Arctic Sea Ice : Forum

Cryosphere => Arctic sea ice => Topic started by: Wipneus on March 12, 2013, 05:07:20 PM

Title: Latest PIOMAS update (December update)
Post by: Wipneus on March 12, 2013, 05:07:20 PM
Hello, PIOMAS has updated:
Latest value: 2013-3-1 19.945
Latest value: 2013-3-31 21.612
Latest value: 2013-4-30 21.273
Latest value: 2013-5-31 19.087
Latest value: 2013-6-30 13.002
Latest value: 2013-7-31 7.104
Latest value: 2013-8-31 5.077
Latest value: 2013-9-30 5.343
Latest value: 2013-10-31 8.218
Latest value: 2013-11-30 11.449
Latest value: 2013-12-31 15.225
Latest value: 2014-1-31 18.938  <- version 2.1 !
Latest value: 2014-2-28 20.86
Latest value: 2014-3-31 22.609
Latest value: 2014-4-30 22.94
Latest value: 2014-5-31 20.288
Latest value: 2014-6-30 14.632
Latest value: 2014-7-31 9.575
Latest value: 2014-8-31 7.22
Latest value: 2014-9-30 7.119 (minimum 2014  on 9-18: 6.810)
Latest value: 2014-10-31 9.701
Latest value: 2014-11-30 13.314
Latest value: 2014-12-31 16.842
Latest value: 2015-1-31 20.229
Latest value: 2015-3-8 22.813
Latest value: 2015-3-31 24.036
Latest value: 2015-4-30 24.066
Latest value: 2015-5-31 21.496
Latest value: 2015-6-30 15.263
Latest value: 2015-7-31 8.604
Latest value: 2015-8-31 5.975
Latest value: 2015-9-15 5.713
Latest value: 2015-9-30 6.032
Latest value: 2015-10-31 8.563
Latest value: 2015-11-30 11.999
Latest value: 2015-12-31 15.652
Latest value: 2016-1-31 18.536
Latest value: 2016-2-29 20.660
Latest value: 2016-4-1 22.337
Latest value: 2016-5-1 22.268
Latest value: 2016-6-1 19.201
Latest value: 2016-7-1 13.177
Latest value: 2016-8-1 7.448
Latest value: 2016-9-1 4.638
Latest value: 2016-10-1 4.869
Latest value: 2016-11-1 6.534
Latest value: 2016-12-1  9.515
Latest value: 2016-12-31 13.078
Latest value: 2017-1-31 16.162
Latest value: 2017-2-28 18.608
Latest value: 2017-3-31 20.398
Latest value: 2017-4-30 20.64
Latest value: 2017-5-31 18.11
Latest value: 2017-6-30 12.164
Latest value: 2017-7-31 6.725
Latest value: 2017-9-15 4.658
Latest value: 2017-11-30 10.871

I have updated my graphics at Arctische Pinguin https://sites.google.com/site/arctischepinguin/home/piomas/ (https://sites.google.com/site/arctischepinguin/home/piomas/) for the latest data.

Monthly data:
(https://sites.google.com/site/arctischepinguin/home/piomas/grf/piomas-trnd2.png)
Daily Anomalies:
(https://sites.google.com/site/arctischepinguin/home/piomas/grf/piomas-trnd3.png)
Daily data with a "prediction" based on exponential trend:
(https://sites.google.com/site/arctischepinguin/home/piomas/grf/piomas-trnd4.png)
Title: Re: Latest PIOMAS update
Post by: Wipneus on March 12, 2013, 05:21:11 PM
From the official graphs:

Thickness:

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fpsc.apl.washington.edu%2Fwordpress%2Fwp-content%2Fuploads%2Fschweiger%2Fice_volume%2FBpiomas_plot_daily_heff.2sst.png&hash=efca6fb136d508b98d939b35635a8690)
Title: Re: Latest PIOMAS update
Post by: Wipneus on March 12, 2013, 05:28:20 PM
So according to PIOMAS , the ice volume and thickness (and therefore area) are at the beginning of March almost the same as in 2012. And still a month to grow even thicker.
Title: Re: Latest PIOMAS update
Post by: Dave C on March 12, 2013, 06:11:08 PM
Well it looks like the ice cracks had a big effect, but in the opposite direction many people were predicting.  The previous record for volume gain through March 1st was 16.4. We are at 16.7 now. It is fairly likely we will break or tie the record for volume gain this year. 

We will see if the cracks result in a record volume loss as well but I am skeptical. The cracks are far from the fram strait and will have time to refreeze. Volume doesn't peak until sometime in April.

I am going to predict a recovery year, with an expected value for volume minimum close to last years number. 
Title: Re: Latest PIOMAS update
Post by: crandles on March 12, 2013, 06:19:22 PM
So according to PIOMAS , the ice volume and thickness (and therefore area) are at the beginning of March almost the same as in 2012. And still a month to grow even thicker.

2011 day 60 19.981
2012 day 60 19.812
2013 day 60 19.945

So volume also almost same as 2011 as well as 2012.

One reason for growing thicker faster is heat can be lost faster through thinner ice. If the ice has caught up in thickness that reason disappears.

So is any further thickening relative to 2012 likely to be a result of less snow cover? If so, the lower snow cover might mean lower albedo and a faster start to the melt season? The frozen over cracks certainly look like they have lower albedo.


Got a feeling there was a diagram showing evolution of ice thickness and snow thickness after instantaneous removal of sea ice in Schroder and Connolley 2007 but I am struggling to find it now.
Title: Re: Latest PIOMAS update
Post by: Wipneus on March 12, 2013, 07:20:42 PM
For Dave:

Attached is a graph of PIOMAS ice gains (max.volume - min.volume.previous.year).

It shows, as most people here are aware, that volume gains are on the increase. Record gains should be quite normal, and are entirely expected because of  the record low September ice.



Title: Re: Latest PIOMAS update
Post by: Peter Ellis on March 12, 2013, 09:36:10 PM
Well it looks like the ice cracks had a big effect, but in the opposite direction many people were predicting.  The previous record for volume gain through March 1st was 16.4. We are at 16.7 now. It is fairly likely we will break or tie the record for volume gain this year. 
Record gain straight after record loss isn't at all unexpected - it's well-known that there is less of a downward trend in winter than in summer, and that the annual cycle is getting gradually wider.


I am going to predict a recovery year, with an expected value for volume minimum close to last years number.
Staying at the same volume as the all time record low is not a recovery!  If the volume is the same, then any recovery in area/extent just means the ice is thinner. Note that for 2007 -> 2008, there was a reasonable if short-lived "bounce back" in summer minimum extent.  However, that time round, 2008 was well ahead of 2007 even by the end of January.  The fact that we're not substantially above 2012 by now suggests we're unlikely to see much of a "bounce back" from last year's record low, and may be close to a second record in two years.  How is that a recovery?
Title: Re: Latest PIOMAS update
Post by: PhilGChapman on March 12, 2013, 11:10:45 PM
Wipneus,

How did you fit that trend line on the annual gain plot? The data are very scattered.

Cheers, Phil
Title: Re: Latest PIOMAS update
Post by: Dave C on March 12, 2013, 11:18:41 PM
Peter Ellis-
What I meant to say was that it is looking like there will be a deviation from the volume loss trend in a positive direction.

Based on various trend lines volume could be expected to range from 2.0 to 2.7.  It's looking like ice volume will significantly deviate from these trends.

I guess I could have been more precise.
Title: Re: Latest PIOMAS update
Post by: TerryM on March 12, 2013, 11:45:20 PM
Wipneus


As always thanks so much for your work!


I'm planning on stealing a few of your graphics for a presentation I'll be doing in early May - with proper accreditation and your consent of course.


It would be nice if PIOMAS linked to your graphics page as you've managed to tease out so much more from their data than they're able or willing to share.


I wonder how PIOMAS is handling the fractures so prevalent this year. When we had the stacked up FYI after the "Ice Hurricane" in late 2011 it melted away with astonishing speed. I have a feeling that though we're losing heat through the fractures, this spring will see even faster ice loss than last year.


Terry
Title: Re: Latest PIOMAS update
Post by: Dave C on March 13, 2013, 01:37:53 AM
Wipneus- Yea I've seen that data. It's part of why I came up with my 2007 theory.

Average through 2007-16.3
Something crazy happens.
Average since then- 17.9(including this year's likely value)

If the discontinuity is that huge, can you accurately map it in one smooth function?
My theory is that even though you have less data it would be more accurate to focus primarily on post-2007 trends.
Title: Re: Latest PIOMAS update
Post by: crandles on March 13, 2013, 03:17:45 AM
If the discontinuity is that huge, can you accurately map it in one smooth function?
My theory is that even though you have less data it would be more accurate to focus primarily on post-2007 trends.

http://farm9.staticflickr.com/8224/8334481723_947248554a_b.jpg (http://farm9.staticflickr.com/8224/8334481723_947248554a_b.jpg)

Who wants a smooth function? I think my 'project melt' is quite a good fit for 'melt'. Isn't this more impressive for not being smooth in close to the right places? However, if there were only differences in a couple of places I wouldn't think that, I would instead think overfitting.

You can model the freeze volume as 2 horizontal lines or as a smooth curve. Maybe the 2 horizontal lines is a better fit but that doesn't mean it is going to be a better predictor. With the level of noise involved I would be very surprised if the better fit is significant. I suggest that despite the better fit, two horizontal lines is unlikely to be a better predictor if the curve is more physically plausible.

I think the curve is more physically plausible.
Title: Re: Latest PIOMAS update
Post by: Dave C on March 13, 2013, 05:06:08 AM
I don't spend any time at all worrying about what is a better fit. I just think about how to look at the data in a way that makes the best predictions.

I think it would be a good idea to have an ice prediction contest where people commit to a number and see how well it matches.  Of course a lot of it would be luck, but over multiple predictions I think some skill might emerge.
Title: Re: Latest PIOMAS update
Post by: Wipneus on March 13, 2013, 07:41:47 AM
Wipneus,

How did you fit that trend line on the annual gain plot? The data are very scattered.

Cheers, Phil

Hi Phil. It is a Loess (http://en.wikipedia.org/wiki/Local_regression (http://en.wikipedia.org/wiki/Local_regression)) curve fitted to the data, it is the default smoothing method for the plotting library (ggplot2) that I used in R to produce the graph.

I find the curves are quite useful for trends that are severely non-linear and similar to what an expert human would sketch with graphing paper and pencil.

I realize however now that the graph compares the gain on first of March 2013, with the full gain in other years (realized in April). For an all apples graph, here is the gain on day 60 (attached):
   
Title: Re: Latest PIOMAS update
Post by: Wipneus on March 13, 2013, 08:15:33 AM
Wipneus

I'm planning on stealing a few of your graphics for a presentation I'll be doing in early May - with proper accreditation and your consent of course.


Terry, by all means. I am glad you find the graphs are useful.

It would be nice if PIOMAS linked to your graphics page as you've managed to tease out so much more from their data than they're able or willing to share.

I am not so sure they like my graphs that much. My graphs are trying to focus on the question of zero ice. I do that because I think their data is begging for it. You can look at all the official PIOMAS graphs without ever realizing that that event might be within the next decade,

I wonder how PIOMAS is handling the fractures so prevalent this year.

Good question, we don't even know whether the ice in the modeled world of PIOMAS has ice fractures as bad as, or as outstanding as we see on the satellite images now. PIOMAS may have been vindicated somewhat, but only as far as the overall annual cycle and long time trends. The details may differ from reality still.

Attributing the volume increase mostly to the cracks is IMO jumping conclusions. It also ignores the well known physics that colder than normal  temperatures over thinner than normal ice will give larger than normal ice volume growth.
Title: Re: Latest PIOMAS update
Post by: Wipneus on March 13, 2013, 09:06:48 AM

If the discontinuity is that huge, can you accurately map it in one smooth function?


Dave, beware. I was taught a long time ago that physical laws are continuous and the world is mostly continuous as well if studied detailed enough. We already know that volume trends are highly non-linear. Human minds are known (for a fact) not to understand exponential trends and falsly introduce discontinuous, sudden, or unexpected behavior when faced with exponential phenomena.
Just assuming won't do here to make a convincing argument.


-Google for humans do not understand exponential trends
-read Limits to growth, club of Rome


PS, attached is trend focused on 2007-2013. I find it makes your case (IIUC ) look even worse.
Title: Re: Latest PIOMAS update
Post by: Dromicosuchus on March 13, 2013, 01:35:19 PM
I know that this jump in thickness probably isn't actually all that reassuring, what with it being not only first-year ice but first-year ice that's formed quickly, thus expelling less brine. Nonetheless, I have to say it's somewhat comforting to see the Arctic heading towards the 2013 melt season with a thickness that isn't 1,000 km^3 lower than last year.  It won't make a particle of difference to the long-term trend, but as someone who's hoping to get out of the U.S. and into a more northerly country before the ice crumbles completely, every little bit of extra ice is good ice, and every year that the final collapse is delayed is a good year.
Title: Re: Latest PIOMAS update
Post by: Dave C on March 13, 2013, 08:20:32 PM
Wipneus- We use more data points because it gives us more statistical significance and keeps us from unconsciously cherrypicking. But the problem with the arctic is that those data points are not equally valid. Each previous year is less likely to describe the arctic as it actually is today. As I've said, I could be wrong, but it seems that pre-summer 2007 data is describing a different enough situation that you might be better off dealing with the large statistical problems of a small data set.
Also, in your graphic you should exclude winter 2006-07 since that was before the divide.

Right now I'm just trying to look at the problem from different angles. I'm not in a position to argue authoritatively against your approach, but it seems worth a try to overweight the recent data. At the end of the day it's about what model makes better predictions.

A 5 year linear trend is currently predicting 3.35 will be the minimum volume this year.
A 10 year linear trend is predicting 3.0.
Your exponential trend is predicting 2.0.

I certainly don't have everything figured out, but I would be willing to bet that my 5 year prediction is more accurate this year than your exponential model.
Title: Re: Latest PIOMAS update
Post by: Wipneus on March 15, 2013, 10:55:53 AM
Wipneus- We use more data points because it gives us more statistical significance and keeps us from unconsciously cherrypicking. But the problem with the arctic is that those data points are not equally valid. Each previous year is less likely to describe the arctic as it actually is today.

Hmm. You correctly state mention the advantage of looking at the trends and mention cherrypicking(sic) as a dirty word. Followed by a defending of cherry picked data. All without a single hint of analysis.

Repeat: the physical laws that cause the trend are the same in 1980 and in 2013. The behavior is clearly non-linear, so apparent to the human eyes discontinuities are to be expected.
I have showed a trend drawn with an algorithm that has been found to be much better than deceiving eyes. 

Also, in your graphic you should exclude winter 2006-07 since that was before the divide.


It seems that your algorithm is: drop points until the result is what you want.  And you are wrong:
cherry picking as you suggest an dropping the 2007 gain, does not change anything at all: 1st of March 2013 data point lies comfortably in the confidence range.

You would have known that if instead of eye'ing the graph you would have tried an analysis.

Right now I'm just trying to look at the problem from different angles. I'm not in a position to argue authoritatively against your approach, but it seems worth a try to overweight the recent data. At the end of the day it's about what model makes better predictions.

Indeed, I tried to do here for an exponetial fit: https://sites.google.com/site/arctischepinguin/home/piomas/grf/piomas-trnd6-1.png (https://sites.google.com/site/arctischepinguin/home/piomas/grf/piomas-trnd6-1.png)
gomperts model:
https://sites.google.com/site/arctischepinguin/home/piomas/grf/piomas-trnd9-1.png (https://sites.google.com/site/arctischepinguin/home/piomas/grf/piomas-trnd9-1.png)

Too close to call I think.

Your exponential trend is predicting 2.0.

I'd prefer to say a range of 0 to 4, best value 2. The uncertainty is of course not very satisfying, but that is what the exponential trend method gives.
Title: Re: Latest PIOMAS update
Post by: Buddy on March 16, 2013, 11:59:56 AM
My nonscientific mind thinks your extrapolation might be correct.  Every bit of "logic" tells me it is toast.....and PDQ (pretty darn quick)  (1) all the positive feedback effects have been kicking in over the past 5 years (2) increasing amounts of CO2 in the atmosphere (3) warm ocean anomaly in the Arctic and north Atlantic (4) early start to Greenland melt season does not bode well for the Arctic was well.  So when I "step back from the numbers".....the direction is clear....and the "increasing speed of the direction" is also clear.

TOO many things stacked against the Arctic and Greenland as well.  One of these years....and this year MAY be the year....the melting in the Arctic and/or Greenland is going to "scare" more "mainstream/average" folks.  THAT is what it will take to get some political action....and some substantive change in policy.

At this point...most people who visit this board often (which includes me) think the Arctic ice sheet is gone within 2 - 5 years (I think it is summer of 2015 or 2016).







Title: Re: Latest PIOMAS update
Post by: Jim Pettit on March 20, 2013, 03:32:32 AM
Based on a discussion in which I was involved in another forum, I've gone ahead created two new graphs reflecting the same data set in two different manners. These graphs show monthly average PIOMAS sea ice volume from 1980 to now not in terms of absolute volume, but as a percentage of the 1979 value for that month.

The first is a polar plot, with 1979 at the top and consecutive years running clockwise:

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fiwantsomeproof.com%2Fextimg%2Fsiv_monthly_average_percentage_of_79_polar.png&hash=a411cd455692734c76fdf58f80e5d8ca)

The second is the same data (and color scheme) represented in a standard line graph:

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fiwantsomeproof.com%2Fextimg%2Fsiv_monthly_average_percentage_of_79.png&hash=025a6aa1a709b61a5675da3cc5f40d14)

Both of these charts show, as do so many others, that something pretty remarkable and alarming is happening at the North Pole. Not, of course, that that'll come as a surprise to anyone who frequents Neven's site...
Title: Re: Latest PIOMAS update
Post by: dlen on March 20, 2013, 04:00:10 AM
With data as noisy as they are and no convincing explicit physical model in the background, eyballing the decrease is (imho) as good as any mathematical model can be. Or in other words: extrapolation of any kind holds only under the assumption, that the processes, which lead to this unexpectedly rapid loss, continue more or less the way they did.

This is not unreasonable.

But on the other hand, a switch to a different weather pattern, leading to, say, more hours of overcast and subsequently less melting, cannot be ruled out.

At the end of the day, we are left with a mixture of common sense, guts feeling and fit functions.
Title: Re: Latest PIOMAS update
Post by: Bob Wallace on March 20, 2013, 11:54:01 PM
But on the other hand, a switch to a different weather pattern, leading to, say, more hours of overcast and subsequently less melting, cannot be ruled out.

True, but so far I haven't seen anyone reporting that sunny day overcast is increasing.  Overcast after the Sun drops below the horizon should increase melting/water warming as it should trap heat.

If the weather (climate) is going to shift to be more favorable to ice retention then is needs to get going.  It would seem that if the physics of less ice was going to change the weather pattern then we would be seeing signs by now.

Time is certainly of the essence. 
Title: Re: Latest PIOMAS update (April)
Post by: Wipneus on April 05, 2013, 05:46:39 AM
New graphics in the top post.
Title: Re: Latest PIOMAS update (April)
Post by: crandles on April 05, 2013, 12:36:23 PM
Great graphs and impressively fast as usual. Thanks you Wipneus!

2011 day 60 19.981
2012 day 60 19.812
2013 day 60 19.945

2011 day 90 21.568
2012 day 90 21.665
2013 day 90 21.612

2011 30 day increase 1.587
2012 30 day increase 1.853
2013 30 day increase 1.667

Less of a last 30 day increase than last year putting back below last year
More of a last 30 day increase than 2011 putting us above 2011

A strange combination? Random fluctuation or to some extent explainable as less ice than last year means more growth than 2012 and more ice than 2011 means less growth than 2011?
Title: Re: Latest PIOMAS update (April)
Post by: Apocalypse4Real on April 05, 2013, 01:52:48 PM
Wipneus and Jim,

Thanks as always for excellent work!

Wipneus, thanks for the permission for use, I lecture in a week on Climate Change in an ethics course, your graphics will be very helpful.

A4R
Title: Re: Latest PIOMAS update (May)
Post by: Wipneus on May 04, 2013, 06:32:48 AM
Updated, new graphics in the top post.
Title: Re: Latest PIOMAS update (May)
Post by: crandles on May 04, 2013, 11:41:38 AM
Great graphs and impressively fast as always. Thanks you Wipneus!

2011 day 90 21.568
2012 day 90 21.665
2013 day 90 21.612

2011 max day 103 21.961
2012 max day 114 21.923
2013 max day 107 21.823

2011 day 120 21.336
2012 day 120 21.568
2013 day 120 21.273 

2011 30 day decrease 0.232
2012 30 day decrease 0.097
2013 30 day decrease 0.339

2011 Drop max to day 120 0.625 over 17 days
2012 Drop max to day 120 0.355 over 6 days
2013 Drop max to day 120 0.55 over 13 days

So the maximum is slightly less than last two years and the decline since the peak is pretty rapid.
Now 0.063 below 2011 and 0.295 below 2012.
Title: Re: Latest PIOMAS update (May)
Post by: birthmark on May 04, 2013, 01:04:25 PM
Hello, PIOMAS has updated:
Latest value: 2013-3-1 19.945
Latest value: 2013-3-31 21.612
Latest value: 2013-4-30 21.273

I have updated my graphics at Arctische Pinguin https://sites.google.com/site/arctischepinguin/home/piomas/ (https://sites.google.com/site/arctischepinguin/home/piomas/) for the latest data.

Wipneus, thanks for all the work you do on those graphs. I find them interesting and informative. I have a question, is this the first time that the projection for Volume includes zero within the error bars?
Title: Re: Latest PIOMAS update (May)
Post by: Wipneus on May 04, 2013, 01:15:40 PM

Wipneus, thanks for all the work you do on those graphs. I find them interesting and informative. I have a question, is this the first time that the projection for Volume includes zero within the error bars?

Year 2013 is the first year that has an expected minimum volume with a confidence range that includes zero.

I think I did show that for the first time November (maybe December) last year.

New this month are error bars around the maximum and a few more dates, responding to a request/question made on the blog.
Title: Re: Latest PIOMAS update (June)
Post by: Wipneus on June 05, 2013, 06:46:05 AM
Updated, graphics in the top post.
Title: Re: Latest PIOMAS update (June)
Post by: Bob Wallace on June 05, 2013, 06:55:18 AM
Thanks for the update.
Title: Re: Latest PIOMAS update (June)
Post by: ChrisReynolds on June 05, 2013, 07:43:25 AM
PIOMAS always seems to update after I've gone to bed. Then I have work in the morning.  >:(

The anomalies are very interesting; looks like this year could break the pattern of the previous three.
Title: Re: Latest PIOMAS update (June)
Post by: slow wing on June 05, 2013, 08:55:16 AM
Thanks very much Wipneus, I always look forward to your monthly ASI volume plots.



Of course, that piques our curiosity and raises obvious questions. For more detail, could someone please remind me if PIOMAS now makes available their average thickness values by region or else on a grid? (Or, conceivably, even by parameterisation.)  If so, does anyone on this talented blog/forum do thickness maps and also year-to-year thickness difference maps from the PIOMAS data? Thanks, slow wing.
Title: Re: Latest PIOMAS update (June)
Post by: ChrisReynolds on June 05, 2013, 07:47:40 PM
Slow Wing,

PIOMAS thickness is easy to calculate from the gridded data, this can be broken down regionally. However concentration is needed to match the PIOMAS thickness plot and the gridded data are only available monthly.

While the PIOMAS team have been good enough to release thickness data earlier this year (updated is normally only annual in January), they have not included concentration. So I cannot calculate thickness. They have provided data for those of us using gridded data to use because it's been noticed what we're doing with it, they have said they will release data again this year. The PIOMAS team are not costed to provide this service to us, so I am unwilling to ask for them to upload concentration as well.

PS

As posted over at Neven's blog. I had asked for PIOMAS thickness data to be provided up to July to be available August. In view of current events I am considering asking instead for data up to June to be available in July.

Comments on this are welcome here.
Title: Re: Latest PIOMAS update (June)
Post by: SATire on June 05, 2013, 08:37:05 PM
Chris, you know that we have concentration available since some days allready.
Title: Re: Latest PIOMAS update (June)
Post by: ChrisReynolds on June 05, 2013, 09:21:46 PM
Not sure if it is compatible. The PIOMAS concentration is monthly average from the model. The model does assimilate concentration, but this may not necessarily mean that using NSIDC or other concentration is useable to calculate average thickness.

That's before you get to mapping your concentration data onto the PIOMAS grid.

It looks like a hell of a lot of work for little gain in my opinion.

Thanks anyway, and I have been reading with interest (over at Nevens blog) what you guys are up to.
Title: Re: Latest PIOMAS update (June)
Post by: slow wing on June 06, 2013, 01:31:10 AM
Chris,

   It would be very interesting to simply plot the gridded data that the PIOMAS people have given you, normalised to the areas of course, and particularly if the same data is also available for the same time last year so that difference plots can be done.

  If they provide the ice volumes in grid squares of known area then that indeed provides an average ice thickness for that square and under one definition. (For my tastes, that is probably the most interesting definition as well.) Concentration data is not needed to plot that much.

  I appreciate your point that they are not paid to provide extra data and are doing it as a favour. It is good of them to do that, and great as well that they have satellite data and other information to work from. Whoever does the plots is standing on the shoulders of many hard working scientists.

Title: Re: Latest PIOMAS update (June)
Post by: ChrisReynolds on June 06, 2013, 08:05:08 AM
You can find PIOMAS thickness plots here:
https://drive.google.com/folderview?id=0B3pB-kdzoLU3bENnNkxPZkRGLWM&usp=sharing (https://drive.google.com/folderview?id=0B3pB-kdzoLU3bENnNkxPZkRGLWM&usp=sharing)

I have previously done interannual and intermonth thickness but I'll have to dig the url out of an email as it's not in my favourites. I've not updated this for 2012 and 2013.

The PIOMAS data is available to all here:
http://psc.apl.washington.edu/zhang/IDAO/data_piomas.html (http://psc.apl.washington.edu/zhang/IDAO/data_piomas.html)
Title: Re: Latest PIOMAS update (June)
Post by: Wipneus on June 08, 2013, 09:07:17 AM
Also gridded thickness data did update.

Compare May 2013 with 2012:

(https://sites.google.com/site/arctischepinguin/home/piomas/grf/thickness_chg_may13.png)
Title: Re: Latest PIOMAS update (June)
Post by: jdallen on June 08, 2013, 10:10:18 AM
@Wipneus - Unless I'm missing something, looks mostly like a 'wash' in terms of over-all volume.  Key difference I'd say would be the thinning at higher latitudes, which ( I presume...) is the source of MYI going forward.

All in all though, seems like large amounts of ice are being spun out of the central arctic basin, much as a centrifuge forces anything heavy to the bottom of the tubes it spins.  That may not work out so well for ice in the Beaufort, even if we don't see as dramatic an early melt out.
Title: Re: Latest PIOMAS update (June)
Post by: slow wing on June 08, 2013, 12:33:20 PM
Thanks, Wipneus, for that PIOMAS difference map!

Agreed, jdallen, the ice has thinned from last year in the middle. The overall volume looks similar* because that is approximately compensated by thicker ice on average around the fringes, where most of it would generally be expected to melt away anyway.

That distribution suggests to me that this year has more than a 50% chance of a low volume record, all else being equal. (And I personally can't figure out which way the other factors are leaning.)



* Wipneus, in the OP gives "Latest value: 2013-5-31 19.087". Does anyone have the corresponding volume for that date in 2012? (For strict comparison with the graph, isn't it the plot for the  monthly average anyway, rather than the volume on the last day of May?)
Title: Re: Latest PIOMAS update (June)
Post by: Wipneus on June 08, 2013, 12:48:53 PM
 Thickness map:

(https://sites.google.com/site/arctischepinguin/home/piomas/grf/pg_5_2013.png)

Thick ice in Chukchi and East Siberian Sea.
Title: Re: Latest PIOMAS update (June)
Post by: Wipneus on June 08, 2013, 12:54:16 PM
Thanks, Wipneus, for that PIOMAS difference map!

* Wipneus, in the OP gives "Latest value: 2013-5-31 19.087". Does anyone have the corresponding volume for that date in 2012? (For strict comparison with the graph, isn't it the plot for the  monthly average anyway, rather than the volume on the last day of May?)

18.186

The maps of the gridded data are monthly averages.

PIOMAS data: http://psc.apl.washington.edu/wordpress/research/projects/arctic-sea-ice-volume-anomaly/data/ (http://psc.apl.washington.edu/wordpress/research/projects/arctic-sea-ice-volume-anomaly/data/)
PIOMAS gridded data: http://psc.apl.washington.edu/zhang/IDAO/data_piomas.html (http://psc.apl.washington.edu/zhang/IDAO/data_piomas.html)
Title: Re: Latest PIOMAS update (June)
Post by: Tor Bejnar on June 10, 2013, 05:35:11 PM
The May 31st datum appears to be outside the suggested 2013 confidence range.  I expect the curve will soon notice its predicament, and will quietly migrate back into its predicted course over the next 8 weeks, hoping that nobody noticed its errant behavior. [Excuse the personification of a curve on a graph.]  ;)
Title: Re: Latest PIOMAS update (June)
Post by: ChrisReynolds on June 10, 2013, 06:07:46 PM
Tor,

To put it in more mechanistic terms. The further south the ice edge is relative to the current pseudo-equilibrium (has 2012 set a new lower equilibrium point?), the more insolation it will be subjected to, and a faster volume loss should be expected to occur.
Title: Re: Latest PIOMAS update (June)
Post by: Wipneus on June 10, 2013, 06:27:10 PM
Tor,

The further south ...  the more insolation it will be subjected to.

Chris, insolation within the Arctic circle increases with latitude:

(https://sites.google.com/site/arctischepinguin/_/rsrc/1318000025092/home/asib/insol120-219.png)
Title: Re: Latest PIOMAS update (June)
Post by: Tor Bejnar on June 10, 2013, 06:44:47 PM
Chris & Wipneus,
Yup, insolation along with warm Pacific and Atlantic waters (and, possibly, churned-up salty & warm Arctic water) working on the Persistent Arctic Storm mélange (slush puppy ice left by the churning winds) plus any other special (weather) effects Ægir and Rán (too far north for Poseidon) choose to throw down this year, including forced migration of ice through the Fram. :)
Title: Re: Latest PIOMAS update (June)
Post by: ChrisReynolds on June 10, 2013, 08:47:06 PM
Wipneus,

Is that TOA or surface, adjusted for angle of incidence?
Title: Re: Latest PIOMAS update (June)
Post by: ChrisReynolds on June 10, 2013, 09:07:32 PM
Forget that...

Thanks Wipneus, I wasn't aware of it. The figures you have are in line with radiometer figures from a 1993 cruise off Siberia.
Title: Re: Latest PIOMAS update (June)
Post by: Wipneus on June 10, 2013, 09:16:05 PM
Wipneus,

Is that TOA or surface, adjusted for angle of incidence?

Yet an answer: atmosphere is ignored and the angle of incidence is taken into account.
Title: Re: Latest PIOMAS update (June)
Post by: ChrisReynolds on June 10, 2013, 09:59:20 PM
I've just been doing some trigonometry and it's really obvious: Insolation must be highest at the pole since as one moves south from the pole the angle of incidence begins to vary substantially.
Title: Re: Latest PIOMAS update (June)
Post by: Wipneus on June 11, 2013, 07:43:01 AM
insolation vs latitude was discussed on the asi blog here:

http://neven1.typepad.com/blog/2011/10/september-2011-sea-ice-extent-looking-ahead.html (http://neven1.typepad.com/blog/2011/10/september-2011-sea-ice-extent-looking-ahead.html)
Title: Re: Latest PIOMAS update (July)
Post by: Wipneus on July 04, 2013, 11:30:51 AM
Updated, graphs in the top post.
Title: Re: Latest PIOMAS update (July)
Post by: crandles on July 04, 2013, 01:03:12 PM
Great work and fast as always.

At 31 May (day 151) we had 0.9 K Km^3 more than last year (19.087 vs 18.186)

By 23 Jun (Day 174) the gap had doubled to 1.861 K Km^3 (14.662 vs 12801)

In last 7 days, volume has begun to catch up a little and gap is down to 1.72 K Km^3 (13.002 vs 11.282).

At that rate of catch up, it would take more than 12 weeks to catch up, and we haven't got that long.

I also doubt that that rate of catch up would continue once Hudson, Baffin, and South Western Kara melt out. i.e. we may be catching up because we are melting over a larger area. The areas will become more similar as current thin low latitude ice areas melt and then what would be the reason for melting more volume to continue catching up? This year has had more ice area therefore less ocean collecting heat so there may well be less volume melt again later in the season.
Title: Re: Latest PIOMAS update (July)
Post by: wanderer on July 04, 2013, 01:10:07 PM
As expected, but now confirmed!
This melt season is so exciting - I wonder how the last days of fast melting show up in next month's graph!
Title: Re: Latest PIOMAS update (July)
Post by: Wipneus on July 04, 2013, 01:23:29 PM
For what I thought I knew about the ASI, this is a both sobering and exciting season.

Anyway, the anomaly is now at minimum (normally ) and at a level slightly above 2010. We are going to the part of the season where the negative swing of the anomaly will get smaller again.

One of the proposed reasons for this was that the easy ice was gone, that reason is not valid now. If the anomaly stays constant, or even get lower than anything is still possible.
Title: Re: Latest PIOMAS update (July)
Post by: Richard Rathbone on July 04, 2013, 01:42:18 PM
Catch up with May, though not April, is to be expected. There's some sort of mechanism that means fast melt in June makes it harder to melt in July through September. and vice versa, because that's the way the historical data tend to go. May 31 to minimum is surprisingly close to a constant loss. You aren't backing off that finding of yours are you crandles? I reckon its pretty solid. I'd guess the mechanism as a mixture of thickness distribution and insolation peak sharpness.

Its not quite as far off June 2012 as I was thinking it would be, so I'll push my expectation of this year's minimum volume down a little, and say it comes in at 0.5M above 2012. I still reckon catchup with 2012 and a new record by a narrow margin is possible, but it would take the right weather all the way.

The next region in line for contributing to catch up is Beaufort.
Title: Re: Latest PIOMAS update (July)
Post by: Vergent on July 04, 2013, 02:47:35 PM
Arctic ice volume is kilo scale km^3, not mega scale. Sorry for the nit picking, but being off by a factor of 1,000..... Its like squeaking the chalk on the blackboard.

Vergent
Title: Re: Latest PIOMAS update (July)
Post by: Richard Rathbone on July 04, 2013, 04:49:48 PM
T not kk3 if you are being picky in SI (no stacking allowed). ;)

M for thousand and MM for million if you stack prefixes American style.

If usage is loose it could be a thousand or a million of anything and if the magnitude isn't clear from the context you should always ask the user to clarify rather than assume they are using it the same way you are. M on its own is seriously ambiguous when used across cultures.
Title: Re: Latest PIOMAS update (July)
Post by: Jim Pettit on July 04, 2013, 05:24:36 PM
The year with the lowest volume lost after June 30 was--drum roll, please--2012. That's because so much of the fringe ice was gone by July 1 last year, which is obviously not the case this year. In fact, as this chart shows, post-June volume loss has been decreasing over the years as more and more ice has been melting earlier and earlier:

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fimg543.imageshack.us%2Fimg543%2F2271%2Fbgjl.png&hash=ecbb7524ee8771f09607fcb3bace9d98)

So my observations/assumptions/thoughts are these:

1) Roughly the same amount of volume is lost every year (between 16.5k and 17k km3);

2) This year's currently higher volume isn't due to thicker ice in the middle of the pack, but later-melting ice at the fringes;

3) That ice at the fringes is going to melt anyway, as it does nearly every year;

4) Extent and area have both indicated over the past several days that insolation is finally catching up, and they're starting to drop in earnest;

5) 2013 had the lowest volume maximum on record.

Upshot: there's a better than 50% chance that this year's mid-September volume minimum will be a new record. (I put it at 3.15k km3).
Title: Re: Latest PIOMAS update (July)
Post by: Frivolousz21 on July 04, 2013, 05:37:53 PM
How much of this is peripheral ice that didn't melt out vs 2010, 2011, and 2012?


Title: Re: Latest PIOMAS update (July)
Post by: crandles on July 04, 2013, 07:04:20 PM

3) That ice at the fringes is going to melt anyway, as it does nearly every year;

4) Extent and area have both indicated over the past several days that insolation is finally catching up, and they're starting to drop in earnest;


Average thickness for last three years (PIOMAS vol/CT Area)
1.747857842
1.70610248
1.71219451

If the average thickness was particularly low because of large areas of very thin ice at low latitude then you might have a point.

As it is, in a couple of weeks the area will have caught up some but this will mean that the average thickness will be noticeably higher than last year as well as still having more area.

So I don't think your argument works.
Title: Re: Latest PIOMAS update (July)
Post by: Dromicosuchus on July 04, 2013, 07:20:42 PM
Oh, thank goodness.  I have to say I wasn't expecting this, as I supposed that Ekman pumping acting on the fractured ice near the center would have drawn volume down.  I suppose the long-lasting perimeter saved the day.  I'm interested by the similarity between this year's June average uptick and that that occurred in 2008; it begins to look, to me at least, like this will end up being another "recovery" year (I know, I know, it's hardly a recovery and the trend continues.  A hiatus year?), which I have to say is welcome.  Time is precious, and the longer the Arctic holds back from complete collapse, the happier I am.  I want to have time to get myself North.
Title: Re: Latest PIOMAS update (July)
Post by: ChrisReynolds on July 04, 2013, 07:31:14 PM
T not kk3 if you are being picky in SI (no stacking allowed). ;)

M for thousand and MM for million if you stack prefixes American style.

If usage is loose it could be a thousand or a million of anything and if the magnitude isn't clear from the context you should always ask the user to clarify rather than assume they are using it the same way you are. M on its own is seriously ambiguous when used across cultures.

????? As an engineer M stands for mega, which is 10^6 or one million.
Title: Re: Latest PIOMAS update (July)
Post by: ChrisReynolds on July 04, 2013, 07:36:32 PM
No chance of beating 2012 now, as Neven has pointed out over on his blog (in comments) this year underlines the importance of the spring melt. It's so important that if it's missed it generates the appearance of a recovery.
Title: Re: Latest PIOMAS update (July)
Post by: Bob Wallace on July 04, 2013, 08:06:32 PM
2) This year's currently higher volume isn't due to thicker ice in the middle of the pack, but later-melting ice at the fringes;

3) That ice at the fringes is going to melt anyway, as it does nearly every year;

4) Extent and area have both indicated over the past several days that insolation is finally catching up, and they're starting to drop in earnest;

I hope Wipneus doesn't mind me linking to his excellent new regional maps in this comment.  But they see to be the perfect way to illustrate what Jim is saying.

(https://sites.google.com/site/arctischepinguin/home/amsr2/grf/amsr2-extent-regional.png)

(https://sites.google.com/site/arctischepinguin/home/amsr2/grf/amsr2-area-regional.png)

It looks to me that the CAB might not be doing as well this year as it was last.  Take a look at the Area chart.  As long as the CAB is melting at close to the 2012 rate then the horse race is not over.  The other two regions in which we might expect some remaining ice are the Greenland Sea and Canadian Archipelago.  GS is ahead of last year and CA about tied.
Title: Re: Latest PIOMAS update (July)
Post by: jdallen on July 04, 2013, 08:10:15 PM
No chance of beating 2012 now, as Neven has pointed out over on his blog (in comments) this year underlines the importance of the spring melt. It's so important that if it's missed it generates the appearance of a recovery.

Not so sure of this conclusion yet.  The early July losses have been shockingly large.  Looking at holes opening up in the <b>center</b> of ice covered areas, I am left with serious concern regarding the ice's durability.

I'm also wondering about wide swaths of extent that are showing up "brown" - it seems like these are weaker still.

That said, I hope you are right, Chris.
Title: Re: Latest PIOMAS update (July)
Post by: Neven on July 04, 2013, 08:20:18 PM
No chance of beating 2012 now,

The chance is small.  :)
Title: Re: Latest PIOMAS update (July)
Post by: Bob Wallace on July 04, 2013, 08:26:51 PM
No chance of beating 2012 now

It looks like there's a decent chance of a big hole opening up in the CAB.  That happens and 2012 is in for a struggle. 

It's all about the CAB. 
Title: Re: Latest PIOMAS update (July)
Post by: ChrisReynolds on July 04, 2013, 09:01:17 PM
No chance of beating 2012 now, as Neven has pointed out over on his blog (in comments) this year underlines the importance of the spring melt. It's so important that if it's missed it generates the appearance of a recovery.

Not so sure of this conclusion yet.  The early July losses have been shockingly large.  Looking at holes opening up in the <b>center</b> of ice covered areas, I am left with serious concern regarding the ice's durability.

I'm also wondering about wide swaths of extent that are showing up "brown" - it seems like these are weaker still.

That said, I hope you are right, Chris.

July volume losses are large but...

From 30 June to minimum losses have a small downward trend from 1979, then a step drop post 2010, i.e. late summer losses are decreasing (see below). Not increasing. It remains to be seen whether 2013 will be in the pre or post 2010 set.

2010 to 2012 average loss 8.24k km^3.
1979 to 2009 average loss 9.88k km^3.
1979 to 2009 trend -0.0214x + 10.227.
Title: Re: Latest PIOMAS update (July)
Post by: Jim Pettit on July 04, 2013, 10:51:28 PM
From 30 June to minimum losses have a small downward trend from 1979, then a step drop post 2010, i.e. late summer losses are decreasing (see below). Not increasing.

That's my point. Those post-June drops have been getting increasingly smaller over the years for the simple reason that more fringe ice has melted out earlier. And that hasn't happened this year. Now, my "theory" will obviously be proved wrong if SIA stays a million km2 or so above 2013. But I'm willing to be money that it won't. I'm not saying either area or volume will necessarily catch 2012--but by by the same token I don't think the odds of a record this year are nearly as remote as some are expressing. And I do think it's far too early to call it a day and shove 2013 into the "recovery" column.

(I'll revisit and recalculate at the end of July; if volume then is over, say 8,000 km3, I'll admit my mistake and be happy. But I've a feeling end-of-July volume will be closer to 6.5-6.8k. And if it is, look out.)

Title: Re: Latest PIOMAS update (July)
Post by: ChrisReynolds on July 04, 2013, 11:26:02 PM
Jim,

This I exactly why I noted: "It remains to be seen whether 2013 will be in the pre or post 2010 set."

However apart from 2008, every post 2007 year has shown an increase in anomalies post June, and the 2008 decrease in June was modest. I also think that the final levelling tendency in the PIOMAS anomalies for late June 2013 is significant, such an inflection is seen in all post 2007 years. Which implies to me that the drop in anomalies is done this year, as has been the case in other post 2007 years.
Title: Re: Latest PIOMAS update (July)
Post by: Neven on July 04, 2013, 11:35:00 PM
I'm posting a PIOMAS update tomorrow or the day after that, because I want my latest post to remain at the top of the main page a bit longer.

At the danger of being accused that I express doubt because as an alarmist I don't like the data (2013 being almost 2000 km3 higher than 2012), but could PIOMAS have trouble getting to grips with this year that could be seen as the first year of the New Abnormal era that perhaps started last year? I know the weather has caused an extremely slow start, but volume as high as 2010?

I'm not really expressing doubt, as I've always stressed the uncertainty in PIOMAS output because it's a model, especially when numbers plummeted. I'm just entertaining the possibility, but will have to think about how I'm going to put it into words tomorrow.
Title: Re: Latest PIOMAS update (July)
Post by: Bob Wallace on July 04, 2013, 11:49:10 PM
What I'd love to see is regional volume graphs.  Like the extent and area above.

It looks to me that all regions but the CAB will melt out.  More precisely, the ice currently in all other regions will melt out.  The Greenland Sea and CA will likely be replenished somewhat by ice currently in the CAB.  (Beaufort is getting a late start, but it has a two month cushion based on 2012 hitting zero by the end of July.)

It could be that CAB volume for 2013 is already lower than for 2012.  If that's the case and weather from here on out contributes about the same amount of melt then it's a new record.

Title: Re: Latest PIOMAS update (July)
Post by: BornFromTheVoid on July 05, 2013, 01:05:20 AM
Something to note, the recent NSIDC update said that CryoSat found the average thickness this March to be 8% less than March 2012. http://nsidc.org/arcticseaicenews/ (http://nsidc.org/arcticseaicenews/)

This didn't appear to be the case with PIOMAS in March.
(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fpsc.apl.washington.edu%2Fwordpress%2Fwp-content%2Fuploads%2Fschweiger%2Fice_volume%2FBpiomas_plot_daily_heff.2sst.png&hash=efca6fb136d508b98d939b35635a8690)
Title: Re: Latest PIOMAS update (July)
Post by: dree12 on July 05, 2013, 03:43:34 AM
I'm posting a PIOMAS update tomorrow or the day after that, because I want my latest post to remain at the top of the main page a bit longer.

At the danger of being accused that I express doubt because as an alarmist I don't like the data (2013 being almost 2000 km3 higher than 2012), but could PIOMAS have trouble getting to grips with this year that could be seen as the first year of the New Abnormal era that perhaps started last year? I know the weather has caused an extremely slow start, but volume as high as 2010?

I'm not really expressing doubt, as I've always stressed the uncertainty in PIOMAS output because it's a model, especially when numbers plummeted. I'm just entertaining the possibility, but will have to think about how I'm going to put it into words tomorrow.

I believe it. It was really cold this spring, far colder than in 2011 or 2012. In addition to the rapid refreeze last year, it was enough to bring volume far up.
Title: Re: Latest PIOMAS update (July)
Post by: ChrisReynolds on July 05, 2013, 07:43:19 AM
With regards the weather I agree with Dree12.

The large ref-freeze was merely a result of record low ice at the end of last season. But as I've shown in my blog posts on the atmospheric set up in June, the spring melt being far less marked this year was not a surprise in view of the weather. And as the spring melt sets the melt season in the years 2010 to 2012 that we are now above 2012 in volume is quite believable to me.
Title: Re: Latest PIOMAS update (July)
Post by: Steven on July 05, 2013, 12:33:13 PM
I'm not really expressing doubt, as I've always stressed the uncertainty in PIOMAS output because it's a model, especially when numbers plummeted. I'm just entertaining the possibility, but will have to think about how I'm going to put it into words tomorrow.

Neven, I would be careful indeed to pick the right words.  By the way, many commenters on the ASIB blog will mention this issue anyway :)

The Beaufort ice was thin at the start of the melting season.  But the ice has been compressing towards the coasts.

The divergence (and thinning?) in the Arctic Basin have moved ice volume towards the fringes.

Melt pond formation and albedo drops have been way behind schedule.  Insolation has been wasted. 

Altogether, I still believe PIOMAS.
Title: Re: Latest PIOMAS update (July)
Post by: TerryM on July 05, 2013, 04:25:53 PM
Neven
Your pessimism may be justified. PIOMAS does well when melt is from the edges under clear skies. Whether the same can be said when melt consists of thinning from the center under clouds & fog is still to be seen.
Terry
Title: Re: Latest PIOMAS update (July)
Post by: Neven on July 06, 2013, 12:15:45 AM
I just posted PIOMAS July 2013 (http://neven1.typepad.com/blog/2013/07/piomas-july-2013.html) on the ASIB.

Conclusion:
Right now I'm not sure what to make of that big gap between 2013 and previous years. If it's real, this could mean that 1) the start of the melting season is of paramount importance, and 2) 2013 is a recovery year, the first one in 5 years, volume-wise. More or less the same conclusion I drew a couple of days ago, after reviewing maps showing atmospheric circulation patterns in May and July.

But I think I'm seeing a huge melting potential out there, despite those slow start weather conditions, with holes in the interior of the ice pack and lots of discoloured, thin ice on the fringes. We mustn't forget that this melting season started with the most first-year ice on record. A bad start can postpone much of that ice to melt out, but all bad starts come to an end.

I believe there will be a rapid area/extent decrease in the coming weeks, and it remains to be seen how PIOMAS is going to interpret that. If, like I said, some of those parameters are sidetracked due to the unique pattern of this melting season so far, they just might get back on track once the melting season throws off its mask.

That last one about throwing off the mask, is pretty good, if I say so myself. That will probably be turned into a subtitle for the ASI update in two weeks from now.  8)
Title: Re: Latest PIOMAS update (July)
Post by: dree12 on July 06, 2013, 01:06:50 AM
I just posted PIOMAS July 2013 (http://neven1.typepad.com/blog/2013/07/piomas-july-2013.html) on the ASIB.

Conclusion:
Right now I'm not sure what to make of that big gap between 2013 and previous years. If it's real, this could mean that 1) the start of the melting season is of paramount importance, and 2) 2013 is a recovery year, the first one in 5 years, volume-wise. More or less the same conclusion I drew a couple of days ago, after reviewing maps showing atmospheric circulation patterns in May and July.

But I think I'm seeing a huge melting potential out there, despite those slow start weather conditions, with holes in the interior of the ice pack and lots of discoloured, thin ice on the fringes. We mustn't forget that this melting season started with the most first-year ice on record. A bad start can postpone much of that ice to melt out, but all bad starts come to an end.

I believe there will be a rapid area/extent decrease in the coming weeks, and it remains to be seen how PIOMAS is going to interpret that. If, like I said, some of those parameters are sidetracked due to the unique pattern of this melting season so far, they just might get back on track once the melting season throws off its mask.

That last one about throwing off the mask, is pretty good, if I say so myself. That will probably be turned into a subtitle for the ASI update in two weeks from now.  8)

I think that PIOMAS is not far off. Looking at the thickness charts, the post-2010 era has been relatively stable. The curves for 2010, 2011, and 2012 are not far off from each other—and 2013 is closely following them as well. The arctic may possibly have reached a lower limit on annual thickness, and further volume declines may be in the form of area declines, rather than ice thinning. If this hypothesis verifies, then the PIOMAS figure is likely accurate only because area is not lower than 2010.
Title: Re: Latest PIOMAS update (July)
Post by: ChrisReynolds on July 06, 2013, 09:04:19 AM
PIOMAS is doing exactly what I'd expected in June given the other data I'd been following.
Title: Re: Latest PIOMAS update (July)
Post by: jdallen on July 06, 2013, 09:04:21 AM
I think that PIOMAS is not far off. Looking at the thickness charts, the post-2010 era has been relatively stable. The curves for 2010, 2011, and 2012 are not far off from each other—and 2013 is closely following them as well. The arctic may possibly have reached a lower limit on annual thickness, and further volume declines may be in the form of area declines, rather than ice thinning. If this hypothesis verifies, then the PIOMAS figure is likely accurate only because area is not lower than 2010.

I don't think I can agree.  Ice bridge observations earlier this year suggested large areas of ice were considerably thinner than what is being modeled. Unfortunately, we won't be able to get a sense of who's right for a few weeks yet...
Title: Re: Latest PIOMAS update (July)
Post by: Richard Rathbone on July 06, 2013, 03:54:14 PM
I don't think I can agree.  Ice bridge observations earlier this year suggested large areas of ice were considerably thinner than what is being modeled. Unfortunately, we won't be able to get a sense of who's right for a few weeks yet...

Have you got a reference with the detailed calculations for that comparison? My impression was that they were in decent agreement. I read that ice bridge observations noticed thin ice corresponding to refrozen cracks, but that's a lot of thin lines, not a lot of thin area.
Title: Re: Latest PIOMAS update (July)
Post by: jdallen on July 06, 2013, 07:01:06 PM
I don't think I can agree.  Ice bridge observations earlier this year suggested large areas of ice were considerably thinner than what is being modeled. Unfortunately, we won't be able to get a sense of who's right for a few weeks yet...

Have you got a reference with the detailed calculations for that comparison? My impression was that they were in decent agreement. I read that ice bridge observations noticed thin ice corresponding to refrozen cracks, but that's a lot of thin lines, not a lot of thin area.

Someone have the nice Ice Bridge link handy which shows the estimated thickness under their flight paths?  Best way to determine if my perception is wrong.
Title: Re: Latest PIOMAS update (July)
Post by: Jim Pettit on July 06, 2013, 07:53:42 PM
I tried to make a point a few days ago, and may have miscommunicated it, so I hope you don't mind if I try again, only with some simplification--and some new art.

That point was that over the years, total annual volume loss has remained fairly constant, with a yearly average of between 16.5k and 17.0k km3 disappearing from maximum to minimum. The "death spiral" is, thus, not due to increasingly greater melt, but is in fact almost entirely the product of decreasing annual maxima.

That being said, then, I threw together this dual plot showing volume losses from each year's maximum through June 30, and from July 1 through each year's minimum. And it's plain to see that, as the years have gone by, there's increasingly been more of the former and less of the latter. In fact, because of that c. 16.75k km3 average, there exists in most cases a loose inverse relationship: more early melt means less later melt, and vice versa.

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fi.imgur.com%2Fep5uarZ.png&hash=1049d0da1efeb81ed7e921f3f98e8934)

Now, the 2013 volume maximum was the lowest on record yet (though admittedly not by much). And between that maximum and June 30, the amount of ice lost was less than it's been for a number of years. My estimation, then, is that the post-June loss this year will be greater than it's been for a number of years. And because of that, the 2013 volume minimum will be lower than some are predicting. Again, I'm not necessarily saying we'll see a new record (although that's certainly well within the bounds of possibility). I'm just saying that this year will show once again that any "recovery" is purely imaginary.
Title: Re: Latest PIOMAS update (July)
Post by: ChrisReynolds on July 06, 2013, 08:05:36 PM
PIOMAS and IceBridge.
http://farm8.staticflickr.com/7385/9225201142_446243a2e6_o.png (http://farm8.staticflickr.com/7385/9225201142_446243a2e6_o.png)

This isn't the ideal way to do an intercomparison, far from it. But I've yet to motivate myself to get round to programming it, as I hate programming (I like results, but I've not yet been sufficiently motivated by the prospect of these results).

I've used a schematic of IceBridge (IB) thickness transects from here.
http://www.arcus.org/search/seaiceoutlook/2013/june (http://www.arcus.org/search/seaiceoutlook/2013/june)
See 'Pan Arctic'.

This has been scaled and overlaid onto one of my PIOMAS thickness plots. My PIOMAS plot is in 25 cm increments, however 2m is 1.75 to 2m, so each thickness band is the upper limit of the band.

One important point: Note that from March to April there is thickening, the PIOMAS gridded data is monthly average and shows the 'effective thickness' for each grid box.

Beaufort is seen to be 1.5 to 1.75m (dark band along the Alaskan coast) rising to 1.75 to 2m further into the pack. In the same region towards Chukchi greens predominate in IB suggesting around 1.5m, but we don't know whether the flights occurred in early or late April, and as stated above, due to thickening between March and April averages this matters.

There is a suggestion of thicker ice in Beaufort near Banks Island in IB data, but in the central blue pack IB suggests reds and oranges (about 2 to 3m), here PIOMAS is 2.5m and above.

Given the approximate nature of the comparison, I think the two are in reasonable agreement.
Title: Re: Latest PIOMAS update (July)
Post by: ChrisReynolds on July 06, 2013, 09:09:54 PM
Jim,

Considering the volume loss from June 30 to min, using the average from 2007 to 2009 applied to the volume at 30 June 2013 predicts a volume minimum of 3.25k km^3. Whereas using the average volume loss from 2010 to 2012 applied to volume on 30 June 2013 predicts a volume minimum of 4.76k km^3, higher than 2010!

So we're on track to at least meet 2012 volume, which suggests we'll have a similar area/extent record.... But, the situation isn't quite so clear.

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Ffarm8.staticflickr.com%2F7454%2F9210960046_f09dcc0dd8_o.png&hash=b4a30a855092efc4477a31eb6a14113c)

Volume loss from maximum to 30 June for 2013 is between that for 2007 to 2009 and 2010 to 2012. So which camp will 2013 fall into?

I had been going to put this in my recent blog post, but somehow it got published before it was ready, and this got left out, I'll tidy that up tomorrow. But as it's germane to your point:

Call the volume loss from Max to 30 June 'Early'. Call the volume loss from 30 June to Min 'Late'. Calculate the ratio Late/Early. Now plot on a scatter plot as a function of the Early volume loss, and calculate the best fit.

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Ffarm6.staticflickr.com%2F5448%2F9222870161_1e2d200aed_o.jpg&hash=de611b92d0835888e6645963638f525e)

Now the above equation can be used to calculate the ratio of Early and Late given 2013's Early volume loss. After which the ratio can be applied to the Early volume loss of 2013 to calculate what we should expect the Late volume loss of 2013 to be, this can then be subtracted from volume at 30 June 2013.

This method predicts a minimum volume of 4.57k km^2.
Title: Re: Latest PIOMAS update (July)
Post by: ghoti on July 06, 2013, 11:50:42 PM
Isn't plotting a value against a ratio with the same value as the numerator an auto-correlation? As the numerator decreases the ratio also decreases if there is no correlation of the numerator to the denominator ( I think).

If you plot early versus late i'm pretty sure you will not get a significant correlation. This would suggest early melt doesn't predict late melt - within limits after all since if you melt all the ice early the late melt would have to be small.

Interesting either way. I'm just leery of ratios from what I found with them in my plant research many years ago.
Title: Re: Latest PIOMAS update (July)
Post by: ChrisReynolds on July 07, 2013, 09:31:48 AM
Ghoti,

My maths isn't great, but plotting early vs late produces a greater scatter and lower R2 so the increase of R2 may be the autocorrelation at work. The reason I considered it reasonable is that it's the same sort of technique used in Hubbert Linearisation.
http://en.wikipedia.org/wiki/File:HubbertLin_US_Lower48.svg (http://en.wikipedia.org/wiki/File:HubbertLin_US_Lower48.svg)
Title: Re: Latest PIOMAS update (July)
Post by: Richard Rathbone on July 07, 2013, 12:48:28 PM
Ghoti is right. Its ones of the sins my supervisor warned me about.

Hubbert linearisation is a better descriptor than predictor. The results from using it to predict future oil production are a lot poorer than you'd think from looking at the graphical fit. That is partly down to the fit not actually being as good as it looks because the way the variables are plotted enhances it.

If you have good reasons for the expression you are plotting you can use this sort of plot to fit a parameter, but you need to establish that its the right thing to plot by other means first. The reason for using a Hubbert linearisation isn't that its a good fit, but that there are reasonable grounds for expecting oil production to follow a logistic curve.
Title: Re: Latest PIOMAS update (July)
Post by: ChrisReynolds on July 07, 2013, 02:10:35 PM
Thanks Ghoti and Richard,

There is no way to predict, as a straight scatter plot doesn't give a good fit at all. 2010 to 2012 look more like a regime shift, with years before giving a wide scatter.
Title: Re: Latest PIOMAS update (August)
Post by: Wipneus on August 04, 2013, 06:44:07 AM
Updated, graphs are in the top post (https://forum.arctic-sea-ice.net/index.php/topic,119.0.html).
Title: Re: Latest PIOMAS update (August)
Post by: slow wing on August 11, 2013, 04:37:10 AM
I'm wondering if there is going to be a poll for PIOMAS minimum volume?


We already have them for minimum area and minimum extent...  :P

Title: Re: Latest PIOMAS update (August)
Post by: slow wing on August 18, 2013, 03:13:04 PM
It would be fantastic if someone who knows how would be kind enough to do the PIOMAS sea ice thickness maps for the July data...  :)
Title: Re: Latest PIOMAS update (August)
Post by: Dave C on September 01, 2013, 06:23:37 PM
Thanks for keeping all these charts updated. Just a quick suggestion- Your "Monthly Average Arctic Ice Volume" chart would be much easier to read if you divided it into two charts, Oct-Mar and Apr-Sep.
Title: Re: Latest PIOMAS update (August)
Post by: Wipneus on September 01, 2013, 06:52:55 PM
Thanks for keeping all these charts updated. Just a quick suggestion- Your "Monthly Average Arctic Ice Volume" chart would be much easier to read if you divided it into two charts, Oct-Mar and Apr-Sep.
Perhaps I will do something like that (during the freezing season). It is definitely not clearest of graphs.
Title: Re: Latest PIOMAS update (August)
Post by: ChrisReynolds on September 01, 2013, 08:55:35 PM
It would be fantastic if someone who knows how would be kind enough to do the PIOMAS sea ice thickness maps for the July data...  :)

Sorry Slow Wing, missed this when you posted. The gridded data on which thickness maps are based has not been updated since June.
Title: Re: Latest PIOMAS update (August)
Post by: slow wing on September 02, 2013, 04:00:36 AM
Thanks for letting me know, Chris, much appreciated.


The next update is going to be very interesting!
Title: Re: Latest PIOMAS update (September)
Post by: Wipneus on September 06, 2013, 06:43:12 PM
Updated, graphs are in the top post (https://forum.arctic-sea-ice.net/index.php/topic,119.0.html).
Title: Re: Latest PIOMAS update (September)
Post by: dlen on October 08, 2013, 02:25:26 AM
Remark to the yearly min-to-max volume gains:

The amplidude of the ice thickness oscillation is to be expected to increase considerably with decreasing mean thickness, because the winter heat flux is much higher with thin ice. And the ice growth rate depends directly on the heat flux going up into the atmosphere.
But this holds strictly only for areas with no summer melt-out.
In areas with summer melt-out, the thickness oscillation amplitude depends mostly on the iceless time, decreasing with it more and more.
So with the ice becoming thinner, the increasing thickness oscillation in areas with no melt-out and the decreasing thickness oscillation in areas with summer melt-out add up to a volume oscillation amplitude, which increases a little bit, until the summer melt-out becomes too large, then it decreases again.





Title: Re: Latest PIOMAS update (October)
Post by: Wipneus on November 05, 2013, 08:05:41 AM
Updated, monthly graphs are in the top post (https://forum.arctic-sea-ice.net/index.php/topic,119.0.html).

The minimum 2013 value was 4.942 [1000 km3] at September 7.

Yearly minimum fit to exponential trend:

(https://sites.google.com/site/arctischepinguin/home/piomas/grf/piomas-trnd6.png)

Yearly minimum fit to linear trend:

(https://sites.google.com/site/arctischepinguin/home/piomas/grf/piomas-trnd7.png)

Yearly minimum fit to Gomperts trend:

(https://sites.google.com/site/arctischepinguin/home/piomas/grf/piomas-trnd9.png)


Title: Re: Latest PIOMAS update (October)
Post by: jdallen on November 05, 2013, 09:13:37 AM
Thank you Wipneus - marvelous work as typical.

I'd say we are still on track for "ice free" sometime between now and 2020.  Perhaps not by my low end guess (2017), but close.
Title: Re: Latest PIOMAS update (October)
Post by: idunno on November 05, 2013, 12:23:09 PM
Hi Wipneus,

One of us is confused.

AFAICT, PIOMAS has just updated for the figures for September, and October is yet to be released.
Title: Re: Latest PIOMAS update (October)
Post by: Wipneus on November 05, 2013, 01:29:39 PM
Hi Wipneus,

One of us is confused.

AFAICT, PIOMAS has just updated for the figures for September, and October is yet to be released.

Actually I am confused as well. The explanation is this: the monthly update for any month has data normally updated to the last date of the previous month. I am following Neven's standard in the blog here. That last day of the last month can also be regarded as day zero of this month, so at least it makes some sense (to someone at least).

Now hopefully we get the data for October very soon right up to the zeroth of November, so I will call it that the November update and we can forget this confusing episode  ;)
Title: Re: Latest PIOMAS update (November)
Post by: Wipneus on November 16, 2013, 07:43:56 AM
Updated, graphs are in the top post (https://forum.arctic-sea-ice.net/index.php/topic,119.0.html).
Title: Re: Latest PIOMAS update (November)
Post by: ChrisReynolds on November 16, 2013, 08:04:49 AM
Thanks Wipneus.
Title: Re: Latest PIOMAS update (November)
Post by: ggelsrinc on November 16, 2013, 08:42:07 AM
Updated, graphs are in the top post (https://forum.arctic-sea-ice.net/index.php/topic,119.0.html).

Wipneus, I'm not trying to go off subject, but when I click on your links, it's the same certificate error message I once had logging onto this site with https. I easily changed mine to http by staying logged in and switching sites.

This isn't a complaint and just a possible suggestion that may lead to a solution for some people's problems. You may have your reasons for sticking to https, like I did using a proxy server in the past. I think the problem can be solved by registering the security certificate to both website addresses, but I don't know for sure, because I've never been there and done that.

When I click your links, I'm switched to the https site that doesn't have a security certificate.

Does any of that make sense?

 
Title: Re: Latest PIOMAS update (November)
Post by: Wipneus on November 17, 2013, 08:03:22 AM

You may have your reasons for sticking to https, like I did using a proxy server in the past. I think the problem can be solved by registering the security certificate to both website addresses, but I don't know for sure, because I've never been there and done that.


Well, I am using https because the proprietor and the web master (know as user DungeonMaster) asked me to.

I might be wrong, but the web certificate seems to be a matter of costs. No idea how much, but I'd be happy to make a contribution if that is the case.
Title: Re: Latest PIOMAS update (November)
Post by: ChrisReynolds on November 25, 2013, 09:55:04 PM
Regional PIOMAS volume breakdown available as a csv file here:
https://drive.google.com/file/d/0B3pB-kdzoLU3WXpaMWtUTnFJalE/edit?usp=sharing

A set of volume/thickness breakdowns will be calculated, but due to my day job probably not until the weekend.
Title: Re: Latest PIOMAS update (November)
Post by: ChrisReynolds on November 26, 2013, 08:53:02 PM
For completeness,

PIOMAS thickness broken down into regions.
https://drive.google.com/file/d/0B3pB-kdzoLU3RkU4WUZuLXVxeGM/edit?usp=sharing

PIOMAS volume and thickness broken into regions for Excel 2007 and later. Contains user selectable tables breaking down into region and month. Contains VBA code used to process in 'module 2' of the VBA tree.
https://drive.google.com/file/d/0B3pB-kdzoLU3NlhLSno2aVk0Q0U/edit?usp=sharing
Title: Re: Latest PIOMAS update (December)
Post by: Wipneus on December 04, 2013, 08:06:17 AM
Updated, graphs are in the top post (https://forum.arctic-sea-ice.net/index.php/topic,119.0.html).

Interesting, the "pause" in the extent increase beginning of November is reflected in the volume increase as well.
Title: Re: Latest PIOMAS update (December)
Post by: ChrisReynolds on December 06, 2013, 05:54:01 PM
Wipneus,

I've been working again on grid areas for PIOMAS for the last few days. Your calculation (if you remember) was

(HTN+HUS)/2 * (HTE+HUW)/2

Which gives the closest to the main PIOMAS series you can get with the data in grid.dat.pop.

I've not been able to improve on that so have contacted Dr Zhang. It turns out that HUS and HUW are vector quantities, so instead of using those figure from grid.dat.pop we should have calculated by obtaining the other edges (HUS and HUW) from adjacent grid cells. That's the method Dr Zhang uses.

So with an array Grid(1 to 120, 1 to 360,XXX), where XXX is for example HTN or HTE the grid cell area is calculated as:

(Grid(n,m,HTN)+Grid(n-1,m,HTN))/2 * (Grid(n,m,HTE)+Grid(n,m-1,HTE))/2

Using this the error drops to about 0.01%, including the landmask in calculations drops the error far lower (can't remember the figure but it's orders of magnitude - Excel tied up right now checking results).

I'll post on my blog and include a link to the revised grid cell area mask in the next couple of days. But I'm going to try to remove some more of the error first.
Title: Re: Latest PIOMAS update (December)
Post by: Wipneus on December 06, 2013, 07:05:00 PM
... we should have calculated by obtaining the other edges (HUS and HUW) from adjacent grid cells. That's the method Dr Zhang uses.

So with an array Grid(1 to 120, 1 to 360,XXX), where XXX is for example HTN or HTE the grid cell area is calculated as:

(Grid(n,m,HTN)+Grid(n-1,m,HTN))/2 * (Grid(n,m,HTE)+Grid(n,m-1,HTE))/2


Great, although the differences are small it was not nice not to know the reason why.

Thanks.

Title: Re: Latest PIOMAS update (December)
Post by: ChrisReynolds on December 06, 2013, 07:09:54 PM
My attitude had been that -0.6% was acceptable in view of PIOMAS uncertainties.

But to get it so much closer is so much better.  ;D
Title: Re: Latest PIOMAS update (December)
Post by: Wipneus on December 22, 2013, 08:15:24 AM
Gridded thickness data was updated until November 2013 as well.

Attached are thickness differences with 2012, to compare with Cryosat-2.
Title: Re: Latest PIOMAS update (December)
Post by: Wipneus on December 22, 2013, 09:50:59 AM
Here are the thickness maps for October and November:

Title: Re: Latest PIOMAS update (December)
Post by: Neven on December 22, 2013, 10:11:21 AM
Nice work, as always, Wipneus.
Title: Re: Latest PIOMAS update (December)
Post by: crandles on December 22, 2013, 01:55:21 PM
Very interesting Wipneus, thank you.

My view /summary:

Red area by Ellesmere island won't melt out in 2014 anyway. There are large areas - Beaufort round to East Siberian and Central Arctic where thickness already seems to be regressing back to 2012 thicknesses.

There is a build up of extra thickness in Barents - this is probably what would be anticipated looking at extent and area products. Bering isn't covered but there is clearly less ice there from area and extent products. It would be unusual if there wasn't a case of a bit more on one side and a little less on another side.

While that summary sound much like all very much as expected, it is interesting to see. It seems quite early for to me for such large areas to already be showing such marked regression towards 2012 thicknesses.

Maybe other people see different things or have different opinions?

Nice to have it so up to date. :)
Title: Re: Latest PIOMAS update (December)
Post by: ChrisReynolds on December 22, 2013, 02:16:09 PM
Thanks Wipneus,

You ended up beating me to it anyway. Here's my blog post on the data:
http://dosbat.blogspot.co.uk/2013/12/new-piomas-gridded-data-november-2013.html (http://dosbat.blogspot.co.uk/2013/12/new-piomas-gridded-data-november-2013.html)
Title: Re: Latest PIOMAS update (December)
Post by: Wipneus on January 05, 2014, 02:08:57 PM
The PIOMAS daily update is not in yet, but for the first time the gridded monthly data has come first!

The difference between 2013 and 2012 is slowly getting less (September-December 2013 vs 2012):

1661  1937  1865  1689 km3

Attached are maps of thickness in Dec 2012 and Dec 2013, and the differences.
Title: Re: Latest PIOMAS update (December)
Post by: crandles on January 05, 2014, 03:07:22 PM
Thanks Wipneus, that is great.

Is a difference map between the November differences and the December differences difficult to produce?

Title: Re: Latest PIOMAS update (December)
Post by: Wipneus on January 05, 2014, 05:27:21 PM
Thanks Wipneus, that is great.

Is a difference map between the November differences and the December differences difficult to produce?

No it is not difficult to produce.

You ask for the following:

(thickness.dec.2013 - thickness.dec.2012) -(thickness.nov.2013 - thickness.nov.2012)

but this is the same as

(thickness.dec.2013 - thickness.nov.2013) -(thickness.dec.2012 - thickness.nov.2012)

Which I prefer to call difference of nov-dec growth.

Attached.
Title: Re: Latest PIOMAS update (December)
Post by: crandles on January 05, 2014, 08:12:33 PM
Thanks Wipneus :)

So more mechanical thickening by Greenland and Canada. Elsewhere over large areas there is less growth and this seems pretty much regardless of whether ice was thicker or thinner than last year. In Kara and Barents there is thicker ice which is thickening faster but thicker ice seems an unlikely cause for this.

If relative ice thickness does not seem to be a major driver, what is/are?

Warmer weather this year than last? More snow insulation? Higher upward heat flux? Less area of leads preventing heat escaping easily? Other factors?

Title: Re: Latest PIOMAS update (December)
Post by: jdallen on January 05, 2014, 08:49:20 PM
Thanks Wipneus :)

So more mechanical thickening by Greenland and Canada. Elsewhere over large areas there is less growth and this seems pretty much regardless of whether ice was thicker or thinner than last year. In Kara and Barents there is thicker ice which is thickening faster but thicker ice seems an unlikely cause for this.

If relative ice thickness does not seem to be a major driver, what is/are?

Warmer weather this year than last? More snow insulation? Higher upward heat flux? Less area of leads preventing heat escaping easily? Other factors?

A number of the buoys are reporting significant snow cover - as much as a meter.  This would retard thickening.
Title: Re: Latest PIOMAS update (January)
Post by: Wipneus on January 07, 2014, 07:35:01 AM
Updated, graphs are in the top post (https://forum.arctic-sea-ice.net/index.php/topic,119.0.html).
Title: Re: Latest PIOMAS update (January)
Post by: Jim Pettit on January 07, 2014, 05:11:40 PM
Thanks, Wipneus. FWIW, I've updated my SIV graphs with the December PIOMAS figures:

https://sites.google.com/site/pettitclimategraphs/pettit-climate-graphs (https://sites.google.com/site/pettitclimategraphs/pettit-climate-graphs)

(3D volume graphs can be found here (http://"https://sites.google.com/site/pettitclimategraphs/pettit-climate-graphs/3d").)
Title: Re: Latest PIOMAS update (January)
Post by: Buddy on January 07, 2014, 06:26:30 PM
This is NOT setting up to a good year for the Arctic.  Things can change.....but this does NOT look good.
Title: Re: Latest PIOMAS update (January)
Post by: werther on January 07, 2014, 08:33:22 PM
Hi Buddy,
I felt "not good" on climate change/AGW for years. And very worried last winter.

But some parameters give me at least some spare time to see if the situation for this year will indeed be "NOT GOOD".
Now that PIOMAS December is in, it is clear that volume is not rejoining the '10-'12 trend for some time. Reynolds suggested that part of the conserved/not molten CAB volume may stack into a higher portion of MYI at the start of this melt-season.

That doesn't mean the outcome of a brutal summer will be less than dramatic. We'll see. If the weird circulation goes on, teams up with a new El Nino and so on, NOT GOOD will be an understatement.
Title: Re: Latest PIOMAS update (January)
Post by: Buddy on January 07, 2014, 09:06:26 PM
My biggest concern (other than a lack of intelligence in the US Congress:) is the "seemingly" growing number of heat anomalies in the sea surface temperatures.  More "warm anomalies" have been popping up over the past couple of months.  And of course.....the area off of southern Greenland is warmer than usual. 

http://climatechangegraphs.blogspot.com/2013/02/sea-surface-temperature-anomaly-weekly.html (http://climatechangegraphs.blogspot.com/2013/02/sea-surface-temperature-anomaly-weekly.html)

As well.....the western US is dry....dry....dry.  Climate.....as I have found out over the last 5 years....is one tricky puzzle, with a lot of interacting parts.  But as you folks all know too well.....the number of parts that are looking worse and worse over time........is growing.  Not only growing, but literally growing right in front of our eyes.  NOT GOOD....

The Arctic and Greenland are just two of the bigger canaries in the proverbial coal mine.   If the ice sheet level in the Arctic continues its near/at record level into the beginning of melt season in April.....it will not be a pretty thing.

       
Title: Re: Latest PIOMAS update (January)
Post by: jdallen on January 07, 2014, 09:16:31 PM
@Buddy - you are echoing me last year at this time.  However, to the surprise of us all, the ice did not crash.  The crucial period appears to be early to mid spring.

That notwithstanding, the anomalous weather events are multiplying.  Change is happening.  It will not be prompt, nor consistent, even with a "melt out".  That will just be another signal, if a dramatic one, but far less ominous than the changes to weather patterns in the mid latitudes which have already started.
Title: Re: Latest PIOMAS update (January)
Post by: deep octopus on January 07, 2014, 10:15:54 PM
The below-average snow coverage in Europe is on watch for me. This is compounded by models which project a very warm late winter/early spring for Europe and western Siberia.
https://lh5.googleusercontent.com/-VUmsaYV62iY/Usxq7rUl7WI/AAAAAAAAAPc/-YmmcZD1bH4/w1018-h787-no/glbT2mSeaInd1.gif

If snow melt gets ramped up early and quickly, I suppose the sea ice could get a rude awakening by April. However, like jdallen, in March of last year, it appeared to me that what looked like a rapid ice loss event in the making was was soon stymied by unexpected changes in weather patterns. But we do have some interesting circumstances taking shape (the snow/early spring situation being one.)
Title: Re: Latest PIOMAS update (January)
Post by: ritter on January 08, 2014, 05:23:39 PM
@Buddy - you are echoing me last year at this time.  However, to the surprise of us all, the ice did not crash.  The crucial period appears to be early to mid spring.

Well, not in the summer at least. It's waited until December/January to get to new lows.....  :o
Title: Re: Latest PIOMAS update (January)
Post by: Wipneus on February 05, 2014, 11:21:42 AM
PIOMAS gridded thickness data has been updated, again ahead of the official non-gridded data.

My estimate for January 2014 is 17.300 km3 which brings it at the 4th lowest place, just below 2010 but above 2011, 2012 and 2013.

