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What will the CT 2013 Arctic SIA daily minimum be?

More than 3.5 million km2
1 (1.4%)
Between 3.25 and 3.5 million km2
0 (0%)
Between 3.0 and 3.25 million km2
4 (5.7%)
Between 2.75 and 3.0 million km2
3 (4.3%)
Between 2.5 and 2.75 million km2
3 (4.3%)
Between 2.25 and 2.5 million km2
9 (12.9%)
Between 2.0 and 2.25 million km2
14 (20%)
Between 1.75 and 2.0 million km2
15 (21.4%)
Between 1.5 and 1.75 million km2
8 (11.4%)
Between 1.25 and 1.5 million km2
3 (4.3%)
Between 1.0 and 1.25 million km2
2 (2.9%)
Between 0.75 and 1.0 million km2
6 (8.6%)
Between 0.5 and 0.75 million km2
0 (0%)
Between 0.25 and 0.5 million km2
1 (1.4%)
Between 0 and 0.25 million km2
1 (1.4%)

Total Members Voted: 67

Voting closed: June 20, 2013, 06:29:57 PM

Author Topic: Cryosphere Today 2013 Arctic SIA daily minimum: June poll  (Read 105885 times)

ChrisReynolds

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Re: Cryosphere Today 2013 Arctic SIA daily minimum: June poll
« Reply #100 on: June 21, 2013, 06:18:45 PM »
As has been pointed out so frequently on this forum, the volume of ice lost from this time of year until minimum remains nearly constant. It stands to reason that there will be something like 25% more volume at minimum this year than last.

But the volume loss profile remained the same until the volume loss of 2010, after which it changed, bringing about a more aggressive spring loss. Yes, it may seem reasonable to rely on past precedent to predict the volume/area minimum. But the pack is in the process of final transition to a seasonally sea ice free state, which will mean further reductions in multi-year ice. I don't think anyone really has a handle on the implications of this.

The loss of volume from now on may adhere to past precedent, but I don't think that can be guaranteed. If you think it can be guaranteed, your starting point should surely be to explain why it has remained invariant.

jdallen

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Re: Cryosphere Today 2013 Arctic SIA daily minimum: June poll
« Reply #101 on: June 21, 2013, 07:55:18 PM »
As has been pointed out so frequently on this forum, the volume of ice lost from this time of year until minimum remains nearly constant. It stands to reason that there will be something like 25% more volume at minimum this year than last.
... If you think it can be guaranteed, your starting point should surely be to explain why it has remained invariant.

Andrew - sounds like you are making an "all else being equal" argument, which isn't unreasonable. I, Chris and others don't see the "all else" as true.  We also think that those differences in state are in total strongly negative.

SO back to your *original* assertion, that is why people can reasonably conclude we might pass 2007/2012 this year. Like your estimation of melt, that has a rational basis.
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Re: Cryosphere Today 2013 Arctic SIA daily minimum: June poll
« Reply #102 on: June 22, 2013, 12:33:33 PM »
CT area: -207k6

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Re: Cryosphere Today 2013 Arctic SIA daily minimum: June poll
« Reply #103 on: June 22, 2013, 04:40:47 PM »
As has been pointed out so frequently on this forum, the volume of ice lost from this time of year until minimum remains nearly constant. It stands to reason that there will be something like 25% more volume at minimum this year than last.
... If you think it can be guaranteed, your starting point should surely be to explain why it has remained invariant.

Andrew - sounds like you are making an "all else being equal" argument, which isn't unreasonable. I, Chris and others don't see the "all else" as true.  We also think that those differences in state are in total strongly negative.

SO back to your *original* assertion, that is why people can reasonably conclude we might pass 2007/2012 this year. Like your estimation of melt, that has a rational basis.

2007 maybe, and even 2011, but I highly doubt we'll pass 2012. The period of greatest melt is coming to a close and there is significantly more ice than in 2012. The last week of June can drop like 2010's did and there would still be more ice than in 2012.

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Re: Cryosphere Today 2013 Arctic SIA daily minimum: June poll
« Reply #104 on: June 22, 2013, 05:19:48 PM »

2007 maybe, and even 2011, but I highly doubt we'll pass 2012. The period of greatest melt is coming to a close and there is significantly more ice than in 2012. The last week of June can drop like 2010's did and there would still be more ice than in 2012.

