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Author Topic: Latest PIOMAS update (May 2019)  (Read 939921 times)

abbottisgone

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Re: Latest PIOMAS update (May)
« Reply #900 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:

Being super-conservative we can say that 2016 is not outside of 2 standard deviations!
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crandles

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Re: Latest PIOMAS update (May)
« Reply #901 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:



yep definitely not outside 2 standard deviations  ;) ;D

plinius

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Re: Latest PIOMAS update (May)
« Reply #902 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:



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).

crandles

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Re: Latest PIOMAS update (May)
« Reply #903 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.


werther

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Re: Latest PIOMAS update (May)
« Reply #904 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...

crandles

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Re: Latest PIOMAS update (May)
« Reply #905 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.

Nick_Naylor

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Re: Latest PIOMAS update (May)
« Reply #906 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?


DavidR

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Re: Latest PIOMAS update (May)
« Reply #907 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. 
« Last Edit: May 12, 2016, 02:31:51 PM by DavidR »
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Nick_Naylor

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Re: Latest PIOMAS update (May)
« Reply #908 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.

Wipneus

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Re: Latest PIOMAS update (May)
« Reply #909 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.


abbottisgone

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Re: Latest PIOMAS update (May)
« Reply #910 on: May 13, 2016, 03:21:13 AM »
Wipneus, that second dip seems to be a recurrent theme in more than those two years!
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crandles

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Re: Latest PIOMAS update (May)
« Reply #911 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?

Richard Rathbone

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Re: Latest PIOMAS update (May)
« Reply #912 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.

abbottisgone

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Re: Latest PIOMAS update (May)
« Reply #913 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.

 :)
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OSweetMrMath

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Re: Latest PIOMAS update (May)
« Reply #914 on: May 19, 2016, 11:19:52 PM »
I was inspired by 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.

Richard Rathbone

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Re: Latest PIOMAS update (May)
« Reply #915 on: May 20, 2016, 04:01:33 PM »
Nice piece of work.

epiphyte

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Re: Latest PIOMAS update (May)
« Reply #916 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).

Dorsetmetman

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Re: Latest PIOMAS update (May)
« Reply #917 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?

werther

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Re: Latest PIOMAS update (May)
« Reply #918 on: May 21, 2016, 12:34:35 PM »
Thanks Mathmaster!

Given the temp record so far this year (DMI +80dgN), your graph makes me wonder whether the black line will dive down like the red and yellow ones.
Will be exciting to follow! Keep it up to date.

Tor Bejnar

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Re: Latest PIOMAS update (May)
« Reply #919 on: May 21, 2016, 03:22:36 PM »
On the ASIB, Chris Reynolds wrote
Quote
...
Anyway, check out the PIOMAS site.
http://psc.apl.uw.edu/research/projects/arctic-sea-ice-volume-anomaly/

They have updated a comparison between PIOMAS and Cryosat2.
http://psc.apl.uw.edu/wordpress/wp-content/uploads/schweiger/ice_volume/CryoSat_2012_2016_feb.png
That shows the difference between Feb 2012 and Feb 2016 in Cryosat 2(left) and PIOMAS (right).

The agreement is very good.

By eye, it looks like about half of the 'agreement' is excellent (e.g., Beaufort Sea), and some parts are really bad, such as eastern Kara Sea.  Someone with the technology & some skill could do a point by point comparison!
Arctic ice is healthy for children and other living things.

A-Team

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Re: Latest PIOMAS update (May)
« Reply #920 on: May 21, 2016, 04:24:53 PM »
Quote
point by point comparison?
To me, the agreement looks mediocre. In cases of gross conflict, which should be believed?

The graphic itself is a disgrace, unpublishable. Years and years of work, hundreds of millions of dollars -- the data deserves a better comparison especially since it is important and so simple to do it right.

For starters, the coordinate systems show different areas and cannot be aligned as provided. That in itself is utterly unacceptable but is compounded by an asinine choice of diverging non-quantifiable palette. When I see two entry level mistakes in a single product, I have to wonder what else was done wrong in processing the data.

