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Author Topic: Latest PIOMAS update (May 2019)  (Read 938238 times)

viddaloo

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Re: Latest PIOMAS update (January)
« Reply #500 on: February 07, 2015, 02:49:39 PM »
January has now increased its compensating support for the Arctic sea ice (up from 10%) and now shares the 'least supportive' position with December:



With half the decade gone, only 4 months contribute to the collapse, while 8 months do their best to resist and compensate:

January packs 10% more volume in the 2010s than in the late 1900s.
February packs 14% more volume in the 2010s than in the late 1900s.
March packs 18% more volume in the 2010s than in the late 1900s.
April has 75% lower net refreeze volume in the 2010s than in the late 1900s.
May melts 92% more volume in the 2010s than in the late 1900s.
June melts 37% more volume in the 2010s than in the late 1900s.
July melts 14% less volume in the 2010s than in the late 1900s.
August melts 20% less volume in the 2010s than in the late 1900s.
September has 36% lower net refreeze volume in the 2010s than in the late 1900s.
October packs 17% more volume in the 2010s than in the late 1900s.
November packs 25% more volume in the 2010s than in the late 1900s.
December packs 12% more volume in the 2010s than in the late 1900s.
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iceman

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Re: Latest PIOMAS update (February)
« Reply #501 on: February 07, 2015, 03:49:28 PM »

Not forgetting that CryoSat 2 reckoned the ice was thinner in Oct/Nov 2014 than in 2013.

Quote
Measurements made during October and November show that the volume of Arctic sea ice now stands at about 10 200 cubic km – a small drop compared to last year’s 10 900 cubic km
I wouldn't put too much faith in CryoSat 2 for now.  Judging from posts here a month ago, it seems that CryoSat 2 may have measured erroneously high in Oct/Nov 2013, which could yield an incorrect y/y decline in the latest readings.

Jim Hunt

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Re: Latest PIOMAS update (February)
« Reply #502 on: February 07, 2015, 05:07:45 PM »
I wouldn't put too much faith in CryoSat 2 for now

Which implies that you have a lot more faith in PIOMAS? I presume these are the comments you are referring to?

http://forum.arctic-sea-ice.net/index.php/topic,119.msg41670/topicseen.html#msg41670
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viddaloo

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Re: Latest PIOMAS update (February)
« Reply #503 on: February 07, 2015, 10:14:49 PM »
Updated collapse estimate: With the hottest year globally (sea and land surface) + the first warm month of 2015, average volume is now up 1968 km³ in 21 months. The last time we had an average volume jump of 1968 km³ or more in 21 months or less, was in 1995–97 (up 2181 km³), a La Niña event. So, to sum up; the monster volume regrowth of 2013–2015 is only matched by a 1995–97 La Nina regrowth of sea ice volume, even though 2014 was the warmest on record (in itself quite an achievement without an El Niño). When will we see a monster El Niño accompanied by a same–time monster La Niña–style ice volume regrowth? With "streamlined" América del Norte–style politicised "science" it may be closer than you think!


[chart faq]
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viddaloo

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Re: Latest PIOMAS update (February)
« Reply #504 on: February 09, 2015, 05:14:44 PM »
2014 *gained* 6th most ice during the year in the 1979–2014 PIOMAS time–series. Another way of putting this is that it 'melted' 31st most ice. By contrast, 2012 melted 8th most ice and was 9th warmest globally.

This is why I believe we may be heading for a new ice–age or a new 'Snowball Earth' scenario if the planet gets even hotter.
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Bob Wallace

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Re: Latest PIOMAS update (February)
« Reply #505 on: February 09, 2015, 05:44:47 PM »
And difference in growth from December to January,  red means more thickening/less thinning.

(total growth was about 3.4 [1000 km3], slightly less than the 3.6 [1000 km3] a year ago)

The red area east of Greenland and the blue areas to the north indicate a lot of thicker ice being ejected into the Atlantic?

Wipneus

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Re: Latest PIOMAS update (February)
« Reply #506 on: February 09, 2015, 06:08:15 PM »
The ice in the Greenland Sea will melt in the near future. How fast the ice is entering via the Fram Strait cannot be said from this data alone.

Peter Ellis

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Re: Latest PIOMAS update (February)
« Reply #507 on: February 09, 2015, 07:17:33 PM »
This is why I believe we may be heading for a new ice–age or a new 'Snowball Earth' scenario if the planet gets even hotter.