Here is where the logic of this could fail - the presumption the state of the ice at the end of June precludes higher rates of melt in July and August. This is another "all else being equal" assumption. Considering the experience of the last few years, that as a premise is a tad risky.
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Re: Cryosphere Today 2013 Arctic SIA daily minimum: June poll
« Reply #105 on: June 22, 2013, 05:49:13 PM »
JD Allen,

To be clear. I'm not being totally dismissive of the observation that volume loss from June to minimum hasn't changed. I just don't think it's safe to rely on that assumption. FWIW  I find both strident claims that we will see 2012 beaten and strident claims that we won't equally unconvincing.

Which is to say: I don't think anyone's put forward a solid argument for either case.

As an ongoing example: Now we have a 208km^2 drop in CT Area, while after the previous day's lack of loss I had found myself wondering if June's Cliff could be over for this year. That now leaves 2012 at 651 km^2 behind 2012, four days previously it was 933km^2 behind 2012. This alone should indicate that the lead could easily be reversed over the rest of June.

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Re: Cryosphere Today 2013 Arctic SIA daily minimum: June poll
« Reply #106 on: June 23, 2013, 01:53:13 AM »
Melt should be reaching its peak between now and mid July if my memory serves me correct.  There is a delay between peak insolation and actual melting as energy is transmitted into the ice from above and below.  This has been covered before but I don't remember the exact details. 

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Re: Cryosphere Today 2013 Arctic SIA daily minimum: June poll
« Reply #107 on: June 23, 2013, 02:40:23 AM »
  Things are certainly heating up!

  This month, I went back down to my April choice of the 1.50-1.75 bin, after having previously bumped up one bin in May due to the slow initial melt. For a central value and uncertainly, I would now pick:

(1.7 +/- 0.7) x 10^6 km^2

at one sigma. (So that is probably a 3-out-of-4 chance of beating last year's number, without actually bothering to work it out.)


  As others have discussed, it is all about the central Arctic region to a good approximation, as the other regions will essentially melt out anyway and their current state will have little effect on the central Arctic.

  For the first time, I expect essentially all of the ice to the East (Russian side) of the North Pole to melt out. (And an ice free Pole.) Now at the solstice, the satellite images show much of the Russian side to already be largely rubble, with a broad road through it showing mostly less than 75% concentration on the Bremen University map. I doubt that can survive the sun, the wind and the ocean currents over the next 3 months.

  Predicting the melt progress of the Western side seems more problematic as the ice doesn't have the obvious weaknesses of the Eastern side.

  And the other big question mark is, obviously, the weather through to mid-September.


  Whatever the outcome, we're watching history in the making, and it is exciting and sobering at the same time.
« Last Edit: June 23, 2013, 05:48:27 AM by slow wing »

ChrisReynolds

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Re: Cryosphere Today 2013 Arctic SIA daily minimum: June poll
« Reply #108 on: June 23, 2013, 09:02:29 AM »
Melt should be reaching its peak between now and mid July if my memory serves me correct.  There is a delay between peak insolation and actual melting as energy is transmitted into the ice from above and below.  This has been covered before but I don't remember the exact details.

July and August volume losses are greater than June's.

ChrisReynolds

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Re: Cryosphere Today 2013 Arctic SIA daily minimum: June poll
« Reply #109 on: June 23, 2013, 09:51:47 AM »
As of 21 June.

CT Area anomalies - the  June Cliff.



2013 Joins 2007, 2010, 2011 and 2012 as having a June Cliff. Notably this makes all of the post 2010 years notable in having a June Cliff, which I see as further support for the reality of the 2010 volume loss, link.

The loss from 1 June to 21 June is now the greatest loss for that period since the start of the satellite record.


BornFromTheVoid

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Re: Cryosphere Today 2013 Arctic SIA daily minimum: June poll
« Reply #110 on: June 23, 2013, 02:38:48 PM »
An increase of 13.6k on CT, mostly from the East Siberian sea, with little change elsewhere.
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Re: Cryosphere Today 2013 Arctic SIA daily minimum: June poll
« Reply #111 on: June 24, 2013, 04:45:56 AM »
The weather is not very favorable.

Except to help the Kara and Hudson melt out.


The Beaufort stays warm.  But most of the ESB and Laptev and the arctic basin are not Sunny and warm.

Then by day 5 a reverse Dipole forms.

This will help melt the Kara and some of the ice along the atlantic side.

