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Dharma Rupa

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Re: IJIS
« Reply #4650 on: July 23, 2017, 07:58:16 PM »
...
My current working hypothesis about this can be summarized thus:  once melt retreats past about 75N over all, the system dynanimics change sharply. My thought is, that open water becomes a buffer which more efficiently and evenly redistributes heat.  I think the dynamics of phase change come into play as well, with heat which previously melted ice, taken up by evaporation, which in turn further contributes to increased albedo.  To summarize, we see increasing feedbacks from different mechanisms that don't exist or are retarded at higher levels of ice coverage.  I think they are the only reason we aren't seeing open water at 90N by early August.
Not sure about the rest of your analysis, but I agree that the open water more evenly distributes heat.  The problem is, if this is correct then the ice will more suddenly go from covering large areas to completely disappearing.  Thus, everything points to an Arctic which very suddenly changes -- even if we cannot tell when this will happen.

Ice Shieldz

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Re: IJIS
« Reply #4651 on: July 23, 2017, 10:38:56 PM »
What I've seen is an almost "compressive" feedback behavior, where other forces come into play slowing the melt.

I remember bbr2314 talking this fall and winter about the possible ice-age inducing effects that extra snow would have on the arctic. I dismissed his zeal around the cooling effect it would have - esp. during fall and winter. However, in hindsight the extra snow, and other related negative atmospheric feedbacks, seemed to have slowed melt in 2017 and 2016(more because of clouds, etc).

Have we entered a new phase of the arctic? Cloudy-cool-summers, Stormy-warm-winters. AKA the Wimpy Ice Phase, where sea ice extent hangs on while ice thickness plummets. How long will this phase last?

One thing seems sure to me given the decadal trend of sea ice volume loss, we are rapidly approaching the point when one ice unfriendly winter followed by an ice unfriendly summer will yield a BOE for the Arctic.

In the meantime, perhaps nature might give us a few more years to figure things out before we reach the end of the whip. In other words, ongoing BOEs, a highly-disrupted atmospheric circulation and a planetary energy budget that's running away from us at an unstoppable rate.

Tigertown

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Re: IJIS
« Reply #4652 on: July 23, 2017, 11:05:18 PM »
As far as I am concerned, as long as PIOMAS is dropping, melt is ongoing. Extent is interesting to watch, but is not a melt gauge by no means.

Deeenngee

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Re: IJIS
« Reply #4653 on: July 23, 2017, 11:17:50 PM »
Some chartistic updates.
First, centred 7 day averages of daily extent change. 2017 is showing a charming sinusoidal shape, and is currently bang on the 2007-16 average.

Next, the same thing but with 2012 as well. The scale of the June 2012 extent drop and the GAC drop are plainly visible.

Then, 2017 daily extent change compared with the average extent change for the same day during 2007-16. It's just a different way to look at how the season is progressing.

Finally, the more conventional day by day chart with the historical range and decadal averages.

(I've also done an equivalent minimum chart to the one I posted a few times for the maximum, showing the timing and km2 of previous years. I'll post that around August 1st.)
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Ice Shieldz

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Re: IJIS
« Reply #4654 on: July 23, 2017, 11:23:09 PM »
As far as I am concerned, as long as PIOMAS is dropping, melt is ongoing. Extent is interesting to watch, but is not a melt gauge by no means.
True for me too. My point is that we seem to be revealing a mechanism by which SIE can hang on a little longer than some might think, and there's a vast world of difference (as far as net effects) between having even a thin layer of relatively low SIE and having a BOE.
« Last Edit: July 23, 2017, 11:30:53 PM by Ice Shieldz »