Wut?  Now I'm confused.  Are you simultaneously predicting a Snowball Earth and ice-free conditions year-round?  What's the snow made of, polystyrene?

Lord M Vader

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Re: Latest PIOMAS update (February)
« Reply #508 on: February 09, 2015, 07:22:24 PM »
Wipneus: don't forget the crap ice south east of Svalbard! It should also melt out rather quickly in the near future... Another area of interest is located southwest of Alaska with fragile ice but shouldn't be subject for melting in the close future as colder air seems to merge southward..

//LMV

Michael Hauber

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Re: Latest PIOMAS update (February)
« Reply #509 on: February 09, 2015, 10:20:37 PM »
The PIOMAS anomaly chart [/quote] is quite striking with anomalies now well above the long term trend, and above the range of the darker shading (1 standard deviation?).  This fits in comfortably with a long term linear trend.  However Tamino in the past had [url=https://tamino.wordpress.com/2013/03/12/arctic-sea-ice-loss-part-1/]shown a statistically significant acceleration and that the trend was not linear.  Some possibilities:
1.  Tamino's analysis is wrong.
3.  My gut feel assessment that a return to the upper boundaries of the typical range for a linear trend must be a significant departure from the non linear trend is wrong.
3.  A statistical fluke either caused the appearance of acceleration, or the return to above linear trend.
4.  A significant factor (i.e. something not covered by the relevant statistical test for noise) caused a temporary increase in melt and this factor has now changed.
5.  Something to do with Tamino's analysis being extent and this being volume. 
6.  Slow decline - the acceleration was real, but the trend is a gompertz curve that is now entering the deceleration phase.
Climate change:  Prepare for the worst, hope for the best, expect the middle.

Peter Ellis

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Re: Latest PIOMAS update (February)
« Reply #510 on: February 10, 2015, 01:32:43 AM »
(5) will be a huge factor.

Volume and area shouldn't be expected to follow the same pattern - at the most simplistic level, area scales with the square of linear dimensions and volume with the cube.  So, if a blob of ice melts evenly in all directions, the graph of area against volume will have y proportional to x^(2/3).  Or (3/2) depending which way round you draw your axes!

This in itself will intrinsically convert a linear decline in volume to a nonlinear, accelerating decline in area.  If you additionally assume that ice loses thickness proportionally faster than area (a fairly sensible assumption given how heat flow works in large flat sheets), then the nonlinearity becomes even more pronounced.

plinius

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Re: Latest PIOMAS update (February)
« Reply #511 on: February 10, 2015, 02:24:03 AM »
I'd add 6th: Your underlying hypothesis of homoskedasticity is wrong - we expect that due to increased positive feedbacks and reduced memory effect (less old ice there...) the variability (and probably also the autocorrelation) should go up. Hence, the statistical significance of these events is overestimated by your eye.

The PIOMAS anomaly chart
is quite striking with anomalies now well above the long term trend, and above the range of the darker shading (1 standard deviation?).  This fits in comfortably with a long term linear trend.  However Tamino in the past had shown a statistically significant acceleration and that the trend was not linear.  Some possibilities:
1.  Tamino's analysis is wrong.
3.  My gut feel assessment that a return to the upper boundaries of the typical range for a linear trend must be a significant departure from the non linear trend is wrong.
3.  A statistical fluke either caused the appearance of acceleration, or the return to above linear trend.
4.  A significant factor (i.e. something not covered by the relevant statistical test for noise) caused a temporary increase in melt and this factor has now changed.
5.  Something to do with Tamino's analysis being extent and this being volume. 
6.  Slow decline - the acceleration was real, but the trend is a gompertz curve that is now entering the deceleration phase.
[/quote]

Michael Hauber

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Re: Latest PIOMAS update (February)
« Reply #512 on: February 10, 2015, 03:27:29 AM »
I'd add 6th: Your underlying hypothesis of homoskedasticity is wrong - we expect that due to increased positive feedbacks and reduced memory effect (less old ice there...) the variability (and probably also the autocorrelation) should go up. Hence, the statistical significance of these events is overestimated by your eye.


A very quick analysis -  I measure variability as absolute difference from one year to next in September volume.  A linear trend shows variability has reduced over time - doesn't look to be significant, but it would be no surprise to me if less ice means less variability.  Consider also with a more uniform pack dominated by 1st year ice there will be less variability due to a regional hotspot being in an area of thin and vulnerable ice vs an area of thick and resilient ice. 