But bring cooler air to the pacific side and warm air North of Greenland where the ice won't melt out regardless.


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BornFromTheVoid

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Re: Cryosphere Today 2013 Arctic SIA daily minimum: June poll
« Reply #112 on: June 24, 2013, 03:20:49 PM »
Here's how the current extent compares to the previous minima after today's update



Already within 3 million km2 of 5 previous minima.
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ChrisReynolds

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Re: Cryosphere Today 2013 Arctic SIA daily minimum: June poll
« Reply #113 on: June 24, 2013, 08:14:11 PM »
The June Cliff has ended, it lasted from 6 June to 18 June, and 2013 joins 2007, 2010, 2011 and 2012 in having a June Cliff.


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Re: Cryosphere Today 2013 Arctic SIA daily minimum: June poll
« Reply #114 on: June 24, 2013, 08:43:04 PM »
And it's higher than even 2008.
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Re: Cryosphere Today 2013 Arctic SIA daily minimum: June poll
« Reply #115 on: June 25, 2013, 08:09:14 AM »
And it's higher than even 2008.

Now we just wait to see how far down it can drop from this level, as happened in 2007, 2011 and 2012.

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Re: Cryosphere Today 2013 Arctic SIA daily minimum: June poll
« Reply #116 on: June 25, 2013, 08:19:33 AM »
I think 2007, 2008, 2010, 2011, and 2012 all hit 3.0 mil in area at some point which has to be like a 1.8 mil negative anomaly or so.

I still think 2013 will reach about 2.85 mil km2 in area at the min but could be higher if this weather keeps up.
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Oyvind Johnsen

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Re: Cryosphere Today 2013 Arctic SIA daily minimum: June poll
« Reply #117 on: June 25, 2013, 09:32:18 AM »
And it's higher than even 2008.

Now we just wait to see how far down it can drop from this level, as happened in 2007, 2011 and 2012.

It seems to me that of these years, only 2011 dropped after the June Cliff.
And if 2013 drops like 2011, it will end up between 2008 and 2010. To compete with 2007, 2011 and 2012 at the end of melt season, it will have to drop more like 2009 from now.

Richard Rathbone

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Re: Cryosphere Today 2013 Arctic SIA daily minimum: June poll
« Reply #118 on: June 25, 2013, 11:52:07 AM »
And it's higher than even 2008.

Now we just wait to see how far down it can drop from this level, as happened in 2007, 2011 and 2012.

It seems to me that of these years, only 2011 dropped after the June Cliff.
And if 2013 drops like 2011, it will end up between 2008 and 2010. To compete with 2007, 2011 and 2012 at the end of melt season, it will have to drop more like 2009 from now.

I can't find the plot to double-check right now, but I am pretty sure the flat-line at the bottom of the cliff only lasts through July and then they all go down again in August. Thats why it being a melt ponding artefact made sense to me. Its most of June and July's melting showing up in advance as melt ponds.

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Re: Cryosphere Today 2013 Arctic SIA daily minimum: June poll
« Reply #120 on: June 25, 2013, 07:00:43 PM »
A note on anomalies:

The anomalies are the difference from the average seasonal cycle. When anomalies are level this shows that the current rate of loss is equal to the average seasonal cycle's rate of loss. When anomalies go up the current rate of loss has fallen behind the average, when anomalies go down the current rate of loss is greater than the average.

2007, 2011 and 2012 all show a short levelling of anomalies after the June Cliff, then after mid June (late June for 2012) anomalies fall, indicating greater loss rates than the average seasonal cycle.

Given the state of the ice it is very hard to imagine how anomalies will not begin to fall in July. Just because sea ice area is greater than all post 2007 years at present does not mean that will remain the case. July and August have very large losses of volume, and if the ice is of similar thickness to the post 2010 years that large volume loss will probably result in large area loss.

It is worth noting that CT Area for 2013 is only about 200k km^2 above that for 2011. 2011 resulted in 2007 being met (record in some datasets, no record in others).

PS for what it's worth - I don't take claims of a massive crash this year at all seriously.

Neven

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Re: Cryosphere Today 2013 Arctic SIA daily minimum: June poll
« Reply #121 on: June 25, 2013, 10:46:51 PM »
Past couple of days CT SIA: Century break - small uptick - century break - small uptick - century break - small uptick...

