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Neven

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Re: 2017 sea ice area and extent data
« Reply #150 on: April 09, 2017, 11:28:58 AM »
I know I said they should be ignored, but will this adjustment give climate risk deniers something to shout about? For instance, if later years get revised downwards more than earlier years. The whole reason for adjusting seems complicated enough for some nice spin.
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oren

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Re: 2017 sea ice area and extent data
« Reply #151 on: April 09, 2017, 12:12:14 PM »
I know I said they should be ignored, but will this adjustment give climate risk deniers something to shout about?
Of course it will, but science should continue in spite of that. It's like living with a psychotic person, even when you are perfect you always seem to fail and blame yourself. At some point you must realise you should be true to yourself.

Neven

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Re: 2017 sea ice area and extent data
« Reply #152 on: April 09, 2017, 12:16:52 PM »
I'm not talking about blaming anyone, and climate risk deniers will do as they always will, but I was just wondering if they might get some traction with this. The Lord knows they need some Arctic propaganda to stall the inevitable.
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LRC1962

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Re: 2017 sea ice area and extent data
« Reply #153 on: April 09, 2017, 02:51:40 PM »
I'm not talking about blaming anyone, and climate risk deniers will do as they always will, but I was just wondering if they might get some traction with this. The Lord knows they need some Arctic propaganda to stall the inevitable.
Any time when scientists start talking about probabilities, even among those at odds among their peer group, unless you are deadly accurate in your predictions, you are leaving yourself open to ridicule. A case in point was Einstein's theory of General Relativity.   The only way it could then be tested was to get a precise measurement of deflection of light  from a star around the sun. Took years to get that measurement for proof and finally got the proof he needed.
As for measurements today? you are relying on satellite data that is still primarily 2d and getting data only during a passover, unlike what you can get on geostationary equatorial stations. As satelittes improve and get better data then can update old data basing it on old data you will get changes. Problem is that unless you can and care to understand the math involved, you will never truely believe that the science is good.
"All truth passes through three stages: First, it is ridiculed; Second,  it is violently opposed; and Third, it is accepted as self-evident."
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Shared Humanity

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Re: 2017 sea ice area and extent data
« Reply #154 on: April 09, 2017, 03:31:05 PM »
I know I said they should be ignored, but will this adjustment give climate risk deniers something to shout about? For instance, if later years get revised downwards more than earlier years. The whole reason for adjusting seems complicated enough for some nice spin.

Climategate 3 or 4 or whatever. How difficult would it be for them to generate both metrics simultaneously for a couple of years? This way we could still track long term trends by looking at the existing metric while evaluating the effectiveness of the change in capturing what has really been going on.

gerontocrat

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Re: 2017 sea ice area and extent data
« Reply #155 on: April 09, 2017, 03:41:23 PM »
"Facts are stubborn things; and whatever may be our wishes, our inclinations, or the dictates of our passions, they cannot alter the state of facts and evidence."     John Adams

"Publish and be damned".   Lord Wellington
"Para a Causa do Povo a Luta Continua!"

BornFromTheVoid

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Re: 2017 sea ice area and extent data
« Reply #156 on: April 09, 2017, 07:02:28 PM »
Update for the week to April 8th

The current 5 day trailing average is on 14,090,000km2 while the 1 day extent is at 13,995,000km2.

(All the following data is based on a trailing 5 day average)
The daily anomaly (compared to 81-10) is at -970,000km2, a decrease from -1,114,000km2 last week. The anomaly compared to the 07, 11 and 12 average is at -392,000km2, a decrease from -477,000km2 last week. We're currently 3rd lowest on record, down from lowest last week.



The average daily change over the last 7 days was -10.9k/day, compared to the long term average of -31.5k/day, and the 07, 11 and 12 average of -23.1k/day.
The average long term change over the next week is -39.6k/day, with the 07, 11, and 12 average being -31.4k/day.



The extent loss so far this April is the 6th smallest record. To achieve the largest loss, a drop of at least 73.1k/day is required (over -72.3k/day with with single day values), while the smallest drop requires a loss of less than 31.0k/day (loss less than 26.1k/day with single day values) and an average loss requires a drop of 49.7k/day (-46.7k/day with single day values).


Jim Pettit

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Re: 2017 sea ice area and extent data
« Reply #157 on: April 10, 2017, 03:06:15 PM »
In not earth-shattering but nonetheless interesting news, NSIDC extent has experienced back-to-back century drops. That's a fairly rare thing so early in the season; it hasn't happened prior to April 10 since 2004. 2016 is now just 5k behind 2016, and should retake first place in the next few days, at least for awhile.

Wipneus

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Re: 2017 sea ice area and extent data
« Reply #158 on: April 10, 2017, 03:39:09 PM »
Wipneus: I was thinking about these for example CT-area numbers that you posted quite regularly during the melting season last year.  :)

http://forum.arctic-sea-ice.net/index.php/topic,1457.msg87403.html#msg87403

Best regards, LMV


Because the Cryosphere Today seems to have stopped for good, and there is a better alternative: my NSIDC area, I decided to stop the CT area calculation.

Remember that CT-area is calculated from the same source, NSIDC sea ice concentration but with some differences that make direct comparison with NSIDC extent impossible.