Preparing some maps...
Title: Re: Latest PIOMAS update (January)
Post by: Wipneus on February 05, 2014, 11:30:20 AM
Here are thickness maps for January 2013 and 2014, and a map of the differences between them.
Title: Re: Latest PIOMAS update (January)
Post by: KielFish on February 05, 2014, 11:42:11 AM
Hi Wipneus,

Thanks for making those maps. I would like to play around with the data myself but I have a bit of confusion over the datasets. Whilst attempting to get the gridded PIOMAS data (from here: ftp://psc.apl.washington.edu/zhang/IDAO/retrospection/) I found two files: heff.H2013.gz and heff.txt2013.gz (using 2013 as an example). Am I correct to assume that these are the same datasets? In which case, the text file seems much more user-friendly - despite my best efforts I cannot understand the data structure of the first file.
Title: Re: Latest PIOMAS update (January)
Post by: Wipneus on February 05, 2014, 11:44:00 AM
And the difference between the growth from December to January and  the growth last year.
Title: Re: Latest PIOMAS update (January)
Post by: Wipneus on February 05, 2014, 12:05:13 PM
Hi Wipneus,

Thanks for making those maps. I would like to play around with the data myself but I have a bit of confusion over the datasets. Whilst attempting to get the gridded PIOMAS data (from here: ftp://psc.apl.washington.edu/zhang/IDAO/retrospection/) I found two files: heff.H2013.gz and heff.txt2013.gz (using 2013 as an example). Am I correct to assume that these are the same datasets? In which case, the text file seems much more user-friendly - despite my best efforts I cannot understand the data structure of the first file.

Yes they should be the same. Yet the resolution is one centimeter, the binary files could be more accurate. Also the 2014 data seems to be available only as a binary.

As documentation the read_hi_uice.f is to be used, if that helps.

My programs are written in R, if you could use that let me know. Another frequenter here, Chris Reynolds does everything in Excel he may be able to help as well.
Title: Re: Latest PIOMAS update (January)
Post by: werther on February 05, 2014, 12:15:52 PM
And the difference between the growth from December to January and  the growth last year.

Those two graphs look the same, Wipneus... it's not immediately clear to me what to make of them...
Title: Re: Latest PIOMAS update (January)
Post by: Wipneus on February 05, 2014, 12:37:43 PM
Something went a bit wrong:
The first time I pressed "Post", I got a warning from another post. Then I pressed "Post" again, at that time the attachment was gone. So I attached again  and now I have two attachments.

There should be only one image now, thanks for noticing.
Title: Re: Latest PIOMAS update (January)
Post by: KielFish on February 05, 2014, 03:16:50 PM
Thanks for the clarification Wipneus, I think I can use my own tools to process the data from the text files for now. I do a bit of web development and would like to make some interactive thickness maps using the PIOMAS data. I have some good ideas on how it may work but needed to get the data into a suitable format first - the first stumbling block of many I'm sure. Will keep you updated if anything comes of it.
Title: Re: Latest PIOMAS update (January)
Post by: ChrisReynolds on February 05, 2014, 07:30:58 PM
Kielfish,

You'll find metadata extracted from the gridded data here at my blog.
http://dosbat.blogspot.co.uk/2013/12/regional-piomas-volume-data.html (http://dosbat.blogspot.co.uk/2013/12/regional-piomas-volume-data.html)
There's volume broken down into regions, regional breakdown of a breakdown of volume contribution from various thickness bands (thickness of grid cell in a given month), and regional average thickness. Thickness doesn't exactly tally with the PIOMAS thickness series.

On that page you'll also find an explanation of how to calculate grid cells.

A correspondent of mine (email) has been having problems with the text files, for a start they don't contain enough elements to cover the entire PIOMAS domain. but as I use the binaries I can't advise further than that note of caution.

In case it's of use (i.e. you do decide to tackle the binaries) here is the Excel Visual Basic code core I use to populate arrays with gridded data, e.g. thickness .heff files, and a shadow array containing necessary overhead data for each grid point. If you need the binary files for grid cell area or region mask just ask, the lattitude and longitude are available here (you'll need scalar - grid.dat), which you already know about:
http://psc.apl.washington.edu/zhang/IDAO/data_piomas.html (http://psc.apl.washington.edu/zhang/IDAO/data_piomas.html)
(That's for other readers really)

'***************************Data Acquisition Functs/Subs******************************

Private Sub LoadData(DataArray() As Single, DataIndex As String, MonthIndex As Integer, YearIndex As Integer)

Dim n As Long
Dim Word As Single
Dim URLstring As String

Select Case DataIndex
   Case "Thick"
   FileID = "heff.h"
   FolderID = "Thickness\"
   MinYear = 1978
   MaxYear = 2013
   Case "Conc"
   FileID = "area.h"
   FolderID = "Concentration\"
   MinYear = 1978
   MaxYear = 2012
   Case "Grow"
   FileID = "icegrow.h"
   FolderID = "Growth Rate\"
   MinYear = 1978
   MaxYear = 2004
   Case "OFlux"
   FileID = "Oflux.h"
   FolderID = "Ocean Flux\"
   MinYear = 1978
   MaxYear = 2004
   Case Else
   Debug.Print "*****LoadData terminated - no such category***************"
   End
End Select

If YearIndex < MinYear Then
   Debug.Print "*****LoadData terminated - Invalid Year = "; YearIndex
   End
End If
If YearIndex > MaxYear Then
   Debug.Print "*****LoadData terminated - Invalid Year = "; YearIndex
   End
End If

'make the URL for the source file
URLstring = "C:\Users\Computer\Documents\PIOMAS\Data\" + FolderID + FileID + CStr(YearIndex)

'open the source file
Open URLstring For Binary Access Read As #1
   
'load DataArray from file - 43200 data points for each month, 12 months per file.
   For Lat = 1 To 120
     For Lon = 1 To 360
      Get #1, (Lat - 1) * 1440 + 1 + (Lon - 1) * 4 + (MonthIndex - 1) * 172800, Word
      DataArray(Lat, Lon) = Word
     Next Lon
   Next Lat

Close #1

Debug.Print "Source Data loaded OK ", Time()

End Sub




Private Sub LoadGridPoints(GridArray() As Single)
'GridArray is a 3d array, first 2 indices are grid number lat and lon as index, second is 1=longitude,
                          '1=latitude (actual lat and lon of grid box), 3=area, 4=region, 5=LandMask
                          'declare as Dim GridArray(1 To 120, 1 To 360, 1 To 5) As Single

Dim Word As Single
Dim InByte As Byte
Dim n As Long
Dim LandMaskString As String

Open "C:\Users\Computer\Documents\PIOMAS\Data\Lat.bin" For Binary Access Read As #1
Open "C:\Users\Computer\Documents\PIOMAS\Data\Lon.bin" For Binary Access Read As #2
Open "C:\Users\Computer\Documents\PIOMAS\Data\GridArea.bin" For Binary Access Read As #3
Open "C:\Users\Computer\Documents\PIOMAS\Data\Region.bin" For Binary Access Read As #4
Open "C:\Users\Computer\Documents\PIOMAS\Data\io.dat_360_120.output" For Input As #5

'Load Lat and Lon into strings

'Load Land mask into string
Input #5, LandMaskString

'Load Grid lat and lon and area.
For Lat = 1 To 120
 For Lon = 1 To 360
   'load longitude
     Get #1, , Word
     GridArray(Lat, Lon, 1) = Word
   'load latitude
     Get #2, , Word
     GridArray(Lat, Lon, 2) = Word
   'load area
     Get #3, , Word
     GridArray(Lat, Lon, 3) = Word
   'Load Region Code
     Get #4, , InByte
     GridArray(Lat, Lon, 4) = InByte
   'Load Land Mask, 1 = sea -1 = land
     If Mid(LandMaskString, (((Lat - 1) * 360 + Lon) * 2) - 1, 2) > 0 Then
      GridArray(Lat, Lon, 5) = 1
     Else
      GridArray(Lat, Lon, 5) = -1
     End If
  Next Lon
Next Lat

'close source files
Close #1
Close #2
Close #3
Close #4
Close #5

Debug.Print "Grid Data loaded OK ", Time()

End Sub
Title: Re: Latest PIOMAS update (January)
Post by: ChrisReynolds on February 05, 2014, 07:35:33 PM
Thanks Wipneus,

Guess I'd better do a blog post tonight...

Although I may just watch a film.  ;D
Title: Re: Latest PIOMAS update (January)
Post by: ChrisReynolds on February 05, 2014, 11:06:54 PM
Loads of graphs in my January post, for those who like such things.
http://dosbat.blogspot.co.uk/2014/02/piomas-january-2014.html (http://dosbat.blogspot.co.uk/2014/02/piomas-january-2014.html)
Title: Re: Latest PIOMAS update (January)
Post by: ChrisReynolds on February 06, 2014, 08:10:24 AM
There's been a change to the PIOMAS gridded data, I've not yet checkd the main daily series.

Graphs in the above blog post will be updated when I get back from work. The spring volume loss and 2010 volume loss remains. But the 2013 volume gain is less, and minimum volume for sept 2012 is greater.
Title: Re: Latest PIOMAS update (January)
Post by: Wipneus on February 06, 2014, 08:29:32 AM
Indeed, I had expected the official daily PIOMAS data would be available by now so I waited.

But:
Gridded data has changed substantially for 2009-2013;
For instance minimum 2012 is now about 3.76, was 3.37 [1000 km3];
max difference (June 2013) 1.43 [1000 km3];
all differences from 2010-2013 are positive: ice is thicker;

Will the change in gridded data also be seen in the non-gridded data? Is a new release (v3) to be announced?

We will have to wait a bit longer.
Title: Re: Latest PIOMAS update (January)
Post by: crandles on February 06, 2014, 12:37:24 PM
The 15 June 2011 new version (v2) section says

The long term trend is reduced to about -2.8 103 km3/decade from -3.6 km3 103/decade in the last version. Our comparisons with data and alternate model runs indicate that this new trend is a conservative estimate of the actual trend.  New with this version we provide uncertainty statistics. More details can be found in Schweiger et al. 2011.  Model improvement is an ongoing research activity at PSC and model upgrades may occur at irregular intervals.  When model upgrades occur, the entire time series will be reprocessed and posted.

Sounds like the trend is reduced again despite last trend being conservative. If the volume keeps being adjusted upwards and the trend reduced, then it allows more time for a long tail as shown by models to make an appearance.
Title: Re: Latest PIOMAS update (January)
Post by: Wipneus on February 06, 2014, 12:59:20 PM
A revision that only affects 2009-2010 sounds that some input data is revised. It cannot be Cryosat-2, if it would be all long term trends would be suspicious.

Here are the estimated differences (new - old) per month:

   ---2010 -----2011 ------2012 -------2013
jan 130.9539 226.3197  597.5953  627.5944
feb 389.9285 329.3752  761.9594  846.4948
mar 553.0858 426.7384  971.5580  965.6704
apr 711.5166 589.9611 1251.2395 1299.9121
may 849.3467 786.4040 1414.8699 1431.0550
jun 617.8464 654.0335 1102.3938 1113.6824
jul 429.6737 485.5981  796.5020  755.9716
aug 224.9569 355.0028  528.3009  530.1337
sep 130.9260 242.2494  387.0746  403.8874
oct 101.2592 185.9627  337.7706  335.4152
nov 125.9876 212.0406  338.1416  313.2785
dec 220.8414 403.0042  455.7761  397.5223
Title: Re: Latest PIOMAS update (January)
Post by: jdallen on February 06, 2014, 06:28:26 PM
The 15 June 2011 new version (v2) section says

The long term trend is reduced to about -2.8 103 km3/decade from -3.6 km3 103/decade in the last version. Our comparisons with data and alternate model runs indicate that this new trend is a conservative estimate of the actual trend.  New with this version we provide uncertainty statistics. More details can be found in Schweiger et al. 2011.  Model improvement is an ongoing research activity at PSC and model upgrades may occur at irregular intervals.  When model upgrades occur, the entire time series will be reprocessed and posted.

Sounds like the trend is reduced again despite last trend being conservative. If the volume keeps being adjusted upwards and the trend reduced, then it allows more time for a long tail as shown by models to make an appearance.

I would caution here... Beware the exponential function.  Higher numbers may not indicate an emerging "tail" so much as they indicate 1 or 2 two more years of grace before a thorough crash.

I would also add higher numbers now do not preclude higher numbers *earlier*; this revision suggests to me that it is possible they started higher (40 years ago) and have fallen farther.
Title: Re: Latest PIOMAS update (January)
Post by: ChrisReynolds on February 06, 2014, 06:43:32 PM
It is fascinating how the increase in volume on previous years is concentrated during the early summer and spring melt. Yet (and I've just double checked) this has not removed the post 2010 spring melt anomaly - I've yet to compare the spring melt in both datasets (old and new).

I've also copied the new data into my spreadsheet on the Spring Melt, which I used to calculate and graph for my recent blog post on that. The conclusions of that post remain, however the role of the Central Arctic is reduced very slightly with Beaufort and the CAA joining in to a greater degree.

What I can't understand is this - volumes over the spring melt have gone up with the new data. BUT the spring melt seems to be greater in this new data.

I'll post more after I've eaten.
Title: Re: Latest PIOMAS update (January)
Post by: Neven on February 06, 2014, 07:21:34 PM
Will the change in gridded data also be seen in the non-gridded data? Is a new release (v3) to be announced?

Or could it be that it's taking a bit longer because someone can't be bothered to make new graphs with 2014 trend lines?  ;D
Title: Re: Latest PIOMAS update (January)
Post by: ChrisReynolds on February 06, 2014, 07:50:53 PM
I'm going to have a night off because I was up late last nnight with this, and have a long day tomorrow, so I'm going to be cheap and post the core of what I've just emailed to someone.

I've just been doing some calculations and graphs.

1) The new April volume is significantly higher than the old data.

2) The new September volume is very close to the old data.

3) This causes the melt season range to increase much more than previously.The 2012 melt season lost 18357.35km^3 by the old data, for the new data that rises to 19333.64km^3.

4) The 2010 volume loss drops from 2398.46 (Sept minus previous Sept) to 2182.76, 2010 remains one of a small number of massive volume loss events, 2007 being the one preceding (2587.07km^3).

5) The post 2010 anomalous spring volume loss remains, but there's a greater role for the seas from Beaufort to Kara, actually the spring melt has increased with the new data! My first thought had been that it was going to be removed.

6) The central Arctic region is the largest source of the volume increase from old to new.


I'll probably do a proper blog post about this over the weekend, but may email Dr Zhang before I blog. I'm waiting because there may be an announcement at the PIOMAS main series web page, and I don't want to bother Dr Zhang when I know he'll be busy.
Title: Re: Latest PIOMAS update (January)
Post by: jdallen on February 06, 2014, 08:09:33 PM
So, if I understand Chris' analysis, it would appear season to season volume changes are more volatile than we previously thought.  In my view, that makes the new numbers more disturbing, rather than less.
Title: Re: Latest PIOMAS update (January)
Post by: ktonine on February 06, 2014, 10:15:42 PM
Chris:
5) The post 2010 anomalous spring volume loss remains, but there's a greater role for the seas from Beaufort to Kara, actually the spring melt has increased with the new data! My first thought had been that it was going to be removed.

That's exactly what my first thought was :)

Title: Re: Latest PIOMAS update (January)
Post by: ChrisReynolds on February 06, 2014, 10:26:01 PM
I strongly disagree JD,

The increased winter volume actually takes us back to the Tietsche effect, or the process dominating winter ice growth, it seems to be marginally stronger in recent years than the old version. Summer losses are about the same, winter gains from those losses are higher in recent years.

If anything I'd say whatever the change is it indicates marginally more stability.

I've attached some rough graphs, the one with 4000 at the top scale is for April, the one with 6000 at the top is for September, volume is anomaly from 1980 to 1999 average, shown in km^3.
Title: Re: Latest PIOMAS update (January)
Post by: ChrisReynolds on February 06, 2014, 10:28:12 PM
Chris:
5) The post 2010 anomalous spring volume loss remains, but there's a greater role for the seas from Beaufort to Kara, actually the spring melt has increased with the new data! My first thought had been that it was going to be removed.

That's exactly what my first thought was :)

I'm normally in bed between 2100 and 2200, last night just before bed I checked my emails, found this out and was up late - I had to work it out before I could sleep. I was (as we say in the UK) "having kittens".

Turned out alright.  8)
Title: Re: Latest PIOMAS update (January)
Post by: jdallen on February 07, 2014, 01:12:41 AM
@ Chris - noted, but I'm skeptical.  Partly, if I understand what I see correctly, with about the same September value, but higher April value, more rather than less ice was lost during the melt season than shown previously, even if the end point was higher than the previous year.

That suggests greater volatility <within> the melt season. That is one of the possibilities I was getting at.  The other was, that the same modifications have not been applied to earlier data (I.e., the 1980-2000 values). Are we sure those numbers might not increase as well? If so, one might be able to conclude the loss over time has been more rather than less dramatic.

I presume we have numbers for total loss from maximum and total gain from minimum? Contrasting those values rather than the end points might be useful.
Title: Re: Latest PIOMAS update (January)
Post by: jdallen on February 07, 2014, 01:32:10 AM
Here's a couple of $64 questions to ponder in addition.

Are the heat inputs into the arctic during the refreeze becoming sufficient to positively balance the additional loss due to increasingly greater Tietsche effect?

Is there an upper limit / diminishing returns characteristic to the Tietsche effect which will result in more heat being retained as total sensible heat increases past some predictable level?

Im going to see if I can download numbers and do a bit of my own graphing.
Title: Re: Latest PIOMAS update (January)
Post by: Wipneus on February 07, 2014, 06:32:57 AM
More updates in the gridded data sets: also ice velocity and snow thickness data files are updated.

This time its not 2009-2013 but all years (1979-2013) are affected.
Title: Re: Latest PIOMAS update (January)
Post by: ChrisReynolds on February 07, 2014, 05:52:47 PM
Wipneus,

I suspect another version is being released. I'll wait to see if there's an announcement before I go bothering Dr Zhang - he must be busy - actually maybe I'll email Dr Schweiger - Done, just emailed him, hoping for a reply before the weekend starts in the US.

I suspect some of those indices are being extended past 2004 when previously they weren't - but I haven't kept close notes on that.

JD Allen,

It'll be a hell of a job for you to try to get numbers out of that binary data. I'll post you some text files with old and new monthly volumes from 1978 to jan 2014, it's a five minute job for me. But bear in mind my comment above, further and earlier changes may happen.
Title: Re: Latest PIOMAS update (January)
Post by: Wipneus on February 07, 2014, 06:43:50 PM

I suspect some of those indices are being extended past 2004 when previously they weren't - but I haven't kept close notes on that.

No, they where available until 2012.
Title: Re: Latest PIOMAS update (January)
Post by: ChrisReynolds on February 07, 2014, 06:49:52 PM
Thanks Wipneus,

They've found a bug and are in the process of reworking what is affected, the main daily and monthly timeseries should not change. I've asked Dr Schweiger or Dr Zhang to let me know when the data is 'stable' so I can pass the message on.
Title: Re: Latest PIOMAS update (January)
Post by: ChrisReynolds on February 07, 2014, 07:10:51 PM
EDIT - data removed from this and put in a csv file attached.

If the main series isn't going to change then based on the data so far, I've attached the resultant errors between the main monthly series and the new gridded dataset, it's a serious problem as it stands, I just hope that what's been uploaded is an interim.

I can't see how the gridded can change without a change to the main series...

JD Allen, you'll find new and old volume data series attached.

Key
PIOMASGriddedNEW.txt = New gridded volume in km^3
PIOMASGriddedOLD.txt = Old gridded volume in km^3
PIOMASNewVsMainError.txt = The percent error between the new gridded data total volume and the PIOMAS monthly timeseries (counterpart to the more usually used daily volume dataset.
PIOMASOldVsMainError.txt = as above but percent error with respect to old gridded volume data.
Title: Re: Latest PIOMAS update (January)
Post by: ChrisReynolds on February 07, 2014, 07:46:15 PM
Axel has emailed me. He'll let us know when the data is stable and no further changes are expected. I've emailed him the error files attached in my previous message - just in case they thought what was uploaded was OK.

I'm leaving this matter for now.
Title: Re: Latest PIOMAS update (January)
Post by: Neven on February 07, 2014, 09:57:22 PM
Thanks for looking into this, ChrisR and Wipneus.
Title: Re: Latest PIOMAS update (January)
Post by: jdallen on February 07, 2014, 11:12:42 PM
@Chris - Thanks!

I'll pull down the data and see if I can do something sensible with it.  Hopefully it will help me articulate more clearly, or show me that my assumptions are flawed.
Title: Re: Latest PIOMAS update (January)
Post by: Wipneus on February 08, 2014, 07:32:52 AM
You may have a look at the changes at the arctic sea ice volume page of PSC/APL (http://psc.apl.washington.edu/wordpress/research/projects/arctic-sea-ice-volume-anomaly/) putting the 2013 "recovery" in perspective.

About the bug discovered and the new version 2.1:

Version 2.1

We identified a programming error in a routine that interpolates ice concentration data prior to assimilation. The error only affected data from 2010-2013. These data have been reprocessed and are now available as version 2.1. Ice thickness is generally greater in the Beaufort Chukchi Sea area with the largest differences in thickness during May. Differences in ice volume are up to 11% greater in late spring.

Fig 5. shows the differences in volume between Version 2.0 and Version 2.1 (click to enlarge)

This is fig 5:

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fpsc.apl.washington.edu%2Fwordpress%2Fwp-content%2Fuploads%2Fschweiger%2Fice_volume%2Fversion_diff.png&hash=0461557aa7a990a6cbbc029a7f3fe82f)

It will take some time to update my own graphics.
Title: Re: Latest PIOMAS update (January)
Post by: jdallen on February 08, 2014, 11:21:48 AM
So on short, in net, we have more ice at the end of the refreeze, and greater total melt during the summer (higher end of summer values not withstanding...)
Title: Re: Latest PIOMAS update (February)
Post by: ChrisReynolds on February 08, 2014, 11:36:14 AM
JD Allen, Yes.

Wipneus,
So it looks like they have had to do a version change, thanks for the heads up. I'll get onto this later today and do a blog post. It does of course mean that now you can tell people what I relayed to you.  ;)
Title: Re: Latest PIOMAS update (February)
Post by: Wipneus on February 08, 2014, 11:37:15 AM
I have updated for version 2.1, graphs are in the top post (https://forum.arctic-sea-ice.net/index.php/topic,119.0.html).

I am dropping the daily volume graph with "expected" values based on exponential trends. Look at the monthly graph to see how that fit will go in the future.

BTW as a result of the version bump the trends have changed only slightly, especially when taking uncertainty into account. The exponential extrapolation to exactly zero, which was affected most, shifted upward 0.5 years (2016.44 to 2016.94).
Title: Re: Latest PIOMAS update (February)
Post by: ChrisReynolds on February 08, 2014, 12:13:51 PM
I'll check those out Wipneus.

Using the Zhang Method for calculating grid area left an odd error during 2010 of the order of 0.1% peak. Now with the new release V2.1, the difference between V2.1 and the gridded data is generally no more than 0.01% (two instances of 0.02%), orders of magnitude below the uncertainty. The average of errors from 1979 to 2013 is 0.00%.

 :)

Title: Re: Latest PIOMAS update (February)
Post by: crandles on February 08, 2014, 12:26:05 PM
V2.1 numbers:

:
Year 2009 2010 2011 2012 2013 2014
Day
31 20.397 19.222 17.938 18.432 17.733 18.938
59 22.837 21.929 20.459 20.707 20.903
90 24.613 24.053 22.129 22.889 22.85
120 24.886 23.752 22.282 23.099 22.828
151 22.431 20.229 19.483 19.591 20.498
181 16.563 13.458 12.917 12.295 14.04
212 9.813 7.405 6.979 6.676 7.795
243 7.235 4.838 4.607 3.932 5.574
273 6.938 5.138 4.789 3.967 5.743
304 9.13 7.71 7.085 6.417 8.593
334 12.369 11.114 11.139 10.138 11.859
365 15.951 14.657 15.012 13.921 15.78
Title: Re: Latest PIOMAS update (February)
Post by: crandles on February 08, 2014, 01:10:23 PM
Monthly averages:

:
Year\Mon Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
1979 27.79083 30.13017 32.09870 32.95703 32.25320 29.72177 23.43953 18.29870 16.90950 17.90847 20.16490 23.30550
1980 26.62823 29.11007 31.18200 32.24393 31.77200 29.08083 22.64780 17.68010 16.31937 17.36893 19.46690 22.54833
1981 25.40183 27.73363 29.87433 30.74993 29.98493 26.73807 19.94377 14.50943 12.81307 14.01323 16.18420 19.21503
1982 22.74390 25.44080 27.72203 28.97830 28.25477 25.54923 19.45370 14.73503 13.50987 14.98760 17.81400 21.17177
1983 24.55817 27.23163 29.43987 30.39653 30.14207 27.69167 21.64400 16.62270 15.20130 16.49330 18.99657 22.06337
1984 24.81127 27.16240 29.20830 30.33870 29.77597 27.02227 20.72660 16.05167 14.63357 15.71733 18.14173 21.39590
1985 24.74227 27.22300 29.51907 30.87797 30.47717 27.40797 20.54373 15.91990 14.58363 15.90203 18.32980 21.38347
1986 24.78877 27.47140 29.83887 30.94293 30.41680 27.79283 21.75230 17.19630 16.08027 17.44370 19.89767 22.83633
1987 26.12760 28.79387 30.71610 31.80093 31.47223 28.74080 22.04380 16.59537 15.36090 16.76263 19.29937 22.39627
1988 25.56770 28.09187 30.33923 31.20247 30.16067 27.15583 20.89300 16.23060 14.98800 16.31443 18.97037 22.22933
1989 25.46413 27.80523 29.46400 30.11623 29.58840 27.05423 20.86433 16.09443 14.76910 16.01107 18.69967 21.89347
1990 25.06250 27.58527 29.43230 29.90767 28.84780 25.41847 19.31450 14.79607 13.81753 15.29163 18.30843 21.62163
1991 24.78140 27.42710 29.72453 30.74743 29.95747 26.70900 19.79180 14.89960 13.59467 15.08900 17.73280 20.99953
1992 24.28430 26.86513 28.72903 29.65103 29.22520 26.78413 20.68500 15.82260 15.08637 16.64880 19.20323 22.42660
1993 25.38647 27.68323 29.51227 30.43477 29.51470 25.71423 18.27183 13.38497 12.44960 14.03683 17.03173 20.51220
1994 23.95567 26.62633 28.77047 29.74120 29.28143 26.47327 19.81260 14.78910 13.86447 15.25647 17.98890 21.31227
1995 24.28500 26.39613 27.99903 28.44240 27.25397 23.72430 16.97723 12.34163 11.23483 12.18747 14.88323 18.28950
1996 21.75190 24.42587 26.44643 27.45437 27.22710 24.80297 19.08240 14.81053 13.95943 15.45457 17.43087 20.25397
1997 23.59723 26.26750 28.37530 29.37567 28.70237 25.63657 19.02647 14.28473 13.22977 14.25300 16.66113 20.02467
1998 23.57797 26.30687 28.35510 29.41817 28.77380 25.27467 18.35193 13.17423 11.62333 12.88237 15.68867 19.05993
1999 22.53313 25.27680 27.35863 28.45760 27.88147 24.80390 18.30300 12.94847 11.04383 12.51250 15.42213 18.49580
2000 21.81247 24.25717 26.22337 27.16113 26.64983 23.80740 17.20880 12.32520 11.08693 12.37740 14.94453 18.04860
2001 21.36713 24.08317 26.47670 27.64093 26.81653 23.75473 17.70773 13.30503 12.27443 13.38393 15.80307 18.70017
2002 21.94443 24.74347 26.70337 27.43367 26.78090 23.60413 16.95007 12.02417 10.84620 11.95053 14.63540 17.94663
2003 21.34073 24.07647 26.36853 27.24690 26.20967 22.83477 16.26497 11.40443 10.28357 11.26057 13.72980 16.95223
2004 20.14570 22.61073 24.86940 25.75607 25.27420 22.63327 16.37187 11.40310 10.04017 11.30763 14.01267 17.34433
2005 20.34063 22.62670 24.88353 26.05220 25.30047 21.53217 15.02170 10.61897 9.27993 10.23520 12.89247 16.09070
2006 19.40683 21.98927 24.11090 25.11020 24.28553 20.82130 14.49717 10.31810 9.10820 9.86110 12.30253 15.13370
2007 18.43173 20.77657 23.06050 23.76373 23.05763 19.11037 11.92693 7.53630 6.52773 7.15367 10.47243 14.29950
2008 18.64417 21.48687 23.89753 24.99547 24.07940 20.49807 13.95730 9.09057 7.24567 8.34373 11.75897 15.25553
2009 18.91127 21.63637 23.85667 24.95700 23.81820 19.64937 12.61507 8.18660 6.92347 7.68770 10.81293 14.30060
2010 17.77877 20.53350 23.15687 24.10263 22.13040 17.04407 10.04963 5.84187 4.74757 6.27270 9.53500 13.04230
2011 16.31127 19.27057 21.45043 22.51047 21.07010 16.40333 9.35003 5.40543 4.48450 5.78413 9.31633 13.11260
2012 17.00413 19.54710 22.00257 23.13023 21.63083 15.89650 9.08033 4.86937 3.78893 5.07027 8.27640 12.26053
2013 15.92377 19.26217 22.03433 23.13053 21.80910 17.44690 10.33533 6.31640 5.48323 7.03607 10.13027 13.91273
2014 17.51440
Title: Re: Latest PIOMAS update (February)
Post by: ChrisReynolds on February 08, 2014, 03:03:22 PM
Thickness (metres) from PIOMAS (V2.1) Gridded data         
Area   1980s   2012   2013
Okhotsk   0.18   0.17   0.17
Bering   0.28   0.40   0.25
Beaufort   1.88   1.04   1.24
Chukchi   1.67   0.91   0.79
ESS   2.17   1.04   1.08
Laptev   1.50   1.15   0.97
Kara   1.08   0.63   0.75
Barents   0.94   0.33   0.50
Greenland   1.21   0.94   0.94
Central   2.66   1.53   1.74
CAA   1.89   1.12   1.30
Baffin   0.80   0.62   0.76
Hudson   0.61   0.56   0.67
Title: Re: Latest PIOMAS update (February)
Post by: Jim Pettit on February 08, 2014, 05:15:37 PM
I've updated all my pertinent PIOMAS sea ice volume graphs (https://sites.google.com/site/pettitclimategraphs/sea-ice-volume) to version 2.1:


(In some cases--namely the 3D graphs--the January data won't be shown in full until the February numbers are published and January can be closed out.)
Title: Re: Latest PIOMAS update (February)
Post by: crandles on February 08, 2014, 06:17:18 PM
(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Ffarm8.staticflickr.com%2F7341%2F12388348675_fb2e7bd922_o.png&hash=686986780288d86f113f7b7c74fbafea)
Title: Re: Latest PIOMAS update (February)
Post by: ChrisReynolds on February 08, 2014, 08:13:16 PM
Blog post on the new data here:
http://dosbat.blogspot.co.uk/2014/02/piomas-v21.html (http://dosbat.blogspot.co.uk/2014/02/piomas-v21.html)
Title: Re: Latest PIOMAS update (February)
Post by: jdallen on February 09, 2014, 07:50:10 AM
(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Ffarm8.staticflickr.com%2F7341%2F12388348675_fb2e7bd922_o.png&hash=686986780288d86f113f7b7c74fbafea)
YES!

This is exactly what I was working on!

The key thing to note is the increase in *Melt* that has been taking place, primarily since 2000.

My own graphs were using a running 5 year average rather than the 1979-2000 average as a baseline, but they show much the same sort of pattern.
Title: Re: Latest PIOMAS update (February)
Post by: crandles on February 09, 2014, 11:28:07 AM
Then perhaps this is also worth posting:

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Ffarm4.staticflickr.com%2F3832%2F12396645665_9c4dc90817_o.png&hash=b511728cfc34dda12d216ad80716d080)

which is recreating a couple of Chris Reynolds graphs. Have you looked at dosbat
http://dosbat.blogspot.co.uk/2014/02/piomas-v21.html (http://dosbat.blogspot.co.uk/2014/02/piomas-v21.html)
Title: Re: Latest PIOMAS update (February)
Post by: crandles on February 09, 2014, 12:51:37 PM
I let excel do the 5 year moving average. If I did them I would have placed each data points two years earlier at the middle of the range rather than the end.

The April average to May average shows a remarkable upturn with the volume melting tripling.

May to June show a similar upturn close to doubling.

June to July is a bit unclear whether it is beginning to show an upturn.

July to Sept surprises me. It looks like there is a discontinuity at about 1997/98, but that timing might be suggestive of a large spike due to the super El Nino. That with random noise might give the impression of a discontinuity.

Anyway the strength of the decline from 1979 to 1996 still seems surprising given the lack of any trend in the total season melt unless there is some explanation. Therefore I am wondering if less MYI (perhaps particularly in ESS and Laptev?) was encouraging early season melt but once season was in advance of where it usually was after the early season melt, the melt slowed down to compensate for some reason(s). I would like to better understand those reasons for the slower melt in the later part of the melt season. The only thing that has occurred to me and/or been suggested by Dr Zhang is that with less ice, there is less area and less edge where the melt occurs.

Any other thoughts on whether there might be a discontinuity or reasons for a late melt season slowing of melt?
Title: Re: Latest PIOMAS update (February)
Post by: jdallen on February 09, 2014, 01:06:32 PM
I let excel do the 5 year moving average. If I did them I would have placed each data points two years earlier at the middle of the range rather than the end.

The April average to May average shows a remarkable upturn with the volume melting tripling.

May to June show a similar upturn close to doubling.

June to July is a bit unclear whether it is beginning to show an upturn.

July to Sept surprises me. It looks like there is a discontinuity at about 1997/98, but that timing might be suggestive of a large spike due to the super El Nino. That with random noise might give the impression of a discontinuity.

Anyway the strength of the decline from 1979 to 1996 still seems surprising given the lack of any trend in the total season melt unless there is some explanation. Therefore I am wondering if less MYI (perhaps particularly in ESS and Laptev?) was encouraging early season melt but once season was in advance of where it usually was after the early season melt, the melt slowed down to compensate for some reason(s). I would like to better understand those reasons for the slower melt in the later part of the melt season. The only thing that has occurred to me and/or been suggested by Dr Zhang is that with less ice, there is less area and less edge where the melt occurs.

Any other thoughts on whether there might be a discontinuity or reasons for a late melt season slowing of melt?

I was using the 5 year moving average as well, but wasn't breaking things down as finely month to month.  What I noticed primarily with the 5 year moving average, was when computing anomalies from that, the dramatic break that takes place around/about 2000.  The net loss, April-Sept starts making a consistent upturn, and the total melt increases.  The Sept-April refreeze does show a significant, almost complete recovery, but it seems like the volatility of the refreeze/melt is oscillating around some *almost* predictable level.  I'll continue tinkering with the data.

Once again, Albedo, energy loss, etc. is no doubt playing a part during any specific year, but it still seems the net energy available in the arctic establishes some sort of focal point for the variations in volume, +/- variability tied to characteristics of the specific season.

Even with an uptick (2013) I'm not sure the refreeze will take that value high enough, that the coming melt season won't see a drop below 2013 levels, possibly lower still.  Even with radiative loss, the net inputs into the system seem quite high.  Once we start getting insolation back, the equation becomes quite a bit more dire, I think.  Those 20+ degree anomalies have to be having and effect.  They may not be melting, but I suspect the imported heat is reducing the refreeze, and pumping energy into the region which replaces that lost through radiation.  I'd love to have some sort of reliable heat data.
Title: Re: Latest PIOMAS update (February)
Post by: ktonine on February 09, 2014, 03:02:22 PM
crandles:
...but once season was in advance of where it usually was after the early season melt, the melt slowed down to compensate for some reason...

I think some of these idiosyncrasies of longterm melt patterns can be explained by geography. 
 We typically segregate the data by region or sea, but in many cases latitude might tell a better story.
Title: Re: Latest PIOMAS update (February)
Post by: Shared Humanity on February 09, 2014, 03:43:19 PM
Could these monthly melt trends be the result of an interaction between the availability and quality of the ice at any point in the melt season and insolation? It appears as if the melt slows after the sun reaches its highest point in the sky. As it lowers towards the horizon the remaining ice sees a reduction in insolation which slows the melt of the ice which, as ktonine says, is concentrated in the higher latitudes.

This interaction between reduced insolation and reduced SIA (concentrated in the high latitudes)  might  also explain the accelerated freeze that we are seeing as we head into the freeze seasons.
Title: Re: Latest PIOMAS update (February)
Post by: crandles on February 09, 2014, 03:51:41 PM
Could these monthly melt trends be the result of an interaction between the availability and quality of the ice at any point in the melt season and insolation? It appears as if the melt slows after the sun reaches its highest point in the sky. As it lowers towards the horizon the remaining ice sees a reduction in insolation which slows the melt of the ice which, as ktonine says, is concentrated in the higher latitudes.

This interaction between reduced insolation and reduced SIA (concentrated in the high latitudes)  might  also explain the accelerated freeze that we are seeing as we head into the freeze seasons.

The Jun to July melt is much larger than the May to Jun melt even though the Jun to July melt is mainly after the sun reaches its highest angle. Therefore lower albedo of thinner ice and open water is clearly important.
Title: Re: Latest PIOMAS update (February)
Post by: ChrisReynolds on February 09, 2014, 10:14:27 PM
crandles:
...but once season was in advance of where it usually was after the early season melt, the melt slowed down to compensate for some reason...

I think some of these idiosyncrasies of longterm melt patterns can be explained by geography. 
 We typically segregate the data by region or sea, but in many cases latitude might tell a better story.

There is a paper comparing extent changes for the Arctic and Antarctic which finds this effect. I could easily calculate PIOMAS volume change by latitude band.
Title: Re: Latest PIOMAS update (February)
Post by: Wipneus on February 10, 2014, 09:06:56 AM
Updated my Fram graphics with the 2013 (v2.1) data.

Fram time line, transport in spring (AMJ) is still high compared with other seasons and annual:

(https://sites.google.com/site/arctischepinguin/home/piomas/grf/fram.png)

Fram seasonal: summer 2013 transport was low. But not as low as 2003-2004, and only slightly below average. The low Jan/Feb transport in 2014 is highly un-seasonal, but that has to wait until next year to be graphed.

(https://sites.google.com/site/arctischepinguin/home/piomas/grf/fram2.png)
Title: Re: Latest PIOMAS update (February)
Post by: ChrisReynolds on February 10, 2014, 06:56:32 PM
crandles:
...but once season was in advance of where it usually was after the early season melt, the melt slowed down to compensate for some reason...

I think some of these idiosyncrasies of longterm melt patterns can be explained by geography. 
 We typically segregate the data by region or sea, but in many cases latitude might tell a better story.

There is a paper comparing extent changes for the Arctic and Antarctic which finds this effect. I could easily calculate PIOMAS volume change by latitude band.

I could easily calculate it, but I don't think it's worth it. At one month resolution the gridded PIOMAS data hasn't the daily resolution needed to make such an effort worth it.

However within the Arctic Ocean, I can confirm that Central Arctic volume tends to peak in May, while the peripheral seas (Beaufort to Laptev) peak in April. I suspect this is showing the effect you were expecting.
Title: Re: Latest PIOMAS update (March)
Post by: Wipneus on March 07, 2014, 06:45:28 PM
Updated, graphs are in the top post (https://forum.arctic-sea-ice.net/index.php/topic,119.0.html).
Title: Re: Latest PIOMAS update (March)
Post by: crandles on March 07, 2014, 09:29:57 PM
Day 59 (28 Feb) values
2014  59  20.860
2013  59  20.903
2012  59  20.707
2011  59  20.459
2010  59  21.929
2007  59  22.063

So now 3rd lowest on record .153 above 2012 and .401 above 2011

For 31 Jan:
2014  31  18.937
2013  31  17.733
2012  31  18.432
2011  31  17.938
2010  31  19.222
2007  31  19.584

So at 31 Jan ice volume was 4th lowest, 1.001 above 2011 and we are now only .401 above 2011. If we continue to catch up at anything like that rate, becoming lowest maximum volume per PIOMAS does not look impossible.
Title: Re: Latest PIOMAS update (March)
Post by: Wipneus on March 14, 2014, 08:08:47 AM
Gridded monthly thickness data has been updated with February 2014.

Attached are thickness maps for February 2013 and 2014, as well as the difference between them.

[edit: fixed the difference map to display the right month]
Title: Re: Latest PIOMAS update (March)
Post by: Wipneus on March 14, 2014, 08:13:49 AM
And the January-to-February growth difference between 2013 and 2014. Comparing this with the thickness difference map in the previous post, it is nice to see that where the ice is thicker the growth is less and where the ice is thinner in 2014 (eg Laptev) the growth is a bit higher.
Title: Re: Latest PIOMAS update (March)
Post by: Neven on March 14, 2014, 09:24:42 AM
Very nice and interesting, as always. Thanks, WN.
Title: Re: Latest PIOMAS update (March)
Post by: Steven on March 14, 2014, 05:09:58 PM
Gridded monthly thickness data has been updated with February 2014.

Attached are thickness maps for February 2013 and 2014, as well as the difference between them.

Thanks, Wipneus.

Is the third map in your post the difference in thickness between February 2014 and February 2013?  On my (low resolution) screen it doesn't seem to match with the difference of the first two maps, for example in the region east of Svalbard.  Apologies if my reading of the maps is incorrect.
Title: Re: Latest PIOMAS update (March)
Post by: Wipneus on March 14, 2014, 05:42:04 PM

Is the third map in your post the difference in thickness between February 2014 and February 2013?  On my (low resolution) screen it doesn't seem to match with the difference of the first two maps, for example in the region east of Svalbard.  Apologies if my reading of the maps is incorrect.

Steven, you were absolutely right. I showed the January difference map, this map is quite different North of Svalbard and what a difference in west Chukchi!

Thanks for spotting this.
Title: Re: Latest PIOMAS update (March)
Post by: ChrisReynolds on March 14, 2014, 09:39:07 PM
I'll be blogging with a lot more detail tomorrow, but here's some graphics until I post. My take home message - we're now virtually at identical conditions (given PIOMAS uncertainty) as we were this time last year, most of the volume gain remains in the Central Arctic region (as Wipneus shows). Given the right weather conditions this year could easily see another 2012 type drop.

Title: Re: Latest PIOMAS update (March)
Post by: Nightvid Cole on March 14, 2014, 11:51:56 PM
Thanks for the sneak peak, Chris! :)
Title: Re: Latest PIOMAS update (March)
Post by: slow wing on March 15, 2014, 12:34:11 AM
Thanks for these plots, Wipneus and Chris. Very interesting and much appreciated!   :D
Title: Re: Latest PIOMAS update (March)
Post by: ChrisReynolds on March 15, 2014, 08:25:59 AM
Wipneus,

Hope you don't mind - I intend to use your difference plot in my blog post.
Title: Re: Latest PIOMAS update (March)
Post by: Wipneus on March 15, 2014, 08:54:06 AM
Wipneus,

Hope you don't mind - I intend to use your difference plot in my blog post.

No problem there Chris.
Title: Re: Latest PIOMAS update (March)
Post by: crandles on April 07, 2014, 11:31:19 PM
March daily data is now out. 31 March 14 value 22.609 just below 2011's minimum maximum of 22.677, is second lowest for 31 March 14.

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fpsc.apl.washington.edu%2Fwordpress%2Fwp-content%2Fuploads%2Fschweiger%2Fice_volume%2FBPIOMASIceVolumeAnomalyCurrentV2.1_CY.png&hash=f61d516ac3b505fb678d0c7abd01b6fe)
Title: Re: Latest PIOMAS update (March)
Post by: Jim Pettit on April 08, 2014, 12:34:21 AM
 Excellent! I've gone ahead and updated my interactive 3D PIOMAS graphs with the March numbers, as well:
Title: Re: Latest PIOMAS update (April)
Post by: Wipneus on April 08, 2014, 06:59:10 AM
Updated, graphs are in the top post (https://forum.arctic-sea-ice.net/index.php/topic,119.0.html).
Title: Re: Latest PIOMAS update (April)
Post by: Wipneus on April 08, 2014, 07:47:06 AM
Gridded monthly thickness data has been updated as well with March 2014.

Attached are thickness maps for March 2013 and 2014, as well as the difference between them.
Title: Re: Latest PIOMAS update (April)
Post by: Wipneus on April 08, 2014, 07:49:02 AM
And the difference between the March-February growth (or melt) between 2014 and 2013.
Title: Re: Latest PIOMAS update (April)
Post by: jdallen on April 08, 2014, 08:44:19 PM
It looks like an awful lot of our recovered volume is stacked up along the CAA.  Even with the increase in MYI, we have no broad recovery in thickness.  In fact, it looks just as vulnerable as last year.  This tends to be borne out anecdotally by the spot measurements we see at the buoys and Barneo.  I'm very anxious to see what Icebridge will tell us.  I'm not expecting any good news.
Title: Re: Latest PIOMAS update (April)
Post by: ChrisReynolds on April 08, 2014, 10:30:29 PM
Thickness breakdowns for Beaufort/ESS/Central, and regional volume breakdowns etc here:
http://dosbat.blogspot.co.uk/2014/04/piomas-march-2014.html (http://dosbat.blogspot.co.uk/2014/04/piomas-march-2014.html)

Looks like we may have an exciting melt season.  ;D
Title: Re: Latest PIOMAS update (May)
Post by: Wipneus on May 08, 2014, 05:53:59 AM
Updated, graphs are in the top post (https://forum.arctic-sea-ice.net/index.php/topic,119.0.html).

(no gridded data update yet)
Title: Re: Latest PIOMAS update (May)
Post by: Wipneus on May 08, 2014, 06:54:12 AM
From the Polar Science Ice Volume Page (http://psc.apl.washington.edu/wordpress/research/projects/arctic-sea-ice-volume-anomaly/)


The 2014 ice volume reached its annual maximum in April  with 22,900 km3  which is just slightly below the long term trend and is the second lowest on record;  just 400 km3 above the previous April minimum which occurred in 2011.  However, variations over the last 4-years are well within the error bars of the volume estimates so that inter-annual variability over this period maybe due to errors in the sea ice reanalysis.
Title: Re: Latest PIOMAS update (May)
Post by: crandles on May 08, 2014, 05:07:38 PM
Daily Max 23.104 day 105 second lowest 0.427 above day 109 2011 at 22.677.

April Average 22.931 second lowest 0.42 above April 2011.

31 March 14 at 22.609 was second lowest 0.48 above 2011.

30 April 14 at 22.94 is third lowest 0.112 above 2013's 22.828 and 0.658 above 2011's 22.282.

So April 2014 has been unusually flat, starting 0.48 above 2011 the difference reduced to 0.427 at maximum then the difference increased to 0.658 at the end of April.

Temperature was above average almost throughout month
(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Focean.dmi.dk%2Farctic%2Fplots%2FmeanTarchive%2FmeanT_2014.png&hash=7f94b91dafe8aa9f0d8d5cd2bf581c21)

Any reasons for unusually flat shape?
(maybe I need temperature N of 70N rather than N ot 80N?)
Title: Re: Latest PIOMAS update (May)
Post by: ChrisReynolds on May 08, 2014, 06:29:23 PM
Crandles,

Whilst there is the usual low level surface hugging warming typical of recent years, this winter has seen substantial warming from the 1951 to 1980 baseline average (GISS baseline) up to around 500mb (north of 80degN for NCEP/NCAR).

The low level warming is due to loss of ice. But the deeper atmospheric warming of this year seems to me to be probably due to influx of warmer air - although I've not been able to conclusively demonstrate that.
Title: Re: Latest PIOMAS update (May)
Post by: jdallen on May 08, 2014, 07:36:32 PM
The low level warming is due to loss of ice. But the deeper atmospheric warming of this year seems to me to be probably due to influx of warmer air - although I've not been able to conclusively demonstrate that.
Chris - I presume the heating of mid levels of the atmosphere is an unpleasant but expected climate signal?

I would imagine it would have a modest but non-trivial effect on outgoing heat transfer?
Title: Re: Latest PIOMAS update (May)
Post by: crandles on May 08, 2014, 08:10:17 PM
Crandles,

Whilst there is the usual low level surface hugging warming typical of recent years, this winter has seen substantial warming from the 1951 to 1980 baseline average (GISS baseline) up to around 500mb (north of 80degN for NCEP/NCAR).

The low level warming is due to loss of ice. But the deeper atmospheric warming of this year seems to me to be probably due to influx of warmer air - although I've not been able to conclusively demonstrate that.

So are you saying that ice causes low level temperature not the other way around so I shouldn't look at temperature for an explanation?

or are you suggesting that the deeper atmospheric warmth this year should have affected ice levels so this year should have seen less up and more down? This doesn't agree with the flat PIOMAS trend in April either.

Perhaps that deeper atmospheric warmth applies over a longer timescale than just April and is an explanation for the small gain in the run up to the maximum. We haven't seen much time since the maximum and while the small loss since maximum isn't explained by this, over a short period there can be lots of possible explanations?
Title: Re: Latest PIOMAS update (May)
Post by: lanevn on May 08, 2014, 08:15:32 PM
@crandles

April 2014 were colder than april 2013 for that graph, so it is normal that it lost his second place.
Title: Re: Latest PIOMAS update (May)
Post by: crandles on May 08, 2014, 08:32:04 PM
@crandles

April 2014 were colder than April 2013 for that graph, so it is normal that it lost his second place.

Good point thanks.

The end of April 2011 was also warmer than in 2014 potentially accounting for an increase in the gap.

The end of April 2012 was cooler but the gap has if anything narrowed rather than widened so I guess we cannot fully explain deviations like this but it could be a good part of the explanations necessary.
Title: Re: Latest PIOMAS update (May)
Post by: ChrisReynolds on May 08, 2014, 09:46:25 PM
I've just blogged, so can post images now.

JDAllen,

Not a climate signal, just weather. Even in recent years above about 900mb there are cold and warm winters. The low level warming in the following graphic is due to 1) the breakdown of the calimatological (i.e. typical) inversion, 2) surface sourced heat flux due to thinner ice (which in part causes 1).

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2F4.bp.blogspot.com%2F-7T1hQWOu3lg%2FU2vGC8u7txI%2FAAAAAAAAAVI%2FbTSnSkU5Igw%2Fs1600%2F2014%2Btemperature%2Bprofile.png&hash=e0a41e55cb91a7be88fe882fcc218244)

Crandles,

There's a two way effect. However summer (including spring) melt losses are, as you know, countered by winter (including autumn volume gains).

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2F2.bp.blogspot.com%2F-hF5Fq5WgdLc%2FU2vGEcXGlpI%2FAAAAAAAAAVA%2FwtimJKGeVww%2Fs1600%2FPIOMAS%2BWinter%2BSummer%2Bgrowth%2Bloss.png&hash=56374baedcb9eddefaefef6e667d5935)

While at the same time winter warming is racing ahead of summer warming.

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2F4.bp.blogspot.com%2F-zYTfhOV_v3w%2FU2vGDkDEGoI%2FAAAAAAAAAU8%2FBjobinEGMNc%2Fs1600%2FMelt%2BFreeze%2BTemp%2BAnoms.png&hash=11fcad5690d103d1ab04f57dea36afb6)

So it is clear that while we should expect some kind of impact on winter volume gains due to the winter warming, we aren't. So I think the only answer to this is that winter warming at the surface is caused mainly by open water and thinner ice, it is not causing that. Amidst this warming the overall change in volume gain over winter as been an increase.

However with regards this year (damn - forgot to add this to my blog post) - Francis & Hunter find that downwelling longwave (DLR) impacts the ice edge in summer, other research shows DLR is a strong factor in ice loss in models. Warming aloft should be expected to increase DLR, so I suspect the upper atmosphere (900 to 500mb) warming may have played a role in limiting thickening this year.

For comparison I've uploaded JFM 2013 and 2012...

Title: Re: Latest PIOMAS update (May)
Post by: crandles on May 08, 2014, 10:18:20 PM

So it is clear that while we should expect some kind of impact on winter volume gains due to the winter warming, we aren't. So I think the only answer to this is that winter warming at the surface is caused mainly by open water and thinner ice, it is not causing that. Amidst this warming the overall change in volume gain over winter as been an increase.


I think the prime effect on volume gain is that if you start from a lower minimum then you get a larger gain. So rather than work in terms of what affects volume gain, it is much better to work with volume maximum.

This years volume maximum appears lower than 2012 and 2013, but perhaps we should expect more difference. How does 2014 NCEP/NCAR reanalysis temperature given above compare with 2011 if that isn't too much trouble?

Title: Re: Latest PIOMAS update (May)
Post by: Steven on May 08, 2014, 11:50:48 PM
The end of April 2011 was also warmer than in 2014 potentially accounting for an increase in the gap.

The end of April 2012 was cooler but the gap has if anything narrowed rather than widened so I guess we cannot fully explain deviations like this but it could be a good part of the explanations necessary.

CT sea ice area decreased rapidly around the middle of April 2014,  but slowed down and plateaued during the last part of April.  So the "flat" shape of the PIOMAS curve for April 2014 may be partly due to weather conditions near the edges of the ice.

In contrast, the other years in the 2010s had a big decrease of CT area in the last 10 days of April.
Title: Re: Latest PIOMAS update (May)
Post by: jdallen on May 09, 2014, 12:18:42 AM
Magnificently illustrated as typical, Chris. Thank you!
Title: Re: Latest PIOMAS update (May)
Post by: ChrisReynolds on May 10, 2014, 09:51:59 AM

So it is clear that while we should expect some kind of impact on winter volume gains due to the winter warming, we aren't. So I think the only answer to this is that winter warming at the surface is caused mainly by open water and thinner ice, it is not causing that. Amidst this warming the overall change in volume gain over winter as been an increase.


I think the prime effect on volume gain is that if you start from a lower minimum then you get a larger gain. So rather than work in terms of what affects volume gain, it is much better to work with volume maximum.

This years volume maximum appears lower than 2012 and 2013, but perhaps we should expect more difference. How does 2014 NCEP/NCAR reanalysis temperature given above compare with 2011 if that isn't too much trouble?

The overall multi-year trend shows the impact of reducing summer volume on the following freeze season gain. This years freeze season gain hasn't been as large as recent years, so looking for the effects of warming on that seems to be swamped by the signal of the growth response to reduced summer volume.

However similarly the overall surface warming has climbed so much over winter that it doesn't seem to me to be a major factor in determining end of winter peak volume.

What temperatures do you need? A quick snapshot of the lower atmospheric column would seem to me to be surface, 850mb, 500mb - would this be OK?

Steven,

That seems reasonable, notably up to end May there is still some thickening in parts of the central Arctic Ocean in most years.

JD Allen,

I just hope it was useful, thanks.
Title: Re: Latest PIOMAS update (May)
Post by: ghoti on May 10, 2014, 07:28:19 PM
On a press conference webcast from the European Geophysical Union meetings  near the end of April data was presented showing a good correlation between freezing degree days (FDD) and maximum ice volume. Seems obvious to me. The FDD charts for the post satellite era look the same as the PIOMASS max volume charts for the same period. I wish I remembered the presenter's name so I could find a reference.

In any case, winter temperatures were above average the entire freezing season this year so it is no surprise that volume increase was lower.
Title: Re: Latest PIOMAS update (May)
Post by: OSweetMrMath on May 11, 2014, 08:32:48 AM
I've been doing some experimenting with modeling PIOMAS as a SARIMA time series, and I have some results to share. This graph shows the last few years of PIOMAS data in black, with predictions through 2016 in red. The dashed lines are (nominal) 95% confidence intervals on the predictions. The year tick marks indicate January of each year.

The prediction of greatest interest is probably the volume in September. The predicted value for this year is 4.6 x 10^3 km^3, and the 95% confidence interval is 2.9 - 6.3 x 10^3 km^3. Note that the confidence interval size is nominally 95%, but based on previous years, this interval is too small. In practice, this is an 85% confidence interval, and a 95% confidence interval would be approximately 50% larger, or 2.1 - 7.2 x 10^3 km^3.

Also, note that when the smaller interval fails to accurately predict the September ice volume, the prediction is usually too high.
Title: Re: Latest PIOMAS update (May)
Post by: Steven on May 11, 2014, 05:30:25 PM
I wish I remembered the presenter's name so I could find a reference.

Perhaps it's in the Press Conference webstream "PC3: The changing Arctic":

http://client.cntv.at/EGU2014/?play=24 (http://client.cntv.at/EGU2014/?play=24)

Second speaker Jean-Claude Gascard between minutes 12 and 14 of the video shows some maps of "Freezing Degree Days" for 4 different freezing seasons, and next shows a graph of "ice volume produced in winter calculated from FDD".  His presentation slides and abstract are here (http://media.egu.eu/documents)  (search for "Gascard")
Title: Re: Latest PIOMAS update (May)
Post by: Steven on May 11, 2014, 06:13:45 PM
So I think the only answer to this is that winter warming at the surface is caused mainly by open water and thinner ice, it is not causing that.

Chris, thanks for your comments above and for your blog post (http://dosbat.blogspot.be/2014/05/april-2014-start-of-new-season.html).  My understanding is that there are other amplifying factors which are also very important, e.g. in the Pithan/Mauritsen paper that was discussed some time ago in another thread (https://forum.arctic-sea-ice.net/index.php/topic,722.msg19805.html#msg19805).  (It's probably more on-topic there than here.)  Here's a link to the pdf of the paper (http://www.researchgate.net/profile/Thorsten_Mauritsen/publication/259990439_Arctic_amplification_dominated_by_temperature_feedbacks_in_contemporary_climate_models/file/9c96052ef41dc12d91.pdf).  There's also an article about it on LiveScience.com (http://www.livescience.com/43045-arctic-warming-linked-stratified-air.html).  It looks very interesting to me.
 
Title: Re: Latest PIOMAS update (May)
Post by: ChrisReynolds on May 11, 2014, 07:46:52 PM
Steven,

Pithan/Mauritsen look at ice/snow albedo feedback, this is not a factor north of 80degN over autumn/winter, however they may be considering the winter warming as resultant from ice/albedo feedback through release of ocean heat - I may have missed it but I don't think that's clear. I don't doubt that Plank emission needs a higher temperature increase at lower temperatures to achieve the same increase of emission as at higher temperatures. I just doubt it is the major player in winter warming.

The greatest anomalous warming in the annual cycle is over the dark months in both NCEP/NCAR and ERA Interim. The climatological mean temperature profile with height from 2007 to 2012 is shown below (NCEP/NCAR) relative to a 1951 to 1980 baseline.

(https://farm3.staticflickr.com/2911/14158918582_6b92a58f21_o.png)

This shows a very low level massive warming, which I have argued is due to thinning of sea ice.
http://dosbat.blogspot.co.uk/2013/10/winter-warming-and-sea-ice-thinning.html (http://dosbat.blogspot.co.uk/2013/10/winter-warming-and-sea-ice-thinning.html)

Using a grid box covering part of the Siberian Arctic it is seen that winter surface temperature and PIOMAS thickness track each other closely.
(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Ffarm3.staticflickr.com%2F2849%2F10506908784_48b9a0761f_o.png&hash=c745cc270c265b745021071883661677)

Because NCEP/NCAR is used in PIOMAS it may be thought that this close relationship is due to winter thickening reducing with the warming. However a substantial proportion of the thinning is due to loss of MYI, not thermodynamic thinning. For example here are the DAM plots for Jan 1984 and Jan 2013
ftp://ccar.colorado.edu/pub/tschudi/iceage/gifs/age1984_01.gif (http://ftp://ccar.colorado.edu/pub/tschudi/iceage/gifs/age1984_01.gif)
ftp://ccar.colorado.edu/pub/tschudi/iceage/gifs/age2013_01.gif (http://ftp://ccar.colorado.edu/pub/tschudi/iceage/gifs/age2013_01.gif)
And for the same region used in the above linked blog post, here is the percentage contribtion to overall volume for grid boxes above and below 2m thick in December (a reasonable proxy for MYI and FYI)
(https://farm6.staticflickr.com/5513/14182020153_b81533d3dc_o.png)

I calculate that the combined thinning of ice and warming of atmosphere, has increased heat flux through the ice by something of the order of 50%.
(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Ffarm4.staticflickr.com%2F3833%2F10507089883_814ba62fbb_o.png&hash=a7be7681b1115fe65e79c3c309ffd5a0)

So in line with Screen and Simmonds I think the major player in reality is the thinning of ice over winter due to the transition from a mainly MYI to a mainly FYI cover.
Title: Re: Latest PIOMAS update (May)
Post by: Nightvid Cole on May 11, 2014, 08:48:12 PM
Steven,

Pithan/Mauritsen look at ice/snow albedo feedback, this is not a factor north of 80degN over autumn/winter, however they may be considering the winter warming as resultant from ice/albedo feedback through release of ocean heat - I may have missed it but I don't think that's clear. I don't doubt that Plank emission needs a higher temperature increase at lower temperatures to achieve the same increase of emission as at higher temperatures. I just doubt it is the major player in winter warming.

The greatest anomalous warming in the annual cycle is over the dark months in both NCEP/NCAR and ERA Interim. The climatological mean temperature profile with height from 2007 to 2012 is shown below (NCEP/NCAR) relative to a 1951 to 1980 baseline.

(https://farm3.staticflickr.com/2911/14158918582_6b92a58f21_o.png)

This shows a very low level massive warming, which I have argued is due to thinning of sea ice.
http://dosbat.blogspot.co.uk/2013/10/winter-warming-and-sea-ice-thinning.html (http://dosbat.blogspot.co.uk/2013/10/winter-warming-and-sea-ice-thinning.html)

Using a grid box covering part of the Siberian Arctic it is seen that winter surface temperature and PIOMAS thickness track each other closely.
(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Ffarm3.staticflickr.com%2F2849%2F10506908784_48b9a0761f_o.png&hash=c745cc270c265b745021071883661677)

Because NCEP/NCAR is used in PIOMAS it may be thought that this close relationship is due to winter thickening reducing with the warming. However a substantial proportion of the thinning is due to loss of MYI, not thermodynamic thinning. For example here are the DAM plots for Jan 1984 and Jan 2013
ftp://ccar.colorado.edu/pub/tschudi/iceage/gifs/age1984_01.gif (http://ftp://ccar.colorado.edu/pub/tschudi/iceage/gifs/age1984_01.gif)
ftp://ccar.colorado.edu/pub/tschudi/iceage/gifs/age2013_01.gif (http://ftp://ccar.colorado.edu/pub/tschudi/iceage/gifs/age2013_01.gif)
And for the same region used in the above linked blog post, here is the percentage contribtion to overall volume for grid boxes above and below 2m thick in December (a reasonable proxy for MYI and FYI)
(https://farm6.staticflickr.com/5513/14182020153_b81533d3dc_o.png)

I calculate that the combined thinning of ice and warming of atmosphere, has increased heat flux through the ice by something of the order of 50%.
(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Ffarm4.staticflickr.com%2F3833%2F10507089883_814ba62fbb_o.png&hash=a7be7681b1115fe65e79c3c309ffd5a0)

So in line with Screen and Simmonds I think the major player in reality is the thinning of ice over winter due to the transition from a mainly MYI to a mainly FYI cover.

If this explanation were correct, wouldn't we expect to see greater temperature anomalies in November than we do in March or April, since the ice is thinner?
Title: Re: Latest PIOMAS update (May)
Post by: Steven on May 11, 2014, 10:04:44 PM
Chris, yes I think Pithan/Mauritsen take into account the "delayed" effect of the albedo feedback.  They say in the paper: 

Seasonal heat storage in the ocean, including latent heat of melting sea ice, mitigates about two-thirds of the summertime effect of surface albedo change.  Heat from the ocean is released to the atmosphere in winter, which in combination with the positive lapse-rate feedback causes the well-known pattern of winter-amplified Arctic warming.

The bolded sentence in this quote (bold mine) seems consistent with the feedbacks called "ocean" and "albedo" in Fig. 2b (http://www.researchgate.net/profile/Thorsten_Mauritsen/publication/259990439_Arctic_amplification_dominated_by_temperature_feedbacks_in_contemporary_climate_models/file/9c96052ef41dc12d91.pdf).  That figure shows the contribution of each feedback from a top of atmosphere perspective; Fig 2c is from a surface perspective, which is probably somewhat more relevant for the Arctic sea ice.

I need to think a bit more about your last comment and the references you gave.
Title: Re: Latest PIOMAS update (May)
Post by: Neven on May 11, 2014, 10:15:19 PM
I have to approve comments by new members before they show up, and so someone might miss this one:

I've been doing some experimenting with modeling PIOMAS as a SARIMA time series, and I have some results to share. This graph shows the last few years of PIOMAS data in black, with predictions through 2016 in red. The dashed lines are (nominal) 95% confidence intervals on the predictions. The year tick marks indicate January of each year.

The prediction of greatest interest is probably the volume in September. The predicted value for this year is 4.6 x 10^3 km^3, and the 95% confidence interval is 2.9 - 6.3 x 10^3 km^3. Note that the confidence interval size is nominally 95%, but based on previous years, this interval is too small. In practice, this is an 85% confidence interval, and a 95% confidence interval would be approximately 50% larger, or 2.1 - 7.2 x 10^3 km^3.

Also, note that when the smaller interval fails to accurately predict the September ice volume, the prediction is usually too high.

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fforum.arctic-sea-ice.net%2Findex.php%3Faction%3Ddlattach%3Btopic%3D119.0%3Battach%3D6777%3Bimage&hash=3723885e3a43c612d1fcbc5883ebce72)
Title: Re: Latest PIOMAS update (May)
Post by: wili on May 12, 2014, 05:47:56 PM
Nice graph, OSMM.

If I read it right, the lower end of predictions for September 2016 would looks like about one thousand cubic meters. If my always meager maths haven't completely failed me, that would translate to one million square meters of meter-thick ice, or what most have accepted to be the 
"essentially ice free" measure.
Title: Re: Latest PIOMAS update (May)
Post by: jai mitchell on May 12, 2014, 06:47:44 PM
Steven, Chris,

For what it is worth, my reading of Pithan-Mauritsen is that the increased moist adiabatic lapse rate feedback is equal to the summer ice albedo feedback.  The models for arctic amplification hold that winter warming will be greater than summer warming and we see that now.  I was always under the assumption that increased relative humidity in winter was the cause.

paleoclimate analysis of the Eocene holds that this area did not go below freezing in winter due to high humidity during this period.   

from a strict observational analysis of this last winter, a shift in the jet stream produced a wobble in the polar vortex https://www.youtube.com/watch?v=Pvtgoe0pN8U (https://www.youtube.com/watch?v=Pvtgoe0pN8U)  This is why Alaska had one of its warmest winters on record, extreme warm air moving north from the pacific due to the blocking system (the same that produced the droughts in California all last year) forced colder air out of the arctic.

This animation shows the actual Jetstream on January 6th, notice how the warm air is being pushed up into the arctic circle on the bearing strait and Svalbard sides of the arctic.

http://earth.nullschool.net/#2014/01/06/1500Z/wind/isobaric/850hPa/overlay=temp/orthographic=270.11,63.45,434 (http://earth.nullschool.net/#2014/01/06/1500Z/wind/isobaric/850hPa/overlay=temp/orthographic=270.11,63.45,434)

I don't believe that this can be attributed to low ice thickness or area.  I would attribute it to the pacific blocking pattern and a low pressure development over Hudson bay.
Title: Re: Latest PIOMAS update (May)
Post by: ChrisReynolds on May 12, 2014, 08:08:29 PM
Nightvid,

Here are the monthly anomalies (1951 to 1980 baseline) average from 2007 onwards.

Jan   3.042
Feb   3.954
Mar   3.377
Apr   3.520
May   2.655
Jun   0.188
Jul   0.000
Aug   0.270
Sep   3.948
Oct   6.120 -highest
Nov   4.316 -second highest
Dec   3.982

We do indeed see the greatest warming anomalies in the early autumn.
Title: Re: Latest PIOMAS update (May)
Post by: ChrisReynolds on May 12, 2014, 08:15:21 PM
Steven,

From my reading it just wasn't clear exactly how the autumn/winter energy release was handled or considered. I had read what you referenced but couldn't figure out how it was factored in. That said a chunk of the methods was out of my grasp.

Jai,

As I say in my most recent blog post, and up thread, I see this winter's warmth as being due to atmospheric heat transport into the Arctic from lower latitudes. The surface hugging warming due to thin ice is apparent, but there is also a deeper warming from over 500mb downwards which is not seen in other years.
Title: Re: Latest PIOMAS update (May)
Post by: Andreas T on May 12, 2014, 09:35:13 PM
Thinner ice which has water nearer the ice surface, does of course raise surface temperatures but must also, if everything else is unchanged, increase heat loss from that surface and therefore cooling and freezing of that water. That is, I believe, the effect seen in models (I recall a discussion on real climate some time ago) where an artificially icefree arctic returns to an ice covered one in not many years.
What Pithan and Mauritsen report is that changes in outgoing radiation from the surface have a strong effect on surface temperatures in the arctic. That would mean that the warmer (i.e. less cold) winter temperatures you point to near the surface can be the cause of less thickening of the ice rather than the consequence of thin ice.
This is of course complicated by the fact that the most substantial reduction in thickness is occurring over several seasons. So autumn ice thickness is low because of both increased summer melt and reduced winter freeze. I understand them as saying reduced winter freeze does not have to mean reduced growth compared to previous winters (you have the numbers) but reduced growth compared to what it should be at this ice thickness. They don't say that literally, but it is implied in what they are saying about warming being constituted by changes in heat fluxes and also by changes in where temperature gradients are found. I am thinking for example of their point about low clouds which increase temperatures on the surface but loose heat from their tops at the same rate as the surface did previously.
When attributing warming it makes a big difference whether one talks about higher than previous temperatures or changes in heat fluxes.
Title: Re: Latest PIOMAS update (May)
Post by: OSweetMrMath on May 13, 2014, 01:47:52 AM
Neven,

Thanks for reposting my post. One thing I didn't state, but is probably clear from the graph, is that this is based on the monthly data. The results probably would not differ greatly if I used the daily data instead.

wili,

A couple of points in response. The reliability of predictions is dependent on the goodness of fit of the model, and unfortunately, this model isn't that good.

The model assumptions of a SARIMA model are that the next month's value can be written as a weighted sum of all previous months, plus a noise term. The monthly noise is assumed to be constant variance and uncorrelated with the noise from all previous months.

The best model I can find (I used a (3,0,0)x(1,1,1) model) has noise with an increasing variance and no short term correlations, but longer term correlations are nonzero. Bigger models don't do much better, and this model is already bigger than I would like anyway.

What this means in practice is that the predictions out to a year or so probably aren't terrible, but the reliability goes down beyond that, so I'm not sure it makes much sense to look at the predictions for 2016.

If you do look at the prediction for September 2016, the minimum value for the confidence interval is 1.3 x 10^3 km^3. Keeping in mind that the confidence intervals are probably too small, this means that there is some non-zero probability that the ice minimum in 2016 will be less than 1000 km^3.

(But this interpretation is a Bayesian interpretation of a frequentist model, which is kind of sketchy from a statistical standpoint. Coming from a frequentist model, the correct interpretation of the confidence interval is a probability statement about the model. The interpretation above is making a probability statement about the ice volume.)

On the other hand, the model also states that there is an equal probability that the ice minimum in 2016 will be above 8500 km^3. Based on the record up to this point, I do not think these two probabilities are in fact equal.
Title: Re: Latest PIOMAS update (May)
Post by: Neven on May 13, 2014, 02:33:20 AM
Thanks for reposting my post.

You're welcome. I have to approve the first 3 posts by new members (as an anti-spam measure) and after that their comments show up immediately.
Title: Re: Latest PIOMAS update (May)
Post by: Wipneus on May 13, 2014, 09:38:02 AM
Back online after the main telephone in my street was cut by construction work. It may well happen again as the works will probably continue into 2015.

Anyway, here are the delayed maps created from PIOMAS gridded data. First the April thickness maps  of 2013 and 2014 as well as the differences.
Title: Re: Latest PIOMAS update (May)
Post by: Wipneus on May 13, 2014, 09:42:22 AM
And here the differences in growth between 2013 and 2014.

(I will have to change the term "growth" to something else next month. Negative growth gets too confusing, would "gains/losses" be better?)

 
Title: Re: Latest PIOMAS update (May)
Post by: crandles on May 13, 2014, 02:53:53 PM
I am thinking the comparison to 2013 may become increasingly irrelevant.

Perhaps 2011 and 2012 thickness maps (and perhaps difference to 2014) would be more relevant &/or useful additions?

Gains/losses difference is OK but perhaps add that red represent less loss of ice this year in the melt season and say red represent more gain of ice this year in freeze season.

Great work as always.
Title: Re: Latest PIOMAS update (May)
Post by: Shared Humanity on May 13, 2014, 04:10:13 PM
Nightvid,

Here are the monthly anomalies (1951 to 1980 baseline) average from 2007 onwards.

Jan   3.042
Feb   3.954
Mar   3.377
Apr   3.520
May   2.655
Jun   0.188
Jul   0.000
Aug   0.270
Sep   3.948
Oct   6.120 -highest
Nov   4.316 -second highest
Dec   3.982

We do indeed see the greatest warming anomalies in the early autumn.

If you consider that the 4 seasons are more a function of the summer and winter solstice and the spring and fall equinox, I would call this late autumn/early winter.

This raises a question for me. I wonder what all of the arctic measurement seasonal trends would look like if we considered these to be the center points of their respective seasons instead of the start points. Would we gain any insights?
Title: Re: Latest PIOMAS update (May)
Post by: ChrisReynolds on May 13, 2014, 10:57:05 PM
New post up with analysis of starting conditions for the 2014 season.
http://dosbat.blogspot.co.uk/2014/05/piomas-april-2014-gridded-data.html (http://dosbat.blogspot.co.uk/2014/05/piomas-april-2014-gridded-data.html)

Looking good for something exciting.  ;D

It's well past my bedtime, I'll reply to comments above tomorrow.
Title: Re: Latest PIOMAS update (May)
Post by: OSweetMrMath on May 15, 2014, 11:37:44 PM
I've done some more statistical regression and prediction on the PIOMAS monthly data. This time I took the average of the monthly values for each month over the period 1981-2010 as a baseline, and subtracted that from the PIOMAS data to get a monthly anomaly. I fit the anomaly with a smoothing spline, and then used that to predict future ice volumes.

Note that splines tend to have high variance at the ends of the data interval, so the ends of the spline should not be overinterpreted. Prediction of future values is inherently overinterpreting the end of the spline, so the confidence intervals (not computed) should be assumed to be quite large.

The predicted value for September is similar to the predicted value from my previous post using the SARIMA time series model, at 4600 km^3. The spline approach appears to underestimate the size of the annual cycle, but predicts a continuing decreasing trend in ice volume, unlike the SARIMA model.
Title: Re: Latest PIOMAS update (May)
Post by: ChrisReynolds on May 16, 2014, 08:51:19 PM
OSweetMrMath,

Thanks interesting. Monthly anomalies are deviations per month from an average seasonal cycle for some past baseline period (for what it's worth I use 1980 to 1999). Given that behaviour within the annual cycle can vary, for example there are different behaviours of anomalies in April, June and October, does it make physical sense to concatenate the monthly anomalies into an anomaly from the past average seasonal cycle?

Would it not make more sense from a physical perspective to analyse each seperately or indeed to work with seasonal amomalies?

I know PIOMAS use an anomaly timeseries using all days of data available in their main anomaly graph. I've just never been persuaded it's meaningful to analyse a series of anomalies in that way. When looking at the daily anomalies I use I tend to work across common points in the seasonal cycle (be it individual days, months or seasons (formal or ad hoc)) when analysing changes with time.
Title: Re: Latest PIOMAS update (May)
Post by: OSweetMrMath on May 17, 2014, 01:20:39 AM
Chris,

I've done a little formal study of time series, but I'm by no means an expert, so don't take my comments as the voice of authority. It's fairly standard in time series analysis to consider the time series as a sum of three components, the trend, the seasonal (or periodic) component, and the random noise. The goal is to estimate the trend and the seasonal component from the data, and if done well, whatever is left over should look like random noise.

If you compute an estimate of the seasonal component and subtract it from the full data, you have left the trend + the estimated noise. Because the seasonal component is an estimate, the remaining noise is also an estimate, so there's at least the potential that the estimated noise is larger than the true noise. But if the assumption that the seasonal component is periodic is a good assumption, then the estimated noise is approximately the same magnitude as the true noise.

If the periodic assumption is good, you can then use the entire time series to estimate the trend. This is in contrast to building a separate time series for each month and estimating the trend of each individually. For the individual estimates, you have less data, so the estimate is less accurate, and there's at least the potential for the estimates to be inconsistent.

So how do we know whether the periodic assumption is good? Well, we can try running the data analysis using just one month's data, and see if the results are better or worse than using the full data. Below I have a graph of the September PIOMAS data, along with an ARIMA forecast (in red, with confidence intervals as dashed lines) and a spline regression (in blue). The ARIMA forecast for September 2014 is 5000 km^3, with a 95% confidence interval of 2200-7700 km^3. The spline regression forecast for September 2014 is 3600 km^3. I haven't attempted to compute a confidence interval for the spline regression, but it is likely to be very large.