DavidR

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Re: IJIS
« Reply #4655 on: July 24, 2017, 01:48:01 AM »
As far as I am concerned, as long as PIOMAS is dropping, melt is ongoing. Extent is interesting to watch, but is not a melt gauge by no means.
True for me too. My point is that we seem to be revealing a mechanism by which SIE can hang on a little longer than some might think, and there's a vast world of difference (as far as net effects) between having even a thin layer of relatively low SIE and having a BOE.
It is also worth remembering that  2012 had the equal lowest drop (up until 2012, subsequently  2014 was lower) in volume (8.62 K km^3) after July 1st despite its record loss in extent. It was clearly the distribution of that volume that played into the final extent figures. The GAC, in itself, did not cause any significant additional volume loss.  This years distribution must be very similar to 2012 given the July 1st  figures for volume and extent.
« Last Edit: July 24, 2017, 05:17:05 AM by DavidR »
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oren

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Re: IJIS
« Reply #4656 on: July 24, 2017, 02:53:56 AM »
I've been wanting to crunch some numbers, having followed gerontocrat's informative calculations for a while now, to try and correlate between extent loss and low July volume. It is quite difficult as the ice regime has changed over the years (loss of MYI), volume distribution matters a lot, extent depends on dispersion, day of minimum matters a lot, PIOMAS has some error margins, and in addition, the correlations are not very strong.

So I made the attached table, sorry for the lack of annotation, but it takes the years 2010-2016, looking at losses of volume and extent from last known date to day 250 (Sep 7th) and comparing to the average of those years. I did not calculate correlations (though they exist), but instead here are some thoughts on why 2012 was a freak.
2012 on day 203 had a low extent - but 2011 was lower.
2012 to day 250 lost a good volume figure - but 2015 and 2016 lost much more.
2012 had a low volume on day 196 - but 2011 wasn't far behind.
On the other hand, 2012 had a low volume on day 250 - with no other year coming close. And by some miracle, it also produced a freak extent loss.
So maybe current extent isn't such a good predictor, and current volume can't make a strong case, but when absolute volume falls below a threshold, extent crashes?

Speculating: If 2011 had lost an above-average amount of volume in this period, it might have finished as 2012.
If 2016 had entered day 196 with a low volume figure, it might have finished as 2012 or below (as it was area did crash, but extent didn't).
More speculation: the last volume is in the highest latitudes, therefore harder to melt, so having a low volume in July could cause a low loss of volume later. (But a GAC can help bring the volume loss numbers back up.)

My unscientific conclusion - starting with lower volume than 2012, this year needs just an average loss of volume so it might crash in extent. Will an average volume loss happen? I give it 40%. Will this actually crash extent? I think it a serious possibility. So a 20% chance for an extent record seems reasonable.

** Why day 250 - to avoid the effect of early/late minimum, which adds the noise of weather and the distribution of open water latitudes.
Why from 2010 - looking at their volume numbers I believe 2007-2009 were much too different.
« Last Edit: July 24, 2017, 07:50:00 AM by oren »

Rob Dekker

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Re: IJIS
« Reply #4657 on: July 24, 2017, 03:53:09 AM »
The mistake you and others make is the assumption that this year's ice is anything like previous years.  Or that this year's climate is anything like previous years.   Or that atmospheric circulation or ocean currents and temperatures are anything like previous years.

You can crunch numbers all you want, but if circumstances in the past in no way resemble current circumstances, then it's just GIGO.

You can't treat a transforming system as if it's a static one and derive anything useful.

This is somewhat of a "hands-in-the-air", "if-you-don't-know-everything-you-can't-know-anything" type of response.

Reality is that the 'climate' in the Arctic is changing due to climate change, but that doesn't make it GIGO. In predictive methods we use the term predictive 'skill'. Steven can explain this better than I can, but it basically means that your method is BETTER than a prediction done with linear trend.

For example, Andrew Slater's Probabilistic Model has predictive skill at lead times up to
90 days
https://www.arcus.org/files/sio/27252/sio2017_june_slater_etal.pdf

And Dr. Schroeder's method has predictive 'skill' using melt-pond area in spring (May).
http://www.homepages.ed.ac.uk/shs/Climatechange/Arctic%20ice/melt%20pond%20ice%20forecast.pdf

My own model has predictive 'skill' from June to September, and Steven's model has some skill even from May-September.