- not taking the true grid cell area in account;
- including lake ice;
- no revisions when the input data (sea ice concentration) is revised;
- not making a 15% cutoff;

On my side it would not be a big deal to restart the CT calculation again, but in my opinion the confusion would not make it worth it (unless CT comes back again).

Wipneus

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Re: 2017 sea ice area and extent data
« Reply #159 on: April 15, 2017, 12:41:13 PM »
Kevin Pluck created a wonderful video with animated NSIDC sea ice extent, SH, NH and Global.

Link to the video

More of Kevin's work here

TerryM

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Re: 2017 sea ice area and extent data
« Reply #160 on: April 15, 2017, 04:00:27 PM »
Jesus H Christ !


Terry

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Re: 2017 sea ice area and extent data
« Reply #161 on: April 16, 2017, 03:23:00 PM »
Update for the week to April 15th

The current 5 day trailing average is on 13,817,000km2 while the 1 day extent is at 13,739,000km2.

(All the following data is based on a trailing 5 day average)
The daily anomaly (compared to 81-10) is at -966,000km2, a decrease from -970,000km2 last week. The anomaly compared to the 07, 11 and 12 average is at -445,000km2, an increase from -392,000km2 last week. We're currently lowest on record, up from 3rd lowest last week.



The average daily change over the last 7 days was -38.9k/day, compared to the long term average of -39.6k/day, and the 07, 11 and 12 average of -31.4k/day.
The average long term change over the next week is -37.3k/day, with the 07, 11, and 12 average being -22.8k/day.



The extent loss so far this April is the 12th smallest record. To achieve the largest loss, a drop of at least 84.6k/day is required (more than -91.6k/day with with single day values), while the smallest drop requires a loss of less than 23.0k/day (less than 20.5k/day with single day values) and an average loss requires a drop of 50.4k/day (-52.1k/day with single day values).


Juan C. García

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Re: 2017 sea ice area and extent data
« Reply #162 on: April 18, 2017, 02:26:02 AM »
I made this graph that shows the number of days on a year, in which the day breaks a record or stays at the second or third lowest.

I would say that it represents the stress that we suffer on a daily basis, wondering what will happen on a particular year.

It is interesting that the worst years are 2005, 2006, 2007 and 2016. Of course, these are for the whole year and in 2012 we didn't have too much days of breaking record, but they happened exactly when they count: at the end of the melting season!
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: 2017 sea ice area and extent data
« Reply #163 on: April 18, 2017, 02:32:48 AM »
This is a similar graph, but only looking at the days on the melting season (kind of arbitrary the assignation of days at the melting season).
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: 2017 sea ice area and extent data
« Reply #164 on: April 18, 2017, 03:05:51 AM »
To better understand the previous graphs, this is the NSIDC graph for 2005 and previous years. So it is easy to see that 2005 was breaking records continuously, on a daily basis. Of course, here I don't show 2006, but 2006 broke several records of 2005. And so on, year after year.
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.

gerontocrat

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Re: 2017 sea ice area and extent data
« Reply #165 on: April 21, 2017, 01:36:36 PM »
Hullo Juan,

I have highlighted a bit of your post which I think I disagree with. Yes, I am being picky.

It is interesting that the worst years are 2005, 2006, 2007 and 2016. Of course, these are for the whole year and in 2012 we didn't have too much days of breaking record, but they happened exactly when they count: at the end of the melting season!

The 2012 end of season melt could be regarded as least important in 2 ways:-
- early season melt (as in 2016) maximises positive feedback from insolation and from that ocean warming to inhibit winter sea ice growth,
- by late August  / September the sun is heading South and insolation is in rapid decline,
- some of us still think maybe it is only when winter sea ice reduces sufficiently will we see an ice-free summer (though the Jury is still out on that one - 2012 does NOT support that speculation).

I wonder what the graph if it included freezing months only would look like. Is there any correlation between winter sea ice volume maxima and summer minima ? (I bet someone on ASIF has done it).
"Para a Causa do Povo a Luta Continua!"

AndrewB

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Re: 2017 sea ice area and extent data
« Reply #166 on: April 21, 2017, 03:49:21 PM »
...
Is there any correlation between winter sea ice volume maxima and summer minima ? (I bet someone on ASIF has done it).
GC,
Sorry to point out the obvious, but there is no need to calculate a statistical correlation between winter sea ice volume maxima and summer minima, because the two are directly related by a simple formula:
summer ice minimum = (previous) winter ice maximum - total spring/summer melt

The evolution of the three interlinked variables over time is completely summarized in the following excellent chart by Jim Pettit:

CognitiveBias

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Re: 2017 sea ice area and extent data
« Reply #167 on: April 21, 2017, 04:08:41 PM »
...
Is there any correlation between winter sea ice volume maxima and summer minima ? (I bet someone on ASIF has done it).
GC,
Sorry to point out the obvious, but there is no need to calculate a statistical correlation between winter sea ice volume maxima and summer minima, because the two are directly related by a simple formula:
summer ice minimum = (previous) winter ice maximum - total spring/summer melt

The evolution of the three interlinked variables over time is completely summarized in the following excellent chart by Jim Pettit:

As max trends lower, min also trends lower.  Sounds like a positive correlation to me.   I'm not sure of the value of this statistic, but the 'obvious' dismissal is a bit much.