The ARIMA forecast is greater than the SARIMA forecast (from my earlier post), and also has a larger confidence interval. Essentially, the ARIMA forecast is greater than the SARIMA forecast because it doesn't know that the April volume is low, and the confidence interval is wider because it's just less accurate. I don't put a lot of value in the spline regression forecasts, but I think it's worth observing that that the spline forecast on the full data set is very close to the SARIMA forecast, but the spline forecast on just the September data is much lower than the ARIMA forecast.

Title: Re: Latest PIOMAS update (May)
Post by: OSweetMrMath on May 18, 2014, 06:50:26 AM
I was thinking that the SARIMA and ARIMA forecasts I posted earlier looked a little off. I found some online discussion which confirmed my suspicion, which is that the R function arima() does not handle trends well. So I've redone both graphs with corrected forecasts. For the corrected forecasts, the SARIMA forecast for September, using all of the PIOMAS data is 4700 km^3, with 95% CI 3000-6300 km^3. The ARIMA forecast for September, using just the September PIOMAS data, is 4300 km^3, with 95% CI 1800-6700 km^3. This is assuming that I haven't introduced any new computation errors as I've corrected my previous errors.

On further thought, the confidence intervals on the SARIMA forecast are not correct starting at April 2015 and going into the future. They should be larger.  :P

Edit: I've corrected the confidence intervals and updated the graph. Hopefully now I'm doing everything correctly.
Title: Re: Latest PIOMAS update (May)
Post by: ChrisReynolds on May 18, 2014, 09:45:57 AM
OMrSweetMath,

Thanks. I'm also no expert on timeseries analysis (I hadn't even heard of SARIMA). But I wonder if the increase in statistical confidence gained by using all months for all years as anomalies is sound. You find that the spline forecast on just September data is lower than that using all months, this is to be expected because September volume is declining faster than April (with a range of declines between those months spanning those extremes). So in this case I wonder if the higher confidence gained from using a longer series is illusory and if the result of prediction using all months will consistently overshoot the actual September volume.

I've suggested recently that we might see a reduction of loss rates in April volume because much of the past decline in volume has been from loss of thicker multi-year ice (ice which has survived more than one season). However the pack is reaching a state where it is mainly first year ice (new ice which has grown since the previous September).

Continuing melt season losses and April peak volume for the Arctic Ocean into the future, and the two curves meet in around 2020. When the curves meet it implies that April volume is equal to melt season losses resulting in virtually* no ice by September. *allow 'wiggle room' for weather impacts!

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2F2.bp.blogspot.com%2F-9Sagw-kQLoI%2FU07O_yFyXgI%2FAAAAAAAAATI%2FLEEObN9NnOQ%2Fs1600%2FCentral%2Bactual.png&hash=27f2bb3918490b054d6aad15b46f40cf)

However if the Central Arctic ceases to lose volume in April because it hits a 'floor' of around 2m thick, and the above plot becomes....

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2F2.bp.blogspot.com%2F-VSnmt_J2JKo%2FU07O_qUDMPI%2FAAAAAAAAATA%2FmMprA3niytg%2Fs1600%2FCentral%2BProjected.png&hash=a57d875761ac3cd4b3359bc125ff11f8)

The reason I raise this issue is that such a feasible underlying physical process might exacerbate the potential problem I see with using all months in forming the trend.

I've previously compared NSIDC Extent and PIOMAS volume - the extent & volume at the days of volume maximum in April and extent minimum in September. These should be related due to open water formation efficiency - the thinner ice gets the more open water can be exposed by a given melt.

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2F3.bp.blogspot.com%2F-WikZ1iqxDt8%2FU2vVxLdlEII%2FAAAAAAAAAVo%2FPgoQq8Vos6M%2Fs1600%2FTrend.png&hash=f48a315624661dd8a3cc96d299bf29d5)

Regressing the two produces quite a strong R2. However using interannual differences to effectively detrend* produces no residual relationship. *(actually the following answers the question - what is the relationship between interannual changes of volume in April and interannual changes of extent in September)

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2F3.bp.blogspot.com%2F-vFO_yiy9IZY%2FU2vVxMz1rPI%2FAAAAAAAAAV0%2F0ZxZ0O5lLK4%2Fs1600%2FDeTrend.png&hash=cc13211f61492702a3c2c0d60be2aa31)

OK, strictly I should use the relationship in the first scatter plot to develop a series of residuals and present those, but I've not updated that, I did do it some years ago. What I've had problems with is 'explaining' the residuals using indices such as temperature of the mid troposphere, Arctic Oscillation, Pacific/North American index etc..

In terms of prediction I think accounting for the residuals in the past series is the key. Whether the factors involved in those residuals can then be explained is another question entirely!

The reason I posted those two scatter plots is that I see initial volume (aka thickness) in April  as mainly explaining the trend, and not being a good predictor of variation around the trend.


If you do want to slew the conversation more firmly in the direction of prediction, there's a prediction thread we could move to here.
http://forum.arctic-sea-ice.net/index.php/topic,696.0.html (http://forum.arctic-sea-ice.net/index.php/topic,696.0.html)

Although strictly, IMO, prediction of this year is reasonable fallout from the April data, until May data is released.
Title: Re: Latest PIOMAS update (May)
Post by: Shared Humanity on May 18, 2014, 01:31:29 PM
CR.....

I love this melt season losses vs. April volume analysis. Looking at the 1st 2 charts, it seems to suggest that the most pessimistic forecasts for an ice free Arctic by 2030 might play out. The 2nd chart certainly suggests this but I do have a question.

What is the reason you have for April volume hitting a floor? Is this simply the result of the freeze volume preceding the melt or does it include a persistent MYI remnant along the CA? If it is the latter couldn't we also see a floor in the melt season as this persistent MYI just refuses to melt?

In this case it could be much later that the two actually meet.
Title: Re: Latest PIOMAS update (May)
Post by: crandles on May 18, 2014, 08:35:57 PM
CR.....

I love this melt season losses vs. April volume analysis. Looking at the 1st 2 charts, it seems to suggest that the most pessimistic forecasts for an ice free Arctic by 2030 might play out. The 2nd chart certainly suggests this but I do have a question.

What is the reason you have for April volume hitting a floor? Is this simply the result of the freeze volume preceding the melt or does it include a persistent MYI remnant along the CA? If it is the latter couldn't we also see a floor in the melt season as this persistent MYI just refuses to melt?

In this case it could be much later that the two actually meet.

Wrong CR but

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2F2.bp.blogspot.com%2F-VGyQONYbSkw%2FU1gORuu_nDI%2FAAAAAAAAAT8%2FLlN6VvyRcV0%2Fs1600%2FThinning.png&hash=0e67f48431d1b92f857b2561b0c8c36f)

The thick MYI ice has been thinning fast as it converts to FYI or is simply less old and has had less time to thicken mechanically. FYI has been thinning slowly and the very marginal ice zones where thickness rarely gets to 1m have hardly been thinning at all.

As we run out of MYI that is a lot thicker than FYI, then I think there is a good argument for the rate of decline to reduce to the rate of FYI thinning.

Why there would be a floor rather than a decline in rate to that of FYI isn't clear to me. You could perhaps add some other reasons like
1. River run-off not reaching the hard to melt areas.
2. What we have seen in the way of areas opening up is only areas where ice is moving out and it may be a different story when we get to areas where ice moves in from other areas.
3. Upward heat flux may have increased noticeably in shallow areas and less so in deeper areas.
4. All excess heat built up in ocean in summer gets vented to space before freeze up and there is enough time in winter for the ice to build back up to thermal equilibrium thickness.

For Chris Reynolds views, have you seen Chris Reynolds discussion at
http://dosbat.blogspot.co.uk/2014/04/what-is-future-of-arctic-sea-ice-part-2.html (http://dosbat.blogspot.co.uk/2014/04/what-is-future-of-arctic-sea-ice-part-2.html)
Title: Re: Latest PIOMAS update (May)
Post by: OSweetMrMath on May 19, 2014, 01:31:27 AM
Following Chris Reynolds's suggestion, I've posted my response to him on the Predicting PIOMAS Max Volume thread at http://forum.arctic-sea-ice.net/index.php/topic,696.0.html (http://forum.arctic-sea-ice.net/index.php/topic,696.0.html) . My post is long, but the one sentence summary is that using the anomaly data has a better outcome in terms of the bias-variance tradeoff than using the data from each month separately.
Title: Re: Latest PIOMAS update (May)
Post by: crandles on June 03, 2014, 11:54:22 PM
Day 151 31 May:
2014 20.288 4th lowest
2013 20.498
2012 19.591 2nd lowest
2011 19.483 lowest
2010 20.229 3rd lowest
2009 22.431
2008 22.878
2007 21.891

Average for May 2014 21.872 also 4th lowest but behind 2011, 2012 and 2013
Title: Re: Latest PIOMAS update (May)
Post by: Neven on June 04, 2014, 12:16:37 AM
Latest update is on the ASIB (http://neven1.typepad.com/blog/2014/06/piomas-june-2014.html), with a bonus from the NSIDC.
Title: Re: Latest PIOMAS update (May)
Post by: Andreas T on June 04, 2014, 01:04:11 AM
What I find striking is the difference in the cryostat thickness plot compared with the piomas gridded plot above (difference between april / may is probably not large in arctic basin). Do you think with icebridge backup cryostat is more convincing than piomas thickness? Hycom http://www7320.nrlssc.navy.mil/hycomARC/navo/arcticictnnowcast.gif (http://www7320.nrlssc.navy.mil/hycomARC/navo/arcticictnnowcast.gif)has much larger thickness in Beaufort can that be disregarded? Do we have to wait for the melt to show which has got it right?
Title: Re: Latest PIOMAS update (June)
Post by: Wipneus on June 04, 2014, 06:32:31 AM
Updated, graphs are in the top post (https://forum.arctic-sea-ice.net/index.php/topic,119.0.html).

(gridded data updated also, I will post the graphs later)
Title: Re: Latest PIOMAS update (June)
Post by: Wipneus on June 04, 2014, 07:37:05 AM
Apologies for still comparing 2014 with 2013, at the moment I only have time to update the existing graphs.

Here are the thickness graphs of May 2013 and 2014 and the difference. No surprises I think.
Title: Re: Latest PIOMAS update (June)
Post by: Wipneus on June 04, 2014, 07:54:11 AM
Difference in April-May thickness change (positive means more growth/less melt in 2014).

Title: Re: Latest PIOMAS update (June)
Post by: iceman on June 04, 2014, 02:37:03 PM
The slope of the anomaly trace has been shallower over the past two months than in recent years.  My guess is that this coming month it will be steeper (excepting 2012), because many areas that show an increase in thickness for May over April will experience rapid melt during June.
Title: Re: Latest PIOMAS update (May)
Post by: Nightvid Cole on June 10, 2014, 03:09:38 AM
Neven,

Thanks for reposting my post. One thing I didn't state, but is probably clear from the graph, is that this is based on the monthly data. The results probably would not differ greatly if I used the daily data instead.

wili,

A couple of points in response. The reliability of predictions is dependent on the goodness of fit of the model, and unfortunately, this model isn't that good.

The model assumptions of a SARIMA model are that the next month's value can be written as a weighted sum of all previous months, plus a noise term. The monthly noise is assumed to be constant variance and uncorrelated with the noise from all previous months.

The best model I can find (I used a (3,0,0)x(1,1,1) model) has noise with an increasing variance and no short term correlations, but longer term correlations are nonzero. Bigger models don't do much better, and this model is already bigger than I would like anyway.

What this means in practice is that the predictions out to a year or so probably aren't terrible, but the reliability goes down beyond that, so I'm not sure it makes much sense to look at the predictions for 2016.

If you do look at the prediction for September 2016, the minimum value for the confidence interval is 1.3 x 10^3 km^3. Keeping in mind that the confidence intervals are probably too small, this means that there is some non-zero probability that the ice minimum in 2016 will be less than 1000 km^3.

(But this interpretation is a Bayesian interpretation of a frequentist model, which is kind of sketchy from a statistical standpoint. Coming from a frequentist model, the correct interpretation of the confidence interval is a probability statement about the model. The interpretation above is making a probability statement about the ice volume.)

On the other hand, the model also states that there is an equal probability that the ice minimum in 2016 will be above 8500 km^3. Based on the record up to this point, I do not think these two probabilities are in fact equal.

You're conflating two issues: The first is that there is some uncertainty in the fit parameters due to weather noise behind the data currently available (For which we only have likelihood or odds ratio distributions, not probabilities absent a Bayesian prior), and the second is that, even given a set of fit parameters, there is a proability distribution of deviations from the fit in a given future year due to weather in *that* year (For which we can assign a "true" probability distribution even from the frequentist school of thought).
Title: Re: Latest PIOMAS update (June)
Post by: OSweetMrMath on June 10, 2014, 10:28:48 PM
Warning: philosophy of statistics.

I've done some searching and haven't found any references which directly address the interpretation of prediction intervals. The predictions are structured as future value = deterministic term + random term. If we assume we know the exact deterministic term and probability distribution for the random term, then the prediction interval is a statement about the distribution of future values. In the language I used previously, this is a Bayesian interpretation of the prediction interval. In fact, the confidence intervals I have computed are constructed under this assumption, which implies that Nightvid Cole is correct. Contrary to my qualms, the confidence intervals define probabilities that the ice volume will fall in certain ranges.

But I'm not sure that I buy that interpretation. For linear models, there are two confidence intervals associated with the model, which are sometimes called the fitted confidence interval and the predicted confidence interval. The fitted interval shows the error in the estimate of the mean value for the function. This is clearly a frequentist confidence interval, and shows the uncertainty in the estimate due to the random nature of the data used to generate the estimate.

The predicted confidence interval is an interval for new data values. This includes both the variability due to the estimation errors and the variability due to the random term in the original equation. Since the estimation error is a statement about the precision of the parameter estimates, and the noise error is a probability distribution, I'm not convinced that the prediction interval has a single coherent interpretation.

As a possible way out, we can go full frequentist. The claim then becomes that the September ice volume is already a fixed number, and we just don't know what it is yet. The prediction formula then becomes

future value = known deterministic term + unknown deterministic term

The known term represents stuff that we know about and can model. The unknown term is stuff which we can't model. Since we can't model it, effectively we assume that all the relevant parameters are zero, and then the random noise term from the previous model can be interpreted as a statement about the accuracy of the claim that all the unknown parameters are zero.

Under this interpretation, the prediction interval is a frequentist confidence interval, making a statement about the prediction accuracy, not a probability distribution. I think this interpretation is more consistent with the construction of the underlying model and with the different kinds of intervals that are used for linear models.

Like I said, I checked various textbooks and did some searching online, and I didn't find anywhere directly addressing this interpretation question. If there is a source which argues one way or the other, I would be interested in reading it.
Title: Re: Latest PIOMAS update (June)
Post by: jdallen on June 10, 2014, 10:58:27 PM
Following OSweetMrMath, it follows to *me* as a result that extent and area have a near impossible number of terms to rationalize sensibly.  Volume is what I'd try to focus on. To wit:

Future ice volume equals Current ice volume in CC
Plus/minus (total regional insolation in joules (predictable value)
                  Minus albedo loss
                  Minus re-radiation loss
                  Minus sensible heat loss (energy expended raising the temp of other stuff)
                  Plus heat import from other sources in joules
                 )
                 Divided by 334 (heat of fusion of ice in joules/CC)

I'd argue from this that extent and area are simply how the deck chairs are arranged.  They may affect re-radiation and albedo, and have a limited affect on heat uptake otherwise, but are not as key.
Title: Re: Latest PIOMAS update (June)
Post by: OSweetMrMath on June 10, 2014, 11:10:53 PM
jdallen,

On the other hand, one of the virtues of a noise term is that you can throw all the terms you don't want to (or can't) manage into the noise, and as long as the noise is well behaved, you don't have to worry about those terms any more. In fact, I've been working with models to forecast both the PIOMAS volume and the NSIDC extent, and based on their histories, the extent model is likely to be more reliable than the volume model. We'll have to wait and see how they actually play out this year.
Title: Re: Latest PIOMAS update (June)
Post by: crandles on June 11, 2014, 12:13:53 AM
I may well be talking rubbish, but I thought that I understood that

Confidence intervals represent the probability of data being in the range but only on the assumption that our model is in fact correct.

What you often want is a credible interval that only comes from Baysian probability. This is inherently subjective (requires a prior) and give your degree of confidence that the data will be in the range.

If you have a physics today subscription, maybe this might help
http://julesandjames.blogspot.co.uk/2007/04/data-analysis-frequently-bayesian.html (http://julesandjames.blogspot.co.uk/2007/04/data-analysis-frequently-bayesian.html)
Title: Re: Latest PIOMAS update (July)
Post by: Wipneus on July 08, 2014, 07:47:23 AM
Updated, graphs are in the top post (https://forum.arctic-sea-ice.net/index.php/topic,119.0.html).

(gridded data updated also, I will post the graphs later)
Title: Re: Latest PIOMAS update (July)
Post by: epiphyte on July 08, 2014, 09:24:31 AM
Delurking for a moment...

Look at the metrics we have for area, extent and volume. Is the volume estimated by the
PIOMAS model in part dictated by the other two... which would make any attempt to impute the health of the overall pack using volume/area an exercise in circular reasoning?

My own (totally unvalidated) hypothesis is that the health of the ice is better informed by surface:volume ratio than area/extent. This might help quantify the notion of ice "quality".... the larger the surface for a given volume in a given area, the more fragmented and vulnerable the ice...

Title: Re: Latest PIOMAS update (July)
Post by: Wipneus on July 08, 2014, 10:13:49 AM
Delurking for a moment...

Look at the metrics we have for area, extent and volume. Is the volume estimated by the
PIOMAS model in part dictated by the other two... which would make any attempt to impute the health of the overall pack using volume/area an exercise in circular reasoning?


epiphyte, PIOMAS brings in the thickness of the ice. With only extent and area there is no direct way  to establish thickness and therefore volume.
Title: Re: Latest PIOMAS update (July)
Post by: Wipneus on July 08, 2014, 10:18:54 AM
Here are the thickness graphs of June 2013 and 2014 and the difference.
Title: Re: Latest PIOMAS update (July)
Post by: Wipneus on July 08, 2014, 10:23:28 AM
And the difference in thickness change, the reds means less melt/more growth in 2014.
I think this shows that PIOMAS thinks large portions of the had less melt in June 2014.
Title: Re: Latest PIOMAS update (July)
Post by: DavidR on July 10, 2014, 05:11:43 AM
The thickness variation diagram for 2013 and 2014 is a good pointer to the reason PIOMAS is higher in June this year but still irrelevant to  final  extent. 

The ice is thinner in most of the areas likely to melt out but much thicker than 2013 in areas where the ice is already too thick to melt out.  It would be good to see a calculation of the volume of ice in the area that was above 2.5 m thickness last year, with a comparison for the same area in 2012 and 2014.  I suspect  the additional thickness in that  area alone would account for most of the additional volume this year. Thickness is above 1m greater for most of this area.  If this area covers 2M Km^2 that amounts to  an extra 2000 Km^3 in PIOMAS.

The extra thickness on the Atlantic edge of the pack in the Atlantic occurs from a very low thickness last year.  This ice is still thin enough to melt out and may be nothing more than an aberration caused by more ice drifting out of the central arctic than last year.
Title: Re: Latest PIOMAS update (July)
Post by: slow wing on July 10, 2014, 08:04:55 AM
Wipneus, so is that last plot the thickness change for: (June 2014 - May2014) - (same for 2013)?



I recall you asking for suggestions for the plot title; you could indicate the formula in the title...


"PIOMAS ice thickness trend: (June2014-May2014)-(June2013-May2013)".



Another option might be to write the formula on the legend.


"ice thickness change [m]: (June2014-May2014)-(June2013-May2013)".
Title: Re: Latest PIOMAS update (July)
Post by: epiphyte on July 11, 2014, 08:03:14 AM
Delurking for a moment...

Look at the metrics we have for area, extent and volume. Is the volume estimated by the
PIOMAS model in part dictated by the other two... which would make any attempt to impute the health of the overall pack using volume/area an exercise in circular reasoning?


epiphyte, PIOMAS brings in the thickness of the ice. With only extent and area there is no direct way  to establish thickness and therefore volume.

That's understood. What I'm trying to get at is that PIOMAS imputes volume using (in part) the area, + discrete measurements + gridded estimates of thickness, and some here go on to impute the average thickness from the PIOMAS volume, and then use that as an indicator of the robustness of the ice. Doesn't this just reduce the information content of the measurements + model output?



Title: Re: Latest PIOMAS update (July)
Post by: crandles on July 11, 2014, 12:06:15 PM
Delurking for a moment...

Look at the metrics we have for area, extent and volume. Is the volume estimated by the
PIOMAS model in part dictated by the other two... which would make any attempt to impute the health of the overall pack using volume/area an exercise in circular reasoning?


epiphyte, PIOMAS brings in the thickness of the ice. With only extent and area there is no direct way  to establish thickness and therefore volume.

That's understood. What I'm trying to get at is that PIOMAS imputes volume using (in part) the area, + discrete measurements + gridded estimates of thickness, and some here go on to impute the average thickness from the PIOMAS volume, and then use that as an indicator of the robustness of the ice. Doesn't this just reduce the information content of the measurements + model output?

I think the modelled thickness is improved by assimilating actual data but largely because there are hindcasts where parameters are tweaked so that the minimum adjustments to assimilated information is necessary. 

I think this ensures the modelled thickness is more consistent to actual over time. It could well be consistently wrong if the model is poor but when compared to icesat2, volumes seem very similar at minimum but PIOMAS understates volume most at maximum.

Under assimilation, PIOMAS is adjusted to actual extent and area. Apart from this, thickness comes from the PIOMAS model. These seem nearly* independent so I don't see any circular reasoning.


*nearly: differences between model and actual extent/area used to tweak parameters seems close to independent from actual extent/area to me. Other people may disagree about this.
Title: Re: Latest PIOMAS update (July)
Post by: A-Team on July 11, 2014, 07:55:12 PM
Wipneus, I notice sometimes your palettes are measured gray scale steps with a hue overtint. Other times, not. In the first case, I can drop them into PovRay freeware for a 3D perspective view (for what that is worth). Script:

include "colors.inc"
  camera{
    location <-15,20,-31>
    look_at 0
    angle 35
  }
  light_source{ <1000,1000,-1000> White }
  height_field {
    png "t2gray.png"
    smooth
    pigment { White }
    translate <-.5, -.5, -.5>
    scale <17, 2, 17>
      texture{pigment{
                     gradient y
                     color_map {
   [ 0.00000 rgb < 1.00000, 0.01111, 0.05829> ]
   [ 0.05000 rgb < 0.99728, 0.68188, 0.62282> ]
   [ 0.10000 rgb < 0.99457, 0.43569, 0.12356> ]
   [ 0.20000 rgb < 0.99457, 0.65239, 0.12521> ]
   [ 0.30000 rgb < 0.99457, 0.87889, 0.06625> ]
   [ 0.40000 rgb < 0.83409, 0.99457, 0.02736> ]
   [ 0.50000 rgb < 0.38010, 0.99457, 0.07204> ]
   [ 0.60000 rgb < 0.05287, 0.99457, 0.64586> ]
   [ 0.65000 rgb < 0.46341, 0.97697, 0.89598> ]
   [ 0.70000 rgb < 0.04840, 0.95938, 0.99457> ]
   [ 0.75000 rgb < 0.43931, 0.82767, 0.99457> ]
   [ 0.80000 rgb < 0.09890, 0.49815, 0.99457> ]
   [ 0.90000 rgb < 0.16623, 0.08811, 0.99457> ]
   [ 1.00000 rgb < 0.47403, 0.02386, 0.99457> ]
} }}  }
Title: Re: Latest PIOMAS update (July)
Post by: Wipneus on July 12, 2014, 03:52:48 PM
Wipneus, I notice sometimes your palettes are measured gray scale steps with a hue overtint. Other times, not.

A-Team, I guess that is because thickness asks for a "sequential palette", going from 0->max. For changes a "diverging palette" is appropriate going from thinner->neutral->thicker.

"sequential" and "diverging" definition taken from the color brewer man page:

     There are 3 types of palettes, sequential, diverging, and
     qualitative.
     1. Sequential palettes are suited to ordered data that progress
     from low to high.  Lightness steps dominate the look of these
     schemes, with light colors for low data values to dark colors for
     high data values.
     2. Diverging palettes put equal emphasis on mid-range critical
     values and extremes at both ends of the data range. The critical
     class or break in the middle of the legend is emphasized with
     light colors and low and high extremes are emphasized with dark
     colors that have contrasting hues.
     3. Qualitative palettes do not imply magnitude differences between
     legend classes, and hues are used to create the primary visual
     differences between classes.  Qualitative schemes are best suited
     to representing nominal or categorical data.

For the thickness maps I use a R-builtin palette called "terrain colors", for the changes the color brewer palette named "Spectral".

Attached are the R-builtin palettes and those from color brewer.
Title: Re: Latest PIOMAS update (August)
Post by: Wipneus on August 05, 2014, 07:12:52 AM
Updated, graphs are in the top post (https://forum.arctic-sea-ice.net/index.php/topic,119.0.html).
Title: Re: Latest PIOMAS update (August)
Post by: Andir on August 05, 2014, 08:17:44 AM
Volume anomalie isn't so big this year. How large is the influence because of the slow Fram export in your opinion?
Title: Re: Latest PIOMAS update (August)
Post by: Wipneus on August 05, 2014, 08:25:38 AM
Volume anomalie isn't so big this year. How large is the influence because of the slow Fram export in your opinion?

It did not help, but low Fram export in the summer is not unusual.
Title: Re: Latest PIOMAS update (August)
Post by: Wipneus on August 05, 2014, 08:37:33 AM
Here are the thickness graphs of July 2013 and 2014 and the differences.
Title: Re: Latest PIOMAS update (August)
Post by: Wipneus on August 05, 2014, 08:43:50 AM
And the difference in thickness change in July (red is morelessmore thickening or lessmoreless thinning).
Title: Re: Latest PIOMAS update (August)
Post by: slow wing on August 05, 2014, 10:23:49 AM
Fascinating! Thanks, Wipneus!



The volume has split right away upwards from 2013 and is now hanging out with 2009 and 2007!



It's going to take a lot of melt in the next month or so to get back to the post-2009 years at minimum. Otherwise, we will end up back around the minimum volume levels of the 2007-2009 years!
Title: Re: Latest PIOMAS update (August)
Post by: crandles on August 05, 2014, 02:18:26 PM
PIOMAS         
Year, fall to min _31/7 __minimum
2005   3.094   12.253   9.159
2006   2.946   11.939   8.993
2007   2.714   9.172   6.458
2008   4.360   11.432   7.072
2009   2.974   9.813   6.839
2010   2.823   7.405   4.582
2011   2.677   6.979   4.302
2012   3.003   6.676   3.673
2013   2.403   7.795   5.392

Year   _ Fall __ If follows this fall   
2005   3.094   6.481   
2006   2.946   6.629   
2007   2.714   6.861   
2008   4.360   5.215   
2009   2.974   6.601   
2010   2.823   6.752   
2011   2.677   6.898   
2012   3.003   6.572   
2013   2.403   7.172   

         
07+Average____   2.993   6.582   6th lowest
07+Average+3sd   4.900   4.675   4th lowest
07+Average+2sd   4.265   5.310   4th lowest
07+Average+sd   3.629   5.946   5th lowest
07+Average-sd   2.358   7.217   8th lowest
07+Average-2sd   1.722   7.853   8th lowest

2008 looks a bit of an outlier having a large fall and it was from a high quantity at 31st July. Excluding that, I get

07+9-13Avg___   2.766   6.809   6th lowest
07+9-13Avg+3sd   3.430   6.145   5th lowest
07+9-13Avg+2sd   3.208   6.367   5th lowest
07+9-13Avg+sd   2.987   6.588   6th lowest
07+9-13Avg-sd   2.544   7.031   7th lowest
07+9-13Avg-2sd   2.323   7.252   8th lowest

So currently 6th lowest and at minimum seems likely (2sd range) to be 5th to 8th lowest.
Title: Re: Latest PIOMAS update (August)
Post by: Nightvid Cole on August 05, 2014, 02:59:03 PM
Fascinating! Thanks, Wipneus!



The volume has split right away upwards from 2013 and is now hanging out with 2009 and 2007!



It's going to take a lot of melt in the next month or so to get back to the post-2009 years at minimum. Otherwise, we will end up back around the minimum volume levels of the 2007-2009 years!

There's no such thing as "the post 2009 years", apparently, as far as PIOMAS volume is concerned. Just fluctuations superimposed on a long term decline, even though the latter still appears significantly nonlinear.
Title: Re: Latest PIOMAS update (August)
Post by: iceman on August 05, 2014, 03:00:04 PM
I'm quite surprised at the upturn in the anomaly trace: steeper this past month than in any recent year.  Judging from your last graph, much of the anomaly increase comes from slower thinning in the central part of the ice pack. (more so than in the comparable graph from a month ago)  Is this attributable to the unusually high compactness in 2014?
Title: Re: Latest PIOMAS update (August)
Post by: Wipneus on August 05, 2014, 04:56:40 PM
I'm quite surprised at the upturn in the anomaly trace: steeper this past month than in any recent year.  Judging from your last graph, much of the anomaly increase comes from slower thinning in the central part of the ice pack. (more so than in the comparable graph from a month ago)  Is this attributable to the unusually high compactness in 2014?

Yes of course. Directly because the thickness of a grid box is really the average thickness ( the modelers call it effective thickness) of the ice. If concentration goes up, the average goes up because the box contains more ice and less open water.

Indirectly because compacter ice absorbs less incoming solar.

Further I am convinced that part of the increased compactness as far as it is measured with data like the NSIDC sea ice concentration data is explained by the low temperatures resulting in less melting, dryer surface. Obviously that is also going along with less thinning.
Title: Re: Latest PIOMAS update (August)
Post by: NeilT on August 05, 2014, 06:48:31 PM
Help me out here, but didn't we see, earlier in the year, buoy data which showed low temperatures on the surface and significant bottom melt at the same time?

Wasn't that around where the "thick ice" is now vanishing in the Beaufort?

I know that PIOMAS has been accused of overestimating in certain circumstances.  Could it be that if there is a cold snap and we see 5cm ice in an area of 1M ice that PIOMAS will average it all as 1M?

Just thinking out loud.

[edit]

I also recall Dr Barber talking about this phenomena when he did his presentation on rotten sea ice. Where areas of very thick but disintegrating ice was being averaged as all the same thickness when it was, in fact, largely thinner ~10cm ice with thicker ice holding it all together.
Title: Re: Latest PIOMAS update (August)
Post by: jdallen on August 05, 2014, 07:30:36 PM
Help me out here, but didn't we see, earlier in the year, buoy data which showed low temperatures on the surface and significant bottom melt at the same time?

Wasn't that around where the "thick ice" is now vanishing in the Beaufort?

I know that PIOMAS has been accused of overestimating in certain circumstances.  Could it be that if there is a cold snap and we see 5cm ice in an area of 1M ice that PIOMAS will average it all as 1M?

Just thinking out loud.

[edit]

I also recall Dr Barber talking about this phenomena when he did his presentation on rotten sea ice. Where areas of very thick but disintegrating ice was being averaged as all the same thickness when it was, in fact, largely thinner ~10cm ice with thicker ice holding it all together.

I think you are on the right track, if not the exact detail.

While we are increasing the data we have available about volume, we are limited by scale and resolution.  When Icebridge flew over the Beaufort, ESS and Chukchi, it showed large amounts of MYI in place. It did not clearly describe its construction, or how in August it would come to look like this:

(Chukchi/Beaufort north of Bearing strait)
http://map2.vis.earthdata.nasa.gov/imagegen/index.php?TIME=2014217&extent=-2076192,-121792,-1138208,699456&epsg=3413&layers=MODIS_Terra_CorrectedReflectance_TrueColor,arctic_coastlines_3413&format=image/jpeg&width=1832&height=1604 (http://map2.vis.earthdata.nasa.gov/imagegen/index.php?TIME=2014217&extent=-2076192,-121792,-1138208,699456&epsg=3413&layers=MODIS_Terra_CorrectedReflectance_TrueColor,arctic_coastlines_3413&format=image/jpeg&width=1832&height=1604)

I think we are struggling greatly to understand the effect structural changes in the ice will have on both its behavior and regional weather.
Title: Re: Latest PIOMAS update (August)
Post by: SCYetti on August 06, 2014, 03:56:19 AM
The PIOMAS validation page states that their model has a bias that under estimates thick ice and over estimates thin ice. What is the effect of this when the Arctic ice is overwhelmingly thin.
Title: Re: Latest PIOMAS update (August)
Post by: jbatteen on August 06, 2014, 05:24:26 AM
Looks like a lot of the thickening is in areas of thin ice on the periphery that shouldn't be too hard to get rid of.  While a lot of thinning is in the reserve of MYI that's holding everything together.
Title: Re: Latest PIOMAS update (August)
Post by: ChasingIce on August 06, 2014, 06:23:56 AM
The PIOMAS validation page states that their model has a bias that under estimates thick ice and over estimates thin ice. What is the effect of this when the Arctic ice is overwhelmingly thin.

apparently, it would over-estimate thin ice, and under-estimate thick(er) ice. 
Title: Re: Latest PIOMAS update (August)
Post by: epiphyte on August 06, 2014, 06:31:40 AM
SCYetti writes:

The PIOMAS validation page states that their model has a bias that under estimates thick ice and over estimates thin ice. What is the effect of this when the Arctic ice is overwhelmingly thin

I've been wondering about that too. W.r.t the August update I find it especially intriguing that from wipneus' chart : "PIOMAS modeled ice June-July thickness change 2014-2013" it looks at first glance (as jbatteen alludes to above) as though as almost all of the
reddest areas (i.e. more thickening/less thinning) are at the periphery (i.e. - where the ice is probably thinnest... and where PIOMAS is most likely to overestimate). It also appears from comparison with MODIS that as of Aug 04. almost all of these deep red areas are over open water... which causes me to question the practical value of this model in predicting the seasonal fate of first-year ice.
Title: Re: Latest PIOMAS update (August)
Post by: ktonine on August 06, 2014, 07:08:10 AM
It also appears from comparison with MODIS that as of Aug 04. almost all of these deep red areas are over open water... which causes me to question the practical value of this model in predicting the seasonal fate of first-year ice.

Yes, it seems rather odd that the ice has gained thickness precisely in those areas where there is no ice.

I have been confused a number of times over the past two melting seasons.  I'll just add this to the growing list of things I simply cannot comprehend.
Title: Re: Latest PIOMAS update (August)
Post by: Wipneus on August 06, 2014, 09:40:32 AM
Help me out here, but didn't we see, earlier in the year, buoy data which showed low temperatures on the surface and significant bottom melt at the same time?

Let me hasten to say that most what I said is relative. I have no doubt that if the temperature on the surface were not "low", the melt would have been even higher.


Wasn't that around where the "thick ice" is now vanishing in the Beaufort?


Did it? I have looked at the images from february and it seems a good portion of that thick ice has moved on with the Beaufort/Arctic gyre.


I know that PIOMAS has been accused of overestimating in certain circumstances.  Could it be that if there is a cold snap and we see 5cm ice in an area of 1M ice that PIOMAS will average it all as 1M?


That is not how PIOMAS works. It is a physical model that result in modeling data. When comparing the model data with real data, the thinner ice is found to be overestimated (and thicker ice underestimated) at least in the comparison period up to 2010. That is not explicitly built in, it is an "emerging" feature of the model.
Title: Re: Latest PIOMAS update (August)
Post by: Wipneus on August 06, 2014, 09:57:43 AM

Yes, it seems rather odd that the ice has gained thickness precisely in those areas where there is no ice.

I have been confused a number of times over the past two melting seasons.  I'll just add this to the growing list of things I simply cannot comprehend.

Sorry guys, I must have been confused. The reds are more thinning in 2014.

So where there is ice in 2014, but none in 2013 (eg Barents Sea) you will see red because the thinning in 2013 was zero.
And where there is no ice in 2014, but in 2013 there was (eg Beaufort) you will see blue because thinning in 2014 is none.
Title: Re: Latest PIOMAS update (August)
Post by: Neven on August 06, 2014, 10:35:57 AM
I have put up the latest PIOMAS update on the ASIB: PIOMAS August 2014 (http://neven1.typepad.com/blog/2014/08/piomas-august-2014.html).

From the conclusion:

After the lessons of 2012 and 2013, showing the importance of the start of the melting season, it's fascinating to see the theory confirmed again. A lack of melt ponds during May, and very litle movement, even during times when high-pressure areas dominate, seem to have serious implications for how much the ice pack recedes and thins during the melting season.

Equally fascinating will be to see how high volume can end up this year, perhaps even doubling the rebound from last year. And of course, what it will all mean for melting seasons to come. But there's still a couple of weeks of melt to come before drawing any preliminary conclusions.
Title: Re: Latest PIOMAS update (August)
Post by: NeilT on August 06, 2014, 12:05:12 PM
Thanks wipneus.  I just read stuff and get impressions. Then I ask questions.  Nice to know.

I'm just watching to see what is happening right now.  The pack appears, from the modis images, to be in a worse state every year.  Yet the volume keeps going up.

Something doesn't match.

Looking at the Modis images The entire eastern side of the pack, from Svalbard through to the Chuchki, looks more like a flotilla floating in concert than an ice pack.  In such a scenario I would have thought that the ice would have had to be much greater thickness than is actually evident to give such high volume figures.

That's just an observation mind you.  No science behind it at all and could quite likely be wrong.

As for the thick ice moving on.  Where would it have gone?  As we see from the thickness graphs, the entire eastern side of the pack is thin or first year, even trending back into the pole.  Has they gyre moved it back into the CAA?
Title: Re: Latest PIOMAS update (August)
Post by: Steven on August 06, 2014, 01:15:09 PM
Sorry guys, I must have been confused. The reds are more thinning in 2014.

Wipneus, I think the original (unedited) version of Reply #275 upthread was the correct one.  The red color means that there was less thinning in 2014 than in 2013.


where there is no ice in 2014, but in 2013 there was (eg Beaufort) you will see blue because thinning in 2014 is none.

Replacing the word "blue" by "red" in the quoted sentence, it becomes:   

"where there is no ice in 2014, but in 2013 there was ice (e.g. in southern Beaufort/Chukchi) you will see red because thinning in 2014 is none."
Title: Re: Latest PIOMAS update (August)
Post by: iceman on August 06, 2014, 01:53:16 PM
Sorry guys, I must have been confused. The reds are more thinning in 2014.

Wipneus, I think the original (unedited) version of Reply #275 upthread was the correct one.  The red color means that there was less thinning in 2014 than in 2013.

That's the way I read it as well.  If an area was mostly melted out by June 2014, it will show red as "less thinning" as of July 2014.
   The combination of month/month and year/year comparisons makes this a little tricky to interpret: previous sentence is predicated on 2013 having more July thinning in the area being compared.
Title: Re: Latest PIOMAS update (August)
Post by: Wipneus on August 06, 2014, 02:29:28 PM
red color is less thinning in 2014

Let me see. What I am displaying is the difference between two subtractions:

  ( thk(2014,7) - thk(2014,6) )   -     ( thk(2013,7) - thk(2013,6) )

thinning means that thickness in July is less than in June, so these subtractions have negative results.

Less thinning means the number on the left side is less negative than on the right.

So the result is positive.

Look at the legend: red is positive.

So it is true that red is less thinning.

Now what did I write, hmm, grrm. I need a vacation.
Title: Re: Latest PIOMAS update (August)
Post by: iceman on August 06, 2014, 04:29:27 PM
Now what did I write, hmm, grrm. I need a vacation.
                                                    ... or a nap.
Title: Re: Latest PIOMAS update (August)
Post by: ChrisReynolds on August 06, 2014, 08:19:39 PM
Now what did I write, hmm, grrm. I need a vacation.
                                                    ... or a nap.

It's reassuring to find that Wipneus sometimes finds these things confusing, I may be in good company in that respect, but for the record - Wipneus's mathematical ability beats mine any day.
Title: Re: Latest PIOMAS update (August)
Post by: Frivolousz21 on August 06, 2014, 08:33:39 PM
Thanks wipneus.  I just read stuff and get impressions. Then I ask questions.  Nice to know.

I'm just watching to see what is happening right now.  The pack appears, from the modis images, to be in a worse state every year.  Yet the volume keeps going up.

Something doesn't match.

Looking at the Modis images The entire eastern side of the pack, from Svalbard through to the Chuchki, looks more like a flotilla floating in concert than an ice pack.  In such a scenario I would have thought that the ice would have had to be much greater thickness than is actually evident to give such high volume figures.

That's just an observation mind you.  No science behind it at all and could quite likely be wrong.

As for the thick ice moving on.  Where would it have gone?  As we see from the thickness graphs, the entire eastern side of the pack is thin or first year, even trending back into the pole.  Has they gyre moved it back into the CAA?

It's the MYI.  It's just in shambles and piomas thinks it's thicker than it is. That simple.



(https://forum.arctic-sea-ice.net/ftp://ccar.colorado.edu/pub/tschudi/iceage/gifs/age2014_31.gif)


Title: Re: Latest PIOMAS update (August)
Post by: OSweetMrMath on August 06, 2014, 09:37:50 PM
I usually work from the monthly data from PIOMAS, but it doesn't seem to have been updated yet, even though the daily data is clearly out for July. Does anyone else use the monthly data? Have you gotten the updated numbers? Anyone have any info on why it's not updated yet?
Title: Re: Latest PIOMAS update (August)
Post by: ChrisReynolds on August 06, 2014, 09:51:58 PM
OSMM,

I don't use it, but you're right, it's not been updated. Don't know why, daily and gridded is OK.
Title: Re: Latest PIOMAS update (August)
Post by: SCYetti on August 07, 2014, 12:43:30 AM

Posted by: ChasingIce
« on: August 06, 2014, 06:23:56 AM » Insert Quote
: SCYetti  August 06, 2014, 03:56:19 AM
The PIOMAS validation page states that their model has a bias that under estimates thick ice and over estimates thin ice. What is the effect of this when the Arctic ice is overwhelmingly thin.

apparently, it would over-estimate thin ice, and under-estimate thick(er) ice
Really? Well, duh! :P
Obviously I did not express myself adequately. I wanted quantification rather than verification. I should have asked " How great would be the effects of over-estimating thin ice would be.
Title: Re: Latest PIOMAS update (August)
Post by: epiphyte on August 07, 2014, 02:38:21 AM
So it is true that red is less thinning.

Now what did I write, hmm, grrm. I need a vacation.

..As do I - especially w.r.t my previous comment. I was interpreting the reduction in thinning at the edges as being due to an underestimate by the model... but duh... there was no ice in the first place!

(otoh - it might be a good idea to mask off the open water on that graphic, though...)





Title: Re: Latest PIOMAS update (August)
Post by: Frivolousz21 on August 07, 2014, 04:04:50 AM
A lot of "thicker" ice according to piomas biting the dust in grand fashion.

Not saying piomas is crap.  But it seems to have over estimated some areas or what folks have been preaching to me on different websites about how August can't get the "big" melts is wrong. 

I have contended if the weather is right August can have huge melting.  We will see.

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fi.imgur.com%2FbWEch9N.png%3F1&hash=0c8d69a04325846b2c40b1a6410181c0)
Title: Re: Latest PIOMAS update (August)
Post by: epiphyte on August 07, 2014, 04:59:28 AM
Friv writes:

I have contended if the weather is right August can have huge melting.  We will see.

I'm inclined to agree. Not least because once the ice is mobile, and once significant waves can form,  the weather can have all kinds of effects that have never heretofore been in play. There is a huge reservoir of energy in the water surrounding the arctic, and more only a few meters beneath the ice.

As I've said before I'm not predicting it will happen this year - if $100,000,000 worth of super-computers and the best brains in the business can't get the next week straight, I'm not about to try. But I do agree with Friv that that August is when it will be decided. Whether this year or another in the near future, I don't know.




Title: Re: Latest PIOMAS update (August)
Post by: ChrisReynolds on August 07, 2014, 06:34:29 PM
A lot of "thicker" ice according to piomas biting the dust in grand fashion.

Actually PIOMAS July figures show that virtually all the increase in volume is due to ice between 3 and 3.9m thick in the Central Arctic (70% of the increase in volume from July 2012 to July 2014). What PIOMAS does not show, unlike HYCOM, is a tongue of thicker multi year ice from Beaufort to the ESS.
Title: Re: Latest PIOMAS update (September)
Post by: Wipneus on September 04, 2014, 06:54:16 AM
Updated, graphs are in the top post (https://forum.arctic-sea-ice.net/index.php/topic,119.0.html).

(gridded data updated also, I will post the graphs later)
Title: Re: Latest PIOMAS update (September)
Post by: Wipneus on September 04, 2014, 08:18:53 AM
Here are the August 2013 /2014 thickness maps, as well as the differences.

Title: Re: Latest PIOMAS update (September)
Post by: Wipneus on September 04, 2014, 08:23:20 AM
An here is the August thickness change difference (2013/2014). Red means more thickening or less thinning than last year (which gives some headaches in areas that are open water in one year and ice covered in the other).
Title: Re: Latest PIOMAS update (September)
Post by: iceman on September 04, 2014, 12:24:37 PM
Thanks for the update.  Your last two graphics indicate that the relative y/y gain in thickness in the central area of the pack - a notable feature of this year's melt season, along with concentration in the same location - has mostly carried over from the previous month's PIOMAS data.
      Looking at the anomaly graphic on Arctische Pinguin, the recent uptrend is consistent with recent years, yet still a surprise to me.  I had thought the steep incline during July was something of a mid-season aberration, to be partly reversed.
Title: Re: Latest PIOMAS update (September)
Post by: ChrisReynolds on October 02, 2014, 05:40:39 PM
http://www.esrl.noaa.gov/psd/cgi-bin/data/composites/printpage.pl (http://www.esrl.noaa.gov/psd/cgi-bin/data/composites/printpage.pl)

  At this time (2014/09/29), the NCEP/NCAR Reanalysis is not being updated at PSD as NCEP has halted their distribution. Any of our products or web-tools that use this data will be impacted. Data will be updated when it becomes available. We have no further information as to when that might be.

Will this impact PIOMAS?

If it persists it will certainly impact my blogging.
Title: Re: Latest PIOMAS update (September)
Post by: viddaloo on October 02, 2014, 05:50:59 PM
What's up, Chris? Are you saying there will be no PIOMAS October release? The US Govt is stopping it, effectively ending the 1979-2014 data series?
Title: Re: Latest PIOMAS update (September)
Post by: ChrisReynolds on October 02, 2014, 05:55:56 PM
I don't know, but PIOMAS is forced by NCEP/NCAR reanalysis data, no reanalysis data for September, no PIOMAS data for September.

Dr Zhang probably downloads as netcdf, I don't know if that is blocked too, but at present NCEP/NCAR reanalysis is suspended.

I do not know for how long.

EDIT - check out this Google search (http://"https://www.google.co.uk/?gfe_rd=cr&ei=v3QtVIHGGNLH8gfIl4CgBw#q=%22the+NCEP/NCAR+Reanalysis+is+not+being+updated+at+PSD%22&safe=off&filter=0"). Only one other person is asking what has happened and I've drawn a blank as to why.
Title: Re: Latest PIOMAS update (September)
Post by: viddaloo on October 02, 2014, 05:58:28 PM
Now, why would the Obama administration make such a dramatic move? Fire under his presidential behind?


This is probably why weather and climate should never be Weather.GOV or Climate.GOV.
Title: Re: Latest PIOMAS update (September)
Post by: ChrisReynolds on October 02, 2014, 06:15:39 PM
I've emailed Dr Zhang.
Title: Re: Latest PIOMAS update (September)
Post by: ChrisReynolds on October 02, 2014, 06:17:45 PM
Now, why would the Obama administration make such a dramatic move? Fire under his presidential behind?


This is probably why weather and climate should never be Weather.GOV or Climate.GOV.

OK I'll bite. There are plenty of mundane reasons why there might be a glitch in the reanalysis data update. So why start stooping to conspiracy theory nonsense?  ::)
Title: Re: Latest PIOMAS update (September)
Post by: viddaloo on October 02, 2014, 06:22:58 PM
If one man decides to end a climate data service it's by definition not a conspiracy, hence no conspiracy theories are involved here. :)
Title: Re: Latest PIOMAS update (September)
Post by: ChrisReynolds on October 02, 2014, 07:24:06 PM
There has been a technical problem at NCEP. Dr Zhang confirms that the September PIOMAS data will be delayed until the issue is resolved and reanalysis data is available.
Title: Re: Latest PIOMAS update (September)
Post by: viddaloo on October 02, 2014, 07:31:39 PM
OK. Computer problem or real-life observation problem? And why don't they use the excellent communication medium that their website is to communicate this message?
Title: Re: Latest PIOMAS update (September)
Post by: Neven on October 03, 2014, 09:19:38 AM
Come on, don't exaggerate, viddaloo.
Title: Re: Latest PIOMAS update (September)
Post by: viddaloo on October 03, 2014, 09:52:28 AM
Come on, don't exaggerate, viddaloo.

We simply disagree, Neven, no big deal. I think the web can be used for communicating info, others don't think that can be done via a website.
Title: Re: Latest PIOMAS update (September)
Post by: jdallen on October 03, 2014, 06:21:02 PM
Come on, don't exaggerate, viddaloo.

We simply disagree, Neven, no big deal. I think the web can be used for communicating info, others don't think that can be done via a website.
Others, who are in the industry, and know the bureaucracy, understand just how glacial change in websites can be.   :o

Never ascribe to malice what can be explained by inefficiency or indifference.
Title: Re: Latest PIOMAS update (September)
Post by: viddaloo on October 03, 2014, 06:44:34 PM
Granted. Yet you must agree that 1) not displaying any notice on their website within a week, 2) not telling anyone online what sort of issue is allegedly haunting the NCEP, and 3) not being able to tell anyone online what day, month, year or decade the service will be back, if at all, or 4) whether it will ever be back, is a tad excentric.

Begs the question: Are we living in the Information Age or the Dark Ages?
Title: Re: Latest PIOMAS update (September)
Post by: ChrisReynolds on October 03, 2014, 11:17:56 PM
Viddaloo,

Stop wriggling. You're wrong.

You started off with a mindless conspiracy theory about the loss of data being due to the US administration wanting to hush things up, now you're making childish demands without having the foggiest what is going on.

If my house had been broken into and I couldn't fix the locks, the last thing I would do would be put up a sign announcing the fact.

You really are very, very tiresome.  >:(
Title: Re: Latest PIOMAS update (September)
Post by: viddaloo on October 04, 2014, 12:06:00 AM
I think not telling anyone is excentric, you don't. This world would be a boring place if everyone on the planet thought it was excentric, or, on the other hand, if everyone on the planet thought it wasn't excentric, right?

In other words, we disagree on this one. It's not the end of the world.

Worse things happen at sea.

Calm down.

Breathe.

Good.
Title: Re: Latest PIOMAS update (September)
Post by: OSweetMrMath on October 04, 2014, 12:14:47 AM
The only "official" news I've found on this is at the ESRL PSD site (http://www.esrl.noaa.gov/psd/data/gridded/data.ncep.reanalysis.html (http://www.esrl.noaa.gov/psd/data/gridded/data.ncep.reanalysis.html)) which has been updated today to say "As of 2014/10/03, the NCEP/NCAR Reanalysis 1 is being updated at PSD. Some products are catching up and we don't yet know when normal distribution will return at NCEP." Hopefully this means that this was a temporary problem and PIOMAS will be updated soon.

Before I found that, I went to the NCEP/NCAR Reanalysis Wikipedia page (http://en.wikipedia.org/wiki/NCEP/NCAR_Reanalysis (http://en.wikipedia.org/wiki/NCEP/NCAR_Reanalysis)), which generally needs help, but it was revised about a day ago to read that the updates stopped in September 2014.

The update was made anonymously and does not have a citation. Does anyone here know anything about the Wikipedia change? In any event, based on the update at PSD, the change on the Wikipedia page does not appear to be correct.
Title: Re: Latest PIOMAS update (September)
Post by: viddaloo on October 04, 2014, 12:27:11 AM
Seems strange to criticise someone who's asking what sort of technical issue it is, for not knowing enough about the sort of technical issue involved. Rather than calling that "making childish demands", one could view it as a method of getting to know what sort of technical issue we're talking about. Had you known more about the type of issue, Chris, you probably would just say so.

Asking someone who might know is a great way of getting to know more. I know a lot of people disagree with me on this one. But people are different, and that's a good thing.
Title: Re: Latest PIOMAS update (September)
Post by: ChrisReynolds on October 04, 2014, 07:01:29 AM
Seems strange to criticise someone who's asking what sort of technical issue it is, for not knowing enough about the sort of technical issue involved. Rather than calling that "making childish demands", one could view it as a method of getting to know what sort of technical issue we're talking about. Had you known more about the type of issue, Chris, you probably would just say so.

Asking someone who might know is a great way of getting to know more. I know a lot of people disagree with me on this one. But people are different, and that's a good thing.

If I am told something in a private conversation, and if I suspect it might be information that one probably shouldn't make public, would it not be dishonourable for me to say such a thing publicly?

The reason I said it publicly here is because I noticed that on another thread (effective thickness) you alluded to such a reason - so I presumed the matter was now in the public domain.
Title: Re: Latest PIOMAS update (September)
Post by: ChrisReynolds on October 04, 2014, 07:03:23 AM
New announcement:

As of 2014/10/03, the NCEP/NCAR Reanalysis 1 is being updated at PSD. Some products are catching up and we don't yet know when normal distribution will return at NCEP.
http://www.esrl.noaa.gov/psd/data/composites/day/ (http://www.esrl.noaa.gov/psd/data/composites/day/)
Title: Re: Latest PIOMAS update (September)
Post by: viddaloo on October 04, 2014, 07:23:26 AM
Just taking a wild/educated guess based on the excessive secrecy of this matter. Let's hope it all comes up again nicely and that no data are lost.
Title: Re: Latest PIOMAS update (September)
Post by: ChrisReynolds on October 04, 2014, 09:23:49 AM
I doubt if data will be lost, looks like there's a chance of having PIOMAS data by the end of the week (if they're already putting things right at NCEP/NCAR).
Title: Re: Latest PIOMAS update (September)
Post by: Neven on October 04, 2014, 09:32:07 AM
Humans are involved, that's all I need to now. And as I'm human myself, I try not to interpret or judge too much.  ;D
Title: Re: Latest PIOMAS update (September)
Post by: ChrisReynolds on October 06, 2014, 09:19:51 PM
Not long to wait now folks.

Then we can see how much 'baggage' the sea ice will carry into winter 2014/15.  8)
Title: Re: Latest PIOMAS update (September)
Post by: viddaloo on October 06, 2014, 09:30:47 PM
Great, Chris! :)

PS: Is anything official yet about the outage?
Title: Re: Latest PIOMAS update (September)
Post by: ChrisReynolds on October 06, 2014, 10:11:24 PM
Great, Chris! :)

PS: Is anything official yet about the outage?

Nope. Dr Zhang has said it is just what he heard and may be wrong. Another scientist told me the same thing, but that doesn't mean anything if it is a rumour in the community.

Anyway. I'm winding down for the evening. So if the data is released tonight (later afternoon in the US), I'll have to leave doing something about it until tomorrow night.
Title: Re: Latest PIOMAS update (September)
Post by: diablobanquisa on October 07, 2014, 12:49:09 AM

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fimages.meteociel.fr%2Fim%2F7121%2FBPIOMASIceVolumeAnomalyCurrentV2.1_CY_xmh8.png&hash=7dc5d782b8467bd4d5f79cb79ff10498)



Title: Re: Latest PIOMAS update (September)
Post by: slow wing on October 07, 2014, 05:12:29 AM
So, eye-balling, it looks like just a jot under 7000 km^3 at minimum?
Title: Re: Latest PIOMAS update (September)
Post by: viddaloo on October 07, 2014, 01:25:11 PM
Hard to tell. Latest PIOMAS daily download still terminates on August 31st.
Title: Re: Latest PIOMAS update (September)
Post by: slow wing on October 07, 2014, 01:54:55 PM
So that isn't September's data in the plot just above posted by diablobanquisa?
Title: Re: Latest PIOMAS update (September)
Post by: viddaloo on October 07, 2014, 02:29:56 PM
Yes, it is. But as I just said, they haven't released daily numbers post-August yet.
Title: Re: Latest PIOMAS update (September)
Post by: ChrisReynolds on October 07, 2014, 06:45:43 PM
Gridded updated. Crunching numbers while I eat dinner.  8)
Title: Re: Latest PIOMAS update (September)
Post by: ChrisReynolds on October 07, 2014, 09:19:28 PM
Too tired to blog tonight, but here's PIOMAS volume for September for the regions of the Central Arctic.

The regional PIOMAS numbers have been updated, apart from the daily volume (HiDay has not been updated since August).
http://dosbat.blogspot.co.uk/2013/12/regional-piomas-volume-data.html (http://dosbat.blogspot.co.uk/2013/12/regional-piomas-volume-data.html)



Title: Re: Latest PIOMAS update (September)
Post by: viddaloo on October 07, 2014, 10:13:27 PM
I'll think of something. Adding up the regions, for instance. Then we can have volume data even for September 2014, despite the #%^* incidence.
Title: Re: Latest PIOMAS update (September)
Post by: slow wing on October 07, 2014, 11:15:26 PM
Cheers for all your work, Chris. Much appreciated...  :)
Title: Re: Latest PIOMAS update (September)
Post by: ChrisReynolds on October 08, 2014, 07:40:15 AM
I'll think of something. Adding up the regions, for instance. Then we can have volume data even for September 2014, despite the #%^* incidence.

By gridded monthly data - haven't checked this morning if the main series is updated, just turned on my laptop to put more tunes on my MP3 player.

Total Volume.
6972.35 km^3

Central Arctic Volume.
6330.35 km^3

Slow Wing, Thanks, I'm glad it's of use to you.
Title: Re: Latest PIOMAS update (September)
Post by: viddaloo on October 08, 2014, 11:45:11 AM
I'll say thanks, too, Chris.

Checked PIOMAS volume again several times the last hour. Still very secretive about this year's September :(
Title: Re: Latest PIOMAS update (September)
Post by: viddaloo on October 08, 2014, 01:01:10 PM
1400 CET: Last daily volume is for August 31st.
Title: Re: Latest PIOMAS update (September)
Post by: iceman on October 08, 2014, 02:55:52 PM
Cheers for all your work, Chris. Much appreciated...  :)
Likewise... looking forward to your post on Dosbat.
Title: Re: Latest PIOMAS update (October)
Post by: Wipneus on October 08, 2014, 06:18:10 PM
I asked Dr Schweiger who fixed the issue immediately.

So data is updated, the usual monthly graphs are in the top post (https://forum.arctic-sea-ice.net/index.php/topic,119.0.html).

I will post the graphs based on September minimum later, the curve fitting algorithms are experiencing difficulties  :-(

Gridded data updated also, I will post those graphs first.
Title: Re: Latest PIOMAS update (October)
Post by: viddaloo on October 08, 2014, 06:43:32 PM
September 2014 daily sea ice volume:

2014 244   7.187
2014 245   7.164
2014 246   7.131
2014 247   7.110
2014 248   7.084
2014 249   7.067
2014 250   7.044
2014 251   7.009
2014 252   6.985
2014 253   6.963
2014 254   6.932
2014 255   6.902
2014 256   6.869
2014 257   6.834
2014 258   6.840
2014 259   6.834
2014 260   6.821
2014 261   6.810
2014 262   6.818
2014 263   6.839
2014 264   6.870
2014 265   6.892
2014 266   6.900
2014 267   6.937
2014 268   6.980
2014 269   7.015
2014 270   7.056
2014 271   7.077
2014 272   7.099
2014 273   7.119

PS: Note that for the first time since 2009 there is a net volume loss in September.
Title: Re: Latest PIOMAS update (October)
Post by: Wipneus on October 08, 2014, 06:50:26 PM
Here are the September 2013 /2014 thickness maps, as well as the differences.

EDIT: the difference graphics showed the wrong month.

Title: Re: Latest PIOMAS update (October)
Post by: Wipneus on October 08, 2014, 06:53:57 PM
And here is the August-to-September thickness change difference (2013/2014). Red means more thickening or less thinning than last year (which gives some headaches in areas that are open water in one year and ice covered in the other).
Title: Re: Latest PIOMAS update (October)
Post by: Wipneus on October 08, 2014, 07:16:23 PM
Here are the different regressions of the PIOMAS September minimums.

None of the curves, except "linear", looks very convincing now. For now I just like to see how it plays out.
Title: Re: Latest PIOMAS update (October)
Post by: viddaloo on October 08, 2014, 07:25:22 PM
Great graphs, Wipneus!

I think there's no doubt 2015 will be considerably lower in September than 2014, so don't go all linear just yet :)
Title: Re: Latest PIOMAS update (October)
Post by: ChrisReynolds on October 08, 2014, 10:30:34 PM
September PIOMAS blog post up now.
http://dosbat.blogspot.co.uk/2014/10/piomas-september-2014-massive-volume.html (http://dosbat.blogspot.co.uk/2014/10/piomas-september-2014-massive-volume.html)
Title: Re: Latest PIOMAS update (October)
Post by: Neven on October 09, 2014, 12:50:06 AM
I have also published the latest PIOMAS update (http://neven1.typepad.com/blog/2014/10/piomas-october-2014.html) on the ASIB.
Title: Re: Latest PIOMAS update (October)
Post by: Pmt111500 on October 09, 2014, 06:40:27 AM
looks like a large part of transport out of the Arctic via East Greenland Current, and the late breakup of the Nares block helped the ice to grow wrt the recent years. Could this be a (temporary) new normal that the Arctic circulation is changed so it won't throw up ice so easily anymore? Not that it much matters as we get nearer 2050s (guessing this is where the extinction of sea ice is currently located by them linear models.).  Can't believe this 2-year-trend (oxymoron) continues for much longer.
Title: Re: Latest PIOMAS update (October)
Post by: iceman on October 09, 2014, 01:17:33 PM
Here are the different regressions of the PIOMAS September minimums.

None of the curves, except "linear", looks very convincing now. For now I just like to see how it plays out.

I expect the Gompertz fit will eventually assert itself, though with such large variations it might be the end of the decade before we can say so with much confidence.
Title: Re: Latest PIOMAS update (October)
Post by: crandles on October 09, 2014, 01:41:34 PM
None of the curves, except "linear", looks very convincing now. For now I just like to see how it plays out.

Hmm, maybe. For linear, the residuals still seem a bit patchy. If it is linear then there would have to be considerable autocorrelation. If so perhaps we should now expect several years above the linear trend before a crash when it changes again to going below linear trend? Ice ages have come down, so can there be such long memory in the system? Not sure this seems physically based.

The residuals are reduced with some curve built in, but no longer by a convincing amounts. The last two years is quite eye catching, but is this likely to just be noise?

I don't think the curve fitting is very convincing and in the absence of anything else then linear might be the most sensible expectation. However we have models! All models either show a gompertz like shape or at least have a hint of such a shape.

So I don't see any reason to expect any shape other than a gompertz like shape.

For people who expected a rapid crash, this looks like yet another win for the models to me. I was certainly concerned there wasn't much time for a slow down in rate of ice loss to appear. It seems I needn't have been so concerned as there now seems plenty of time for a slow approach towards no Arctic sea ice.

Iceman posted while I was typing the same thing (probably excessively long winded).
Title: Re: Latest PIOMAS update (October)
Post by: viddaloo on October 09, 2014, 02:08:06 PM
IMO there's simply no reason for there to be a gompertz like shape. Remember we're talking about the heat potential of the Arctic seas here, and not some population or resource being depleted. I think way too much meaning is read into these two above trend years. Any trendline will have up years and down years. And the melt doesn't stop at 100%, as I've pointed out, it continues through August, October, July etc, after September finally melts out.
Title: Re: Latest PIOMAS update (October)
Post by: jdallen on October 09, 2014, 07:14:12 PM
Not sure about a gompertz-like shape to the curve.

Viddaloo, Not sure your rather disturbing curve is correct either.

Not sure the ice behavior is the correct mechanism to use for predicting the future.

I Do think the outcome will be dictated by two things - system enthalpy and net heat transfer.

Our inflection point is the freezing point of sea water.  I say inflection point because it determines a binary state; whether ice exists, or it does not.

Ice coverage will be predictable to the degree we can track heat, and determine how much sea surface will remain at a temperature which exceeds that inflection point. To my mind there now follows three questions.

1) What reservoir of oceanic heat is required to maintain a minimum SST at freezing?

2) What level of heat transfer is necessary to reach it?

3) If the current rate of heat transfer is increasing oceanic enthalpy, how soon will we reach the level indicated by question (1) above?

Sort those, and we will likely have a rather precise answer to our question.
Title: Re: Latest PIOMAS update (October)
Post by: viddaloo on October 09, 2014, 08:11:10 PM
Enthalpy (http://wikipedia.org/wiki/Enthalpy) was just awarded the Word of the Day prize. And yeah, there doesn't seem to be any mechanism that would ensure a slowdown towards the end of the era of September sea ice. But maybe some Gompertz will kick in on the way to melting out March and April? Some of us may actually live to see that happening, even though net, electricity etc will be long gone.
Title: Re: Latest PIOMAS update (October)
Post by: wili on October 09, 2014, 08:13:05 PM
But in spite of all those factors, won't there be some ice on the Arctic Ocean for a long, long time, since the Canadian Archipelago and GIS will be calving into it, probably at increasing rates?

So I would think the something like gompertz is exactly what we would expect--a very long tail, even if that represents something different that what we traditionally think of as Arctic sea ice.
Title: Re: Latest PIOMAS update (October)
Post by: jdallen on October 09, 2014, 08:19:08 PM
But in spite of all those factors, won't there be some ice on the Arctic Ocean for a long, long time, since the Canadian Archipelago and GIS will be calving into it, probably at increasing rates?

So I would think the something like gompertz is exactly what we would expect--a very long tail, even if that represents something different that what we traditionally think of as Arctic sea ice.

Absolutely.  The dynamics of the system won't distribute heat evenly. The coverage will oscillate wildly until high enough enthalpy is reached.
Title: Re: Latest PIOMAS update (October)
Post by: ChrisReynolds on October 09, 2014, 08:25:52 PM
...And yeah, there doesn't seem to be any mechanism that would ensure a slowdown towards the end of the era of September sea ice.

Yes there is; the thickness/growth feedback.
Title: Re: Latest PIOMAS update (October)
Post by: viddaloo on October 09, 2014, 08:38:30 PM
But in spite of all those factors, won't there be some ice on the Arctic Ocean for a long, long time, since the Canadian Archipelago and GIS will be calving into it, probably at increasing rates?

I'm no expert on Greenland ice, but won't these glacier withdraw inland and then only contribute meltwater in the foreseeable future? The trend, anyway, seems to be towards withdrawal.
Title: Re: Latest PIOMAS update (October)
Post by: jdallen on October 09, 2014, 09:13:29 PM
But in spite of all those factors, won't there be some ice on the Arctic Ocean for a long, long time, since the Canadian Archipelago and GIS will be calving into it, probably at increasing rates?

I'm no expert on Greenland ice, but won't these glacier withdraw inland and then only contribute meltwater in the foreseeable future? The trend, anyway, seems to be towards withdrawal.
The powerful feedback for Greenland is the consistent heat loss - it will likely be the strongest cold center in the northern hemisphere for quite a while.  In fact, it could start picking up more snow, which would be a somewhat positive feedback. I don't see calving slowing down until the sheet turns stagnant from reduced snowfall, and the existing flow pressure drops off.
Title: Re: Latest PIOMAS update (October)
Post by: crandles on October 09, 2014, 09:22:13 PM
IMO there's simply no reason for there to be a gompertz like shape. Remember we're talking about the heat potential of the Arctic seas here, and not some population or resource being depleted.

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fneven1.typepad.com%2F.a%2F6a0133f03a1e37970b017744cf5360970d-pi&hash=2582a580076f04282dbfc0fffa5e2276)
How many models have to produce a gompertz like shape before you will admit that maybe there is reason for a gompertz like shape?
Title: Re: Latest PIOMAS update (October)
Post by: viddaloo on October 09, 2014, 09:38:22 PM
If you're asking me to trust silly IPCC models that laughably predict ice-free September for the first time in 2100, the answer is Never. I just won't ever do that. It is stupid and silly.
Title: Re: Latest PIOMAS update (October)
Post by: Steven on October 09, 2014, 09:45:12 PM
Here are the September 2013 /2014 thickness maps, as well as the differences.

Thanks for these maps.  The third map in your post (Reply #349) seems to be for the wrong month: it shows the thickness difference for August rather than September?
Title: Re: Latest PIOMAS update (October)
Post by: crandles on October 09, 2014, 10:05:41 PM
If you're asking me to trust silly IPCC models that laughably predict ice-free September for the first time in 2100, the answer is Never. I just won't ever do that. It is stupid and silly.

They are the models that we have got. While we can all wish that they were better, it is what we have got. They are a lot better physically based than simple silly curve fitting exercises.

All models are wrong but some are useful. Even if these models are not very useful for predicting the date of ice free conditions, if they all predict a gompertz like shape then it is highly likely there are physical reasons for expecting gompertz like shape.

If you want to be seen to be being silly by ignoring the best information we have, then so be it.
Title: Re: Latest PIOMAS update (October)
Post by: viddaloo on October 09, 2014, 10:23:56 PM
Out in IPCC land there is still a 'pause', and no less than 10 all-time low September minimum volume records have happened during this 'pause'. I'm not a climate change denialist, so obviously I don't trust the IPCC or any other bought and sold government agency.
Title: Re: Latest PIOMAS update (October)
Post by: ChrisReynolds on October 10, 2014, 06:09:57 AM
Out in IPCC land there is still a 'pause', and no less than 10 all-time low September minimum volume records have happened during this 'pause'. I'm not a climate change denialist, so obviously I don't trust the IPCC or any other bought and sold government agency.

Sounds to me like you're anti-science. These are not 'IPCC models' they are the best mathematical implmentation of the understanding of the scientific community.

When run as a projection into the future PIOMAS shows a long tail (from Zhang et al 2010 "Arctic sea ice response to atmospheric forcings with varying levels of anthropogenic warming and climate variability"). The dashed lines are September volume, the full lines are annual average volume, four IPCC SRES scenarios shown.
(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Ffarm8.staticflickr.com%2F7085%2F7035601799_6e77dc0d70_o.jpg&hash=a8fe9a4032b36acc2aeef95f05b0ceae)

So to be consistent you really need to drop use of all PIOMAS data.
Title: Re: Latest PIOMAS update (October)
Post by: jdallen on October 10, 2014, 06:49:50 AM
IPCC is wisely conservative in their estimations of the rate of change. They cannot speculate on feed backs which have as yet not been fully plumbed, or extrapolate from sudden variations which could just be noise in the signal.

On fact I had overlooked earlier; there is a diminishing return one the forcing applied by continuing increases in CO2.  We still have a ways to go, but at some level - 500PPM? 750PPM? - the effect of it on radiative forcing itself begins to tail off into a much shallower curve.

I will go back to my enthalpy comment.  That heat reservoir works two ways, even without ice.  The ocean still has huge capacity for heat uptake, and that will buffer melt for quite a while to come.
Title: Re: Latest PIOMAS update (October)
Post by: ChrisReynolds on October 10, 2014, 07:26:02 AM
JD Allen,

I might have said this before: Using BP Statistical Review of Energy 2014 data, I have taken proven fossil fuel reserves. There is enough to drive atmos CO2 above 1000ppm, that's roughly two doublings of CO2 which implies around 6degC of global warming at equilibrium. However that does not include other GHGs and other feedbacks, most of which look likely to be positive.

The significance being that when the Arctic was last ice free all year round, CO2 levels were of the order of 1000ppm (with large uncertainty around that figure).
Title: Re: Latest PIOMAS update (October)
Post by: Wipneus on October 10, 2014, 07:39:46 AM
a gompertz like shape?

I think you should better define what exactly you think is a "gompertz like shape".
To me a gompertz like shape, is one where the tailing of lasts indefinitely, the lasts bits of ice get progressively harder to melt until the point that the last square kilometer of ices takes a zillion of years before (not) melting completely. That is not what (at least I) expect and therefore I think a "gompertz like shape" is not helping much to describe what be are observing.
(a somewhat extreme example, I hope you can see the point)

Just having a tail is not at odds with sudden and progressive melting:

- remember the model I made with each PIOMAS grid cell fitted to an exponential decline? The resulting volume/area/extent graphs got a tail, but zeroed when the last grid cell reached zero. Not gompertz like.;
- model each month volume to an exponential decline and calculate average annual volume. Yet the result gets a tail but will reach zero when the last month reaches zero. Not "gompertz like".
- model anything to a exponential decline, but add some stochastic noise with a limited amplitude to the result. The results will get a tail and will reach  zero when the noise is not big enough;
- Plot the ensemble of some "IPCC model" runs that individually more or less suddenly melt out. The ensemble will get a tail but will reach zero when the last run reaches zero. Not "gompertz like".

So yes, I think the reality will have some tail. And no, I have trouble with calling it "gompertz like", and doubt if fitting with such function will give much insight in predicting the length of the "tail".

Title: Re: Latest PIOMAS update (October)
Post by: viddaloo on October 10, 2014, 07:47:57 AM
I'm against "science" that is clearly compromized by criminal corporate elites and polluticians. If that makes me "anti-science", so be it! We need to know what happens in the real world.
Title: Re: Latest PIOMAS update (October)
Post by: Wipneus on October 10, 2014, 08:31:59 AM
None of the curves, except "linear", looks very convincing now. For now I just like to see how it plays out.
(...)
I don't think the curve fitting is very convincing and in the absence of anything else then linear might be the most sensible expectation.
(...)

Yes, that is exactly what I meant.
Title: Re: Latest PIOMAS update (October)
Post by: viddaloo on October 10, 2014, 09:29:14 AM
That's giving far too much weight to two slow years IMO. The September trend is NOT linear :)
Title: Re: Latest PIOMAS update (October)
Post by: crandles on October 10, 2014, 12:26:42 PM

I think you should better define what exactly you think is a "gompertz like shape".
To me a gompertz like shape, is one where the tailing of lasts indefinitely, the lasts bits of ice get progressively harder to melt until the point that the last square kilometer of ices takes a zillion of years before (not) melting completely. That is not what (at least I) expect and therefore I think a "gompertz like shape" is not helping much to describe what be are observing.
(a somewhat extreme example, I hope you can see the point)

Yes that probably isn't clear. There are several shapes that I would consider to be gompertz like. The main feature being a back to front s pulled out so there is only one y value for each x value.

1. There is the infinite tail you mention.
2. There is a 4 parameter gompertz which just moves the curve down (or up). This could crash to zero before starting the slow down in rate or it might not reach zero until some time after the inflection.
3. Instead of tending to a horizontal level, it might tend to a shallow slope. So instead of adding a constant as in 2 above, a constant*x is added.
4. There may be other reverse s like shapes that are not strictly gompertz shapes.
Perhaps there are others that I haven't yet mentioned.

.

I like the idea of 3 above for maximum winter volume. The rapid slope being where thick MYI is being reduced towards 2m thick. Once that has happened there is still the effect of GHGs, ocean upward heat flux ... reducing the thickness of FYI.

Other things being equal, the lower the maximum volume, the higher the melt volume (until it all melts).

If the melt volume was particularly sensitive to a certain range of maximum volume, then the minimum curve could have two periods of rapid decline. I doubt this as we don't see it in the models. However another possibility is that this results in a trend (after the slowdown in rate) that slowly increases the downward trend tending towards some limit.

I think this possibility is sufficiently far from a gompertz shape that I wouldn't call it a gompertz like shape.
Title: Re: Latest PIOMAS update (October)
Post by: Wipneus on October 10, 2014, 04:04:53 PM
Here are the September 2013 /2014 thickness maps, as well as the differences.

Thanks for these maps.  The third map in your post (Reply #349) seems to be for the wrong month: it shows the thickness difference for August rather than September?

You are completely right, I have corrected it now.

Thank you for spotting this.
Title: Re: Latest PIOMAS update (October)
Post by: Phil. on October 10, 2014, 11:29:42 PM
IPCC is wisely conservative in their estimations of the rate of change. They cannot speculate on feed backs which have as yet not been fully plumbed, or extrapolate from sudden variations which could just be noise in the signal.

On fact I had overlooked earlier; there is a diminishing return one the forcing applied by continuing increases in CO2.  We still have a ways to go, but at some level - 500PPM? 750PPM? - the effect of it on radiative forcing itself begins to tail off into a much shallower curve.

I will go back to my enthalpy comment.  That heat reservoir works two ways, even without ice.  The ocean still has huge capacity for heat uptake, and that will buffer melt for quite a while to come.