Those clouds, holes and melt ponds are making the sensors sweat.  :)
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Pmt111500

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Re: Cryosphere Today 2013 Arctic SIA daily minimum: June poll
« Reply #122 on: June 26, 2013, 05:42:36 AM »
Quote
Past couple of days CT SIA: Century break - small uptick - century break - small uptick - century break - small uptick...

Those clouds, holes and melt ponds are making the sensors sweat. 

You sure this isn't a result of the US bicameral two party political system?? ;-)  Camera one says "it's ice" and camera two says "no way!"

Juan C. García

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Re: Cryosphere Today 2013 Arctic SIA daily minimum: June poll
« Reply #123 on: June 26, 2013, 06:23:54 AM »
Past couple of days CT SIA: Century break - small uptick - century break - small uptick - century break - small uptick...
Those clouds, holes and melt ponds are making the sensors sweat.  :)
Yesterday I saw an important melt on Hudson Bay and Baffin/Newfoundland Seas, but it was offset by more ice on East Siberian Sea, Canadian Archipelago and Arctic Basin.
Today seems that Arctic sea ice was waiting to melt after the speech of President Obama. Now I see weakness on Hudson Bay, Canadian Archipelago, Arctic Basin and the seas of Kara, Greenland, Baffin and Newfoundland.
I will wait for the possible drop on CT SIA this week.
Or maybe Century break - small uptick - century break - small uptick...? 



Which is the best answer to Sep-2012 ASI lost (compared to 1979-2000)?
50% [NSIDC Extent] or
73% [PIOMAS Volume]

Volume is harder to measure than extent, but 3-dimensional space is real, 2D's hide ~50% thickness gone.
-> IPCC/NSIDC trends [based on extent] underestimate the real speed of ASI lost.

jdallen

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Re: Cryosphere Today 2013 Arctic SIA daily minimum: June poll
« Reply #124 on: June 26, 2013, 06:27:30 AM »
I am confused by the SIA increases. It is simply not cold enough for significant ice creation.  Where is it coming from ?!
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Pmt111500

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Re: Cryosphere Today 2013 Arctic SIA daily minimum: June poll
« Reply #125 on: June 26, 2013, 07:36:49 AM »
Quote
I am confused by the SIA increases. It is simply not cold enough for significant ice creation.  Where is it coming from ?!

from leads of under 200 m wide?

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Re: Cryosphere Today 2013 Arctic SIA daily minimum: June poll
« Reply #126 on: June 26, 2013, 09:00:50 AM »
I am confused by the SIA increases. It is simply not cold enough for significant ice creation.  Where is it coming from ?!
Measurement inaccuracies.

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Re: Cryosphere Today 2013 Arctic SIA daily minimum: June poll
« Reply #127 on: June 26, 2013, 09:29:55 AM »
I am confused by the SIA increases. It is simply not cold enough for significant ice creation.  Where is it coming from ?!
Fragmentation and dispersion could contribute, especially in areas where the ice is warm, soft and slushy.
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Re: Cryosphere Today 2013 Arctic SIA daily minimum: June poll
« Reply #128 on: June 26, 2013, 01:31:53 PM »
Area about the same as yesterday

Juan C. García

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Re: Cryosphere Today 2013 Arctic SIA daily minimum: June poll
« Reply #129 on: June 26, 2013, 06:52:03 PM »
I was expecting a drop in CT SIA today. I understand that it hasn’t drop in 3 or 4 days, but I see important changes on Bremen AMSR2 ASI concentration. I don´t see the same changes on the CT image.
I don´t expect to see this melt on NSIDC or Bremen values, because they use extent on their images (not area). But why CT SIA is not dropping? Which satellite does CT uses? Does it have some time lag? Can anybody give me a link to know how CT makes their SIA calculation?
Which is the best answer to Sep-2012 ASI lost (compared to 1979-2000)?
50% [NSIDC Extent] or
73% [PIOMAS Volume]

Volume is harder to measure than extent, but 3-dimensional space is real, 2D's hide ~50% thickness gone.
-> IPCC/NSIDC trends [based on extent] underestimate the real speed of ASI lost.

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Re: Cryosphere Today 2013 Arctic SIA daily minimum: June poll
« Reply #130 on: June 26, 2013, 07:51:02 PM »
Juan, I think that ct area data has an extra lag of two days, compared with other indexes.