And why are visitors left to do the quantitative comparison? It was really the job of this web site to provide an accurate difference map -- all they had to do was subtract two netCDF arrays and click a map button. Or do it both ways.

I am not seeing an error map, again something trivial to produce and ubiquitous (at least in Greenland research). That's a huge issue on something like [(Cryo16 - Cryo12) - (Pio16 - Pio12)] where error is accumulating at each step. Even if we could do a quantitative graphical subtraction, we would have no idea if the differences were statistically significant.

Look sometime at graphics from the Eric Rignot group. We cannot expect the average scientist to work at their research level but others could follow along on how data is supposed to be presented.
« Last Edit: May 21, 2016, 04:48:31 PM by A-Team »

abbottisgone

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Re: Latest PIOMAS update (May)
« Reply #921 on: May 21, 2016, 05:03:52 PM »
I was inspired by 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.
I agree: very nice work!

What year is the thin grey line down the bottom or is it two years crossing each other one going up and one going down?
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crandles

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Re: Latest PIOMAS update (May)
« Reply #922 on: May 21, 2016, 05:17:29 PM »


3rd graph on https://sites.google.com/site/arctischepinguin/home/piomas

doesn't seem to have those two low lines?

abbottisgone

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Re: Latest PIOMAS update (May)
« Reply #923 on: May 21, 2016, 05:36:50 PM »


3rd graph on https://sites.google.com/site/arctischepinguin/home/piomas

doesn't seem to have those two low lines?
I was talking about omrmaths 2nd graph where some were in colour but most were in grey...

Out of interest I wondered what the grey lines at the very bottom were!!
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Wipneus

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Re: Latest PIOMAS update (May)
« Reply #924 on: May 21, 2016, 06:51:07 PM »

3rd graph on https://sites.google.com/site/arctischepinguin/home/piomas

doesn't seem to have those two low lines?

My anomaly should be the same as in the official APL/PSC's anomaly graph: it is the difference of the daily actual volume with the average (calculated from 1979-2015) for the day. There is no modeling of year-to-year difference in the "normal" volume.

OSMM's "anomaly" is better described as the residuals of the daily volume data with his particular fitted  model. To interpret the residuals, you must interpret the model as well.

Yuha

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Re: Latest PIOMAS update (May)
« Reply #925 on: May 21, 2016, 07:16:14 PM »
I was talking about omrmaths 2nd graph where some were in colour but most were in grey...

Out of interest I wondered what the grey lines at the very bottom were!!

OSMM's "anomaly" is better described as the residuals of the daily volume data with his particular fitted  model. To interpret the residuals, you must interpret the model as well.

Most importantly OSMM's anomaly is with respect to linear trend not with respect to average. The grey/black curves at the bottom are 1981 and 1982 (I think) with high volumes compared to recent years but low with respect to the trend.

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Re: Latest PIOMAS update (May)
« Reply #926 on: May 21, 2016, 11:17:37 PM »
I should confirm Wipneus' and Yuha's comments. Wipneus' graph shows the difference for each day from the average for that day. Since recent years generally have less ice than earlier years, all recent years appear toward the bottom of his graph.

My graph shows the difference from the volume including the linear trend. Therefore the difference shown is computed from the expected ice volume in that year, and any year can appear at a positive or negative position on my graph. As Wipneus said, I could also have labeled my graph as showing the model residuals. In fact, I originally wrote my post using the word "residuals", until I saw that Tamino used "anomaly" for his graph. I changed my terms to match the language more commonly used here.

I showed every year since 1979 on my graph, but I only labeled the most recent years. The lowest line on the graph is for the end of 1981 and the beginning of 1982. If you look closely at the graph of the data and the model, you can see that the ice was far below the model from the summer of 1981 through the summer of 1982. Looking at the anomaly graph, the line for 1981 starts mixed in with the other years. It starts falling rapidly around day 125 (the beginning of May) and is the lowest line on the graph from day 200 (mid-July) through the end of the year. 1982 starts where 1981 ended. From there it rises, crossing the line for 1981 at about day 200 and returning to more typical anomaly levels by the end of the year.

