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Author Topic: Latest PIOMAS update (May 2019)  (Read 938210 times)

ChrisReynolds

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Re: Latest PIOMAS update (January)
« Reply #150 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.

Neven

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Re: Latest PIOMAS update (January)
« Reply #151 on: February 06, 2014, 07:21:34 PM »
Quote
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
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ChrisReynolds

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Re: Latest PIOMAS update (January)
« Reply #152 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.

Quote
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.

jdallen

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Re: Latest PIOMAS update (January)
« Reply #153 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.
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ktonine

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Re: Latest PIOMAS update (January)
« Reply #154 on: February 06, 2014, 10:15:42 PM »
Chris:
Quote
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 :)


ChrisReynolds

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Re: Latest PIOMAS update (January)
« Reply #155 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.

ChrisReynolds

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Re: Latest PIOMAS update (January)
« Reply #156 on: February 06, 2014, 10:28:12 PM »
Chris:
Quote
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)

jdallen

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Re: Latest PIOMAS update (January)
« Reply #157 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.
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jdallen

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Re: Latest PIOMAS update (January)
« Reply #158 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.
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Wipneus

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Re: Latest PIOMAS update (January)
« Reply #159 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.

ChrisReynolds

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Re: Latest PIOMAS update (January)
« Reply #160 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.

Wipneus

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Re: Latest PIOMAS update (January)
« Reply #161 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.

ChrisReynolds

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Re: Latest PIOMAS update (January)
« Reply #162 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.

ChrisReynolds

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Re: Latest PIOMAS update (January)
« Reply #163 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.
« Last Edit: February 07, 2014, 07:29:08 PM by ChrisReynolds »

ChrisReynolds

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Re: Latest PIOMAS update (January)
« Reply #164 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.

Neven

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Re: Latest PIOMAS update (January)
« Reply #165 on: February 07, 2014, 09:57:22 PM »
Thanks for looking into this, ChrisR and Wipneus.
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jdallen

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Re: Latest PIOMAS update (January)
« Reply #166 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.
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Wipneus

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Re: Latest PIOMAS update (January)
« Reply #167 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 putting the 2013 "recovery" in perspective.

About the bug discovered and the new version 2.1:

Quote
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:



It will take some time to update my own graphics.

jdallen

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Re: Latest PIOMAS update (January)
« Reply #168 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...)
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ChrisReynolds

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Re: Latest PIOMAS update (February)
« Reply #169 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.  ;)

Wipneus

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Re: Latest PIOMAS update (February)
« Reply #170 on: February 08, 2014, 11:37:15 AM »
I have updated for version 2.1, graphs are in the top post.

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).

ChrisReynolds

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Re: Latest PIOMAS update (February)
« Reply #171 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%.

 :)


crandles

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Re: Latest PIOMAS update (February)
« Reply #172 on: February 08, 2014, 12:26:05 PM »
V2.1 numbers:

Code: [Select]
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

crandles

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Re: Latest PIOMAS update (February)
« Reply #173 on: February 08, 2014, 01:10:23 PM »
Monthly averages:

Code: [Select]
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

ChrisReynolds

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Re: Latest PIOMAS update (February)
« Reply #174 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

Jim Pettit

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crandles

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Re: Latest PIOMAS update (February)
« Reply #176 on: February 08, 2014, 06:17:18 PM »

ChrisReynolds

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Re: Latest PIOMAS update (February)
« Reply #177 on: February 08, 2014, 08:13:16 PM »

jdallen

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Re: Latest PIOMAS update (February)
« Reply #178 on: February 09, 2014, 07:50:10 AM »

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.
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crandles

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Re: Latest PIOMAS update (February)
« Reply #179 on: February 09, 2014, 11:28:07 AM »
Then perhaps this is also worth posting:



which is recreating a couple of Chris Reynolds graphs. Have you looked at dosbat
http://dosbat.blogspot.co.uk/2014/02/piomas-v21.html

crandles

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Re: Latest PIOMAS update (February)
« Reply #180 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?

jdallen

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Re: Latest PIOMAS update (February)
« Reply #181 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.
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ktonine

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Re: Latest PIOMAS update (February)
« Reply #182 on: February 09, 2014, 03:02:22 PM »
crandles:
Quote
...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.

Shared Humanity

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Re: Latest PIOMAS update (February)
« Reply #183 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.
« Last Edit: February 09, 2014, 03:49:27 PM by Shared Humanity »

crandles

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Re: Latest PIOMAS update (February)
« Reply #184 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.

ChrisReynolds

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Re: Latest PIOMAS update (February)
« Reply #185 on: February 09, 2014, 10:14:27 PM »
crandles:
Quote
...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.

Wipneus

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Re: Latest PIOMAS update (February)
« Reply #186 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:



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.


ChrisReynolds

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Re: Latest PIOMAS update (February)
« Reply #187 on: February 10, 2014, 06:56:32 PM »
crandles:
Quote
...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.

Wipneus

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Re: Latest PIOMAS update (March)
« Reply #188 on: March 07, 2014, 06:45:28 PM »
Updated, graphs are in the top post.

crandles

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Re: Latest PIOMAS update (March)
« Reply #189 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.

Wipneus

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Re: Latest PIOMAS update (March)
« Reply #190 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]
« Last Edit: March 14, 2014, 05:43:36 PM by Wipneus »

Wipneus

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Re: Latest PIOMAS update (March)
« Reply #191 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.

Neven

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Re: Latest PIOMAS update (March)
« Reply #192 on: March 14, 2014, 09:24:42 AM »
Very nice and interesting, as always. Thanks, WN.
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Steven

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Re: Latest PIOMAS update (March)
« Reply #193 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.

Wipneus

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Re: Latest PIOMAS update (March)
« Reply #194 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.

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Re: Latest PIOMAS update (March)
« Reply #195 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.


Nightvid Cole

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Re: Latest PIOMAS update (March)
« Reply #196 on: March 14, 2014, 11:51:56 PM »
Thanks for the sneak peak, Chris! :)

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Re: Latest PIOMAS update (March)
« Reply #197 on: March 15, 2014, 12:34:11 AM »
Thanks for these plots, Wipneus and Chris. Very interesting and much appreciated!   :D

ChrisReynolds

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Re: Latest PIOMAS update (March)
« Reply #198 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.

Wipneus

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Re: Latest PIOMAS update (March)
« Reply #199 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.