That does not mean that these models will be right in predicting September extent (in fact they will probably all be wrong) but they will on average be less wrong than simply extrapolating a linear trend. Thus these models are useful, and are NOT GIGO.

Please try to recognize the difference...
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mmghosh

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Re: IJIS
« Reply #4658 on: July 24, 2017, 06:55:03 AM »
Deengee thanks for the excellent and informative charts.

jdallen

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Re: IJIS
« Reply #4659 on: July 24, 2017, 07:52:32 AM »
...
My current working hypothesis about this can be summarized thus:  <snip>
<snip>
Thus, everything points to an Arctic which very suddenly changes -- even if we cannot tell when this will happen.
There is much merit to your observation, Dharma Rupa.  The Arctic has become a very chaotic system, with the potential to tip over into a very different regime very quickly.

I think we need to be tracking other dimensions more closely - sea water heat distribution, albedo, rate of thermal transfer between water and atmosphere, water vapor, total system enthalpy among others - as I think they would give us more insight.  It would be better if we had history for all of those things, but sadly, we do not.  If wishes were horses, beggars would ride.
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jdallen

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Re: IJIS
« Reply #4660 on: July 24, 2017, 08:03:10 AM »
What I've seen is an almost "compressive" feedback behavior, where other forces come into play slowing the melt.

I remember bbr2314 talking this fall and winter about the possible ice-age inducing effects that extra snow would have on the arctic. I dismissed his zeal around the cooling effect it would have - esp. during fall and winter. However, in hindsight the extra snow, and other related negative atmospheric feedbacks, seemed to have slowed melt in 2017 and 2016(more because of clouds, etc).

Have we entered a new phase of the arctic? Cloudy-cool-summers, Stormy-warm-winters. AKA the Wimpy Ice Phase, where sea ice extent hangs on while ice thickness plummets. How long will this phase last?

One thing seems sure to me given the decadal trend of sea ice volume loss, we are rapidly approaching the point when one ice unfriendly winter followed by an ice unfriendly summer will yield a BOE for the Arctic.

In the meantime, perhaps nature might give us a few more years to figure things out before we reach the end of the whip. In other words, ongoing BOEs, a highly-disrupted atmospheric circulation and a planetary energy budget that's running away from us at an unstoppable rate.
Snow cover is a highly volatile and vulnerable negative feedback sadly.  Unlike ice which is realtively durable vs. things like air temperature and rain, snow can vanish in a matter of hours completely changing a major system dynamic (albedo) literally overnight.  As such, it is much more at the mercy of chance, which over the last 5 years following 2012 has managed to work more in our favor.

The energy budget and total enthalpy in the system is The Thing.  In a sort of inverse Pit and the Pendulum, that heat raises the target for each swing of the annual solar "Pendulum".  Eventually, however much the Arctic manage to suck in its belly, it will not be able to avoid getting cut lethally; at least, not without some sort of stupendous intervention.

We're not going to see it coming, as our current metrics like IJIS extent can't "see" that heat, and the nature of the ice and the system are changing in ways that we can't quantify.  Right now, I think anyone making a definitive prediction of the year of the ice's disappearence is throwing darts blindfolded.  We simply don't have all of the data we need to predict that.
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Espen

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Re: IJIS
« Reply #4661 on: July 24, 2017, 08:40:54 AM »
IJIS:

7,049,346 km2(July 23, 2017)down 9,685 km2 and 4th lowest measured for the date.
Have a ice day!

Rob Dekker

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Re: IJIS
« Reply #4662 on: July 24, 2017, 09:45:09 AM »
2017 was overdue for a bit of a stall.
The question now is : Will this reduction in melt rate persist or not.

Most indicators suggest it will, and 2017 should start to follow the 2013 or 2014 lines going forward.
However, the (PIOMAS) volume numbers suggest that melting will progress faster than normal, and potentially rival 2012.