Actually there is the expectation that at some point the CO2 forcing will transition to a square root dependence and therefore increase.  see Curve of growth.
Title: Re: Latest PIOMAS update (October)
Post by: Peter Ellis on October 11, 2014, 12:42:21 AM
When run as a projection into the future PIOMAS shows a long tail (from Zhang et al 2010 "Arctic sea ice response to atmospheric forcings with varying levels of anthropogenic warming and climate variability"). The dashed lines are September volume, the full lines are annual average volume, four IPCC SRES scenarios shown.
(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Ffarm8.staticflickr.com%2F7085%2F7035601799_6e77dc0d70_o.jpg&hash=a8fe9a4032b36acc2aeef95f05b0ceae)

So to be consistent you really need to drop use of all PIOMAS data.
I agree that viddaloo is one of the several anti-science folks we have here (guess it's an occupational hazard).  However in fairness I should point out that if I recall that paper correctly, only the red and black lines on that graph are remotely plausible, and both show a September collapse to very low levels by about 2025. 

The green and blue lines were forced based on the assumption that _all_ variability in the historical record is random noise - i.e. that there is no genuine trend towards sea ice loss, that AGW isn't happening, and that global temperatures / Arctic weather will consequently return to the "historical average" (i.e. the average of all the figures from 1978 to the present day, roughly a return to mid 90's conditions).  You can see the effect of this as the sea ice volumes immediately take an unphysical jump upward to ~1995 levels as soon as the forecast is initialised.

To forestall viddaloo's inevitable comment about corruption, fake science etc., this is because those two lines are in effect acting as a negative control - an essential part of any good science.  This negative control has obviously already been falsified by the data from the last couple of years (even including the recent mini-recovery)
Title: Re: Latest PIOMAS update (October)
Post by: Peter Ellis on October 11, 2014, 01:00:05 AM
Forgot the conclusion:

So no, I don't think PIOMAS predicts a long tail.  When you use realistic forcings that actually accept the existence of AGW, it predicts a more or less linear drop to a September volume of ~1-2 x 10^12 m^3 by 2025.  This is less than 1/3 of the 2012 record, and would presumably therefore correspond to a similar fraction of the 2012 minimum extent - which puts it around the 1 million km^2 threshold for "ice free".

It does then seem to bounce along at around that minimum for a very long time though without dropping to a "true" zero. That's not to say PIOMAS is right!

I'm intrigued by the way the Tietsche et al models show two "plateau phases" in the drop - one at around 4.5 million km^2 September minimum and another at around 2 million km^2.  The reason I find this quite plausible is that it roughly corresponds to the bathymetric features of the Arctic ocean basin.  4.5 million km^2 just about covers the "deep bits" of the Arctic Ocean, with the surrounding shallower seas melting out (which is close to the status quo since 2007), while 2km^2 represents the last bastion in the Lincoln sea and north of Greenland/CA.

I do very much like the implication that there will be several successive "regimes" on the way down, since the heat transfer processes operating in different regions of the Arctic basin will be quite different and thus different parts of the basin will be inherently more or less resilient to AGW.
Title: Re: Latest PIOMAS update (October)
Post by: viddaloo on October 11, 2014, 01:00:54 AM
Enough! with the name–calling, OK? How on Earth can my view that science should be fact–based and pure and free of the compromizing and lobbying efforts of vested interests, be remotely anti–science? You're just calling me anti–science because I love science, which is really childish and ignorant.

To give you an analogy to make you see my valid point, what you're thoughtlessly saying is like telling a guy who loves football but can't stand all the advertisments and talk about buying and selling of players, that he is anti–football. When all he wants is for sports to be about sports.

Stop being stupid and making ad hominem attacks. Thanks.
Title: Re: Latest PIOMAS update (October)
Post by: jai mitchell on October 11, 2014, 06:02:46 AM
Out in IPCC land there is still a 'pause', and no less than 10 all-time low September minimum volume records have happened during this 'pause'. I'm not a climate change denialist, so obviously I don't trust the IPCC or any other bought and sold government agency.

Sounds to me like you're anti-science. These are not 'IPCC models' they are the best mathematical implmentation of the understanding of the scientific community.

When run as a projection into the future PIOMAS shows a long tail (from Zhang et al 2010 "Arctic sea ice response to atmospheric forcings with varying levels of anthropogenic warming and climate variability"). The dashed lines are September volume, the full lines are annual average volume, four IPCC SRES scenarios shown.
(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Ffarm8.staticflickr.com%2F7085%2F7035601799_6e77dc0d70_o.jpg&hash=a8fe9a4032b36acc2aeef95f05b0ceae)

So to be consistent you really need to drop use of all PIOMAS data.

Let's dispense from the ad hominem attacks.  While we can be proud of the collective body of work, I think that we should all remember that the inherent negative feedbacks in the world of policy cause the IPCC to be greatly, fantastically, even -dare I say it- GENOCIDALLY conservative in their estimations.

The known biases are
1.  Established to show science and refrain from policy implications/interpretations
2. Relying on full consensus for findings (leads to Type I Avoidance Bias)
3.  Dominant Type I error avoidance bias (more fearful of losing credibility in the now than being wrong in the future)
4.  Allowing government agents to lobby for corrections to the final draft and synthesis report
5.  A simple temporal lag in the development process, the AR5 is 5 years too late.

If I may interject.  The above graph, as shocking and terrible as it may seem, does not include the following:

1.  Increasing and significant albedo changes due to increasing spring snow cover anomalies and late melt season open oceans. (chart above shows AR4 inputs)
2.  Carbon cycle and permafrost emission feedbacks becoming severe around the mid 2020's
3.  The new work by Paul Durack at LLL showing that the Top of Atmosphere energy imbalance is growing at a much faster rate than we have previously modeled, (even beyond the projected measurement error).

These are fatal flaws and can only be attributed to a kind of collective "capture" of the scientific work.  As though it was doomed to fail from the onset.
Title: Re: Latest PIOMAS update (October)
Post by: ChrisReynolds on October 11, 2014, 09:05:16 AM
Peter,

Thanks for pointing that out.

A1 (A2) uses an increase of regional average temperature of 4degC (2degC) by 2050 onto which is superimposed variability taken from NCEP/NCAR forcings for 1948 to 2009.

B1 (B2) uses an increase of regional average temperature of 2degC (2degC) by 2050 onto which is superimposed variability taken from NCEP/NCAR forcings for 1948 to 2009.

So A2 and B2 are the scenarios to consider, I should have pointed that out.

However I still see a tail, by 'long tail, I do not think 2050s, rather into the 2030s. Those claiming a fast crash seem to be claiming one this decade, PIOMAS in the Zhang et al 2010 paper shows a continuation until the mid 2020s, with a tail of remnant summer volume thereafter. This tail of remnant summer volume is due to the long term survival of winter sea ice volume, this survival of winter ice volume means a crash to zero ice will not happen. Zhang et al note that: "Because of enhanced winter ice growth, arctic winter ice extent remains nearly stable and therefore appears to be a less sensitive climate indicator."

This survival of winter ice volume also means that there will be no rapid ransition to a sea ice free state. Years with weather like 2013 and 2014 will pull volume (thickness) up and lead to large variations in summer extent for some time, I suspect into the 2030s. Arctic warming seems to be happening faster than the scenarios in Zhang et al 2010, this will bring winter volume down faster than in the graphic I posted.

The survival of winter ice is significant because Viddaloo has also posted a graph up thread.
http://forum.arctic-sea-ice.net/index.php/topic,119.msg37908.html#msg37908 (http://forum.arctic-sea-ice.net/index.php/topic,119.msg37908.html#msg37908)

This shows no ice by the 2050s year round, and over 6 months ice free by the 2030s. That stands against the findings of Zhang et al 2010.
Title: Re: Latest PIOMAS update (October)
Post by: ChrisReynolds on October 11, 2014, 09:31:00 AM
Viddaloo, Jai Mitchell,

An ad-hom is an attack is "An attack upon an opponent in order to discredit their arguement or opinion." That is not what is happening here. The anti-science element on this forum are something I see (and it seems Peter does too). That is seperate from the issue of whether arguments are flawed. I have alledged an anti science bias, then gone on to address the argument.

Jai,

Your final three points.

1) That doesn't affect winter ice growth which is the key issue in maintaining winter volume.
2) That seems rather early and precise for such an issue, I'm not convinced.
3) Got a cite for that paper?

In any case: Armour et al, 2011, "The reversibility of sea ice loss in a state-of-the-art climate
model" Figure 2c shows NH sea ice extent in March as a function of NH annual mean average temperature anomaly. Between 4 degC and 6 degC the selected GCMS show a crash of March extent to extremely low levels that would imply many months of the year being totally ice free in summer.

Even allowing for bias in the models, and further warming factors, we are some way from a NH annual mean average temperature anomaly of 4 to 6 degC.

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fdata.giss.nasa.gov%2Fgistemp%2Fgraphs_v3%2FFig.B.gif&hash=48246527a6b597d0333e772939fdcb0f)

EDIT - forgot to add: Show me one example where political interests have been involved in the design or running of a climate model.

Viddaloo,

IMO there's simply no reason for there to be a gompertz like shape. Remember we're talking about the heat potential of the Arctic seas here, and not some population or resource being depleted. I think way too much meaning is read into these two above trend years. Any trendline will have up years and down years. And the melt doesn't stop at 100%, as I've pointed out, it continues through August, October, July etc, after September finally melts out.

Can you direct me to where you explained that graph. When I first saw it I thought "I must look at that, I don't believe it", but was too busy, then forgot.
Title: Re: Latest PIOMAS update (October)
Post by: viddaloo on October 11, 2014, 10:55:51 AM
I've shown (previously) how Winter refreeze mirrors Summer melt, but less so the other way around: Maximum Winter ice is less indicative of what the Summer melt will achieve. I've also asked all of you what the (physical mechanism or) reason would be for the expectation of a Gompertz like shape to the graphs that go into the future.

So far the only such suggested reason I've seen here is Winter refreeze. Is that correct? If so, I think your argument is wrong. The next 2007 or 2010 or 2011 or 2012 will go dramatically low because of extreme melting, not because of a low starting point. At least, that is what the data tells me. (Of course, a low starting point helps, but the force of the melting season is more important IMO.)
Title: Re: Latest PIOMAS update (October)
Post by: jdallen on October 11, 2014, 11:07:42 AM
Not a specific paper, but perhaps the start of the thread:

http://www.commondreams.org/news/2014/10/06/rate-ocean-warming-vastly-underestimated-study (http://www.commondreams.org/news/2014/10/06/rate-ocean-warming-vastly-underestimated-study)

Edit: SciAm article, with a touch more detail.

http://www.scientificamerican.com/article/mystery-of-ocean-heat-deepens-as-climate-changes/ (http://www.scientificamerican.com/article/mystery-of-ocean-heat-deepens-as-climate-changes/)
Title: Re: Latest PIOMAS update (October)
Post by: viddaloo on October 11, 2014, 12:23:17 PM
These are fatal flaws and can only be attributed to a kind of collective "capture" of the scientific work.  As though it was doomed to fail from the onset.
It is very much a design for scientific and political failure, whether or not the choice of that specific design was intentional or not.
Title: Re: Latest PIOMAS update (October)
Post by: crandles on October 11, 2014, 12:57:23 PM
I've shown (previously) how Winter refreeze mirrors Summer melt, but less so the other way around: Maximum Winter ice is less indicative of what the Summer melt will achieve. I've also asked all of you what the (physical mechanism or) reason would be for the expectation of a Gompertz like shape to the graphs that go into the future.

So far the only such suggested reason I've seen here is Winter refreeze. Is that correct? If so, I think your argument is wrong. The next 2007 or 2010 or 2011 or 2012 will go dramatically low because of extreme melting, not because of a low starting point. At least, that is what the data tells me. (Of course, a low starting point helps, but the force of the melting season is more important IMO.)

>So far the only such suggested reason I've seen here is Winter refreeze. Is that correct?
Yes

>The next 2007 or 2010 or 2011 or 2012 will go dramatically low because of extreme melting, not because of a low starting point.

That is right too, because the maximum volumes are not getting much lower any more.

What you seem to me to be missing is that the main reason for increasing summer melt is that the declining maximum volume is allowing lower albedo through more open water formation and thinner ice. Take away the declining maximum volume and there isn't much reason left for increasing summer melt.
Title: Re: Latest PIOMAS update (October)
Post by: viddaloo on October 11, 2014, 01:05:34 PM
Then you forget the tiny detail element of global warming, of course. Easy to forget in this context.
Title: Re: Latest PIOMAS update (October)
Post by: crandles on October 11, 2014, 01:12:00 PM
Albedo effects are huge. GW not so much.

Like I said, there isn't much reason left for increasing summer melt.
Title: Re: Latest PIOMAS update (October)
Post by: viddaloo on October 11, 2014, 01:26:47 PM
Albedo effects are huge. GW not so much.

Like I said, there isn't much reason left for increasing summer melt.
All right. So let me get this straight: You're saying, on a Saturday in October 2014, that increased radiative forcing, increased ocean enthalpy, increased release of permafrost methane etc etc, somehow will not melt any more sea ice than in 2010-2012?

Sir, I think we'll just have to agree to disagree on that one. I don't see no room for educated discussion here.
Title: Re: Latest PIOMAS update (October)
Post by: jai mitchell on October 11, 2014, 07:09:50 PM

Your final three points.

1) That doesn't affect winter ice growth which is the key issue in maintaining winter volume.
2) That seems rather early and precise for such an issue, I'm not convinced.
3) Got a cite for that paper?

--------------
Even allowing for bias in the models, and further warming factors, we are some way from a NH annual mean average temperature anomaly of 4 to 6 degC.
--------------

Re: Durack et. al we have a thread going here:  I have done comparative analysis to Nuccitelli et. al 2013 (and Hansen & Soto 2010) and shown the comparative deviation from previous projections.

https://forum.arctic-sea-ice.net/index.php/topic,1011.0.html (https://forum.arctic-sea-ice.net/index.php/topic,1011.0.html)

Re winter ice growth:  I do not expect that tietsche et. al. accurately portrayed the atmospheric dynamics in her projections for winter ice recovery post summer ice loss.  This is especially true when one considers the enthalpy increase due to a june 1st ice free condition.  I believe that we will see a large change in Maislowski's intrusive pacific and that albedo-driven ocean enthalpy will ensure a much thinner winter ice cover.

Re: NH 4-6 C'  The Zhang 2010 paper projected ice free conditions with regional arctic ambient temperatures of 4C by 2050 not NH temperatures.

Models are run all the time with many (any!) inputs.  Where the internal bias comes in is in the design of the results, what is considered to be aligned with the consensus, what is left on the cutting room floor.

The AR5 report was only recently published.  At the Royal Society ARCTIC 14 presentation an unofficial poll was taken that asked when the arctic would be ice free.  The vast majority of the respondents stated within 10-30 years.

How do you suppose then that the AR5 still holds that there will be perennial sea ice through 2050 under a high emissions scenario?

RE: political findings, I am surprised you do not know this -

Government representatives propose authors and contributors, participate in the review process, and help reach a consensus on the report’s major findings. This can result (especially in the SPMs) in language that is sometimes weaker than it otherwise might be.

union of concerned scientists
http://www.ucsusa.org/global_warming/science_and_impacts/science/ipcc-backgrounder.html#bf-toc-9 (http://www.ucsusa.org/global_warming/science_and_impacts/science/ipcc-backgrounder.html#bf-toc-9)

Title: Re: Latest PIOMAS update (October)
Post by: ChrisReynolds on October 11, 2014, 07:15:40 PM
Albedo effects are huge. GW not so much.

Like I said, there isn't much reason left for increasing summer melt.
All right. So let me get this straight: You're saying, on a Saturday in October 2014, that increased radiative forcing, increased ocean enthalpy, increased release of permafrost methane etc etc, somehow will not melt any more sea ice than in 2010-2012?

Sir, I think we'll just have to agree to disagree on that one. I don't see no room for educated discussion here.

Don't just walk away. Provide us with the calculations that show interannual variability, intra-annual range of forcing (mainly solar) vs the annual increment of forcing due to AGW.

Once you've done that you will be able to claim you're approaching this in an educated manner.

Once you've done that you will see that the AGW forcing (EDIT - change in forcing over short periods) is dwarfed by interannual variability and intra-annual range of forcing (mainly solar).

Sheesh!
Title: Re: Latest PIOMAS update (October)
Post by: mark on October 11, 2014, 07:52:33 PM
How does a thread degenerate into this. I thought it was a very interesting interpretation of the resuts to fit a single curve to them as this does mostly fit very neatly with the recent Data. However the results over longer periods or shorter periods (it doesnt seem to matter) have a habit of going off trend - I mean any trend -linear, curved ,gompertz etc modeled or otherwise. They are all conjecture if recent data doesnt fit predicted. I say each to their own, perhaps someone will be right.

Viddaloo - there are so many different forcings and negative and positive feedbacks I dont see how you expect all the people here to see things as you do, I think its safe to say we all research and read, some are very well trained and knowledgeable others are very well read and knowledgeable. That you are passionate is undeniable and your postings are stimulating up to the point where you get upset and make a stand.

For myself I believe the ocean currents hold the key as they hold the most energy. As we currently dont record the deep and bottom water flows with enough regular accuracy it is hard to form an opinion on what effect these massive flows are having on climate variation so I dont believe the future is even slightly more predicatble than it was 18 years ago. I dipped a finger in this debate before and now have just 9 left, so I tread much more carefully with passionate opinion! But I read and then reread different papers and try to keep opinions to a minimum. Perhaps when I understand more about the whole atmospheric and oceanographic make up I will post my findings here and take on the comment hopefully without getting upset again.
Title: Re: Latest PIOMAS update (October)
Post by: ChrisReynolds on October 11, 2014, 08:19:43 PM

Your final three points.

1) That doesn't affect winter ice growth which is the key issue in maintaining winter volume.
2) That seems rather early and precise for such an issue, I'm not convinced.
3) Got a cite for that paper?

--------------
Even allowing for bias in the models, and further warming factors, we are some way from a NH annual mean average temperature anomaly of 4 to 6 degC.
--------------

Re: Durack et. al we have a thread going here:  I have done comparative analysis to Nuccitelli et. al 2013 (and Hansen & Soto 2010) and shown the comparative deviation from previous projections.

https://forum.arctic-sea-ice.net/index.php/topic,1011.0.html (https://forum.arctic-sea-ice.net/index.php/topic,1011.0.html)

The full paper is here:
http://www-pcmdi.llnl.gov/about/staff/Durack/dump/oceanwarming/140926a_Duracketal_UpperOceanWarming.pdf (http://www-pcmdi.llnl.gov/about/staff/Durack/dump/oceanwarming/140926a_Duracketal_UpperOceanWarming.pdf)
The result doesn't seem so significant as to affect the 1.5 to 4.5degC confidence interval for climate sensitivity, which is based on multiple lines of evidence.

Re winter ice growth:  I do not expect that tietsche et. al. accurately portrayed the atmospheric dynamics in her projections for winter ice recovery post summer ice loss.  This is especially true when one considers the enthalpy increase due to a june 1st ice free condition.  I believe that we will see a large change in Maislowski's intrusive pacific and that albedo-driven ocean enthalpy will ensure a much thinner winter ice cover.

Both Tietsche et al and Schroeder & Connelly used coupled atmopshere runs.
http://onlinelibrary.wiley.com/doi/10.1029/2007GL030253/abstract (http://onlinelibrary.wiley.com/doi/10.1029/2007GL030253/abstract)

Tietsche removed the ice on 1 July, near enough to the solstice to make little difference from 1 June. Schroeder & Connelly removed the ice on, 1 December, 1 March, 1 June, and 1 September, they found a very similar result.

"Sensitivity experiments with a fully coupled general
circulation model show a complete recovery from a total
removal or strong increase of sea ice after four years. These
are extreme anomalies and more realistic perturbations
would show even faster recovery. Thus, errors in initial
sea ice conditions seem to be unimportant for climate
modelling on decadal or longer timescales....

...The impact is stronger when ocean temperature is
adjusted to ice-free conditions, but even then the differences
appearing between the sensitivity and Ctrl runs are clearly
smaller after a few years than the differences between
modelled and observed sea ice area."

Note that different models were used in each study: Tietsche et al used ECHAM5/MPI-OM, Schroeder & Connelly used HADCM3.

Re: NH 4-6 C'  The Zhang 2010 paper projected ice free conditions with regional arctic ambient temperatures of 4C by 2050 not NH temperatures.

Sorry I don't get your point here. Armour et al examine GCMs and find 4 to 6degC NH avg temperature increase is the period where the models considered show a crash of winter cover.

Models are run all the time with many (any!) inputs.  Where the internal bias comes in is in the design of the results, what is considered to be aligned with the consensus, what is left on the cutting room floor.

The results are emergent phenomena from the mathematical model. Leaving out results because the scientist doesn't like them would be considered highly unethical. Is that really what you think of the scientists?

The AR5 report was only recently published.  At the Royal Society ARCTIC 14 presentation an unofficial poll was taken that asked when the arctic would be ice free.  The vast majority of the respondents stated within 10-30 years.

Overland & Wang, 2013, "A sea ice free summer Arctic within 30 years: An update
from CMIP5 models"

"Three years ago we proposed that the summer Arctic
would be nearly sea ice free by the 2030s; “nearly” is
interpreted as sea ice extent less than 1.0 million km2. We
consider this estimate to be still valid based on projections of
updated climate models (CMIP5) and observational data...

...Applying the same technique of
model selection and extrapolation approach to CMIP5 as we
used in our previous paper, the interval range for a nearly sea
ice free Arctic is 14 to 36 years, with a median value of
28 years. Relative to a 2007 baseline, this suggests a nearly
sea ice free Arctic in the 2030s."

When one uses models selected because they reproduce the seasonal cycle well the models say within 30 years.

How do you suppose then that the AR5 still holds that there will be perennial sea ice through 2050 under a high emissions scenario?

What does AR5 actually say?

Page 995 of this doc:
http://www.climatechange2013.org/images/report/WG1AR5_Chapter11_FINAL.pdf (http://www.climatechange2013.org/images/report/WG1AR5_Chapter11_FINAL.pdf)

The IPCC clearly do not hold that there will be perennial ice. WG1 concludes that it is "likely that the Arctic Ocean will become nearly ice-free in September before the middle of the century for high GHG emissions such as those corresponding to RCP8.5 (medium confidence)."

They note Maslowski's aggressive 2016 prediction. But note that "such an approach not only neglects the effect of year-to-year or longer-term variability (Overland and Wang, 2013) but also ignores the negative feedbacks that can occur when the sea ice cover becomes thin (Notz, 2009)."

RE: political findings, I am surprised you do not know this -

Government representatives propose authors and contributors, participate in the review process, and help reach a consensus on the report’s major findings. This can result (especially in the SPMs) in language that is sometimes weaker than it otherwise might be.


union of concerned scientists
http://www.ucsusa.org/global_warming/science_and_impacts/science/ipcc-backgrounder.html#bf-toc-9 (http://www.ucsusa.org/global_warming/science_and_impacts/science/ipcc-backgrounder.html#bf-toc-9)


Sorry, the SPM is not the main IPCC report, it's the dumbed down version. You need to refer to IPCC AR5 WG1. I have never bothered with the SPM, politicians have a hand in it.
Title: Re: Latest PIOMAS update (October)
Post by: jai mitchell on October 11, 2014, 09:42:36 PM
The full paper is here:
http://www-pcmdi.llnl.gov/about/staff/Durack/dump/oceanwarming/140926a_Duracketal_UpperOceanWarming.pdf (http://www-pcmdi.llnl.gov/about/staff/Durack/dump/oceanwarming/140926a_Duracketal_UpperOceanWarming.pdf)
The result doesn't seem so significant as to affect the 1.5 to 4.5degC confidence interval for climate sensitivity, which is based on multiple lines of evidence.

I would expect you to take a closer look at the data and contemplate more fully its implications.  This is very shallow thinking of you.  You must consider that if the total 35 year accumulation of heat energy is (at the high end) 30% more than was previously understood, then the total forcing is much higher, the ECS is much higher and the TOA will continue to grow at a much higher rate for a given rate of emissions.

In addition, since the models appear to be correct for the ocean heat accumulation in the NORTHERN hemisphere, this also poses significant implications to the impacts of NH aerosols (being severely underestimated in Trenberths' balance calculation).

THEN you must consider the compounding feedback and tipping points that are inherently affected by the reanalysis of ECS and TOA energy imbalance growth rates.  These are all compounding effects.

The simple fact is that, this one study alone, indicates that our current radiative forcing from 402% PPMV is actually acting like 460 PPMV according to our previous models.

These are the IMPLICATIONS from the results of the paper.

Both Tietsche et al and Schroeder & Connelly used coupled atmopshere runs.
http://onlinelibrary.wiley.com/doi/10.1029/2007GL030253/abstract (http://onlinelibrary.wiley.com/doi/10.1029/2007GL030253/abstract)

Tietsche removed the ice on 1 July, near enough to the solstice to make little difference from 1 June.

Stating that a July 1 and June 1 ice free condition is quantitatively similar is simply not true:  http://www.physicalgeography.net/fundamentals/images/insolation_latitude.gif (http://www.physicalgeography.net/fundamentals/images/insolation_latitude.gif)
Schroeder & Connelly removed the ice on, 1 December, 1 March, 1 June, and 1 September, they found a very similar result.

"Sensitivity experiments with a fully coupled general
circulation model show a complete recovery from a total
removal or strong increase of sea ice after four years.

...The impact is stronger when ocean temperature is
adjusted to ice-free conditions, but even then the differences
appearing between the sensitivity and Ctrl runs are clearly
smaller after a few years than the differences between
modelled and observed sea ice area."

Note that different models were used in each study: Tietsche et al used ECHAM5/MPI-OM, Schroeder & Connelly used HADCM3.

How do you reconcile this with the ZHANG 2010 paper that states a largely summer ice free state with 4C regional (not NH) warming?

Neither of these adequately addressed the 40 meter depth warm pool effects after june 1 ice free conditions and the increase of saline atlantic water from the Alaskan Shoreline Eddy, as documented in Maislowski's recent work.   They both predicted rapid heat loss to the atmosphere but this is inconsistent with the production of surface ice with a warm pool contained below the halocline that will likely (between 2020 and 2040) be holding between 2 and 8 times the total enthalpy than current values.

You said that it would take a 4C NH warming and that is simply not true.  .5C maybe. . not 4C  I expect we will see this warming rate within the next 5 years.
 

The results are emergent phenomena from the mathematical model. Leaving out results because the scientist doesn't like them would be considered highly unethical. Is that really what you think of the scientists?


Government representatives propose authors and contributors

Sorry, the SPM is not the main IPCC report, it's the dumbed down version. You need to refer to IPCC AR5 WG1. I have never bothered with the SPM, politicians have a hand in it.
[/quote]

This is not just the synthesis report it is the lead authorship roles as well, for the working groups.  Why would we allow governments to appoint authors and select contributors???
Title: Re: Latest PIOMAS update (October)
Post by: jai mitchell on October 11, 2014, 09:55:09 PM
Finally, and much more importantly, and in hopes of returning to the topic, Wipneus's AMAZING work!

<img width="580" height="435" class="bbc_img resized" style="width: auto; height: auto; cursor: pointer;" alt="" src="https://sites.google.com/site/arctischepinguin/home/piomas/grf/piomas-trnd4.png"></img>

(https://sites.google.com/site/arctischepinguin/home/piomas/grf/piomas-trnd4.png)

I would like to see a statistical analysis of this data with a trend analysis for cumulative loss between June 1st and August 1st.  Then the deviation from the trend for 2014 can be more adequately addressed.

just by looking at the graph I am certain it surpasses the 2 sigma deviation from the trend (possibly 3!)

It would be absolutely foolhardy to imply that this extreme event can be anything indicative of a long-term trend.

however, it does indicate some kind of larger systemic shift, a "not-seen-before" event.  Either natural or unnatural it indicates a significant loss of boundary between the Ferrel and Arctic Cells  And/or some form of conscious manipulation of the atmospheric regimes.

At this point, all bets are out the window.  The world has NEVER witnessed a climatic shift to this degree at this rate.  The PETM took 10,000 years to develop, we are on track to overshoot the PETM within 300 years.
Title: Re: Latest PIOMAS update (October)
Post by: ChrisReynolds on October 12, 2014, 10:01:02 AM
Jai,

Let's just get the IPCC issue out of the way first. When I was in the process of changing my mind from being a sceptic of AGW I downloaded AR3 and selected some random chapters from the WG1 scientific basis. I then went through those chapters checking to see if the IPCC was correctly reporting the science, this took some time as I didn't know very much. I've not done the same since, but on reading the section I referred you to I have read all the references (and more) and it reads like a fair assessment of the science. I'm just an amateur but I do know sea ice science pretty well. So unless you can point out problems with that section that will educate me further, I think the IPCC is making a fair assessment there.

You said:
...this one study alone, indicates that our current radiative forcing from 402% PPMV is actually acting like 460 PPMV according to our previous models.
I said, "The result doesn't seem so significant as to affect the 1.5 to 4.5degC confidence interval for climate sensitivity, which is based on multiple lines of evidence." Note the wide range of the pre-existing (basically Charney) estimate, and the multiple lines of evidence that have gone into that. 402 to 460 rounds up to a 15% increase, 15% extra on 3degC is about 3.5degC, within the range of 1.5 to 4.5degC, assuming RF tends to linear over such a short range. My opinion remains that until I see significant research substantially revising upwards outside the Charney range. I don't think Durack et. al is strong enough to overturn that range, but it is useful.

June/July insolation: What have you got, a 100W/m^2 variation with lattitude? Or some 20%. Agreed?

How much variation in insolation do you think different pressure systems with attendant cloud variation (thick low cloud to clear sky) will cause? I said "Tietsche removed the ice on 1 July, near enough to the solstice to make little difference from 1 June." Maybe I should have said "Tietsche removed the ice on 1 July, near enough to the solstice to make little difference from 1 June, bearing in mind the influence of weather"

I went on to refer to Schroeder & Connelly: "Schroeder & Connelly removed the ice on, 1 December, 1 March, 1 June, and 1 September, they found a very similar result." They also examined a warmed ocean due to open water, the results were that:

The impact is stronger when ocean temperature is
adjusted to ice-free conditions, but even then the differences
appearing between the sensitivity and Ctrl runs are clearly
smaller after a few years than the differences between
modelled and observed sea ice area."

You say:
How do you reconcile this with the ZHANG 2010 paper that states a largely summer ice free state with 4C regional (not NH) warming?
You seen to be getting mixed up. Actually Zhang et al 2010 shows virtually ice free with 2degC warming, but this is in the summer. Armour et al find a collapse of winter ice cover with between 4 and 6degC hemispheric annual average warming.

Sea ice formation is simply not inconsistent with an ocean warmed in the summer. Once the sun sets in winter temperatures drop. Over the ice free warmed ocean temperatures are held up lower in the atmosphere above the open water. But the net heat flux is upward, and as atmospheric temperatures cool it is massive.

On the slow transition thread I have shown calculations with a simple thermodynamic model of sea ice growth. The following uses a synthesised daily 2m temperature dataset derived from NCEP/NCAR monthly data over the ESS.

(https://farm6.staticflickr.com/5558/15302194511_19b64cac76_o.png)

Heat flux is seen to be massive in the early autumn, with a delay to ice growth into mid October as the air temperatures exceed zero degC.

Consider the heat flux. The sum of heat flux for a 1m squared area from 6 October to 31 December is 4379W/m^2 over 92 days. 60x60x24x4379 = 378M joules for a 1m^2 area. 6 October being when the ice has formed.

The specific heat capacity of sea water near the surface is around 3985 J/kg K, the density is around 1027 kg/m^3, so to cool 1m cubed of sea water by 1degC (or Kelvin) you need to lose around 4M joules.

378MJ/m^3 K / 4MJ /m^3 = 94.5 metre depth cooled by 1 degC. And that is after the ice has formed, so temperature is already at -1.8degC for the surface. Before the ice forms heat loss is even greater, in winter over leads heat fluxes can exceed 400W/m^2 (Andreas 1979 via Alam & Curry). Bear in mind that the peak heat flux through ice is only 1/8 of such figures for open water in winter.
Alam & Curry.
http://curry.eas.gatech.edu/currydoc/Alam_JGR100.pdf (http://curry.eas.gatech.edu/currydoc/Alam_JGR100.pdf)

Once incoming solar radiation is gone the heat budget for the Arctic is upwards, cooling will occur. Over open water it is massive. Hence ice will form.

Using the same simple physical model it is possible to reformulate in terms of Freezing Degree Days (FDDs). Using such a formulation one can combine the impact of shortened melt season and winter warming.

(https://farm4.staticflickr.com/3863/15323264632_350e9e8873_o.png)

Currently over the East Siberian Sea FDD is around 4000, in the 1980s it was about 5000, over the Central Arctic it is higher (over 5000). Over most of the pack you'd need to more than halve FDD to around 2000 to get out of the linear range of FDD/peak thickness. If winter ice only grows to around 1.5m across the pack then by that stage thickness will be such that summer thinning will largely wipe out the ice (apart from mechanically deformed ice off Canada). We have a long way to go before that happens and winter thickness falls enough such that regular total melt outs become the norm.

Note that in PIOMAS of grid boxes with an effective thickness of around 2m in April, only around 15% to 70% meltout totally to give open water. By 1.75m, this is 40% to 85%, which corresponds to 2000 FDDs. As mentioned above, the Central Arctic is currently around 5000 FDD and the ESS has fallen from 5000 FDD in the 1980s to 4000 FDD in recent years. There remains a lot of winter warming and later start to melting before we can expect to see winter thickness drop to levels where massive (85%) area loss is to be expected.

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2F4.bp.blogspot.com%2F--3lUdsfzyWQ%2FVDWAkgA5x_I%2FAAAAAAAABC8%2FZT7yjyBLZOE%2Fs1600%2FPercent%252BOW%252BAll.png&hash=86d4c5c47dfa4107dfc70b7e9e1071d7)
Title: Re: Latest PIOMAS update (October)
Post by: jai mitchell on October 12, 2014, 06:10:32 PM
working on a response here:

https://forum.arctic-sea-ice.net/index.php/topic,1017.0.html
Title: Re: Latest PIOMAS update (October)
Post by: Phil. on October 13, 2014, 02:01:52 PM
Once incoming solar radiation is gone the heat budget for the Arctic is upwards, cooling will occur. Over open water it is massive. Hence ice will form.


Chris have you accounted for incoming LW flux, into Nov that will still be ~200W/m^2?
Title: Re: Latest PIOMAS update (October)
Post by: ChrisReynolds on October 13, 2014, 04:40:52 PM
Once incoming solar radiation is gone the heat budget for the Arctic is upwards, cooling will occur. Over open water it is massive. Hence ice will form.


Chris have you accounted for incoming LW flux, into Nov that will still be ~200W/m^2?

Downwelling longwave has typically been of such a order of magnitude in the past as the sample plots from ISCCP show on this page.
https://stratus.ssec.wisc.edu/projects/d1fluxes/d1fluxes.html (https://stratus.ssec.wisc.edu/projects/d1fluxes/d1fluxes.html)
Under such a regime ice has formed, net flux is still upwards as evidenced by Autumn/Winter atmospheric cooling. The warming signature of recent years with large open water into the autumn is marked as a low level surface hugging warming, this warming will retard ice growth, however it is a warming above climatology, not always above freezing. So the process of ocean losing heat followed by ice growth still occurs. To halve the freezing degree days down to around 2000 and severely impact April thickness requires a substantial mix of late re-freeze and substantial winter warming.

In the 'even simpler model' from Semtner 1975, which I drew on in the above long comment, DLR is not included, the model depends on the temperature difference between the ice/ocean interface and the atmosphere/ice interface. See this thread:
http://forum.arctic-sea-ice.net/index.php/topic,933.150.html (http://forum.arctic-sea-ice.net/index.php/topic,933.150.html)
Messages 150, 157, and 160 for details and comparison with PIOMAS over the East Siberian Sea.
Title: Re: Latest PIOMAS update (October)
Post by: jdallen on October 13, 2014, 09:15:59 PM
Permit me to dovetail just a bit with Chris.

While I have spoken to heat levels, as important to the formation, or not, of ice is heat flow.

As has been demonstrated elsewhere, there already far and away exists enough heat in the Arctic Ocean to keep it ice free.  What as yet does not exist, is a mechanism by which it could be evenly distributed.

I will add also, while peak insolation at high latitudes may be as much as 200W/M2, total insolation being delivered is massively reduced over what it was just a few days ago. At 73N right now, total daily insolation amounts to barely 1KWH/ day. That's far too little to offset radiation out of the system.  The only things keeping temperatures high is heat from the ocean combined with the currently surprisingly high inputs of heat via weather from lower latitudes.

In fact, here's a pv calculator people can tinker with to get a sense of things.

http://pveducation.org/pvcdrom/properties-of-sunlight/calculation-of-solar-insolation (http://pveducation.org/pvcdrom/properties-of-sunlight/calculation-of-solar-insolation)

While intended to let one calculate power available for electrical generation, it is reasonable adaptable so one may get a "thumb nail sketch" of energy available as heat.  Multiply by 1-albedo, and you can get a sense of what is available to heat the system.
Title: Re: Latest PIOMAS update (October)
Post by: mark on October 13, 2014, 10:53:07 PM
Its just a thought, but could it be that the slow warming of the seas and resultant reduction in ice volume over recent years has had an effect on the strength of the warm surface flow into the Arctic due to increased fresher water flow into the N Atlantic from the Labrador current. This should make a small change to the temperature and volume of the flow through the subpolar gyre. The fact that climatic temperature changes over Greenland are always substantially enhanced compared with other regions of the Arctic, it would seem that this flow is climatically very sensitive.

Over 30 years is there any evidence that this is the case (weakening of the sub polar gyre). As perhaps the recent recoveries are the result of long term sensitivity that is just catching up. Should this be the case then increased freezing in winter from a position of lower ice extent and volume (ie greater recovery) would lead to increasing saline flows into the Arctic Bottom Water and N Atlantic Deep water and a greater flow out of the Arctic between Scotland and Greenland. Eventually completing the cycle by pulling larger volumes of water back into the Arctic through the N Atlantic Drift, starting another warming period. Throw into this equation lower insolation due to lower solar energy, is this the reason for the signs of recovery now. If so how long is the cycle likely to last - if it is 20 years as some sources are implying, the next cycle is likely to come back with a bang
Title: Re: Latest PIOMAS update (October)
Post by: jdallen on October 14, 2014, 10:12:30 AM
Its just a thought, but could it be that the slow warming of the seas and resultant reduction in ice volume over recent years has had an effect on the strength of the warm surface flow into the Arctic due to increased fresher water flow into the N Atlantic from the Labrador current. This should make a small change to the temperature and volume of the flow through the subpolar gyre. The fact that climatic temperature changes over Greenland are always substantially enhanced compared with other regions of the Arctic, it would seem that this flow is climatically very sensitive.

Over 30 years is there any evidence that this is the case (weakening of the sub polar gyre). As perhaps the recent recoveries are the result of long term sensitivity that is just catching up. Should this be the case then increased freezing in winter from a position of lower ice extent and volume (ie greater recovery) would lead to increasing saline flows into the Arctic Bottom Water and N Atlantic Deep water and a greater flow out of the Arctic between Scotland and Greenland. Eventually completing the cycle by pulling larger volumes of water back into the Arctic through the N Atlantic Drift, starting another warming period. Throw into this equation lower insolation due to lower solar energy, is this the reason for the signs of recovery now. If so how long is the cycle likely to last - if it is 20 years as some sources are implying, the next cycle is likely to come back with a bang

Pondering what you are saying here, some purely qualitative thoughts.

Regarding fresh water flow - during the decline of the last glaciation there were some very distinct , and (possibly) in the case of the Dryas - catastrophic - changes in fresh water flow into the Arctic and North Atlantic by way of release of impounded melt water and considerable volume reduction melt from stagnant ice sheets.  The volumes to cause those changes was pretty extraordinary - thousands of KM3 over prompt periods.

The annual melt in the Arctic and off of Greenland is on that scale, but even though our endpoints - Volume at Max and Volume at Min - have driven lower, the average melt during the season remains reasonably constant.  We gain, and then lose reasonably close to the same volume each year, within about 20%.  That 20% while in scale of the ice is large, in terms of fresh water displacement is not.  We need to remember that additional 2-3K KM3 of meltwater is across several million square miles of arctic surface.  The net increase in surface fresh water is a matter of centimeters.  I don't think that is affecting the "conveyor" yet.  What *will* affect the conveyor most dramatically I think, is when the haline engine slows and stops because no ice is forming.

Compared to current flow also, the volume of exchange resulting from ice formation is trivial compared to over-all current volume.  Consider that the Gulf Stream/NA Drift system is moving 150,000,000 cubic meters a second past any given point near Newfoundland.  Farther on, the North Atlantic Drift drops to 10% of that figure - about 15,000,000 meters a second. That still adds up to a KM3 about every minute.  If my math and scale is correct, that's close to 1400 KM3/day moving steadily north - which annually adds up to 30+ times the volume of ice melted over an entire season. 

Not all of that makes it to the Arctic by any means, but it highlights this - the overall contribution of melt to drive this flow is quite small.  There are other mechanisms driving it completely independent of ice formation.

You make a reference to solar cycles as well.  I think it needs to be pointed out that the estimated variation in solar energy during those cycles is significantly less than the forcing caused by the additional CO2 added to the atmosphere by human activity over the last century and a half.  Numbers I see suggest a total variation of insolation during typical cycles being less than 1 watt/M2, generally less than 0.5/watt/M2.  As the change in forcing by CO2 is at least double that, it is highly doubtful a downswing in insolation will significantly impede the on-going increase in heat in the environment.

http://www.esrl.noaa.gov/gmd/aggi/aggi.fig3.png (http://www.esrl.noaa.gov/gmd/aggi/aggi.fig3.png)
Title: Re: Latest PIOMAS update (October)
Post by: mark on October 14, 2014, 12:57:11 PM
Thanks very much for the reply - I wasnt alluding to a strong connection to solar cycles more that the reduced insolation may have a small effect. I perhaps come from a different viewpoint in that I like to look for evidence of balances within the system. I cant point to specific references but I do read as many of the references on this site (and others) as I can and Ive been looking at ASLR's very full thread as well as this one. There are just too many feedbacks to be able to narrow anything down. Each subject is fascinating and well supported with facts and figures, but as you quite rightly pointed out the ocean currents are absolutely collossal which is why It makes sense that very small changes to the flow can have big consequences, but all over a considerably longer period than just the last 18 years of levelling temperatures.

I havent got the depth of knowledge or the ability to 'see' the data as some on here do. But whether its freshwater (adequately rebuffed! thank you) or the reduced saline flows I have read too many times that the Sub Polar Gyre has slowed somewhat. So really I was asking if this is conjecture or whether it is fact based. If so is the present recovery purely down to meteorological coincidence or down to a shift in the way the gyres are transporting heat. Its a frustrating subject which is why I admire the persistence of the posters on this site.

I'm sorry if my response is a bit slow - I'm a 'newbie' so currently being moderated
Title: Re: Latest PIOMAS update (October)
Post by: ChrisReynolds on October 14, 2014, 10:27:04 PM
I'll reply tomorrow night, it's now late and I'm whacked.

Actually nothing I feel I need to reply to.  :)

Night off.  8)
Title: Re: Latest PIOMAS update (October)
Post by: viddaloo on October 15, 2014, 05:29:09 AM
I would like to see a statistical analysis of this data with a trend analysis for cumulative loss between June 1st and August 1st.  Then the deviation from the trend for 2014 can be more adequately addressed.

just by looking at the graph I am certain it surpasses the 2 sigma deviation from the trend (possibly 3!)

It would be absolutely foolhardy to imply that this extreme event can be anything indicative of a long-term trend.

however, it does indicate some kind of larger systemic shift, a "not-seen-before" event.  Either natural or unnatural it indicates a significant loss of boundary between the Ferrel and Arctic Cells  And/or some form of conscious manipulation of the atmospheric regimes.
This graph shows deviations from the 1979—2014 average for each day June 1st to August 1st, with deviations for first day, June 1st, leveled to zero and subtracted (for better comparison) for that year.

As you can see, there is a clear trend (2008, 2010, 2011, 2012, 2013, 2014) towards smaller losses after Solstice, which I've addressed in this thread (http://forum.arctic-sea-ice.net/index.php/topic,980.0.html). 2014 is the most extreme year in this trend so far. My personal theory is that of an increase in Boreal forest fires as the Arctic goes warmer, dryer and more snow–free, and that vast amounts of smoke from these fires reduce insolation (negative feedback).
Title: Re: Latest PIOMAS update (October)
Post by: jai mitchell on October 15, 2014, 06:47:38 AM
Thanks VID, but. . .

More specifically, I would like the SLOPES of the runs between June 1 and Aug 1 for the last 20 years.

Then a statistical analysis of the plots can be deduced with a standard deviation for the 2014 value to determine how far from the trend it is.

to do this I need the june 1 and aug 1 values of volume any idea where that data is?
Title: Re: Latest PIOMAS update (October)
Post by: viddaloo on October 15, 2014, 09:02:06 AM
1979,31368,20179
1980,30925,19546
1981,28843,16610
1982,27330,16425
1983,29396,18585
1984,28872,17678
1985,29501,17471
1986,29533,18837
1987,30674,18510
1988,29074,17896
1989,28782,17882
1990,27484,16355
1991,28872,16722
1992,28464,17451
1993,28114,15016
1994,28464,16649
1995,26009,13999
1996,26464,16260
1997,27747,15974
1998,27611,15067
1999,26872,15090
2000,25675,13960
2001,25696,14919
2002,25722,13823
2003,24854,12992
2004,24474,13326
2005,23880,12125
2006,23076,11805
2007,21744,8964
2008,22787,11050
2009,22300,9698
2010,20100,7283
2011,19356,6882
2012,19416,6538
2013,20390,7705
2014,20081,9422
Title: Re: Latest PIOMAS update (October)
Post by: crandles on October 15, 2014, 01:27:54 PM
Losses:
11189
11379
12233
10905
10811
11194
12030
10696
12164
11178
10900
11129
12150
11013
13098
11815
12010
10204
11773
12544
11782
11715
10777
11899
11862
11148
11755
11271
12780
11737
12602
12817
12474
12878
12685
10659


Avg   11702
St deva   742

2014 from average 1043
This is just 1.4 standard deviations which could quite easily occur by chance and indeed there is a lower value 10204 for 1996.

Above just assumes no trend.

However there does seems an trend curving upwards. If you believe that pattern is as expected then average of 5 years 2009-2013 is 12691. 2014 differs from this by 2032 and a standard deviation from this trend would be less than 742 so it is looking like a 3SD event.

More precise calculation may well be possible but requires a decision on what type of rising pattern is justified.
Title: Re: Latest PIOMAS update (October)
Post by: jai mitchell on October 16, 2014, 07:28:53 AM
Thanks JD and Crandals, I expect that we are dealing with a second order feedback analysis that includes a tipping point that was reached sometime around 2005 therefore the multi decadal analysis will hold too much deviation from the average (read: 1996 anomaly).  but The trend is definitely pushing 3-sig.

We may be operating in a dynamic environment that is so extreme that no trend analysis can be made, at least not for another decade or so.

Title: Re: Latest PIOMAS update (October)
Post by: jdallen on October 16, 2014, 06:49:21 PM
Looking at those volume numbers, what jumps out at me is the trend at maximum.  Since 2000, the volume at maximum has dropped 20%. I actually haven't been looking at Max trends that closely, so that surprised me.

That reflects the enthalpy increases in the system and is more key than minimum.  Less ice increases the pack vulnerability to weather,  and makes for greater volatility in system behavior.

What are our chances of working out regional volume changes at Max? That might give us some interesting clues.

Edit - quick and dirty purely statistical prediction from trend... Purely to provide basis for further discussion.

2015 volume max volume - 19500 +/- 500
2015 volume min volume  -   7825 +/- 350
2029 first "ice free" summer (sub 1000 KM3 pack)
2053 first "ice free winter (sub 1000 KM3 winter max pack)
Title: Re: Latest PIOMAS update (October)
Post by: ChrisReynolds on October 16, 2014, 07:24:11 PM
What are our chances of working out regional volume changes at Max? That might give us some interesting clues.

Regional PIOMAS volume data available via this page:
http://dosbat.blogspot.co.uk/2013/12/regional-piomas-volume-data.html (http://dosbat.blogspot.co.uk/2013/12/regional-piomas-volume-data.html)
Title: Re: Latest PIOMAS update (October)
Post by: crandles on October 16, 2014, 07:26:56 PM
There is also
http://dosbat.blogspot.co.uk/2014/06/piomas-may-2014-part-2.html (http://dosbat.blogspot.co.uk/2014/06/piomas-may-2014-part-2.html)
 from Chris Reynolds blog.
Title: Re: Latest PIOMAS update (October)
Post by: jdallen on October 16, 2014, 07:59:31 PM
More thoughts I can't resist posting.

Crandles, Looking at your annual volume variation numbers (losses), I'm struck by how consistent the annual arctic energy budget is.  Considering even the small size of the sample, there are no +2SD outliers.  Even more interesting is the SD range itself... Even the recent "big" melt years are inside the 1SD envelope, which is about 6%.

That confirms for me the inputs into the system are increasing incrementally, at very small values. The rate at which heat is shed during refreeze remains constant. The primary force driving the downward trend is the increasing residual heat in the system at the end of the melt season, not weather or increasing temperatures directly.
Title: Re: Latest PIOMAS update (October)
Post by: crandles on October 16, 2014, 11:40:25 PM
You do realise those are 1 June and 1 Aug volumes (and the change between those dates).

Also
2010,20100
2011,19356
2012,19416
2013,20390
2014,20081

doesn't seem to be reducing much recently.

Also
11702-742*2 = 10218 so 10204 is outside 2 sd

Expect 1 in 20 items to be outside 2 sd. So in a list of 36 would normally expect to see 2 such values but just 1 is not wildly different from the expectation.
Title: Re: Latest PIOMAS update (October)
Post by: jdallen on October 17, 2014, 03:00:34 AM
You do realise those are 1 June and 1 Aug volumes (and the change between those dates).

Also
2010,20100
2011,19356
2012,19416
2013,20390
2014,20081

doesn't seem to be reducing much recently.

Also
11702-742*2 = 10218 so 10204 is outside 2 sd

Expect 1 in 20 items to be outside 2 sd. So in a list of 36 would normally expect to see 2 such values but just 1 is not wildly different from the expectation.
<wry look>  Thank you for the detail correction.

No, no significant  change over the last few years - oscillation mostly.

I think my point still stands - the drop over 14 years - 25% - I think is quite significant.  I think it still points at net energy in the system being what is driving the long term trend, rather than changes in weather.

That increase in net energy is eventually tied back to the forcing from CO2.  Now, to look at some regional numbers from the link to Chris's stuff you sent out earlier.
Title: Re: Latest PIOMAS update (October)
Post by: crandles on October 17, 2014, 01:06:10 PM
I think my point still stands - the drop over 14 years - 25% - I think is quite significant.  I think it still points at net energy in the system being what is driving the long term trend, rather than changes in weather.

[point being]
That confirms for me the inputs into the system are increasing incrementally, at very small values. The rate at which heat is shed during refreeze remains constant. The primary force driving the downward trend is the increasing residual heat in the system at the end of the melt season, not weather or increasing temperatures directly.

In the 1 June figures, I think I would suggest the pattern is:
5k drop from 1980 to 2002 22 years
3k drop in 5 years
2k drop in 7 years

2002 to 2007 shows a fast drop between slower sections. The fast drop seems like MYI became FYI or changed thickness so little over 2m. As thickness reduces towards 2m, it can no longer drop at a fast rate as winter restores that thickness. So the rate of drop reduces and it becomes more like oscillation.

So while you may well be correct to deduce incremental change over the 36 year period, the validity of that in the last few years and going forward is much more questionable (in my opinion)
Title: Re: Latest PIOMAS update (October)
Post by: crandles on October 17, 2014, 02:02:32 PM
https://sites.google.com/site/arctischepinguin/home/piomas/grf/piomas-trnd2.png

now suggests Sept 2019 for zero ice, (2018 for 1k km^3).

Wadhams at RS meeting on 22/23 September 2014 showed old image* with zero as soon as 2015. See page 10 onwards for discussion of this:
https://drive.google.com/file/d/0BzOmEySKhRVOc1prYUNLQXhoa3c/view

* couldn't be expected to include 2014 data at this was in Sept 14 but Sept 13 should have been included.

COMMENTARY This is the source of the data set around which Peter Wadhams has built his notable and controversial prediction of the disappearance of sea ice. Brandon tweeted that it is linked to data thus making the point that it is not just a computational model but has basis in measurements. However, note that the data originators – when questioned later in the week at the follow on Discussion Meeting – do not believe prediction such as Wadhams proceeds to do is appropriate.

Note that it is Wadhams that has made complaints about tweets during this meeting.
Also PIOMAS team have made that clear before.

One of the tweets was
Wadhams still using graphs with ridiculous projections with no basis in physics

It seems this is being robustly defended
There has been wide criticism of this methodology since no convincing physical basis for such behaviour has been presented.

Disagreement? Yes. Grounds for complaint? Clearly not AFAICS
Title: Re: Latest PIOMAS update (October)
Post by: ChrisReynolds on October 17, 2014, 07:33:50 PM
Stoat's good on this issue.
http://scienceblogs.com/stoat/2014/10/07/wadhams-and-the-mighty-shtwit-storm/ (http://scienceblogs.com/stoat/2014/10/07/wadhams-and-the-mighty-shtwit-storm/)
Title: Re: Latest PIOMAS update (October)
Post by: jdallen on October 17, 2014, 09:17:26 PM
So while you may well be correct to deduce incremental change over the 36 year period, the validity of that in the last few years and going forward is much more questionable (in my opinion)

Reasonable criticisms, worthy of further thought.

After spending time wit the regional 2000-2014 volume data Chris supplied, I'm struck by how asymmetric the changes are over time.  The change in behavior over the last 7-10 years seems very much tied to volatility in peripheral seas, which are melting out completely with increasing frequency.  However, given the right weather, they are still close enough to some systemic threshold that we observe good retention (relatively) and wild swings in metrics.

Each peripheral region in turn, save Greenland and the CAA, has dropped in peak volume to the point that the typical, not exceptional, spring and summer melt take them to zero volume.  Where ice remains is by way of reductions of normal energy input, or transport (in the case of the Barents specifically) from other regions.  I think this volatility may hide a trend, as each region year over year more often than not have experienced significant variations in weather, both over time with themselves season over season, and with each other, during the same season.   2014 may be our poster child for this.

So, while your criticisms require consideration, there may exist reasonable explanations for your questions.
Title: Re: Latest PIOMAS update (October)
Post by: viddaloo on November 05, 2014, 08:42:23 PM
Funny how PIOMAS want my email address every time I download data, but never use said address to notify of new data dumps. Nor for alerts that the data will be delayed. Let's hope the new Senate doesn't make them even more cash–strapped. Seem to be on a shoestring budget as it is.
Title: Re: Latest PIOMAS update (October)
Post by: viddaloo on November 07, 2014, 09:18:13 PM
Looks like the plan is to call it a week, with no dump from PIOMAS till Monday the 10th. Just wondering whether PIOMAS data has ever been this late before? And same thing for IJIS extent: The update for November 6th is now 17 hours (and running) late, after their server crash.

Neither source seems to believe in the use of information architecture to inform about unforeseen events or delays. They don't use the web for this, they don't use Twitter for this and as mentioned above: Even when they harvest your email address, they don't use this to inform you once a month when new data is available. I wonder why.
Title: Re: Latest PIOMAS update (October)
Post by: viddaloo on November 08, 2014, 03:02:47 AM
Fresh PIOMAS Volume numbers for October 2014:

:
2014 274   7.154
2014 275   7.191
2014 276   7.227
2014 277   7.284
2014 278   7.334
2014 279   7.382
2014 280   7.434
2014 281   7.486
2014 282   7.548
2014 283   7.614
2014 284   7.691
2014 285   7.773
2014 286   7.849
2014 287   7.939
2014 288   8.020
2014 289   8.090
2014 290   8.172
2014 291   8.278
2014 292   8.383
2014 293   8.481
2014 294   8.598
2014 295   8.691
2014 296   8.779
2014 297   8.850
2014 298   8.947
2014 299   9.027
2014 300   9.114
2014 301   9.224
2014 302   9.362
2014 303   9.520
2014 304   9.701
Title: Re: Latest PIOMAS update (October)
Post by: viddaloo on November 08, 2014, 03:42:33 AM
2014 gained 0.4k km³ in October compared to the late 20th century average gain. That places 2014 ahead of the current trend of increased October gains, just above the orange 11/14 average.

Title: Re: Latest PIOMAS update (November)
Post by: Wipneus on November 08, 2014, 08:47:43 AM
Updated, graphs are in the top post (https://forum.arctic-sea-ice.net/index.php/topic,119.0.html).

(gridded data updated also, I will post the graphs later)
Title: Re: Latest PIOMAS update (November)
Post by: Wipneus on November 08, 2014, 05:13:10 PM
Here are thickness maps for October 2013 and 2014 as well as their difference.
Title: Re: Latest PIOMAS update (November)
Post by: Wipneus on November 08, 2014, 05:16:02 PM
And difference in growth from September to October, red means more thickening/less thinning.
Title: Re: Latest PIOMAS update (November)
Post by: viddaloo on November 10, 2014, 05:50:47 PM
I'm quite happy with the accuracy of my PIOMAS estimate formula this month. 20 days out of 31 it was less than 2% off from the real thing. Here's how I did it, for those of you who speak PHP:

:
if($i>$currentmonthstart-1)
$piomas[$year][$i] = $ijis[$year][$i]/( ($ijis[$year-5][$i]/$piomas[$year-5][$i])
- (($ijis[$year-5][$currentmonthstart-1]/$piomas[$year-5][$currentmonthstart-1])
-($ijis[2014][$currentmonthstart-1]/$piomas[2014][$currentmonthstart-1])) );

In short, it uses the rate between extent and volume in October 5 years ago, which is known, to get volume (unknown) from another known variable; the current month extent data. It assumes the gap between the ext/vol rate that year and this year will be roughly the same through the month, and then follows that 2009 ext/vol rate graph up the peak and down again, as we move through October.

Why pick just 2009? Well, it's a spin-off from the Five Year Cycle hypothesis, that's why. Could another year have yielded even better estimates? Possibly, but 2009 is much more similar to 2014 when it comes to the rate between extent and volume, among many other things.

Will it work just as well in November? Only time will tell.
Title: Re: Latest PIOMAS update (November)
Post by: ChrisReynolds on November 10, 2014, 09:28:49 PM
Thanks Wipneus,

There seems to be a starting of Beaufort Gyre and Fram Strait export from the Central Arctic.
Title: Re: Latest PIOMAS update (November)
Post by: jdallen on November 10, 2014, 09:41:10 PM
Thanks Wipneus,

There seems to be a starting of Beaufort Gyre and Fram Strait export from the Central Arctic.

... which may herald a halt in the volume increases we've seen.  It will be interesting to track the movement out of the Fram.  Lack of Fram export was pretty key to MYI retention last summer.
Title: Re: Latest PIOMAS update (November)
Post by: ChrisReynolds on November 11, 2014, 06:58:39 PM
My thoughts exactly JD.
Title: Re: Latest PIOMAS update (November)
Post by: crandles on December 05, 2014, 10:47:54 PM
30Nov graphs now out:
(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fpsc.apl.uw.edu%2Fwordpress%2Fwp-content%2Fuploads%2Fschweiger%2Fice_volume%2FBPIOMASIceVolumeAnomalyCurrentV2.1_CY.png&hash=71e098ee33c36296b9e24f63de218d71)
Title: Re: Latest PIOMAS update (November)
Post by: viddaloo on December 06, 2014, 05:49:26 AM
:
2014 305   9.860
2014 306  10.020
2014 307  10.161
2014 308  10.319
2014 309  10.450
2014 310  10.576
2014 311  10.661
2014 312  10.751
2014 313  10.837
2014 314  10.927
2014 315  10.999
2014 316  11.075
2014 317  11.164
2014 318  11.307
2014 319  11.402
2014 320  11.475
2014 321  11.600
2014 322  11.720
2014 323  11.850
2014 324  11.978
2014 325  12.113
2014 326  12.238
2014 327  12.361
2014 328  12.494
2014 329  12.635
2014 330  12.789
2014 331  12.916
2014 332  13.048
2014 333  13.184
2014 334  13.314
Title: Re: Latest PIOMAS update (December)
Post by: Wipneus on December 06, 2014, 08:24:33 AM
Updated, graphs are in the top post.

(gridded data updated also, I will post the graphs later)
Title: Re: Latest PIOMAS update (December)
Post by: Wipneus on December 06, 2014, 08:46:09 AM
Here are thickness maps for November 2013 and 2014 as well as their difference.
Title: Re: Latest PIOMAS update (December)
Post by: Wipneus on December 06, 2014, 08:47:44 AM
And difference in growth from October to November, red means more thickening/less thinning.
Title: Re: Latest PIOMAS update (December)
Post by: viddaloo on December 06, 2014, 11:03:33 AM
Updated collapse estimate.
Title: Re: Latest PIOMAS update (December)
Post by: OSweetMrMath on December 06, 2014, 08:48:26 PM
Updated collapse estimate.

Your graph does not predict that there will be no Arctic sea ice year round in 2031. Your graph predicts that the average ice volume in 2031 will be 0.

The graph has a built in assumption that for approximately half the year, the ice volume will be below the stated average, and for the other half, it will be above the stated average. This does not change as the average approaches zero.

Effectively, the graph predicts that in 2031, the Arctic ice volume will be negative for six months out of the year.
Title: Re: Latest PIOMAS update (December)
Post by: viddaloo on December 06, 2014, 10:15:46 PM
Updated collapse estimate.

Your graph does not predict that there will be no Arctic sea ice year round in 2031. Your graph predicts that the average ice volume in 2031 will be 0.

The graph has a built in assumption that for approximately half the year, the ice volume will be below the stated average, and for the other half, it will be above the stated average. This does not change as the average approaches zero.

Effectively, the graph predicts that in 2031, the Arctic ice volume will be negative for six months out of the year.

Well, no. Actually, an inch of ice on just half a day will keep the average from going to zero.
Title: Re: Latest PIOMAS update (December)
Post by: OSweetMrMath on December 06, 2014, 10:30:38 PM
Well, no. Actually, an inch of ice on just half a day will keep the average from going to zero.

Then I don't understand how you are computing the prediction. It looks like you are computing the average each day over the previous 12 months, giving you the data in your graph. You are then fitting a curve to these average values. This curve reaches 0 in 2031.

If that is correct, then the 0 value for the curve means that the average over the 12 previous months is 0, not that every day for the previous 12 months is exactly 0. Unless you are directly compensating for the fact that the ice volume cannot be less than zero on any given day when you are fitting that curve, it builds in the idea that half the time, the ice volume will be below average.

When a large fraction of the days in the year have 0 ice, it becomes harder to reduce the average over the entire year. This should show up in a flattening of your curve as it approaches zero. I take the lack of flattening as evidence that you are averaging assuming negative ice rather than zero ice.
Title: Re: Latest PIOMAS update (December)
Post by: viddaloo on December 06, 2014, 10:36:00 PM
I don't know why many of you assume such things. IMO none of you have explained this sufficiently. In 2013 you had 365 days. Each of those days had their total ice volume figure. Add day 1 + day 2 ... + day 365 into a year total and divide by 365. Et voila!
Title: Re: Latest PIOMAS update (December)
Post by: ChrisReynolds on December 06, 2014, 11:29:15 PM
New PIOMAS blog post.
http://dosbat.blogspot.co.uk/2014/12/piomas-november-2014.html (http://dosbat.blogspot.co.uk/2014/12/piomas-november-2014.html)
Title: Re: Latest PIOMAS update (December)
Post by: OSweetMrMath on December 07, 2014, 02:07:38 AM
I shouldn't have said anything. My mistake.
Title: Re: Latest PIOMAS update (December)
Post by: Unmex Chingon on December 07, 2014, 05:25:30 PM
I don't know why many of you assume such things. IMO none of you have explained this sufficiently. In 2013 you had 365 days. Each of those days had their total ice volume figure. Add day 1 + day 2 ... + day 365 into a year total and divide by 365. Et voila!

And if you wanted to calculate Day 2 of 2014 - you would start with Day 2 of 2013 + day 3...+day 365 2013 + day 1 2014 and divide all that by 365 - Right?  If that is how you calculate then - I have a question for you though - in 2031 this calculation will result in Zero?
Title: Re: Latest PIOMAS update (December)
Post by: viddaloo on December 08, 2014, 06:18:01 AM
I don't know why many of you assume such things. IMO none of you have explained this sufficiently. In 2013 you had 365 days. Each of those days had their total ice volume figure. Add day 1 + day 2 ... + day 365 into a year total and divide by 365. Et voila!

And if you wanted to calculate Day 2 of 2014 - you would start with Day 2 of 2013 + day 3...+day 365 2013 + day 1 2014 and divide all that by 365 - Right?  If that is how you calculate then - I have a question for you though - in 2031 this calculation will result in Zero?

That is correct, well, almost: The AAV for day 2014/02 is (Day 3 of 2013 + day 4...+day 365 2013 + day 1 2014 + day 2 2014) divided by 365.

Of course I can't say if that calculation will result in zero in 2031, as the data for 2030 and 2031 aren't really in yet! What I can say is that the trend we see in AAV from 1980 to 2014 seems to end rather horribly in zero sometime during 2031 or the early thirties.

If you look at the purple part of the graph, that is the start of that move towards zero. And from what I can see in the purple real data part, we are almost half–way to zero in ice volume, and if the trend is correct, we're about 70% of the way to zero measured in time.
Title: Re: Latest PIOMAS update (December)
Post by: Unmex Chingon on December 08, 2014, 06:24:21 AM
I don't know why many of you assume such things. IMO none of you have explained this sufficiently. In 2013 you had 365 days. Each of those days had their total ice volume figure. Add day 1 + day 2 ... + day 365 into a year total and divide by 365. Et voila!

And if you wanted to calculate Day 2 of 2014 - you would start with Day 2 of 2013 + day 3...+day 365 2013 + day 1 2014 and divide all that by 365 - Right?  If that is how you calculate then - I have a question for you though - in 2031 this calculation will result in Zero?

That is correct, well, almost: The AAV for day 2014/02 is (Day 3 of 2013 + day 4...+day 365 2013 + day 1 2014 + day 2 2014) divided by 365.

Of course I can't say if that calculation will result in zero in 2031, as the data for 2030 and 2031 aren't really in yet! What I can say is that the trend we see in AAV from 1980 to 2014 seems to end rather horribly in zero sometime during 2031 or the early thirties.

If you look at the purple part of the graph, that is the start of that move towards zero. And from what I can see in the purple real data part, we are almost half–way to zero in ice volume, and if the trend is correct, we're about 70% of the way to zero measured in time.

So your projection is that the Artic will be with Zero ice for 12 consecutive months?  No refreeze at all during the winter seems to be a very bold prediction.
Title: Re: Latest PIOMAS update (December)
Post by: viddaloo on December 08, 2014, 07:44:53 AM
I don't think removing the last half of the ice is any more bold than removing the first half that was lost from 1979 to 2014. Did anyone in 1979 think that would happen? No. At that time they were talking about a new ice age, and any talk of massive ice–loss was just preposterous.

However, I'm glad that you and Mr Math comment on it. Humans make mistakes, and last time I checked the mirror, I looked very much like one of them humans. That means I can make mistakes. If I have in any way made mathematical mistakes by calculating the average volume, I would like you to point it out. If your objection is about the trendline, then please suggest a different sort of trendline that you believe is more plausible, plus the reasoning behind this.

Mine is
:

trendlines: {
   0: {
        type: 'polynomial',
        degree: 2,       
        visibleInLegend: false,
        color: 'green',
   },
}
Title: Re: Latest PIOMAS update (December)
Post by: Peter Ellis on December 08, 2014, 09:48:12 AM
I don't know why many of you assume such things. IMO none of you have explained this sufficiently. In 2013 you had 365 days. Each of those days had their total ice volume figure. Add day 1 + day 2 ... + day 365 into a year total and divide by 365. Et voila!

Yes, but you are then projecting that forward, and you need to be clear in your own mind (and in your posts) about what that projection entails. When you predict that (say) 2020 will be 3.5x10^6 km^3 lower than 2015, how is that actually playing out in terms of day to day volume? 

Do you think that every individual day will be 3.5x10^6 km^3 lower than the corresponding day 5 years previously (i.e. March 1st 2020 is 3.5x10^6 lower than April 1st 2015, September 1st 2020 is 3.5x10^6 lower than September 1st 2015, etc.)? 

Or will the losses be concentrated more in summer or winter?

If you start to think in genuine physical terms you'll see the problem - you predict that 2031 will be ~14x10^6 lower than today.  But the current rate of decline is based on curves that are getting lower all year (and summer declining faster than winter).  If you lower everything across the board by 14x10^6, you go negative in summer!  At some point these losses are going to start flattening out because of this effect.
Title: Re: Latest PIOMAS update (December)
Post by: viddaloo on December 08, 2014, 11:30:09 AM
Peter, I guess this — and the collapse graph — should more appropriately be discussed over at the Annual Average Thread (http://forum.arctic-sea-ice.net/index.php/topic,994.msg40899.html#new). As I've said I'm happy to discuss it, but I think right now it takes up too much space in this PIOMAS update thread, so better to discuss it in an on–topic thread for yearly averages.

I'll answer you there later today after some other — real world — business  ;D
Title: Re: Latest PIOMAS update (December)
Post by: crandles on December 08, 2014, 03:00:39 PM
Did anyone in 1979 think that would happen? No. At that time they were talking about a new ice age, and any talk of massive ice–loss was just preposterous.

Not so for scientists re expecting global cooling. Though perhaps the media liked it as a scare story.

http://journals.ametsoc.org/doi/abs/10.1175/2008BAMS2370.1 (http://journals.ametsoc.org/doi/abs/10.1175/2008BAMS2370.1)

An enduring popular myth suggests that in the 1970s the climate science community was predicting “global cooling” and an “imminent” ice age, an observation frequently used by those who would undermine what climate scientists say today about the prospect of global warming. A review of the literature suggests that, on the contrary, greenhouse warming even then dominated scientists' thinking as being one of the most important forces shaping Earth's climate on human time scales.





Title: Re: Latest PIOMAS update (November)
Post by: Neven on December 16, 2014, 12:19:14 AM
Here are thickness maps for October 2013 and 2014 as well as their difference.

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fforum.arctic-sea-ice.net%2Findex.php%3Faction%3Ddlattach%3Btopic%3D119.0%3Battach%3D11699%3Bimage&hash=7f3dcd9aad0a6b98c52dde1d2423d7c3)
I just posted a blog post over on the ASIB with some new CryoSat maps:

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fneven1.typepad.com%2F.a%2F6a0133f03a1e37970b01bb07c4b84c970d-800wi&hash=01e6dcef7f5262f1899cc57c47f91eee)

I know there have always been some discrepancies between PIOMAS and CryoSat, but the 2014-2013 difference between both graphs is quite pronounced, with CryoSat showing a lot less thick ice (red) this winter compared to last year's map. Whereas with PIOMAS it's the other way round.

Am I misinterpreting the maps? Did the CryoSat people accidentally swap the maps for 2013 and 2014?
Title: Re: Latest PIOMAS update (November)
Post by: viddaloo on December 16, 2014, 12:24:05 AM
Am I misinterpreting the maps? Did the CryoSat people accidentally swap the maps for 2013 and 2014?

No idea what happened there, Neven, but they don't seem to be swapped, at least: You clearly see the big extra ice area between Svalbard and Josef's land on the 2014 map, which is correct (and was not there last year).
Title: Re: Latest PIOMAS update (November)
Post by: Neven on December 16, 2014, 12:28:44 AM
Am I misinterpreting the maps? Did the CryoSat people accidentally swap the maps for 2013 and 2014?

No idea what happened there, Neven, but they don't seem to be swapped, at least: You clearly see the big extra ice area between Svalbard and Josef's land on the 2014 map, which is correct (and was not there last year).

Yes, indeed, that's the yellow on the CryoSat map. It's mostly the red that is causing the frown.
Title: Re: Latest PIOMAS update (December)
Post by: viddaloo on December 16, 2014, 12:41:50 AM
: BBC
The spacecraft observed 7,500 cu km of ice cover in October when the Arctic traditionally starts its post-summer freeze-up.

This was only slightly down on 2013 when 8,800 cu km were recorded.

That's interesting, as PIOMAS never has October near 8,800 (not even on October 30th) in 2013, while PIOMAS' October 2014 crosses 7,500 already on the 9th (and ends at 9,700 on the 30th):

:
2013 274 5.79 2014 7.15
2013 275 5.82 2014 7.19
2013 276 5.84 2014 7.23
2013 277 5.86 2014 7.28
2013 278 5.92 2014 7.33
2013 279 5.99 2014 7.38
2013 280 6.08 2014 7.43
2013 281 6.15 2014 7.49
2013 282 6.24 2014 7.55
2013 283 6.33 2014 7.61
2013 284 6.42 2014 7.69
2013 285 6.52 2014 7.77
2013 286 6.63 2014 7.85
2013 287 6.75 2014 7.94
2013 288 6.88 2014 8.02
2013 289 7 2014 8.09
2013 290 7.09 2014 8.17
2013 291 7.16 2014 8.28
2013 292 7.27 2014 8.38
2013 293 7.36 2014 8.48
2013 294 7.46 2014 8.6
2013 295 7.57 2014 8.69
2013 296 7.66 2014 8.78
2013 297 7.74 2014 8.85
2013 298 7.84 2014 8.95
2013 299 7.96 2014 9.03
2013 300 8.06 2014 9.11
2013 301 8.16 2014 9.22
2013 302 8.29 2014 9.36
2013 303 8.44 2014 9.52
2013 304 8.59 2014 9.7
Title: Re: Latest PIOMAS update (December)
Post by: Neven on December 16, 2014, 01:16:51 AM
I forgot the details, but I believe there are differences in total area that is counted by either PIOMAS or CryoSat. It's explained somewhere on the blog. So that shouldn't necessarily ring any bells.
Title: Re: Latest PIOMAS update (December)
Post by: viddaloo on December 16, 2014, 01:28:50 AM
Looking at the numbers in my previous comment, it is more likely that the egg is on BBC's face, and that their summary should read:

: Fictional competent BBC reporter
The spacecraft observed 8,800 cu km of ice cover in October when the Arctic traditionally starts its post-summer freeze-up.

This was only slightly up from 2013 when 7,500 cu km were recorded.
Title: Re: Latest PIOMAS update (December)
Post by: Neven on December 16, 2014, 01:35:35 AM
Looking at the numbers in my previous comment, it is more likely that the egg is on BBC's face, and that their summary should read:

: Fictional competent BBC reporter
The spacecraft observed 8,800 cu km of ice cover in October when the Arctic traditionally starts its post-summer freeze-up.

This was only slightly up from 2013 when 7,500 cu km were recorded.

But that still doesn't explain the graphs.

I guess we'll have to wait for wipneus and see what he thinks.
Title: Re: Latest PIOMAS update (December)
Post by: crandles on December 16, 2014, 01:46:47 AM
I forgot the details, but I believe there are differences in total area that is counted by either PIOMAS or CryoSat. It's explained somewhere on the blog. So that shouldn't necessarily ring any bells.

I wouldn't have thought area would make any difference for Oct/Nov. It might nearer maximum ice volume.

PIOMAS (line & circles) v Cryosat2 (triangles)
(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Ffarm9.staticflickr.com%2F8380%2F8480824625_949b101fcd_o.jpg&hash=2e2c2260ee155cd94d8b7976533085cc)
Have we had any update on this graph?


https://earth.esa.int/web/guest/missions/esa-operational-eo-missions/cryosat/news/-/article/cryosat-extends-its-reach-on-the-arctic (https://earth.esa.int/web/guest/missions/esa-operational-eo-missions/cryosat/news/-/article/cryosat-extends-its-reach-on-the-arctic)
Measurements made during October and November show that the volume of Arctic sea ice now stands at about 10,200 cubic km - a small drop compared to last year's 10,900 cubic km
.
Title: Re: Latest PIOMAS update (December)
Post by: crandles on December 16, 2014, 01:52:20 AM
In October 2013, CryoSat measured about 9000 cubic km of sea ice - a notable increase compared to 6000 cubic km in October 2012.

https://earth.esa.int/web/guest/missions/esa-operational-eo-missions/cryosat/news/-/asset_publisher/47bD/content/arctic-sea-ice-up-from-record-low?redirect=https%3A%2F%2Fearth.esa.int%2Fweb%2Fguest%2Fmissions%2Fesa-operational-eo-missions%2Fcryosat%2Fnews%3Fp_p_id%3D101_INSTANCE_47bD%26p_p_lifecycle%3D0%26p_p_state%3Dnormal%26p_p_mode%3Dview%26p_p_col_id%3Dcolumn-1%26p_p_col_pos%3D1%26p_p_col_count%3D2

So about 9000 or maybe 8800 does seem right for 2013.
Title: Re: Latest PIOMAS update (December)
Post by: Wipneus on December 16, 2014, 10:49:14 AM

But that still doesn't explain the graphs.