AndrewB

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Re: 2017 sea ice area and extent data
« Reply #168 on: April 21, 2017, 04:38:48 PM »
The obvious refers to the fact that there is not a statistical correlation; while there is actually a straightforward logical and mathematical relation. And the excellent chart makes this relation quite obvious, as does the formula.

It's much like asking if the number of ice creams the iceman has in his truck at the end of the day is statistically correlated with the number of ice creams he had in his truck when he exited the factory in the morning. The obvious answer is that there is no need to work out a statistical correlation because we know exactly that:
ice creams at the end of the day = ice creams in the morning - ice creams sold *

Is it obvious why it's obvious?  ???

* In some rare cases, this relation may not hold true. I would suspect the iceman, not the statistician.  ;)
« Last Edit: April 21, 2017, 04:58:14 PM by AndrewB »

oren

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Re: 2017 sea ice area and extent data
« Reply #169 on: April 21, 2017, 04:47:24 PM »
Indeed there is a relation but the correlation does depend in some cases on the third variable, namely the annual loss. Had there been a 100% correlation between max volume and annual loss, there could be 0% correlation between max and min volume. Indeed this is what will happen when min volume is 0 every year.
In reality though, annual loss remained stable and then even increased as max volume decreased over the years. Therefore min volume, on average, is dropping even faster than max volume.

AndrewB

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Re: 2017 sea ice area and extent data
« Reply #170 on: April 21, 2017, 05:06:46 PM »
Indeed there is a relation but the correlation does depend in some cases on the third variable, namely the annual loss. Had there been a 100% correlation between max volume and annual loss, there could be 0% correlation between max and min volume. Indeed this is what will happen when min volume is 0 every year.
...

Indeed, that's the case whenever the iceman sells all the ice creams in his truck.

But the correct analysis is not that there is a 100% correlation between number of ice creams in the truck in the morning and the number of ice creams sold, but quite simply that on that day, the iceman sold all the ice creams he had picked up in the morning.

When x - y =0, you don't say that x is 100% statistically correlated to y, you just say x = y.
« Last Edit: April 21, 2017, 05:36:38 PM by AndrewB »

Juan C. García

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Re: 2017 sea ice area and extent data
« Reply #171 on: April 21, 2017, 11:19:17 PM »
Hullo Juan,

I have highlighted a bit of your post which I think I disagree with. Yes, I am being picky.

It is interesting that the worst years are 2005, 2006, 2007 and 2016. Of course, these are for the whole year and in 2012 we didn't have too much days of breaking record, but they happened exactly when they count: at the end of the melting season!

The 2012 end of season melt could be regarded as least important in 2 ways:-
- early season melt (as in 2016) maximises positive feedback from insolation and from that ocean warming to inhibit winter sea ice growth,
- by late August  / September the sun is heading South and insolation is in rapid decline,
- some of us still think maybe it is only when winter sea ice reduces sufficiently will we see an ice-free summer (though the Jury is still out on that one - 2012 does NOT support that speculation).

I wonder what the graph if it included freezing months only would look like. Is there any correlation between winter sea ice volume maxima and summer minima ? (I bet someone on ASIF has done it).

Hi gerontocrat.

Thank for your comment, but I am not sure that I understand it.

2012 started a little low in January and February, but in March it had an important refreeze. So, the daily records on the first five months were not too many, as you can see on the first graph, that compares 2012 with 2007, 2010 and 2011. Even in April, 2012 was above the 1981-2010 average. The melt in June was important, but the real difference appeared after the Great Arctic Cyclone, on August. So, most of the 2012 daily records happened on the second semester, as you can see on the second graph.

2016 was completely the other way. We have daily records almost the whole year, except for July, September and the first half of October. So, I was expecting a minimum record at 2016 lower than what finally happened. I don’t agree with some conclusions that NSIDC makes public, specifically, that 2016 was the fifth lower year. From my point of view, 2016 should be cataloged as the second or at least the third worst year on record, because that it is what it was, in area, daily extent and volume. But well, that is another story.

2016 had 182 days being the daily lowest (against 1979-2015) and 312 days being among the three lowest on record.
2012 had 125 days being the daily lowest (against 1979-2011) and 211 days being among the three lowest on record.

That is, according to my calculations. I compare the days on the year as NSIDC do on a Charctic graph. That is, I compared day 60 on 2011 with day 60 on 2012. Being 2012 a leap year, the 60th day will be Feb 29, while on 2011 would be March 1st. These is what we visually see on Charctic, but the numbers could change a little, if I erase the feb 29´s and I compare the dates matching for the day on the month.

Regarding your last question, I believe that it is not a rule that the year that has a winter minimum, will have a summer minimum. But surely, even that 2012 does not match that rule, it should help to start with a winter minimum. So yes, I agree that there is a bigger possibility of having an ice-free Arctic, on years like 2015-2017, that the melt season starts with low ice. Specially 2017, that we are starting with the lowest volume on record, according to PIOMAS.
« Last Edit: April 22, 2017, 01:02:59 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.

Steven

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Re: 2017 sea ice area and extent data
« Reply #172 on: April 22, 2017, 02:11:41 PM »
Is there any correlation between winter sea ice volume maxima and summer minima ?