Cross correlation seems to show it:

https://forum.arctic-sea-ice.net/index.php/topic,382.msg7823.html#msg7823

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Re: Cryosphere Today 2013 Arctic SIA daily minimum: June poll
« Reply #131 on: June 26, 2013, 10:00:55 PM »
FWIW, In preparation for my June Status blog post, I find myself being drawn to the conclusion that on current performance 2013 is unlikely to be as low as even 2007.

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Re: Cryosphere Today 2013 Arctic SIA daily minimum: June poll
« Reply #132 on: June 26, 2013, 10:53:48 PM »
........................I find myself being drawn to the conclusion that on current performance 2013 is unlikely to be as low as even 2007.

That sir, is a question being asked by great minds and lesser mortals alike!!  With so many factors being unique in 2013, it's hard to predict what the next three months will do.

Is there any probability that this years melt will drift into October, even if just for a few days or a week??
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Juan C. García

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Re: Cryosphere Today 2013 Arctic SIA daily minimum: June poll
« Reply #133 on: June 26, 2013, 11:37:55 PM »
Is there any probability that this years melt will drift into October, even if just for a few days or a week??
I made a study looking for the difference between the official NSIDC monthly average and what should be the statistical monthly average (that is, average of the daily values). I had interesting results, but I stop writing the Assay because I’m working on another field. I have several graphs and I will look to put them on this Forum.
One of the conclusions is that the Official NSIDC October monthly average is overvalue against the statistical monthly average. So from my point of view, the answer is that if there is a September ice-free Arctic Ocean, then we can have an ice-free on the first week of October. It is just that the Ocean is warm at the beginning of October and the NSIDC monthly average tends to give a value that corresponds to October 18-25.

« Last Edit: June 26, 2013, 11:44:02 PM by Juan C. García »
Which is the best answer to Sep-2012 ASI lost (compared to 1979-2000)?
50% [NSIDC Extent] or
73% [PIOMAS Volume]

Volume is harder to measure than extent, but 3-dimensional space is real, 2D's hide ~50% thickness gone.
-> IPCC/NSIDC trends [based on extent] underestimate the real speed of ASI lost.

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Re: Cryosphere Today 2013 Arctic SIA daily minimum: June poll
« Reply #134 on: June 27, 2013, 07:47:36 AM »
........................I find myself being drawn to the conclusion that on current performance 2013 is unlikely to be as low as even 2007.

That sir, is a question being asked by great minds and lesser mortals alike!!  With so many factors being unique in 2013, it's hard to predict what the next three months will do.

Is there any probability that this years melt will drift into October, even if just for a few days or a week??

No. None.

The date of minimum, after which ice area (CT Area) increases has remained largely invariant over the course of the satellite record. i.e. there is no relationship between date of minimum and area and the area at that date.

This supports the idea that the date of area minimum is set by insolation. Once the sun starts to set net energy flow is out of the ocean/ice system and into the atmosphere. No further significant melt occurs, ice formation starts once the ocean has cooled to around zero deg C.

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Re: Cryosphere Today 2013 Arctic SIA daily minimum: June poll
« Reply #135 on: June 27, 2013, 01:08:14 PM »


One of the conclusions is that the Official NSIDC October monthly average is overvalue against the statistical monthly average.

You are confusing yourself by thinking that the NSIDC monthly extent is an average. It isn't. Its the monthly extent. NSIDC say things like "Arctic sea ice extent for May 2013 was 13.10 million square kilometers". No mention of "average" there. Its the extent for May, not the average daily extent during May.

Extent varies depending on the grid scale used, both in space and time. Daily extent isn't an average of hourly extent, and monthly extent isn't an average of daily extent. Extent based on  100km blocks isn't an average of extent based on 10 km blocks within it.

Larger grid blocks and longer times give higher values of extent. Thats an expected consequence of the way extent is defined.

The average daily extent for a month may be a statistic that you are interested in, but its not one that NSIDC is using and you are misrepresenting them by calling their monthly extent an average.

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Re: Cryosphere Today 2013 Arctic SIA daily minimum: June poll
« Reply #136 on: June 27, 2013, 01:40:49 PM »
Century break!

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Re: Cryosphere Today 2013 Arctic SIA daily minimum: June poll
« Reply #137 on: June 27, 2013, 01:51:50 PM »
If I didn't miscalculate Global Sea Ice Area would be today (day 176) 19,999 million sq. km, about the same as in 2010 but around 1 million sq. km more than in the lowest years on record.