I guess we'll have to wait for wipneus and see what he thinks.

My first thought was that I never quite trusted the CS2 2013 October data. If I remember correctly half of the time the CS2 was shutdown and the operators were trying to rescue the satellite. I don't know how they filled in that permanently lost data.

If that is not the case, it is a strong reminder of the uncertainty in the data. Neither PIOMAS of Cryosat seems to be in a position to have the benefit of the doubt when there is a mismatch.

https://forum.arctic-sea-ice.net/index.php/topic,8.msg15924.html#msg15924
Title: Re: Latest PIOMAS update (December)
Post by: Neven on December 16, 2014, 12:03:56 PM
Here (http://neven1.typepad.com/blog/2013/12/cryosat-arctic-sea-ice-up-from-record-low.html)'s the post I did last year, and back then the graphs looked like this (they changed the legend's colour scheme):

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fneven1.typepad.com%2F.a%2F6a0133f03a1e37970b01a3fa8e03af970b-pi&hash=a99ae14195980c2d2a30bb193dc1e5eb)
Title: Re: Latest PIOMAS update (December)
Post by: Steven on December 16, 2014, 09:34:49 PM
I forgot the details, but I believe there are differences in total area that is counted by either PIOMAS or CryoSat. It's explained somewhere on the blog. So that shouldn't necessarily ring any bells.

Here is the domain (https://forum.arctic-sea-ice.net/index.php/topic,8.msg946.html#msg946) over which the sea ice volume is usually calculated in the context of CryoSat  (and also for the earlier ICESat satellite).  It excludes regions like Kara, Barents, Greenland Sea, and Canadian Archipelago:

(https://sites.google.com/site/arctischepinguin/home/piomas/grf/IceSat_on_Piomas.png)

I used Chris Reynolds' regional volume data to estimate the PIOMAS volume inside and outside this domain respectively.

October PIOMAS volume:

:

year    volume_inside (km^3)   volume_outside (km^3)
2010    5657                   541
2011    5220                   499
2012    4578                   423
2013    6349                   604
2014    7192                   966


November PIOMAS volume:

:

year    volume_inside (km^3)   volume_outside (km^3)
2010    7916                   1564
2011    7745                   1505     
2012    7036                   1180
2013    8430                   1645
2014    9306                   2174
Title: Re: Latest PIOMAS update (December)
Post by: ChrisReynolds on December 16, 2014, 09:53:43 PM
Thanks Steven,
Title: Re: Latest PIOMAS update (December)
Post by: diablobanquisa on December 17, 2014, 01:34:06 AM
Cryosat-2 October-November data:
2010  8283 km3    (Laxon et al. 2013)
2011  6838 km3    (Laxon et al. 2013)
2012     ??              (Not published)
2013  10900 km3  (ESA 2014)
2014  10200 km3  (ESA 2014)

Cryosat-2 October data:
2010   ??            (Not published)
2011 5300 km3 (BBC 2014)
2012 5400 km3 (BBC 2014) (6000 km3 ??  ESA and BBC 2013)
2013 8800 km3 (BBC 2014) (9000 km3 ??  ESA and BBC 2013)
2014 7500 km3 (BBC 2014)

ESA 2013 (http://www.esa.int/Our_Activities/Observing_the_Earth/CryoSat/Arctic_sea_ice_up_from_record_low):
In October 2013, CryoSat measured about 9000 cubic km of sea ice – a notable increase compared to 6000 cubic km in October 2012

ESA 2014 (http://www.esa.int/Our_Activities/Observing_the_Earth/CryoSat/CryoSat_extends_its_reach_on_the_Arctic):
Measurements made during October and November show that the volume of Arctic sea ice now stands at about 10 200 cubic km – a small drop compared to last year’s 10 900 cubic km.

BBC 2014 (http://www.bbc.com/news/science-environment-30399079):
The spacecraft observed 7,500 cu km of ice cover in October when the Arctic traditionally starts its post-summer freeze-up. This was only slightly down on 2013 when 8,800 cu km were recorded. The deep lows in this short series were 5,300 and 5,400 cubic km in 2011 and 2012, respectively.

BBC 2013 (http://www.bbc.com/news/science-environment-25383373):
In the three years following its launch, the spacecraft saw a steady decline in autumn ice volume, with a record low of 6,000 cubic km being recorded in late October 2012. But after a sharply colder summer this year, the autumn volume number has gone up. Measurements taken in the same three weeks in October found the floes to contain just shy of 9,000 cu km.


Laxon et al. 2013:  http://psc.apl.washington.edu/zhang/Pubs/Laxon_etal2013_icevol_grl50193.pdf (http://psc.apl.washington.edu/zhang/Pubs/Laxon_etal2013_icevol_grl50193.pdf) (look at Table 1)


A little chaotic...  :o
Title: Re: Latest PIOMAS update (December)
Post by: Neven on December 17, 2014, 10:00:10 AM
Cryosat-2 October-November data:
2010  8283 km3    (Laxon et al. 2013)
2011  6838 km3    (Laxon et al. 2013)
2012     ??              (Not published)
2013  10900 km3  (ESA 2014)
2014  10200 km3  (ESA 2014)

Cryosat-2 October data:
2010   ??            (Not published)
2011 5300 km3 (BBC 2014)
2012 5400 km3 (BBC 2014) (6000 km3 ??  ESA and BBC 2013)
2013 8800 km3 (BBC 2014) (9000 km3 ??  ESA and BBC 2013)
2014 7500 km3 (BBC 2014)

ESA 2013 (http://www.esa.int/Our_Activities/Observing_the_Earth/CryoSat/Arctic_sea_ice_up_from_record_low):
In October 2013, CryoSat measured about 9000 cubic km of sea ice – a notable increase compared to 6000 cubic km in October 2012

ESA 2014 (http://www.esa.int/Our_Activities/Observing_the_Earth/CryoSat/CryoSat_extends_its_reach_on_the_Arctic):
Measurements made during October and November show that the volume of Arctic sea ice now stands at about 10 200 cubic km – a small drop compared to last year’s 10 900 cubic km.

BBC 2014 (http://www.bbc.com/news/science-environment-30399079):
The spacecraft observed 7,500 cu km of ice cover in October when the Arctic traditionally starts its post-summer freeze-up. This was only slightly down on 2013 when 8,800 cu km were recorded. The deep lows in this short series were 5,300 and 5,400 cubic km in 2011 and 2012, respectively.

BBC 2013 (http://www.bbc.com/news/science-environment-25383373):
In the three years following its launch, the spacecraft saw a steady decline in autumn ice volume, with a record low of 6,000 cubic km being recorded in late October 2012. But after a sharply colder summer this year, the autumn volume number has gone up. Measurements taken in the same three weeks in October found the floes to contain just shy of 9,000 cu km.


Laxon et al. 2013:  http://psc.apl.washington.edu/zhang/Pubs/Laxon_etal2013_icevol_grl50193.pdf (http://psc.apl.washington.edu/zhang/Pubs/Laxon_etal2013_icevol_grl50193.pdf) (look at Table 1)


A little chaotic...  :o

You can say that again. Every year different maps with different legends as well.

I'm tempted to say that CryoSat is perhaps not delivering what was hoped for.
Title: Re: Latest PIOMAS update (December)
Post by: Peter Ellis on December 17, 2014, 10:36:55 AM
Most of those seem consistent with each other, the only one that's very different is the second quote which explicitly refers to October AND NOVEMBER, so it's not talking about the actual lowest point.

Table 1 in the Laxton document covers Oct/Nov AND is looking only at the ICESat domain to compare things to the previous satellite, so there's no reason to expect it to be simply comparable to the other figures.
Title: Re: Latest PIOMAS update (December)
Post by: diablobanquisa on December 17, 2014, 01:18:58 PM
Hi Peter,
-Which is the lowest year (October)? 2012? (BBC 2013) Or 2011? (BBC 2014)
-Which is the lowest October value? 6000 km3? (BBC 2013 and ESA 2013) Or 5300 km3? (BBC 2014)

I'd like to see a complete and consistent time series from 2010 to 2014. And I don't mind if it uses  'October', 'October/November' or 'October and November' data. I'm just asking for the same metric every year.
(Of course, if I could choose I'd prefer a consistent with Icesat metric )


Title: Re: Latest PIOMAS update (December)
Post by: ChrisReynolds on December 17, 2014, 06:42:43 PM
Hi Peter,
-Which is the lowest year (October)? 2012? (BBC 2013) Or 2011? (BBC 2014)
-Which is the lowest October value? 6000 km3? (BBC 2013 and ESA 2013) Or 5300 km3? (BBC 2014)

I'd like to see a complete and consistent time series from 2010 to 2014. And I don't mind if it uses  'October', 'October/November' or 'October and November' data. I'm just asking for the same metric every year.
(Of course, if I could choose I'd prefer a consistent with Icesat metric )

I agree. You shouldn't have to stop yourself and ask if the latest data is according to a different measure than the previous. And it would seem reasonable to allow easy comparison for the IceSat domain to be used for public data release.

I still consider that the best long term proxy for volume is PIOMAS, I will keep on using that in preference to IceSat.
Title: Re: Latest PIOMAS update (December)
Post by: viddaloo on December 17, 2014, 07:05:52 PM
Cryosat seems to be the only direct measurement of sea ice volume, so for sea ice volume purposes, I'd go for Cryosat, rather than PIOMAS or Icesat.
Title: Re: Latest PIOMAS update (December)
Post by: ChrisReynolds on December 17, 2014, 08:17:32 PM
Cryosat seems to be the only direct measurement of sea ice volume, so for sea ice volume purposes, I'd go for Cryosat, rather than PIOMAS or Icesat.

ICESat ran back in the early 2000s, it used a LIDAR to measure sea ice free board. Ron Kwok at JPL had a series of papers looking at the results. It was a direct measurement of sea ice thickness. ICESat results were used in the calibration of PIOMAS.
http://scholar.google.co.uk/scholar?hl=en&q=kwok+icesat&btnG=&as_sdt=1%2C5&as_sdtp= (http://scholar.google.co.uk/scholar?hl=en&q=kwok+icesat&btnG=&as_sdt=1%2C5&as_sdtp=)
Title: Re: Latest PIOMAS update (December)
Post by: viddaloo on December 17, 2014, 11:50:23 PM
Radio EcoShock on the recent hacks against the NOAA computer systems: ES_141217_LoFi.mp3 (http://www.ecoshock.net/downloads/ES_141217_LoFi.mp3) (min. 14 onwards, if you are short on time)
Title: Re: Latest PIOMAS update (December)
Post by: crandles on December 18, 2014, 02:11:04 PM
For Cryosat vs PIOMAS difference see Artic report card thread:

: Arctic report Card
Recent studies of the impact of snow layer properties on CryoSat-2 freeboard retrieval conclude that radar backscatter from the snow layer may lead to a bias in sea ice freeboard if it is not included in the retrieval process (Ricker et al. 2014, Kwok et al. 2014). Current sea-ice thickness data products from CryoSat-2 are, therefore, based on the assumption that the impact of the snow layer on radar freeboard is constant from year to year and snow depth can be sufficiently approximated by long-term observation values.
Perhaps ESA is suffering from the 'radar backscatter from the snow layer' issue?
Title: Re: Latest PIOMAS update (December)
Post by: ChrisReynolds on December 18, 2014, 07:12:23 PM
Thanks Crandles,

I've said before that this is a major reason to view Cryosat with caution.
Title: Re: Latest PIOMAS update (January)
Post by: Wipneus on January 06, 2015, 01:02:25 PM
The daily PIOMAS data is still not in, but gridded data is. From it we can estimate that in December the volume was 1654 km3 more than in 2013.  In November the difference was 1859 km3.

Here are thickness maps for December 2013 and 2014 as well as their difference.
Title: Re: Latest PIOMAS update (January)
Post by: Wipneus on January 06, 2015, 01:04:13 PM
And difference in growth from November to December, red means more thickening/less thinning.
Title: Re: Latest PIOMAS update (January)
Post by: A-Team on January 06, 2015, 05:38:17 PM
I dumbed down the excellent graphic above to 3 color classes and took percent of pixels as an approximation to sq km of area, below.

Four papers at AGU mentioned PIOMAS in their abstract. None of these provided an ePoster:

C43B-0397 Estimation of Sea Ice Thickness through Maximum Covariance Analysis
https://agu.confex.com/agu/fm14/meetingapp.cgi#Paper/26406

C53A-0292 Arctic Ocean Sea Ice Thickness, Bathymetry, and Water Properties from Submarine Data
https://agu.confex.com/agu/fm14/meetingapp.cgi#Paper/18799

B41E-0103 Changing Seasonality of Tundra Vegetation and Associated Climatic Variables
https://agu.confex.com/agu/fm14/meetingapp.cgi#Paper/9002

C11A-0354 MIZMAS Forecast of Sea Ice Thickness and Drift in the Beaufort Sea Marginal Ice Zone
https://agu.confex.com/agu/fm14/meetingapp.cgi#Paper/31003

Eleven Arctic abstracts were accompanied by an ePoster: see screenshot below for titles.

https://agu.confex.com/data/handout/agu/fm14/Paper_26223_handout_790_0.pdf
https://agu.confex.com/data/handout/agu/fm14/Paper_3556_handout_319_0.pdf
https://agu.confex.com/data/handout/agu/fm14/Paper_7358_handout_773_0.pdf
https://agu.confex.com/data/handout/agu/fm14/Paper_10720_handout_301_0.pdf
https://agu.confex.com/data/handout/agu/fm14/Paper_16731_handout_1975_0.pdf
https://agu.confex.com/data/handout/agu/fm14/Paper_20721_handout_1782_0.pdf
https://agu.confex.com/data/handout/agu/fm14/Paper_21258_handout_1771_0.pdf
https://agu.confex.com/data/handout/agu/fm14/Paper_27927_handout_923_0.pdf
https://agu.confex.com/data/handout/agu/fm14/Paper_30369_handout_2045_0.pdf
https://agu.confex.com/data/handout/agu/fm14/Paper_30841_handout_1409_0.pdf
https://agu.confex.com/data/handout/agu/fm14/Paper_8127_handout_1971_0.pdf
Title: Re: Latest PIOMAS update (January)
Post by: Steven on January 08, 2015, 11:26:02 PM
Daily PIOMAS data for December 2014 now available:
http://psc.apl.uw.edu/research/projects/arctic-sea-ice-volume-anomaly (http://psc.apl.uw.edu/research/projects/arctic-sea-ice-volume-anomaly)

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fpsc.apl.uw.edu%2Fwordpress%2Fwp-content%2Fuploads%2Fschweiger%2Fice_volume%2FBPIOMASIceVolumeAnomalyCurrentV2.1_CY.png&hash=71e098ee33c36296b9e24f63de218d71)

Currently 8th lowest on record.

Daily PIOMAS volume for December 31st, ranked:

1. 2012. 13.92 k km^3
2. 2010. 14.66
3. 2011. 15.01
4. 2013. 15.78
5. 2009. 15.95
6. 2007. 16.39
7. 2006. 16.55
8. 2014. 16.84   
9. 2008. 16.89
10. 2005. 17.72
...
Title: Re: Latest PIOMAS update (January)
Post by: Neven on January 09, 2015, 12:22:51 AM
Thanks, Steven. I'll have a blog post up on the ASIB tomorrow evening.
Title: Re: Latest PIOMAS update (January)
Post by: Wipneus on January 09, 2015, 06:00:55 AM
Updated, graphs are in the top post (https://forum.arctic-sea-ice.net/index.php/topic,119.0.html).

(gridded data was already updated earlier this week, graphs above)
Title: Re: Latest PIOMAS update (January)
Post by: viddaloo on January 10, 2015, 12:00:24 PM
Updated collapse estimate. (chart faq (https://www.pheed.com/IceGraph/57495824/2505))

(https://d22d7v2y1t140g.cloudfront.net/m_13473120_3MKFbrus9Mju.png)
Title: Re: Latest PIOMAS update (January)
Post by: Gray-Wolf on January 10, 2015, 12:26:53 PM
So it appears the resumption in Fram exports has impacted, a little, the ranking and so I would expect this to be further 'impacted' in Jan's figure as the losses through Fram continue but also the 'normal gains' of Bering at this time of year fail to materialise?

This may be the second year in a row where we entered refreeze carrying a better load of ice only to see this decline ( in relative terms?) through Jan/Feb/March?
Title: Re: Latest PIOMAS update (January)
Post by: crandles on January 10, 2015, 01:21:57 PM
So it appears the resumption in Fram exports has impacted, a little, the ranking ...

Didn't the ranking change from 7th lowest at end of November to 8th lowest at end of December? ;)

Yes I would think most people would expect falls in ranking over the winter like 2014 and not necessarily due to Fram exports. I would suggest factors in order of importance:

1. The thicker the ice, the more slowly it grows thicker.
2. Fram export - speed and thickness seems high at least at present.
3. Low area in Bering - this might keep the volume down particularly in the near term and perhaps by continuing to keep extent down but maybe with less ice it can grow volume rapidly over late Jan Feb & Mar.
Title: Re: Latest PIOMAS update (January)
Post by: Gray-Wolf on January 10, 2015, 08:05:26 PM
Oopsie! my bad!!!
Title: Re: Latest PIOMAS update (January)
Post by: DavidR on January 11, 2015, 06:55:15 AM
So it appears the resumption in Fram exports has impacted, a little, the ranking and so I would expect this to be further 'impacted' in Jan's figure as the losses through Fram continue but also the 'normal gains' of Bering at this time of year fail to materialise?
Sea Surface temperatures in the Bering Sea have been at record warmth for the past 6 months according to NOAA, with  Jul - Nov all rated warmest and December rated second warmest.  I  doubt that we will see much ice at all there in the coming months. 
Title: Re: Latest PIOMAS update (January)
Post by: viddaloo on January 11, 2015, 10:10:19 AM
With half the decade gone, only 4 months contribute to the collapse, while 8 months do their best to resist and compensate:

(https://d22d7v2y1t140g.cloudfront.net/m_13478968_lnGXhlorZ1N7.png)

January packs 10% more volume in the 2010s than in the late 1900s.
February packs 14% more volume in the 2010s than in the late 1900s.
March packs 18% more volume in the 2010s than in the late 1900s.
April has 75% lower net refreeze volume in the 2010s than in the late 1900s.
May melts 92% more volume in the 2010s than in the late 1900s.
June melts 37% more volume in the 2010s than in the late 1900s.
July melts 14% less volume in the 2010s than in the late 1900s.
August melts 20% less volume in the 2010s than in the late 1900s.
September has 36% lower net refreeze volume in the 2010s than in the late 1900s.
October packs 17% more volume in the 2010s than in the late 1900s.
November packs 25% more volume in the 2010s than in the late 1900s.
December packs 12% more volume in the 2010s than in the late 1900s.
Title: Re: Latest PIOMAS update (January)
Post by: Neven on January 11, 2015, 11:04:09 AM
Blog post is up on ASIB: PIOMAS update January 2015 (http://neven1.typepad.com/blog/2015/01/piomas-january-2015.html).
Title: Re: Latest PIOMAS update (January)
Post by: crandles on February 06, 2015, 12:13:16 AM
Latest update 5th Feb 2015:

2015  31  20.229 very nearly 2500 km^3 more than record low
2014  31  18.935
2013  31  17.733 record low
2012  31  18.432
2011  31  17.938
2010  31  19.222
2009  31  20.397 higher than 2015
2008  31  20.210
2007  31  19.584
2006  31  20.834 higher than 2015

So 8th lowest since turn of century.

For comparison at 31 Dec record low is 31/12/12 13.921
31/12/14 was 16.845 2924 km^3 above record low.

So the gap above the record low has grown slightly from 2924 to 2996 km^3.
Title: Re: Latest PIOMAS update (February)
Post by: viddaloo on February 06, 2015, 07:23:05 AM
:
2015   1  16.927
2015   2  16.991
2015   3  17.065
2015   4  17.154
2015   5  17.247
2015   6  17.365
2015   7  17.472
2015   8  17.572
2015   9  17.655
2015  10  17.749
2015  11  17.854
2015  12  17.980
2015  13  18.113
2015  14  18.240
2015  15  18.360
2015  16  18.478
2015  17  18.593
2015  18  18.722
2015  19  18.839
2015  20  18.971
2015  21  19.095
2015  22  19.216
2015  23  19.331
2015  24  19.434
2015  25  19.540
2015  26  19.639
2015  27  19.756
2015  28  19.872
2015  29  19.981
2015  30  20.111
2015  31  20.229
Title: Re: Latest PIOMAS update (February)
Post by: Wipneus on February 06, 2015, 08:06:27 AM
Updated, graphs are in the top post.

(gridded data updated also, I will post the graphs later)
Title: Re: Latest PIOMAS update (February)
Post by: Wipneus on February 06, 2015, 10:28:49 AM
Here are thickness maps for January 2014 and 2015 as well as their difference.

(total January volume is about 1000 km3 bigger than in 2014)
Title: Re: Latest PIOMAS update (February)
Post by: Wipneus on February 06, 2015, 10:35:33 AM
And difference in growth from December to January,  red means more thickening/less thinning.

(total growth was about 3.4 [1000 km3], slightly less than the 3.6 [1000 km3] a year ago)
Title: Re: Latest PIOMAS update (February)
Post by: jdallen on February 07, 2015, 07:21:19 AM
It's all way too thin, especially considering the hot cyclones blowing up along the eastern seaboard dragging heat and moisture into the Greenland, Norwegian and Barents.

I'm pessimistic.
Title: Re: Latest PIOMAS update (February)
Post by: Jim Hunt on February 07, 2015, 11:27:55 AM
It's all way too thin

Not forgetting that CryoSat 2 reckoned (http://www.esa.int/Our_Activities/Observing_the_Earth/CryoSat/CryoSat_extends_its_reach_on_the_Arctic) the ice was thinner in Oct/Nov 2014 than in 2013.

Measurements made during October and November show that the volume of Arctic sea ice now stands at about 10 200 cubic km – a small drop compared to last year’s 10 900 cubic km

(Click the image to see a 1.5 Mb animation)
Title: Re: Latest PIOMAS update (February)
Post by: Neven on February 07, 2015, 12:23:19 PM
PIOMAS February 2015 (http://neven1.typepad.com/blog/2015/02/piomas-february-2015.html) over on the ASIB.
Title: Re: Latest PIOMAS update (February)
Post by: Jim Hunt on February 07, 2015, 12:26:03 PM
PIOMAS February 2015 (http://neven1.typepad.com/blog/2015/02/piomas-february-2015.html) over on the ASIB.

I noticed :)
Title: Re: Latest PIOMAS update (February)
Post by: Neven on February 07, 2015, 01:30:52 PM
I noticed :)

I noticed you noticed.  ;D
Title: Re: Latest PIOMAS update (January)
Post by: viddaloo on February 07, 2015, 02:49:39 PM
January has now increased its compensating support for the Arctic sea ice (up from 10%) and now shares the 'least supportive' position with December:

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fd22d7v2y1t140g.cloudfront.net%2Fm_13594297_72XtF30EJ9bU.png&hash=41772e9a0bdbc9c37966556ce910e7de)

With half the decade gone, only 4 months contribute to the collapse, while 8 months do their best to resist and compensate:

January packs 10% more volume in the 2010s than in the late 1900s.
February packs 14% more volume in the 2010s than in the late 1900s.
March packs 18% more volume in the 2010s than in the late 1900s.
April has 75% lower net refreeze volume in the 2010s than in the late 1900s.
May melts 92% more volume in the 2010s than in the late 1900s.
June melts 37% more volume in the 2010s than in the late 1900s.
July melts 14% less volume in the 2010s than in the late 1900s.
August melts 20% less volume in the 2010s than in the late 1900s.
September has 36% lower net refreeze volume in the 2010s than in the late 1900s.
October packs 17% more volume in the 2010s than in the late 1900s.
November packs 25% more volume in the 2010s than in the late 1900s.
December packs 12% more volume in the 2010s than in the late 1900s.
Title: Re: Latest PIOMAS update (February)
Post by: iceman on February 07, 2015, 03:49:28 PM

Not forgetting that CryoSat 2 reckoned (http://www.esa.int/Our_Activities/Observing_the_Earth/CryoSat/CryoSat_extends_its_reach_on_the_Arctic) the ice was thinner in Oct/Nov 2014 than in 2013.

Measurements made during October and November show that the volume of Arctic sea ice now stands at about 10 200 cubic km – a small drop compared to last year’s 10 900 cubic km
I wouldn't put too much faith in CryoSat 2 for now.  Judging from posts here a month ago, it seems that CryoSat 2 may have measured erroneously high in Oct/Nov 2013, which could yield an incorrect y/y decline in the latest readings.
Title: Re: Latest PIOMAS update (February)
Post by: Jim Hunt on February 07, 2015, 05:07:45 PM
I wouldn't put too much faith in CryoSat 2 for now

Which implies that you have a lot more faith in PIOMAS? I presume these are the comments you are referring to?

http://forum.arctic-sea-ice.net/index.php/topic,119.msg41670/topicseen.html#msg41670 (http://forum.arctic-sea-ice.net/index.php/topic,119.msg41670/topicseen.html#msg41670)
Title: Re: Latest PIOMAS update (February)
Post by: viddaloo on February 07, 2015, 10:14:49 PM
Updated collapse estimate: With the hottest year globally (sea and land surface) + the first warm month of 2015, average volume is now up 1968 km³ in 21 months. The last time we had an average volume jump of 1968 km³ or more in 21 months or less, was in 1995–97 (up 2181 km³), a La Niña event. So, to sum up; the monster volume regrowth of 2013–2015 is only matched by a 1995–97 La Nina regrowth of sea ice volume, even though 2014 was the warmest on record (in itself quite an achievement without an El Niño). When will we see a monster El Niño accompanied by a same–time monster La Niña–style ice volume regrowth? With "streamlined" (http://forum.arctic-sea-ice.net/index.php/topic,179.msg44383.html#msg44383) América del Norte–style politicised "science" it may be closer than you think!

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fd22d7v2y1t140g.cloudfront.net%2Fm_13594964_F1wQAvkXc7aj.png&hash=d7e408d2cc6e160e75d2150a03b54c8a)
[chart faq (https://www.pheed.com/IceGraph/57495824/2505)]
Title: Re: Latest PIOMAS update (February)
Post by: viddaloo on February 09, 2015, 05:14:44 PM
2014 *gained* 6th most ice during the year in the 1979–2014 PIOMAS time–series. Another way of putting this is that it 'melted' 31st most ice. By contrast, 2012 melted 8th most ice and was 9th warmest globally.

This is why I believe we may be heading for a new ice–age or a new 'Snowball Earth' scenario if the planet gets even hotter.
Title: Re: Latest PIOMAS update (February)
Post by: Bob Wallace on February 09, 2015, 05:44:47 PM
And difference in growth from December to January,  red means more thickening/less thinning.

(total growth was about 3.4 [1000 km3], slightly less than the 3.6 [1000 km3] a year ago)

The red area east of Greenland and the blue areas to the north indicate a lot of thicker ice being ejected into the Atlantic?
Title: Re: Latest PIOMAS update (February)
Post by: Wipneus on February 09, 2015, 06:08:15 PM
The ice in the Greenland Sea will melt in the near future. How fast the ice is entering via the Fram Strait cannot be said from this data alone.
Title: Re: Latest PIOMAS update (February)
Post by: Peter Ellis on February 09, 2015, 07:17:33 PM
This is why I believe we may be heading for a new ice–age or a new 'Snowball Earth' scenario if the planet gets even hotter.

Wut?  Now I'm confused.  Are you simultaneously predicting a Snowball Earth and ice-free conditions year-round?  What's the snow made of, polystyrene?
Title: Re: Latest PIOMAS update (February)
Post by: Lord M Vader on February 09, 2015, 07:22:24 PM
Wipneus: don't forget the crap ice south east of Svalbard! It should also melt out rather quickly in the near future... Another area of interest is located southwest of Alaska with fragile ice but shouldn't be subject for melting in the close future as colder air seems to merge southward..

//LMV
Title: Re: Latest PIOMAS update (February)
Post by: Michael Hauber on February 09, 2015, 10:20:37 PM
The PIOMAS anomaly chart [/quote] is quite striking with anomalies now well above the long term trend, and above the range of the darker shading (1 standard deviation?).  This fits in comfortably with a long term linear trend.  However Tamino in the past had [url=https://tamino.wordpress.com/2013/03/12/arctic-sea-ice-loss-part-1/]shown (http://neven1.typepad.com/.a/6a0133f03a1e37970b01b7c748611e970b-pi) a statistically significant acceleration and that the trend was not linear.  Some possibilities:
1.  Tamino's analysis is wrong.
3.  My gut feel assessment that a return to the upper boundaries of the typical range for a linear trend must be a significant departure from the non linear trend is wrong.
3.  A statistical fluke either caused the appearance of acceleration, or the return to above linear trend.
4.  A significant factor (i.e. something not covered by the relevant statistical test for noise) caused a temporary increase in melt and this factor has now changed.
5.  Something to do with Tamino's analysis being extent and this being volume. 
6.  Slow decline - the acceleration was real, but the trend is a gompertz curve that is now entering the deceleration phase.
Title: Re: Latest PIOMAS update (February)
Post by: Peter Ellis on February 10, 2015, 01:32:43 AM
(5) will be a huge factor.

Volume and area shouldn't be expected to follow the same pattern - at the most simplistic level, area scales with the square of linear dimensions and volume with the cube.  So, if a blob of ice melts evenly in all directions, the graph of area against volume will have y proportional to x^(2/3).  Or (3/2) depending which way round you draw your axes!

This in itself will intrinsically convert a linear decline in volume to a nonlinear, accelerating decline in area.  If you additionally assume that ice loses thickness proportionally faster than area (a fairly sensible assumption given how heat flow works in large flat sheets), then the nonlinearity becomes even more pronounced.
Title: Re: Latest PIOMAS update (February)
Post by: plinius on February 10, 2015, 02:24:03 AM
I'd add 6th: Your underlying hypothesis of homoskedasticity is wrong - we expect that due to increased positive feedbacks and reduced memory effect (less old ice there...) the variability (and probably also the autocorrelation) should go up. Hence, the statistical significance of these events is overestimated by your eye.

The PIOMAS anomaly chart  (http://neven1.typepad.com/.a/6a0133f03a1e37970b01b7c748611e970b-pi)
is quite striking with anomalies now well above the long term trend, and above the range of the darker shading (1 standard deviation?).  This fits in comfortably with a long term linear trend.  However Tamino in the past had shown (https://tamino.wordpress.com/2013/03/12/arctic-sea-ice-loss-part-1/) a statistically significant acceleration and that the trend was not linear.  Some possibilities:
1.  Tamino's analysis is wrong.
3.  My gut feel assessment that a return to the upper boundaries of the typical range for a linear trend must be a significant departure from the non linear trend is wrong.
3.  A statistical fluke either caused the appearance of acceleration, or the return to above linear trend.
4.  A significant factor (i.e. something not covered by the relevant statistical test for noise) caused a temporary increase in melt and this factor has now changed.
5.  Something to do with Tamino's analysis being extent and this being volume. 
6.  Slow decline - the acceleration was real, but the trend is a gompertz curve that is now entering the deceleration phase.
[/quote]
Title: Re: Latest PIOMAS update (February)
Post by: Michael Hauber on February 10, 2015, 03:27:29 AM
I'd add 6th: Your underlying hypothesis of homoskedasticity is wrong - we expect that due to increased positive feedbacks and reduced memory effect (less old ice there...) the variability (and probably also the autocorrelation) should go up. Hence, the statistical significance of these events is overestimated by your eye.


A very quick analysis -  I measure variability as absolute difference from one year to next in September volume.  A linear trend shows variability has reduced over time - doesn't look to be significant, but it would be no surprise to me if less ice means less variability.  Consider also with a more uniform pack dominated by 1st year ice there will be less variability due to a regional hotspot being in an area of thin and vulnerable ice vs an area of thick and resilient ice. 

Title: Re: Latest PIOMAS update (February)
Post by: Peter Ellis on February 10, 2015, 09:35:17 AM
What on Earth does the September-to-September variability tell you about mid-February?
Title: Re: Latest PIOMAS update (February)
Post by: lanevn on February 10, 2015, 10:39:10 AM
This is why I believe we may be heading for a new ice–age or a new 'Snowball Earth' scenario if the planet gets even hotter.

Several days ago you predicted record low this year.
Title: Re: Latest PIOMAS update (February)
Post by: crandles on February 10, 2015, 01:12:38 PM

5.  Something to do with Tamino's analysis being extent and this being volume. 

(5) will be a huge factor.

The Tamino article linked included
Arctic sea ice volume shows a somewhat different pattern that that of extent and area:

There are still plenty of fluctuations but they’re not as large relative to the trend as with extent or area. This may be partly because the volume data involve the output of a computer model for ice thickness. There is still strong acceleration of sea ice volume loss, and no sign of deceleration.

The article is dated March 2013 so we are less than two year past this date. While I think there is now a sign of deceleration, is less than two years data likely to be statistically significant? So I am not ruling out 2 and 3.

4. Also seems entirely possible especially as an explanation has already been discussed. We had a rapid fall in Multi year ice when MYI ceased surviving a passage around Beaufort Gyre. MYI had fallen as low as it is going to go as a result of this so the rate of decline in volume slows down. See also slow transition thread.

Above could also be considered to be causing a gompertz shape curve ie it could be considered to be no 6.

So I am tending to think a combination of a couple of things that can be described as '2 & 3' and  '4 & 6'.
Title: Re: Latest PIOMAS update (February)
Post by: Michael Hauber on February 10, 2015, 09:58:04 PM
What on Earth does the September-to-September variability tell you about mid-February?

The same analysis repeated for February gives roughly the same result.
Title: Re: Latest PIOMAS update (February)
Post by: epiphyte on February 11, 2015, 08:14:22 AM
(5) will be a huge factor.

Volume and area shouldn't be expected to follow the same pattern - at the most simplistic level, area scales with the square of linear dimensions and volume with the cube.  So, if a blob of ice melts evenly in all directions, the graph of area against volume will have y proportional to x^(2/3).  Or (3/2) depending which way round you draw your axes!

This in itself will intrinsically convert a linear decline in volume to a nonlinear, accelerating decline in area.  If you additionally assume that ice loses thickness proportionally faster than area (a fairly sensible assumption given how heat flow works in large flat sheets), then the nonlinearity becomes even more pronounced.

Sure the decline in area is nonlinear - but it all happens at the end.  If a disc of ice 1000km in diameter and 1m thick melts evenly in all directions, won't it still have an area of PI*499.495**2 ~= 783812km2 when it is uniformly 1mm thick?
Title: Re: Latest PIOMAS update (February)
Post by: Gray-Wolf on February 11, 2015, 09:17:08 AM
I get the idea that Vid was being a tad sarcastic about 'snowball earth'? The topsy turvy world of 'how much ice' and how much ice gain versus ice losses can appear a tad counter intuitive and deniers will often mess with things like 'ice gain' ,come re-freeze, after major loss years.

Some times 'more is less' and it can be a bit like that looking at every single bob and weave that some ice stats take? Maybe the 'bigger picture' is a safer view esp. over rebound years???
Title: Re: Latest PIOMAS update (February)
Post by: crandles on February 11, 2015, 12:37:26 PM
(5) will be a huge factor.

Volume and area shouldn't be expected to follow the same pattern - at the most simplistic level, area scales with the square of linear dimensions and volume with the cube.  So, if a blob of ice melts evenly in all directions, the graph of area against volume will have y proportional to x^(2/3).  Or (3/2) depending which way round you draw your axes!

This in itself will intrinsically convert a linear decline in volume to a nonlinear, accelerating decline in area.  If you additionally assume that ice loses thickness proportionally faster than area (a fairly sensible assumption given how heat flow works in large flat sheets), then the nonlinearity becomes even more pronounced.

Sure the decline in area is nonlinear - but it all happens at the end.  If a disc of ice 1000km in diameter and 1m thick melts evenly in all directions, won't it still have an area of PI*499.495**2 ~= 783812km2 when it is uniformly 1mm thick?

A more accurate view of the ice is a semicircle in area which is thickest at the centre (against Canada) and gets thinner towards the edges. This will maintain its basic shape as it melts. That is rather theoretical and in practice it may be much more complex, however, when looking at data the same ratio of area to thickness does seem to be maintained.
Title: Re: Latest PIOMAS update (February)
Post by: viddaloo on February 11, 2015, 02:52:15 PM
I get the idea that Vid was being a tad sarcastic about 'snowball earth'? The topsy turvy world of 'how much ice' and how much ice gain versus ice losses can appear a tad counter intuitive and deniers will often mess with things like 'ice gain' ,come re-freeze, after major loss years.

Some times 'more is less' and it can be a bit like that looking at every single bob and weave that some ice stats take? Maybe the 'bigger picture' is a safer view esp. over rebound years???

If I was a tabloid empire I would certainly run with the headline 'New Ice–Age in June' on the front–page, and nifty drawings of 'Snowball–Earth' in the magazine supplement. If only one record–warm year can give this much more ice Jan 1 to Jan 1, imagine what a string of 10 or 100 steadily warmer years can do?
Title: Re: Latest PIOMAS update (February)
Post by: jbatteen on February 11, 2015, 06:58:06 PM
I still can't tell if you're serious or sarcastic.
Title: Re: Latest PIOMAS update (February)
Post by: viddaloo on February 11, 2015, 07:30:07 PM
Clarification: I don't think we'll be in a new ice–age by June.
Title: Re: Latest PIOMAS update (February)
Post by: Frivolousz21 on February 13, 2015, 06:36:50 PM
any cryosat update for December or January data to compare with piomas?

They have been strikingly different the past two falls and the most recent press release the folks running cryosat claim it's 99% accurate.
Title: Re: Latest PIOMAS update (February)
Post by: viddaloo on February 13, 2015, 06:45:58 PM
Welcome back, Friv!

I've just been reading up on the melt seasons prior to my joining the forum (ie 2013 and first part of 2014 melt), and looking forward to having you on the board for the 2015 melt (http://forum.arctic-sea-ice.net/index.php/topic,1149.0.html)!
Title: Re: Latest PIOMAS update (February)
Post by: lanevn on February 13, 2015, 11:26:42 PM
They have been strikingly different the past two falls and the most recent press release the folks running cryosat claim it's 99% accurate.
Cryosat is for europeans with renewables and energy savings, piomas for americans with shale gas and etc  8)
Title: Re: Latest PIOMAS update (February)
Post by: lanevn on February 15, 2015, 01:18:57 PM
piomas for europeans with shale gas and etc  8)
Sorry, I ment "americans" ofc.
Title: Re: Latest PIOMAS update (March)
Post by: Wipneus on March 11, 2015, 06:44:57 AM
The gridded monthly data was updated, from it I calculate the average volum for February to be 21.5 [1000 km3], about 600 1600  km3 above 2014.

We will have to wait for the daily data to see if the trend after Feb 15 did change. In the mean time I will post the monthly thickness maps.
Title: Re: Latest PIOMAS update (March)
Post by: Wipneus on March 11, 2015, 06:47:59 AM
Thickness maps for February 2014 and 2015 and their difference.
Title: Re: Latest PIOMAS update (March)
Post by: Wipneus on March 11, 2015, 06:54:39 AM
And difference in growth from January to February, red means more thickening/less thinning.
Title: Re: Latest PIOMAS update (March)
Post by: OSweetMrMath on March 11, 2015, 07:22:54 AM
The gridded monthly data was updated, from it I calculate the average volum for February to be 21.5 [1000 km3]], about 600  km3] above 2014.

We will have to wait for the daily data to see if the trend after Feb 15 did change. In the mean time I will post the monthly thickness maps.

Feb. 2014 was 19.851, which makes this year 1600 cubic km above last year, unless I'm misreading something.
Title: Re: Latest PIOMAS update (March)
Post by: viddaloo on March 11, 2015, 07:31:02 AM
LOL
Title: Re: Latest PIOMAS update (March)
Post by: Wipneus on March 11, 2015, 07:33:23 AM
Feb. 2014 was 19.851, which makes this year 1600 cubic km above last year, unless I'm misreading something.

Thanks, you are absolutely right.
Title: Re: Latest PIOMAS update (March)
Post by: OSweetMrMath on March 11, 2015, 07:55:50 AM
I'll post more on this tomorrow (in my time zone) but since volume increases due to thickening even after extent and area drop, I will not be surprised if the volume doesn't show the same late February drop as the other measures. The year-over-year increase in volume has been around 1000-1500 cubic km for every month since last July, so the February volume is basically still in that range. It is still several hundred cubic km above my prediction, for what that's worth.
Title: Re: Latest PIOMAS update (March)
Post by: Nightvid Cole on March 11, 2015, 06:13:42 PM
Volume, as of March 8th according to the main PIOMAS anomaly trace graph, is virtually indistinguishable from the same time in 2010.

The distribution is different, however. Compared to 2010, much more of the volume is in the thick band of ice off Greenland and the CAA. The ice in the central Arctic Ocean, away from any of the land masses, is thinner than 2010. Based on the map the modal thickness is roughly 25cm thinner than at the same time in 2010.

This means it is more likely that we will see the September extent go really low this year, though it of course depends on the weather.
Title: Re: Latest PIOMAS update (March)
Post by: Wipneus on March 11, 2015, 06:46:33 PM
PIOMASA daily data is updated now, see the graphs in the top post.
Title: Re: Latest PIOMAS update (March)
Post by: viddaloo on March 11, 2015, 07:25:20 PM
:
2015  32  20.348
2015  33  20.452
2015  34  20.542
2015  35  20.629
2015  36  20.699
2015  37  20.754
2015  38  20.812
2015  39  20.890
2015  40  20.991
2015  41  21.094
2015  42  21.199
2015  43  21.312
2015  44  21.448
2015  45  21.571
2015  46  21.680
2015  47  21.768
2015  48  21.803
2015  49  21.838
2015  50  21.897
2015  51  21.973
2015  52  22.042
2015  53  22.132
2015  54  22.235
2015  55  22.303
2015  56  22.355
2015  57  22.389
2015  58  22.434
2015  59  22.472
2015  60  22.524
2015  61  22.580
2015  62  22.623
2015  63  22.682
2015  64  22.731
2015  65  22.779
2015  66  22.808
2015  67  22.813
Title: Re: Latest PIOMAS update (March)
Post by: viddaloo on April 02, 2015, 08:10:38 AM
Guessing the 2015 yearly Piomas ice volume maximum happened in March. My fake–piomas algorithm seems to suggest as much:

:
2015 79  23.801
2015 80  23.943
2015 81  24.135
2015 82  24.261
2015 83  24.329
2015 84  24.423
2015 85  24.513
2015 86  24.473
2015 87  24.368
2015 88  24.309
2015 89  24.284
2015 90  24.267
2015 91  24.289

If so, this of course implies Piomas Minus 1000 would have a maximum volume of about 23,500 km³. Such a maximum would also be the earliest Piomas max by about a week.
Title: Re: Latest PIOMAS update (April)
Post by: Wipneus on April 04, 2015, 09:21:34 AM
Updated, graphs are in the top post.

(gridded data updated also, I will post the graphs later)
Title: Re: Latest PIOMAS update (April)
Post by: Wipneus on April 04, 2015, 09:29:09 AM
Here are thickness maps for March 2014 and 2015 as well as their difference.

Title: Re: Latest PIOMAS update (April)
Post by: Wipneus on April 04, 2015, 09:30:23 AM
And difference in growth from February to March,  red means more thickening/less thinning.
Title: Re: Latest PIOMAS update (April)
Post by: crandles on April 04, 2015, 12:31:31 PM
2015  60  22.524
2015  61  22.580
2015  62  22.623
2015  63  22.682
2015  64  22.731
2015  65  22.779
2015  66  22.809
2015  67  22.814
2015  68  22.851
2015  69  22.872
2015  70  22.938
2015  71  22.990
2015  72  23.039
2015  73  23.090
2015  74  23.140
2015  75  23.160
2015  76  23.177
2015  77  23.216
2015  78  23.284
2015  79  23.365
2015  80  23.456
2015  81  23.536
2015  82  23.610
2015  83  23.683
2015  84  23.756
2015  85  23.826
2015  86  23.878
2015  87  23.924
2015  88  23.963
2015  89  23.998
2015  90  24.036

2014  90  22.639
2013  90  22.850
2012  90  22.889
2011  90  22.129
2010  90  24.053
2009  90  24.613
2008  90  24.698
2007  90  23.711
2006  90  24.860
2005  90  25.760

Of these years fairly steady downward movement with exception of 2007 being unusually low and this year being unusually high - only 6th lowest for date and close enough to 2010 to call it =6th.

So perhaps we should expect poor melt season?
Title: Re: Latest PIOMAS update (April)
Post by: Neven on April 04, 2015, 12:37:36 PM
Thanks for the heads up, Wip. I'll have a blog post up later today.
Title: Re: Latest PIOMAS update (April)
Post by: jdallen on April 04, 2015, 07:48:11 PM

Of these years fairly steady downward movement with exception of 2007 being unusually low and this year being unusually high - only 6th lowest for date and close enough to 2010 to call it =6th.

So perhaps we should expect poor melt season?

Quite within the realm of possibility.  A poor melt season would keep the minimum within the general envelope of 2013 and 2014.  Considering a poor (Really Poor - Under 9.5 million KM2 of retreat - 2014 retreated 9.75...) melt season would still put us close to 5 million KM2, that's still not particularly good news.

All hinges on the weather. 

Edit - DavidR has some nice graphs showing annual losses.  The 2000-2014 one provides a pretty good preview.  The discussion on his new thread has the potential to be interesting as well.

http://forum.arctic-sea-ice.net/index.php/topic,1211.msg49401.html#msg49401 (http://forum.arctic-sea-ice.net/index.php/topic,1211.msg49401.html#msg49401)
Title: Re: Latest PIOMAS update (April)
Post by: Nightvid Cole on April 04, 2015, 09:32:43 PM

Of these years fairly steady downward movement with exception of 2007 being unusually low and this year being unusually high - only 6th lowest for date and close enough to 2010 to call it =6th.

So perhaps we should expect poor melt season?

Quite within the realm of possibility.  A poor melt season would keep the minimum within the general envelope of 2013 and 2014.  Considering a poor (Really Poor - Under 9.5 million KM2 of retreat - 2014 retreated 9.75...) melt season would still put us close to 5 million KM2, that's still not particularly good news.

All hinges on the weather. 

Edit - DavidR has some nice graphs showing annual losses.  The 2000-2014 one provides a pretty good preview.  The discussion on his new thread has the potential to be interesting as well.

http://forum.arctic-sea-ice.net/index.php/topic,1211.msg49401.html#msg49401 (http://forum.arctic-sea-ice.net/index.php/topic,1211.msg49401.html#msg49401)

As I've said before, I don't think 2-dimensional measures at this time of year are remotely relevant to what ice will be there in September.
Title: Re: Latest PIOMAS update (April)
Post by: jdallen on April 05, 2015, 08:42:48 AM
As I've said before, I don't think 2-dimensional measures at this time of year are remotely relevant to what ice will be there in September.
How to frame this... the state of the ice *currently* is not specifically predictive of the state it will be in in September - I generally agree.

However - Median ice loss between max and min since 2000 is about 9.9 million KM2.
Average is about 10.1

So by extension, we statistically are looking at a minimum extent of just over 4 million KM2.

That puts us very close, if not slightly below 2007.

It will require a *very* favorable melt season to keep us above that.

If we have a "bad" melt season (e.g. similar to 2012), it's quite likely we could see a minimum well under 3 million KM2.  Statistics do not favor a good year.  Neither (and more importantly) does the weather.
Title: Re: Latest PIOMAS update (April)
Post by: Nightvid Cole on April 05, 2015, 07:00:37 PM
As I've said before, I don't think 2-dimensional measures at this time of year are remotely relevant to what ice will be there in September.
How to frame this... the state of the ice *currently* is not specifically predictive of the state it will be in in September - I generally agree.

However - Median ice loss between max and min since 2000 is about 9.9 million KM2.
Average is about 10.1

So by extension, we statistically are looking at a minimum extent of just over 4 million KM2.

That puts us very close, if not slightly below 2007.

It will require a *very* favorable melt season to keep us above that.

If we have a "bad" melt season (e.g. similar to 2012), it's quite likely we could see a minimum well under 3 million KM2.  Statistics do not favor a good year.  Neither (and more importantly) does the weather.

You are contradicting yourself. Using differences between max and min to infer min IS THE SAME THING as inferring min from max!

For that matter, I could just as well argue that on average the minimum ice extent is 10 Trillion times the mean body surface area of patients admitted to St. Jude Hospital in March of that year, and since this year had a record low (due to fewer obese patients), it is unlikely the ice won't be close to a record low. Seems silly, right? But as long as max and min extent are uncorrelated to each other (at least after detrending), you're basically doing the same thing.
Title: Re: Latest PIOMAS update (April)
Post by: jdallen on April 06, 2015, 06:41:35 AM
As I've said before, I don't think 2-dimensional measures at this time of year are remotely relevant to what ice will be there in September.
How to frame this... the state of the ice *currently* is not specifically predictive of the state it will be in in September - I generally agree.
You are contradicting yourself. Using differences between max and min to infer min IS THE SAME THING as inferring min from max!

I disagree.  I'm not using the max to infer the eventual min.  I'm using the loss of ice extent to infer a possible range of minimum values, not a specific one.

By doing that I'm looking at two very broad variables.  First is the total uptake of heat, as identifiable by changes in ice coverage and ocean temperature.  The second is weather, as expressed in the same loss of ice.

So no, I can't infer a specific minimum.  I can infer from recent behavior a predictable loss of extent.  *That* has been reasonably consistent at just under 10 million KM2. 

However, the sample is fairly small, and has some pretty serious outliers (8.5 million and 12 million), so the chance exists for minima that reflect those losses.  That said, they *are* 2 sigma results.  most actually favor my base assumption of just under 10 million KM2.

We'll see how the season plays out.
Title: Re: Latest PIOMAS update (April)
Post by: jdallen on April 06, 2015, 07:45:46 AM
To amplify my earlier post, here's SIA numbers (thank you Jim Pettit)

SIA   Maximum   Minimum   Loss
2014   13487337   3483168   10004169
2013   13799198   3444397   10354801
2012   13708510   2234010   11474500
2011   13144420   2904740   10239680
2010   13812038   2904740   10907298
2009   13812038   3424598   10387440
2008   13890715   3003556   10887159
2007   13317198   2919438   10397760
2006   13358222   4016919   9341303
2005   13460056   4091798   9368258
2004   13775685   4282973   9492712
2003   14339062   4141665   10197397
2002   14322480   4034710   10287770
2001   14526312   4533619   9992693
2000   13918529   4168766   9749763
1999   14295398   4204499   10090899
1998   14541186   4262403   10278783
1997   14332573   4899706   9432867
1996   13843270   5238185   8605085
1995   14274362   4410301   9864061
1994   14527855   4816096   9711759
1993   14755034   4472953   10282081
1992   14398718   5026778   9371940
1991   14222953   4460384   9762569
1990   14688305   4628935   10059370
1989   14183708   4815916   9367792
1988   15007110   5144891   9862219
1987   14682733   5288995   9393738
1986   14487026   5381843   9105183
1985   14594806   4992847   9601959
1984   14262281   4695892   9566389
1983   14773425   4386929   10386496
1982   14773425   5139060   9634365
1981   14308250   5507712   8800538
1980   14742998   5507712   9235286
1979   15074604   5306726   9767878

      Average   9868443
      Median   9815049
      StdDev   590653
      +2SD   11049750
      -2SD    8687137

Post 1999   Average   10205514
      Median   10239680
      StdDev   592651
      +2SD   11390816
      -2SD    9020211
Title: Re: Latest PIOMAS update (April)
Post by: jdallen on April 06, 2015, 08:25:44 AM
So, from this consider the probable outcome for 2015.

If we have a sea ice loss which is "average", what would the minimum look like?

Applying the 1979-2014 average we get a max of 13.27 million KM2. (values in millions of KM2)


                      Using 1979-2014 stats      Using 2000-2014 stats
From Average   3.40                               3.06
From Median     3.45                               3.03
+2SD              2.22                                1.88
-2SD               4.58                                4.25

It's a big range, but its also pretty easy to see that given relatively normal melt, the ice coverage is quite likely to flirt with the lowest of years we've seen.

Even a "cool" melt year still keeps us generally within what we saw in 2013 and 2014.
Title: Re: Latest PIOMAS update (April)
Post by: Vergent on April 06, 2015, 09:54:08 AM
jdallen,

Sorry for coming out of hibernation, but PIOMAS volume units are Km^3, and they are kilo, not mega. You are off by a factor of 1,000. This makes it difficult to take you seriously.

 Verg
Title: Re: Latest PIOMAS update (April)
Post by: Neven on April 06, 2015, 11:21:57 AM
I think jdallen was referring to Cryosphere Today sea ice area numbers, which, I admit, is a bit confusing in the PIOMAS thread.  :)
Title: Re: Latest PIOMAS update (April)
Post by: Nightvid Cole on April 06, 2015, 04:27:19 PM
As I've said before, I don't think 2-dimensional measures at this time of year are remotely relevant to what ice will be there in September.
How to frame this... the state of the ice *currently* is not specifically predictive of the state it will be in in September - I generally agree.
You are contradicting yourself. Using differences between max and min to infer min IS THE SAME THING as inferring min from max!

I disagree.  I'm not using the max to infer the eventual min.  I'm using the loss of ice extent to infer a possible range of minimum values, not a specific one.

By doing that I'm looking at two very broad variables.  First is the total uptake of heat, as identifiable by changes in ice coverage and ocean temperature.  The second is weather, as expressed in the same loss of ice.

So no, I can't infer a specific minimum.  I can infer from recent behavior a predictable loss of extent.  *That* has been reasonably consistent at just under 10 million KM2. 

However, the sample is fairly small, and has some pretty serious outliers (8.5 million and 12 million), so the chance exists for minima that reflect those losses.  That said, they *are* 2 sigma results.  most actually favor my base assumption of just under 10 million KM2.

We'll see how the season plays out.

You're splitting hairs. Your technique still uses the max to infer the min, to within some range of uncertainty. Is that better?
Title: Re: Latest PIOMAS update (April)
Post by: jdallen on April 06, 2015, 04:54:56 PM
I think jdallen was referring to Cryosphere Today sea ice area numbers, which, I admit, is a bit confusing in the PIOMAS thread.  :)

Oops :)  Sorry.  I can re-work it with PIOMAS :))
Title: Re: Latest PIOMAS update (April)
Post by: oren on April 07, 2015, 02:46:37 PM
So, from this consider the probable outcome for 2015.

If we have a sea ice loss which is "average", what would the minimum look like?

Applying the 1979-2014 average we get a max of 13.27 million KM2. (values in millions of KM2)


                      Using 1979-2014 stats      Using 2000-2014 stats
From Average   3.40                               3.06
From Median     3.45                               3.03
+2SD              2.22                                1.88
-2SD               4.58                                4.25

It's a big range, but its also pretty easy to see that given relatively normal melt, the ice coverage is quite likely to flirt with the lowest of years we've seen.

Even a "cool" melt year still keeps us generally within what we saw in 2013 and 2014.

I believe the possible problem with such a calculation is that loss might be slightly correlated to max extent, meaning that in high max years more ice is lost than low max years, which in turn causes the low correlation of the min to the max even though losses are fairly grouped together.
In the real world, if the Sea of Okhotsk is full of ice and this causes high max extent, when it melts out the loss will be high, and vice versa, buit the min extent (driven by CAB and CAA and whatever) will still be the same.
I haven't done the calculation to check this, my math skills are rusty.
Title: Re: Latest PIOMAS update (April)
Post by: DavidR on April 07, 2015, 03:00:07 PM
I believe the possible problem with such a calculation is that loss might be slightly correlated to max extent, meaning that in high max years more ice is lost than low max years, which in turn causes the low correlation of the min to the max even though losses are fairly grouped together.
In the real world, if the Sea of Okhotsk is full of ice and this causes high max extent, when it melts out the loss will be high, and vice versa, buit the min extent (driven by CAB and CAA and whatever) will still be the same.
I haven't done the calculation to check this, my math skills are rusty.
Oren see the thread I  started on the Plateau  hypothesis which suggests exactly the reverse of your thoughts.
Title: Re: Latest PIOMAS update (April)
Post by: jdallen on April 07, 2015, 04:23:50 PM
I believe the possible problem with such a calculation is that loss might be slightly correlated to max extent, meaning that in high max years more ice is lost than low max years, which in turn causes the low correlation of the min to the max even though losses are fairly grouped together.
In the real world, if the Sea of Okhotsk is full of ice and this causes high max extent, when it melts out the loss will be high, and vice versa, buit the min extent (driven by CAB and CAA and whatever) will still be the same.
I haven't done the calculation to check this, my math skills are rusty.
Oren see the thread I  started on the Plateau  hypothesis which suggests exactly the reverse of your thoughts.
Still not an unreasonable criticism.  I started tinkering with the PIOMAS volume data, and found the variability - about 1000KM3 - probably too high to be useful for prediction; not much more it seemed than saying the Arctic will melt a lot in summer, and freeze a lot in fall. I'll post what I have later. Perhaps one of you can imagine more utility than my meager skills do.
Title: Re: Latest PIOMAS update (April)
Post by: Wipneus on May 05, 2015, 09:25:31 AM
PIOMAS gridded data was updated (still waiting for the main daily data and graphs).

Here are the maps with monthly average thickness of April 2014, 2015 as well as the difference.
Title: Re: Latest PIOMAS update (April)
Post by: Wipneus on May 05, 2015, 09:28:08 AM
And difference in growth from March to April,  red means more thickening/less thinning.
Title: Re: Latest PIOMAS update (April)
Post by: seaicesailor on May 05, 2015, 11:50:41 AM
PIOMAS shows thickening north of Alaska, right where NSIDC shows substantial loss of concentration. Can this be congruent or one contradicts each other? I'd say loss of concentration must reduce average thickness (unless transport brought very thick ice up there)
Title: Re: Latest PIOMAS update (April)
Post by: Jim Hunt on May 05, 2015, 12:04:24 PM
PIOMAS shows thickening north of Alaska, right where NSIDC shows substantial loss of concentration.

If you check the Radarsat (http://forum.arctic-sea-ice.net/index.php/topic,1149.msg51224.html#msg51224) images (http://forum.arctic-sea-ice.net/index.php/topic,1149.msg47797.html#msg47797) on the 2015 melt thread you can see that older ice has indeed moved into the vicinity of Point Barrow over the last few weeks:

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fforum.arctic-sea-ice.net%2Findex.php%3Faction%3Ddlattach%3Btopic%3D1149.0%3Battach%3D15959%3Bimage&hash=a00380be8fb2a1cfc630d8bb99fa2cea)

 
Title: Re: Latest PIOMAS update (April)
Post by: jdallen on May 05, 2015, 05:06:59 PM
PIOMAS gridded data was updated (still waiting for the main daily data and graphs).

Here are the maps with monthly average thickness of April 2014, 2015 as well as the difference.

Encouraging, but perhaps that is illusory hope. 

For example at the same time as I see improved thickness in say, the CAA, I note the area where the tragic loss of two dutch explorers occurred shows a thickness of over two meters.

I suspect the conditions have become so granular, areas of thick and thin ice have become so small and intermixed, that its beyond the ability of the sensors to resolve properly. 

River ice might be a good metaphor.  During breakup, it might actually be thicker than when it was static, but it certainly isn't in better shape, nor safe to cross....
Title: Re: Latest PIOMAS update (April)
Post by: Greenbelt on May 05, 2015, 05:38:31 PM
I was wondering about ice conditions in the areas with highest reported thickness when I saw the report about the researchers who had died in that area, and the description of "open water and poor ice conditions."

http://forum.arctic-sea-ice.net/index.php/topic,1247.0.html (http://forum.arctic-sea-ice.net/index.php/topic,1247.0.html)

http://www.nunatsiaqonline.ca/stories/article/65674two_dutch_researchers_presumed_drowned_in_nunavut/ (http://www.nunatsiaqonline.ca/stories/article/65674two_dutch_researchers_presumed_drowned_in_nunavut/)
Title: Re: Latest PIOMAS update (April)
Post by: crandles on May 05, 2015, 07:16:15 PM
(still waiting for the main daily data and graphs).

2015  91  24.059
2015  92  24.084
2015  93  24.118
2015  94  24.150
2015  95  24.182
2015  96  24.201
2015  97  24.232
2015  98  24.248
2015  99  24.261
2015 100  24.275
2015 101  24.277
2015 102  24.295
2015 103  24.289
2015 104  24.277
2015 105  24.266
2015 106  24.281
2015 107  24.306
2015 108  24.332
2015 109  24.358
2015 110  24.377
2015 111  24.388
2015 112  24.354
2015 113  24.307
2015 114  24.273
2015 115  24.205
2015 116  24.168
2015 117  24.136
2015 118  24.107
2015 119  24.078
2015 120  24.066
Title: Re: Latest PIOMAS update (April)
Post by: jai mitchell on May 05, 2015, 11:28:27 PM
for an average monthly value of 24.231  Which places the April value back below the 2010 high point.   (March was slightly above the 2010 value)

It looks like the early minimum did impact the volume values somewhat.
Title: Re: Latest PIOMAS update (April)
Post by: crandles on May 05, 2015, 11:50:26 PM
Year 2015 2010
Mar 23.236 23.121
Apr 24.232 24.103

Looks to me like 2015 had more volume than 2010 in Mar and Apr averages, but I could easily have done something stupid.
Title: Re: Latest PIOMAS update (April)
Post by: jdallen on May 06, 2015, 12:53:32 AM
Year 2015 2010
Mar 23.236 23.121
Apr 24.232 24.103

Looks to me like 2015 had more volume than 2010 in Mar and Apr averages, but I could easily have done something stupid.
Not sure.

I will say that when considered in context to the measurements confidence ranges, are statistically equivalent.  "Higher" or "lower" with such small differences are almost meaningless adjectives.
Title: Re: Latest PIOMAS update (April)
Post by: jai mitchell on May 06, 2015, 02:08:17 AM
indeed,

according to http://psc.apl.uw.edu/wordpress/wp-content/uploads/schweiger/ice_volume/PIOMAS.2sst.monthly.Current.v2.1.txt (http://psc.apl.uw.edu/wordpress/wp-content/uploads/schweiger/ice_volume/PIOMAS.2sst.monthly.Current.v2.1.txt)

March 2010 = 23.082
March 2015 = 23.206
Delta = .124

April 2010 = 24.097
April 2015 = 24.222
Delta = .125

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fs17.postimg.org%2Fhr3sfitz3%2Fpiomas2015.jpg&hash=cd82e9ea12a345d2b62b0054ad9800d9)

Thats what I get for eyeballing a trendline. . .  ::)
Title: Re: Latest PIOMAS update (May)
Post by: Wipneus on May 06, 2015, 08:35:22 AM
(still waiting for the main daily data and graphs).

2015  91  24.059
...
2015 120  24.066

Indeed, everything has been updated now, including the subject line of this thread.
Title: Re: Latest PIOMAS update (June)
Post by: Wipneus on June 04, 2015, 07:43:23 AM
Updated, graphs are in the top post.

(gridded data updated also, I will post the graphs later)
Title: Re: Latest PIOMAS update (June)
Post by: Wipneus on June 04, 2015, 07:49:27 AM
Here are the maps with monthly average thickness of May 2014, 2015 as well as the difference.
Title: Re: Latest PIOMAS update (June)
Post by: Wipneus on June 04, 2015, 07:51:05 AM
And difference in growth from April to May,  red means more thickening/less thinning.

Title: Re: Latest PIOMAS update (June)
Post by: seaicesailor on June 04, 2015, 09:12:50 AM
So ESS is thick as hell.
 
Title: Re: Latest PIOMAS update (June)
Post by: Jim Hunt on June 04, 2015, 10:27:23 AM
So ESS is thick as hell.

Except that MODIS reveal this:

http://GreatWhiteCon.info/resources/arctic-sea-ice-images/summer-2015-images/#ESS (http://GreatWhiteCon.info/resources/arctic-sea-ice-images/summer-2015-images/#ESS)

Title: Re: Latest PIOMAS update (June)
Post by: Yuha on June 04, 2015, 11:01:57 AM
So ESS is thick as hell.

Except that MODIS reveal this:

Remember that it is not the end of May thickness but the average thickness for the whole of May.
Title: Re: Latest PIOMAS update (June)
Post by: Neven on June 04, 2015, 11:16:16 AM
Thanks for the graphs and maps, Wipneus. I've used a couple for the PIOMAS 2015 June (http://neven1.typepad.com/blog/2015/06/piomas-june-2015.html) update over on the ASIB.
Title: Re: Latest PIOMAS update (June)
Post by: Wipneus on June 04, 2015, 11:22:39 AM
So ESS is thick as hell.

Except that MODIS reveal this:

Remember that it is not the end of May thickness but the average thickness for the whole of May.


Indeed that is not fair, here is the last day available, 31th of May.
Title: Re: Latest PIOMAS update (June)
Post by: Wipneus on June 04, 2015, 11:56:09 AM
animated.
Title: Re: Latest PIOMAS update (June)
Post by: oren on June 04, 2015, 12:35:00 PM
Just as things get going nicely, it stops...
Title: Re: Latest PIOMAS update (June)
Post by: Jim Hunt on June 05, 2015, 11:36:08 AM
Here is the last day available, 31th of May.

Can you easily do an Arctic wide version for May 31st?
Title: Re: Latest PIOMAS update (June)
Post by: Wipneus on June 05, 2015, 04:30:38 PM
Here is the last day available, 31th of May.

Can you easily do an Arctic wide version for May 31st?

Yes.

Colored the land in "tomato3" (R speak). I hope that alerts you these are from the daily data, not the usual monthly files. Give it a click of course.
Title: Re: Latest PIOMAS update (June)
Post by: Jim Hunt on June 05, 2015, 04:53:25 PM
Yes. Colored the land in "tomato3" (R speak). I hope that alerts you these are from the daily data, not the usual monthly files.

Thanks very much Wipneus. I clicked it eventually!
Title: Re: Latest PIOMAS update (June)
Post by: jai mitchell on June 06, 2015, 12:02:47 AM
what is the May monthly average value?
Title: Re: Latest PIOMAS update (June)
Post by: plinius on June 06, 2015, 03:55:48 PM
well, had PIOMAS not pathetically walled access to their data, one could tell instantly...

Apart from that, why should one care at that level? There is cryosat and given the divergence of last year's PIOMAS values versus cryosat volume, I would tend to stick with the latter...
Title: Re: Latest PIOMAS update (June)
Post by: OSweetMrMath on June 07, 2015, 07:14:36 AM
well, had PIOMAS not pathetically walled access to their data, one could tell instantly...

In what way has PIOMAS walled access to their data? It all appears to be downloadable from the usual location.

On the other hand, it doesn't look like the data file for the monthly average has been updated. Not the first time this has happened. I think Wipneus calculates a monthly average from the daily average for the graphs. Eyeballing puts the May average volume at about 23.0 thousand cubic km.
Title: Re: Latest PIOMAS update (June)
Post by: Neven on June 07, 2015, 12:04:04 PM
well, had PIOMAS not pathetically walled access to their data, one could tell instantly...

Let's not go there. The people from the PSC are extremely responsive and willing to share data, but they're working on other stuff too. You know, doing science etc. I don't think it's their top priority to have everything available real-time for a handful of interested amateurs. And it shouldn't be.

Ask them (or some of us here) if you need anything.
Title: Re: Latest PIOMAS update (June)
Post by: ChrisReynolds on June 07, 2015, 12:28:33 PM
well, had PIOMAS not pathetically walled access to their data, one could tell instantly...

Apart from that, why should one care at that level? There is cryosat and given the divergence of last year's PIOMAS values versus cryosat volume, I would tend to stick with the latter...

Puzzled...

Cryosat makes assumption of snow depth, if that assumption is wrong then Cryosat is wrong.
Title: Re: Latest PIOMAS update (June)
Post by: jai mitchell on June 07, 2015, 01:47:35 PM
well, had PIOMAS not pathetically walled access to their data, one could tell instantly...

In what way has PIOMAS walled access to their data? It all appears to be downloadable from the usual location.

On the other hand, it doesn't look like the data file for the monthly average has been updated. Not the first time this has happened. I think Wipneus calculates a monthly average from the daily average for the graphs. Eyeballing puts the May average volume at about 23.0 thousand cubic km.

that is what I got too, but For some reason it seems high to me. . .
Title: Re: Latest PIOMAS update (June)
Post by: jai mitchell on June 07, 2015, 01:55:00 PM
on a similar and slightly related note:

May snow cover anomalies are updated

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fs14.postimg.org%2Fiwrwclenl%2Fmaysnow.jpg&hash=4358478c164ef7f7c108f3977adfa6f2)

here is the map, look at Alaska!

 :o

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fs18.postimg.org%2Fp4vb64p95%2Fmaysnowmap.jpg&hash=1bf15304c131bb67712e3c6b9b5e9ab5)

Rutgers Snow lab
http://climate.rutgers.edu/snowcover/chart_vis.php?ui_year=2015&ui_month=5&ui_set=2 (http://climate.rutgers.edu/snowcover/chart_vis.php?ui_year=2015&ui_month=5&ui_set=2)
Title: Re: Latest PIOMAS update (June)
Post by: ChrisReynolds on June 07, 2015, 09:07:30 PM
Right, now I see what you all mean, Jinlun has forgotten to update the monthly data, as has been noted it has happened before. I will email him tomorrow.

Not a problem right now though. For 1979 to 2014 the RMS error of my volume calculations based on gridded data vs the monthly PIOMAS figures for May is 96ppm.

I calculate May average volume as 23.019k km^3, call it 23.02k km^3 (+/- 1 digit). OSMM is correct in his guesstimate.
Title: Re: Latest PIOMAS update (June)
Post by: jdallen on June 07, 2015, 09:14:09 PM
on a similar and slightly related note:

May snow cover anomalies are updated

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fs14.postimg.org%2Fiwrwclenl%2Fmaysnow.jpg&hash=4358478c164ef7f7c108f3977adfa6f2)

here is the map, look at Alaska!

 :o

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fs18.postimg.org%2Fp4vb64p95%2Fmaysnowmap.jpg&hash=1bf15304c131bb67712e3c6b9b5e9ab5)

Rutgers Snow lab
http://climate.rutgers.edu/snowcover/chart_vis.php?ui_year=2015&ui_month=5&ui_set=2 (http://climate.rutgers.edu/snowcover/chart_vis.php?ui_year=2015&ui_month=5&ui_set=2)

This suggests huge region-wide drops in Albedo well before we enter the teeth of the melt season.  It suggests the streaming of heat and moisture into the arctic basin proper will not be letting up.
Title: Re: Latest PIOMAS update (June)
Post by: plinius on June 07, 2015, 11:55:51 PM
@OSweet: Mea culpa. I had the habit of using the parent directory:
http://psc.apl.washington.edu/wordpress/wp-content/uploads/schweiger/ice_volume/ (http://psc.apl.washington.edu/wordpress/wp-content/uploads/schweiger/ice_volume/)

To get to the data, which is walled now. Number two is the introduction of the email query, which actually makes a link pop up, but I needed your unhappy response to actually find it, as it is tiny and nearly invisible in my browsers. Must say, I looked a long time for the data and then (mistakenly) gave up.

@ChrisReynolds: You should be careful about snow cover and cryosat, taking all blame on the data. As snow cover affects PIOMAS in a similar direction (insulating the ice from heat losses), an underestimate of snow cover will lead to overestimated ice volumes in PIOMAS, or am I mistaken?
Title: Re: Latest PIOMAS update (June)
Post by: anotheramethyst on June 08, 2015, 09:47:40 AM
on a similar and slightly related note:

May snow cover anomalies are updated

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fs14.postimg.org%2Fiwrwclenl%2Fmaysnow.jpg&hash=4358478c164ef7f7c108f3977adfa6f2)

here is the map, look at Alaska!

 :o

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fs18.postimg.org%2Fp4vb64p95%2Fmaysnowmap.jpg&hash=1bf15304c131bb67712e3c6b9b5e9ab5)

Rutgers Snow lab
http://climate.rutgers.edu/snowcover/chart_vis.php?ui_year=2015&ui_month=5&ui_set=2 (http://climate.rutgers.edu/snowcover/chart_vis.php?ui_year=2015&ui_month=5&ui_set=2)

stupid question:
is the snow anomaly in alaska lack of precipitation, possibly related to that california drought?  or did it melt early?  (or some combination of the 2...)
Title: Re: Latest PIOMAS update (June)
Post by: Siffy on June 08, 2015, 11:32:32 AM
on a similar and slightly related note:

May snow cover anomalies are updated

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fs14.postimg.org%2Fiwrwclenl%2Fmaysnow.jpg&hash=4358478c164ef7f7c108f3977adfa6f2)

here is the map, look at Alaska!

 :o

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fs18.postimg.org%2Fp4vb64p95%2Fmaysnowmap.jpg&hash=1bf15304c131bb67712e3c6b9b5e9ab5)

Rutgers Snow lab
http://climate.rutgers.edu/snowcover/chart_vis.php?ui_year=2015&ui_month=5&ui_set=2 (http://climate.rutgers.edu/snowcover/chart_vis.php?ui_year=2015&ui_month=5&ui_set=2)

stupid question:
is the snow anomaly in alaska lack of precipitation, possibly related to that california drought?  or did it melt early?  (or some combination of the 2...)

Early melt, for a large part of May abnormally hot weather kept the place anywhere from 10-20C above base line average as per GFS. This torched much of the snow cover.
Title: Re: Latest PIOMAS update (June)
Post by: Jim Hunt on June 08, 2015, 12:43:20 PM
You should be careful about snow cover and cryosat, taking all blame on the data.

The latest NASA IceBridge/CryoSat results for March have been published. More background at:

http://forum.arctic-sea-ice.net/index.php/topic,1149.msg53595.html#msg53595 (http://forum.arctic-sea-ice.net/index.php/topic,1149.msg53595.html#msg53595)

but here's the maps again:

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fforum.arctic-sea-ice.net%2Findex.php%3Faction%3Ddlattach%3Btopic%3D1149.0%3Battach%3D16985%3Bimage&hash=98a4797439dd3c2e94e140c48fc62d1c)

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fforum.arctic-sea-ice.net%2Findex.php%3Faction%3Ddlattach%3Btopic%3D1149.0%3Battach%3D16986%3Bimage&hash=fb27b56b737126a34d940b13e0db4fdf)
Title: Re: Latest PIOMAS update (June)
Post by: ChrisReynolds on June 08, 2015, 06:48:07 PM
@ChrisReynolds: You should be careful about snow cover and cryosat, taking all blame on the data. As snow cover affects PIOMAS in a similar direction (insulating the ice from heat losses), an underestimate of snow cover will lead to overestimated ice volumes in PIOMAS, or am I mistaken?

What I am saying is that many people make the mistake of seeing Cryosat as inherently superior to a reanalysis like PIOMAS or NAME. Cryosat is not inherently superior because it suffers from the same issue of uncertainty over snow depth and distribution.
Title: Re: Latest PIOMAS update (June)
Post by: quanitlaq on June 08, 2015, 07:04:34 PM

stupid question:
is the snow anomaly in alaska lack of precipitation, possibly related to that california drought?  or did it melt early?  (or some combination of the 2...)
[/quote]

Early melt, for a large part of May abnormally hot weather kept the place anywhere from 10-20C above base line average as per GFS. This torched much of the snow cover.
[/quote]

Alaska had a warm winter and low snow year plus a warm May - so likely a combination of the 2. Many of us in Alaska that like snow blamed Boston for stealing it, but scientists are pointing to the warm "blob" in the eastern North Pacific, which has also been implicated for the California drought to some degree.
Title: Re: Latest PIOMAS update (June)
Post by: Vergent on June 08, 2015, 09:43:01 PM
Wipneus or Chris,

Could you do May 2015 - 2012 ice thickness and snow thickness? ("-" = minus)

Thanks

Verg
Title: Re: Latest PIOMAS update (June)
Post by: ChrisReynolds on June 08, 2015, 11:31:54 PM
Vergent,

Map or regional volume?

Wipneus may be the best bet for a map, since I re-wrote my code to tidy up, difference maps would need a total rewrite to get them running (it's complicated..). But regional figures I can do.

Volume and thickness, for May average, difference between 2012 and 2015 = 2015 - 2012.
Also for context 2012 volume for May and the percent change.