Using data for 1979-2016,  the correlation between detrended maximum volume and detrended minimum volume is 0.648, which is highly statistically significant (p-value: p < 0.001).

However, this is only true for sea ice volume.  For sea ice extent (rather than volume), the correlation between detrended maxima and detrended minima is very weak.

gerontocrat

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Re: 2017 sea ice area and extent data
« Reply #173 on: April 22, 2017, 02:49:04 PM »
Is there any correlation between winter sea ice volume maxima and summer minima ?

Using data for 1979-2016,  the correlation between detrended maximum volume and detrended minimum volume is 0.648, which is highly statistically significant (p-value: p < 0.001).

However, this is only true for sea ice volume.  For sea ice extent (rather than volume), the correlation between detrended maxima and detrended minima is very weak.

Thankyou Steven - bloody marvellous.

And, therefore, is it fair to say that a reduction in winter sea ice maximum volume increases the likelihood of a reduced sea ice volume minimum in the following summer and so on ...... ? (though natural variation, e.g. an unusually warm or unusually cool melting season can overwhelm the signal).

If so, then the April sea ice volume maximum will at least indicate the direction of travel?
Or am I making a cause and effect where none really exists ?

To explain my thought processes, in the risk analyses I have done in many different fields from risk of war, economics, finance, water resources and others, absolute data was often rare. One attempts to identify influences, rank them in +ve and -ve directions and attempt to weight them. From that, take a deep breath and make a forecast and assign probabilities of various future events (and be proved wrong).

"Para a Causa do Povo a Luta Continua!"

AndrewB

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Re: 2017 sea ice area and extent data
« Reply #174 on: April 22, 2017, 03:06:29 PM »
Is there any correlation between winter sea ice volume maxima and summer minima ?

Using data for 1979-2016,  the correlation between detrended maximum volume and detrended minimum volume is 0.648, which is highly statistically significant (p-value: p < 0.001).

However, this is only true for sea ice volume.  For sea ice extent (rather than volume), the correlation between detrended maxima and detrended minima is very weak.

Steven, just curious: what correlation coefficient did you calculate and how?

oren

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Re: 2017 sea ice area and extent data
« Reply #175 on: April 22, 2017, 03:13:14 PM »
gerontocrat, absolutely. This year's extremely low winter volume makes me expect a record summer min volume even with average melt conditions.
« Last Edit: April 22, 2017, 08:02:36 PM by oren »

Steven

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Re: 2017 sea ice area and extent data
« Reply #176 on: April 22, 2017, 06:41:47 PM »
And, therefore, is it fair to say that a reduction in winter sea ice maximum volume increases the likelihood of a reduced sea ice volume minimum in the following summer and so on ...... ? (though natural variation, e.g. an unusually warm or unusually cool melting season can overwhelm the signal).

Yes, that is fair to say.

The 2017 maximum PIOMAS volume should be about 20.8 thousand km3.  For what it's worth, a simple regression analysis then suggests that this gives an 80 percent chance of a record low minimum volume for September 2017.

gerontocrat

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Re: 2017 sea ice area and extent data
« Reply #177 on: April 23, 2017, 03:59:51 PM »
And, therefore, is it fair to say that a reduction in winter sea ice maximum volume increases the likelihood of a reduced sea ice volume minimum in the following summer and so on ...... ? (though natural variation, e.g. an unusually warm or unusually cool melting season can overwhelm the signal).

Yes, that is fair to say.

The 2017 maximum PIOMAS volume should be about 20.8 thousand km3.  For what it's worth, a simple regression analysis then suggests that this gives an 80 percent chance of a record low minimum volume for September 2017.

Thanks again, Steven.
The PIOMAS April analysis should be coming out in about a fortnight. Any chance of you running the correlation and indication for 2017 minimum again when it appears and shoving it onto the PIOMAS thread ?
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Bill Fothergill

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Re: 2017 sea ice area and extent data
« Reply #178 on: April 23, 2017, 08:10:31 PM »
Is there any correlation between winter sea ice volume maxima and summer minima ?


Using data for 1979-2016,  the correlation between detrended maximum volume and detrended minimum volume is 0.648, which is highly statistically significant (p-value: p < 0.001).

However, this is only true for sea ice volume.  For sea ice extent (rather than volume), the correlation between detrended maxima and detrended minima is very weak.


Thank you Steven. That was a concise and meaningful answer to a perfectly reasonable question.

However, an earlier response to Gerontocrat's question was less helpful.
... Sorry to point out the obvious, but there is no need to calculate a statistical correlation between winter sea ice volume maxima and summer minima, because the two are directly related by a simple formula:
summer ice minimum = (previous) winter ice maximum - total spring/summer melt
...


Instead of answering the question as to the existence (or otherwise) of such a correlation, that was simply a descriptive statement of an obvious equality. A similar example of an obvious equality from the world of finance would be...

Closing share price = Opening share price + Change in share price

Although taken from entirely different spheres, these two equality statements share a common weakness: namely that, in the absence of any reliable form of time travel - other than the usual unidirectional 1 second per second familiar to everyone - the predictive skill of each is precisely zero.