Climate change:  Prepare for the worst, hope for the best, expect the middle.

Peter Ellis

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Re: Latest PIOMAS update (February)
« Reply #513 on: February 10, 2015, 09:35:17 AM »
What on Earth does the September-to-September variability tell you about mid-February?

lanevn

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Re: Latest PIOMAS update (February)
« Reply #514 on: February 10, 2015, 10:39:10 AM »
This is why I believe we may be heading for a new ice–age or a new 'Snowball Earth' scenario if the planet gets even hotter.

Several days ago you predicted record low this year.

crandles

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Re: Latest PIOMAS update (February)
« Reply #515 on: February 10, 2015, 01:12:38 PM »

5.  Something to do with Tamino's analysis being extent and this being volume. 

Quote
(5) will be a huge factor.

The Tamino article linked included
Quote
Arctic sea ice volume shows a somewhat different pattern that that of extent and area:

There are still plenty of fluctuations but they’re not as large relative to the trend as with extent or area. This may be partly because the volume data involve the output of a computer model for ice thickness. There is still strong acceleration of sea ice volume loss, and no sign of deceleration.

The article is dated March 2013 so we are less than two year past this date. While I think there is now a sign of deceleration, is less than two years data likely to be statistically significant? So I am not ruling out 2 and 3.

4. Also seems entirely possible especially as an explanation has already been discussed. We had a rapid fall in Multi year ice when MYI ceased surviving a passage around Beaufort Gyre. MYI had fallen as low as it is going to go as a result of this so the rate of decline in volume slows down. See also slow transition thread.

Above could also be considered to be causing a gompertz shape curve ie it could be considered to be no 6.

So I am tending to think a combination of a couple of things that can be described as '2 & 3' and  '4 & 6'.

Michael Hauber

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Re: Latest PIOMAS update (February)
« Reply #516 on: February 10, 2015, 09:58:04 PM »
What on Earth does the September-to-September variability tell you about mid-February?

The same analysis repeated for February gives roughly the same result.
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epiphyte

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Re: Latest PIOMAS update (February)
« Reply #517 on: February 11, 2015, 08:14:22 AM »
(5) will be a huge factor.

Volume and area shouldn't be expected to follow the same pattern - at the most simplistic level, area scales with the square of linear dimensions and volume with the cube.  So, if a blob of ice melts evenly in all directions, the graph of area against volume will have y proportional to x^(2/3).  Or (3/2) depending which way round you draw your axes!

This in itself will intrinsically convert a linear decline in volume to a nonlinear, accelerating decline in area.  If you additionally assume that ice loses thickness proportionally faster than area (a fairly sensible assumption given how heat flow works in large flat sheets), then the nonlinearity becomes even more pronounced.

Sure the decline in area is nonlinear - but it all happens at the end.  If a disc of ice 1000km in diameter and 1m thick melts evenly in all directions, won't it still have an area of PI*499.495**2 ~= 783812km2 when it is uniformly 1mm thick?

Gray-Wolf

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Re: Latest PIOMAS update (February)
« Reply #518 on: February 11, 2015, 09:17:08 AM »
I get the idea that Vid was being a tad sarcastic about 'snowball earth'? The topsy turvy world of 'how much ice' and how much ice gain versus ice losses can appear a tad counter intuitive and deniers will often mess with things like 'ice gain' ,come re-freeze, after major loss years.

Some times 'more is less' and it can be a bit like that looking at every single bob and weave that some ice stats take? Maybe the 'bigger picture' is a safer view esp. over rebound years???
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crandles

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Re: Latest PIOMAS update (February)
« Reply #519 on: February 11, 2015, 12:37:26 PM »
(5) will be a huge factor.

Volume and area shouldn't be expected to follow the same pattern - at the most simplistic level, area scales with the square of linear dimensions and volume with the cube.  So, if a blob of ice melts evenly in all directions, the graph of area against volume will have y proportional to x^(2/3).  Or (3/2) depending which way round you draw your axes!

This in itself will intrinsically convert a linear decline in volume to a nonlinear, accelerating decline in area.  If you additionally assume that ice loses thickness proportionally faster than area (a fairly sensible assumption given how heat flow works in large flat sheets), then the nonlinearity becomes even more pronounced.

