 k km2.

For comparison, the method I used has a standard deviation of 440 k km2 for the hindcasts, whereas the forecast error of my method for the last few decades would probably be somewhere between 500 and 550 k km2 or so.  That is worse than Schroeder's.

A similar remark applies to your method as well.  You have a SD of 460 k km2 for the residuals of the hindcasts.  But the forecast error of your method for the last few decades is certainly higher than that (probably in the same ballpark as for my method).


*: To calculate the "forecast" that the method would have produced for the year 2009 (say), only data up to 2008 should be used to calculate the coefficients of the regression equation.  In contrast, the hindcast for 2009 is calculated from data for the entire period 1979-2016.
Title: Re: NSIDC 2017 Arctic SIE September average: June poll
Post by: Neven on June 12, 2017, 11:41:56 PM
The poll has closed. 134 votes in total, which is pretty great (thanks, everyone). When I find the time I'll post the average and the median (if I remember how to do it, and hopefully the overlapping bins don't make this more complicated  ;) ).
Title: Re: NSIDC 2017 Arctic SIE September average: June poll
Post by: Rob Dekker on June 13, 2017, 06:57:16 AM
Are you comparing hindcasts or forecasts?

Schroeder et al.'s method has a standard deviation of 330 k km2 for the residuals of the hindcasts, and it has a forecast error for the last few decades* of about 500 k km2.

For comparison, the method I used has a standard deviation of 440 k km2 for the hindcasts, whereas the forecast error of my method for the last few decades would probably be somewhere between 500 and 550 k km2 or so.  That is worse than Schroeder's.

A similar remark applies to your method as well.  You have a SD of 460 k km2 for the residuals of the hindcasts.  But the forecast error of your method for the last few decades is certainly higher than that (probably in the same ballpark as for my method).

*: To calculate the "forecast" that the method would have produced for the year 2009 (say), only data up to 2008 should be used to calculate the coefficients of the regression equation.  In contrast, the hindcast for 2009 is calculated from data for the entire period 1979-2016.

I'm comparing 'forecast' methods.
That is : methods that include ONLY data that is available before the prediction is made.
For May predictions of September SIE, that should include only data that is available in May of that year. In other words, for real 'forecast' methods, you cannot use data available only in June-September.

There, Schroeder's method (in forecast mode) has a SD of the residuals of 500 k km^2.
My method (implicitly a forecast method) has a SD of the residuals of 460 k km^2.

For your method, I'm not sure now.
When you mentioned 900 k km^2 for the 95% confidence range (2 SD), did you include data from the summer (June->Sept) for the years in the learning period in your linear regression ?

To be clear : 'hindcasts' as defined in Schroeder's method can only be calculated for past years, NOT for the current year, since they include data from June->September. 'hindcasts' are useful to determine how much of natural variability over the summer is captured by your variables, but of course it is useless for true predictions for a new year. As Schroeder himself puts it :

Quote
The low error values in the hindcast of September ice extent
do not guarantee that pond fraction can be used for real forecasts
of Arctic September sea ice, because for a forecast only data of
previous years are available to calculate the weights and linear
regression
Title: Re: NSIDC 2017 Arctic SIE September average: June poll
Post by: Rob Dekker on June 13, 2017, 07:15:59 AM
Thanks for organizing this poll, Neven !
Seems that the majority of votes is between 3.0 and 4.5 this year.
But the spread is quite extensive.
May is still early for predictions, and I'm looking forward to the July poll, based on June data, which tends to be a lot more accurate.
Title: Re: NSIDC 2017 Arctic SIE September average: June poll
Post by: Steven on June 13, 2017, 06:22:46 PM
There, Schroeder's method (in forecast mode) has a SD of the residuals of 500 k km^2.
My method (implicitly a forecast method) has a SD of the residuals of 460 k km^2.

That is an unfair comparison.  You are overselling your model.

I looked at your model a few years ago, and I'm pretty sure that 460k km2 is the standard deviation of the residuals for the hindcasts (rather than forecasts) of your model.