As Steven goes on to stress, although there is a strongly positive correlation when the metric is volume, that breaks down when looking at either extent or area. In the summer of 2013, Rob Dekker and myself independently wrote articles on this subject for Neven's Arctic Sea Ice Blog.

http://neven1.typepad.com/blog/2013/06/problematic-predictions.html
http://neven1.typepad.com/blog/2013/07/problematic-predictions-2.html

Bringing that a bit more up to date, and using Excel's CORREL function on the NSIDC monthly values for both Artic Sea Ice extent and area for September 1979 - March 2017...

Correlation between September extent (year X) and March extent (year X+1) = 0.739
Correlation between September area (year X) and March area (year X+1) = 0.678

However, those seemingly meaningful correlations are largely due to the overall downward trend in the dataset(s).

March extent trend = - 42k sq kms/annum
March area trend = - 32k sq kms/annum

September extent trend = - 87k sq kms/annum
September area trend = - 79k sq kms/annum

Once the data has been de-trended (using a simple least-squares linear regression), the output(s) of the CORREL function change to...

Correlation between September extent (year X) and March extent (year X+1) = -0.068
Correlation between September area (year X) and March area (year X+1) = -0.165

As Steven stated, this represents a pretty weak level of correlation - and it actually comes out as being weakly negative.


N.B. As mentioned earlier, during those array comparisons, the average September value of (year X) would be paired with the average March value of (year X+1). The reason for this particular arrangement was because Gerontocrat's original question concerned the correlation if only the freezing season was considered. Had the question pertained to the melting season, then March and September values from the same year would have been compared.

However, it would not really have made much difference, as the de-trended correlations for the March - September melt season are also very weak...

extent = 0.000
area = -0.022

BornFromTheVoid

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Re: 2017 sea ice area and extent data
« Reply #179 on: April 23, 2017, 08:21:22 PM »
Update for the week to April 22nd

The current 5 day trailing average is on 13,587,000km2 while the 1 day extent is at 13,493,000km2.

(All the following data is based on a trailing 5 day average)
The daily anomaly (compared to 81-10) is at -935,000km2, a decrease from -966,000km2 last week. The anomaly compared to the 07, 11 and 12 average is at -515,000km2, an increase from -445,000km2 last week. We're currently 2nd lowest on record, down from lowest last week.



The average daily change over the last 7 days was -32.9k/day, compared to the long term average of -37.3k/day, and the 07, 11 and 12 average of -22.8k/day.
The average long term change over the next week is -40.7k/day, with the 07, 11, and 12 average being -44.2k/day.



The extent loss so far this April is the 14th smallest record. To achieve the largest loss, a drop of at least 130.0k/day is required (more than -157.4k/day with with single day values), while the smallest drop requires a loss of less than 14.4k/day (less than 3.5k/day with single day values) and an average loss requires a drop of 65.7k/day (-71.9k/day with single day values).


gregcharles

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Re: 2017 sea ice area and extent data
« Reply #180 on: April 27, 2017, 08:22:13 PM »
Today is a five year anniversary of being below average. Based on the Charctic Interactive Sea Ice, it's now been five years since arctic sea ice extent was last above the 1981-2010 median.

BornFromTheVoid

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Re: 2017 sea ice area and extent data
« Reply #181 on: May 01, 2017, 11:12:13 AM »
Update for the week to April 29th

The current 5 day trailing average is on 13,587,000km2 while the 1 day extent is at 13,493,000km2.

(All the following data is based on a trailing 5 day average)
The daily anomaly (compared to 81-10) is at -790,000km2, a decrease from -935,000km2 last week. The anomaly compared to the 07, 11 and 12 average is at -346,000km2, a decrease from -515,000km2 last week. We're currently 2nd lowest on record, the same as last week.



The average daily change over the last 7 days was -20.1k/day, compared to the long term average of -40.7k/day, and the 07, 11 and 12 average of -44.2k/day.
The average long term change over the next week is -43.1k/day, with the 07, 11, and 12 average being -45.2k/day.



The extent loss so far this April is the 4th smallest record. To achieve the largest loss, a drop of at least 898.5k/day is required (more than -4,457.1k/day with with single day values), while the smallest drop an increase of at least than 25.5k/day (at least 161.9k/day with single day values) and an average loss requires a drop of 385.2k/day (1,891.0k/day with single day values).


BornFromTheVoid

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Re: 2017 sea ice area and extent data
« Reply #182 on: May 07, 2017, 06:44:32 PM »
Update for the week to May 6th

The current 5 day trailing average is on 13,070,000km2 while the 1 day extent is at 13,079,000km2.

(All the following data is based on a trailing 5 day average)
The daily anomaly (compared to 81-10) is at -736,000km2, a decrease from -790,000km2 last week. The anomaly compared to the 07, 11 and 12 average is at -271,000km2, a decrease from -346,000km2 last week. We're currently 3rd lowest on record, down from 2nd lowest last week.



The average daily change over the last 7 days was -53.9k/day, compared to the long term average of -61.6k/day, and the 07, 11 and 12 average of -64.6k/day.
The average long term change over the next week is -43.3k/day, with the 07, 11, and 12 average being -38.4k/day.



The extent loss so far this May is the 14th smallest record. To achieve the largest loss, a drop of at least 70.9k/day is required (more than -77.3k/day with with single day values), while the smallest loss requires a drop of less than 18.8k/day (less than 20.8k/day with single day values) and an average loss requires a drop of 43.8k/day (48k/day with single day values).