Northern Hemisphere Sea Ice Anomaly is 0,898 (million sq. km) below the mean.
A week ago, the Southern Hemisphere Sea Ice Anomaly was way above normal, today it's "just" 0.526 (million sq. km) above the anomaly from 1979-2008 mean.

http://arctic.atmos.uiuc.edu/cryosphere/antarctic.sea.ice.interactive.html

http://meteomodel.pl/klimat/globalice.png


Juan C. García

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Re: Cryosphere Today 2013 Arctic SIA daily minimum: June poll
« Reply #138 on: June 27, 2013, 02:48:20 PM »
You are confusing yourself by thinking that the NSIDC monthly extent is an average. It isn't. Its the monthly extent. NSIDC say things like "Arctic sea ice extent for May 2013 was 13.10 million square kilometers". No mention of "average" there. Its the extent for May, not the average daily extent during May.
Extent varies depending on the grid scale used, both in space and time. Daily extent isn't an average of hourly extent, and monthly extent isn't an average of daily extent.
A year ago I was confusing myself by thinking that the NSIDC monthly extent was an average of the daily values (and I believe that I am not the only one making that mistake). Now I am maybe wrong by using the term “Official NSIDC monthly average” and I should use the term “Official NSIDC Monthly Extent”. But anyway, what I am looking to highlight is precisely the difference between the “Official NSIDC Monthly Extent” and an average of NSIDC daily values on a given month.
NSIDC defines a daily extent as grids that have 15% or more of ice in a given day. If this grid has 15% or more of ice, then the grid counts as if it has 100% of ice. I believe that this criteria was good in the XX Century, but can overvalue the sea ice extent now, that we can have a lots of grids with 15% or a little more of ice. So I tend to be concern about the concept of daily extent.
But I find more misleading the concept of monthly extent. NSIDC defines monthly extent as the sum of grids that have 15% or more of ice in a month. But especially in July, October and November, the ice at the start of the month is very different of the ice at the end of the month. On July, the ice is melting quickly and on October and November, the water of the ocean is freezing quickly. So in July, the NSIDC monthly extent is close to the daily values that we have on July 5-12th. It doesn’t matter if afterwards we have a strong melt on the month. An in October and November, the NSIDC monthly extent is also close to the daily values that we have on October 18-25th and November 18-25th, respectively.  Especially in October, it doesn’t matter if the first week of October we have values similar to those close to the minimum of the year and then we have a strong freeze-up. The Official NSIDC October value will reflect the strong freeze-up, not the slow start of freeze.
As a conclusion, what I mean is that if a daily extent could be overvalue now that the Arctic Sea Ice is melting, as never before in the history of the human being, the Official Monthly Extent is worst because it is overvalue against an average of the daily extent values.
So for me it is better to follow area or volume, instead of extent, and if I follow extent, I look at the daily values but I find very misleading the concept of monthly extent. And that is a concern when I see that a lot of models using monthly extent.
« Last Edit: June 27, 2013, 03:03:22 PM by Juan C. García »
Which is the best answer to Sep-2012 ASI lost (compared to 1979-2000)?
50% [NSIDC Extent] or
73% [PIOMAS Volume]

Volume is harder to measure than extent, but 3-dimensional space is real, 2D's hide ~50% thickness gone.
-> IPCC/NSIDC trends [based on extent] underestimate the real speed of ASI lost.

Wipneus

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Re: Cryosphere Today 2013 Arctic SIA daily minimum: June poll
« Reply #139 on: June 27, 2013, 03:39:20 PM »
NSIDC calls their monthly extent routinely "average". From the arctic news Oktober 2012:


dree12

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Re: Cryosphere Today 2013 Arctic SIA daily minimum: June poll
« Reply #140 on: June 27, 2013, 06:05:44 PM »
NSIDC calls their monthly extent routinely "average". From the arctic news Oktober 2012:



I feel this is simply an ambiguity of language. With brackets, the heading can be read as either "Average (Monthly Arctic Sea Ice Extent)" or "(Average Monthly Arctic Sea Ice) Extent". The latter is meant, and it means the extent of average ice rather than the average ice extent.

