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crandles

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PIOMAS Maximum
« on: April 07, 2013, 01:26:47 PM »


Larger version: http://farm9.staticflickr.com/8120/8626552241_5dc1304294_b.jpg

Trend has moved day of maximum from 113 to 105. So early/mid May would seem rather late. About day 100 (10 April) would seem an appropriate day if you expect it to be earlier than the trend. This would probably mean little increase from 21.612 on day 90.

Gain day 60 to 70 = 0.761
Gain day 70 to 80 = 0.451
Gain day 80 to 90 = 0.455

2012 (late max) had 0.858 0.497 0.498
2011 (early max) had 0.602 0.554 0.431

Probably not sensible to read too much into this but 0.455 of last 10 days is nearer the 0.431 of 2011 which had an early max.

Please feel free to add your guesses of day and amount.
I am going for: day 103 21.78

Jim Pettit

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Re: PIOMAS Maximum
« Reply #1 on: April 07, 2013, 05:16:04 PM »
Nice graph, and it definitely shows how max volume day has shifted earlier over the length of the record. Here's one of my own:



I created this standard distribution chart of PIOMAS max days, and the shift of which you speak is very evident. The dashed blue lines represent the maximum volume day for the years 1979-1984 inclusive. (There are only five lines visible, as max was on Day 112 in both 1980 and 1982). Note that five of the six lines are on the high side of the mean, with one of those far beyond one standard deviation from that mean. The dashed red lines represent the maximum volume day for the years 2007-2012 (and again there are only five lines visible, as 2009 and 2011 shared a max day of 103. Note now that five of those six years have seen their maximum occur on the low side of the mean, with four of those more than one standard deviation below the mean. (The lone outlier is last year's Day 114 occurrence.)

My own guess: this year's volume maximum of 21.805 will occur next week, on Day 106.

Dave C

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Re: PIOMAS Maximum
« Reply #2 on: April 08, 2013, 06:32:19 AM »
Day 106, 21.96.

Tor Bejnar

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Re: PIOMAS Maximum
« Reply #3 on: April 09, 2013, 02:05:30 PM »
guess:  PIOMAS max on day 109  with volume of 21.99 x 10^3 km^3
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Vergent

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Re: PIOMAS Maximum
« Reply #4 on: April 09, 2013, 06:16:34 PM »
21.872 day 99(today)

However due to PIOMAS's propensity to overestimate thin ice thickness(and its tendency to underestimate the thick stuff),

and the fact that there is about 1,000,000 km2 less of the thick stuff

and the fact that there is about 1,000,000 km2 more of the thin stuff,

and the huge area of frozen leads that it does not take into account,

and that they made it "conservative" with v2.0,
 .
. .  the reality will be less than 20.0. I'll wait for icebridge/cryosat2.

 V

ChrisReynolds

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Re: PIOMAS Maximum
« Reply #5 on: April 10, 2013, 10:37:39 PM »
Whooo Hooo!

Dr Schweiger has just emailed me.

PIOMAS gridded thickness data now out to March 2013.
ftp://psc.apl.washington.edu/zhang/IDAO/retrospection/

I've replied asking whether they intend to update periodically.

 ;D
« Last Edit: April 10, 2013, 10:43:26 PM by ChrisReynolds »

Neven

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Re: PIOMAS Maximum
« Reply #6 on: April 10, 2013, 10:57:01 PM »
Chris, does this mean that you can see where the thickening occurred?
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ChrisReynolds

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Re: PIOMAS Maximum
« Reply #7 on: April 10, 2013, 11:42:24 PM »
No.

It means YOU can see where the thickening occurred.
http://dosbat.blogspot.co.uk/2013/04/piomas-2013-so-far.html
 ;)

I'll update the thickness breakdowns, just run them off, but it's time for bed.

PS - Neven and anyone, it's not my data, the images on that page are free for anyone to use provided it's made clear they not made by the PIOMAS team.

Neven

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Re: PIOMAS Maximum
« Reply #8 on: April 10, 2013, 11:56:49 PM »
No.