For example, what is the forecast that your model would have produced for the year 2014?  The actual forecast that you made back then is 4.6 M km2 (link (https://www.arcus.org/files/search/sea-ice-outlook/pdf/dekker.pdf)).  But I suspect that you are currently using a different "forecast" value for the year 2014 when you are calculating your standard deviation.

Another example: for a simple linear fit of September extent over 1979-2016, the standard deviation of residuals is about 550 k km2 for hindcasts, but almost 600 k km2 in forecast mode.

Regarding my method, the 2*SD = 900 k km2 number that I mentioned on Saturday was just a quick estimate from the hindcasts.  It's much more work to calculate this for the actual forecasts that the method would have produced, since then the coefficients of the regression equation have to be re-calculated for each individual year.  Anyway, I did that calculation yesterday, and it would give about 2*SD = 1.04 M km2.
Title: Re: NSIDC 2017 Arctic SIE September average: June poll
Post by: Rob Dekker on June 14, 2017, 05:05:23 AM
Steven, thank you !

I always thought that a 'hindcast' included data (past performance) between the moment the prediction was made (May in this case) to the moment of prediction (September in this case).
But in reading your response, and re-reading Schroeder's paper, I realized I was mistaken.
Schroeder writes :
Quote
To investigate the potential of pond fraction as a predictor for
Arctic September sea ice, we first used the whole data period
to derive the linear regression between spring pond fraction and
September ice extent and applied the regression line to calculate
September ice extent from spring pond fraction (hindcast mode).
And that is exactly what I did (with snow cover rather than pond fraction).

So indeed my method is called a 'hindcast' under that definition. I learned something today  :)

Couple of thoughts :
- The (hindcast) 330 k SD that Schroeder obtains with May data is impressive. I obtain that SD (using snow cover) only with June data.

- I'm also impressed that you obtain (hindcast) SD 450 k km^2 with your method using May data of just PIOMAS volume and ice 'area' as variables. If you have a chance, could you explain your method in more detail (like, what exactly is your regression formula, and how did you determine the weight factors for each variable).

- I'm now confused about Schroeder's 'forecast' method. Seems to me that if you re-calculate the regression parameters for every year (using the years before that) that you will get serious 'over-fitting' for the first couple of years, then in the middle you don't have enough data points, and at the end of the time series you match the results of the 'hindcast' method. I don't see how the SD of residuals of such a strange method tells anything useful.
Title: Re: NSIDC 2017 Arctic SIE September average: June poll
Post by: Steven on June 14, 2017, 07:31:54 PM
The (hindcast) 330 k SD that Schroeder obtains with May data is impressive.

Yes, but Schroeder's model has lots of parameters.  That makes it easier to obtain good hindcasts.  Hindcasts aren't very informative when there are lots of predictor variables:  a low hindcast error in such a case could be simply due to overfitting.  That is the reason why Schroeder only runs his model in forecast mode when he discusses the skill of the model.

Regarding my model: I used two predictor variables (volume and area).  There are built-in software packages in R and in Excel to perform multiple linear regression.  This automatically computes the optimal coefficients of the regression equation.  The raw (unadjusted) SD of the hindcast residuals for my method is 420 k km2.  But I preferred to make an adjustment, to account for the fact that I'm using multiple predictors.  The adjusted hindcast residual SD is 450 k km2.  The adjustment was obtained from using the adjusted R squared (http://www.statisticshowto.com/adjusted-r2/) of the multiple linear regression.

Regarding the calculation of forecasts: to simulate the forecast for the year 1989 (say), only 10 years of data would be available: 1979-1988.  I think that is too few.  In fact, I prefer to have at least 20 years of data available for each forecast.  For that reason I only simulated forecasts from 1999 onwards  (using 1979-1998 data for the 1999 forecast,  1979-1999 data for the 2000 forecast, and so on).  Doing that for each year between 1999 and 2016, I get a forecast error SD of 520k km2 for my method.
Title: Re: NSIDC 2017 Arctic SIE September average: June poll
Post by: Rob Dekker on June 16, 2017, 07:22:59 AM
The (hindcast) 330 k SD that Schroeder obtains with May data is impressive.