I guess all we can do is wait. And see.
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Re: IJIS
« Reply #4663 on: July 24, 2017, 12:42:28 PM »
IJIS:

7,049,346 km2(July 23, 2017)down 9,685 km2 and 4th lowest measured for the date.

FWFW, that marks the smallest July one-day decrease IJIS has recorded in all the years from 2003 to now (there was a very small increase on the 30th in 2013). The 2003-2016 average for today has been -84k.

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Re: IJIS
« Reply #4664 on: July 24, 2017, 01:41:39 PM »
Yesterday's 41K drop was OK with me (it brought the predict-o-matic back up to 99.96% accuracy for its June 10th prediction) but this sub-10K drop is pretty crazy.

The July 30, 2013 extent increase that Jim mentions is literally the only other time there has been such a small daily change in extent during the two-plus months from June 20 to Aug 21.  That's 901 days, with yesterday ranking 900th of 901.

It's statistically equivalent to a 184K century break, but on the low side instead of the high side.




Tigertown

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Re: IJIS
« Reply #4665 on: July 24, 2017, 01:57:14 PM »
 Ned W
Quote
this sub-10K drop is pretty crazy.
Some thin ice popped up in the Kara and some more next to Svalbard. The ice had melted there recently, but the water was yet to be disturbed enough to dispatch the cool fresh meltwater. The new ice will not last, but it temporarily offset losses mathematically. Also, some other ice in places like the Fram did not melt out quite completely and experienced some minor dispersion.

Cid_Yama

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Re: IJIS
« Reply #4666 on: July 24, 2017, 02:27:36 PM »
The mistake you and others make is the assumption that this year's ice is anything like previous years.  Or that this year's climate is anything like previous years.   Or that atmospheric circulation or ocean currents and temperatures are anything like previous years.

You can crunch numbers all you want, but if circumstances in the past in no way resemble current circumstances, then it's just GIGO.

You can't treat a transforming system as if it's a static one and derive anything useful.

We have variations on this post LITERALLY EVERY YEAR.  One year they will be right, much like a stopped clock. When that year comes, don't delude yourself that you deserve credit for your foresight.

Where did THAT come from?  You may be fighting some personal demon, but it's not me.
Personal attacks are out of place here, especially when they are based on nothing but your own issues.   
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Cid_Yama

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Re: IJIS
« Reply #4667 on: July 24, 2017, 02:50:02 PM »
Quote
Here I will tackle systems and, more specifically, I want to draw attention to the differences between static and dynamic systems.  This is often under-emphasised when thinking about whole systems.

How we make sense of, or cognitively frame, a problem is fundamental to how we then solve it.  Often we don’t realise how we’re framing something because this happens in our subconscious and, understandably, we spend little or no time thinking about how we are thinking about something.

What do you think when you read or hear the word “system”?  I’ll share mine: when I close my eyes and consider what I mean, I have a vague notion – a picture if you like – of an interconnected whole.  Call it a network of lots of parts, with a complicated set of inter-connections.

Few of the words used to describe what I imagine imply any sort of dynamism.  In fact, the word “picture” leans me much more toward a static interpretation.

Is this a problem?  Well, yes and no because it depends on the context and how and why I use the word.  If I am concerned with a broadly unchanging system then my personal definition of this word isn’t terrible.  But problems arise when we use words or framings that sit awkwardly with the real world we are trying to grapple with e.g. when the system I am considering changes (e.g. the weather) and I frame it as if it were static.

Moreover, I would argue that quite a few people think of systems in a similarly static way.  In fact, some of my colleagues in the complex systems arena deliberately avoid using the word system because they interpret it in a narrow, static way, which jars with the inherently dynamic nature of complex systems.
link


An excellent paper on how students in Earth and Atmospheric Sciences have difficulty in conceptualizing complex systems.