It means YOU can see where the thickening occurred.
http://dosbat.blogspot.co.uk/2013/04/piomas-2013-so-far.html
 ;)

Hold on, let me get my glasses.  :P

Quote
I'll update the thickness breakdowns, just run them off, but it's time for bed.

PS - Neven and anyone, it's not my data, the images on that page are free for anyone to use provided it's made clear they not made by the PIOMAS team.

Yes, yes, we'll tell everyone that PIOMAS is predicting that the world is about to end. No worries.  8)
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TerryM

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Re: PIOMAS Maximum
« Reply #9 on: April 11, 2013, 03:53:40 AM »
That's a huge difference from last March!


Assuming the Laptev ice heads out towards Fram, there won't be much thick ice to work with.


Terry

ChrisReynolds

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Re: PIOMAS Maximum
« Reply #10 on: April 11, 2013, 09:16:16 AM »
NOSEDIVE!  :o



Calculated from March PIOMAS gridded data. Region - all ice pack, Month - March. Volume contribution for above and below 2m thick. 2m having been chosen because above this thickness growth is mainly compression and ridging, below 2m growth is mainly thermodynamic, so the 2m split represents a good proxy for young ice (<2m) and old ice (>2m). This also shows how the volume loss has previously been from thicker older ice.

Conclusion, despite this year and the previous two having similar net volumes, the decline of the pack is continuing.

Source spreadsheet available here:
https://docs.google.com/file/d/0B3pB-kdzoLU3MkNsZFpxZTlmUEk/edit?usp=sharing

Wipneus

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Re: PIOMAS Maximum
« Reply #11 on: April 11, 2013, 09:25:22 AM »
Attached plot of the ice thickness differences between March 2013 and March 2012.


ChrisReynolds

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Re: PIOMAS Maximum
« Reply #12 on: April 11, 2013, 09:40:57 AM »
Thanks Wipneus,

So there's been a lot of volume gain in Barents/Kara and the Atlantic sector, The lack of the MYI tongue from Beaufort through Chukchi is evident.

Actually I've just filled out my above comment and posted on my blog. But we may see a very early start to the melt in Beaufort, probably th earliest melt so far.

slow wing

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Re: PIOMAS Maximum
« Reply #13 on: April 11, 2013, 01:22:18 PM »
Attached plot of the ice thickness differences between March 2013 and March 2012.
Thanks Wipneus, that is very interesting indeed.

Just to make the general comment that the quality of data presentation from you and some of the others on the forum and blog is incredible! It really helps to get a handle on what is happening and so is much appreciated.




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Re: PIOMAS Maximum
« Reply #14 on: April 11, 2013, 01:47:17 PM »
Wipneus, thanks for fast visualization. What do you think, is the strong east/west gradient of the three Russian islands a consequence of changed drift pattern? (ice piling up on the eastern coast)

ChrisReynolds

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Re: PIOMAS Maximum
« Reply #15 on: April 11, 2013, 01:52:12 PM »
Yes that piling up wasn't there in February's average thickness but is in March's. It's a consequence of the overall clockwise motion of the pack in late February to mid March, the event that caused the Beaufort fracturing.

Wipneus

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Re: PIOMAS Maximum
« Reply #16 on: April 11, 2013, 02:53:20 PM »
What do you think, is the strong east/west gradient of the three Russian islands a consequence of changed drift pattern? (ice piling up on the eastern coast)

Yup, either that or relative absence of these effects in 2012.

Ice Cool Kim

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Re: PIOMAS Maximum
« Reply #17 on: April 11, 2013, 03:05:47 PM »
The question of drift is interesting. How does the other end drift (min) ?

This could be an interesting comparison to my work on melting/freezing periods from ice area.

Is possible to pull ice area out of PIOMAS as well?

Yuha

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Re: PIOMAS Maximum
« Reply #18 on: April 11, 2013, 04:33:28 PM »
Wipneus, thanks for another highly informative plot.

Could I suggest another one: differences in January-March ice gain between 2012 and 2013.