In response to Epiphyte and others, the PIOMAS data is itself the output of a model, and so it is fair to ask if the PIOMAS data contains errors or biases. My response is that it doesn't particularly matter, as long as the bias is consistent. If it is true that PIOMAS overestimates volume during the early Spring in years with low volume, then as long as that overestimate is similar every year, comparing the data for different years is still valid.

Dorsetmetman asked when the model will reach an ice free level. I would expect the model to be reasonably accurate for short term predictions, but even then you need to take the variability of the anomaly into account. The model says this year's minimum will be 5.1 thousand cubic km. But the most recent anomaly was -0.5 thousand cubic km. If we stay at that level, the minimum will be 4.6 thousand cubic km. And the data is three weeks out of date, and we've all seen what's been happening to the ice in that time. If this year turns into a year like 2012, the anomaly at the minimum could be around -2.5 thousand cubic km, in which case the minimum will be 2.6 thousand cubic km. These all are plausible outcomes. Even if the anomaly in September this year is -2.5 thousand cubic km, the anomaly next September could be 0, in which case we'll get to go through another round of claims of a recovery.

I am very skeptical of the prediction accuracy for this model more than a year or two in advance. Using the model to predict when the Arctic will be ice free just isn't statistically valid, and there's no physical support for long term predictions either. (There is no physical support for this model at all! It's entirely statistical.) If you must know, the model currently reaches zero in 2032, 16 years from now. For comparison purposes, I rebuilt the model only using data through 2000, 16 years ago. The difference between the most recent data and the predicted value for that date is 3.8 thousand cubic km. In 2012, the error was as large as 7.15 thousand cubic km. The anomalies for the data fitted by the model can be quite large, but the anomalies for data outside that time period can be far worse.

epiphyte

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Re: Latest PIOMAS update (May)
« Reply #927 on: May 22, 2016, 06:12:13 PM »

In response to Epiphyte and others, the PIOMAS data is itself the output of a model, and so it is fair to ask if the PIOMAS data contains errors or biases. My response is that it doesn't particularly matter, as long as the bias is consistent. If it is true that PIOMAS overestimates volume during the early Spring in years with low volume, then as long as that overestimate is similar every year, comparing the data for different years is still valid.


OSMM - Really appreciate the response, and concur with what you're saying... but the root of my speculation is that the PIOMAS overestimate may _not_ be similar every year, but rather might increase as average thickness decreases - especially as the proportion of area modeled in the 2-1m range grows vs. well-established MYI.

The reasoning behind this is that thin ice is more unpredictable than thick ice because... well, it's a far from perfect analogy, but because a falling brick has a more predictable trajectory than a falling sheet of paper.

lf there's any truth to this, then for any given modeled volume the spring PIOMAS error would grow in proportion to the total SIA in Mar/Apr... wondering if that's a possibility you can easily test?

S.Pansa

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Re: Latest PIOMAS update (May)
« Reply #928 on: May 28, 2016, 07:17:09 AM »
I was browsing on NASAs Worldview this morning and was quite surprised by the dire state of the ice in the Chukchi along the Siberian coast.
According to PIOMAS and TOPAZ4 for instance, the ice was supposed to be around 4 meters thick there. Hence I thought it would work as a strong fire wall against an early meltout.
But if I compare the Worldview images from 18th and 27th May - unfortunately a bit cloudy, the 26th is a little bit better  - I get the impression that the ice is deteriorating quickly (to me it seems it is not just drifting, it is melting as not just the ice edge is effected).
I am aware that a look from above is not the best way to judge volume - but from what I have observed in the past years, 4 meter thick ice does not give in so easy, especially not this early in the melting season.

What do you guys think?
Is it a case of wrong expectations, bad observation on my side?
Or might this be an indication that the Models did overestimate the ice volume in this area?
Or perhaps 4 meter thick first year ice does really melt out this fast (even though the temps weren't that extreme in the last week)?