The extent loss in April was the 3rd smallest on record, while the average extent was the 2nd lowest on record.




Wipneus

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Re: 2017 sea ice area and extent data
« Reply #183 on: May 12, 2017, 03:56:31 PM »
Time for an update concerning sea ice area calculated from NSIDC sea ice concentration compared with extent (same as calculated by NSIDC).

While extent is 5th lowest (~690k higher than 2016), area has dropped to #10, more than 1 Million higher than 2016.

Here are the rankings for 11th May:

extent NH
datum: -05-11
2005-05-11 13.119149
2003-05-11 13.056350
2011-05-11 12.968637
2007-05-11 12.940884
2014-05-11 12.876776
2017-05-11 12.830311
2015-05-11 12.757955
2004-05-11 12.709222
2006-05-11 12.709040
2016-05-11 12.143364

area NH
2017-05-11 11.467165
2007-05-11 11.449676
2003-05-11 11.447578
2004-05-11 11.381959
2014-05-11 11.324955
2010-05-11 11.241607
2011-05-11 11.145334
2015-05-11 11.144258
2006-05-11 11.007650
2016-05-11 10.454304

Wipneus

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Re: 2017 sea ice area and extent data
« Reply #184 on: May 12, 2017, 04:06:40 PM »
How is the situation wrt sea ice measured by NSIDC restricted to the Arctic Basin regions?

NSIDC extent has dropped from the 100% ice cover and is among the front runners (well behind 2016).

That can not be said of area, still in the middle of the pack and behind most of the recent (2006 and later) years.

Neven

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Re: 2017 sea ice area and extent data
« Reply #185 on: May 12, 2017, 10:14:39 PM »
Thanks, Wip, that's some great info (as always).
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charles_oil

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Re: 2017 sea ice area and extent data
« Reply #186 on: May 12, 2017, 11:20:51 PM »

So is it that the outlying areas (which will melt out) are holding on, maybe due to the "wacky" weather whereas the key, core area is already declining ?


Jim Williams

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Re: 2017 sea ice area and extent data
« Reply #187 on: May 13, 2017, 12:14:18 AM »

So is it that the outlying areas (which will melt out) are holding on, maybe due to the "wacky" weather whereas the key, core area is already declining ?

Isn't that what I am seeing in the Nares?

Weather isn't that wacky...the cold that used to stay at the pole has to dissipate somewhere.

slow wing

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Re: 2017 sea ice area and extent data
« Reply #188 on: May 13, 2017, 12:45:05 AM »
Thanks Wipneus! I really like your plots restricted to the Arctic Basin regions.

Note the big offset scale - the fractional declines shown in those plots by 11 May are only a couple of percent at most.

2016 has the biggest declines by 11 May. (The purple line on Wipneus' plots.) The reason can be seen from the concentration maps for 13 May (but 11 May for 2017):

https://sites.google.com/site/arcticseaicegraphs/concentration-maps/sic0513

In all the other years, all of the Arctic Basin sea ice is nearly intact through 13 May. In 2016 though, it is seen that the Beaufort Sea had already opened up by a significant amount by 13 May, as shown by the red arrow:



jdallen

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Re: 2017 sea ice area and extent data
« Reply #189 on: May 13, 2017, 06:54:41 AM »
How is the situation wrt sea ice measured by NSIDC restricted to the Arctic Basin regions?

NSIDC extent has dropped from the 100% ice cover and is among the front runners (well behind 2016).

That can not be said of area, still in the middle of the pack and behind most of the recent (2006 and later) years.
For all of that, most of the difference in both extent and area is in three areas:  the Barents sea, Greenland Sea and Baffin Bay.

It will dissappear rapidly.
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BornFromTheVoid

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Re: 2017 sea ice area and extent data
« Reply #190 on: May 15, 2017, 01:44:01 PM »
Update for the week to May 13th

The current 5 day trailing average is on 13,070,000km2 while the 1 day extent is at 13,079,000km2.

(All the following data is based on a trailing 5 day average)
The daily anomaly (compared to 81-10) is at -672,000km2, a decrease from -736,000km2 last week. The anomaly compared to the 07, 11 and 12 average is at -241,000km2, a decrease from -271,000km2 last week. We're currently 5th lowest on record, down from 3rd lowest last week.




The average daily change over the last 7 days was -34.1k/day, compared to the long term average of -43.3k/day, and the 07, 11 and 12 average of -38.4k/day.
The average long term change over the next week is -44.2k/day, with the 07, 11, and 12 average being -47.1k/day.



The extent loss so far this May is the 12th smallest record. To achieve the largest loss, a drop of at least 85.2k/day is required (more than -86.6k/day with single day values), while the smallest loss requires a drop of less than 12.8k/day (less than 5.3k/day with single day values) and an average loss requires a drop of 47.5k/day (44.4k/day with single day values).