In January there was 1000 km3 less ice this year than last but in March the ice volumes were almost equal. It would interesting to know how that extra ice is distributed.

Wipneus

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Re: PIOMAS Maximum
« Reply #19 on: April 11, 2013, 07:01:32 PM »
Quote
Could I suggest another one: differences in January-March ice gain between 2012 and 2013

Well, I've named it "PIOMAS Modeled Ice Jan-Mar Thickness Growth Difference 2013-2012"

Attached, for you to analyse.

Jim Williams

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Re: PIOMAS Maximum
« Reply #20 on: April 11, 2013, 07:38:24 PM »
Blowing out into the Atlantic?

crandles

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Re: PIOMAS Maximum
« Reply #21 on: April 11, 2013, 08:01:48 PM »
Blowing out into the Atlantic?

Possibly, also strong rotation with cracking could well have mushed more ice into Barents. However, it seems more like 2012 was warmer in Kara and Barents than 2013 such that there was much less ice formed in these regions in 2012.

Whatever the cause it suggests a slow start to melt season on Atlantic side this year. OTOH Beaufort ....

ChrisReynolds

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Re: PIOMAS Maximum
« Reply #22 on: April 11, 2013, 08:24:09 PM »
Ice Cool Kim,

PIOMAS gridded data also include ice movement, although that's not included in this early release. See the icevel files, (single precision binary).
ftp://psc.apl.washington.edu/zhang/IDAO/retrospection

Little point in getting area from PIOMAS because PIOMAS assimilate sea ice concentration you may as well use a real satellite product. EDIT - I have done it for the open water formation efficiency work I did a while back - but it was all needed in terms of PIOMAS. Combining PIOMAS and extent/area has some weird effects.
« Last Edit: April 11, 2013, 08:32:40 PM by ChrisReynolds »

ChrisReynolds

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Re: PIOMAS Maximum
« Reply #23 on: April 11, 2013, 08:48:03 PM »
Blowing out into the Atlantic?

Possibly, also strong rotation with cracking could well have mushed more ice into Barents. However, it seems more like 2012 was warmer in Kara and Barents than 2013 such that there was much less ice formed in these regions in 2012.

Whatever the cause it suggests a slow start to melt season on Atlantic side this year. OTOH Beaufort ....



Temperature plot for 2013 minus 2012.

But ASCAT still showed significant movement into the Atlantic sector in Feb/Mar, and the March thickening onto the islands out to Svalbard supports ice transport towards the Atlantic. 2012 is notable thin in Barents for March of years post 2007. I think we'll have a typical melt in the Atlantic region, but from the first week of June Beaufort and Siberian will see aggressive melt, unlike past years there's no MYI buffer.

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Re: PIOMAS Maximum
« Reply #24 on: April 11, 2013, 09:40:35 PM »
> PIOMAS Modeled Ice Jan-Mar Thickness Growth Difference 2013-2012

If only PIOMAS would tell what's drift and what's freeze...

ChrisReynolds

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Re: PIOMAS Maximum
« Reply #25 on: April 11, 2013, 10:21:04 PM »
It will... in 2014.   ;)

Ice Cool Kim

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Re: PIOMAS Maximum
« Reply #26 on: April 12, 2013, 12:09:43 AM »
Quote
Little point in getting area from PIOMAS because PIOMAS assimilate sea ice concentration you may as well use a real satellite product. EDIT - I have done it for the open water formation efficiency work I did a while back - but it was all needed in terms of PIOMAS. Combining PIOMAS and extent/area has some weird effects.

Thanks Chris. In fact I realised that my comment about drift was ambiguous. I was not referring to ice drift but to the top post about date of max. ie drift in dates not in the ice itself.

While I realise that PIOMAS takes real data input, my thinking was this :

check how well PIOMAS finalises area with relation to min/max dates: run the same  processing I did on area/extent on PIOMAS output and compare.

If results are close, it would suggest we are comparing apples to apples. Then proceed to look at PIOMAS volume min/max dates by similar methods.