Thanks!

Edit: Oh Pansa you idiot. I completely forgot to check Cryosat2. It shows thick ice there as well.
@ abbotisgone: I think it is possible through compaction, but I'll better leave that to the experts on the forum
« Last Edit: May 28, 2016, 07:33:50 AM by S.Pansa »

abbottisgone

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Re: Latest PIOMAS update (May)
« Reply #929 on: May 28, 2016, 07:26:59 AM »
..I didn't think first year ice got 4 metres thick!
..
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Re: Latest PIOMAS update (May)
« Reply #930 on: May 28, 2016, 09:15:39 AM »
I was browsing on NASAs Worldview this morning and was quite surprised by the dire state of the ice in the Chukchi along the Siberian coast. ...
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Re: Latest PIOMAS update (May)
« Reply #931 on: May 28, 2016, 11:58:26 AM »
Thanks for this, S.Pansa!
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Re: Latest PIOMAS update (May)
« Reply #932 on: May 28, 2016, 12:17:10 PM »
yes, hum, hum little problem here ! (also)
I think the ice is more fragile this days, it may not be a problem with the satellites but with the ice piling up more easily thus making the ice appear thick when it is just a pile of "junk ice"
http://go.nasa.gov/1X2Swfe

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Re: Latest PIOMAS update (May)
« Reply #933 on: May 28, 2016, 12:47:27 PM »
..I didn't think first year ice got 4 metres thick!

me neither, i don't think it's 4m thich frozen but in a way piled up through currents and winds driving relative new and therefore (flexible) ice in certain spots where they reach some hights. might be wrong, just a laymen's idea :-)
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Re: Latest PIOMAS update (May)
« Reply #934 on: May 28, 2016, 01:34:04 PM »
Piling up as El Nino has diverted some of the warm currents reaching the Bering? These areas could well keep the ice above the minimum record this year. Not that I'm entirely trusting Topaz. There was some talk (also by me) that the map would show maximum thickness and not be reliable wrt whole patch of ice. But as it shows on other systems too there is likely a thick mess of first year floes sideways and on top of eachother every which way that may slowly distangle?(is that a word? Ah it's 'disentangle') during melt. Even in Baltic these formations can be 3 m high but of course here these are not as extensive as in Arctic
« Last Edit: May 28, 2016, 01:46:44 PM by Pmt111500 »
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Re: Latest PIOMAS update (May)
« Reply #935 on: May 28, 2016, 02:13:03 PM »
I was browsing on NASAs Worldview this morning and was quite surprised by the dire state of the ice in the Chukchi along the Siberian coast.
According to PIOMAS and TOPAZ4 for instance, the ice was supposed to be around 4 meters thick there. Hence I thought it would work as a strong fire wall against an early meltout.
But if I compare the Worldview images from 18th and 27th May - unfortunately a bit cloudy, the 26th is a little bit better  - I get the impression that the ice is deteriorating quickly (to me it seems it is not just drifting, it is melting as not just the ice edge is effected).
I am aware that a look from above is not the best way to judge volume - but from what I have observed in the past years, 4 meter thick ice does not give in so easy, especially not this early in the melting season.

What do you guys think?
Is it a case of wrong expectations, bad observation on my side?
Or might this be an indication that the Models did overestimate the ice volume in this area?
Or perhaps 4 meter thick first year ice does really melt out this fast (even though the temps weren't that extreme in the last week)?
...

I have posted my reply on the siberian arctic thread
 
to have a fact based discussion on a thread which does not fill up as quickly with chatter and opinion based guessing. It is best to look at movement on the basis of identifiable floes or areas. This is more time consuming and laborious than a throw away comment, but the models and measurements of three independent sources deserve a bit more thought before dismissing them so readily.
« Last Edit: May 28, 2016, 06:45:22 PM by Andreas T »

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Re: Latest PIOMAS update (May)
« Reply #936 on: May 28, 2016, 10:54:40 PM »
I am sorry to be a bother if I am overlooking something obvious, Wipneus, but when trying to see when the thickening east of Wrangel island occurred I came across an apparent inconsistency in the Jan 2016 and Feb 2016 animations: Jan 31  looks different (much less thickness east of Wrangel) from the way it looks at the start of the Feb2016 animation
http://forum.arctic-sea-ice.net/index.php/topic,119.msg69488.html#msg69488
http://forum.arctic-sea-ice.net/index.php/topic,119.msg71526.html#msg71526
Is there somewhere else I should look?