Sure the decline in area is nonlinear - but it all happens at the end.  If a disc of ice 1000km in diameter and 1m thick melts evenly in all directions, won't it still have an area of PI*499.495**2 ~= 783812km2 when it is uniformly 1mm thick?

A more accurate view of the ice is a semicircle in area which is thickest at the centre (against Canada) and gets thinner towards the edges. This will maintain its basic shape as it melts. That is rather theoretical and in practice it may be much more complex, however, when looking at data the same ratio of area to thickness does seem to be maintained.

viddaloo

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Re: Latest PIOMAS update (February)
« Reply #520 on: February 11, 2015, 02:52:15 PM »
I get the idea that Vid was being a tad sarcastic about 'snowball earth'? The topsy turvy world of 'how much ice' and how much ice gain versus ice losses can appear a tad counter intuitive and deniers will often mess with things like 'ice gain' ,come re-freeze, after major loss years.

Some times 'more is less' and it can be a bit like that looking at every single bob and weave that some ice stats take? Maybe the 'bigger picture' is a safer view esp. over rebound years???

If I was a tabloid empire I would certainly run with the headline 'New Ice–Age in June' on the front–page, and nifty drawings of 'Snowball–Earth' in the magazine supplement. If only one record–warm year can give this much more ice Jan 1 to Jan 1, imagine what a string of 10 or 100 steadily warmer years can do?
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jbatteen

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Re: Latest PIOMAS update (February)
« Reply #521 on: February 11, 2015, 06:58:06 PM »
I still can't tell if you're serious or sarcastic.

viddaloo

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Re: Latest PIOMAS update (February)
« Reply #522 on: February 11, 2015, 07:30:07 PM »
Clarification: I don't think we'll be in a new ice–age by June.
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Re: Latest PIOMAS update (February)
« Reply #523 on: February 13, 2015, 06:36:50 PM »
any cryosat update for December or January data to compare with piomas?

They have been strikingly different the past two falls and the most recent press release the folks running cryosat claim it's 99% accurate.
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viddaloo

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Re: Latest PIOMAS update (February)
« Reply #524 on: February 13, 2015, 06:45:58 PM »
Welcome back, Friv!

I've just been reading up on the melt seasons prior to my joining the forum (ie 2013 and first part of 2014 melt), and looking forward to having you on the board for the 2015 melt!
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lanevn

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Re: Latest PIOMAS update (February)
« Reply #525 on: February 13, 2015, 11:26:42 PM »
They have been strikingly different the past two falls and the most recent press release the folks running cryosat claim it's 99% accurate.
Cryosat is for europeans with renewables and energy savings, piomas for americans with shale gas and etc  8)
« Last Edit: February 15, 2015, 01:09:38 PM by lanevn »

lanevn

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Re: Latest PIOMAS update (February)
« Reply #526 on: February 15, 2015, 01:18:57 PM »
piomas for europeans with shale gas and etc  8)
Sorry, I ment "americans" ofc.

Wipneus

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Re: Latest PIOMAS update (March)
« Reply #527 on: March 11, 2015, 06:44:57 AM »
The gridded monthly data was updated, from it I calculate the average volum for February to be 21.5 [1000 km3], about 600 1600  km3 above 2014.

We will have to wait for the daily data to see if the trend after Feb 15 did change. In the mean time I will post the monthly thickness maps.
« Last Edit: March 11, 2015, 07:32:24 AM by Wipneus »

Wipneus

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Re: Latest PIOMAS update (March)
« Reply #528 on: March 11, 2015, 06:47:59 AM »
Thickness maps for February 2014 and 2015 and their difference.

Wipneus

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Re: Latest PIOMAS update (March)
« Reply #529 on: March 11, 2015, 06:54:39 AM »
And difference in growth from January to February, red means more thickening/less thinning.

OSweetMrMath

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Re: Latest PIOMAS update (March)
« Reply #530 on: March 11, 2015, 07:22:54 AM »
The gridded monthly data was updated, from it I calculate the average volum for February to be 21.5 [1000 km3]], about 600  km3] above 2014.

We will have to wait for the daily data to see if the trend after Feb 15 did change. In the mean time I will post the monthly thickness maps.