See whether PIOMAS derived melting/freezing seasons tells us anything new or different from ice area/extent estimations of melting season.

My guess is that it will show notable differences, so when we see them we can start assessing what they may tell us about the processes driving ice.

Your comment about funny things happening may mean the two are not compatible. so that will rather kill the idea but it would be worth checking to see.


Yuha

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Re: PIOMAS Maximum
« Reply #27 on: April 12, 2013, 12:14:39 AM »
Thanks, Wipneus.

And thanks, Chris, for the temperature plot.

There is a strong correlation between temperature and ice growth, not surprisingly.
But why did Baffin Bay have a slight gain of ice despite much higher temperatures?
Lower salinity caused by the record Greenland melt? Does PIOMAS model that?

Neven

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Re: PIOMAS Maximum
« Reply #28 on: April 12, 2013, 12:33:56 AM »
Yes, thanks, Chris and Wipneus! I've used your stuff for an extra PIOMAS update over on the ASIB.

One thing though, besides those thicknesses of almost 4 metres near the Siberian coast (I guess that's possible): How can the Baffin Bay ice be thicker than in 2012 - albeit slightly - according to the PIOMAS Modeled Ice Jan-Mar Thickness Growth Difference 2013-2012 map that Wipneus made, when temps have been so much higher than in 2012 according to Chris' Temperature plot for 2013 minus 2012?
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ChrisReynolds

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Re: PIOMAS Maximum
« Reply #29 on: April 12, 2013, 08:02:44 AM »
Neven,

typo I think, 2012 was warmer than 2013 by up to 8degC.

Kim,

Funny things, refers to the sort of volume you get when using CT Area and PIOMAS thickness - wildly wrong.

If you're looking at dates as you have been then using the daily PIOMAS series is what you need. Gridded PIOMAS is only released at monthly average resolution.

Ice Cool Kim

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Re: PIOMAS Maximum
« Reply #30 on: April 12, 2013, 08:59:33 AM »
Quote
Funny things, refers to the sort of volume you get when using CT Area and PIOMAS thickness - wildly wrong.

OK , well that pretty much answers the question about compatibility.

This raises a question as to what area would be applicable. If you take PIOMAS volume and divide by PIOMAS thickness you should get an area that can be compared to real world data as a kind of sanity check on the model.

In fact I would expect that would be the first step in model verification.

Models are of little use if they only exist in their own little universe.

Is there anything like this in the literature that you are aware of?

Thanks.

Wipneus

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Re: PIOMAS Maximum
« Reply #31 on: April 12, 2013, 11:15:59 AM »
On request, I linked the thickness map of march 2013 on the ASI blog:



Neven:

Max thickness is 4.4 m, stuck on the Siberian coast in that little reddish patch behind Wrangel island.

Don't know about Baffin, as air temperature is only one factor the others factors are probably not so favorable.  Since we have only the thickness parameter pre-released, I cannot say much about those.


Dave C

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Re: PIOMAS Maximum
« Reply #32 on: April 12, 2013, 02:18:10 PM »


 How can the Baffin Bay ice be thicker than in 2012 - albeit slightly - according to the PIOMAS Modeled Ice Jan-Mar Thickness Growth Difference 2013-2012 map that Wipneus made, when temps have been so much higher than in 2012 according to Chris' Temperature plot for 2013 minus 2012?

There was a strong clockwise motion in the arctic this winter. It's likely that ice was pushed up into Baffin Bay.  The Davis strait has less ice than last year, which is what you would expect if this is what happened.

http://igloo.atmos.uiuc.edu/cgi-bin/test/print.sh?fm=04&fd=09&fy=2012&sm=04&sd=09&sy=2013

Ice Cool Kim

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Re: PIOMAS Maximum
« Reply #33 on: April 12, 2013, 05:03:43 PM »
Chris:
Quote
If you're looking at dates as you have been then using the daily PIOMAS series is what you need. Gridded PIOMAS is only released at monthly average resolution.

Where do the dates for the headline plot come from ?