Volume in km^3.
   Difference / 2012 Vol / %  Change
Other   0.0   0.0   0.00%
Okhotsk   -42.2   108.2   -39.03%
Bering   -221.7   261.3   -84.84%
Beaufort   -257.9   1098.1   -23.49%
Chukchi   -238.0   1394.9   -17.06%
ESS   -149.2   2032.3   -7.34%
Laptev   -0.6   1049.1   -0.06%
Kara   242.4   624.5   38.82%
Barents   176.0   193.2   91.13%
Greenland   -62.0   650.4   -9.53%
Central   1535.1   10557.6   14.54%
CAA   54.0   1473.8   3.67%
Baffin   184.3   962.3   19.15%
Hudson   83.6   1309.0   6.39%
All   1303.9   21714.7   6.00%
Arctic Ocean   1299.9   19073.9   6.81%


Thickness in metres.         
   Difference / 2012 Vol / %  Change
Other   0.00   0   0.00%
Okhotsk   -0.16   0.63   -25.25%
Bering   -0.28   0.49   -56.85%
Beaufort   -0.48   2.11   -22.50%
Chukchi   -0.40   2.39   -16.77%
ESS   -0.17   2.28   -7.34%
Laptev   0.00   1.64   -0.06%
Kara   0.28   0.83   34.33%
Barents   0.31   0.63   49.90%
Greenland   0.04   0.82   4.52%
Central   0.35   2.38   14.54%
CAA   0.07   1.95   3.67%
Baffin   0.17   0.92   18.38%
Hudson   0.08   1.14   6.90%
All   0.17   1.74   9.63%
Arctic Ocean   0.13   1.98   6.79%

Hope that's of use.

PS Beaufort is the thinnest and lowest volume on record!
Title: Re: Latest PIOMAS update (June)
Post by: Neven on June 08, 2015, 11:54:20 PM
PS Beaufort is the thinnest and lowest volume on record!

But that's where a lot of the MYI is...  ??? :-\
Title: Re: Latest PIOMAS update (June)
Post by: seaicesailor on June 09, 2015, 12:52:29 AM
PS Beaufort is the thinnest and lowest volume on record!

But that's where a lot of the MYI is...  ??? :-\

Well, in absolute terms, thickness is large in Beaufort this year, only that in earlier years it was probably more multi and more thick (pardon my english)
Title: Re: Latest PIOMAS update (June)
Post by: jdallen on June 09, 2015, 03:37:53 AM
PS Beaufort is the thinnest and lowest volume on record!

But that's where a lot of the MYI is...  ??? :-\
As I said elsewhere, we are in entirely unknown territory.

What is necessary now to save us from a new record minimum, is the best of possible weather to preserve the ice.

Poor melt conditions (e.g. 2013) might keep us in the bottom 5.

Even average melt conditions will put us into the bottom three, if not the bottom two or even lower than 2012.

Conditions optimal for melt will be catastrophic.
Title: Re: Latest PIOMAS update (June)
Post by: jdallen on June 09, 2015, 03:42:35 AM
P.S. - bets on whether or not Peter Wadhams will be saying "I told you so!" at the end of the season?

Cold comfort....
Title: Re: Latest PIOMAS update (June)
Post by: Vergent on June 09, 2015, 03:51:30 AM
Vergent,

Map or regional volume?

Wipneus may be the best bet for a map, since I re-wrote my code to tidy up, difference maps would need a total rewrite to get them running (it's complicated..). But regional figures I can do.

Volume and thickness, for May average, difference between 2012 and 2015 = 2015 - 2012.
Also for context 2012 volume for May and the percent change.

Volume in km^3.
   Difference / 2012 Vol / %  Change
Other   0.0   0.0   0.00%
Okhotsk   -42.2   108.2   -39.03%
Bering   -221.7   261.3   -84.84%
Beaufort   -257.9   1098.1   -23.49%
Chukchi   -238.0   1394.9   -17.06%
ESS   -149.2   2032.3   -7.34%
Laptev   -0.6   1049.1   -0.06%
Kara   242.4   624.5   38.82%
Barents   176.0   193.2   91.13%
Greenland   -62.0   650.4   -9.53%
Central   1535.1   10557.6   14.54%
CAA    54.0   1473.8   3.67%
Baffin   184.3   962.3   19.15%
Hudson   83.6   1309.0   6.39%
All   1303.9   21714.7   6.00%
Arctic Ocean   1299.9   19073.9   6.81%


Thickness in metres.         
   Difference / 2012 Vol / %  Change
Other   0.00   0   0.00%
Okhotsk   -0.16   0.63   -25.25%
Bering   -0.28   0.49   -56.85%
Beaufort   -0.48   2.11   -22.50%
Chukchi   -0.40   2.39   -16.77%
ESS   -0.17   2.28   -7.34%
Laptev   0.00   1.64   -0.06%
Kara   0.28   0.83   34.33%
Barents   0.31   0.63   49.90%
Greenland   0.04   0.82   4.52%
Central   0.35   2.38   14.54%
CAA   0.07   1.95   3.67%
Baffin   0.17   0.92   18.38%
Hudson   0.08   1.14   6.90%
All   0.17   1.74   9.63%
Arctic Ocean   0.13   1.98   6.79%

Hope that's of use.

PS Beaufort is the thinnest and lowest volume on record!

ChrisReynolds

Thanks! Maps would be more intuitive, and answer questions like; "is the thickness difference in the CAB bunched along the CAA?"

Verg

Title: Re: Latest PIOMAS update (July)
Post by: Wipneus on July 03, 2015, 02:15:03 PM
PIOMAS gridded data was updated (still waiting for the main daily data and graphs).

Here are the maps with monthly average thickness of June 2014, 2015 as well as the difference.

Title: Re: Latest PIOMAS update (July)
Post by: Wipneus on July 03, 2015, 02:16:57 PM
And difference in growth from May to June,  red means more thickening/less thinning.
Title: Re: Latest PIOMAS update (July)
Post by: Wipneus on July 03, 2015, 02:58:19 PM
Previous two posts are monthly average.
More interesting are of course the daily files, here is an animation of the June melt.

(click req'd)
Title: Re: Latest PIOMAS update (July)
Post by: Wipneus on July 03, 2015, 04:08:29 PM
For the curious, here are the monthly volumes derived from gridded daily data for June 30. May be slightly different from the real daily data.
It seems 2015 is still in sixth place, but coming closer...
   year    vol
1  2000 21.044
2  2001 21.074
3  2002 20.672
4  2003 20.071
5  2004 19.916
6  2005 18.564
7  2006 17.930
8  2007 15.594
9  2008 17.443
10 2009 16.564
11 2010 13.458
12 2011 12.917
13 2012 12.295
14 2013 14.041
15 2014 14.642
16 2015 15.263
Title: Re: Latest PIOMAS update (July)
Post by: Nightvid Cole on July 03, 2015, 06:15:22 PM
It is absolutely, positively weird just how thick PIOMAS thinks the ice off the CAA and Greenland have now become. If we are to believe it, that ice has gone from ~2.5 m in 2012 to > 4 m in 2015. This is a 70% increase in thickness!

What's even stranger still is that PIOMAS seems to have started seriously straying away from anything with a semblance of reality - the buoys on the Pacific side of the CAB are unanimous in telling us that this ice did not get above 2 - 2.05 m in thickness this past winter, and most of them topped out at only around 1.75 m. Yet PIOMAS thinks it got up to almost 2.5 m.

Also, TOPAZ4 seems to agree with Cryosat as well as ADS/VISHOP in telling us that the thick ice of 2014 on the CAA side of the Arctic had in fact moderated in thickness this year in winter and in spring. Quite to the contrary, PIOMAS is saying that this ice got even thicker, for a third straight year!!!

I am truly surprised by this. PIOMAS seemed to be a good model, or so I thought. Now it basically has gone its own way and is disagreeing with every other model and observation. Why????

Title: Re: Latest PIOMAS update (July)
Post by: Neven on July 03, 2015, 07:11:14 PM
I am truly surprised by this. PIOMAS seemed to be a good model, or so I thought. Now it basically has gone its own way and is disagreeing with every other model and observation. Why????

Don't draw conclusions too fast.
Title: Re: Latest PIOMAS update (July)
Post by: Nick_Naylor on July 03, 2015, 07:25:06 PM
Are there obvious differences between any reliable observations of thickness and the PIOMAS representation?

I am also a little confused about what is meant by "thickness" - regarding sea ice data, does this normally refer to the average thickness of the ice over the ice-covered area? That would be a useful definition, but I wonder which data sources are capable of measuring that. Particularly when discussing the type of heterogeneous rubble that is Beaufort, "thickness" can be a complicated property to represent in a single number.
Title: Re: Latest PIOMAS update (July)
Post by: Richard Rathbone on July 03, 2015, 07:45:39 PM
Wipneus' numbers give a bit more melt in June 2015 than 2014 or 2013, which is what would would be expected from May's melt ponds as assessed by Schroeder. The same sort of excess over 2014 for the rest of the season will bring 2015 volume close to or slightly below 2014 volume around the minimum.
Title: Re: Latest PIOMAS update (July)
Post by: Steven on July 03, 2015, 08:20:51 PM
It is absolutely, positively weird just how thick PIOMAS thinks the ice off the CAA and Greenland have now become. If we are to believe it, that ice has gone from ~2.5 m in 2012 to > 4 m in 2015. This is a 70% increase in thickness!

What's even stranger still is that PIOMAS seems to have started seriously straying away from anything with a semblance of reality - the buoys on the Pacific side of the CAB are unanimous in telling us that this ice did not get above 2 - 2.05 m in thickness this past winter, and most of them topped out at only around 1.75 m. Yet PIOMAS thinks it got up to almost 2.5 m.

Also, TOPAZ4 seems to agree with Cryosat as well as ADS/VISHOP in telling us that the thick ice of 2014 on the CAA side of the Arctic had in fact moderated in thickness this year in winter and in spring. Quite to the contrary, PIOMAS is saying that this ice got even thicker, for a third straight year!!!

I am truly surprised by this. PIOMAS seemed to be a good model, or so I thought. Now it basically has gone its own way and is disagreeing with every other model and observation. Why????

A few weeks ago I had a look at the IceBridge QuickLook data, which can be downloaded at this page (https://nsidc.org/data/docs/daac/icebridge/evaluation_products/sea-ice-freeboard-snowdepth-thickness-quicklook-index.html).  These data confirm that the sea ice north of the CAA was thicker in March 2015 than in preceding years.  Moreover, the same is true for the sea ice in Eastern Beaufort Sea.  That seems to be in good agreement with PIOMAS.

Regarding Cryosat, this recent paper by Ricker et al. 2015 (http://onlinelibrary.wiley.com/doi/10.1002/2015GL064081/full) may be relevant.  The paper suggest that Cryosat overestimated the sea ice freeboard and thickness north of the CAA during the 2013/2014 freezing season, due to snow backscatter of the radar signal.  Here are the concluding paragraphs of the Ricker et al. paper (see especially the first one):

An exceptional high snow depth and early accumulation during the freezing season 2013/2014 north of Canada, shown by IMB measurements and indicated by Operation IceBridge snow depth retrievals, might have lead to the major increase of CryoSat-2 multiyear ice freeboard in November 2013 for this region. By quantifying the impact on CryoSat-2 sea ice thickness retrievals, we obtain a mean multiyear ice thickness bias of 1.4 m, if it is assumed that the main scattering horizon is given by the snow-ice interface.

We conclude that snowfall can have a significant impact on CryoSat-2 range measurements and therefore on ice freeboard, thickness, and volume. The assumption that the CryoSat-2 main scattering horizon is given by the snow-ice interface cannot be justified in regions with a thick snow layer. Finally, this study also shows that there is a strong need for more data and knowledge about the seasonal cycle of snow distribution and properties on sea ice.
Title: Re: Latest PIOMAS update (July)
Post by: seaicesailor on July 03, 2015, 08:47:31 PM
Actually the animation confirms the 1 m thinning of the ice from Beaufort to Laptev and part of the CAB. So no surprise about something I still dont understand. What caused such thinning in this particular June month? Storms?

In Beaufort the av thickness is about or less than 1m, but because of open water, the MYI floes probably are 1.5 to 2 m thick.
Title: Re: Latest PIOMAS update (July)
Post by: Nightvid Cole on July 03, 2015, 08:53:46 PM
It is absolutely, positively weird just how thick PIOMAS thinks the ice off the CAA and Greenland have now become. If we are to believe it, that ice has gone from ~2.5 m in 2012 to > 4 m in 2015. This is a 70% increase in thickness!

What's even stranger still is that PIOMAS seems to have started seriously straying away from anything with a semblance of reality - the buoys on the Pacific side of the CAB are unanimous in telling us that this ice did not get above 2 - 2.05 m in thickness this past winter, and most of them topped out at only around 1.75 m. Yet PIOMAS thinks it got up to almost 2.5 m.

Also, TOPAZ4 seems to agree with Cryosat as well as ADS/VISHOP in telling us that the thick ice of 2014 on the CAA side of the Arctic had in fact moderated in thickness this year in winter and in spring. Quite to the contrary, PIOMAS is saying that this ice got even thicker, for a third straight year!!!

I am truly surprised by this. PIOMAS seemed to be a good model, or so I thought. Now it basically has gone its own way and is disagreeing with every other model and observation. Why????

A few weeks ago I had a look at the IceBridge QuickLook data, which can be downloaded at this page (https://nsidc.org/data/docs/daac/icebridge/evaluation_products/sea-ice-freeboard-snowdepth-thickness-quicklook-index.html).  These data confirm that the sea ice north of the CAA was thicker in March 2015 than in preceding years.  Moreover, the same is true for the sea ice in Eastern Beaufort Sea.  That seems to be in good agreement with PIOMAS.

Regarding Cryosat, this recent paper by Ricker et al. 2015 (http://onlinelibrary.wiley.com/doi/10.1002/2015GL064081/full) may be relevant.  The paper suggest that Cryosat overestimated the sea ice freeboard and thickness north of the CAA during the 2013/2014 freezing season, due to snow backscatter of the radar signal.  Here are the concluding paragraphs of the Ricker et al. paper (see especially the first one):

An exceptional high snow depth and early accumulation during the freezing season 2013/2014 north of Canada, shown by IMB measurements and indicated by Operation IceBridge snow depth retrievals, might have lead to the major increase of CryoSat-2 multiyear ice freeboard in November 2013 for this region. By quantifying the impact on CryoSat-2 sea ice thickness retrievals, we obtain a mean multiyear ice thickness bias of 1.4 m, if it is assumed that the main scattering horizon is given by the snow-ice interface.

We conclude that snowfall can have a significant impact on CryoSat-2 range measurements and therefore on ice freeboard, thickness, and volume. The assumption that the CryoSat-2 main scattering horizon is given by the snow-ice interface cannot be justified in regions with a thick snow layer. Finally, this study also shows that there is a strong need for more data and knowledge about the seasonal cycle of snow distribution and properties on sea ice.

Thanks - the Ricker et al. paper was quite interesting, and does explain a lot. It also seems unsurprising in light of the fact that it seems that microwaves' penetrating power of lots of things seems to often be overstated - yet in reality, even light things scatter and block microwaves quite a bit. The same phenomenon probably accounts for why clouds block the passive microwave data so easily, why bad weather interrupts satellite TV, and cell phone signals get cut out so easily. In all these cases, it seems the assumption (though incorrect) is that dielectrics are transparent, even though in reality they are not - as observation demonstrates.

However, this still does not solve the paradox of why TOPAZ4 and PIOMAS get such dramatically different answers, nor does it explain why PIOMAS disagrees with the buoy observations about ice thickness in the Beaufort/Chukchi sector of the CAB.

Title: Re: Latest PIOMAS update (July)
Post by: Lord M Vader on July 03, 2015, 09:04:29 PM
Wipneus: do you have an opportunity to make a schematic map of the difference in sea ice thickness for the period June 1- June 30? Would be very interesting to see it black and white how much thinner the ice have been in the different regions.

Best, LMV
Title: Re: Latest PIOMAS update (July)
Post by: ChrisReynolds on July 03, 2015, 11:05:47 PM
Actually the animation confirms the 1 m thinning of the ice from Beaufort to Laptev and part of the CAB. So no surprise about something I still dont understand. What caused such thinning in this particular June month? Storms?

In Beaufort the av thickness is about or less than 1m, but because of open water, the MYI floes probably are 1.5 to 2 m thick.

If the PIOMAS sub grid thickness distribution is right (it probably is more or less) then here are the June GICE sub grid thickness distributions for post 2010 years in Beaufort. So for example, the thickness band centred on 20.62m thick has a volume of 12.78km^3, this is intended to represent the bands of ridged ice in pressure ridges across the pack.

Thickness   2010   2011   2012   2013   2014   2015
0m   0.00   0.00   0.00   0.00   0.00   0.00
0.26m   16.43   19.59   13.77   11.52   18.25   14.34
0.71m   36.53   3.62   5.80   10.43   26.04   22.26
1.46m   110.35   94.96   74.72   197.02   147.39   108.75
2.61m   126.56   268.06   184.41   340.86   201.56   173.55
4.23m   64.11   139.46   115.87   180.58   98.31   104.71
6.39m   30.05   47.07   39.45   73.73   40.41   42.82
9.1m   26.82   38.47   26.54   69.89   32.41   36.58
12.39m   26.98   42.87   28.50   78.66   32.39   39.20
16.24m   26.90   45.16   28.44   80.30   30.86   39.79
20.62m   8.27   18.05   7.37   21.16   4.45   12.78
25.49m   2.96   5.90   2.39   6.85   1.29   4.30

This also answers the concerns about PIOMAS disagreeing with one point in a million km^2 area (519000km^2 for Beaufort, 584000km^2 for Chukchi). What you see in Wipneus's plots is the grid box effective thickness. The relationship between the effective thickness and the sub grid thickness distributions is explained here:
http://dosbat.blogspot.co.uk/2015/04/what-is-piomas-gice.html (http://dosbat.blogspot.co.uk/2015/04/what-is-piomas-gice.html)

There is no discrepancy between PIOMAS and the single points from bouys, this issue is why point data like Buoys were not used in the Schweiger et al 2011 intercomparison study. Moored ULS sounders were used, but they are fixed to the sea ice, and sea ice movement can present the range of actual thickness.

PIOMAS has a bias: From Schweiger et al 2011 "PIOMAS appears to overestimate thin ice thickness and underestimate thick ice, yielding a smaller downward trend than apparent in reconstructions from observations."

PIOMAS gain since June 2012.
(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2F2.bp.blogspot.com%2F-mJ2kuPc0iQU%2FVZbT0Qty-xI%2FAAAAAAAACQI%2Ff4tb-EVfBPc%2Fs1600%2FJune%252BVolume%252Bdelta.png&hash=a649f5af5d68378fa705a72693a16052)
Title: Re: Latest PIOMAS update (July)
Post by: slow wing on July 04, 2015, 12:52:11 AM
Regarding Nightvid Cole's & Steven's posts, a quick comparison shows PIOMAS might have been a little thicker in the Chukchi & Beaufort than CryoSat actually measured, when compared for May 2015. (Cryosat couldn't measure any later in the Summer due to melt ponds.)

Wipneus posted the May PIOMAS thickness reconstruction here...
http://forum.arctic-sea-ice.net/index.php/topic,119.msg53274.html#msg53274 (http://forum.arctic-sea-ice.net/index.php/topic,119.msg53274.html#msg53274)

While the roughly corresponding map from CryoSat is here...
http://www.cpom.ucl.ac.uk/csopr/seaice.html (http://www.cpom.ucl.ac.uk/csopr/seaice.html)

Probably the best comparison is to click on "14 days", which shows 5-19 May for Cryosat.

The Chukchi Sea for that plot is, very roughly speaking, mostly a mix of green & yellow areas, which is, respectively, the 1.75-2.00m and 2.00-2.25 m thickness bins.
So the average looks about 2m.

For comparison, PIOMAS in the same region shows mostly the 2.00-2.25 bins, with some thicker but little in the yellow 1.75-2.00m thickness bin.


So, at first glance, PIOMAS looked slightly thicker there than the CryoSat measurements, perhaps by of order 10%. This is hardly surprising given the model and measurement uncertainties.


That was just a quick eyeball comparison. I'm sure the scientists themselves have done a more thorough comparison.
Title: Re: Latest PIOMAS update (July)
Post by: Nightvid Cole on July 04, 2015, 01:57:18 AM
Actually the animation confirms the 1 m thinning of the ice from Beaufort to Laptev and part of the CAB. So no surprise about something I still dont understand. What caused such thinning in this particular June month? Storms?

In Beaufort the av thickness is about or less than 1m, but because of open water, the MYI floes probably are 1.5 to 2 m thick.

If the PIOMAS sub grid thickness distribution is right (it probably is more or less) then here are the June GICE sub grid thickness distributions for post 2010 years in Beaufort. So for example, the thickness band centred on 20.62m thick has a volume of 12.78km^3, this is intended to represent the bands of ridged ice in pressure ridges across the pack.

Thickness   2010   2011   2012   2013   2014   2015
0m   0.00   0.00   0.00   0.00   0.00   0.00
0.26m   16.43   19.59   13.77   11.52   18.25   14.34
0.71m   36.53   3.62   5.80   10.43   26.04   22.26
1.46m   110.35   94.96   74.72   197.02   147.39   108.75
2.61m   126.56   268.06   184.41   340.86   201.56   173.55
4.23m   64.11   139.46   115.87   180.58   98.31   104.71
6.39m   30.05   47.07   39.45   73.73   40.41   42.82
9.1m   26.82   38.47   26.54   69.89   32.41   36.58
12.39m   26.98   42.87   28.50   78.66   32.39   39.20
16.24m   26.90   45.16   28.44   80.30   30.86   39.79
20.62m   8.27   18.05   7.37   21.16   4.45   12.78
25.49m   2.96   5.90   2.39   6.85   1.29   4.30

This also answers the concerns about PIOMAS disagreeing with one point in a million km^2 area (519000km^2 for Beaufort, 584000km^2 for Chukchi). What you see in Wipneus's plots is the grid box effective thickness. The relationship between the effective thickness and the sub grid thickness distributions is explained here:
http://dosbat.blogspot.co.uk/2015/04/what-is-piomas-gice.html (http://dosbat.blogspot.co.uk/2015/04/what-is-piomas-gice.html)

There is no discrepancy between PIOMAS and the single points from bouys, this issue is why point data like Buoys were not used in the Schweiger et al 2011 intercomparison study. Moored ULS sounders were used, but they are fixed to the sea ice, and sea ice movement can present the range of actual thickness.

PIOMAS has a bias: From Schweiger et al 2011 "PIOMAS appears to overestimate thin ice thickness and underestimate thick ice, yielding a smaller downward trend than apparent in reconstructions from observations."

PIOMAS gain since June 2012.
(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2F2.bp.blogspot.com%2F-mJ2kuPc0iQU%2FVZbT0Qty-xI%2FAAAAAAAACQI%2Ff4tb-EVfBPc%2Fs1600%2FJune%252BVolume%252Bdelta.png&hash=a649f5af5d68378fa705a72693a16052)

Ok, this makes sense. One minor quibble - the 0.000m thickness band is obviously only those with thicknesses less than or equal to 0.00m - otherwise the volume would not be zero. It is *not* a band centered on 0.00m.

So I'd assume that, likewise, "0.26m" is thicknesses UP TO 0.26m, not "centered on" 0.26m, and so on. Right?
Title: Re: Latest PIOMAS update (July)
Post by: oren on July 04, 2015, 06:24:04 AM
Ok, this makes sense. One minor quibble - the 0.000m thickness band is obviously only those with thicknesses less than or equal to 0.00m - otherwise the volume would not be zero. It is *not* a band centered on 0.00m.

So I'd assume that, likewise, "0.26m" is thicknesses UP TO 0.26m, not "centered on" 0.26m, and so on. Right?

My wild uneducated guess, just by looking at the numbers, is that 0.26 is a band of 0.01-0.50, 0.71 is 0.51 to 1.00, and then 1-2, 2-3, 3-5 etc.
0.00 is a band of 0.00-0.00
Title: Re: Latest PIOMAS update (July)
Post by: ChrisReynolds on July 04, 2015, 08:21:19 AM
Nightvid, Oren,

The bands are given in my post on PIOMAS Gice, from the paper by Dr Zhang, they're shown in the image below.
(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2F1.bp.blogspot.com%2F-bZJ52Kc_3aA%2FVTaXXMfbv_I%2FAAAAAAAABvg%2Fzmb2n_-Uxw0%2Fs1600%2FZR%252BFig2.png&hash=84620da66353b6edde7dc3df692b525b)
Title: Re: Latest PIOMAS update (July)
Post by: Nightvid Cole on July 04, 2015, 01:55:41 PM
Nightvid, Oren,

The bands are given in my post on PIOMAS Gice, from the paper by Dr Zhang, they're shown in the image below.
(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2F1.bp.blogspot.com%2F-bZJ52Kc_3aA%2FVTaXXMfbv_I%2FAAAAAAAABvg%2Fzmb2n_-Uxw0%2Fs1600%2FZR%252BFig2.png&hash=84620da66353b6edde7dc3df692b525b)

Since negative thicknesses are physically nonsensical, shouldn't you use 0.05 as the thickness to calculate the volume of the "0" band, since it represents thicknesses from -0.1 to 0.1 and thus physically must be 0 to 0.1, with a middle of 0.05?

In other words, volume = area * 0.05, not area * 0?

OR, alternatively, would this lead to the entire open water portion of the domain making a spurious contribution to the volume?

Is there any distinction between "real" zero and "very very thin" ice?
Title: Re: Latest PIOMAS update (July)
Post by: Tor Bejnar on July 04, 2015, 01:57:34 PM
So why does the 0m band (that includes ice up to 0.10 m thick) always have 0.00 volume? 

Assuming an actual average thickness of 0.05 m (5 cm or 5x10-5 km), it would required 200 km2 to reach a volume of 0.01 km3. (It could be almost half this area and round to 0.01 km3.)  The least volume recorded, 1.29 km3 averages 25.49 m (or 0.02549 km)[assuming equal distribution across its thickness] covers only 50.6 km2.
Title: Re: Latest PIOMAS update (July)
Post by: oren on July 04, 2015, 05:18:58 PM
Nightvid, Oren,

The bands are given in my post on PIOMAS Gice, from the paper by Dr Zhang, they're shown in the image below.
(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2F1.bp.blogspot.com%2F-bZJ52Kc_3aA%2FVTaXXMfbv_I%2FAAAAAAAABvg%2Fzmb2n_-Uxw0%2Fs1600%2FZR%252BFig2.png&hash=84620da66353b6edde7dc3df692b525b)

Thanks Chris.
Title: Re: Latest PIOMAS update (July)
Post by: ChrisReynolds on July 04, 2015, 05:23:56 PM
Mathematically the zero thickness band needs upper and lower limits, those limits have been chosen as shown. Zero thickness band is open water, not very thin ice, this is by definition. The bands are bands of thickness within the grid box upon which the equation set of the model operates, moving ice volume up and down through the bands according to the modelled processes.

When you take grid box effective thickness the situation is different, a gbet if 0.1m may indeed represent dispersed ice, which in theory could be thick chunks in a lot of open water.

Typing on a very bouncy bus! Hope I make sense.

PS just occurred to me that if lower limit of zero band were zero exactly ut might make the equations crash.
Title: Re: Latest PIOMAS update (July)
Post by: Peter Ellis on July 04, 2015, 07:08:28 PM
Right, so if I understand it right.

1) The lowest band in the model represents open water
2) That band therefore has to have a _central_ value of zero
3) A band can't have zero width

Therefore, they've chosen +10cm as being effectively negligible, i.e. everything less than 10cm counts as zero / open water. The -10 cm lower limit of the band is simply a mathematical trick to enforce the real rule, which is "treat everything lower than 10cm as open water / zero ice".
Title: Re: Latest PIOMAS update (July)
Post by: Andreas T on July 04, 2015, 08:09:49 PM
Couldn't  the question whether the band named "0.0m" has no ice in it because at this time of the year thin ice has melted away or it is by definition a band of 0 volume  be answered by looking at October or November when one can expect substantial areas of ice between 0 and 0.1m thick? I don't know where to look though.
Title: Re: Latest PIOMAS update (July)
Post by: Tor Bejnar on July 04, 2015, 08:33:31 PM
Thanks again Chris and Peter, too!  Those pesky infinities and undefined functions.  :)
Title: Re: Latest PIOMAS update (July)
Post by: Nightvid Cole on July 04, 2015, 10:42:10 PM
Mathematically the zero thickness band needs upper and lower limits, those limits have been chosen as shown. Zero thickness band is open water, not very thin ice, this is by definition.

No, "open water" is a thickness of precisely 0, not a thickness of < 0.1m!!!

The bands are bands of thickness within the grid box upon which the equation set of the model operates, moving ice volume up and down through the bands according to the modelled processes.

When you take grid box effective thickness the situation is different, a gbet if 0.1m may indeed represent dispersed ice, which in theory could be thick chunks in a lot of open water.

Typing on a very bouncy bus! Hope I make sense.

PS just occurred to me that if lower limit of zero band were zero exactly ut might make the equations crash.

I don't get it. What happens when ice first "grows" from zero thickness? There is necessarily a time when it is not zero, but is less than 0.1m. How is this handled by the model?
Title: Re: Latest PIOMAS update (July)
Post by: Andreas T on July 05, 2015, 04:36:44 AM
Mathematically the zero thickness band needs upper and lower limits, those limits have been chosen as shown. Zero thickness band is open water, not very thin ice, this is by definition.

No, "open water" is a thickness of precisely 0, not a thickness of < 0.1m!!!

The bands are bands of thickness within the grid box upon which the equation set of the model operates, moving ice volume up and down through the bands according to the modelled processes.

...........

I don't get it. What happens when ice first "grows" from zero thickness? There is necessarily a time when it is not zero, but is less than 0.1m. How is this handled by the model?
having had a look at http://journals.ametsoc.org/doi/pdf/10.1175/1520-0493%282003%29131%3C0845%3AMGSIWA%3E2.0.CO%3B2 (http://journals.ametsoc.org/doi/pdf/10.1175/1520-0493%282003%29131%3C0845%3AMGSIWA%3E2.0.CO%3B2) I think I understand what Chris is saying.
The model approximates the range of ice thickness in a grid cell by a set of 12 thickness "bins". That means when water freezes the 0.0m bin becomes less full and the 0.26m bin becomes fuller, there just are no thickness values in between. Thickening through freezing or compaction / ridging moves ice from the 0.26m bin to the 0.71m bin and so on. This is the usual way for treating a continuous variable in discrete steps in numerical models.
Title: Re: Latest PIOMAS update (July)
Post by: ChrisReynolds on July 05, 2015, 09:25:08 AM
Peter, exactly right.

Mathematically the zero thickness band needs upper and lower limits, those limits have been chosen as shown. Zero thickness band is open water, not very thin ice, this is by definition.

No, "open water" is a thickness of precisely 0, not a thickness of < 0.1m!!!

The bands are bands of thickness within the grid box upon which the equation set of the model operates, moving ice volume up and down through the bands according to the modelled processes.

...........

I don't get it. What happens when ice first "grows" from zero thickness? There is necessarily a time when it is not zero, but is less than 0.1m. How is this handled by the model?
having had a look at http://journals.ametsoc.org/doi/pdf/10.1175/1520-0493%282003%29131%3C0845%3AMGSIWA%3E2.0.CO%3B2 (http://journals.ametsoc.org/doi/pdf/10.1175/1520-0493%282003%29131%3C0845%3AMGSIWA%3E2.0.CO%3B2) I think I understand what Chris is saying.
The model approximates the range of ice thickness in a grid cell by a set of 12 thickness "bins". That means when water freezes the 0.0m bin becomes less full and the 0.26m bin becomes fuller, there just are no thickness values in between. Thickening through freezing or compaction / ridging moves ice from the 0.26m bin to the 0.71m bin and so on. This is the usual way for treating a continuous variable in discrete steps in numerical models.

Yes, you are right. The equation set behind PIOMAS will create a continuous (not banded) distribution of thickness change, after each iteration of the model's equations there is a process of setting the resultant new thicknesses into the new band. I guess that during summer as ice melts the downward movement of thickness dumps more area into the open water band, before allocating things like rounding errors may produce slightly negative thickness, this would then be reset to zero.

****

Rather than look at it in terms of volume, perhaps it would be best to look at area of each band.

In the following I have summed to bands, OW is open water (0m thickness), <3.3m is the sum of the 0.26m to 2.61m bands, >3.3m is the sum of the 4.23 to 25.49m bands. I have chosen the Central Arctic.

First here is the annual cycle for the year 2000, a year chosen randomly as a year before the post 2007 changes. OW is open water

Annual         
___   OW   <3.3m   >3.3m
Jan   0.059   3.541   0.828
Feb   0.040   3.479   0.908
Mar   0.039   3.393   0.995
Apr   0.039   3.306   1.082
May   0.083   3.196   1.149
Jun   0.260   3.002   1.166
Jul   0.567   2.862   0.998
Aug   0.678   2.917   0.833
Sep   0.391   3.255   0.782
Oct   0.198   3.461   0.769
Nov   0.116   3.555   0.757
Dec   0.071   3.567   0.789

The figures are area in million kmsq. So in April 0.039 million kmsq is open water, 3.306million kmsq has ice less than 3.3m thick, 1.082 has ice over 3.3m thick. So even in April for the PIOMAS model there is about 0.9% open water (0.039 million kmsq) within the Central Arctic. In 2000 the peak open water was in August at 15% of the total area of the Central Arctic.

Turning to September the areas of the two thickness bands and open water (OW) are tabled below.

September         
___   OW   <3.3m   >3.3m
1979   0.433   2.884   1.111
1980   0.221   3.114   1.092
1981   0.334   3.246   0.848
1982   0.276   3.295   0.856
1983   0.354   3.089   0.984
1984   0.511   2.928   0.988
1985   0.473   3.032   0.923
1986   0.302   3.019   1.108
1987   0.228   3.122   1.078
1988   0.263   3.118   1.046
1989   0.276   3.071   1.080
1990   0.454   2.950   1.023
1991   0.445   3.067   0.915
1992   0.276   3.097   1.055
1993   0.387   3.096   0.945
1994   0.320   3.111   0.997
1995   0.485   3.137   0.806
1996   0.370   3.158   0.899
1997   0.280   3.180   0.968
1998   0.585   3.057   0.785
1999   0.522   3.169   0.737
2000   0.391   3.255   0.782
2001   0.477   3.133   0.818
2002   0.470   3.134   0.824
2003   0.516   3.158   0.754
2004   0.568   3.224   0.635
2005   0.583   3.216   0.628
2006   0.506   3.336   0.585
2007   1.598   2.357   0.472
2008   1.242   2.655   0.531
2009   1.252   2.669   0.507
2010   1.578   2.539   0.310
2011   1.575   2.562   0.291
2012   2.275   1.882   0.270
2013   1.331   2.773   0.323
2014   1.275   2.670   0.482

Look at what happened in 2007!

PIOMAS is adjusted by concentration from NSIDC, the same data used to make NSIDC extent and area. That noted, as an 'idiot check' I have scatter plotted PIOMAS fraction of open water in the Central Arctic, and NSIDC September average Area divided by March 1981 to 2010 average extent as the open water fraction for NSIDC. This is attached as a graphic.

Title: Re: Latest PIOMAS update (July)
Post by: Nick_Naylor on July 05, 2015, 02:33:09 PM
If the PIOMAS sub grid thickness distribution is right (it probably is more or less) then here are the June GICE sub grid thickness distributions for post 2010 years in Beaufort. So for example, the thickness band centred on 20.62m thick has a volume of 12.78km^3, this is intended to represent the bands of ridged ice in pressure ridges across the pack.

Thickness   2010   2011   2012   2013   2014   2015
0m   0.00   0.00   0.00   0.00   0.00   0.00
0.26m   16.43   19.59   13.77   11.52   18.25   14.34
0.71m   36.53   3.62   5.80   10.43   26.04   22.26
. . .

Chris, does this data set represent an average for the full month of June, or the month-end values? If not month-end, is that available?

Thanks
Title: Re: Latest PIOMAS update (July)
Post by: ChrisReynolds on July 05, 2015, 10:50:34 PM
Nick,

It's all June average. I have some bare bones code to handle the daily data, but as that only goes back to 2000 I don't normally bother with it. I'll post some figures for the end of the month if needed (for Beaufort?).

If I haven't done so by this time Tuesday, PM me to prompt me.
Title: Re: Latest PIOMAS update (July)
Post by: ChrisReynolds on July 06, 2015, 06:47:45 PM
Nick, I have all the data for Gice sub grid volumes from 2007 to 2015 30 June.

For example, here is...

Peripheral Seas (Beaufort, Chukchi, ESS, Laptev)
   <3.3m   >3.3m
2007   1426.1   916.3
2008   2019.8   1270.0
2009   1747.3   1055.5
2010   1474.1   1826.7
2011   1476.6   847.2
2012   1476.4   1113.7
2013   1791.1   1513.8
2014   1515.8   803.7
2015   1663.8   1023.6

Central Arctic.
   <3.3m   >3.3m
2007   4768.0   4604.9
2008   5005.2   4455.0
2009   5283.1   4354.1
2010   4365.4   3475.3
2011   4662.7   3763.1
2012   4529.6   3805.1
2013   4971.8   3711.7
2014   5326.4   4744.5
2015   4516.3   5494.0

Regions as per Cryosphere Today, volumes in 1000km^3.

Last year had a lower volume of thick ice in peripheral seas. This year is a bit lower than 2012.

Here are the numbers for Beaufort.

   >3.3m   <3.3m   Total
2007   0.273   0.194   0.467
2008   0.151   0.143   0.293
2009   0.266   0.160   0.427
2010   0.154   0.100   0.254
2011   0.243   0.234   0.477
2012   0.150   0.133   0.283
2013   0.446   0.447   0.893
2014   0.211   0.146   0.357
2015   0.236   0.234   0.470

2012 was much lower, but really the excitement this year is in Chukchi, ESS, and Laptev.

Although I said I doubt we'll get near 2012 this year, and that remains my formal position. I am allowing myself to get a bit excited about the state in Chukchi, ESS and Laptev.  ;D
Title: Re: Latest PIOMAS update (July)
Post by: Nick_Naylor on July 06, 2015, 08:28:45 PM
Thanks Chris. Is the Beaufort data scaled differently?

Also, do you have a link to the raw data, assuming it's publicly available?
Title: Re: Latest PIOMAS update (July)
Post by: ChrisReynolds on July 06, 2015, 08:52:24 PM
Yes, sorry, I'm not properly set up with this and the sheet is a messy hotch potch reflecting me messing around with the data. The Beaufort data is thousand km^3. This does not impact the other Peripheral Seas or Central Arctic data.

I've uploaded the tabulated raw data here, I have also tagged on the 31 May data.

https://drive.google.com/file/d/0B3pB-kdzoLU3NHRLU3JENFVtbXc/view?usp=sharing

I'll keep it there for a few days.

I caution, I have not really been using this data, it should be correct as I use the same core code to generate as for the monthly data - but I have not properly checked it nor have I used in such a way that problems would become apparent. The main check would be comparison with the PIOMAS main series of volume, but I just haven't had the time to do that.

So it is provided 'without warranty', so to speak. But I wouldn't post it if I wasn't happy to use it myself for my own purposes.
Title: Re: Latest PIOMAS update (July)
Post by: seaicesailor on July 06, 2015, 09:14:33 PM
Nick, I have all the data for Gice sub grid volumes from 2007 to 2015 30 June.

For example, here is...

Peripheral Seas (Beaufort, Chukchi, ESS, Laptev)
   <3.3m   >3.3m
2007   1426.1   916.3
2008   2019.8   1270.0
2009   1747.3   1055.5
2010   1474.1   1826.7
2011   1476.6   847.2
2012   1476.4   1113.7
2013   1791.1   1513.8
2014   1515.8   803.7
2015   1663.8   1023.6

Central Arctic.
   <3.3m   >3.3m
2007   4768.0   4604.9
2008   5005.2   4455.0
2009   5283.1   4354.1
2010   4365.4   3475.3
2011   4662.7   3763.1
2012   4529.6   3805.1
2013   4971.8   3711.7
2014   5326.4   4744.5
2015   4516.3   5494.0

Regions as per Cryosphere Today, volumes in 1000km^3.

Last year had a lower volume of thick ice in peripheral seas.

Evaluate something by eyeballing a map can be just very wrong . Thank you for these computations.

Title: Re: Latest PIOMAS update (July)
Post by: ChrisReynolds on July 06, 2015, 09:32:01 PM
This also has the advantage of giving you the picture from within the model, not just grid box effective area. But I haven't a clue how to practically give this data in map form, unless I use 12 images as an animated gif - which is a lot of work for me.
Title: Re: Latest PIOMAS update (July)
Post by: Wipneus on July 07, 2015, 07:05:22 PM
The official PIOMAS update is there as well. I have updated my graphs, you can see them in the top post (http://forum.arctic-sea-ice.net/index.php/topic,119.msg1562.html#msg1562)
Title: Re: Latest PIOMAS update (July)
Post by: Neven on July 07, 2015, 07:18:17 PM
The official PIOMAS update is there as well. I have updated my graphs, you can see them in the top post (http://forum.arctic-sea-ice.net/index.php/topic,119.msg1562.html#msg1562)

Thanks, wip!
Title: Re: Latest PIOMAS update (July)
Post by: epiphyte on July 08, 2015, 06:47:21 AM
I just want to ping everyone on something I brought up in early March, just before the PIOMAS Feb numbers came out. At that time I said that PIOMAS Feb-April volume increase was very likely to be greater than last year, even if freezing conditions turned out to be crappy throughout.

In the event freezing conditions did appear to be awfully bad, and PIOMAS volume growth was indeed unusually high.  As I outlined at the time (reasoning cut-and-pasted below) the error was already baked-in, and IMO the only question now is whether things get bad enough to directly observe that this was the case...

Flawed as I believe PIOMAS to be for thin/melting ice, for trends I would have guessed that adding the extra dimension might filter out some of the noise from variations in here-today, gone-tomorrow start/end of season weather conditions. Others have suggested that these effects make area/extent on it's own useless as a predictor of what's going to happen later on in the season - and I'd generally agree.

But eyeballing those PIOMAS monthly trends it seems to me that there's been something very odd going over the past year... either with the model, or with the real world, or both... Viz:

1. The trends for March and May crossed in 2009. Before then, there was consistently more ice in May than in March, since then there has consistently been less ice in May than there was in March - including last year, which was well above the trend for both months.

2. According to PIOMAS there has since 2009 been a consistent 1M km3 volume gain Mar-Apr , and it has always been lost Apr-May, again regardless of trend.

3. Backing up to January , and roughly eyeballing the graph, PIOMAS has never come up with a Jan-Feb volume increase of less than ~2.5 Mkm3, or a Feb-Mar increase less than ~2Mkm3

So if PIOMAS stays true to form, the Feb number will be >= 21M, and under better-than-existing worst case conditions the the March number will be >= 23M and the April number will be >= 24M

In other words, the January number is high enough to guarantee that the April number will be more than a million km3 *higher* than it was in 2014, absent worse than existing worst-case behavior in February and March.

So we just lived through Feb - and to my eyes at least it looked as though it might indeed have have been the worst ever. Assume that PIOMAS cuts it's previous worst-case Feb growth in half (i.e. from ~2.5 to ~1.25m). If it did that the Feb number would be the same as it was last year.

Looking at the actual area today it is essentially the same as it was this time last year - so If PIOMAS does come up with a 50% cut in Feb volume growth over 2014 (which itself was very low),  it might be a plausible number - albeit an unprecedentedly bad February for the arctic -  but only if the avg. thickness is also now the same as this time last year. This seems a stretch given the weak winter and the low thickness estimates. If the ice is actually thinner, then PIOMAS would need essentially zero Feb growth to avoid coming up with an incredible number for Apr/May.

If, OTOH, PIOMAS comes in with the same (already low) Feb & Mar growth that it did in 2014, it can only end with a modeled March-May volume >1m km3 higher than it was last year, which would IMO be astonishing if true, because it would imply faster Feb growth than 2014, on top of thicker ice than 2014, in the presence of higher temperatures than 2014.

So all in all, I'm wondering if this might be the year when PIOMAS last-meter uncertainties finally cause it to part company with directly observable reality.

Looking back over the past four months, I haven't yet seen anything to disabuse me of any of the above...



Title: Re: Latest PIOMAS update (July)
Post by: iwantatr8 on July 08, 2015, 12:29:53 PM
Following Chris's useful data I thought I would try to come up with a way to represent it graphically.
I've reduced the data to 3 thickness buckets and then done a %age difference from 2007 for each different location. it produces some interesting views about how things have changed. 
Most interesting is the changing thickness in the arctic ocean where the lead up to 2012 can clearly be seen contrasting against the thickness this year.

Title: Re: Latest PIOMAS update (July)
Post by: Rubikscube on July 08, 2015, 01:04:13 PM
Following Chris's useful data I thought I would try to come up with a way to represent it graphically.
I've reduced the data to 3 thickness buckets and then done a %age difference from 2017 for each different location. it produces some interesting views about how things have changed. 
Most interesting is the changing thickness in the arctic ocean where the lead up to 2012 can clearly be seen contrasting against the thickness this year.

Niiiiice!

But I suppose you mean 2007 and not 2017?
Title: Re: Latest PIOMAS update (July)
Post by: iwantatr8 on July 08, 2015, 01:19:09 PM
Yes indeed, my forecasting skills are not that good!

 ;D
Title: Re: Latest PIOMAS update (July)
Post by: ChrisReynolds on July 08, 2015, 07:34:26 PM
Epiphyte,

Your statements are in quotes.

1. The trends for March and May crossed in 2009. Before then, there was consistently more ice in May than in March, since then there has consistently been less ice in May than there was in March - including last year, which was well above the trend for both months.


This crossing is due to the PIOMAS spring volume loss, which involves anomalous loss of volume from around 20 April to around the solstice. I shall shortly be blogging further on why this anomaly should be viewed as a result of thinning, particularly in the Central Arctic since the 2010 volume loss event.

2. According to PIOMAS there has since 2009 been a consistent 1M km3 volume gain Mar-Apr , and it has always been lost Apr-May, again regardless of trend.

Again, an effect of the PIOMAS spring volume loss anomaly, prior to 2010 the Apr-May volume loss was substantially lower.

3. Backing up to January , and roughly eyeballing the graph, PIOMAS has never come up with a Jan-Feb volume increase of less than ~2.5 Mkm3, or a Feb-Mar increase less than ~2Mkm3

So if PIOMAS stays true to form, the Feb number will be >= 21M, and under better-than-existing worst case conditions the the March number will be >= 23M and the April number will be >= 24M

Jan to Feb; The average increase is 2.74, the min is 2.23, but broadly correct. At 3.01 the 2015 jan Feb increase was above average but substantially less than the post 2012 increase of 3.52, which was driven by the thickness growth feedback.

Feb to Mar: Quite a few years were below 2Mkm^2, 1978, 1979, 1980, 1984, 1987, 1989, 1990, 1992, 1993... sorry I got bored with that list. 2015 was 1.75, not unusal. Lower September extent leads to greater growth - the growth thickness feedback again.

In other words, the January number is high enough to guarantee that the April number will be more than a million km3 *higher* than it was in 2014, absent worse than existing worst-case behavior in February and March.


Yes, it was 1.31 higher.

So we just lived through Feb - and to my eyes at least it looked as though it might indeed have have been the worst ever. Assume that PIOMAS cuts it's previous worst-case Feb growth in half (i.e. from ~2.5 to ~1.25m). If it did that the Feb number would be the same as it was last year.

Sorry, you lost me here, but February volume was 23.21, Jan Feb gain was 3.01 not unusual, Feb to Mar gain was 1.75 - towards the lower end of the distribution. 1993 (1.74), 1995 (1.52), were lower making 2015 Feb to Mar gain the third lowest on record.

Looking at the actual area today it is essentially the same as it was this time last year - so If PIOMAS does come up with a 50% cut in Feb volume growth over 2014 (which itself was very low),  it might be a plausible number - albeit an unprecedentedly bad February for the arctic -  but only if the avg. thickness is also now the same as this time last year. This seems a stretch given the weak winter and the low thickness estimates. If the ice is actually thinner, then PIOMAS would need essentially zero Feb growth to avoid coming up with an incredible number for Apr/May.

I'm sorry but I really don't get how you conclude Apr/May was/would be an 'incredible' i.e. unbelievable number. The PIOMAS April volume was as I said above 1.31 higher than in 2014, but area would be uninformative as this is concentrated in the thicker ice of the Central Arctic.

If, OTOH, PIOMAS comes in with the same (already low) Feb & Mar growth that it did in 2014, it can only end with a modeled March-May volume >1m km3 higher than it was last year, which would IMO be astonishing if true, because it would imply faster Feb growth than 2014, on top of thicker ice than 2014, in the presence of higher temperatures than 2014.

February 2015 was colder than 2014, I have attached a difference plot, so the high volume increase from Jan to feb is to be expected.

So all in all, I'm wondering if this might be the year when PIOMAS last-meter uncertainties finally cause it to part company with directly observable reality.

It might be that I am tired (very), but I don't see how this conclusion follows.
Title: Re: Latest PIOMAS update (July)
Post by: ChrisReynolds on July 08, 2015, 07:42:47 PM
iwantatr8,

This is data for 30 June as posted above? And it has just dawned on me that you were successful in downloading the data - did it go smoothly?

Interesting, now to explain what you see, it can be an interesting game. How about a game of throwing the ball where the ball is a question?

If you're interested here's my first throw...

Given the regional pattern of the 2007 crash, and how advanced things were in late June, how do you interpret the high % values for the Chukchi and ESS regions in years following?
Title: Re: Latest PIOMAS update (July)
Post by: iwantatr8 on July 09, 2015, 09:56:20 AM
Chris,

Yes, this is your data from above. no real issues with usage, I just had to transform the data from your nice tables into something my visualization software could handle.

As to the question, it is difficult to interpret the single day data as anything other than a comparison between years, and not a particularly indicative one at that.  The apparent conclusion is that 2007 melt started earlier in the Chukchi and ESS, which when you look at the actual data is clear.  I would say that the most interesting thing about the daily data is the ability to look at the rate of change of each of the different thickness blocks as this tells more about the overall heat input to the different regions, but I'd need more data and available time to do that. [Hat tip to Wipneus for the regional graphs]

Using the rate of change could help identify likely melt scenarios for each region, but as with any of our predictions we are at the mercy of the weather.

The question I (and I suspect most) want to know the answer to is; how will the apparent return of thicker ice in the arctic ocean affect this year's melt?
Title: Re: Latest PIOMAS update (July)
Post by: Entropy101 on July 09, 2015, 12:07:33 PM

Lower September extent leads to greater growth - the growth thickness feedback again.

Why?
It is a statement that I often see, but after years of lurking still do not comprehend from an energy budget point of view.
I would expect that ice growth is mostly depending on the energy in the system. If we have a low September extent we have a lot of energy in the system that needs to get out before we can have substantial ice growth.
Same if we have a warmer than average winter. Again we have an energy system that is not favourable for ice growth.
Additional energy is also entering the Arctic in winter due to higher sea water temperatures in the gulf stream and other currents.
So why do we expect a large volume growth when we reach a low September extent if we have a energy system that is not in equilibrium and an Arctic where the average winter temperatures are increasing significantly?

Back to lurking now.....
Title: Re: Latest PIOMAS update (July)
Post by: oren on July 09, 2015, 05:36:38 PM

Lower September extent leads to greater growth - the growth thickness feedback again.

Why?
It is a statement that I often see, but after years of lurking still do not comprehend from an energy budget point of view.
I would expect that ice growth is mostly depending on the energy in the system. If we have a low September extent we have a lot of energy in the system that needs to get out before we can have substantial ice growth.
Same if we have a warmer than average winter. Again we have an energy system that is not favourable for ice growth.
Additional energy is also entering the Arctic in winter due to higher sea water temperatures in the gulf stream and other currents.
So why do we expect a large volume growth when we reach a low September extent if we have a energy system that is not in equilibrium and an Arctic where the average winter temperatures are increasing significantly?

Back to lurking now.....

In very simplified unscientific terms, since winter is cold enough and long enough, all open water in the arctic ocean basin will become ~2m first-year ice at the end of winter. So the lower the Sep extent, the higher the volume growth back to FYI cover. Doesn't mean the actual volume will be higher than the previous year, but the growth will be.
Title: Re: Latest PIOMAS update (July)
Post by: plinius on July 09, 2015, 06:00:47 PM
should point out though that this picture may go bad when there is too much loss. If you store too much heat in the ocean you might fail to develop a full winter ice cover. (so there are some claims about such a hysteresis in the sea ice cover). It all hinges on how much energy you can lose throughout the winter. Given the fact that the arctic already now has some troubles to freeze in fall, I would consider that not entirely absurd.
Title: Re: Latest PIOMAS update (July)
Post by: Nick_Naylor on July 09, 2015, 06:29:05 PM
It can also be reduced by high amounts of snow cover, insulating the newborn first year ice.
Title: Re: Latest PIOMAS update (July)
Post by: ChrisReynolds on July 09, 2015, 06:42:25 PM

Lower September extent leads to greater growth - the growth thickness feedback again.

Why?
It is a statement that I often see, but after years of lurking still do not comprehend from an energy budget point of view.
I would expect that ice growth is mostly depending on the energy in the system. If we have a low September extent we have a lot of energy in the system that needs to get out before we can have substantial ice growth.
Same if we have a warmer than average winter. Again we have an energy system that is not favourable for ice growth.
Additional energy is also entering the Arctic in winter due to higher sea water temperatures in the gulf stream and other currents.
So why do we expect a large volume growth when we reach a low September extent if we have a energy system that is not in equilibrium and an Arctic where the average winter temperatures are increasing significantly?

Back to lurking now.....

Oren has already answered it but...

Calculate the autumn/winter month to month PIOMAS volume changes for 1979 to 2015, get the preceding September extent data for each year. Then take each annual series of month to month volume gain, and the series of September minimum and calculate as interannual averages.

So for each month you have a series of interannual differences in volume increase, and you have interannual difference in the preceding September extent. Correlation of the resulting timeseries has the following result.

Nov   -0.592   99.95% confidence
Dec   -0.685   99.95% confidence
Jan   -0.575   99.95% confidence
Feb   -0.656   99.95% confidence
Mar   -0.452   99.5% confidence
Apr   -0.471   99.5% confidence

In other words, as the September extent goes down the autumn/winter volume gains go up, and this can be asserted with high confidence. Note that I just had to work this out because it is so obvious I have not kept a spreadsheet with this data.

You might then proceed to think that this is interesting.

You could examine the physics of sea ice growth.
http://dosbat.blogspot.co.uk/2015/01/the-simplest-model-of-sea-ice-growth.html (http://dosbat.blogspot.co.uk/2015/01/the-simplest-model-of-sea-ice-growth.html)

And from that you could transform your simple model in terms of growth as a function of initial thickness.
http://dosbat.blogspot.co.uk/2015/01/the-slow-transition-thickness-growth.html (http://dosbat.blogspot.co.uk/2015/01/the-slow-transition-thickness-growth.html)

You would find a very good agreement with what a complex model like PIOMAS reproduces, and that where the agreement fails other processes are at work.

If you want to understand things from an energy budget point of view you must do the physics and use the maths to develop understanding. Trying just to reason with words will invariably result in the wrong answer.

Title: Re: Latest PIOMAS update (July)
Post by: ChrisReynolds on July 09, 2015, 06:47:15 PM
Plinius,

The ability of the ocean to vent heat to the atmosphere in the cold of winter after the sun goes down must not be underestimated. Heat flux from leads measured in winter has been observed to be over 1kW/m^2. Even 2012 with very late refreeze then went on to the largest volume gain from September to April.

Title: Re: Latest PIOMAS update (July)
Post by: NeilT on July 09, 2015, 10:40:53 PM
Chris,  here is my problem with PIOMAS and let me see if I can get it exactly right.

If we take the season from 2011 maximum to 2011 minimum, to 2012 maximum, to 2012 minimum, to 2013 maximum.

Then we compare max PIOMAS
Then we go to the CT area and confirm the comparable maximum area and the comparable minimum area in the following

2011 max/min
2012 max/min
2013 max

We should be able to see the corresponding volume loss of the 2012 huge extra melt reflected in the 2013 max ice PIOMAS.

Because whatever we melted more than the 2011 minimum must have been more than first year ice.  Let us be generous and say 2.5m instead of 2m FYI which will be created to replace that which was lost in that 2012 record area minimum.

Let's be even more generous and assume that the difference between 2012 max area and 2013 max area (2013 being bigger), is actually MYI instead of FYI.  I'm doing this because it makes the calculations easier for me.

What we should see, were PIOMAS estimating correctly, is the difference between the MYI area lost in the exceptional melt and the FYI ice area which replaced it at the 2013 max.

Follow me so far?

So to the calculations.

2011 Max area was 12.99m mkm^2 on April 6th
2011 Min area was 2.9899m mkm^2 on 24 Aug

2012 Max area was 13.70m mkm^2 on  on 28 March
2012 Min area was 2.6399m mkm^2 on on 26 Sept

2013 Max area was 13.79m mkm^2 on on 26 Feb
Although this area peaked again at 13.79 on 14 Mar

OK so to PIOMAS
 
2011 max volume was 22.5mkm^3 average for April
2012 max volume was 23.11mkm^3 average for April
2013 max volume was 23.12mkm^3 average for April

Now here's the thing that blows me away and makes me fail to trust PIOMAS

2011 - 2012 I can understand.  It was clearly more volume and it was roughly in April that the volume was largest.

OK so why 2013

2012 had an area low 350kkm^2 lower than 2011.  That means that 350kkm^2 of MYI melted to be replaced with FYI.

OK on my rules above, 2013 was 90kkm^2 higher than 2012 so we remove that and get a figure of 260kkm^2 more FYI than MYI in the 2013 maximum, compared to the 2012 maximum.

So at the postulated 0.5m thickness, that's 130kkm^3 additional volume lost in the 2012 summer melt which has to be replaced by the 2013 re-freeze.

OK, again, that is within the bounds of variance for a colder winter.  Except that the winter was exceptionally slow to start for 2012/13 in terms of area.  2012 was lower than 2011 almost all the way to the year end.  2013 started much lower than 2012 until mid Jan where they crossed over.

Which means, the FYI in 2013 was thinner than the FYI in 2012.

So I don't understand how we get a max ice volume some 10kkm^3 larger than 2012.  All logic tells me that it should be at least the 130kkm^3 lower if not more because of the slow FYI generation.  Although I could be wrong on that.

Finally I can't align the PIOMAS data with the area calculations over the months.

2013 peaked on Feb 26th then remained high till Mar 14th.  It then fell from that date all the way to the end of April.  In fact April ended 1.85mkm^2 lower than the 14th March maximum.

Yet the PIOMAS figures for Feb, Mar and April 2013 were 19.318,   21.964 and 23.122 respectively.

The only answer I have for this is "It's a model".

But my point is this.  If it can get that situation wrong, then what did it do with the rest of it and since.  It may be that the averaging mechanism within the model does balance out.

But here's the final kicker.  A lot of what melted out in 2012 was not 2.5m ice. There was a lot of 3,4 and 5 year ice vanished that year.  It wasn't 350*0.5 It was a hell of a lot more.  Also it was not predominantly 2m FYI ice which replaced the lost ice from 2012 but a lot of 1M and 1.5M ice at the periphery.  I do recall that because of this very thin ice there was an expectation that 2014 would be another serious loss year.

If we add all this together, it should mean that PIOMAS by now is seriously off in it's calculation.

Or I got it all wrong and there is a simple explanation as to why FYI on a short warm winter can replace all the MYI volume lost in an exceptional melt year????


 
Title: Re: Latest PIOMAS update (July)
Post by: Tor Bejnar on July 09, 2015, 11:36:58 PM
Part of the answer is probably how much did or did not get exported during each winter.  See Chris's
You would find a very good agreement with what a complex model like PIOMAS reproduces, and that where the agreement fails other processes are at work.
Title: Re: Latest PIOMAS update (July)
Post by: NeilT on July 10, 2015, 12:03:50 AM
As Neven said on the latest updates.  There was HUGE export in 2012 and much of it was old MYI.  I remember that myself.
Title: Re: Latest PIOMAS update (July)
Post by: anotheramethyst on July 10, 2015, 07:33:22 AM
Chris,  here is my problem with PIOMAS and let me see if I can get it exactly right.

If we take the season from 2011 maximum to 2011 minimum, to 2012 maximum, to 2012 minimum, to 2013 maximum.

Then we compare max PIOMAS
Then we go to the CT area and confirm the comparable maximum area and the comparable minimum area in the following

2011 max/min
2012 max/min
2013 max

We should be able to see the corresponding volume loss of the 2012 huge extra melt reflected in the 2013 max ice PIOMAS.

Because whatever we melted more than the 2011 minimum must have been more than first year ice.  Let us be generous and say 2.5m instead of 2m FYI which will be created to replace that which was lost in that 2012 record area minimum.

Let's be even more generous and assume that the difference between 2012 max area and 2013 max area (2013 being bigger), is actually MYI instead of FYI.  I'm doing this because it makes the calculations easier for me.

What we should see, were PIOMAS estimating correctly, is the difference between the MYI area lost in the exceptional melt and the FYI ice area which replaced it at the 2013 max.

Follow me so far?

So to the calculations.

2011 Max area was 12.99m mkm^2 on April 6th
2011 Min area was 2.9899m mkm^2 on 24 Aug

2012 Max area was 13.70m mkm^2 on  on 28 March
2012 Min area was 2.6399m mkm^2 on on 26 Sept

2013 Max area was 13.79m mkm^2 on on 26 Feb
Although this area peaked again at 13.79 on 14 Mar

OK so to PIOMAS
 
2011 max volume was 22.5mkm^3 average for April
2012 max volume was 23.11mkm^3 average for April
2013 max volume was 23.12mkm^3 average for April

Now here's the thing that blows me away and makes me fail to trust PIOMAS

2011 - 2012 I can understand.  It was clearly more volume and it was roughly in April that the volume was largest.

OK so why 2013

2012 had an area low 350kkm^2 lower than 2011.  That means that 350kkm^2 of MYI melted to be replaced with FYI.

OK on my rules above, 2013 was 90kkm^2 higher than 2012 so we remove that and get a figure of 260kkm^2 more FYI than MYI in the 2013 maximum, compared to the 2012 maximum.

So at the postulated 0.5m thickness, that's 130kkm^3 additional volume lost in the 2012 summer melt which has to be replaced by the 2013 re-freeze.

OK, again, that is within the bounds of variance for a colder winter.  Except that the winter was exceptionally slow to start for 2012/13 in terms of area.  2012 was lower than 2011 almost all the way to the year end.  2013 started much lower than 2012 until mid Jan where they crossed over.

Which means, the FYI in 2013 was thinner than the FYI in 2012.

So I don't understand how we get a max ice volume some 10kkm^3 larger than 2012.  All logic tells me that it should be at least the 130kkm^3 lower if not more because of the slow FYI generation.  Although I could be wrong on that.

Finally I can't align the PIOMAS data with the area calculations over the months.

2013 peaked on Feb 26th then remained high till Mar 14th.  It then fell from that date all the way to the end of April.  In fact April ended 1.85mkm^2 lower than the 14th March maximum.

Yet the PIOMAS figures for Feb, Mar and April 2013 were 19.318,   21.964 and 23.122 respectively.

The only answer I have for this is "It's a model".

But my point is this.  If it can get that situation wrong, then what did it do with the rest of it and since.  It may be that the averaging mechanism within the model does balance out.

But here's the final kicker.  A lot of what melted out in 2012 was not 2.5m ice. There was a lot of 3,4 and 5 year ice vanished that year.  It wasn't 350*0.5 It was a hell of a lot more.  Also it was not predominantly 2m FYI ice which replaced the lost ice from 2012 but a lot of 1M and 1.5M ice at the periphery.  I do recall that because of this very thin ice there was an expectation that 2014 would be another serious loss year.

If we add all this together, it should mean that PIOMAS by now is seriously off in it's calculation.

Or I got it all wrong and there is a simple explanation as to why FYI on a short warm winter can replace all the MYI volume lost in an exceptional melt year????

it does seem strange.  in my infantile understanding of all this, ice volume appears to be among the harder characteristics to measure, and i've seen a lot of dubious looking claims about bolyme and ice thickness.

that said, i don't think you should throw the model away out of hand.  i was under the impression that one of the reasons 2012 was possible was that there were large volume drops in 2010 or 2011.  second, open water freezes faster and thicker than water covered with thin or low quality ice.  people on this forum have shown that detrended data reveals no correlation between arctic maximum and minimum, and i see no reason to believe a minimum would predict the following maximum.  six months is just too long for one single variable to have an affect in such a dynamic system.

all the models and measurements have their flaws.  the best we can do is take all the info from multiple sources and use them to construct a "most likely" picture of the arctic right now.  if piomas isn't working for u today, don't use it, but that doesn't mean u should stop checking it altogether.  six months from now, it might be the most accurate model, you just never know.
Title: Re: Latest PIOMAS update (July)
Post by: Michael Hauber on July 10, 2015, 10:40:12 AM
Perhaps the amount of melt in the next month or two will give an indication of how accurate PIOMAS is.  PIOMAS suggests that current volume and thickness is similar to 2007.  Currently weather conditions seem about as extreme as 2007.  If PIOMAS is correct and conditions continue we should see a minimum about 2007 levels.  If PIOMAS is seriously overestimating volume then we may see a final extent/area minimum like 2012 or even lower.
Title: Re: Latest PIOMAS update (July)
Post by: plinius on July 10, 2015, 04:07:29 PM
Plinius,

The ability of the ocean to vent heat to the atmosphere in the cold of winter after the sun goes down must not be underestimated. Heat flux from leads measured in winter has been observed to be over 1kW/m^2. Even 2012 with very late refreeze then went on to the largest volume gain from September to April.

@Chris: This is exactly the point! Just the other way round. Currently the heat flux per area of leads is high because they feed a bitingly cold and dry atmosphere.  However, we are not talking leads, but a 10Mio. sqkm open patch of ocean. If I did not toss away some units: If you now assume that through that boundary of about 10000km the air in the ground layer flows in with a height of roughly 1 km, I get that the total heat loss from that would be around 1W per m/s and K of that flow. Not so big any more...

The radiative losses are what will likely dominate an ice free arctic, since you have troubles bringing so much cold air in. So, how large are those radiative losses? The net upwelling radiation from a water layer near freezing is less than 300 W/m^2.  If you protect that thing with a fog layer at -10 celsius, you end up somewhere around 50W/m^2. With that kind of assumption you are at 90 days to produce 1m of ice... If you create such a huge open basin, you have to examine the prediction very closely how much radiative loss you still produce.

We have already seen smaller things like the Hudson bay troubled to freeze over. Will be way worse if the arctic is open and has time to accumulate heat during the summer months.
Title: Re: Latest PIOMAS update (July)
Post by: Nick_Naylor on July 10, 2015, 06:07:39 PM
The net upwelling radiation from a water layer near freezing is less than 300 W/m^2.  If you protect that thing with a fog layer at -10 celsius, you end up somewhere around 50W/m^2. With that kind of assumption you are at 90 days to produce 1m of ice...

The problem is once you have 1/4 meter of ice (20 days?), you no longer have open water, so what does that mean for the fog layer?
Title: Re: Latest PIOMAS update (July)
Post by: Steven on July 10, 2015, 06:28:49 PM
Which means, the FYI in 2013 was thinner than the FYI in 2012.

No.  The first-year ice in spring 2013 was thicker than the FYI in spring 2012.

The first several months of 2013 were relatively cold compared to recent years in the Arctic (e.g. see here (http://www.esrl.noaa.gov/psd/cgi-bin/data/timeseries/timeseries.pl?ntype=1&var=Air+Temperature&level=2000&lat1=70&lat2=90&lon1=0&lon2=360&iseas=1&mon1=0&mon2=4&iarea=1&typeout=2&Submit=Create+Timeseries) for the January to May average).  Sea level pressure was relatively high, so probably there were clear skies most of the time.  And I guess snow depth was relatively low.  That means conditions were favorable for sea ice volume growth during winter/spring 2013.

See also Neven's 2012/2013 Winter Analysis (http://neven1.typepad.com/blog/2013/04/20122013-winter-analysis.html).

CryoSat agrees with PIOMAS in this case, in the sense that it agrees that sea ice volume in spring 2013 was similar to spring 2012.  E.g. see here (http://www.arctic.noaa.gov/reportcard/sea_ice.html) (scroll down to the section about sea ice thickness):

With these assumptions, updated radar freeboard and sea-ice thickness maps of the CryoSat-2 data product from the Alfred Wegner Institute (Fig. 4.4) show an increase in average freeboard of 0.05 m in March 2014 compared to the two preceding years (2012: 0.16 m, 2013: 0.16 m, 2014: 0.21 m). This amounts to an increase of mean sea-ice thickness of 0.38 m (2012: 1.97 m, 2013: 1.97 m, 2014: 2.35 m). The mean values were calculated for an area in the central Arctic Ocean where the snow climatology is considered to be valid. Excluded are the ice-covered areas of the southern Barents Sea, Fram Strait, Baffin Bay and the Canadian Arctic Archipelago.

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fi.imgur.com%2FZwZCZGj.jpg&hash=0c7c59b4b1c1d12b2af90375025e9f79)
Title: Re: Latest PIOMAS update (July)
Post by: ChrisReynolds on July 10, 2015, 06:45:31 PM
Plinius,

The ability of the ocean to vent heat to the atmosphere in the cold of winter after the sun goes down must not be underestimated. Heat flux from leads measured in winter has been observed to be over 1kW/m^2. Even 2012 with very late refreeze then went on to the largest volume gain from September to April.

@Chris: This is exactly the point! Just the other way round. Currently the heat flux per area of leads is high because they feed a bitingly cold and dry atmosphere.  However, we are not talking leads, but a 10Mio. sqkm open patch of ocean. If I did not toss away some units: If you now assume that through that boundary of about 10000km the air in the ground layer flows in with a height of roughly 1 km, I get that the total heat loss from that would be around 1W per m/s and K of that flow. Not so big any more...

The radiative losses are what will likely dominate an ice free arctic, since you have troubles bringing so much cold air in. So, how large are those radiative losses? The net upwelling radiation from a water layer near freezing is less than 300 W/m^2.  If you protect that thing with a fog layer at -10 celsius, you end up somewhere around 50W/m^2. With that kind of assumption you are at 90 days to produce 1m of ice... If you create such a huge open basin, you have to examine the prediction very closely how much radiative loss you still produce.

We have already seen smaller things like the Hudson bay troubled to freeze over. Will be way worse if the arctic is open and has time to accumulate heat during the summer months.

At some stage in the latter part of this century this will be very significant, and the winter ice will be in serious decline. But even with the staggering warming of recent years the decline in winter freezing degree days is relatively modest.

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2F1.bp.blogspot.com%2F--3c7nAjdSVE%2FVLQpb8Y9PeI%2FAAAAAAAABZM%2Fiq3KuHJ0sOM%2Fs1600%2FFDDs.png&hash=cd53e77bfae1673db93f00ab163a9623)

This results in a modest decline in equilibrium thickness for thermodynamic growth from open water (Sept to April). Note that the limiting factor in ice growth is not currently time needed to grow, it is the winter cold.

Take this graphic from Thorndike 1975.
(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Ffarm4.staticflickr.com%2F3824%2F9586307013_77132e9dd4_o.jpg&hash=f79a0214528038d3c8256d0c57a5032f)

Note how massive the growth rate from open water to 1m thick ice is. This is a result of the massive heat flux through thinner ice, and is then limited as the ice grows thicker. This is so powerful that weather and late freeze factors have a relatively small impact on peak winter ice thickness.
Title: Re: Latest PIOMAS update (July)
Post by: Andreas T on July 10, 2015, 06:50:51 PM
Plinius,

The ability of the ocean to vent heat to the atmosphere in the cold of winter after the sun goes down must not be underestimated. Heat flux from leads measured in winter has been observed to be over 1kW/m^2. Even 2012 with very late refreeze then went on to the largest volume gain from September to April.

@Chris: This is exactly the point! Just the other way round. Currently the heat flux per area of leads is high because they feed a bitingly cold and dry atmosphere.  However, we are not talking leads, but a 10Mio. sqkm open patch of ocean. If I did not toss away some units: If you now assume that through that boundary of about 10000km the air in the ground layer flows in with a height of roughly 1 km, I get that the total heat loss from that would be around 1W per m/s and K of that flow. Not so big any more...

The radiative losses are what will likely dominate an ice free arctic, since you have troubles bringing so much cold air in. So, how large are those radiative losses? The net upwelling radiation from a water layer near freezing is less than 300 W/m^2.  If you protect that thing with a fog layer at -10 celsius, you end up somewhere around 50W/m^2. With that kind of assumption you are at 90 days to produce 1m of ice... If you create such a huge open basin, you have to examine the prediction very closely how much radiative loss you still produce.

We have already seen smaller things like the Hudson bay troubled to freeze over. Will be way worse if the arctic is open and has time to accumulate heat during the summer months.
My doubt about that fog layer in arctic night is that the top of the layer radiates out to space at its temperature which either is as cold as the top of the ice is now which probably means precipitation or it is warmer and radiates more strongly requiring more heat input from below to stay at that temperature.
These are the reasons why people have developed models, there are interdependent processes at work which can't be quantified in isolation.
Title: Re: Latest PIOMAS update (July)
Post by: ChrisReynolds on July 10, 2015, 07:05:58 PM
Neil T,

I'm having problems following what you are trying to say, so sorry if I get it wrong.

Does it all come down to:

1) Winter 2013 should have reflected the volume loss in 2012.
2) You can't align area and volume.
3) PIOMAS volume goes up when area declines after March.

If I am correct in that presumption your answers are:

1) The growth thickness feedback.

2) You can only align volume and area using thickness, and you'll get nowhere with CT Area. It produces weird 'compactness' as shown in CAPIE, and I found very quickly that while NSIDC Extent and Area work fairly neatly with PIOMAS (though not perfectly), CT Area is quite bonkers - that's why I stopped using it! The best way to use PIOMAS and area is to use their area.h and .heff files for area (concentration of ice) and thickness respectively.

3) Area loss from March onwards comes from thin ice outside the Arctic Ocean, meanwhile the Arctic Ocean is still sub zero and volume of ice within the Arctic Ocean continues to increase after the area maximum. Indeed the volume within the Central Arctic peaks in May!
Title: Re: Latest PIOMAS update (July)
Post by: Gray-Wolf on July 10, 2015, 08:31:56 PM
Quick question. How well does the PIOMAS team cope with 'rotten ice'? We've all seen the floes from the 'aloft cam' come late August so we know some pretty raggerty ice makes it through the year ( to be in filled with FY ice over winter) so would we not expect the FY ice to melt out leaving the old carcass behind? Would this not leave a lot of 'Swiss cheese ice' over July/Aug? Would such not mean the volume tends high over such regions?
Title: Re: Latest PIOMAS update (July)
Post by: plinius on July 10, 2015, 08:40:08 PM
Chris: Your point of massive growth rates from Thorndike 1975 is null, since that is simply based on a cold arctic and single patches. Of course you lose giant amounts of heat from a lead or a small patch of thin ice. I would also say that a loss of ~10% of the freezing degree days that we have seen is _massive_, given the fact that current ice conditions have only very moderately affected the heat balance of the ocean.

@AndreasT: As far as I know the model situation is not fully conclusive concerning those parameters. Just too far out of our normal experience (and that of the models) and also quite a close call in energy balance, if there is a stable winter ice equilibrium. Look for Langlaufer's stuff, among other things.
Title: Re: Latest PIOMAS update (July)
Post by: jdallen on July 10, 2015, 08:47:25 PM
Neil T,

I'm having problems following what you are trying to say, so sorry if I get it wrong.

Does it all come down to:

1) Winter 2013 should have reflected the volume loss in 2012.
2) You can't align area and volume.
3) PIOMAS volume goes up when area declines after March.

If I am correct in that presumption your answers are:

1) The growth thickness feedback.

2) You can only align volume and area using thickness, and you'll get nowhere with CT Area. It produces weird 'compactness' as shown in CAPIE, and I found very quickly that while NSIDC Extent and Area work fairly neatly with PIOMAS (though not perfectly), CT Area is quite bonkers - that's why I stopped using it! The best way to use PIOMAS and area is to use their area.h and .heff files for area (concentration of ice) and thickness respectively.

3) Area loss from March onwards comes from thin ice outside the Arctic Ocean, meanwhile the Arctic Ocean is still sub zero and volume of ice within the Arctic Ocean continues to increase after the area maximum. Indeed the volume within the Central Arctic peaks in May!
The major problem is, our instrumentation to measure thickness directly is very sparse, and the tools we have to gather it by inference (e.g. Satellite microwave) subject to high degrees of variability.   Extent and area can be directly measured, volume only inferred. As a result, our confidence intervals are quite broad.

I'm sure the people taking the measurements are quite aware of it, and the significantly diverging estimates of thickness and volume by various institutions is mute testament to it.

Those estimate will tend to close up as our sampling increases and tools improve, but until then we will have to accept both uncertainty and occasional surprises.
Title: Re: Latest PIOMAS update (July)
Post by: ktonine on July 10, 2015, 09:14:28 PM
Extent and area can be directly measured, volume only inferred.

It would be an interesting endeavor to do so, but alas we do not measure either directly.  We infer ice concentration/extent/area from satellite measurements of brightness temperature. At least 7 different algorithms have been used to try and differentiate ice from water using brightness temperature as a proxy.