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Re: Latest PIOMAS update (May)
« Reply #937 on: May 29, 2016, 03:27:53 PM »
I am sorry to be a bother if I am overlooking something obvious, Wipneus, but when trying to see when the thickening east of Wrangel island occurred I came across an apparent inconsistency in the Jan 2016 and Feb 2016 animations: Jan 31  looks different (much less thickness east of Wrangel) from the way it looks at the start of the Feb2016 animation
http://forum.arctic-sea-ice.net/index.php/topic,119.msg69488.html#msg69488
http://forum.arctic-sea-ice.net/index.php/topic,119.msg71526.html#msg71526
Is there somewhere else I should look?

Something was wrong, I guess I was showing 2015 instead of 2016. It should be fixed now.

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Re: Latest PIOMAS update (May)
« Reply #938 on: May 30, 2016, 04:49:58 AM »
Looking with max zoom on current images suggests the ice is in significantly better shape than on the Alaskan side of Chukchi.  Many more smaller floes and swirly smoke looking stuff on the Alaskan side.  Still looks a lot worse than Beaufort though.  But Beaufort is a nice pristine white colour suggesting little or no surface melting and the ice in the Chukchi has a serious blue tinge showing surface melt underway.  Enough difference vs Alaskan side for 4m?  I have no idea.

Looking at the current hycom image suggests much less thicker ice on the Siberian vs Beaufort side, and feels more reasonable to me.  Hycom has come under fire on this forum for showing thick ice in places that then melt out, going from >2m to 0 in a day or so.  For instance the thick chunk currently near the neck of the Bering.  That may perhaps have been that thick a month or so ago, but I doubt is currently anywhere near that.
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Re: Latest PIOMAS update (May)
« Reply #939 on: May 30, 2016, 08:42:56 AM »
Just use cryosat it's highly accurate.
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Re: Latest PIOMAS update (May)
« Reply #940 on: June 04, 2016, 12:43:41 AM »
I'm going to try again and eyeball PIOMAS May volume loss. First of all, volume decline during May:



And here are the SAT anomaly and SLP mean distribution maps for 1-15 and 16-31 May:



It's clear what caused 2010 to lose so much volume: Both high temps and high pressure. But 2012 did even better during the second half of May even though SAT and SLP aren't higher! Is it because of that Dipole causing increased transport towards the Atlantic?

No Dipole this year, but temps and pressure are pretty high. First half of May looks similar to 2012, and second half looks similar to 2011 (slightly cooler, but maybe some momentum from first half). That's almost -3000 km3, combined.

I don't think it will come close to the -3500 km3 of 2010 and 2012, but May 2016 should be able to come in lower than 2011's -2800 km3 and 2014's -2650 km3.

So, around -3000 km3 is my guess, plusminus 100 km3. That would make 2016 lowest on record.
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Re: Latest PIOMAS update (June)
« Reply #941 on: June 04, 2016, 12:55:30 PM »
Gridded daily and monthly thickness data is now available. The official volume data not yet. From the daily gridded thickness I estimate that volume on day 152 is 19200 [km3].

The thickness maps will be published soon.

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Re: Latest PIOMAS update (June)
« Reply #942 on: June 04, 2016, 01:09:03 PM »
Here is the animation.
« Last Edit: June 04, 2016, 02:00:52 PM by Wipneus »

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Re: Latest PIOMAS update (June)
« Reply #943 on: June 04, 2016, 01:11:05 PM »
For comparison, previous low years at day 152:

Year   Day   Volume
2015   152   21.390
2013   152   20.390
2010   152   20.100
2014   152   20.075
2012   152   19.416
2011   152   19.356

Wipneus

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Re: Latest PIOMAS update (June)
« Reply #944 on: June 04, 2016, 01:28:29 PM »
Here is the (average) thickness for May and the differences with previous years.