Students’ Understanding of Complex Dynamic Systems


« Last Edit: July 24, 2017, 03:05:28 PM by Cid_Yama »
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Re: IJIS
« Reply #4668 on: July 24, 2017, 03:06:29 PM »
The mistake you and others make is the assumption that this year's ice is anything like previous years.  Or that this year's climate is anything like previous years.   Or that atmospheric circulation or ocean currents and temperatures are anything like previous years.

You can crunch numbers all you want, but if circumstances in the past in no way resemble current circumstances, then it's just GIGO.

You can't treat a transforming system as if it's a static one and derive anything useful.

We have variations on this post LITERALLY EVERY YEAR.  One year they will be right, much like a stopped clock. When that year comes, don't delude yourself that you deserve credit for your foresight.

Where did THAT come from?  You may be fighting some personal demon, but it's not me.
Personal attacks are out of place here, especially when they are based on nothing but your own issues.   

You told other people that they're wrong.  Peter Ellis told you that you're wrong.  His language was perhaps slightly more pointed than yours, but not that much.

He is right that every year people say "conditions this year are totally different from any other previous year" and then most of the time the season proceeds more or less as it did the year before and the year before that. 

We're about six weeks away from the minimum.  Over the past six weeks, extent has decreased by 3.51 million km2.  For the previous decade, the average was 3.59.  Seems pretty typical to me.

Cid_Yama

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Re: IJIS
« Reply #4669 on: July 24, 2017, 03:47:04 PM »
Pointing out mistakes in analysis assumptions, or misframing, in other words methodology, is not a personal attack.

Seems there is something more ideological going on with some of you, that adds an emotional element to your posts.   
« Last Edit: July 24, 2017, 03:54:01 PM by Cid_Yama »
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Neven

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Re: IJIS
« Reply #4670 on: July 24, 2017, 05:04:30 PM »
If you want to take this elsewhere, please, do.
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Feeltheburn

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Re: IJIS
« Reply #4671 on: July 24, 2017, 05:13:56 PM »
IJIS:

7,049,346 km2(July 23, 2017)down 9,685 km2 and 4th lowest measured for the date.

FWFW, that marks the smallest July one-day decrease IJIS has recorded in all the years from 2003 to now (there was a very small increase on the 30th in 2013). The 2003-2016 average for today has been -84k.

These variations are probably just statistical noise and don't mean that much. The average over a few days is more accurate. On NSIDC for example, the ice dropped hugely from 7/18 - 7/21, then increased on 7/22 and 7/23. I doubt any of the numbers are very accurate, but the average is more accurate.
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Ned W

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Re: IJIS
« Reply #4672 on: July 24, 2017, 06:46:11 PM »
The smallness of yesterday's decrease is interesting as a curiosity, in the same way that a century-break drop of 183K would be interesting.

I don't think anyone is suggesting that it's representative of what the rest of the melt season will look like.

FWIW, here are the IJIS/JAXA extent forecasts for the next three weeks from the predict-o-matic:

1 August: 6.2988814 million km2
8 August: 5.7605581
15 August: 5.2863288

I post them here so we can all laugh when they turn out wrong.

 :)

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Re: IJIS
« Reply #4673 on: July 24, 2017, 07:39:41 PM »
2017 was overdue for a bit of a stall.
The question now is : Will this reduction in melt rate persist or not.
Please stop conflating extent reduction rate with melt rate.
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Re: IJIS
« Reply #4674 on: July 24, 2017, 07:45:53 PM »
It is worth noting the contrast of this extent loss blip with the large area decrease (according to AMSR2 -- see Wip's home brew thread), including a large band across the leading edge of the Chukchi and Beaufort.
The Permian–Triassic extinction event, a.k.a. the Great Dying, occurred about 250 million years ago and is the most severe known extinction event. Up to 96% of all marine species and 70% of terrestrial vertebrate species became extinct; it is also the only known mass extinction of insects.