Wipneus

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Re: 2017 sea ice area and extent data
« Reply #191 on: May 23, 2017, 03:09:24 PM »
NSIDC extent is 5th lowest place (nearly equal to  2006 at #4).
Area (from NSIDC SIC) only at 9th position, now behind 2012 at #7.

extent NH
datum: -05-22
2007-05-22 12.565060
1995-05-22 12.558821
2014-05-22 12.523640
2010-05-22 12.454524
2011-05-22 12.390777
2017-05-22 12.376212
2006-05-22 12.370576
2004-05-22 12.291722
2015-05-22 12.213506
2016-05-22 11.591323
area NH
2007-05-22 10.731251
2017-05-22 10.723499
2005-05-22 10.699015
2012-05-22 10.679585
2008-05-22 10.666784
2015-05-22 10.520421
2006-05-22 10.410440
2011-05-22 10.399773
2010-05-22 10.388519
2016-05-22 9.860509

Wipneus

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Re: 2017 sea ice area and extent data
« Reply #192 on: May 23, 2017, 03:15:08 PM »
Restricting to the Arctic Basin regions 2017 extent is second behind 2016 relatively far from other years.
Area is less extreme, but still among the lowest recent years.

TerryM

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Re: 2017 sea ice area and extent data
« Reply #193 on: May 23, 2017, 05:27:20 PM »
This is unexpected - can't wait for PIOMAS.
Terry

BornFromTheVoid

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Re: 2017 sea ice area and extent data
« Reply #194 on: May 23, 2017, 09:43:23 PM »
Update for the week to May 20th

The current 5 day trailing average is on 12,543,000km2 while the 1 day extent is at 12,514,000km2.

(All the following data is based on a trailing 5 day average)
The daily anomaly (compared to 81-10) is at -651,000km2, a decrease from -672,000km2 last week. The anomaly compared to the 07, 11 and 12 average is at -200,000km2, a decrease from -241,000km2 last week. We're currently 5th lowest on record, the same as last week.



The average daily change over the last 7 days was -39.7k/day, compared to the long term average of -44.2k/day, and the 07, 11 and 12 average of -47.1k/day.
The average long term change over the next week is -50.0k/day, with the 07, 11, and 12 average being -54.1k/day.



The extent loss so far this May is the 8th smallest record. To achieve the largest loss, a drop of at least 113.2k/day is required (more than -134.9k/day with single day values), while the smallest loss requires an increase of at least 5.3k/day (at least 9.6k/day with single day values) and an average loss requires a drop of 51.5k/day (59.8k/day with single day values).


BornFromTheVoid

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Re: 2017 sea ice area and extent data
« Reply #195 on: May 29, 2017, 12:30:21 PM »
Update for the week to May 28th

The current 5 day trailing average is on 12,278,000km2 while the 1 day extent is at 12,215,000km2.

(All the following data is based on a trailing 5 day average)
The daily anomaly (compared to 81-10) is at -612,000km2, a decrease from -651,000km2 last week. The anomaly compared to the 07, 11 and 12 average is at -126,000km2, a decrease from -200,000km2 last week. We're currently 7th lowest on record, down from 5th lowest last week.



The average daily change over the last 7 days was -37.8k/day, compared to the long term average of -50.0k/day, and the 07, 11 and 12 average of -54.1k/day.
The average long term change over the next week is -51.4k/day, with the 07, 11, and 12 average being -52.5k/day.



The extent loss so far this May is the 7th smallest record. To achieve the largest loss, a drop of at least 244.6k/day is required (more than -457.5k/day with single day values), while the smallest loss requires an increase of at least 80.6k/day (at least 192.8k/day with single day values) and an average loss requires a drop of 75.6k/day (119.6k/day with single day values)



Wipneus

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Re: 2017 sea ice area and extent data
« Reply #196 on: May 29, 2017, 03:06:45 PM »
Area calculated from NSIDC concentration is currently dropping faster than extent. The latest figures (20170528) are now the fifth lowest (but only 68k below #2).
Extent is 6th lowest, 600k below #2.

extent NH
datum: -05-28
2008-05-28 12.316215
1995-05-28 12.298185
2014-05-28 12.222014
2004-05-28 12.208909
2017-05-28 12.155762
2010-05-28 12.114739
2011-05-28 12.104922
2006-05-28 11.999727
2015-05-28 11.840660
2016-05-28 11.265964

area NH
2014-05-28 10.417287
2005-05-28 10.415554
2008-05-28 10.403674
2015-05-28 10.244283
2010-05-28 10.102317
2017-05-28 10.072805
2012-05-28 10.060195
2006-05-28 10.052573
2011-05-28 10.005748
2016-05-28 9.506624

« Last Edit: May 29, 2017, 03:16:05 PM by Wipneus »

Wipneus

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Re: 2017 sea ice area and extent data
« Reply #197 on: May 29, 2017, 03:11:49 PM »
Within the restricted Arctic Basin, extent is still second lowest. Area at #3 and dropping fast, a first sign of surface melting.