Perhaps when the remaining ice is down to a single floe we can send a surveying team out to measure the area directly.
Title: Re: Latest PIOMAS update (July)
Post by: Neven on July 10, 2015, 09:16:56 PM
But they'll have to hurry...
Title: Re: Latest PIOMAS update (July)
Post by: ChrisReynolds on July 10, 2015, 10:09:09 PM
Quick question. How well does the PIOMAS team cope with 'rotten ice'? We've all seen the floes from the 'aloft cam' come late August so we know some pretty raggerty ice makes it through the year ( to be in filled with FY ice over winter) so would we not expect the FY ice to melt out leaving the old carcass behind? Would this not leave a lot of 'Swiss cheese ice' over July/Aug? Would such not mean the volume tends high over such regions?

PIOMAS assimilates concentration of sea ice from NSIDC.
Title: Re: Latest PIOMAS update (July)
Post by: ChrisReynolds on July 10, 2015, 10:11:01 PM
Chris: Your point of massive growth rates from Thorndike 1975 is null, since that is simply based on a cold arctic and single patches. Of course you lose giant amounts of heat from a lead or a small patch of thin ice. I would also say that a loss of ~10% of the freezing degree days that we have seen is _massive_, given the fact that current ice conditions have only very moderately affected the heat balance of the ocean.

 ::)
Title: Re: Latest PIOMAS update (July)
Post by: jdallen on July 10, 2015, 11:40:13 PM
Extent and area can be directly measured, volume only inferred.

It would be an interesting endeavor to do so, but alas we do not measure either directly.  We infer ice concentration/extent/area from satellite measurements of brightness temperature. At least 7 different algorithms have been used to try and differentiate ice from water using brightness temperature as a proxy.

Perhaps when the remaining ice is down to a single floe we can send a surveying team out to measure the area directly.
Hah! True enough; that said, the granularity of those samples provides far higher precision than we have when measuring volume.

I like your reply as well, Neven...
Title: Re: Latest PIOMAS update (July)
Post by: iceman on July 11, 2015, 01:22:26 PM
In recent years the volume anomaly has consistently bottomed in late June or July.  2015 could be an exception, with several factors pointing toward an extended decline:
   -  sustained heat over the MYI north of Canadian Archipelago
   -  fragmentation around the big floes in Beaufort
   -  winds pushing other thick ice near the Atlantic edge into Kara and Barents
   -  an uptick in Fram export a week or so from now
   -  a lobe in southern Laptev that looks to be cut off from the main pack in a few weeks
   -  and as Neven mentioned on the blog, easy ice left in Hudson and Baffin Bay
My guess is for a low in August, with volume anomaly dropping in between the 2010 and 2013 traces.
Title: Re: Latest PIOMAS update (July)
Post by: plinius on July 13, 2015, 04:28:37 PM
Well, the one thing with which PIOMAS could really give a good view on the detailed quality of the model is publishing the necessary ex post corrections. I.e. statistics about where and how much the ice has to be removed from the model, where it has really melted out, and where and how much it melts out in the model, but not in reality. Not aware that such statistics would exist publicly, correct?
Title: Re: Latest PIOMAS update (July)
Post by: NeilT on July 13, 2015, 06:04:05 PM
Neil T,

I'm having problems following what you are trying to say, so sorry if I get it wrong.

Does it all come down to:

1) Winter 2013 should have reflected the volume loss in 2012.
2) You can't align area and volume.
3) PIOMAS volume goes up when area declines after March.

If I am correct in that presumption your answers are:

1) The growth thickness feedback.

2) You can only align volume and area using thickness, and you'll get nowhere with CT Area. It produces weird 'compactness' as shown in CAPIE, and I found very quickly that while NSIDC Extent and Area work fairly neatly with PIOMAS (though not perfectly), CT Area is quite bonkers - that's why I stopped using it! The best way to use PIOMAS and area is to use their area.h and .heff files for area (concentration of ice) and thickness respectively.

3) Area loss from March onwards comes from thin ice outside the Arctic Ocean, meanwhile the Arctic Ocean is still sub zero and volume of ice within the Arctic Ocean continues to increase after the area maximum. Indeed the volume within the Central Arctic peaks in May!

Hi Chris,

Yes that does answer it for me.  Although I'd challenge the part about

Area loss from March onwards comes from thin ice outside the Arctic Ocean, meanwhile the Arctic Ocean is still sub zero and volume of ice within the Arctic Ocean continues to increase after the area maximum

Because if you need that area to create volume, then if it's really thin how did we get to a volume higher than 2012??  Given that much MYI was melted and flushed in 2012 and replaced with FYI.

FYI simply can't be MYI, there is not enough time for it to melt.

But, in general, you've answered my question.  PIOMAS is using a different area calc which would give different values which would tend to change the results.

I still think it's overestimating volume when significant portions of MYI are melted or flushed and replaced with FYI.  But, I guess, over time it would tend to average out if we didn't get another deep melt back.

I'll answer Steven separately.
Title: Re: Latest PIOMAS update (July)
Post by: NeilT on July 13, 2015, 06:09:13 PM

The mean values were calculated for an area in the central Arctic Ocean where the snow climatology is considered to be valid. Excluded are the ice-covered areas of the southern Barents Sea, Fram Strait, Baffin Bay and the Canadian Arctic Archipelago.

Thanks for your post Steven.  But the conclusion I take from this is that the CAB, where the MYI melted, was replaced with slightly thicker FYI.

On the other hand, the other areas, which had a very short ice growth season, apparently, made up the rest of the lost MYI volume.

It doesn't make sense to me.  But I'm going to head back into watch mode.

I see almost the entire CAB in melt right now with huge intrusion into the CAB from the Pacific side.  Time will tell but the melt season is certainly under way in a big way.  What it results in will come down to both weather and current thickness.
Title: Re: Latest PIOMAS update (July)
Post by: epiphyte on July 14, 2015, 06:34:32 AM
@ChrisReynolds - Thanks for following up on my post a few days back and apologies for not responding earlier...  real life is getting in the way of my ability to spend time on this stuff.

I stand corrected on the historical Feb-Mar growth numbers. What I should have said was that in the post 2000 period the modeled Feb-March gain has almost always been >~ 2M. Nonetheless, eyeballing the graph again, I can only see one 2000-2014 year (2003) when it was significantly less than that - so I think the point still has some validity..

  [...] 2015 was 1.75, not unusal. Lower September extent leads to greater growth - the growth thickness feedback again.

It still seems to me that that 1.75 *is* unusual -  later on you yourself mention that it is the third lowest on record  - and the lowest since 1995,

In other words, the January number is high enough to guarantee that the April number will be more than a million km3 *higher* than it was in 2014, absent worse than existing worst-case behavior in February and March.


Yes, it was 1.31 higher.

So we just lived through Feb - and to my eyes at least it looked as though it might indeed have have been the worst ever. Assume that PIOMAS cuts it's previous worst-case Feb growth in half (i.e. from ~2.5 to ~1.25m). If it did that the Feb number would be the same as it was last year.

Sorry, you lost me here, but February volume was 23.21, Jan Feb gain was 3.01 not unusual, Feb to Mar gain was 1.75 - towards the lower end of the distribution. 1993 (1.74), 1995 (1.52), were lower making 2015 Feb to Mar gain the third lowest on record.

Isn't it interesting though that 1995 went on to have a (then) record low Sep volume, as did 1993 - the other low Feb-Mar growth year which you call out above.

Even more interesting is that for both years the modeled September volume was much lower than the previous year (~2.3m - 2.5m below 1992 and 1994, respectively). I think I'm right in saying that 1981 is the only Sep-Sep drop larger than 2.5. apart from those two.

I'm sorry but I really don't get how you conclude Apr/May was/would be an 'incredible' i.e. unbelievable number. The PIOMAS April volume was as I said above 1.31 higher than in 2014, but area would be uninformative as this is concentrated in the thicker ice of the Central Arctic.

I think area is relevant because it enables a distinction between FYI growth and MYI growth. I think that the numbers are incredible because they require MYI to grow more quickly than it should.

2015 Sep volume was 1.5 higher than 2014.

If the starting and ending areas are the same and the and the starting volume was higher in year 2, then given the same weather conditions:

     1. the Overall volume growth should be less in year 2
     2. the FYI volume (i.e. FYI volume growth) should be the same for years 1 & 2
     3. the ending volume should be > ( starting volume + FYI volume) in both years.

what I was trying to say at the end of Feb was that in order to satisfy all of the above for the period sep 2014 - apr 2015, PIOMAS would need to come up with numbers which seemed inconsistent with either it's past behavior, or observed conditions at the time, or both.

you posted a temp. anomaly plot showing colder temps at the edges and warmer temps at the center - which IMO should disproportionately increase FYI over MYI growth, exacerbating the above. (mind you... I'm tired too :O )
Title: Re: Latest PIOMAS update (July)
Post by: ChrisReynolds on July 14, 2015, 10:06:02 PM
Neil, Epiphyte,

I'm sorry, but I hope you don't mind if I let your comments stand and don't address them. I've got a lot of maths to do for a project at work, and the sea ice is going to be a case of sit back and enjoy for the next few weeks.
Title: Re: Latest PIOMAS update (July)
Post by: NeilT on July 15, 2015, 08:38:41 PM
Not in the slightest Chris. For me this is an interest and a diversion.  As a former analyst I just look at stuff and if it does not seem to make sense I ask why I can't make it make sense and keep asking questions to get my point over until I do understand why.

Work, as always, takes precedence.  Good luck with that.

Title: Re: Latest PIOMAS update (July)
Post by: Benje on July 25, 2015, 10:01:51 PM
One thing that I think is important is how much ice volume we are losing each year....not just sea ice but from Greenland too ....because when we have lost the sea ice, if the same (or more!) annual heat is available in the area then we may expect the losses from Greenland to increase very rapidly: giving rise to much more sea level rise than we have seen up to now.

So I would like to see a combined graph of the total volume losses by year and, in an ideal world, with the sea level impact shown on one of the scales - perhaps from 2015 onwards (as well as the km cubed or GT values).

The losses from Greenland, say, since 2004 have been more than 3000Gt according to the  website
http://polarportal.dk/en/groenlands-indlandsis/nbsp/total-masseaendring/ (http://polarportal.dk/en/groenlands-indlandsis/nbsp/total-masseaendring/)

The losses on Piomass since 2004 are between 3000 and 7000 km cubed per Wipneus (see below)...depending on which year!

I know it is to some extent using different sources of data for volume but isn't there a way to see the whole-loss picture.

I know that someone like Wipneus - or Chris or many other readers on this forum- would make a whole lot better job than me of combining the two.
Benje

https://14adebb0-a-62cb3a1a-s-sites.googlegroups.com/site/arctischepinguin/home/piomas/grf/piomas-trnd1.png?attachauth=ANoY7crpwhX-tfsSveSDHms2wPtbpPzWPYgjsNX0KJHC-w-_1_AScdyWtTapfJmQ_R3_s3Ez4x-FLeN2igsL0Ifhy8sQXjXt7tHGKOL9FbmjIezUaCBt1XJ4_S-uT7dKzPrdhA3JMzxyv7CA2MM_Me6YLcjew0G6jcbjVXdn5vp2L3sUuxsKK0cO_9JJQ802vipavkAEDQv8DGFpIdNvCQKtKlDvAg0UcGmssn3UZhmBbSQk7cDCUbKG-MMSWEdZTwStrV79t0Dy&attredirects=0 (https://14adebb0-a-62cb3a1a-s-sites.googlegroups.com/site/arctischepinguin/home/piomas/grf/piomas-trnd1.png?attachauth=ANoY7crpwhX-tfsSveSDHms2wPtbpPzWPYgjsNX0KJHC-w-_1_AScdyWtTapfJmQ_R3_s3Ez4x-FLeN2igsL0Ifhy8sQXjXt7tHGKOL9FbmjIezUaCBt1XJ4_S-uT7dKzPrdhA3JMzxyv7CA2MM_Me6YLcjew0G6jcbjVXdn5vp2L3sUuxsKK0cO_9JJQ802vipavkAEDQv8DGFpIdNvCQKtKlDvAg0UcGmssn3UZhmBbSQk7cDCUbKG-MMSWEdZTwStrV79t0Dy&attredirects=0)
Title: Re: Latest PIOMAS update (July)
Post by: crandles on July 26, 2015, 12:23:54 AM
Aren't they rather different.

Sea ice volume in 2012 ranged from around 22k down to 4k km^3. When we have lost the sea ice in summer the range is then going to be from approx 19k down to 0 km^3 so instead of losing 18k km^3 we have extra heat which results in losing an extra 1k km^3 of sea ice and maybe the extra heat is a little more than 1k km^3 of ice melt resulting in some spill over into higher temperatures and more ice lost from greenland.

Adding different items together loses the detail.

The projections from climate models are that the losses of sea ice decline in rate as we approach virtually ice free. (Winters are long and cold and it is easy to build sea ice up to 20k km^3 in a winter if you start from having none.)

Whereas for Greenland we are talking increases in the rate of loss possibly even doubling every 10 years for a number of decades.

I suggest they are so different and have such different projected futures it really makes no sense at all to add them together.
Title: Re: Latest PIOMAS update (July)
Post by: Benje on July 26, 2015, 08:00:06 AM
Hi Crandles
Thanks for those comments
I was thinking of the (graphically) simpler situation of year on year loss. For example if the sea ice minumum movement year on year was added to the Greenland loss year on year then the true scale of ice loss over the years would be evident (its pretty much the same ice although the sea ice does have a bit of extra salt).
Benje
Title: Re: Latest PIOMAS update (July)
Post by: Neven on July 26, 2015, 11:52:03 AM
Greenland is losing 300 gigatonnes of ice on average. It doesn't grow back during winter, unlike sea ice. How much km3 is that? And how much km3 is average annual sea ice loss?

Other rather important point: When ice melts on Greenland, there's ice below it. When ice melts on the Arctic Ocean, there's open water below it.

My gut says the difference is orders of magnitude. Much more ice melts on Greenland, but sea ice loss causes much more albedo decrease. But that's my gut.
Title: Re: Latest PIOMAS update (July)
Post by: Peter Ellis on July 26, 2015, 12:16:10 PM
1 Gt is ~1.09 km^3 of ice.  To a first approximation we can just call that 1:1, which means Greenland is currently losing ~300 km^3 of ice per year.
http://www.sealevel.info/conversion_factors.html (http://www.sealevel.info/conversion_factors.html)
Title: Re: Latest PIOMAS update (July)
Post by: Neven on July 26, 2015, 12:21:40 PM
1 Gt is ~1.09 km^3 of ice.  To a first approximation we can just call that 1:1, which means Greenland is currently losing ~300 km^3 of ice per year.
http://www.sealevel.info/conversion_factors.html (http://www.sealevel.info/conversion_factors.html)

That's what I feared. So 300 km3 for Greenland that doesn't come back, and 20 km3 for sea ice that does come back. It's not useful to combine the two, Benje! But it never hurts to ask.  :)
Title: Re: Latest PIOMAS update (July)
Post by: Peter Ellis on July 26, 2015, 12:27:49 PM
The annual cycle for sea ice is of the order of 15-20 thousand km^3.

It's fairly intuitive to work out that the sea ice volume changes dwarf the changes on the Greenland ice sheet.

1)  The area of the Arctic ocean is much larger than the area of Greenland
2)  The thickness of Arctic sea ice changes by an average of a metre or more across the seasonal cycle
3)  The thickness of the Greenland ice cap doesn't fluctuate nearly that much during the seasonal cycle
Title: Re: Latest PIOMAS update (July)
Post by: Peter Ellis on July 26, 2015, 12:34:09 PM
However, the question was more about trends than the seasonal cycle.

Current trend in sea ice volume is a loss of 3000 km^3 per decade = 300 km^3 per year. So the year-on-year trend in Arctic sea ice volume is pretty much equal to the year-on-year trend in Greenland ice cap volume.  Nifty!
http://psc.apl.uw.edu/wordpress/wp-content/uploads/schweiger/ice_volume/BPIOMASIceVolumeAnomalyCurrentV2.1.png (http://psc.apl.uw.edu/wordpress/wp-content/uploads/schweiger/ice_volume/BPIOMASIceVolumeAnomalyCurrentV2.1.png)

I think it's very misleading though to suggest that when the Arctic "bottoms out" at a summer volume of zero, there will be any neat numerical link to subsequent changes in GIS volume.  It's even plausible that GIS volume will go up for a while, due to extra moisture from Arctic evaporation leading to more snow deposition on Greenland.
Title: Re: Latest PIOMAS update (July)
Post by: Neven on July 26, 2015, 12:40:43 PM
The annual cycle for sea ice is of the order of 15-20 thousand km^3.

So much for my gut!  ;D

God, I'm stupid.  :-[
Title: Re: Latest PIOMAS update (July)
Post by: Tensor on July 26, 2015, 02:54:42 PM
So much for my gut!  ;D

I can send some antacids.

 
  God, I'm stupid.  :-[

Not even close.
Title: Re: Latest PIOMAS update (July)
Post by: Benje on July 27, 2015, 04:35:13 PM
Thanks Peter for your comments and helpful clarifactions.

Obviously the future is tough to forecast ....whatever models or methods are used.

But history has happened and although difficult to measure, either the Greenland icesheet or the sea ice, "we" try pretty hard to understand the data we have. And the history is relevant, I suggest, with regard to the scale of heat (and scale of consequential ice loss) and with regard to the way that it is trending...accelerating  (which is what I think most of us fear) or whatever.

It is also relevant to look at both together because  the gross loss from Greenland divides into water run off and ice ...which becomes sea ice. It is probably difficult to measure the ice component but we can be sure that the accelerarting glaciers now provide an increasingly  material contrbution to the (now diminishing) sea ice volume.

I know that there might be more precipitation as snow on Greenland in a given year due to warmer moist air but it is the ice underneath which offers 7 metres of sea level rise (when melted) that is the big player here surely. Extra lubrication of the glaciers and inundation of the valleys with warm(ish) water in Greenland will surly hurry the ice decline.

I think that we should be very concerned that the absence of sea ice  will very soon allow substantial  latent heat absorbtion (previously by the sea ice as was)  to be transferred to the additional warming and ice loss from the Greenland ice sheet.

That's why I would like to see a chart of the two together: trouble is, I feel sure that I lack the skills of many of you to access and make compatible the appropriate data and to show the results in a complelling form. Absent any offers though, I will take it on but can anyone steer me to pre2004 data for the Greenland Ice sheet mass ...in an easy to access format?
Benje
Title: Re: Latest PIOMAS update (July)
Post by: Peter Ellis on July 27, 2015, 11:59:28 PM
I don't think there's any plausible mechanism whereby increased latent heat absorption by the Arctic Ocean can be transferred simply to cause additional ice loss from the Greenland ice sheet.  Can you give me a good reason why slightly warmer waters offshore in Barrow (say) should cause snowmelt in Cape Morris Jesup?
Title: Re: Latest PIOMAS update (July)
Post by: Siffy on July 28, 2015, 12:11:33 AM
I don't think there's any plausible mechanism whereby increased latent heat absorption by the Arctic Ocean can be transferred simply to cause additional ice loss from the Greenland ice sheet.  Can you give me a good reason why slightly warmer waters offshore in Barrow (say) should cause snowmelt in Cape Morris Jesup?

Presumably it wouldn't if I'm right in where I think Barrow is, presumably however an earlier ice free Baffin bay would mean warmer hotter water beside Greenland and subsequently warmer hotter air that could blow over into greenland.

Writ large on for instance a potential year which is ice free by the start of August presumably that could have a large effect on greenlands melt due to the increased amount of heat picked up by the ocean no?

Title: Re: Latest PIOMAS update (July)
Post by: greatdying2 on July 28, 2015, 02:10:07 AM
I don't think there's any plausible mechanism whereby increased latent heat absorption by the Arctic Ocean can be transferred simply to cause additional ice loss from the Greenland ice sheet.  Can you give me a good reason why slightly warmer waters offshore in Barrow (say) should cause snowmelt in Cape Morris Jesup?

Presumably it wouldn't if I'm right in where I think Barrow is, presumably however an earlier ice free Baffin bay would mean warmer hotter water beside Greenland and subsequently warmer hotter air that could blow over into greenland.

Writ large on for instance a potential year which is ice free by the start of August presumably that could have a large effect on greenlands melt due to the increased amount of heat picked up by the ocean no?
Not to mention direct ice-sheet/ocean interactions: http://www.whoi.edu/science/PO/people/fstraneo/ice-sheet-ocean-interactions (http://www.whoi.edu/science/PO/people/fstraneo/ice-sheet-ocean-interactions) .
Title: Re: Latest PIOMAS update (July)
Post by: crandles on July 28, 2015, 12:03:15 PM
Presumably it wouldn't if I'm right in where I think Barrow is, presumably however an earlier ice free Baffin bay would mean warmer hotter water beside Greenland and subsequently warmer hotter air that could blow over into greenland.

But why not continue that and say where that warmer moister air gets colder and snows out the moisture?

Which effect dominates extra melting at the edges or extra snow in the interior?
Title: Re: Latest PIOMAS update (July)
Post by: nukefix on July 28, 2015, 01:28:35 PM
Absent any offers though, I will take it on but can anyone steer me to pre2004 data for the Greenland Ice sheet mass ...in an easy to access format?
Benje
Here's some, haven't looked at the format though:

http://imbie.org/data-downloads/ (http://imbie.org/data-downloads/)
Title: Re: Latest PIOMAS update (July)
Post by: Benje on July 29, 2015, 08:40:52 PM
Thanks Nukefix: its an excel spreadsheet; perfect for me.
Benje
Title: Re: Latest PIOMAS update (July)
Post by: Neven on August 02, 2015, 12:32:39 PM
Now that the month is done (well, almost for the daily composites page (http://www.esrl.noaa.gov/psd/data/composites/day/)), I decided to try and get a feel for which July is most comparable to July 2015. For my July analysis I have downloaded sea level pressure and temperature anomaly maps for 2007, 2010, 2011, 2012, 2013 and 2014. But July 2015 has been much warmer and sunnier, only 2007 comes somewhat close.

And so I decided to have a look at the biggest July droppers according PIOMAS (in km3):

2006: 5990
2007: 6421
2008: 6187
2009: 6750
2010: 6053
2011: 5938
2012: 5619
2013: 6245
2014: 5057

2007 was warmest and sunniest in my analysis, but it looks like 2009 was the biggest July dropper in the past decade. So, off I went to get the SLP and SAT maps, and here's how July 2007 and 2009 compare to July 2015 (up to July 30th):

(https://lh3.googleusercontent.com/-ADvSlsI1RYA/Vb3qec8JnMI/AAAAAAAACgo/DhhBDie1eUQ/s640-Ic42/SAT%252520%25252B%252520SLP%252520July%2525202007%25252C%2525202009%25252C%2525202015.gif)

July 2015 temperature anomaly is comparable to 2007, whereas average sea level pressure is similar to 2009. But overall July 2015 was sunniest and warmest in the 2006-2015 record, with the heat and sun smack in the middle of the area where ice is supposed to be thickest.

And so I expect PIOMAS to put July 2015 at a volume loss of at least 6500 km3, which will put it around 1000 km3 below 2014, and close the gaps with 2011, 2012, 2013.

Of course, it's 2013 that I'm interested in, as I've written a guest article (http://www.theguardian.com/environment/climate-consensus-97-per-cent/2015/jul/29/2015-arctic-melting-season-wont-break-records-but-could-wipe-the-recovery) for the Guardian website, stating that the rebound could be wiped out. This depends on August weather conditions, but also melting momentum, of course. 2013 lost relatively little volume during August.

If 2015 slips under 2013 by September, it's going to be tight.
Title: Re: Latest PIOMAS update (July)
Post by: Yuha on August 03, 2015, 10:40:36 AM
And so I decided to have a look at the biggest July droppers according PIOMAS (in km3):

2006: 5990
2007: 6421
2008: 6187
2009: 6750
2010: 6053
2011: 5938
2012: 5619
2013: 6245
2014: 5057

2007 was warmest and sunniest in my analysis, but it looks like 2009 was the biggest July dropper in the past decade.

...

July 2015 temperature anomaly is comparable to 2007, whereas average sea level pressure is similar to 2009. But overall July 2015 was sunniest and warmest in the 2006-2015 record, with the heat and sun smack in the middle of the area where ice is supposed to be thickest.

This is supported by the mean temperatures in Alert:

     June July
2006 -0.6  3.7
2007 -0.4  2.4
2008  1.7  4.6
2009 -2.4  5.3
2010 -0.3  5.5
2011  2.9  2.9
2012  2.0  4.3
2013  0.7  2.3
2014 -2.2  1.8
2015  1.6  5.5
Avg   0.3  3.8


July 2015 was the warmest July tied with 2010.
And 2015 has had the warmest summer so far (June+July).
Title: Re: Latest PIOMAS update (July)
Post by: Nick_Naylor on August 03, 2015, 01:35:42 PM
You really have to throw out 2007 and 2009 though.  Once you do that, the correlation is pretty good ;)
Title: Re: Latest PIOMAS update (August)
Post by: Wipneus on August 04, 2015, 08:16:51 AM
New PIOMAS data is available. I have updated my graphs, see the top post (http://forum.arctic-sea-ice.net/index.php/topic,119.0.html).

(I did not see any updated gridded data yet. The thickness (change) maps will have to wait)
Title: Re: Latest PIOMAS update (July)
Post by: Neven on August 04, 2015, 08:20:11 AM
And so I expect PIOMAS to put July 2015 at a volume loss of at least 6500 km3, which will put it around 1000 km3 below 2014, and close the gaps with 2011, 2012, 2013.

And a drop of 6659 km3 it is. 2015 is now 809 km3 behind 2013, down from 1223 km3 last month. Oh, and 971 km3 below 2014.
Title: Re: Latest PIOMAS update (July)
Post by: seaicesailor on August 04, 2015, 03:00:44 PM
And so I expect PIOMAS to put July 2015 at a volume loss of at least 6500 km3, which will put it around 1000 km3 below 2014, and close the gaps with 2011, 2012, 2013.

And a drop of 6659 km3 it is. 2015 is now 809 km3 behind 2013, down from 1223 km3 last month. Oh, and 971 km3 below 2014.

lol. Isn't it funny, that PIOMAS usually triggers a lot of reactions immediately? It is as if nobody was surprised of this, the way things are unfolding right now.
Title: Re: Latest PIOMAS update (August)
Post by: plinius on August 04, 2015, 03:46:27 PM
Rather surprised that the model did not produce a larger decrease.
Title: Re: Latest PIOMAS update (July)
Post by: oren on August 04, 2015, 05:01:15 PM
And so I expect PIOMAS to put July 2015 at a volume loss of at least 6500 km3, which will put it around 1000 km3 below 2014, and close the gaps with 2011, 2012, 2013.

And a drop of 6659 km3 it is. 2015 is now 809 km3 behind 2013, down from 1223 km3 last month. Oh, and 971 km3 below 2014.

You nailed it.
Title: Re: Latest PIOMAS update (August)
Post by: Wipneus on August 04, 2015, 05:53:10 PM
The monthly gridded data are available, still waiting for the daily values.

Here are the thickness maps of July 2014 and 2015 and the differences.

Again: these are average monthly thicknesses.
Title: Re: Latest PIOMAS update (August)
Post by: Wipneus on August 04, 2015, 05:58:31 PM
Same as above: thickness 2012 and the difference between July 2015-2012
Title: Re: Latest PIOMAS update (August)
Post by: Nightvid Cole on August 04, 2015, 06:50:53 PM
Same as above: thickness 2012 and the difference between July 2015-2012

The "2012" July thickness map looks just like the 2014 map. Did you copy the 2014 hyperlink again accidentally?
Title: Re: Latest PIOMAS update (August)
Post by: greatdying2 on August 04, 2015, 07:15:32 PM
Rather surprised that the model did not produce a larger decrease.
Ditto.
Title: Re: Latest PIOMAS update (July)
Post by: Neven on August 04, 2015, 07:20:50 PM
lol. Isn't it funny, that PIOMAS usually triggers a lot of reactions immediately? It is as if nobody was surprised of this, the way things are unfolding right now.

Oh, I'm quite surprised to see how much July can make up for May and June.

Here's the latest PIOMAS update (http://neven1.typepad.com/blog/2015/08/piomas-august-2015.html) over on the ASIB, BTW.
Title: Re: Latest PIOMAS update (August)
Post by: ChrisReynolds on August 04, 2015, 10:36:42 PM
I need to see the daily data to see how things have evolved over July. But here is the series of monthly differences from within the Central Arctic for the 2015 - 2012 difference.

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2F1.bp.blogspot.com%2F-3v2fioXwstg%2FVcD5VBrB-SI%2FAAAAAAAACcM%2FOfZhUd00JQw%2Fs1600%2FVol%252BDelta%252Bprogression.png&hash=eef3edf6f27084dea025edd3fb432a86)

In the July average most of the 2012 to 2015 volume difference is still in the Central Arctic, specifically from grid boxes in that region with an effective thickness of between 3.0 and 3.9m.

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2F4.bp.blogspot.com%2F-sh0INBLGSWs%2FVcD5VySBVjI%2FAAAAAAAACcg%2FL1FyNf-QPYg%2Fs1600%2FVolume%252BDelta%252B2012.png&hash=20813b32db3f7fdbeac808e1baea4e30)
Title: Re: Latest PIOMAS update (August)
Post by: plinius on August 04, 2015, 10:42:51 PM
Again, without the adhoc corrections, an assessment of the model isn't really feasible. And PIOMAS is not making those public.
Title: Re: Latest PIOMAS update (August)
Post by: Wipneus on August 05, 2015, 08:32:39 AM
Same as above: thickness 2012 and the difference between July 2015-2012

The "2012" July thickness map looks just like the 2014 map. Did you copy the 2014 hyperlink again accidentally?

Yes, I should be more careful changing code just before shutting down for the day.

Thanks, corrected now.
Title: Re: Latest PIOMAS update (July)
Post by: plinius on August 05, 2015, 12:15:47 PM
lol. Isn't it funny, that PIOMAS usually triggers a lot of reactions immediately? It is as if nobody was surprised of this, the way things are unfolding right now.

Oh, I'm quite surprised to see how much July can make up for May and June.

Here's the latest PIOMAS update (http://neven1.typepad.com/blog/2015/08/piomas-august-2015.html) over on the ASIB, BTW.

Neven, you cannot assume that this is genuine melt. If there is no ice left in the data, my take is that PIOMAS simply zeroes it out. Which means that what you consider melt will to some part be just model adjustments.
Title: Re: Latest PIOMAS update (August)
Post by: Benje on August 10, 2015, 10:49:03 AM
With help from Dugeonmasrter and Neven (for which many thanks) I can show how I have at last added the Greenland ice loss (from year low to year low) to the Sea ice loss (year low to year low). It is not a profound concept...it is just the change of Ice in the Artic....and it is not well done (I could only estimate by eye the greenland loss from the Danish site but the errors would at least not be cumulative.

But even this simple graph shows the overall position in a different way. Obviously the Greenland loss is (in general but not including 2013 and 2014) increasing rapidly and in 2015 the direction of travel will likely resume.

I know there are many skeptics about the concept of Greenland ice being as it were interchangeable with sea ice...or to look at it the other way round when the sea ice is gone that Greenland will melt as much as the sea ice would have if it had been there. Nevertheless, the history is real and as to the future, we will see.
Anyway, I hope it is of interest to some
Benje
Title: Re: Latest PIOMAS update (August)
Post by: JayW on August 10, 2015, 11:41:38 AM
With help from Dugeonmasrter and Neven (for which many thanks) I can show how I have at last added the Greenland ice loss (from year low to year low) to the Sea ice loss (year low to year low). It is not a profound concept...it is just the change of Ice in the Artic....and it is not well done (I could only estimate by eye the greenland loss from the Danish site but the errors would at least not be cumulative.

But even this simple graph shows the overall position in a different way. Obviously the Greenland loss is (in general but not including 2013 and 2014) increasing rapidly and in 2015 the direction of travel will likely resume.

I know there are many skeptics about the concept of Greenland ice being as it were interchangeable with sea ice...or to look at it the other way round when the sea ice is gone that Greenland will melt as much as the sea ice would have if it had been there. Nevertheless, the history is real and as to the future, we will see.
Anyway, I hope it is of interest to some
Benje

I had trouble with the pdf, so I turned it into a jpeg so others could see it.

Title: Re: Latest PIOMAS update (August)
Post by: Neven on August 10, 2015, 12:03:42 PM
Thanks, Benje and JayW.
Title: Re: Latest PIOMAS update (August)
Post by: Benje on August 10, 2015, 10:00:12 PM
Thanks JayW
Title: Re: Latest PIOMAS update (July)
Post by: ChrisReynolds on August 11, 2015, 07:09:36 PM
lol. Isn't it funny, that PIOMAS usually triggers a lot of reactions immediately? It is as if nobody was surprised of this, the way things are unfolding right now.

Oh, I'm quite surprised to see how much July can make up for May and June.

Here's the latest PIOMAS update (http://neven1.typepad.com/blog/2015/08/piomas-august-2015.html) over on the ASIB, BTW.

Neven, you cannot assume that this is genuine melt. If there is no ice left in the data, my take is that PIOMAS simply zeroes it out. Which means that what you consider melt will to some part be just model adjustments.

Plinius,

I don't see the sea ice concentration assimilation as being as problematic as you do. Do you view the assimilation of weather as being a problem?
Title: Re: Latest PIOMAS update (August)
Post by: ChrisReynolds on August 11, 2015, 08:14:09 PM
Gice daily and heff daily are now available. Frankly, they're a bit boring. Losses from 1 June to 1 July are high, but not exceptional on the whole.

Because they're boring I can't be bothered putting my other plans aside to blog tonight, but here are some raw data if anyone wants to see it. Volume for regions in km^3.

Posted as formatted text in a txt file, should copy into a spreadsheet OK. Table of 30 June volumes, 31 July volumes, and table of loss between those dates. All by region.
Title: Re: Latest PIOMAS update (July)
Post by: plinius on August 11, 2015, 10:56:54 PM
I don't see the sea ice concentration assimilation as being as problematic as you do. Do you view the assimilation of weather as being a problem?

Not the concentration assimilation per se. With my incomplete understanding, there should be a lot of real information about model performance in the residuals that come from the assimilation. In simple terms: Ice melts out and this melt-out contrasts with predictions from the model, when it should happen, i.e. a running validation (or invalidation) of the model, that would tell at any time about tendency to under- or overestimate the ice volume in the concerned regions.
Title: Re: Latest PIOMAS update (August)
Post by: Richard Rathbone on August 12, 2015, 01:56:48 AM
http://psc.apl.uw.edu/research/projects/arctic-sea-ice-volume-anomaly/validation/ (http://psc.apl.uw.edu/research/projects/arctic-sea-ice-volume-anomaly/validation/)

This sort of thing.
Title: Re: Latest PIOMAS update (July)
Post by: ktonine on August 12, 2015, 02:36:30 AM
Not the concentration assimilation per se. With my incomplete understanding, there should be a lot of real information about model performance in the residuals that come from the assimilation. In simple terms: Ice melts out and this melt-out contrasts with predictions from the model, when it should happen, i.e. a running validation (or invalidation) of the model, that would tell at any time about tendency to under- or overestimate the ice volume in the concerned regions.

Running validation?  Ummm .... if we had running data on thickness we wouldn't have to rely on models :)

We have a few buoys, obviously, but we can't really claim they're representative of the ice in their vicinity - much less extrapolate to the entire sea ice area.  It's expensive, time-consuming, and pretty much unrealistic to expect a running validation. 

Title: Re: Latest PIOMAS update (July)
Post by: crandles on August 12, 2015, 03:00:53 AM

Not the concentration assimilation per se. With my incomplete understanding, there should be a lot of real information about model performance in the residuals that come from the assimilation. In simple terms: Ice melts out and this melt-out contrasts with predictions from the model, when it should happen, i.e. a running validation (or invalidation) of the model, that would tell at any time about tendency to under- or overestimate the ice volume in the concerned regions.

Note I am a complete amateur, this is all just speculation and am probably getting this completely wrong.

Comparing piomas thickness to actual thickness is difficult because the actual measurements are too sparse and have their own uncertainties. Assimilation corrections are different to this and it may be interesting to see information on these.

There will be lots of unders and overs in every region. If there was a lot of information in this e.g. a high ratio of one way to the other, do you think the modellers wouldn't have used that information to tweak the parameters of the model? I would assume they have in effect done that with optimising their hindcasts. After this is done, the unders and overs would tend to approach similar levels in each region so I doubt there would be much real information at this point.

However, if the system has been running for two or three years since the last time a hindcast and twiddle with the parameters to minimise those assimilation errors (and other comparisons to thickness data) was done, then there could be new information emerging. I wouldn't assume this will be a vastly important, the data might well look like lots of random pluses and minuses that is very difficult to distinguish whether any changes in ratio of +s' to -s' is all just random fluctuations or if there is any emerging trend contained therein.

While you may well not be able to deduce anything from such data, I think there might be circumstances where interesting information could emerge:
Suppose the PIOMAS model has a tendency to change ice volume towards say 2009 ice volume levels. Running a hindcast up to say 2011, most years in the hindcast would be years when the starting volume was higher than where the model tends to want to go so the model would naturally reduce volume as happened. There would be relatively few years with the current situation of volume less than 2009 levels where the model tends to increase or keep the ice volume fairly level. If this isn't what the ice is actually doing, then there might be radically different assimilation errors in the recent years than in the hindcast training period. These radically different assimilation errors might in these sort of situations be very interesting. However reality may not be close to this scenario which I created to try to explain a circumstance where the assimilation errors might be interesting.

Perhaps other people think differently to this?
Note I am a complete amateur and am probably getting this completely wrong.
Title: Re: Latest PIOMAS update (July)
Post by: epiphyte on August 12, 2015, 07:08:47 AM

Running validation?  Ummm .... if we had running data on thickness we wouldn't have to rely on models :)


That's true - but I think inapposite to plinius' point. If PIOMAS is forcing modeled thickness to zero when observed thickness drops to zero, it would be very interesting to know where and when it was doing that, and what the modeled thickness was before it was zeroed out. That would let us know if there are systematic errors which are being systematically eliminated whenever they would otherwise come to light...

Title: Re: Latest PIOMAS update (July)
Post by: Richard Rathbone on August 12, 2015, 02:51:31 PM

Running validation?  Ummm .... if we had running data on thickness we wouldn't have to rely on models :)


That's true - but I think inapposite to plinius' point. If PIOMAS is forcing modeled thickness to zero when observed thickness drops to zero, it would be very interesting to know where and when it was doing that, and what the modeled thickness was before it was zeroed out. That would let us know if there are systematic errors which are being systematically eliminated whenever they would otherwise come to light...

You don't know when it drops to zero. The measurements are too noisy.  If you actually did do this sort of forcing you'd be driving the model with the noise (like the Navy were).
Title: Re: Latest PIOMAS update (July)
Post by: crandles on August 12, 2015, 03:03:57 PM

You don't know when it drops to zero. The measurements are too noisy.  If you actually did do this sort of forcing you'd be driving the model with the noise (like the Navy were).

http://psc.apl.washington.edu/research/projects/arctic-sea-ice-volume-anomaly/ (http://psc.apl.washington.edu/research/projects/arctic-sea-ice-volume-anomaly/)
Model and Assimilation Procedure

PIOMAS is a numerical model with components for sea ice and ocean and the capacity for assimilating some kinds of observations. For the ice volume simulations shown here, sea ice concentration information from the NSIDC near-real time product are assimilated into the model to improve ice thickness estimates

So they are doing that and they obviously believe it helps or they wouldn't be doing it.

What does your '(like the Navy were)' comment mean?
Title: Re: Latest PIOMAS update (July)
Post by: Jim Hunt on August 12, 2015, 06:58:02 PM
What does your '(like the Navy were)' comment mean?

I assume Richard is referring to this?

http://forum.arctic-sea-ice.net/index.php/topic,1320 (http://forum.arctic-sea-ice.net/index.php/topic,1320)
Title: Re: Latest PIOMAS update (July)
Post by: ChrisReynolds on August 12, 2015, 07:26:42 PM
I don't see the sea ice concentration assimilation as being as problematic as you do. Do you view the assimilation of weather as being a problem?

Not the concentration assimilation per se. With my incomplete understanding, there should be a lot of real information about model performance in the residuals that come from the assimilation. In simple terms: Ice melts out and this melt-out contrasts with predictions from the model, when it should happen, i.e. a running validation (or invalidation) of the model, that would tell at any time about tendency to under- or overestimate the ice volume in the concerned regions.

I understand that, and yes a trend or shifts to greater adjustments might be instructive. However it might not tell us just about model bias. Consider a grid cell, concentration is applied from satellite data and this causes the model to deduct a certain volume. Has this volume been lost because the model physics are wrong? Has it been lost because of difference between atmospheric forcings and actual weather? Here small changes in NCEP/NCAR cloud fraction may play a large role. What of ocean heat? How much ocean data is available to identify what role that plays.

In the end the assimilation of concentration, and atmospheric data play a role of keeping the physics in check and instead of the model free-running, pulling it more in line with a key observational measure of sea ice (concentration). My suspicion is that the bias is always towards loss when melt is underway and towards gain when growth is underway.

'Training' of the PIOMAS model was done in the past, mainly using DRA submarine transect data and ICESat data from Ron Kwok. As I understand it, the datasets were broken down in time and area. One set was used to adjust unkown parameters to better match the data. Then the model was verified against the second set to see how well it tracked those observations in hindcast. The switch to PIOMAS V2 was not such an adjiustment, they had a similar problem to that experienced by ACNFS this year, but the impact was very small.

Have you asked the PSC team or Dr Zhang if this data can be made available?
Title: Re: Latest PIOMAS update (August)
Post by: Wipneus on August 13, 2015, 05:41:14 PM
Daily gridded thick was also released. Here is the July melt as a sequence.

(click req'd)
Title: Re: Latest PIOMAS update (August)
Post by: ChrisReynolds on August 13, 2015, 07:14:26 PM
Summary of July losses.
http://dosbat.blogspot.co.uk/2015/08/piomas-volume-loss-over-july.html (http://dosbat.blogspot.co.uk/2015/08/piomas-volume-loss-over-july.html)

Data derived from gridded PIOMAS is now updated.
http://dosbat.blogspot.co.uk/2013/12/regional-piomas-volume-data.html (http://dosbat.blogspot.co.uk/2013/12/regional-piomas-volume-data.html)
Title: Re: Latest PIOMAS update (August)
Post by: Tor Bejnar on August 13, 2015, 08:41:57 PM
I just looked at past (crossed out) data and graphs at the top of this thread (page 1, introductory comment). Last year the minimum PIOMAS ice volume was about 2.7M less than the July 31 volume.  A 2.7M reduction for 2015 would bring volume to below 6.0M km3. On the first graph, this would put a point 1.5M above the suggested trend curve (projecting ice free in 2020), halving the discrepancy of the 2014 minimum.

There are feedbacks that will cause a long tail (ice free much later) and feedbacks that are pushing for a quick melt.  The show goes on!
Title: Re: Latest PIOMAS update (August)
Post by: Nick_Naylor on August 14, 2015, 12:39:55 PM
Daily gridded thick was also released. Here is the July melt as a sequence.

Looking at July 31, it looks like PIOMAS is overestimating the ice in the Beaufort region, showing thick ice in some areas where the concentration was very low. Makes me wonder how quickly/frequently it assimilates concentration. Those sparse floes would have to be unbelievably thick for the average thickness to exceed two meters in the area i highlighted.
Title: Re: Latest PIOMAS update (August)
Post by: oren on August 14, 2015, 01:30:41 PM
Daily gridded thick was also released. Here is the July melt as a sequence.

Looking at July 31, it looks like PIOMAS is overestimating the ice in the Beaufort region, showing thick ice in some areas where the concentration was very low. Makes me wonder how quickly/frequently it assimilates concentration. Those sparse floes would have to be unbelievably thick for the average thickness to exceed two meters in the area i highlighted.

It made me wonder too. Looking at that big area of open water between the highlighted area and the CAA, on PIOMAS it's not showing up at all. What do the experts say about this?
Title: Re: Latest PIOMAS update (August)
Post by: Neven on August 29, 2015, 04:43:02 PM
Has anyone been wondering yet what monthly decrease PIOMAS will report next week? I know I have.  :)

Just like last month I've been trying to get a feel for what's possible by looking at average August weather conditions in previous years. I made this temperature+sea level pressure map, with years following a ranking based on PIOMAS monthly loss (the loss in km3 is noted below the year in question), with 2015 at the bottom:

(https://lh3.googleusercontent.com/-jKxmqIunH8E/VeHB6vW7_gI/AAAAAAAACkA/o5LRXioeg5Q/s640-Ic42/SAT-SLP%252520comparison%252520August%252520PIOMAS.png)

When it comes to SLP, 2015 resembles 2011 most, but 2011 had higher average temperatures over the CAB. 2011 lost 2372 km3 during August, but at the same time 2011 had 1625 km3 less volume at the start of August compared to this year.

Temeprature-wise 2015 looks similar to 2009, but 2009 had much stronger cyclone activity during August. Mind you, 2015 runs only up to August 26th, so the recent cyclone might still change the average somewhat, although not much I expect. 2009 lost 2578 km3 during August, but also had 1209 km3 more volume than this year at the start of August.

Given all this I don't expect August to see a loss of much over 2500 km3, unless PIOMAS has some melting momentum factor from July that bleeds through into August. Of course, a lot of MYI has disappeared during the month, not just the 'arm', but perhaps also in the region where ice is oldest and thickest (north of the CAA), where there has been widespread fragmentation and dispersal in the past couple of weeks. I don't know if PIOMAS has a resolution that picks up on that.

So yeah, I'd say around 2500 km3, not enough to dip below 2013, even though with 2221 km3 it lost relatively little volume during August.
Title: Re: Latest PIOMAS update (September)
Post by: Wipneus on September 05, 2015, 08:01:04 AM
PIOMAS updated the daily volume data. I updated my graphics, see the top post (http://forum.arctic-sea-ice.net/index.php/topic,119.msg1562.html#msg1562)

Monthly gridded data also updated (but not the daily), I will post the graphics later today.
Title: Re: Latest PIOMAS update (September)
Post by: werther on September 05, 2015, 09:47:40 AM
Thanks Wipneus!

Nothing on the PIOMAS site yet, but you bring us the essential. The running monthly average, which has been growing for a while, is dipping again since July. And even steeper during August.
Title: Re: Latest PIOMAS update (September)
Post by: Wipneus on September 05, 2015, 11:25:22 AM
Look again Werther! I noticed the update on the PIOMAS site first.

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fpsc.apl.uw.edu%2Fwordpress%2Fwp-content%2Fuploads%2Fschweiger%2Fice_volume%2FBPIOMASIceVolumeAnomalyCurrentV2.1.png&hash=d75486bc4e09ac0c665a1e839b46b78a)
Title: Re: Latest PIOMAS update (September)
Post by: crandles on September 05, 2015, 12:05:36 PM
The chances of minimum volume in 2013, 2014 and 2015 being above minimum volume of each of 2010, 2011 and 2012 seems pretty slim if the trend is an exponential decline. It could still be noise but this is surely looking unlikely now?
Title: Re: Latest PIOMAS update (September)
Post by: slow wing on September 05, 2015, 12:09:17 PM
Thanks Wipneus, that's very interesting!


With those winds around, I predict it could drop some more in September and the daily minimum could fall below that for 2013.


I can't wait to see the gridded data to see where all the ice remains...  :D :o
Title: Re: Latest PIOMAS update (September)
Post by: Wipneus on September 05, 2015, 12:41:46 PM
The daily gridded thickness data is now available as well. Here is an animation of the thickness development during August.

(Yes, must click to start animation)
Title: Re: Latest PIOMAS update (September)
Post by: Wipneus on September 05, 2015, 01:36:52 PM
Average monthly thickness of August 2015 compared with years 2006-2014. The ice  north of Ellesmere  is anomalous thick compared with all of these years, while the ice right at the pole is comparatively thin.

Click for the wider picture.
Title: Re: Latest PIOMAS update (September)
Post by: slow wing on September 06, 2015, 02:37:36 AM
Interesting that the 2015 melt season started with all that thick multi-year ice on the Pacific side but retains no memory of that in the current ice thickness map, relative to previous years.

Instead, the remaining thick ice is all in the traditional 'thick ice sanctuary' off the Canadian coast. This sanctuary ice is even thicker than in past recent years.

Since I don't have Wipneus' original, here's a screenshot of the thickness map at the end of August...


Title: Re: Latest PIOMAS update (September)
Post by: Adam Ash on September 06, 2015, 04:31:08 AM
As I see it tho, the remaining MYI is in a very different place.  It is now in among the pack, subject to whatever wind and current do with it, and wherever those force send it.

In previous years it was anchored to the land, and comparatively immobile.

So winter circulation of the Beaufort Gyre is likely to rotate this MYI 90 degrees - from the CAA to near the Chukchi, where it is in line to get the same battering ice received there this year. 

And isn't that same rotation of the gyre simply going to pull young ice into that area north of the CAA from north of Greenland.  That's just plain mush, and while you may get some second year ice out of it, the gyre will just roll it on into the Beaufort the year after without a chance to get much thicker?
Title: Re: Latest PIOMAS update (September)
Post by: Peter Ellis on September 06, 2015, 01:58:53 PM
The Arctic ice is pack ice, not fast ice, and is never "anchored" to land.
Title: Re: Latest PIOMAS update (September)
Post by: crandles on September 06, 2015, 03:05:57 PM
With those winds around, I predict it could drop some more in September and the daily minimum could fall below that for 2013.

2015 is above 2013 on day 243 by 401km^3

Recent year drops from day 243 to minimum have been
Year Fall Day243
2007 194 6652
2008 751 7823
2009 396 7235
2010 256 4838
2011 305 4607
2012 259 3932
2013 182 5574
2014 405 7217

So 2013 dropped unusually little after day 243.

Getting below 2013 minimum would require a drop of 401+182=583 km^3

Only one year 2008 dropped more than 583 km^3 from day 243 so maybe not impossible.

However, from 1979 to 2006 largest drop is 452, so 2008 look like an unusual outlier.

Also in the recent years listed, the highest three falls are from highest three values on day 243. This year's day 243 value is not as high at 5975. Maybe there is no such relationship and a big drop this year in September is possible.

In short, not impossible but it looks pretty unlikely.
Title: Re: Latest PIOMAS update (September)
Post by: Neven on September 07, 2015, 08:18:03 AM
Curious as I am, I'm in an Internet cafe right now (I don't have a connection at my holiday address), trying to open the PIOMAS data file, but somehow I can't unpack the .gz file with my usual extraction programme, Extractnow, nor with 7-zip, etc. Anyone experienced the same problems?

Never mind, it suddenly works.

See you next week...
Title: Re: Latest PIOMAS update (September)
Post by: Neven on September 07, 2015, 08:21:51 AM
Given all this I don't expect August to see a loss of much over 2500 km3, unless PIOMAS has some melting momentum factor from July that bleeds through into August.

2629 km3 it is. Interesting...  :)
Title: Re: Latest PIOMAS update (September)
Post by: iceman on September 07, 2015, 01:08:52 PM
Given all this I don't expect August to see a loss of much over 2500 km3, unless PIOMAS has some melting momentum factor from July that bleeds through into August.

2629 km3 it is. Interesting...  :)

It looks like the dip in the anomaly trace came about 23rd-26th August, which would implicate the cyclone (and subsequent accelerated bottom melt) in the larger-than-expected volume decline.
Title: Re: Latest PIOMAS update (September)
Post by: seaicesailor on September 07, 2015, 03:19:49 PM
Given all this I don't expect August to see a loss of much over 2500 km3, unless PIOMAS has some melting momentum factor from July that bleeds through into August.

2629 km3 it is. Interesting...  :)

It looks like the dip in the anomaly trace came about 23rd-26th August, which would implicate the cyclone (and subsequent accelerated bottom melt) in the larger-than-expected volume decline.

Accelerated bottom melt means PIOMAS has some melting momentum factor from August that bleeds through into September.
Title: Re: Latest PIOMAS update (September)
Post by: oren on September 07, 2015, 04:53:25 PM
Given all this I don't expect August to see a loss of much over 2500 km3, unless PIOMAS has some melting momentum factor from July that bleeds through into August.

2629 km3 it is. Interesting...  :)

It looks like the dip in the anomaly trace came about 23rd-26th August, which would implicate the cyclone (and subsequent accelerated bottom melt) in the larger-than-expected volume decline.

Accelerated bottom melt means PIOMAS has some melting momentum factor from August that bleeds through into September.

When I looked at that drop my layman's intuition said that PIOMAS had some thick ice there, but when extent dropped to zero due to the cyclone t had to delete it and thus the sharp volume drop. No idea if this has any merit.
Title: Re: Latest PIOMAS update (September)
Post by: Richard Rathbone on September 07, 2015, 08:54:29 PM
Given all this I don't expect August to see a loss of much over 2500 km3, unless PIOMAS has some melting momentum factor from July that bleeds through into August.

2629 km3 it is. Interesting...  :)

It looks like the dip in the anomaly trace came about 23rd-26th August, which would implicate the cyclone (and subsequent accelerated bottom melt) in the larger-than-expected volume decline.

Accelerated bottom melt means PIOMAS has some melting momentum factor from August that bleeds through into September.

Sunlight goes into the sea heating up the near surface layer during the early part of the season and this mixes upwards to melt ice later in the season. August cyclones can bring it up faster (notably in 2012) and result in melting happening earlier than it otherwise would. On the other hand if the Beaufort Gyre is in full swing, it takes a significant amount of this heat downwards resulting in rather less melting.
Title: Re: Latest PIOMAS update (September Interim)
Post by: Wipneus on September 18, 2015, 07:47:34 AM
PSC has released an interim update for reaching the 2015 minimum (h/t Michael Yorke).

On the official PIOMAS page (http://psc.apl.washington.edu/research/projects/arctic-sea-ice-volume-anomaly/) page they comment:

The sea ice extent minimum for 2015 was likely reached on Sept 11. Sea ice volume minimum was reached a day later with a total volume of 5670 km3 . This  value is about 1200 km3 below the volume minimum of the 2014 which showed a subtantial rebound in ice volume. The value for 2015 is 300 km3 above the value for 2013 and constitutes a continuation of the long-term declining trend (see fig 1) with shorter term  variability in both directions (e.g. 2012 and 2014).

(color: PSC)

Just the volume data is available, not the gridded thickness.
I will update the September minimum graphics shortly.
Title: Re: Latest PIOMAS update (September Interim)
Post by: Wipneus on September 18, 2015, 08:51:32 AM
The September minimum graphics updated with the (prelim) minimum of 2015.

In the bunch of curve fits most projected melt-out ( curve intersects the volume=0 line) dates have increased by about one year.
Title: Re: Latest PIOMAS update (September Interim)
Post by: Wipneus on September 18, 2015, 09:09:21 AM
While you can conclude that most "faster than linear" curve fitting exercises seem to be unreliable forecasters of the final melt-out, a linear fit to the full PIOMAS data shows that the post 2012 "recovery" hardly brings the volume above the projected number. Contrary, the data still shows that the rate of decline is more than linear.
The linear projection predicts that 2012 levels will be the norm in 6-7 years.
Title: Re: Latest PIOMAS update (September Interim)
Post by: Wipneus on September 18, 2015, 09:11:02 AM
For completeness here are the exponential and gompertz fits.
Title: Re: Latest PIOMAS update (September Interim)
Post by: Neven on September 18, 2015, 09:25:59 AM
Thanks, Wipneus!
Title: Re: Latest PIOMAS update (September Interim)
Post by: slow wing on September 18, 2015, 11:05:06 AM
Yep, thanks Wipneus!

Thanks also to the PIOMAS people for releasing the result so promptly. Appreciated!
Title: Re: Latest PIOMAS update (September Interim)
Post by: Richard Rathbone on September 18, 2015, 11:24:58 AM
Is using 1997 as the starting year for the linear fit supported by any method such as change point analysis or similar?
Title: Re: Latest PIOMAS update (September Interim)
Post by: Wipneus on September 18, 2015, 11:40:15 AM
Is using 1997 as the starting year for the linear fit supported by any method such as change point analysis or similar?

No, I did choose (in 2010) a subset to reduce the non-linearity below the noise and still having a reasonable number of points.
That is for the graph with the bunch of curve fits. The other graph with only a the linear fit is calculated over the full set.
Title: Re: Latest PIOMAS update (September Interim)
Post by: Neven on September 18, 2015, 11:47:54 AM
Subtracting the minimum from the maximum, it appears that 2015 had the third biggest annual volume decrease (after 2010 and 2012):

(https://lh3.googleusercontent.com/-m8YZgVWIaN8/Vfvdg-lihvI/AAAAAAAAClo/9SrCd4aOtlA/s656-Ic42/PIOMAS%252520max-min.png)
Title: Re: Latest PIOMAS update (September Interim)
Post by: AmbiValent on September 18, 2015, 12:14:14 PM
Is there also a max-min comparison for max of spring and min of previous fall, to look at the effect of the refreeze season?
Title: Re: Latest PIOMAS update (September Interim)
Post by: Neven on September 18, 2015, 12:20:13 PM
Is there also a max-min comparison for max of spring and min of previous fall, to look at the effect of the refreeze season?

I'm sure there is something out there (probably on the Dosbat blog), but if no one posts anything, I'll try and make another bar graph later today.
Title: Re: Latest PIOMAS update (September Interim)
Post by: Jim Pettit on September 18, 2015, 01:15:36 PM
Is there also a max-min comparison for max of spring and min of previous fall, to look at the effect of the refreeze season?

This isn't exactly what you're asking for, but it may be close. The red line shows the annual volume lost--that is, the difference between max and min. (IOW, it shows the same data that Neven's vertical bar graph does.) The blue line shows, obviously, annual volume maxima, and the grey columns indicate how much ice is left at minimum. That may seem a little backward, but I've shown in this way to better illustrate how, in the not too distant future, there'll likely be years where the blue and the red lines converge. That is, the grey columns will at some point vertically shrink to near zero.

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fi.imgur.com%2F6A20m7d.png&hash=07ed751a02c228985998e244cb260566)
Title: Re: Latest PIOMAS update (September Interim)
Post by: Steven on September 18, 2015, 01:16:55 PM
Is using 1997 as the starting year for the linear fit supported by any method such as change point analysis or similar?

No, I did choose (in 2010) a subset to reduce the non-linearity below the noise and still having a reasonable number of points.
That is for the graph with the bunch of curve fits. The other graph with only a the linear fit is calculated over the full set.

FWIW, the R software package called "segmented (http://www.inside-r.org/packages/cran/segmented/docs/segmented)" (which can be used for change-point analysis) finds a change-point near 1996:

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fi.imgur.com%2FnkK7dSY.png&hash=80b15e715a6361df2d4693ba3096d7a0)
Title: Re: Latest PIOMAS update (September Interim)
Post by: crandles on September 18, 2015, 01:29:13 PM
an old one:

(https://farm6.staticflickr.com/5750/20887985344_21a2b38fff_z.jpg) (https://flic.kr/p/xPNojm)Piomas2.1meltfreeze (https://flic.kr/p/xPNojm) by crandles57 (https://www.flickr.com/photos/37346653@N05/), on Flickr
Title: Re: Latest PIOMAS update (September Interim)
Post by: seaicesailor on September 18, 2015, 01:43:48 PM
Is there also a max-min comparison for max of spring and min of previous fall, to look at the effect of the refreeze season?

I'm sure there is something out there (probably on the Dosbat blog), but if no one posts anything, I'll try and make another bar graph later today.

Subtracting the minimum from the maximum, it appears that 2015 had the third biggest annual volume decrease (after 2010 and 2012):

(https://lh3.googleusercontent.com/-m8YZgVWIaN8/Vfvdg-lihvI/AAAAAAAAClo/9SrCd4aOtlA/s656-Ic42/PIOMAS%252520max-min.png)

Bad season for the Arctic ice, considering what could be called a "relatively cold" season and no Fram export.
Very simplistically, temperature ≠ heat.
Title: Re: Latest PIOMAS update (September)
Post by: seaicesailor on September 18, 2015, 02:02:11 PM
Given all this I don't expect August to see a loss of much over 2500 km3, unless PIOMAS has some melting momentum factor from July that bleeds through into August.

2629 km3 it is. Interesting...  :)

It looks like the dip in the anomaly trace came about 23rd-26th August, which would implicate the cyclone (and subsequent accelerated bottom melt) in the larger-than-expected volume decline.

Accelerated bottom melt means PIOMAS has some melting momentum factor from August that bleeds through into September.

Sunlight goes into the sea heating up the near surface layer during the early part of the season and this mixes upwards to melt ice later in the season. August cyclones can bring it up faster (notably in 2012) and result in melting happening earlier than it otherwise would. On the other hand if the Beaufort Gyre is in full swing, it takes a significant amount of this heat downwards resulting in rather less melting.

I agree. However the first 10 days of September, ocean SST anomalies were significant (+1C) at Beaufort and Chukchi sea. Browse SST anomaly maps thru these days here,

http://ocean.dmi.dk/arctic/satellite/index.uk.php (http://ocean.dmi.dk/arctic/satellite/index.uk.php)

If you browse the Bremen maps until the 10th, you can see some ice melting from Beaufort and Chukchi, especially close to CAA, and the remainders at Chukchi).
The new buoy at CAB (81N), showed bottom melting until the 15th, now flat.

Refreezing starts. Clockwise drift due to prevailing high pressure over Beaufort too*. But I wouldn't be surprised ice front advances slowly during the next weeks.

*Is this drift called Beaufort Gyre too? I had recently learned the Beaufort Gyre is the slower ocean current beneath of much greater inertia, which does not stop flowing clockwise during the whole year, but only strengthens in intensity in Winter due to the mentioned prevailing Winter ice drift.

Title: Re: Latest PIOMAS update (September Interim)
Post by: Neven on September 18, 2015, 02:53:28 PM
Is there also a max-min comparison for max of spring and min of previous fall, to look at the effect of the refreeze season?

I'm sure there is something out there (probably on the Dosbat blog), but if no one posts anything, I'll try and make another bar graph later today.

Here it is, the maximum with the minimum of the previous year subtracted:

(https://lh3.googleusercontent.com/-VENNctvaeco/VfwJDYPseJI/AAAAAAAACmI/cSnfqYUU4bk/s656-Ic42/PIOMAS%252520min-max.png)
Title: Re: Latest PIOMAS update (September Interim)
Post by: crandles on September 18, 2015, 03:11:05 PM
(https://farm6.staticflickr.com/5660/21486235516_5095ee4562_z.jpg) (https://flic.kr/p/yJEzfu)Piomasmaxminmeltfreeze (https://flic.kr/p/yJEzfu) by crandles57 (https://www.flickr.com/photos/37346653@N05/), on Flickr

Includes Sept 2015 estimated at 5.8 K Km^3. (31/8/15 was 5.975 and 15/9/15 5.713 so 5.8 probably isn't far out.)
Title: Re: Latest PIOMAS update (September Interim)
Post by: AmbiValent on September 18, 2015, 03:14:12 PM
Thanks a lot!
Title: Re: Latest PIOMAS update (September Interim)
Post by: jdallen on September 18, 2015, 06:00:31 PM
Is there also a max-min comparison for max of spring and min of previous fall, to look at the effect of the refreeze season?

This isn't exactly what you're asking for, but it may be close. The red line shows the annual volume lost--that is, the difference between max and min. (IOW, it shows the same data that Neven's vertical bar graph does.) The blue line shows, obviously, annual volume maxima, and the grey columns indicate how much ice is left at minimum. That may seem a little backward, but I've shown in this way to better illustrate how, in the not too distant future, there'll likely be years where the blue and the red lines converge. That is, the grey columns will at some point vertically shrink to near zero.

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fi.imgur.com%2F6A20m7d.png&hash=07ed751a02c228985998e244cb260566)

Thank you, Jim.  I love this graph - it (and your previous versions) brilliantly illustrates how the system is changing.


For completeness here are the exponential and gompertz fits.
Very nice, and thank you Wipneus.

I am struck not so much by the trend, as I am the increasing volatility of the scalar measurements.  It seems to me to be evidence of a system about to undergo a major transition in behavior.

Worth noting - we are back to well below 2007 end-of-season volume.
Title: Re: Latest PIOMAS update (September Interim)
Post by: oren on September 20, 2015, 04:43:57 PM
So looking at all these graps it seems 2015 was 3rd highest volume loss. Am I correct?
Title: Re: Latest PIOMAS update (September Interim)
Post by: kingbum on September 20, 2015, 11:54:36 PM
Ice volume volatility due to the lack of MYI...Until a reasonable amount of the ice pack is MYI then this is going to happen year in and year out...huge fluctuations between years due to weather. Everyone is calling for a death spiral to the ice pack and to that I say hold on a second. While it is true that the downward progression was linear here is a counter argument to play Devil's advocate so to speak. The AMO had been in a warm cycle since 1995- until probably 2012 the evidence I present to you is the Atlantic hurricane season most of them in that time period had been extremely active. Now it appears we have gone into a quiet period which is normal when the AMO switches to cold it explains why the Northern Atlantic is suddenly cooler than normal and the shift in the Gulf Stream to the south...My theory is that the ice will rebound again because of this shift. It is the Atlantic Ocean that has the most exposure to the Arctic..anyway if there's no gain by 2020 I will fall in line with you
Title: Re: Latest PIOMAS update (September Interim)
Post by: Neven on September 21, 2015, 09:01:46 AM
Ice volume volatility due to the lack of MYI...Until a reasonable amount of the ice pack is MYI then this is going to happen year in and year out...huge fluctuations between years due to weather. Everyone is calling for a death spiral to the ice pack and to that I say hold on a second. While it is true that the downward progression was linear here is a counter argument to play Devil's advocate so to speak. The AMO had been in a warm cycle since 1995- until probably 2012 the evidence I present to you is the Atlantic hurricane season most of them in that time period had been extremely active. Now it appears we have gone into a quiet period which is normal when the AMO switches to cold it explains why the Northern Atlantic is suddenly cooler than normal and the shift in the Gulf Stream to the south...My theory is that the ice will rebound again because of this shift. It is the Atlantic Ocean that has the most exposure to the Arctic..anyway if there's no gain by 2020 I will fall in line with you

I agree this could be playing a role in years to come, but what does 'switching to cold' mean? How cold is it compared to previous times? And is it just the SSTs, or also the layers just below it? I'd like to know more about it in terms of ocean heat flux and atmospheric effects, but I guess there isn't much known about it because it's so hard to quantify.
Title: Re: Latest PIOMAS update (September Interim)
Post by: jai mitchell on September 24, 2015, 05:15:54 PM
North Atlantic SST anomalies are a product of Greenland surface melt and a resulting decline in the AMOC.  The abnormally quiet current hurricane season (in the atlantic, not the pacific) is a result of significantly increased high altitude wind-shear and dry air off of the coast of africa.  These negative drivers for hurricane formation are well represented in the models, most of which predict a decline in the number of hurricanes in the atlantic basin as the earth warms, however these same models predict that rising mid-atlantic sea surface temperatures resulting from an increase in the Atlantic Gyre current and the availability of increased water vapor will produce much stronger hurricanes with landfall at further north latitudes when the regional circumstances become favorable for hurricane formation.

locked in warming and the reduction of aerosols will continue to increase the rates of sea ice loss in the near-term. 
Title: Re: Latest PIOMAS update (October)
Post by: Wipneus on October 05, 2015, 06:19:07 PM
PSC has updated their PIOMAS  daily volume data. I updated my graphics, see the top post (http://forum.arctic-sea-ice.net/index.php/topic,119.msg1562.html#msg1562)

Monthly gridded thickness data also updated (but not the daily), I will post the graphics tomorrow.
Title: Re: Latest PIOMAS update (September Interim)
Post by: kingbum on October 14, 2015, 01:09:01 PM
iuote author=jai mitchell link=topic=119.msg63907#msg63907 date=1443107754]
North Atlantic SST anomalies are a product of Greenland surface melt and a resulting decline in the AMOC.  The abnormally quiet current hurricane season (in the atlantic, not the pacific) is a result of significantly increased high altitude wind-shear and dry air off of the coast of africa.  These negative drivers for hurricane formation are well represented in the models, most of which predict a decline in the number of hurricanes in the atlantic basin as the earth warms, however these same models predict that rising mid-atlantic sea surface temperatures resulting from an increase in the Atlantic Gyre current and the availability of increased water vapor will produce much stronger hurricanes with landfall at further north latitudes when the regional circumstances become favorable for hurricane formation.

locked in warming and the reduction of aerosols will continue to increase the rates of sea ice loss in the near-term.
[/quote]

What would account then for the longest landfalling hurricane drought in US history then? It's been quite a few years now of less activity not just this El Niño mess and the closest thing I can find that explains most of what we have been seeing in the Atlantic and Arctic is the AMO.Judith Curry has done a lot of compelling research on this very topic but I agree with Neven much more needs to be done.
Title: Re: Latest PIOMAS update (October)
Post by: Wipneus on October 24, 2015, 02:53:03 PM
Average monthly thickness of September 2015 compared with years 2006-2014.
PIOMAS still shows 3+ m thick ice between the Canadian Archipelago and the pole, where Cryosat 2 and Jaxa thickness maps do not.

Click on the images for bigger pictures.
Title: Re: Latest PIOMAS update (November)
Post by: Wipneus on November 05, 2015, 09:28:45 AM
PSC has updated their PIOMAS  daily volume data. I updated my graphics, see the top post (http://forum.arctic-sea-ice.net/index.php/topic,119.msg1562.html#msg1562)

Monthly gridded thickness data also updated , I will post those graphics later.
Title: Re: Latest PIOMAS update (November)
Post by: Wipneus on November 05, 2015, 10:08:09 AM
Average monthly thickness of October 2015 compared with years 2006-2014.
PIOMAS still shows 3+ m thick ice between the Canadian Archipelago and the pole, where Cryosat 2 thickness maps do not. Cryosat 2 and Jaxa thickness maps show a blob of thicker ice between Svalbard and the pole, that can not be seen in the PIOMAS map.

Click on the images for bigger pictures.
Title: Re: Latest PIOMAS update (November)
Post by: Wipneus on November 05, 2015, 10:30:37 AM
From the daily gridded thickness data an animation of the ice thickness during September and October.

Click to start.
Title: Re: Latest PIOMAS update (November)
Post by: plinius on November 05, 2015, 10:35:08 AM
bears quite little resemblance to the measurement:
http://www.cpom.ucl.ac.uk/csopr/seaice.html (http://www.cpom.ucl.ac.uk/csopr/seaice.html)
(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fwww.cpom.ucl.ac.uk%2Fcsopr%2Fsidata%2Fthk_28.png&hash=f2d0199709d1124a821000ec1f466d41)
Title: Re: Latest PIOMAS update (November)
Post by: Neven on November 05, 2015, 11:44:16 AM
Thanks, Wipneus. I'll add your graph to the PIOMAS update (http://neven1.typepad.com/blog/2015/11/piomas-november-2015.html) over on the ASIB.
Title: Re: Latest PIOMAS update (November)
Post by: kingbum on November 06, 2015, 10:34:08 PM
Considering how low extent went I'm pleased with volume numbers this month. Notice that the last few years have actually been staggered gains against the linear line on Neven's ASIB graph. It was a couple standard deviations below the linear line before 2013...I think the trend upward is just being slightly delayed this year by El Niño and we will see another spike up higher than the previous years in either 2016 or maybe 2017 when the ocean loses some of that heat energy built up on the Pacific side. This also means global temperatures will drop off too...maybe as much as 0.5C given the strength of this event. A La Niña working with a cold AMO would greatly affect ice for the positive...However if 2015 is just a new plateau point for global temperatures then it is a continuation of the death spiral. Interesting times ahead many questions are about to be answered one way or another
Title: Re: Latest PIOMAS update (November)
Post by: DavidR on November 08, 2015, 01:13:51 PM
Considering how low extent went I'm pleased with volume numbers this month. Notice that the last few years have actually been staggered gains against the linear line on Neven's ASIB graph. It was a couple standard deviations below the linear line before 2013...I think the trend upward is just being slightly delayed this year by El Niño and we will see another spike up higher than the previous years in either 2016 or maybe 2017 when the ocean loses some of that heat energy built up on the Pacific side. This also means global temperatures will drop off too...maybe as much as 0.5C given the strength of this event. A La Niña working with a cold AMO would greatly affect ice for the positive...However if 2015 is just a new plateau point for global temperatures then it is a continuation of the death spiral. Interesting times ahead many questions are about to be answered one way or another
KB ,
There are a couple of  minor problems with this analysis.

The first issue is that the heat from an El Nino appears to  take a year to get to the Arctic so the big declines do not  occur until the year after the El Nino, you can see this if you  check out the declines in extent  after the 1983, 1998 El Ninos. Both 1984 and 1999  saw big drops in extent.

The second issue is that this El Nino will be the 2016 El Nino not the 2015 El Nino. They are usually known by the year they peak and break. The heat stays around for most of that year . This El Nino is still building and will result in both 2015 and 2016 being record breaking warm years.

There is very  little hope of a rise in sea ice extent or volume over the next two years and I  expect that by the end of 2017 the record minimum extent will start with a 2 not a 3.

Its also worth noting that temperatures have not dropped more than 0.3 degrees after a record warm year for decades. After 1998 only two years were cooler than the previous record hottest year, and the decline was less than 0.25 degrees. I  don't expect we will see a year as cool as 2014 in our lifetimes.

 
Title: Re: Latest PIOMAS update (November)
Post by: seaicesailor on November 08, 2015, 02:04:10 PM
bears quite little resemblance to the measurement:
http://www.cpom.ucl.ac.uk/csopr/seaice.html (http://www.cpom.ucl.ac.uk/csopr/seaice.html)
(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fwww.cpom.ucl.ac.uk%2Fcsopr%2Fsidata%2Fthk_28.png&hash=f2d0199709d1124a821000ec1f466d41)

The latest NSIDC News and Analysis has interesting remarks about the differences between Cryosat and other ice thickness sources like PIOMAS and SMOS measurements. Also it explains that SMOS thicknesses above 1m must not be trusted.

http://nsidc.org/arcticseaicenews/ (http://nsidc.org/arcticseaicenews/)
Title: Re: Latest PIOMAS update (November)
Post by: Neven on December 05, 2015, 12:22:33 AM
PIOMAS has been updated. I'll have a post up on the ASIB somewhere tomorrow.

In the meantime, The Cryosphere has this (http://www.the-cryosphere.net/9/2237/2015/tc-9-2237-2015.html):

Improved Arctic sea ice thickness projections using bias-corrected CMIP5 simulations
N. Melia1, K. Haines2, and E. Hawkins3

Abstract. Projections of Arctic sea ice thickness (SIT) have the potential to inform stakeholders about accessibility to the region, but are currently rather uncertain. The latest suite of CMIP5 global climate models (GCMs) produce a wide range of simulated SIT in the historical period (1979–2014) and exhibit various biases when compared with the Pan-Arctic Ice–Ocean Modelling and Assimilation System (PIOMAS) sea ice reanalysis. We present a new method to constrain such GCM simulations of SIT via a statistical bias correction technique. The bias correction successfully constrains the spatial SIT distribution and temporal variability in the CMIP5 projections whilst retaining the climatic fluctuations from individual ensemble members. The bias correction acts to reduce the spread in projections of SIT and reveals the significant contributions of climate internal variability in the first half of the century and of scenario uncertainty from the mid-century onwards. The projected date of ice-free conditions in the Arctic under the RCP8.5 high emission scenario occurs in the 2050s, which is a decade earlier than without the bias correction, with potentially significant implications for stakeholders in the Arctic such as the shipping industry. The bias correction methodology developed could be similarly applied to other variables to reduce spread in climate projections more generally.
Title: Re: Latest PIOMAS update (December)
Post by: Wipneus on December 05, 2015, 08:13:37 AM
Indeed, PSC has updated their PIOMAS  daily volume data. I updated my graphics, see the top post (http://forum.arctic-sea-ice.net/index.php/topic,119.msg1562.html#msg1562)

Gridded data was updated as well. Update of those graphics probably tomorrow.
Title: Re: Latest PIOMAS update (December)
Post by: Wipneus on December 06, 2015, 10:45:38 AM
Average monthly thickness of November 2015 compared with years 2006-2014.
There is still an area of anomalous thick ice between Ellesmere and pole.

Click on the images for bigger pictures.
Title: Re: Latest PIOMAS update (December)
Post by: Wipneus on December 06, 2015, 11:02:32 AM
And an animation of the thickness map during November 2015. Click to start.
Title: Re: Latest PIOMAS update (December)
Post by: Neven on December 06, 2015, 02:41:11 PM
Thanks for the collage, Wip!
Title: Re: Latest PIOMAS update (December)
Post by: Neven on December 08, 2015, 12:24:16 PM
Post is up (http://neven1.typepad.com/blog/2015/12/piomas-december-2015.html) over on the ASIB now.
Title: Re: Latest PIOMAS update (December)
Post by: A-Team on December 08, 2015, 02:36:25 PM
Here is a 700 ms animation of inter-year comparisons to November 2015. Done from #788 using guilllotine in gimp, save as, open as layers, rescale to 700 pxl width. It could be done at even larger forum scale by moving legend over and recropping but this seems to overshoot the intrinsic resolution.
Title: Re: Latest PIOMAS update (January)
Post by: Wipneus on January 06, 2016, 08:39:41 AM
PSC has updated their PIOMAS  daily volume data. I updated my graphics, see the top post (http://forum.arctic-sea-ice.net/index.php/topic,119.msg1562.html#msg1562)

Gridded thickness data also updated, I will post the graphics later.
Title: Re: Latest PIOMAS update (January)
Post by: Wipneus on January 06, 2016, 10:02:07 AM
Average monthly thickness of December 2015 compared with years 2006-2014.
There is still an area of anomalous thick ice between Ellesmere and pole.