Feb. 2014 was 19.851, which makes this year 1600 cubic km above last year, unless I'm misreading something.

viddaloo

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Re: Latest PIOMAS update (March)
« Reply #531 on: March 11, 2015, 07:31:02 AM »
LOL
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Wipneus

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Re: Latest PIOMAS update (March)
« Reply #532 on: March 11, 2015, 07:33:23 AM »
Feb. 2014 was 19.851, which makes this year 1600 cubic km above last year, unless I'm misreading something.

Thanks, you are absolutely right.

OSweetMrMath

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Re: Latest PIOMAS update (March)
« Reply #533 on: March 11, 2015, 07:55:50 AM »
I'll post more on this tomorrow (in my time zone) but since volume increases due to thickening even after extent and area drop, I will not be surprised if the volume doesn't show the same late February drop as the other measures. The year-over-year increase in volume has been around 1000-1500 cubic km for every month since last July, so the February volume is basically still in that range. It is still several hundred cubic km above my prediction, for what that's worth.

Nightvid Cole

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Re: Latest PIOMAS update (March)
« Reply #534 on: March 11, 2015, 06:13:42 PM »
Volume, as of March 8th according to the main PIOMAS anomaly trace graph, is virtually indistinguishable from the same time in 2010.

The distribution is different, however. Compared to 2010, much more of the volume is in the thick band of ice off Greenland and the CAA. The ice in the central Arctic Ocean, away from any of the land masses, is thinner than 2010. Based on the map the modal thickness is roughly 25cm thinner than at the same time in 2010.

This means it is more likely that we will see the September extent go really low this year, though it of course depends on the weather.

Wipneus

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Re: Latest PIOMAS update (March)
« Reply #535 on: March 11, 2015, 06:46:33 PM »
PIOMASA daily data is updated now, see the graphs in the top post.

viddaloo

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Re: Latest PIOMAS update (March)
« Reply #536 on: March 11, 2015, 07:25:20 PM »
Code: [Select]
2015  32  20.348
2015  33  20.452
2015  34  20.542
2015  35  20.629
2015  36  20.699
2015  37  20.754
2015  38  20.812
2015  39  20.890
2015  40  20.991
2015  41  21.094
2015  42  21.199
2015  43  21.312
2015  44  21.448
2015  45  21.571
2015  46  21.680
2015  47  21.768
2015  48  21.803
2015  49  21.838
2015  50  21.897
2015  51  21.973
2015  52  22.042
2015  53  22.132
2015  54  22.235
2015  55  22.303
2015  56  22.355
2015  57  22.389
2015  58  22.434
2015  59  22.472
2015  60  22.524
2015  61  22.580
2015  62  22.623
2015  63  22.682
2015  64  22.731
2015  65  22.779
2015  66  22.808
2015  67  22.813
[]

viddaloo

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Re: Latest PIOMAS update (March)
« Reply #537 on: April 02, 2015, 08:10:38 AM »
Guessing the 2015 yearly Piomas ice volume maximum happened in March. My fake–piomas algorithm seems to suggest as much:

Code: [Select]
2015 79  23.801
2015 80  23.943
2015 81  24.135
2015 82  24.261
2015 83  24.329
2015 84  24.423
2015 85  24.513
2015 86  24.473
2015 87  24.368
2015 88  24.309
2015 89  24.284
2015 90  24.267
2015 91  24.289

If so, this of course implies Piomas Minus 1000 would have a maximum volume of about 23,500 km³. Such a maximum would also be the earliest Piomas max by about a week.
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Wipneus

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Re: Latest PIOMAS update (April)
« Reply #538 on: April 04, 2015, 09:21:34 AM »
Updated, graphs are in the top post.

(gridded data updated also, I will post the graphs later)

Wipneus

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Re: Latest PIOMAS update (April)
« Reply #539 on: April 04, 2015, 09:29:09 AM »
Here are thickness maps for March 2014 and 2015 as well as their difference.