ChrisReynolds

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Re: Cryosphere Today 2013 Arctic SIA daily minimum: June poll
« Reply #141 on: June 27, 2013, 08:16:29 PM »
NSIDC Sea Ice Index User Documentation, Monthly format.
Quote
These images and data files present ice extent and area averaged over a month.
Link

Richard Rathbone

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Re: Cryosphere Today 2013 Arctic SIA daily minimum: June poll
« Reply #142 on: June 27, 2013, 09:27:08 PM »
The only thing they actually average is concentration.

Juan C. García

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Re: Cryosphere Today 2013 Arctic SIA daily minimum: June poll
« Reply #143 on: June 27, 2013, 11:47:09 PM »
Especially in October, it doesn’t matter if the first week of October we have values similar to those close to the minimum of the year and then we have a strong freeze-up. The Official NSIDC October value will reflect the strong freeze-up, not the slow start of freeze.
 
That is what happened on October 2012. I didn’t accept that the Official NSIDC October Extent was 7 million km2, because it was far away of what should be the average of the October daily values and because it was above 2007. Thanks to the explanations of Wipneus, Piotr Djaków, Aaron Lewis, Werther, P-Maker and others, I find out that the Official NSIDC October Extent was greatly overvalued against the average of the NSIDC daily values.
In the next graph, the “Average October?” is the 7 million km2 that we call now “Official NSIDC October Extent”.


 

That was discussed on Neven’s Blog, on the comments in:

http://neven1.typepad.com/blog/2012/10/looking-for-winter-weirdness-2.html

http://neven1.typepad.com/blog/2012/11/ct-sia-finally-above-2-million-km2-anomaly-mark.html
« Last Edit: June 27, 2013, 11:53:29 PM by Juan C. García »
Which is the best answer to Sep-2012 ASI lost (compared to 1979-2000)?
50% [NSIDC Extent] or
73% [PIOMAS Volume]

Volume is harder to measure than extent, but 3-dimensional space is real, 2D's hide ~50% thickness gone.
-> IPCC/NSIDC trends [based on extent] underestimate the real speed of ASI lost.

Juan C. García

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Re: Cryosphere Today 2013 Arctic SIA daily minimum: June poll
« Reply #144 on: June 28, 2013, 06:50:52 AM »
This is the average overvalue that we have by month, if we made and average of the difference between the NSIDC Official Monthly Extent and the NSIDC average of the daily values, on the 34 years of data (1979-2012).
Which is the best answer to Sep-2012 ASI lost (compared to 1979-2000)?
50% [NSIDC Extent] or
73% [PIOMAS Volume]

Volume is harder to measure than extent, but 3-dimensional space is real, 2D's hide ~50% thickness gone.
-> IPCC/NSIDC trends [based on extent] underestimate the real speed of ASI lost.

Juan C. García

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Re: Cryosphere Today 2013 Arctic SIA daily minimum: June poll
« Reply #145 on: June 28, 2013, 07:03:52 AM »
These are the months in which there is the 20 maximum differences between the NSIDC Official Monthly Extent and the average of the NSIDC daily values of the month. All of them are 500+ km2. only one is November, the others are in October.
Which is the best answer to Sep-2012 ASI lost (compared to 1979-2000)?
50% [NSIDC Extent] or
73% [PIOMAS Volume]

Volume is harder to measure than extent, but 3-dimensional space is real, 2D's hide ~50% thickness gone.
-> IPCC/NSIDC trends [based on extent] underestimate the real speed of ASI lost.

Juan C. García

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Re: Cryosphere Today 2013 Arctic SIA daily minimum: June poll
« Reply #146 on: June 28, 2013, 07:31:16 AM »
These are the months in which there are the 20 minimum differences (not absolute value, but negative or minimum positive value). I believe that the -182.3 km2 of July 1987 is a NSIDC mistake on their values (I retrieved them on March 5, 2013 and I haven’t check them since then). But I hope is my mistake. In fact, I hope that my analysis is wrong and there is not a big difference between the Official NSIDC Monthly Extent and the average of the daily values on the month.
I excuse myself to put this NSIDC Extent Analysis on the CT SIA poll :), but I decided to just follow the discussion. Thank you for reading this analysis and I will appreciate your comments.
« Last Edit: June 28, 2013, 07:44:11 AM by Juan C. García »
Which is the best answer to Sep-2012 ASI lost (compared to 1979-2000)?
50% [NSIDC Extent] or
73% [PIOMAS Volume]

Volume is harder to measure than extent, but 3-dimensional space is real, 2D's hide ~50% thickness gone.
-> IPCC/NSIDC trends [based on extent] underestimate the real speed of ASI lost.