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Re: IJIS
« Reply #4675 on: July 24, 2017, 11:07:41 PM »
Hi guys I don't think a -10 k makes such a big difference honestly. If we think in terms of average decrease, I guess the last 10 days have seen an average decrease of about 90 k which is not surprising at all if we consider the synoptic configuration and the average temperatures on the Arctic. Temperatures have been in line with the average or below for the last 3 months almost.

As I stressed in previous posts, it's difficult to get better synoptic charts than the current ones at this moment of the melting season: plenty of clouds, dispersion and not too deep LPs are extremely beneficial in terms of ice preservation. In the next days we will see a more intense intake of warm winds from Pacific Ocean which will be bringing more clouds and precipitations as well.

Difficult to make forecasts at this point of the season honestly. But so far the synoptic analysis has worked quite well. In my very humble opinion, close as we are to the end of July, I believe the momentum for a major melting has probably been lost. But it's nothing more than an barely-educated guess...Just need to wait and see, there's not so much more to wait actually...

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Re: IJIS
« Reply #4676 on: July 24, 2017, 11:54:15 PM »
My own predict o matic 3.7m has had a bad couple of days.

I need average drops of 70 to 80k to be close now.

Just my first year though.

Ill learn.

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Re: IJIS
« Reply #4677 on: July 25, 2017, 08:26:12 AM »
IJIS:

7,004,682 km2(July 24, 2017)down 44,664 km2 and 5th lowest measured for the date.
Have a ice day!

Rob Dekker

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Re: IJIS
« Reply #4678 on: July 25, 2017, 08:42:48 AM »
Please stop conflating extent reduction rate with melt rate.
Fair enough.
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Re: IJIS
« Reply #4679 on: July 25, 2017, 08:54:47 AM »
Given that the decrease is picking up again in the AMSR2 data set, it should be possible to squeeze a couple of century breaks out of JAXA until the end of the month, especially after that ridiculous 10K drop.  :)
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Re: IJIS
« Reply #4680 on: July 25, 2017, 12:32:04 PM »
In 2012 before the GAC...

A silly warm super torch crushed the Pacific side of the CAB.

With already unprecedented  ssts warmth in place.

A weak ridge bringing a long fetch Southerly wind flow directly off NA I'll n addition to strong sun and many century old land record temps along the Arctic shore.

This event crippling the Western CAB.

Major melt crushed MYI that started the season 3M+ and vanished by August 10th.

This is forgotten or very overlooked leading up to the major wind event.

You can look back and see the incredible 850-925mb temps along the nose of a mid level ridge running with a off shore perpendicular to the NA coast during peak land warmth.

There were days around 90F creeping within miles of the Arctic ocean.

Of course there was likely localized cold frontss along the water front.

But with ssts running at FUCKING 20C at the mouth of that River I can't remember the name...

Down to a balmy 5-8C near the ice pack.

Best believe the low level Southerly flow wasn't totally buttfucked by near ice cold pool driven cold fronts.

And the fact that the hundreds of miles of open ocean near surface warmth had no impediment into the ice pack and had mostly sunny skies to reinforce the lost heat to melting along the pherifery of the ice pack.

Our bouys that were still transmitting data were typically in the thickest ice.

Dampening the entire picture where thinner ice was probably sitting in 1-3C soup water just melting at incredible pace.

This kind of Southerly flow is simply rare.

Combined with peak land warmth
Record land warmth
Epic ssts
Epic open ocean
Highly anomolous mid level ridging bringing sunny skies.


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and a dirty pistol that love to crew hop
my TEC 9 Imma call T-Pain
my 3-8 snub Imma call Lil Wayne
machine gun named Missy so loud
it go e-e-e-e-ow e-e-e-e-e-e-blaow

Ned W

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Re: IJIS
« Reply #4681 on: July 25, 2017, 01:12:52 PM »
My own predict o matic 3.7m has had a bad couple of days.

I need average drops of 70 to 80k to be close now.
Unlikely, maybe, but still possible!