Wipneus

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Re: Latest PIOMAS update (April)
« Reply #540 on: April 04, 2015, 09:30:23 AM »
And difference in growth from February to March,  red means more thickening/less thinning.

crandles

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Re: Latest PIOMAS update (April)
« Reply #541 on: April 04, 2015, 12:31:31 PM »
2015  60  22.524
2015  61  22.580
2015  62  22.623
2015  63  22.682
2015  64  22.731
2015  65  22.779
2015  66  22.809
2015  67  22.814
2015  68  22.851
2015  69  22.872
2015  70  22.938
2015  71  22.990
2015  72  23.039
2015  73  23.090
2015  74  23.140
2015  75  23.160
2015  76  23.177
2015  77  23.216
2015  78  23.284
2015  79  23.365
2015  80  23.456
2015  81  23.536
2015  82  23.610
2015  83  23.683
2015  84  23.756
2015  85  23.826
2015  86  23.878
2015  87  23.924
2015  88  23.963
2015  89  23.998
2015  90  24.036

2014  90  22.639
2013  90  22.850
2012  90  22.889
2011  90  22.129
2010  90  24.053
2009  90  24.613
2008  90  24.698
2007  90  23.711
2006  90  24.860
2005  90  25.760

Of these years fairly steady downward movement with exception of 2007 being unusually low and this year being unusually high - only 6th lowest for date and close enough to 2010 to call it =6th.

So perhaps we should expect poor melt season?

Neven

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Re: Latest PIOMAS update (April)
« Reply #542 on: April 04, 2015, 12:37:36 PM »
Thanks for the heads up, Wip. I'll have a blog post up later today.
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jdallen

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Re: Latest PIOMAS update (April)
« Reply #543 on: April 04, 2015, 07:48:11 PM »

Of these years fairly steady downward movement with exception of 2007 being unusually low and this year being unusually high - only 6th lowest for date and close enough to 2010 to call it =6th.

So perhaps we should expect poor melt season?

Quite within the realm of possibility.  A poor melt season would keep the minimum within the general envelope of 2013 and 2014.  Considering a poor (Really Poor - Under 9.5 million KM2 of retreat - 2014 retreated 9.75...) melt season would still put us close to 5 million KM2, that's still not particularly good news.

All hinges on the weather. 

Edit - DavidR has some nice graphs showing annual losses.  The 2000-2014 one provides a pretty good preview.  The discussion on his new thread has the potential to be interesting as well.

http://forum.arctic-sea-ice.net/index.php/topic,1211.msg49401.html#msg49401
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Re: Latest PIOMAS update (April)
« Reply #544 on: April 04, 2015, 09:32:43 PM »

Of these years fairly steady downward movement with exception of 2007 being unusually low and this year being unusually high - only 6th lowest for date and close enough to 2010 to call it =6th.

So perhaps we should expect poor melt season?

Quite within the realm of possibility.  A poor melt season would keep the minimum within the general envelope of 2013 and 2014.  Considering a poor (Really Poor - Under 9.5 million KM2 of retreat - 2014 retreated 9.75...) melt season would still put us close to 5 million KM2, that's still not particularly good news.

All hinges on the weather. 

Edit - DavidR has some nice graphs showing annual losses.  The 2000-2014 one provides a pretty good preview.  The discussion on his new thread has the potential to be interesting as well.

http://forum.arctic-sea-ice.net/index.php/topic,1211.msg49401.html#msg49401

As I've said before, I don't think 2-dimensional measures at this time of year are remotely relevant to what ice will be there in September.

jdallen

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Re: Latest PIOMAS update (April)
« Reply #545 on: April 05, 2015, 08:42:48 AM »
As I've said before, I don't think 2-dimensional measures at this time of year are remotely relevant to what ice will be there in September.
How to frame this... the state of the ice *currently* is not specifically predictive of the state it will be in in September - I generally agree.

However - Median ice loss between max and min since 2000 is about 9.9 million KM2.
Average is about 10.1

So by extension, we statistically are looking at a minimum extent of just over 4 million KM2.

That puts us very close, if not slightly below 2007.

It will require a *very* favorable melt season to keep us above that.

If we have a "bad" melt season (e.g. similar to 2012), it's quite likely we could see a minimum well under 3 million KM2.  Statistics do not favor a good year.  Neither (and more importantly) does the weather.
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Nightvid Cole

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Re: Latest PIOMAS update (April)
« Reply #546 on: April 05, 2015, 07:00:37 PM »
As I've said before, I don't think 2-dimensional measures at this time of year are remotely relevant to what ice will be there in September.
How to frame this... the state of the ice *currently* is not specifically predictive of the state it will be in in September - I generally agree.

However - Median ice loss between max and min since 2000 is about 9.9 million KM2.
Average is about 10.1

So by extension, we statistically are looking at a minimum extent of just over 4 million KM2.

That puts us very close, if not slightly below 2007.

It will require a *very* favorable melt season to keep us above that.