Yes, but Schroeder's model has lots of parameters.  That makes it easier to obtain good hindcasts.  Hindcasts aren't very informative when there are lots of predictor variables:  a low hindcast error in such a case could be simply due to overfitting.  That is the reason why Schroeder only runs his model in forecast mode when he discusses the skill of the model.

I thought that Schroeder's model had only one parameter : "pond fraction".
Title: Re: NSIDC 2017 Arctic SIE September average: June poll
Post by: Rob Dekker on June 16, 2017, 07:37:09 AM
Incidentally, here is another paper (with Schroeder on the author list)
http://onlinelibrary.wiley.com/doi/10.1002/2016EF000495/pdf (http://onlinelibrary.wiley.com/doi/10.1002/2016EF000495/pdf)

which claims that Sea Ice Concentration (SIC) has equal or better skill than the simulated "pond fraction" from Schroeder's original paper.

This (using SIC to determine melt potential) is very similar to the great work by Tealight (Nico Sun) :
https://sites.google.com/site/cryospherecomputing/daily-data (https://sites.google.com/site/cryospherecomputing/daily-data)

Also interesting is the skill of Melting Onset (MO) metric by Julienne Stroeve, especially for early predictions (March to May) of September Sea Ice.
Title: Re: NSIDC 2017 Arctic SIE September average: June poll
Post by: Steven on June 16, 2017, 07:33:53 PM
I thought that Schroeder's model had only one parameter : "pond fraction".

Not really.  Schroeder et al. use gridded data, and they "calculate weights for each grid point based on the correlation coefficient between the local pond area and the Arctic September ice extent ".  See also this comment by Michael Hauber a few years ago:

http://forum.arctic-sea-ice.net/index.php/topic,902.msg28775.html#msg28775 (http://forum.arctic-sea-ice.net/index.php/topic,902.msg28775.html#msg28775)
Title: Re: NSIDC 2017 Arctic SIE September average: June poll
Post by: Steven on July 01, 2017, 09:09:24 AM
The SIPN June 2017 report is out:

https://www.arcus.org/sipn/sea-ice-outlook/2017/june (https://www.arcus.org/sipn/sea-ice-outlook/2017/june)

Quote
The median Outlook value for September 2017 sea ice extent is 4.43 million square kilometers with quartiles of 4.10 and 4.71 million square kilometers (See Figure 1 in the Overview section, below). Contributions are based on a range of methods: statistical, dynamical models, heuristic, and two informal polls.
...
To place this year's Outlook in context, consider recent observed values of 4.28 million square kilometers in 2007, 3.60 million square kilometers in 2012, and 4.72 million square kilometers in 2016. Only one participant suggests a new record low is likely, though several others suggest it is possible.


(https://www.arcus.org/files/resize/sio/27252/sio2017_june_fig1_n33-700x509.png)

(https://www.arcus.org/files/resize/sio/27252/sio2017_june_fig2_box_n33-700x509.png)
Title: Re: NSIDC 2017 Arctic SIE September average: June poll
Post by: Darvince on July 01, 2017, 12:49:14 PM
The statistical models have clustered higher than the dynamical models...

How many of each take into account sea ice thickness?
Title: Re: NSIDC 2017 Arctic SIE September average: June poll
Post by: Steven on July 02, 2017, 04:44:11 PM
The statistical models have clustered higher than the dynamical models...

How many of each take into account sea ice thickness?

Dynamical models should model sea ice thickness in one way or another.  Some of them use PIOMAS or CryoSat for initial conditions, but most of them seem to use their own model for that.

Regarding the statistical models, only a few of them use thickness data.  There are other predictors (e.g. sea ice concentration, melt pond area, SSTs etc) that are also important.
Title: Re: NSIDC 2017 Arctic SIE September average: June poll
Post by: EgalSust on July 13, 2017, 08:44:12 PM
The forum median prediction was between 3.25 and 3.75 Mkm². That would mean second lowest or record low extent. Compared to SIPN/SIO predictions, this sits at the alarmist end of the spectrum.