Click on the images for bigger pictures.
Title: Re: Latest PIOMAS update (January)
Post by: Wipneus on January 06, 2016, 10:27:22 AM
And here an animation of the daily ice thickness development during December.

click to animate.
Title: Re: Latest PIOMAS update (January)
Post by: Neven on January 06, 2016, 12:23:26 PM
Thanks, Wipneus. I'm waiting for the PSC to update their graphs, and then I'll put up a blog post.
Title: Re: Latest PIOMAS update (January)
Post by: Wipneus on January 06, 2016, 12:46:53 PM
As far as I see, they did :

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fpsc.apl.uw.edu%2Fwordpress%2Fwp-content%2Fuploads%2Fschweiger%2Fice_volume%2FBPIOMASIceVolumeAnomalyCurrentV2.1_CY.png&hash=71e098ee33c36296b9e24f63de218d71)
(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fpsc.apl.uw.edu%2Fwordpress%2Fwp-content%2Fuploads%2Fschweiger%2Fice_volume%2FBPIOMASIceVolumeAnomalyCurrentV2.1.png&hash=d75486bc4e09ac0c665a1e839b46b78a)
(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fpsc.apl.uw.edu%2Fwordpress%2Fwp-content%2Fuploads%2Fschweiger%2Fice_volume%2FBpiomas_plot_daily_heff.2sst.png&hash=48ad7f451f85ccc2900ab160096deff6)
Title: Re: Latest PIOMAS update (February)
Post by: Wipneus on February 04, 2016, 08:54:32 AM
Still waiting for the regular PIOMAS volume data update. Should not be long as the gridded thickness data just appeared. Graphs will appear asap, lots of 2015->2016 changes to be made.
Title: Re: Latest PIOMAS update (February)
Post by: Wipneus on February 04, 2016, 10:21:27 AM
Average monthly thickness of January 2016 compared with years 2007-2015.

Click on the images for bigger pictures.
Title: Re: Latest PIOMAS update (February)
Post by: Wipneus on February 04, 2016, 12:32:30 PM
Animation of the daily ice thickness for January.

Click to start the 3 Meg animation.

[EDIT: showed the wrong year, this should be 2016]
Title: Re: Latest PIOMAS update (February)
Post by: Jim Hunt on February 04, 2016, 01:42:26 PM
Click to start the 3 Meg animation.

I click, but I don't see any animation :( Firefox on Scientific Linux and Chrome on Windows 7.
Title: Re: Latest PIOMAS update (February)
Post by: Wipneus on February 04, 2016, 03:00:36 PM
Click to start the 3 Meg animation.

I click, but I don't see any animation :( Firefox on Scientific Linux and Chrome on Windows 7.

It is the forum software that does not upload any of the frames but the first one, if it is in that mood.

So when I upload an animated gif, I always try to remember to check if it works, if not fiddle with the file and try again and repeat.

This time, being rather busy with replacing the Raspberry Pie's harddrive (1TB->3TB), I just forgot.

Loading and saving in the Gimp was enough to convince the forum software that the animation was OK.
Title: Re: Latest PIOMAS update (February)
Post by: Jim Hunt on February 04, 2016, 03:07:17 PM
Loading and saving in the Gimp was enough to convince the forum software that the animation was OK.

Thanks Wipneus. OK for me now!
Title: Re: Latest PIOMAS update (February)
Post by: TenneyNaumer on February 04, 2016, 05:37:22 PM
PIOMAS is hopelessly wrong.

The sea ice is right now undergoing its breakup pattern, normally seen in late March ("normal" in the last few years; pre-2007 it was in May-June).

The ice is so thin that the normal currents are breaking it up.  (Not to mention that the ice has been beaten to death by storms entering the Arctic all winter long.)

You can watch it here:  https://weather.gc.ca/data/satellite/hrpt_dfo_ir_100.jpg (https://weather.gc.ca/data/satellite/hrpt_dfo_ir_100.jpg)
Title: Re: Latest PIOMAS update (February)
Post by: seaicesailor on February 04, 2016, 05:43:02 PM
With this indication, and the current high if it persists, there will be another interesting Beaufort battle this year
Title: Re: Latest PIOMAS update (February)
Post by: Peter Ellis on February 04, 2016, 06:10:02 PM
PIOMAS is hopelessly wrong.

The sea ice is right now undergoing its breakup pattern, normally seen in late March ("normal" in the last few years; pre-2007 it was in May-June).

The ice is so thin that the normal currents are breaking it up.  (Not to mention that the ice has been beaten to death by storms entering the Arctic all winter long.)

Caution!  Remember all the fuss about the 'Crackocalypse' in 2013.  It ended up meaning extra MYI got advected into the Beaufort Sea, which helped stall the melt there in summer of 2013.  Meanwhile, the open leads vented heat to the atmosphere and rapidly froze over, so the net effect probably increased ice production.

Not all ice fracturing is equivalent (remember that as ice cools, it shrinks, which will also cause cracks to open), and open leads in the coldest part of winter is a great way for the Arctic to lose heat.

I would be very wary of making any projections about the melt season until ooh, mid-May or thereabouts.
Title: Re: Latest PIOMAS update (February)
Post by: jdallen on February 04, 2016, 06:11:28 PM
PIOMAS is hopelessly wrong.

The sea ice is right now undergoing its breakup pattern, normally seen in late March ("normal" in the last few years; pre-2007 it was in May-June).

The ice is so thin that the normal currents are breaking it up.  (Not to mention that the ice has been beaten to death by storms entering the Arctic all winter long.)

You can watch it here:  https://weather.gc.ca/data/satellite/hrpt_dfo_ir_100.jpg (https://weather.gc.ca/data/satellite/hrpt_dfo_ir_100.jpg)

I like the CWS microwave and IR satellite imagery.  It was looking at that which brought me to the page years ago.  What I'm seeing now looks quite familiar - a major cracking event in the Beaufort - not unakin to what we saw over each of the last few years.

Do others recall timing?  I think its about the same timing this year, maybe a week or two earlier?
Title: Re: Latest PIOMAS update (February)
Post by: Peter Ellis on February 04, 2016, 06:25:32 PM
It's maybe a week earlier than 2013.  I suspect this kind of event may be one of the feedbacks that stabilises winter ice volume loss - i.e. thinner ice is more likely to fracture into leads, thereby exposing more water for rapid ice formation.  I have certainly seen publications that say increase ridging of thinner ice is such a feedback, and ridging and rifting are logically part of the same phenomenon of fracture and regrowth.

Remember that there is no melt - no volume loss - in the Beaufort at the moment, nor will be for months yet.  If you see a gap open up, then the ice that used to be in that gap is now somewhere else, making another part of the ice sheet thicker.
Title: Re: Latest PIOMAS update (February)
Post by: Wipneus on February 04, 2016, 06:34:51 PM
Here is a side by side animation of the last two weeks now in 2016 compared with 2013 as seen by AMSR2 (ASI sea ice concentration data from UH Hamburg).
The "Crackocalypse" did not happen until 20 February or so.

(click req'd)
Title: Re: Latest PIOMAS update (February)
Post by: jdallen on February 04, 2016, 06:52:22 PM
Here is a side by side animation of the last two weeks now in 2016 compared with 2013 as seen by AMSR2 (ASI sea ice concentration data from UH Hamburg).
The "Crackocalypse" did not happen until 20 February or so.

(click req'd)
Two and a half weeks? That may actually be significant.
Title: Re: Latest PIOMAS update (February)
Post by: Peter Ellis on February 04, 2016, 07:21:55 PM
... means even longer for the exposed water to freeze over and thicken. We really mustn't leap to assuming every event is a harbinger of the end.
Title: Re: Latest PIOMAS update (February)
Post by: jdallen on February 04, 2016, 08:38:41 PM
... means even longer for the exposed water to freeze over and thicken. We really mustn't leap to assuming every event is a harbinger of the end.
Absolutely and I understand your caution, Peter.

I would be happier if the air temps were 5-10C cooler so we could catch up a bit.

I'm curious what the additional contribution to heat loss open leads would add.  I'm wondering if it would even be as much as a couple of percent - they don't really cover that much area, even when considered in aggregate over time.

I'm looking at the cracking as a qualitative signal reflecting other dimensions of the system over all.  I doubt it will have a significant causative effect on the melt season - save for how it shuffles MYI around.
Title: Re: Latest PIOMAS update (February)
Post by: jdallen on February 04, 2016, 10:36:37 PM
Pertinent to discussion about freezing and thickening, this is what we're going to start struggling with soon now, especially in the peripheral seas.

Sunrise.

The Bering and Okhostk are already getting multiple hours of sunlight a day over mostly open water.  If they aren't getting sunlight, the clouds will be holding in heat.  It will be rapidly ramping up in the Chukchi.

The Kara which has had very thin coverage (particularly the Western) over just a few weeks, will be back in daylight  in a few days, as will the Barents, which has been supernaturally warm all winter. 

Even with the high pressure, most of the basin is maintaining temperatures of 5C or more above normal.

Combine that with even modest returning insolation (especially where it's over open water) and we are rapidly running out of places where we can add significant volume.
Title: Re: Latest PIOMAS update (February)
Post by: TenneyNaumer on February 05, 2016, 05:29:07 AM
I have been downloading these satellite photos since early 2007 (unfortunately, I did not backup the old laptop most of them were on -- now I keep them on a USB drive).  That's 9 years of peering at these images.   In 2007, the ice only barely began to break up at the end of May, and by breakup, I mean that a crack appeared along the edge of the entire Canadian archipelago.  The ice was incredibly thick compared to what we have now.  Recall that land-fast ice shelves existed, some 120-feet thick.  Those all broke away and disappeared in the years after 2007.  Some of these ice shelves covered areas that had not seen open water in 14,000 years.  Those ice shelves had acted as a sort of break on the movement of the sea ice.  Further, although an increasing number of storms were entering the Arctic, during the winter months, this was still a rare occurrence.  Not anymore.

And you have only to look at the speed of the sea ice.  By about 2009, the speed had doubled over the long-term average.  Lord only knows how fast it is moving these days compared to the 1980s, for example. 

Further, the entire character of the sea ice is radically different -- you might as well be discussing the difference between cucumbers and artichokes.  In the past, the ice was very dense and strong, now it is like Swiss cheese made of spongy slush.

Here are some satellite photos from other years (2012 and 2013) at this time:










Title: Re: Latest PIOMAS update (February)
Post by: jdallen on February 05, 2016, 09:42:00 AM
I have been downloading these satellite photos since early 2007... <snippage>

All in all, not qualitatively that much different than what we are seeing now, from what I can tell.

Best guess is, 2016 is acting in accordance with what has been typical since 2010.
Title: Re: Latest PIOMAS update (February)
Post by: Jim Hunt on February 05, 2016, 01:44:36 PM
Further, the entire character of the sea ice is radically different -- you might as well be discussing the difference between cucumbers and artichokes.  In the past, the ice was very dense and strong, now it is like Swiss cheese made of spongy slush.

Here are some of my own satellite screenshots:

http://GreatWhiteCon.info/resources/arctic-sea-ice-images/ (http://GreatWhiteCon.info/resources/arctic-sea-ice-images/)

Have you by any chance read Chris Reynolds on this topic, so dear to all our hearts?

http://forum.arctic-sea-ice.net/index.php/topic,933.0.html (http://forum.arctic-sea-ice.net/index.php/topic,933.0.html)

How about this paper, mentioned in the latest edition of Arctic Sea Ice News (http://greatwhitecon.info/2016/02/arctic-sea-ice-area-and-extent-lowest-ever-for-the-date/#comment-213371)?

"Predicted slowdown in the rate of Atlantic sea ice loss (http://onlinelibrary.wiley.com/doi/10.1002/2015GL065364/full)"
Title: Re: Latest PIOMAS update (February)
Post by: Neven on February 05, 2016, 09:17:18 PM
I'm struck by the difference between 2016 and 2015, with all that deep blue north of Greenland and the CAA:
Title: Re: Latest PIOMAS update (February)
Post by: jdallen on February 05, 2016, 10:06:54 PM
I'm struck by the difference between 2016 and 2015, with all that deep blue north of Greenland and the CAA:
Yeah, that's worrisome.  I think it exemplifies the odd movement of the ice at the end of the last melt season, and the generally unseasonably warm temperatures we've seen over the last 6 weeks.
Title: Re: Latest PIOMAS update (February)
Post by: epiphyte on February 05, 2016, 10:40:29 PM
... means even longer for the exposed water to freeze over and thicken. We really mustn't leap to assuming every event is a harbinger of the end.

Last year I got the strong impression that much of the ice which papered over the crackopalypse in Feb/Mar didn't last too long into the melting season (it is zeroth year ice, after all). Assuming for a moment that I'm right about that, the net effect of the cracking on the season as a whole isn't clear, to me at least, at all.

Yes, the open water in Feb causes faster ice formation now, but if those same areas become open water again when the sun is high, wouldn't they prematurely lower the average surface albedo, causing faster melting later?

On balance, while the net effect on the season doesn't appear obvious, it would seem reasonable to suppose that the earlier in the season the crackup happens, the less likely it is to result in a net decrease in volume - since the paper over the cracks would be thicker and take longer to melt...
Title: Re: Latest PIOMAS update (February)
Post by: Shared Humanity on February 06, 2016, 02:08:13 AM
I'm struck by the difference between 2016 and 2015, with all that deep blue north of Greenland and the CAA:

CAA took a beating last melt season. Unless thick MYI moves in, isn't this what we would expect to see?
Title: Re: Latest PIOMAS update (February)
Post by: crandles on February 06, 2016, 12:13:57 PM
I'm struck by the difference between 2016 and 2015, with all that deep blue north of Greenland and the CAA:

CAA took a beating last melt season. Unless thick MYI moves in, isn't this what we would expect to see?

All that deep blue seems noteworthy in part because they are red in maps showing comparison with other years mainly 2010 through 2014. If this year was particularly thin you would expect to see blue in these area against all or at least most year. This therefore seems to point to January 2015 being particularly thick in those areas.

So conclusion seems to be ice in those area in 2016 is thicker than 2010 through 2014 but not as thick as in 2015 when it was particularly thick in those areas.

That doesn't seem hugely exciting. Atlantic edge looks thin compared to most years, very nearly as thin as 2013 when it was vulnerable/still recovering from 2012. This seem to me to be the more interesting conclusion to reach.

A less exciting observation might be the ice is thicker over large areas compared to 2011, 12, 13, and 14.

Another point being this is January average and if the volume is only increasing very slowly part of this effect is not yet showing through.
Title: Re: Latest PIOMAS update (February)
Post by: magnamentis on February 06, 2016, 01:01:00 PM
I'm struck by the difference between 2016 and 2015, with all that deep blue north of Greenland and the CAA:

CAA took a beating last melt season. Unless thick MYI moves in, isn't this what we would expect to see?

All that deep blue seems noteworthy in part because they are red in maps showing comparison with other years mainly 2010 through 2014. If this year was particularly thin you would expect to see blue in these area against all or at least most year. This therefore seems to point to January 2015 being particularly thick in those areas.

So conclusion seems to be ice in those area in 2016 is thicker than 2010 through 2014 but not as thick as in 2015 when it was particularly thick in those areas.

That doesn't seem hugely exciting. Atlantic edge looks thin compared to most years, very nearly as thin as 2013 when it was vulnerable/still recovering from 2012. This seem to me to be the more interesting conclusion to reach.

A less exciting observation might be the ice is thicker over large areas compared to 2011, 12, 13, and 14.

Another point being this is January average and if the volume is only increasing very slowly part of this effect is not yet showing through.

honestly speaking i take all sea-ice-volume images with a prise of salt. going through the various available graphics they show far too different results to appear reliable. might well be the one of them is correct but who knows which one. especially many of those graphics don't correspond with what we see with our own eyes. last summer some of them were showing thick ice where satellites showed open water and polnyas LOL
Title: Re: Latest PIOMAS update (February)
Post by: Wipneus on February 06, 2016, 01:55:15 PM
Regular PIOMAS volume data update is still pending.
Calculating those from the gridded data I get for January:

2016 1 15.742
2016 2 15.829
2016 3 15.93
2016 4 16.013
2016 5 16.109
2016 6 16.193
2016 7 16.295
2016 8 16.409
2016 9 16.536
2016 10 16.685
2016 11 16.82
2016 12 16.917
2016 13 17.018
2016 14 17.116
2016 15 17.232
2016 16 17.315
2016 17 17.394
2016 18 17.482
2016 19 17.579
2016 20 17.668
2016 21 17.766
2016 22 17.87
2016 23 17.978
2016 24 18.073
2016 25 18.148
2016 26 18.206
2016 27 18.246
2016 28 18.315
2016 29 18.393
2016 30 18.471
2016 31 18.538

Attached are the preliminary volume and volume anomaly graphs. No surprise, January growth was relatively slow.
Title: Re: Latest PIOMAS update (February)
Post by: TenneyNaumer on February 06, 2016, 11:15:12 PM
Very sorry I don't have images from earlier years -- the qualitative difference is quite stark. 

Wipneus's second graph at Reply 823 is very telling.  PIOMAS would have you believe the ice volume in Nov 2014 was as high as in 2008.  This defies credulity.  We know the ice has changed fundamentally since 2008.

I have been downloading these satellite photos since early 2007... <snippage>

All in all, not qualitatively that much different than what we are seeing now, from what I can tell.

Best guess is, 2016 is acting in accordance with what has been typical since 2010.
Title: Re: Latest PIOMAS update (February)
Post by: Peter Ellis on February 07, 2016, 05:22:04 PM
I'm curious what the additional contribution to heat loss open leads would add.  I'm wondering if it would even be as much as a couple of percent - they don't really cover that much area, even when considered in aggregate over time.

Much more than you'd think. Consider this graph.

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Ffarm4.staticflickr.com%2F3824%2F9586307013_77132e9dd4_o.jpg&hash=f79a0214528038d3c8256d0c57a5032f)

This shows the rate of ice growth in cm per day dependent on the current thickness of the ice. Ice formation (equivalent to energy loss via the enthalpy of freezing) in an open lead is around 30x as high as the energy loss through typical 1st year ice at this time of year (i.e. 1-1.5m thick).

If there are no leads before the cracking event, and this increases to 3% open water area after the cracking event, then the total heat loss goes from 100 (arbitrary units) to 187, i.e. it almost doubles the total rate of ice volume formation. This increased ice formation rate then slowly decays back to normal over the next couple of weeks as the leads seal over.
Title: Re: Latest PIOMAS update (February)
Post by: TenneyNaumer on February 07, 2016, 07:51:07 PM
Wouldn't the graph assume certain conditions as, for example, the air temperature above the ice and the water temperature below it?  Possibly it assumes that the temperature of the water is at the freezing point.  What if the water's temperature is actually one or two degrees higher?

The breakup pattern of leads is continuing:
Title: Re: Latest PIOMAS update (February)
Post by: Peter Ellis on February 07, 2016, 08:01:32 PM
Wouldn't the graph assume certain conditions as, for example, the air temperature above the ice and the water temperature below it?
The fundamental equation stays the same even if the parameters change, so the shape of the graph stays the same.  The shape is determined by the insulating properties of ice.

Simply put, heat flow through a few-cm thick layer of nascent ice will be many fold less than the heat flow through a 1.5-metre layer of mature FYI. Colder air will change the scale of the y axis, but not change the ratio between thin/thicker ice growth rates.
Title: Re: Latest PIOMAS update (February)
Post by: seaicesailor on February 07, 2016, 08:08:38 PM
I'm curious what the additional contribution to heat loss open leads would add.  I'm wondering if it would even be as much as a couple of percent - they don't really cover that much area, even when considered in aggregate over time.

Much more than you'd think...

[...]

This shows the rate of ice growth in cm per day dependent on the current thickness of the ice. Ice formation (equivalent to energy loss via the enthalpy of freezing) in an open lead is around 30x as high as the energy loss through typical 1st year ice at this time of year (i.e. 1-1.5m thick).

If there are no leads before the cracking event, and this increases to 3% open water area after the cracking event, then the total heat loss goes from 100 (arbitrary units) to 187, i.e. it almost doubles the total rate of ice volume formation. This increased ice formation rate then slowly decays back to normal over the next couple of weeks as the leads seal over.

The area being refrozen is significant. People expected in 2013 the cracks be very vulnerable, even foster positive feedback on the melting, because the new ice is thinner, easier to melt, it has less snow on top, and once melt, its albedo drops helping later melt of older ice.
Maybe we did not see all that in 2013 because weather during that melting season was cold, there was no spark.
Title: Re: Latest PIOMAS update (February)
Post by: Andreas T on February 08, 2016, 08:13:50 PM
Wouldn't the graph assume certain conditions as, for example, the air temperature above the ice and the water temperature below it?  Possibly it assumes that the temperature of the water is at the freezing point.  What if the water's temperature is actually one or two degrees higher?
...
The water temperature below the ice can only be at freezing point unless the ice is melting and there is heat input into the water (e.g. sunshine). At present freezing point temperature is a very good assumption.
The graph shows the difference ice thickness makes to growth rate at otherwise equal conditions, if the discussion is does cracking increase ice production or not it is the right graph to look at.
What happens later in the season to melting rates is more complex. Draining of meltponds is favoured by cracked floes, late ice gets less snow fall but form watching observation buoys I would say snow is loose and drifting so it doesn't stay where it has fallen. Not an obvious answer on what has the stronger effect.
Title: Re: Latest PIOMAS update (February)
Post by: johnm33 on February 08, 2016, 09:51:40 PM
The sea surface temperature shows anomolies over wide areas, presumably through the cracks
(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fpuu.sh%2Fn0Fyt%2Fad6252cf54.jpg&hash=f6bf07cc987ec15bff735262f6dae9a8)
this shows an anomoly of .5C so -1.3C and above freezing[-1.8] wayne of http://eh2r.blogspot.ca/ (http://eh2r.blogspot.ca/)
a frequent commenter on the ASI blog, and a keen observer of the ice has stated a few times that you need an air temp. of -11C to get sea water to freeze, so where the graph says winter one assumes temperarures below that. Despite frequent air temp. anomolies of +15C or more I'm not sure it's gone above -11C in Beaufort at all. If you check out waynes blog he has a post up about his doubts on Piomas. If the sst anomolies persist then I doubt we'll get a 'normal' refreeze in Piomas's terms.
http://earth.nullschool.net/#current/ocean/surface/currents/overlay=sea_surface_temp_anomaly/orthographic=-14.55,108.73,1106/loc=-132.129,70.653 (http://earth.nullschool.net/#current/ocean/surface/currents/overlay=sea_surface_temp_anomaly/orthographic=-14.55,108.73,1106/loc=-132.129,70.653)
Title: Re: Latest PIOMAS update (February)
Post by: Wipneus on February 10, 2016, 03:43:58 PM
PSC has now updated their PIOMAS  daily volume data as well. I updated my graphics, see the top post (http://forum.arctic-sea-ice.net/index.php/topic,119.msg1562.html#msg1562)
Title: Re: Latest PIOMAS update (February)
Post by: Neven on February 10, 2016, 04:15:57 PM
PIOMAS February 2016 (http://neven1.typepad.com/blog/2016/02/piomas-february-2016.html) is out on the ASIB. Big, big changes that Wipneus was already alluding to!
Title: Re: Latest PIOMAS update (February)
Post by: jdallen on February 10, 2016, 07:22:18 PM
PIOMAS February 2016 (http://neven1.typepad.com/blog/2016/02/piomas-february-2016.html) is out on the ASIB. Big, big changes that Wipneus was already alluding to!
Knew all this heat was going to have a dramatic effect on thickness.  Gratifying for my conclusion to be quantified and affirmed.  Terrifying that I was right.
Title: Re: Latest PIOMAS update (February)
Post by: Neven on March 09, 2016, 12:58:23 PM
PIOMAS has been updated. February saw the second lowest February increase in the 2007-2016 record, meaning 2016 is now lower than 2012 and every other year, just behind 2011. I'll have a ASIB post on this later today.
Title: Re: Latest PIOMAS update (March)
Post by: Trebuchet on March 09, 2016, 03:51:26 PM
 Noob question but how accurate is the PIOMAS model? If you look at the picture the DMI (center) and HYCOM (right) models look totally inaccurate over the CAB when compared to the Cryosat measured data. It's not reassuring that if those models are inaccurate at high latitudes that PIOMAS is.
Title: Re: Latest PIOMAS update (March)
Post by: Wipneus on March 09, 2016, 04:09:24 PM
Yes, PSC has updated their PIOMAS  daily volume data. I updated my graphics, see the top post (http://forum.arctic-sea-ice.net/index.php/topic,119.msg1562.html#msg1562)

Monthly gridded thickness data also updated , I will post the graphics here later.
Daily gridded data: not yet.
Title: Re: Latest PIOMAS update (March)
Post by: Neven on March 09, 2016, 05:26:54 PM
Noob question but how accurate is the PIOMAS model? If you look at the picture the DMI (center) and HYCOM (right) models look totally inaccurate over the CAB when compared to the Cryosat measured data. It's not reassuring that if those models are inaccurate at high latitudes that PIOMAS is.

Hi Trebuchet. First of all, CryoSat also has its problems and isn't perfect. Personally, I don't put much trust in the DMI and HYOM/ACNFS ice thickness distribution maps, but over the years I have to say that PIOMAS has always given a good feel of the general situation with regards to Arctic sea ice volume. Wipneus posts awesome distribution maps too, but I'm not sure how accurate these are either. But a diffcerence with other models is that observational data (thickness measurements by planes, subs, scientists on the ice) gets assimilated for the PIOMAS product.
Title: Re: Latest PIOMAS update (March)
Post by: seaicesailor on March 09, 2016, 09:57:43 PM
Wow the overall thickening for last two months combined is so small. High temperature anomalies sustained surely had a lot to do with this. Direct AGW preconditioning.
Title: Re: Latest PIOMAS update (March)
Post by: Neven on March 10, 2016, 12:05:52 AM
Blog post is up: PIOMAS March 2016 (http://neven1.typepad.com/blog/2016/03/piomas-march-2016.html).
Title: Re: Latest PIOMAS update (March)
Post by: Wipneus on March 10, 2016, 10:10:34 AM
Average monthly thickness of February 2016 compared with years 2007-2015.

Click on the images for bigger pictures.
Title: Re: Latest PIOMAS update (March)
Post by: Wipneus on March 10, 2016, 10:18:07 AM
Animation of the daily ice thickness for February. Ice coming from the region north of Greenland can be seen exiting through the Fram Strait.

Click to start the 3 Meg animation.

[UPDATE: fixed the animation, it was showing 2015 ]
Title: Re: Latest PIOMAS update (March)
Post by: Richard Rathbone on March 11, 2016, 03:10:27 PM
Noob question but how accurate is the PIOMAS model? If you look at the picture the DMI (center) and HYCOM (right) models look totally inaccurate over the CAB when compared to the Cryosat measured data. It's not reassuring that if those models are inaccurate at high latitudes that PIOMAS is.

Hi Trebuchet. First of all, CryoSat also has its problems and isn't perfect. Personally, I don't put much trust in the DMI and HYOM/ACNFS ice thickness distribution maps, but over the years I have to say that PIOMAS has always given a good feel of the general situation with regards to Arctic sea ice volume. Wipneus posts awesome distribution maps too, but I'm not sure how accurate these are either. But a diffcerence with other models is that observational data (thickness measurements by planes, subs, scientists on the ice) gets assimilated for the PIOMAS product.

HYCOM/CICE models are different in a few respects from PIOMAS.

HYCOM/CICE is a forecast model, it predicts what the state of the Arctic will be tomorrow, based on what it thinks the state of the Arctic is today. PIOMAS is a hindcast model, it calculates what the state of the Arctic was last month based on measurements of what the state of the Arctic was last month. So where measurements are available, PIOMAS is likely to be more accurate. In particular, since PIOMAS uses reanalysed weather, while CICE uses weather predictions, PIOMAS should normally have a rather better idea of what the state of the weather was, and project ice conditions through the month better as a result. So if you want to know what the state of the Arctic was last month, PIOMAS should normally be the better guide. However, if you want to know what it will be tomorrow, CICE will make a guess and PIOMAS won't.

PIOMAS takes a lot more data into account than HYCOM/CICE does, and some of the assimilation in HYCOM/CICE models is problematic.

Both use measurements of ice concentration, but the only other data assimilated by HYCOM/CICE is sea surface temperature, and that's not a good thing to assimilate in areas with ice, because water in contact with ice is constrained to be at its melting point, so you don't actually gain anything by using data, and you can send the model haywire if you assimilate measurement inaccuracies too strongly (as was seen last year when a HYCOM/CICE model sent salinity all over the place to get the melting point of ice to match up with the data it was assimilating).

The ocean structure in HYCOM/CICE has to work for weather prediction as well as heat transfer to ice, while in PIOMAS it just has to work for heat transfer to ice. I think this is behind the tendency of HYCOM/CICE to have a shorter and more aggressive melt season that PIOMAS. CICE puts heat directly from insolation into melting the ice in July, while PIOMAS puts it into heating the ocean and continues bottom melting with that heat into September.

However neither are able to constrain thickness details at all closely from measurement, and both will have a lot of compensating errors (they'll get what proportion is a given thickness about right, but not where it is) and you shouldn't pay much attention to the thickness details as opposed to the broad picture.

HYCOM/CICE if you want to know what the ice will look like in 2 days time.
PIOMAS if you want to know what the total volume was last month.
Title: Re: Latest PIOMAS update (March)
Post by: Neven on March 11, 2016, 11:21:22 PM
Thanks, Richard. That's a great explanation.
Title: Re: Latest PIOMAS update (March)
Post by: slow wing on March 11, 2016, 11:44:05 PM
Thanks, appreciated.


But is the Cryosat measured ice thickness data more accurate than all the models? That would be my starting assumption. If not, why not?
Title: Re: Latest PIOMAS update (March)
Post by: Jim Hunt on March 12, 2016, 01:19:01 AM
But is the Cryosat measured ice thickness data more accurate than all the models? That would be my starting assumption. If not, why not?

There's an entire thread devoted to the topic:

Piomas vs. CryoSat (http://forum.arctic-sea-ice.net/index.php/topic,8.0.html)
Title: Re: Latest PIOMAS update (March)
Post by: Peter Ellis on March 12, 2016, 12:32:01 PM
Thanks, appreciated.


But is the Cryosat measured ice thickness data more accurate than all the models? That would be my starting assumption. If not, why not?

Short version - nobody really knows, because measuring ice thickness is really hard.  Or even defining ice thickness, come to that - average height of a rugged landscape is a slippery concept.
Title: Re: Latest PIOMAS update (March)
Post by: slow wing on March 13, 2016, 01:10:34 AM
Thanks for your replies and pointing to the relevant thread.

Yes, early in the thread has some discussion on the measurement difficulties associated with snow cover on the ice.


Concerning a definition of ice thickness, I would have thought solid water mass per unit area would be a useful definition to try to measure/model towards. (A reference ice density constant would convert the units to length/thickness.) To first order, that gives the amount of heat required to melt it out - up to second order corrections for snow vs. ice and ice salinity - which is what is mainly of interest to us.
Title: Re: Latest PIOMAS update (March)
Post by: TenneyNaumer on March 13, 2016, 05:26:36 PM
Instead of focusing on models, you should be focusing on the actual sea ice.  It is not solid -- it is full of large holes like swiss cheese.  The ice now is nothing like it was in 2012. 

We've been getting plenty of information that it is soft like butter.  It used to be very solid and hard.

It is simply not the same animal. 
Title: Re: Latest PIOMAS update (March)
Post by: Andreas T on March 13, 2016, 07:45:41 PM
Instead of focusing on models, you should be focusing on the actual sea ice.  It is not solid -- it is full of large holes like swiss cheese.  The ice now is nothing like it was in 2012. 

We've been getting plenty of information that it is soft like butter.  It used to be very solid and hard.

It is simply not the same animal.
what do you expect to be inside those "swiss cheese holes"?
Title: Re: Latest PIOMAS update (March)
Post by: seaicesailor on March 13, 2016, 07:59:29 PM
Animation of the daily ice thickness for February. Ice coming from the region north of Greenland can be seen exiting through the Fram Starit.

Click to start the 3 Meg animation.

February thicknesses along the coast of Siberia reach 3 m and 4 m at some locations, whereas in the video these don"t even reach 2m.
Title: Re: Latest PIOMAS update (March)
Post by: jdallen on March 13, 2016, 08:46:35 PM
Instead of focusing on models, you should be focusing on the actual sea ice.  It is not solid -- it is full of large holes like swiss cheese.  The ice now is nothing like it was in 2012. 

We've been getting plenty of information that it is soft like butter.  It used to be very solid and hard.

It is simply not the same animal.
what do you expect to be inside those "swiss cheese holes"?
Brine perhaps?
Title: Re: Latest PIOMAS update (March)
Post by: Andreas T on March 13, 2016, 11:21:13 PM
But how would the brine inclusions be different from previous years? Younger ice could be a reason. Compaction would change ice structure, maybe affecting draining of brine. Ice temperature is of course an important factor but how different that is, is hard to say. Unfortunately the mass balance buoys are few and most are not reporting data.
Title: Re: Latest PIOMAS update (March)
Post by: Andreas T on March 14, 2016, 01:13:08 AM
some information on brine inclusion and brine drainage in sea ice http://pure.au.dk/portal/files/84136596/Galley_et_al_2015_MRI.pdf (http://pure.au.dk/portal/files/84136596/Galley_et_al_2015_MRI.pdf)
Title: Re: Latest PIOMAS update (February)
Post by: Frivolousz21 on March 14, 2016, 06:06:47 AM
The sea surface temperature shows anomolies over wide areas, presumably through the cracks
(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fpuu.sh%2Fn0Fyt%2Fad6252cf54.jpg&hash=f6bf07cc987ec15bff735262f6dae9a8)
this shows an anomoly of .5C so -1.3C and above freezing[-1.8] wayne of http://eh2r.blogspot.ca/ (http://eh2r.blogspot.ca/)
a frequent commenter on the ASI blog, and a keen observer of the ice has stated a few times that you need an air temp. of -11C to get sea water to freeze, so where the graph says winter one assumes temperarures below that. Despite frequent air temp. anomolies of +15C or more I'm not sure it's gone above -11C in Beaufort at all. If you check out waynes blog he has a post up about his doubts on Piomas. If the sst anomolies persist then I doubt we'll get a 'normal' refreeze in Piomas's terms.
http://earth.nullschool.net/#current/ocean/surface/currents/overlay=sea_surface_temp_anomaly/orthographic=-14.55,108.73,1106/loc=-132.129,70.653 (http://earth.nullschool.net/#current/ocean/surface/currents/overlay=sea_surface_temp_anomaly/orthographic=-14.55,108.73,1106/loc=-132.129,70.653)

If that is modeled it's likely wrong.

Title: Re: Latest PIOMAS update (March)
Post by: Frivolousz21 on March 14, 2016, 06:12:31 AM
Noob question but how accurate is the PIOMAS model? If you look at the picture the DMI (center) and HYCOM (right) models look totally inaccurate over the CAB when compared to the Cryosat measured data. It's not reassuring that if those models are inaccurate at high latitudes that PIOMAS is.

The middle image is incredibly wrong.  Looks like mid 1990s thickness's. 

The right image is a lot closer to reality than the middle image.

 And the left image is certainly the most accurate.

Cryosat might be off  in some areas due to snow cover, snow drifts, and snow banks up against ridges.

But it's been calibrated extensively and ice bridge will be put up against it the next month and we can compare them.

Title: Re: Latest PIOMAS update (March)
Post by: jdallen on March 14, 2016, 07:09:52 AM
some information on brine inclusion and brine drainage in sea ice http://pure.au.dk/portal/files/84136596/Galley_et_al_2015_MRI.pdf (http://pure.au.dk/portal/files/84136596/Galley_et_al_2015_MRI.pdf)
Purely speculative on my part.

Anecdotally, something appears to be rendering the ice less structurally sound.  What are the physics that could do that?  Voids/brine may not be the cause.  What might?
Title: Re: Latest PIOMAS update (March)
Post by: Peter Ellis on March 14, 2016, 12:21:07 PM
Instead of focusing on models, you should be focusing on the actual sea ice.  It is not solid -- it is full of large holes like swiss cheese.  The ice now is nothing like it was in 2012. 
What do you mean by "large"?  What size are these holes, where are they, and what methods were used to detect them?  Without giving more detail on what physical processes you're talking about, it's very difficult to have any kind of meaningful discussion.


some information on brine inclusion and brine drainage in sea ice http://pure.au.dk/portal/files/84136596/Galley_et_al_2015_MRI.pdf (http://pure.au.dk/portal/files/84136596/Galley_et_al_2015_MRI.pdf)
Purely speculative on my part.

Anecdotally, something appears to be rendering the ice less structurally sound.  What are the physics that could do that?  Voids/brine may not be the cause.  What might?

Since you're not even sharing the detail of the anecdotes, it's really hard to comment.  If this relates to Professor Barber's description of "rotten ice", then he was quite clear about what was going on.  A mixture of first year ice  "glue" holding together the rubble of older ice presents a surface signature quite similar to old ice, meaning that remote microwave sensors can be misled about what type of ice is present in a given region. This has absolutely nothing to do with brine pockets per se (except that first year ice has more brine).  Brine channels are very small structures - of the order of millimetres across - and cannot be detected directly by satellites!

If you're referring to the breakout effects currently visible in the Beaufort - i.e. a mobile, fractured pack with lots of leads - then there is again a question of scale, this time in the other direction. These are giant structures in the Arctic ice that can only really be seen from orbit.  Remember that a "vast floe" in sea ice term is a floe that's 2-10 km across, i.e. up to two pixels on the AMSR-E maps.  Professor Barber's observations of vast floes of rotten ice are far too small to be meaningfully compared to the microwave data.


So I pose the same question I put to Tenney.  What holes are you talking about, and when you say "structurally sound", what scale are you referring to?  What is the underlying evidence, and is there good enough data from a multi-year time series to say that there is an ongoing trend in structural soundness?
Title: Re: Latest PIOMAS update (March)
Post by: jdallen on March 14, 2016, 04:59:35 PM
<snippage>
some information on brine inclusion and brine drainage in sea ice http://pure.au.dk/portal/files/84136596/Galley_et_al_2015_MRI.pdf (http://pure.au.dk/portal/files/84136596/Galley_et_al_2015_MRI.pdf)
Purely speculative on my part.

Anecdotally, something appears to be rendering the ice less structurally sound.  What are the physics that could do that?  Voids/brine may not be the cause.  What might?

Since you're not even sharing the detail of the anecdotes, it's really hard to comment.

<snippage>

So I pose the same question I put to Tenney.  What holes are you talking about, and when you say "structurally sound", what scale are you referring to?  What is the underlying evidence, and is there good enough data from a multi-year time series to say that there is an ongoing trend in structural soundness?
Sorry to be frustratingly unclear Peter.  I was musing vaguely rather than trying to provoke a definitive replay, for which I apologize.

As the question posed is tied to an anecdotal observation, it is quite reasonable in fact to expect no such thing actually exists, and I'm quite willing to accept that conclusion.

And in fact, at the micro scale, I'm reasonably confident that the ice forming mechanisms haven't changed, and FYI is still FYI as it has been all along; there's just a lot more of it.  When I presented my vague and rhetorical questions, that's really what I was aiming at.

AS to the macro scale, I believe you are alluding to the two images of the Beaufort I posted elsewhere (March 13 this year vs April 19th last).  There I'm not suggesting holes, but instead suggesting there is similar over-all structure and composition in the pack across the region captured.  That I think may have implications for the coming melt season, as if the Beaufort ice is a month or more ahead of schedule, we skip conditioning previously required to prepare the ice for losses later in the season.

It's far from a perfect correlation though, as the attendant conditions - temperature and insolation specifically - are much different as we haven't yet reached the equinox.  It's unclear to me as yet what it actually means.  But speculating (that dangerous word again...), I'd say current conditions of the ice (in the Beaufort at least) are such that given equivalent weather conditions the melt season will ramp up a week or two earlier than last year.
Title: Re: Latest PIOMAS update (April)
Post by: Wipneus on April 05, 2016, 09:36:38 AM
Yes, PSC has updated their PIOMAS  daily volume data. I updated my graphics, see the top post (http://forum.arctic-sea-ice.net/index.php/topic,119.msg1562.html#msg1562)

Monthly and daily gridded thickness data also updated , I will post the graphics here later.
Title: Re: Latest PIOMAS update (April)
Post by: jdallen on April 05, 2016, 05:47:06 PM
So, volume of 22.33^10x3 KM3 on April 1st divided by CT area of 12.65^10x6 KM2 for the same date gives us an average thickness of about 1.77 meters.
Title: Re: Latest PIOMAS update (April)
Post by: Wipneus on April 05, 2016, 05:52:56 PM
Animation of the daily ice thickness for March.

Click to start the 3 Meg animation.
Title: Re: Latest PIOMAS update (April)
Post by: Wipneus on April 05, 2016, 06:04:07 PM
And the (average) thickness map for March, and the difference with 2007-2015. 2016 seems to be different to each of them, the ice in the eastern Beaufort is about the thinnest of the lot. Ess and Chukchi have remarkably thick ice cover.
Title: Re: Latest PIOMAS update (April)
Post by: Wipneus on April 05, 2016, 06:21:01 PM
BTW. I fixed the animation for February as well. I was wrong by one year. The excuse is that the piomas files are sometimes confusing at the moment caused by the leap year. There are four months now with the fourth month apparently only one day in it.  I (have to) do the same, sometimes ignoring the leap day and sometimes not.
Title: Re: Latest PIOMAS update (April)
Post by: Neven on April 05, 2016, 10:56:13 PM
Ess and Chukchi have remarkably thick ice cover.
I'm still wondering about this. How can it be so much thicker there than in previous years after such a warm winter? There was no ice there at the end of the melting season, and first-year ice doesn't get much thicker than 2m, right?

The radar and CryoSat comparisons I made for the 2015/2016 Winter analysis also don't show thicker ice there:

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fneven1.typepad.com%2F.a%2F6a0133f03a1e37970b01b8d1b50b25970c-800wi&hash=c9e003f2cdd9e557c1b5f2153c3d213f)

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fneven1.typepad.com%2F.a%2F6a0133f03a1e37970b01b7c82a9c38970b-800wi&hash=107b2a8fd526a5be5ea3c4cfa920957e)
Title: Re: Latest PIOMAS update (April)
Post by: AmbiValent on April 05, 2016, 11:53:43 PM
Once again, different models predict very different volume and thickness values... but given the development of area and extent, this promises to be an interesting melt season - interesting as in terrifying to those who can imagine what a mostly ice-free Arctic Ocean will do to NH weather...
Title: Re: Latest PIOMAS update (April)
Post by: seaicesailor on April 06, 2016, 12:47:53 AM
Ess and Chukchi have remarkably thick ice cover.
I'm still wondering about this. How can it be so much thicker there than in previous years after such a warm winter? There was no ice there at the end of the melting season, and first-year ice doesn't get much thicker than 2m, right?

The radar and CryoSat comparisons I made for the 2015/2016 Winter analysis also don't show thicker ice there...
Just to add as another (very local but reliable) observation that buoy 2015F reports a thickness of about 189 cm at a  location 81 N, in sector north of Beaufort, where Piomas predicts between 2 and 3m at the end of simulation. Remind also that the buoy in anchored in MYI, not FYI.

So yeah maybe PIOMAS went a bit wild in some areas?

PS. I am forgetting the pressure ridges, that constitute a big proportion of volume and average thickness. Maybe just as Beaufort got stretched and opened new cracks, ESS got compressed and piled up ice, and PIOMAS captured that drift effect.

Title: Re: Latest PIOMAS update (April)
Post by: DrTskoul on April 06, 2016, 12:48:20 AM
Ess and Chukchi have remarkably thick ice cover.
I'm still wondering about this. How can it be so much thicker there than in previous years after such a warm winter? There was no ice there at the end of the melting season, and first-year ice doesn't get much thicker than 2m, right?

I am with u Neven. Those radar images have proven a great proxy for thickness variation between different years. Reality would not be far off.  The question is what data does PIOMAS lack resulting to the thickening trajectory of the model? Water temperatures? Sth else?
Title: Re: Latest PIOMAS update (April)
Post by: jdallen on April 06, 2016, 01:54:07 AM
Ess and Chukchi have remarkably thick ice cover.
I'm still wondering about this. How can it be so much thicker there than in previous years after such a warm winter? There was no ice there at the end of the melting season, and first-year ice doesn't get much thicker than 2m, right?

I am with u Neven. Those radar images have proven a great proxy for thickness variation between different years. Reality would not be far off.  The question is what data does PIOMAS lack resulting to the thickening trajectory of the model? Water temperatures? Sth else?
Good questions, DrTskoul.

Judging from some discussion elsewhere about buoy deployment et. al., it seems there have been some cutbacks in funding for Arctic research - at least in so far as the placement of sensors is concerned.

The models are only as good as the initial data they are provided.  Between those points, they have to generalize, using what global information they have available - such as various satellite data streams.  It's far from perfect, but imperfect as it is, it is pretty amazing and even with those imperfections paints a pretty stark picture.

This year, with the astonishing weather, weird snow cover, highly variable coverage of ice (e.g. - the Beaufort and Chukchi thicknesses may be getting thrown off because of many, smaller chunks of MYI ice embedded in the mix), and then Things We Don't Know all contributing that it may be off is absolutely no surprise.

Now that we have daylight, we can watch Worldview, wait for Icebridge data, and things will become quite a bit more definitive.
Title: Re: Latest PIOMAS update (April)
Post by: Michael Hauber on April 06, 2016, 02:50:21 AM
Ess and Chukchi have remarkably thick ice cover.
I'm still wondering about this. How can it be so much thicker there than in previous years after such a warm winter? There was no ice there at the end of the melting season, and first-year ice doesn't get much thicker than 2m, right?

The radar and CryoSat comparisons I made for the 2015/2016 Winter analysis also don't show thicker ice there:

[/quote]

The warmth was largely towards the Atlantic, and also towards Beaufort.  While ESS was still definitely above average, it was probably something much more typical of what we have seen in the last decade.  Combine that with stronger than normal wind towards Siberia (consider how cold Sea of Okhostk has been and how high ice compared to recent years) causeing higher ice transport, then it would be no surprise that we see thicker ice in this region.  However is not showing thicker ice here, so maybe measurement difficulties on Cryosat's part.  Or perhaps the Beaufort Gyre is deflecting ice around the corner towards Laptev instead of piling it up towards Siberia as Piomas is presumably modelling.
Title: Re: Latest PIOMAS update (April)
Post by: seaicesailor on April 06, 2016, 08:53:36 AM
Ess and Chukchi have remarkably thick ice cover.
I'm still wondering about this. How can it be so much thicker there than in previous years after such a warm winter? There was no ice there at the end of the melting season, and first-year ice doesn't get much thicker than 2m, right?

I am with u Neven. Those radar images have proven a great proxy for thickness variation between different years. Reality would not be far off.  The question is what data does PIOMAS lack resulting to the thickening trajectory of the model? Water temperatures? Sth else?

Still can CRYOSAT resolve thickening in ridges by compression? Serious doubt we should address.
PIOMAS can estimate it (not resolve the ridges directly but estimate the increased effective thicknesss by ice accumulation).
The other are not radar strctly speaking and do not show thickness but different quality (age) of ice.
Title: Re: Latest PIOMAS update (April)
Post by: seaicesailor on April 06, 2016, 12:43:58 PM
This is an example of recent ice drift: observe the divergence of drift vectors at Beaufort (which causes coast water opening, stretching of ice and opening of leads). This does not contribute to ice volume increase given the overall expansion in that given closed area (rather decrease and export out of the Beaufort, even when the leads and openings refreeze). However note the converging of ice drift vectors at CAB side of ESS. That causes ice compression and subsequent pressure ridges. For that given closed area, volume increases just by drift ice compression.

The question that is not clear to me is that if CryoSat can resolve that ice accumulation that goes to pressure ridges, since, given the small area that pressure ridges occupy with respect to the rest of the ice cap, the radar signal of these ridges (reaching back the satellite slightly before the main signal) will be extremely weak.

However, it is known that pressure ridges can accumulate a vast amount of ice volume (reference missing)*.

I should look for a map of overall drift of the past months, but just this as an illustrative example.

* Wikipedia Entry gives this reference:
Leppäranta, M. (2005). The Drift of Sea Ice. Springer-Verlag, New York, 266 p.
that claims that half the volume of ice could be stored in ridges, but I have not read it, and is a bit old given the evolution of the Arctic

Title: Re: Latest PIOMAS update (April)
Post by: Neven on April 06, 2016, 01:06:36 PM
I should look for a map of overall drift of the past months, but just this as an illustrative example.

Here's average sea ice drift for February, sis:

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fneven1.typepad.com%2F.a%2F6a0133f03a1e37970b01b8d1b50813970c-800wi&hash=5e0f67d8827f3b9962e7b0f460d9d6ab)
Title: Re: Latest PIOMAS update (April)
Post by: seaicesailor on April 06, 2016, 02:08:37 PM
I should look for a map of overall drift of the past months, but just this as an illustrative example.

Here's average sea ice drift for February, sis:

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fneven1.typepad.com%2F.a%2F6a0133f03a1e37970b01b8d1b50813970c-800wi&hash=5e0f67d8827f3b9962e7b0f460d9d6ab)

Thank you!
Wherever the streamlines diverge, or go parallel and the vectors accellerate along the streamlines, the divergence is positive,  the ice expands. That would be in Canada coast and the usual Laptev.
Wherever the streamlines converge and the vectors accelerate, the ice is displaced but the net divergence may be zero or small. That is Fram and (it seems) Chukchi.
And where streamlines converge with no vector change, or vectors along the streamlines decelerate abruptly, there is compression. That seems to be ESS in this map, and very strong, and the usual Greenland/CAA wall.

The electronic version of that book is 200+ €.
Title: Re: Latest PIOMAS update (April)
Post by: Andreas T on April 06, 2016, 02:18:57 PM
...

Still can CRYOSAT resolve thickening in ridges by compression? Serious doubt we should address.
PIOMAS can estimate it (not resolve the ridges directly but estimate the increased effective thicknesss by ice accumulation).
The other are not radar strctly speaking and do not show thickness but different quality (age) of ice.
Chris Reynolds has written last monthhttp://dosbat.blogspot.co.uk/2016/03/piomas-29-february.html (http://dosbat.blogspot.co.uk/2016/03/piomas-29-february.html) on his blog about the thickening in ESS.
I don't know how drift is assimilated into PIOMAS but the increase in very thick ice which can only originate from pressure ridges shows that PIOMAS "sees" this happening on that side. Cryosat by the way also shows thick ice right against the coast but not as large an extent of it (and therefore less volume)
Temperatures along the Siberian coast have not been much warmer than usual as far as I can tell. I have posted some info in the regional thread but don't have time now to dig for data.
Title: Re: Latest PIOMAS update (April)
Post by: seaicesailor on April 06, 2016, 02:34:22 PM
...

Still can CRYOSAT resolve thickening in ridges by compression? Serious doubt we should address.
PIOMAS can estimate it (not resolve the ridges directly but estimate the increased effective thicknesss by ice accumulation).
The other are not radar strctly speaking and do not show thickness but different quality (age) of ice.
Chris Reynolds has written last monthhttp://dosbat.blogspot.co.uk/2016/03/piomas-29-february.html (http://dosbat.blogspot.co.uk/2016/03/piomas-29-february.html) on his blog about the thickening in ESS.
I don't know how drift is assimilated into PIOMAS but the increase in very thick ice which can only originate from pressure ridges shows that PIOMAS "sees" this happening on that side. Cryosat by the way also shows thick ice right against the coast but not as large an extent of it (and therefore less volume)
Temperatures along the Siberian coast have not been much warmer than usual as far as I can tell. I have posted some info in the regional thread but don't have time now to dig for data.

Well, Chris Reynolds amazing analysis as always. ESS has a lot more ice and a lot more ridged thick ice imported compared to 2015, by his analysis using Gice (so PIOMAS model indeed can output thickness distributions). Beaufort however is weakest, more than 2012.

Still cannot find a site on if ridged ice will "escape" from Cryosat radar (anybody? : - ) )
Title: Re: Latest PIOMAS update (April)
Post by: Timothy Astin on April 06, 2016, 05:38:45 PM
The radar footprint given here (https://directory.eoportal.org/web/eoportal/satellite-missions/c-missions/cryosat) is "about 15km" radius, so about 700km2.

Radar reflections are an "averaged" response from this footprint. In areas of sparse pressure ridges, the dominant response will be from large relatively uniform areas of undeformed ice.

The exact shape of the reflected radar wavelet will include contributions of features smaller than this window, like pressure ridges. How much modification will depend on their individual widths, spatial densities, and the distribution of pressure ridge thicknesses.

So there will be areas where pressure ridge contributions to the dominant radar reflections are effectively hidden.  There will be some thresholds of pressure ridge density and depth distribution which means they start to increase the thickness estimate to be larger than that of the areas of undeformed ice.  (There is a large literature on this topic in radar and seismic reflection physics.)
Title: Re: Latest PIOMAS update (April)
Post by: seaicesailor on April 07, 2016, 12:57:17 AM
Thank you Timothy
Title: Re: Latest PIOMAS update (April)
Post by: Frivolousz21 on April 09, 2016, 04:11:53 AM
It's far more likely Cryosat is right and piomas isn't in terms of ice thickness distribution
Title: Re: Latest PIOMAS update (April)
Post by: Neven on May 05, 2016, 12:37:33 AM
I'm going to try and guess the PIOMAS monthly change for April.

Here's the April volume change for other years:

(https://lh3.googleusercontent.com/-W239qlgnOSo/Vyp3zc1A22I/AAAAAAAAC5o/ClwgRwWQylEEj5XloUCgDWkMHEEum3sQwCCo/s171/PIOMAS%2BApril%2Bchange.gif)

The four years with lowest change were 2010, 2013, 2007 and 2015. If I then compare this year's weather patterns (SAT and SLP) for the first and second half of the month (see attachments) with those of previous years, I conclude that volume change will probably be negative. Difficult to say by how much, perhaps -100 km3. Around -50 km3 will be enough to overtake 2011 and go lowest on record.
Title: Re: Latest PIOMAS update (April)
Post by: Wipneus on May 05, 2016, 07:36:28 AM
I'm going to try and guess the PIOMAS monthly change for April.

Here's the April volume change for other years:

(https://lh3.googleusercontent.com/-W239qlgnOSo/Vyp3zc1A22I/AAAAAAAAC5o/ClwgRwWQylEEj5XloUCgDWkMHEEum3sQwCCo/s171/PIOMAS%2BApril%2Bchange.gif)

The four years with lowest change were 2010, 2013, 2007 and 2015. If I then compare this year's weather patterns (SAT and SLP) for the first and second half of the month (see attachments) with those of previous years, I conclude that volume change will probably be negative. Difficult to say by how much, perhaps -100 km3. Around -50 km3 will be enough to overtake 2011 and go lowest on record.

Impressive. Calculating from gridded daily thickness data I get for day 121 22,268 km3. That is a drop of about -70 km3
Strictly it is not enough to beat 2011, on day 121 2011 volume was 22,247 km3. Remember that PIOMAS does not know anything about leap years/days.
Title: Re: Latest PIOMAS update (May)
Post by: Wipneus on May 05, 2016, 07:42:34 AM
Having said that, gridded data was released (despite the F17 troubles) so I can show you the thickness maps. We are still waiting for the daily volume data.

Here is the thickness animation for April. Click to start.
Title: Re: Latest PIOMAS update (May)
Post by: Wipneus on May 05, 2016, 08:00:14 AM
From the monthly (average)  thickness data, here is the April 2016 thickness map and a summary of the differences with previous years. Click for bigger pictures.
Title: Re: Latest PIOMAS update (May)
Post by: Juan C. García on May 05, 2016, 08:54:45 AM
Having said that, gridded data was released (despite the F17 troubles) so I can show you the thickness maps. We are still waiting for the daily volume data.

Here is the thickness animation for April. Click to start.

On your thickness animation for April, it seems that the F17 made some days with distortion on Baffin and Greenland Sea. Maybe they will come back and correct them.

Your animations are great, Wipneus. Thanks for all this work!
Title: Re: Latest PIOMAS update (May)
Post by: Frivolousz21 on May 05, 2016, 10:16:56 AM
There is absoutely no way there is 4m ice that  big of an area In the CAb
Title: Re: Latest PIOMAS update (May)
Post by: crandles on May 05, 2016, 10:29:30 AM
There is absoutely no way there is 4m ice that  big of an area In the CAb

Cryosat scale goes to 3.5m, less but fairly similar. Why "no way"?
Title: Re: Latest PIOMAS update (May)
Post by: magnamentis on May 05, 2016, 01:24:56 PM
as long as the measurement method remains the same we can easily follow the trends but i as well concur that something seems not right with their numbers. i have this feeling for quite some time, for example does it seem a bit off that as soon as a warm front enters a specific area, that the concentration can drop significantly within 2-3 days where is 4m thick ice, as well, even if that would only appear so due to melt ponds etc. that ice appears too fractured to be solid 4m thick in large areas. i suspect that ridges play a big role in this as well as relying on experience from earlier years 15-30 years ago which are applied in their algorithms that calculate the how deep a specific ice mass is reaching as an average. time will show, it's just a subjective impression based on various observations and not scientifically founded :-)
Title: Re: Latest PIOMAS update (May)
Post by: slow wing on May 05, 2016, 01:38:55 PM
Without disagreeing with your points, it should be pointed out that the white regions are modeled thickness>3.75m, not 4m.
Title: Re: Latest PIOMAS update (May)
Post by: magnamentis on May 05, 2016, 02:01:19 PM
sure, the numbers were not meant absolute, one user posted a 4M the other 3.5 and you 3.75, it was more a general expression of a feeling that those numbers (which ever LOL) should perhaps be taken with a prise of salt, last but not least, which is what i forgot to mention, when i look at 5 graphs i get 3-4 different impressions as to volume and/or thickness. thanks for feedback however and as i said. the trend is fully visible as long as we compare apples with apples (same charts and images) that are using the same algorithm.
Title: Re: Latest PIOMAS update (May)
Post by: seaicesailor on May 05, 2016, 03:20:00 PM
Really thick ice in ESS, but in the comparison it is very similar to what it was in 2012
Beaufort on the other hand... like waiting for "le coup de grace"

Title: Re: Latest PIOMAS update (May)
Post by: Tor Bejnar on May 05, 2016, 03:32:39 PM
Re Wipneus' "From the monthly (average)  thickness data, here is the April 2016 thickness map and a summary of the differences with previous years."

I find the thin ice 'shadow' next to Wrangel Island (off of eastern Siberia) an interesting feature.  My guess is that late winter/spring ice from Beaufort, Chukchi and East Siberian Seas (Beaufort Gyre) was split by Wrangel Island and ice piled up both east and west of the 'shadow', leaving thicker than normal ice along the (eastern) Siberian coast except for behind Wrangel Island.  This suggests the Beaufort Gyre moved more ice than normal this last month or two.
Title: Re: Latest PIOMAS update (May)
Post by: Andreas T on May 06, 2016, 10:26:19 PM
unfortunately the "shadow" is not covered by this sentinel radar image but it may show the effect of ice pushing against Wrangel island. http://www.polarview.aq/images/106_S1jpgsmall/201605/S1A_EW_GRDM_1SDH_20160503T182915_34F5_N_1.jpg (http://www.polarview.aq/images/106_S1jpgsmall/201605/S1A_EW_GRDM_1SDH_20160503T182915_34F5_N_1.jpg)
Title: Re: Latest PIOMAS update (May)
Post by: werther on May 07, 2016, 11:32:14 PM
Well, on the Polar Science website I saw April coming in. And it's in an on/off battle with 2011 for lowest volume. Somehow, I still think PIOMASS is at the conservative side of history...
This is going to be a nail-biting summer.
Title: Re: Latest PIOMAS update (May)
Post by: crandles on May 08, 2016, 12:35:36 AM
Also looks like anomaly below straight line trend.

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fpsc.apl.uw.edu%2Fwordpress%2Fwp-content%2Fuploads%2Fschweiger%2Fice_volume%2FBPIOMASIceVolumeAnomalyCurrentV2.1.png&hash=d75486bc4e09ac0c665a1e839b46b78a)
Title: Re: Latest PIOMAS update (May)
Post by: Wipneus on May 08, 2016, 10:35:05 AM
Yes, PSC has updated their PIOMAS  daily volume data. I updated my graphics, see the top post (http://forum.arctic-sea-ice.net/index.php/topic,119.msg1562.html#msg1562)

Day-to-day changes in volume are a bit erratic, no doubt the F17 troubles are due to this. Perhaps this will be corrected some day, now (preliminary, but much better) F18 based data are available.
Title: Re: Latest PIOMAS update (May)
Post by: Andreas T on May 08, 2016, 12:01:00 PM
from the graph it looks like April average is below 2011 with maximum just above 2011. From what you say, Wipneus,  the numbers are in a bit of doubt but not surprising in view of the general picture from other parameters.
Looking at the trend for year to year April volume which is lower than the trend for the yearly average, 2016 actually lies clearly below the trend (that Polar Science Center graph does not show April 2016 yet)
http://psc.apl.uw.edu/wordpress/wp-content/uploads/schweiger/ice_volume/BPIOMASIceVolumeAprSepCurrent.png (http://psc.apl.uw.edu/wordpress/wp-content/uploads/schweiger/ice_volume/BPIOMASIceVolumeAprSepCurrent.png)
Title: Re: Latest PIOMAS update (May)
Post by: wanderer on May 08, 2016, 12:34:30 PM
Latest value: 2013-3-31 21.612
Latest value: 2013-4-30 21.273

Latest value: 2016-4-1 22.337
Latest value: 2016-5-1 22.268

Am I misinterpreting something? Why is 2016 lower in the graphs than 2013?
Title: Re: Latest PIOMAS update (May)
Post by: Nick_Naylor on May 08, 2016, 01:14:01 PM
Latest value: 2013-3-31 21.612
Latest value: 2013-4-30 21.273

Latest value: 2016-4-1 22.337
Latest value: 2016-5-1 22.268

Am I misinterpreting something? Why is 2016 lower in the graphs than 2013?

If you are misinterpreting, so am I :)

It sure looks like 2016 is neck-and-neck with 2012:
(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fpsc.apl.uw.edu%2Fwordpress%2Fwp-content%2Fuploads%2Fschweiger%2Fice_volume%2FBPIOMASIceVolumeAnomalyCurrentV2.1_CY.png&hash=71e098ee33c36296b9e24f63de218d71)
Title: Re: Latest PIOMAS update (May)
Post by: crandles on May 08, 2016, 01:14:39 PM
Latest value: 2013-3-31 21.612
Latest value: 2013-4-30 21.273

Latest value: 2016-4-1 22.337
Latest value: 2016-5-1 22.268

Am I misinterpreting something? Why is 2016 lower in the graphs than 2013?

I think you are missing the switch to version 2.1 in 2014.

V2.1 2013 day 90  22.850
v2.1 2013 day 120  22.828

Edit:
It is very close to 2011 figures not 2012.

2016 day 121 22.268, 2011 day 121 22.247
pretty sure that is statistically indistinguishable.
Title: Re: Latest PIOMAS update (May)
Post by: crandles on May 08, 2016, 08:57:19 PM
Day-to-day changes in volume are a bit erratic, no doubt the F17 troubles are due to this. Perhaps this will be corrected some day, now (preliminary, but much better) F18 based data are available.

Yes I see.
Title: Re: Latest PIOMAS update (May)
Post by: abbottisgone on May 09, 2016, 04:13:15 AM
Latest value: 2013-3-31 21.612
Latest value: 2013-4-30 21.273

Latest value: 2016-4-1 22.337
Latest value: 2016-5-1 22.268

Am I misinterpreting something? Why is 2016 lower in the graphs than 2013?

If you are misinterpreting, so am I :)

It sure looks like 2016 is neck-and-neck with 2012:
(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fpsc.apl.uw.edu%2Fwordpress%2Fwp-content%2Fuploads%2Fschweiger%2Fice_volume%2FBPIOMASIceVolumeAnomalyCurrentV2.1_CY.png&hash=71e098ee33c36296b9e24f63de218d71)
Being super-conservative we can say that 2016 is not outside of 2 standard deviations!
Title: Re: Latest PIOMAS update (May)
Post by: crandles on May 09, 2016, 10:03:59 AM

Being super-conservative we can say that 2016 is not outside of 2 standard deviations!

2sd of what? presumably above graph is of 2sd from no change. Whereas it makes more sense to look at deviation from downward linear trend:

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fpsc.apl.uw.edu%2Fwordpress%2Fwp-content%2Fuploads%2Fschweiger%2Fice_volume%2FSPIOMASIceVolumeAnomalyCurrentV2.1.png&hash=aff6c69f17939fc86b642bb378e1c96b)

yep definitely not outside 2 standard deviations  ;) ;D
Title: Re: Latest PIOMAS update (May)
Post by: plinius on May 09, 2016, 11:05:47 AM

Being super-conservative we can say that 2016 is not outside of 2 standard deviations!

2sd of what? presumably above graph is of 2sd from no change. Whereas it makes more sense to look at deviation from downward linear trend:

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fpsc.apl.uw.edu%2Fwordpress%2Fwp-content%2Fuploads%2Fschweiger%2Fice_volume%2FSPIOMASIceVolumeAnomalyCurrentV2.1.png&hash=aff6c69f17939fc86b642bb378e1c96b)

yep definitely not outside 2 standard deviations  ;) ;D

1) you need to look at the monthly data, because the trend varies significantly with the time of the year.
2) You will then see that 2016 is quite a bit below the trend line, though not 2 standard deviations (but who knows, since PIOMAS is assimilating faulty data currently).
Title: Re: Latest PIOMAS update (May)
Post by: crandles on May 09, 2016, 02:25:58 PM
April is month with max volume per piomas so may as well update graph of some trends:

Data is PIOMAS April Sept and annual average data.

Straight line fits

4 parameter gompertz fits. These fit quite well but only a denier would expect flat trend from now on.

So what should we expect?

Firstly I expect the minimum trend curve to be a vertically exaggerated copy of the maximum trend. The less ice you start with the faster albedo feedback can get started.

So what has happened with apparent speed up in rate and then slow down. I think we can make a reasonable guess that this is to do with thick MYI lasting much less time before it melts out or at least down to a more normal FYI thickness. The MYI used to take many years to grow thick but now it doesn't get a chance. More of the ice melted is now FYI and that grows backs to very close to as thick as previous years.

So a short period of rapid decline which then settles down to a slower rate of decline than the linear trend. Not much difference between the straight line trend and the other trend lines I have drawn in to try to reflect what might be expected from this.

Title: Re: Latest PIOMAS update (May)
Post by: werther on May 09, 2016, 10:09:13 PM
Hi Crandles,
Maybe my limited math insight makes me miss the point.
But what are you trying to let us expect in those graphs? A first virtual ice free September somewhere between 2030- '35?
That would spoil my alarmist sensation...
Title: Re: Latest PIOMAS update (May)
Post by: crandles on May 09, 2016, 11:48:52 PM
Hi Crandles,
Maybe my limited math insight makes me miss the point.
But what are you trying to let us expect in those graphs? A first virtual ice free September somewhere between 2030- '35?
That would spoil my alarmist sensation...

We frequently get years below trend, so first virtual ice free could easily be before 2025 and 2016 could get down to around 2k Km^3 even if that purple line has the correct slope (and height) and there seems a lot of uncertainty about its rate to me. 2016 data point could easily shift the fits down and the date forward a few years.

If you are thinking when we normally get virtually ice free rather than fluke first occurrence, that purple line is what I am suggesting for what I think is a reasonable extrapolation given data so far and it is suggesting around 2030 for virtually ice free September.

About 20% steeper slope than slope of expected trend of maximum seems justified from the data but slope of expected trend of both maximum and minimum I find hard to pin down. Since the logic I presented suggests less steep than than linear trend of data shown, I cannot make the slope much steeper but there is more room to make it less steep. Sorry if that spoils your alarmist sensation.

Of course there is plenty of scope for such a wild estimate to be badly wrong. I am assuming a fairly steady increase in GHGs leads to a fairly linear decline in FYI thickness at maximum. The physics could easily be different - perhaps GHGs warms ocean with lag so ocean temps rise more than linearly so the FYI maximum thickness declines more than linearly. Or pick any number of other interacting factors like waves... If I haven't seen evidence for such things being significant I am tending to assume they are insignificant and that can easily be wrong.

The models tend to suggest the rate slows down as the ice disappears. If I took that assumption, that would make it regularly virtually ice free later, possibly much later. The models seem reasonable evidence so perhaps I should incorporate this. (I wouldn't have a clue how much of an effect to build in.)

It is a bit of a wild crap shoot. However, at least I think I have made a reasonable attempt to include sufficient complexity to explain the main features of the data including
* faster decline of minimum than maximum,
* increase then decrease in slopes of trends,
arising from likely dominant feedbacks: albedo feedback in summer and thickness regrowth feedback in winter and physics such as effect of MYI.

If we are to attempt to extrapolate curves, probably sensible to try to keep it as physically based as possible.

My explanation of what I have done and why is probably still lacking so sorry about that and feel free to ask questions about it.
Title: Re: Latest PIOMAS update (May)
Post by: Nick_Naylor on May 12, 2016, 01:57:34 PM
Perhaps this has already been discussed, but I am confused about how to reconcile the two main PIOMAS exhibits - one of which appears to show 2016 tied with 2012 for the lowest maximum volume, while the other seems to show 2016 as the fifth or six-lowest volume. Is there a simple explanation for how to interpret them correctly?

Title: Re: Latest PIOMAS update (May)
Post by: DavidR on May 12, 2016, 02:24:32 PM
Perhaps this has already been discussed, but I am confused about how to reconcile the two main PIOMAS exhibits - one of which appears to show 2016 tied with 2012 for the lowest maximum volume, while the other seems to show 2016 as the fifth or six-lowest volume. Is there a simple explanation for how to interpret them correctly?
The anomalies are monthly measurements from the trend line.  Summer months are much  further below the trend than winter months.  The current figure is from April but it is impossible to tell where April sits in the previous years from the graphs. What  we can see is that this April is very close to a trend line that is declining rapidly.  So maximum anomaly  in 2012 was 8.5 M km^2 below the trend and the current anomaly is 5.5 M km^2 below the trend, but by September it could be 7.5 M km^2 below the trend but  be below 2012 because the trend is dropping  so  fast.

On the other hand we can just get a volumetric measure of the ice which shows that the volume estimate in April was the probably the lowest April volume on record. This is shown in the secod graph.

The trend for summer extent is declining at about 120K km^2 per year so this year could produce a record melt without going within 400K Km^2 or the 2012 anomaly. 
Title: Re: Latest PIOMAS update (May)
Post by: Nick_Naylor on May 12, 2016, 04:02:52 PM
Thanks - I think I understand. On the anomaly graph, the local annual maximum (to the extent it's periodic at all) is out of phase with the volume max.
Title: Re: Latest PIOMAS update (May)
Post by: Wipneus on May 12, 2016, 04:15:51 PM
Thanks - I think I understand. On the anomaly graph, the local annual maximum (to the extent it's periodic at all) is out of phase with the volume max.

Indeed, currently the anomaly max can fall anywhere in January to April. The minimum seems to be these years close to summer solstice. BUT in 2007 and 2008 there was a second deeper minimum in oktober!.

Earlier this century there where no clear min-maxima at all.

(https://sites.google.com/site/arctischepinguin/home/piomas/grf/piomas-trnd3.png)
Title: Re: Latest PIOMAS update (May)
Post by: abbottisgone on May 13, 2016, 03:21:13 AM
Wipneus, that second dip seems to be a recurrent theme in more than those two years!
Title: Re: Latest PIOMAS update (May)
Post by: crandles on May 13, 2016, 10:04:01 AM
Wipneus, that second dip seems to be a recurrent theme in more than those two years!

They seem to be grouped together in height.
2005 slight
2006 is weird - still falling to end of year
2007-2009
and
2014
2015 slight

representing 5th to 9th lowest years, weird 2006 is 10th lowest and 11th lowest.

Becoming a feature and then disappearing again seems odd.

May to July drop seems to become ever more prominent with lower values and then for those low years the recovery in rest of year is more pronounced so perhaps that tends to hide the October dip?
Title: Re: Latest PIOMAS update (May)
Post by: Richard Rathbone on May 13, 2016, 01:30:47 PM
This sort of pattern is down to ice melting out and capping the anomaly. e.g. Hudson Bay is open water in September, so its anomaly is always 0 in September. Earlier melting and later freezing allow for anomaly peaks in June and November, but its always completely covered with first year ice in February so the February anomaly is stuck near 0 too.

The ice for the whole arctic doesn't get close enough to 0 yet for this pattern to always manifest when the whole arctic is lumped together but because the anomaly in September is capped at a lower value than June or November anomalies, it will eventually appear regularly in the total anomaly as well as regional ones.
Title: Re: Latest PIOMAS update (May)
Post by: abbottisgone on May 16, 2016, 05:54:10 AM
This sort of pattern is down to ice melting out and capping the anomaly. e.g. Hudson Bay is open water in September, so its anomaly is always 0 in September. Earlier melting and later freezing allow for anomaly peaks in June and November, but its always completely covered with first year ice in February so the February anomaly is stuck near 0 too.

The ice for the whole arctic doesn't get close enough to 0 yet for this pattern to always manifest when the whole arctic is lumped together but because the anomaly in September is capped at a lower value than June or November anomalies, it will eventually appear regularly in the total anomaly as well as regional ones.
I might have to re-read that several times but it's good to know there is logic following this trail of events.

 :)
Title: Re: Latest PIOMAS update (May)
Post by: OSweetMrMath on May 19, 2016, 11:19:52 PM
I was inspired by https://tamino.wordpress.com/2016/05/16/arctic-dive/ (https://tamino.wordpress.com/2016/05/16/arctic-dive/) to create an anomaly graph for PIOMAS volume. The first graph (attached below) shows the PIOMAS daily volume data (in black) along with the fitted model (in red), based on a linear trend and a Fourier seasonal component. If you look closely, you can see that I've included cross-product terms, so the size (and shape) of the seasonal component changes over the time period.

The second graph shows the daily anomalies from the fitted model. Recent years are colored and thicker, with red for 2010, orange for 2011, yellow for 2012, green for 2013, blue for 2014, and purple for 2015. 2016 so far is a thick black line.

The big take away from this graph is that in both 2010 and 2012, the negative anomalies increased sharply starting at the end of April, resulting in the low observed minimum volumes in both years. In contrast, the anomalies in 2011 were low for the entire year, the anomalies in 2013 rose through the year, and the anomalies in 2014 and 2015 were positive.

The question for this year is whether the anomaly will behave the same way as in 2012. The fitted model predicts a daily minimum of 5.14 thousand cubic km. Recent anomalies have been around -0.5, so if this holds, the daily minimum will be around 4.6 thousand cubic km. If the anomalies follow the behavior of 2012, the daily minimum will be 2.4 thousand cubic km.
Title: Re: Latest PIOMAS update (May)
Post by: Richard Rathbone on May 20, 2016, 04:01:33 PM
Nice piece of work.
Title: Re: Latest PIOMAS update (May)
Post by: epiphyte on May 21, 2016, 09:00:43 AM

The question for this year is whether the anomaly will behave the same way as in 2012. The fitted model predicts a daily minimum of 5.14 thousand cubic km. Recent anomalies have been around -0.5, so if this holds, the daily minimum will be around 4.6 thousand cubic km. If the anomalies follow the behavior of 2012, the daily minimum will be 2.4 thousand cubic km.


... I'm not sure that I completely follow, but if I'm understanding this right then there remains an ambiguity w.r.t whether,in 2012, a) PIOMAS departed from reality sometime _before_ April, resulting in spring/summer forcing downward as areas were unexpectedly observed to drop to zero, or b) PIOMAS was right the whole time, and the unprecedented real-world behavior later on was correctly modeled as the year progressed.

For my own part I've always felt that the former is more likely the case, which is one of the things that makes me inclined to distrust PIOMAS w.r.t. the last meter of ice thickness, (other than perhaps in Nov/Dec for newly-formed FYI).
Title: Re: Latest PIOMAS update (May)
Post by: Dorsetmetman on May 21, 2016, 10:53:18 AM
OSweetMrMath these are two great charts and have really helped my understand the PIOMASS anomaly graphs. Tell me, if you extend your red modelled line forward, in which year does it reach zero volume?
Title: Re: Latest PIOMAS update (May)
Post by: werther on May 21, 2016, 12:34:35 PM
Thanks Mathmaster!