Peter Ellis

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Re: Cryosphere Today 2013 Arctic SIA daily minimum: June poll
« Reply #147 on: June 28, 2013, 09:38:52 AM »
Any monthly average involves two averaging steps:

(1) Average over time
(2) Sum over pixels

All this dreadfully long-winded exercise proves is that it matters which order you do the two in, because you get different results.  NEITHER ANSWER IS WRONG, they're simply answers to different questions. There is some incredibly obnoxious rudeness and disrespect being tossed around in this thread, and it's not appropriate for this forum.

Juan C. García

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Re: Cryosphere Today 2013 Arctic SIA daily minimum: June poll
« Reply #148 on: June 28, 2013, 01:32:09 PM »
Any monthly average involves two averaging steps:

(1) Average over time
(2) Sum over pixels

All this dreadfully long-winded exercise proves is that it matters which order you do the two in, because you get different results.  NEITHER ANSWER IS WRONG, they're simply answers to different questions. There is some incredibly obnoxious rudeness and disrespect being tossed around in this thread, and it's not appropriate for this forum.

Peter Ellis:
I have been trying to be as respectful as possible, but the fact is that I disagree with the concept on monthly extent. If the Monthly Extent is define as the sum of grids that have 15% or more of ice in a month, then if 15% of the days have 100% of ice, the grid will be catalog as 100% of ice in the whole month. The 15% of 31 days (the longest months) is 4.65. So rounding it, if a grid has 100% of ice on 5 days in a month, then that grid will count as 100% the whole month.
Some grids will not be catalog as 100% of ice in a given day, so if a grid has 20% of ice in a day, the grid should have extra days that will cover 80% of a day with ice (again, rounding it). That is why I affirm 5 days of the beginning of July or 5 days at the end of October, November and December are not enough to match the NSIDC Official Extent and I give some extra days.
I respect the Scientifics of NSIDC. I know that they have made excellent contributions to the recognition of AGW. But that doesn’t mean that I have to agree to the way they are measuring the Arctic Sea Ice. As I said before, I am concern that the concept of daily extent is over valuating the ASI in a moment that we are going to have an Arctic free of ice. But Official Monthly Extent overvaluates even more. Even that I wish I’m wrong, I believe I am not. I also wish that this Forum is wrong when it votes in a poll and the result is that we are going to have an ice-free Arctic before 2020 and I will be very happy if we don’t break any record in 2013. But we cannot be talking about a possible collapse of our planet and accept that our way to measure it can have a concept that brings the wrong conclusions. The true is that all the values that I am using in the analysis are NSIDC values and my concern is valid. It is the mission of this Forum to find what is happening on the Arctic sea ice and my analysis is completely appropriate to be in this Forum.
I invite everybody to revise the numbers. Again, I wish I'm wrong.
« Last Edit: June 28, 2013, 02:14:06 PM by Juan C. García »
Which is the best answer to Sep-2012 ASI lost (compared to 1979-2000)?
50% [NSIDC Extent] or
73% [PIOMAS Volume]

Volume is harder to measure than extent, but 3-dimensional space is real, 2D's hide ~50% thickness gone.
-> IPCC/NSIDC trends [based on extent] underestimate the real speed of ASI lost.

Richard Rathbone

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Re: Cryosphere Today 2013 Arctic SIA daily minimum: June poll
« Reply #149 on: June 28, 2013, 02:54:18 PM »
As June draws to a close I ask myself whether I would change my prediction (2.25-2.5) if a new poll was opened today.

The main reason that area is high compared to 2012 at the moment are slow melts in the Hudson, Kara and Beaufort. Everywhere else is pretty close to the 2012 schedule. The Hudson will shortly catch up as it finishes melting, the Kara is moving fast enough that it looks to melt out eventually although later than last year, but the Beaufort is not only slow compared to 2012, its slower than the historical average. So with every region but the Beaufort on schedule to match 2012 I find much the same diagnosis from area development at the end of June as I did from May PIOMAS at the beginning. A little bit higher than 2012, with the Beaufort being the region with the extra ice.

I'm expecting PIOMAS to show a lower June volume melt than 2012. If it doesn't continue to spin out of the Death Spiral again this month, I'll be rather more aggressive in my melt projection for the July poll.