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Re: Latest PIOMAS update (June)
« Reply #945 on: June 04, 2016, 01:39:22 PM »
The animation shows spurious ice in the Barents Sea around the 7.5. is that added to the monthly average? Its thickness is low and it only lasts for a few days but it would increase average artificially, or am I wrong?

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Re: Latest PIOMAS update (June)
« Reply #946 on: June 04, 2016, 01:44:12 PM »
Cool, Wipneus. Thanks!

Gridded daily and monthly thickness data is now available. The official volume data not yet. From the daily gridded thickness I estimate that volume on day 152 is 19200 [km3].

That would mean a drop of around 3000 km3, which is what I expected! If I could, I would kiss my own eyeballs.  ;)

Given the comparison distribution map, PIOMAS has a lot of thick ice in the ESS. I wonder what the high temps and clear skies that are pounding that area (and will continue to do so for another week), will mean for next month's update?
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Re: Latest PIOMAS update (June)
« Reply #947 on: June 04, 2016, 04:28:53 PM »
These delta maps again show to me that this past late winter's winds that blew the ice out of the Beaufort Sea seems to have pushed that ice into the East Siberian Sea (ESS) [edit: and Chukchi Sea]. Wrangel Island, it appears to me, blocked that monotonous onslaught, leaving a relatively low-ice 'shadow'.

I think a combination of (1) the generally 'warm' Arctic winter, (2) the open water heat release (due to the open water caused by the relentless wind) and (3) choppy & mixed (warmed) water caused by the wind caused the Beaufort Sea to mostly remain open water and not refreeze (or not much where it did refreeze).  (Chris Reynolds, on his blog a while ago, posted a graph that showed that two early months this year had way above normal air temperatures over the Beaufort Sea.  Although not records in themselves, having two in a row was.) [My thinking on this matter has evolved since I wrote a post somewhere.]
« Last Edit: June 06, 2016, 12:47:43 AM by Tor Bejnar »
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Re: Latest PIOMAS update (June)
« Reply #948 on: June 05, 2016, 01:09:51 AM »
Great stuff, thanks Wipneus!

One small question on your ice thickness colour scale compared to previous months for your plot "PIOMAS Modeled Ice Thickness May 2016".

The 0m, 1m, 3m and 4m  ticks now don't align with a colour boundary. The 2m boundary still does. Don't you need to expand the tick mark distance scale away from 2m so they do? E.g. white should start at 3.75m, shouldn't it?
« Last Edit: June 05, 2016, 01:15:25 AM by slow wing »

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Re: Latest PIOMAS update (June)
« Reply #949 on: June 05, 2016, 01:37:09 AM »
A more substantive question from that plot...

Would it be fair to say we are seeing the ice being pushed around more than in previous Mays?

In particular:
   - the Beaufort bare patch has come from ice movement more than in situ melting
   - thicker ice is piled up on the Siberian coast
   - a band of thicker ice is seen to develop running from the Canadian side to the Russian side, due to the Beaufort gyre
   - a band of thinner ice opens up in the mid-section of the >3.75 'white' ice (Q. do we have visual verification of this?).

Some of this might have been a persistent weather system powering the Beaufort gyre. But some of it might be due to the ice being thinner in recent years. There is also the general 'rottenness' of the Arctic ice, as has been reported. At least one poster (sorry, forget who) has also been talking about expectation of reduced structural strength of the ice due to the Winter having been less cold than in previous years.

The ice piled up on the Siberian coast will be assaulted by warm winds from the land.
Are there more internal fractures this year as well? The exposed water will warm up and melt any ice dragged over it.

If the ice is thinner and weaker and so is being pushed around more this year, and in recent years, then that is ominous for this and future melt seasons.