If we have a "bad" melt season (e.g. similar to 2012), it's quite likely we could see a minimum well under 3 million KM2.  Statistics do not favor a good year.  Neither (and more importantly) does the weather.

You are contradicting yourself. Using differences between max and min to infer min IS THE SAME THING as inferring min from max!

For that matter, I could just as well argue that on average the minimum ice extent is 10 Trillion times the mean body surface area of patients admitted to St. Jude Hospital in March of that year, and since this year had a record low (due to fewer obese patients), it is unlikely the ice won't be close to a record low. Seems silly, right? But as long as max and min extent are uncorrelated to each other (at least after detrending), you're basically doing the same thing.

jdallen

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Re: Latest PIOMAS update (April)
« Reply #547 on: April 06, 2015, 06:41:35 AM »
As I've said before, I don't think 2-dimensional measures at this time of year are remotely relevant to what ice will be there in September.
How to frame this... the state of the ice *currently* is not specifically predictive of the state it will be in in September - I generally agree.
You are contradicting yourself. Using differences between max and min to infer min IS THE SAME THING as inferring min from max!

I disagree.  I'm not using the max to infer the eventual min.  I'm using the loss of ice extent to infer a possible range of minimum values, not a specific one.

By doing that I'm looking at two very broad variables.  First is the total uptake of heat, as identifiable by changes in ice coverage and ocean temperature.  The second is weather, as expressed in the same loss of ice.

So no, I can't infer a specific minimum.  I can infer from recent behavior a predictable loss of extent.  *That* has been reasonably consistent at just under 10 million KM2. 

However, the sample is fairly small, and has some pretty serious outliers (8.5 million and 12 million), so the chance exists for minima that reflect those losses.  That said, they *are* 2 sigma results.  most actually favor my base assumption of just under 10 million KM2.

We'll see how the season plays out.
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jdallen

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Re: Latest PIOMAS update (April)
« Reply #548 on: April 06, 2015, 07:45:46 AM »
To amplify my earlier post, here's SIA numbers (thank you Jim Pettit)

SIA   Maximum   Minimum   Loss
2014   13487337   3483168   10004169
2013   13799198   3444397   10354801
2012   13708510   2234010   11474500
2011   13144420   2904740   10239680
2010   13812038   2904740   10907298
2009   13812038   3424598   10387440
2008   13890715   3003556   10887159
2007   13317198   2919438   10397760
2006   13358222   4016919   9341303
2005   13460056   4091798   9368258
2004   13775685   4282973   9492712
2003   14339062   4141665   10197397
2002   14322480   4034710   10287770
2001   14526312   4533619   9992693
2000   13918529   4168766   9749763
1999   14295398   4204499   10090899
1998   14541186   4262403   10278783
1997   14332573   4899706   9432867
1996   13843270   5238185   8605085
1995   14274362   4410301   9864061
1994   14527855   4816096   9711759
1993   14755034   4472953   10282081
1992   14398718   5026778   9371940
1991   14222953   4460384   9762569
1990   14688305   4628935   10059370
1989   14183708   4815916   9367792
1988   15007110   5144891   9862219
1987   14682733   5288995   9393738
1986   14487026   5381843   9105183
1985   14594806   4992847   9601959
1984   14262281   4695892   9566389
1983   14773425   4386929   10386496
1982   14773425   5139060   9634365
1981   14308250   5507712   8800538
1980   14742998   5507712   9235286
1979   15074604   5306726   9767878

      Average   9868443
      Median   9815049
      StdDev   590653
      +2SD   11049750
      -2SD    8687137

Post 1999   Average   10205514
      Median   10239680
      StdDev   592651
      +2SD   11390816
      -2SD    9020211
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jdallen

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Re: Latest PIOMAS update (April)
« Reply #549 on: April 06, 2015, 08:25:44 AM »
So, from this consider the probable outcome for 2015.

If we have a sea ice loss which is "average", what would the minimum look like?

Applying the 1979-2014 average we get a max of 13.27 million KM2. (values in millions of KM2)


                      Using 1979-2014 stats      Using 2000-2014 stats
From Average   3.40                               3.06
From Median     3.45                               3.03
+2SD              2.22                                1.88
-2SD               4.58                                4.25

It's a big range, but its also pretty easy to see that given relatively normal melt, the ice coverage is quite likely to flirt with the lowest of years we've seen.

Even a "cool" melt year still keeps us generally within what we saw in 2013 and 2014.
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