Wipneus

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Re: 2017 sea ice area and extent data
« Reply #198 on: May 29, 2017, 04:12:07 PM »
Today's regional changes:
Regional Arctic Sea Ice Extent and Area calculated from NSIDC NASA Team concentration data
Date: 2017-05-28 12:00  Values in 1000 km^2

Extent (value, one day change, anomaly):
   Central Arctic Basin       East Siberian Sea              Laptev Sea
  4456.6   +0.0    +5.4    913.7   +2.5   -17.8    722.9   +7.1    -0.5
               Kara Sea             Barents Sea           Greenland Sea
   872.5   -4.4   -17.7    454.2  -16.4  -182.4    653.9   -3.7   -24.0
Baffin/Newfoundland Bay            St. Lawrence              Hudson Bay
  1018.5  -25.7   +22.9     48.7   -5.5   +12.8   1186.9   -3.2   -15.6
   Canadian Archipelago            Beaufort Sea             Chukchi Sea
   738.2   -0.0    -0.2    475.7   -2.5   -41.6    463.8   -3.1  -115.2
             Bering Sea          Sea of Okhotsk                   Lakes
    19.1   -1.7  -167.5     82.7   +0.1   -70.5    197.4   -7.7   +53.9
          Other regions       Total (ex. lakes)
    48.5   -1.9    -3.2  12155.8  -58.4  -615.0

Area (value, one day change, anomaly):
   Central Arctic Basin       East Siberian Sea              Laptev Sea
  4264.2  -26.8   -21.0    808.2   -8.0   -59.5    615.0  -11.2   -39.0
               Kara Sea             Barents Sea           Greenland Sea
   692.8  -36.3   -69.7    281.0  -10.6  -132.2    480.1   -2.1   +25.1
Baffin/Newfoundland Bay            St. Lawrence              Hudson Bay
   677.0  -24.1   -37.1     14.5   -0.9    +3.4    827.4  -28.6  -137.1
   Canadian Archipelago            Beaufort Sea             Chukchi Sea
   609.0   +2.6   -71.6    363.9   -8.7   -95.6    382.7   -0.2  -132.4
             Bering Sea          Sea of Okhotsk                   Lakes
     8.5   -0.6   -64.2     33.0   +0.3   -38.8    120.3   +1.5   +38.2
          Other regions       Total (ex. lakes)
    15.5   -1.7    -4.3  10072.8 -157.0  -874.0


The attached delta images shows where concentration goes over/below 15% in dark blue/red; else concentration changes over 7% are colored light blue/red.

Wipneus

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Re: 2017 sea ice area and extent data
« Reply #199 on: May 30, 2017, 03:44:25 PM »
Area (calculated from NSIDC sea ice concentration) continues to drop fast. Yesterday I reported a 5th place, today's numbers area the second lowest for the day. It will take a lot more melting to get to the first place.

Ranks:

extent NH
datum: -05-29
2007-05-29 12.295967
1995-05-29 12.295098
2004-05-29 12.228823
2014-05-29 12.194538
2017-05-29 12.106827
2010-05-29 12.052171
2011-05-29 12.044185
2006-05-29 12.012332
2015-05-29 11.792429
2016-05-29 11.209175

area NH
1995-05-29 10.404848
2014-05-29 10.360418
2007-05-29 10.358662
2015-05-29 10.189945
2006-05-29 10.097577
2010-05-29 10.056848
2011-05-29 10.033491
2012-05-29 9.998651
2017-05-29 9.952865
2016-05-29 9.416968
 
Regional Arctic Sea Ice Extent and Area calculated from NSIDC NASA Team concentration data
Date: 2017-05-29 12:00  Values in 1000 km^2

Extent (value, one day change, anomaly):
   Central Arctic Basin       East Siberian Sea              Laptev Sea
  4456.6   +0.0    +4.6    913.7   +0.0   -18.0    722.3   -0.6    -0.5
               Kara Sea             Barents Sea           Greenland Sea
   864.3   -8.2   -26.0    445.4   -8.8  -182.8    653.0   -0.8   -23.2
Baffin/Newfoundland Bay            St. Lawrence              Hudson Bay
   997.6  -20.9   +11.5     22.5  -26.2   -13.9   1184.5   -2.4   -13.0
   Canadian Archipelago            Beaufort Sea             Chukchi Sea
   734.4   -3.8    -4.2    478.8   +3.1   -36.8    461.9   -1.9  -115.8
             Bering Sea          Sea of Okhotsk                   Lakes
    22.0   +2.9  -151.5     90.5   +7.9   -56.9    233.5  +35.6   +91.3
          Other regions       Total (ex. lakes)
    59.4  +10.9    +5.5  12106.8  -48.9  -620.9

Area (value, one day change, anomaly):
   Central Arctic Basin       East Siberian Sea              Laptev Sea
  4245.7  -18.4   -31.6    811.7   +3.5   -55.9    608.6   -6.4   -41.3
               Kara Sea             Barents Sea           Greenland Sea
   647.3  -45.6  -112.7    250.0  -31.0  -156.2    479.5   -0.6   +28.2
Baffin/Newfoundland Bay            St. Lawrence              Hudson Bay
   661.4  -15.6   -44.0      8.2   -6.2    -3.1    815.3  -12.1  -147.4
   Canadian Archipelago            Beaufort Sea             Chukchi Sea
   618.8   +9.9   -60.1    363.8   -0.1   -93.0    377.9   -4.8  -136.2
             Bering Sea          Sea of Okhotsk                   Lakes
     9.2   +0.7   -58.0     35.0   +1.9   -33.6    126.8   +6.5   +45.8
          Other regions       Total (ex. lakes)
    20.5   +5.1    +0.0   9952.9 -119.8  -944.8