Is there a regional time series at daily resolution or is the max date just another extract which is published as a given result?


crandles

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Re: PIOMAS Maximum
« Reply #34 on: April 12, 2013, 05:52:03 PM »
Daily volume numbers for Northern Hemisphere have been published for longer than I have been aware of the monthly gridded information. Daily dates come from the daily volume numbers.

Ice Cool Kim

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Re: PIOMAS Maximum
« Reply #35 on: April 12, 2013, 07:02:18 PM »
Thanks crandle. Would you like to add a link to the data source for you graph?


Neven

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Re: PIOMAS Maximum
« Reply #36 on: April 12, 2013, 07:05:05 PM »
Thanks crandle. Would you like to add a link to the data source for you graph?

If you scroll down on the PSC PIOMAS website, you can click a link to get the data.
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ChrisReynolds

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Re: PIOMAS Maximum
« Reply #37 on: April 12, 2013, 07:37:20 PM »
Kim,

I've already directed you to Zhang 2003 on a different matter:
http://psc.apl.washington.edu/zhang/Pubs/POIM.pdf

Firgure 9 shows the sort of fit attained without assimilation of sea ice concentration.

Schweiger's study on PIOMAS uncertainty is the most comprehensive assessment of PIOMAS performance.
http://psc.apl.washington.edu/wordpress/wp-content/uploads/schweiger/pubs/IceVolume-2011-06-02-accepted-with-figures.pdf

PIOMAS gridded data is here:
http://psc.apl.washington.edu/zhang/IDAO/data_piomas.html

Volume broken down into different thickness bands is available here:
http://dosbat.blogspot.co.uk/2013/02/piomas-volume-thickness-breakdowns.html

Ice Cool Kim

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Re: PIOMAS Maximum
« Reply #38 on: April 12, 2013, 09:54:03 PM »
Thanks Chris , Neven.

Here is a similar melting/freezing plot as I did for ice area.

It seems to follow AO a little less closely on the 1-2 year scale but probably rather better on the decadal scale which is interesting.

Also worth noting is that it shows similar shortening of melting period since 2007 as I found in ice area.

short black line is the offset applied to the neutral level of AO .

oops, just noticed the graph title says Antarctic, this is of course Arctic Ice.

« Last Edit: April 13, 2013, 05:39:38 PM by Ice Cool Kim »

Ice Cool Kim

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Re: PIOMAS Maximum
« Reply #39 on: April 13, 2013, 09:59:13 AM »
crandle's original plot show the max getting earlier. That is a noteworthy consequence of more open water, thinner coverage etc. but it's only half the story. There is a similar but non identical drift of the min date as well.

The uncertainly found in Schweiger's paper is pretty huge in percentage terms, though it does show that the model is getting close to something physically meaningful.

It's interesting that there is an underlying curvature in the duration of seasons derived from the volume model that did not stand out in my area/extent plots.

Probably yet another caution against the current obsession in climatology of fitting straight lines to everything, in a system that is anything but linear in behaviour.



crandles

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Re: PIOMAS Maximum
« Reply #40 on: May 04, 2013, 03:34:05 PM »
crandles day 103 21.78
Jim Pettit 21.805 Day 106
DaveC Day 106, 21.96
Tor Bejnar 109 21.99
Vergent 21.872 day 99


Actual 2013 max day 107 21.823

Jim Pettit wins on the volume and joint on the day with Dave C.
Congratulations.

Neven

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Re: PIOMAS Maximum
« Reply #41 on: May 04, 2013, 05:19:06 PM »
Well done, Jim P. That's really close!
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Jim Pettit

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Re: PIOMAS Maximum
« Reply #42 on: May 06, 2013, 10:56:52 PM »
Yay, me!  :) But I "cheated", really; just going along with my volume projection graph:



I think it's fascinating, though not necessarily a shock, how much steeper ice volume is declining in recent years (yellow and green) than it did in the past (blue and magenta)*. Such acceleration is fascinating--and obviously very alarming.

* - I can see that the recent years--in yellow--aren't showing up well. I will remedy that shortly...