Quote
Just my first year though.

Ill learn.
That's why we're all here...

gerontocrat

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Re: IJIS
« Reply #4682 on: July 25, 2017, 01:41:11 PM »
2017 was overdue for a bit of a stall.
The question now is : Will this reduction in melt rate persist or not.
Please stop conflating extent reduction rate with melt rate.

I thought to myself - what is the definition of "conflate"? So I looked it up (see below).
Obviously in the short-term compaction and dispersion can cause variation in various measures. This is especially true in the Antarctic where fierce winds switching from off-shore to on-shore and vice versa cause huge differences in daily sea-ice extent change. But in the end extent reduction can only happen if melting happens. To conflate extent reduction with melting is therefore OK, with the usual caveats. So I am not going to change the wording in my table.

ps:- Having worked in public finance all over the world I noticed that the first casualty of the search for ideological purity by both the extreme left and the extreme right is often a sense of humour.

Meanwhile, three days of low extent reduction means that extent reduction so far this year (to 24 July) is 6 percent less than the average of the last 10 years. Being so late in the season, this also makes the additional melt required for a second lowest extent minimum 10% above that 10 year average.
I admit I am confused given that DMI 80N+ and cci-reanalyzer  + all the images on other threads  supported a continuation or increase in melt.
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dnem

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Re: IJIS
« Reply #4683 on: July 25, 2017, 02:04:36 PM »
Please stop conflating extent reduction rate with melt rate.

[/quote]
But in the end extent reduction can only happen if melting happens. To conflate extent reduction with melting is therefore OK, with the usual caveats. So I am not going to change the wording in my table.
[/quote]

Can't winds compact sea ice causing a reduction in extent with no melting?

gerontocrat

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Re: IJIS
« Reply #4684 on: July 25, 2017, 02:20:41 PM »
Please stop conflating extent reduction rate with melt rate.

But in the end extent reduction can only happen if melting happens. To conflate extent reduction with melting is therefore OK, with the usual caveats. So I am not going to change the wording in my table.
[/quote]

Can't winds compact sea ice causing a reduction in extent with no melting?
[/quote]

Yes, it can in the short-term. As I wrote "Obviously in the short-term compaction and dispersion can cause variation in various measures. This is especially true in the Antarctic where fierce winds switching from off-shore to on-shore and vice versa cause huge differences in daily sea-ice extent change. But in the end extent reduction can only happen if melting happens. "
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"And that's all I'm going to say about that". Forrest Gump
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greatdying2

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Re: IJIS
« Reply #4685 on: July 25, 2017, 03:16:20 PM »
Please stop conflating extent reduction rate with melt rate.
So I am not going to change the wording in my table.
ps:- Having worked in public finance all over the world I noticed that the first casualty of the search for ideological purity by both the extreme left and the extreme right is often a sense of humour.
(Sorry Neven, but I feel this demands a response.)

Gerontocrat, either you are purposely misleading people and using rhetorical tricks in a weak attempt to distract and discredit, or you actually don't grasp the clear difference between extent and melt, which speaks volumes. (Pun intended -- do you like my sense of humour?)  ::)

If the latter is truly the case, let me put it in terms someone from finance might more simply grasp: Using extent to measure melt is like using stock prices to measure GDP. Or perhaps better, using stock prices to measure or predict economic health. (You'd be in for some big surprises!)


« Last Edit: July 25, 2017, 03:49:02 PM by greatdying2 »
The Permian–Triassic extinction event, a.k.a. the Great Dying, occurred about 250 million years ago and is the most severe known extinction event. Up to 96% of all marine species and 70% of terrestrial vertebrate species became extinct; it is also the only known mass extinction of insects.

oren

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Re: IJIS
« Reply #4686 on: July 25, 2017, 06:28:50 PM »
Volume loss is the definition and measure of melt. But volume is not measured, just modelled, and is not published daily unfortunately.
Area is a good physical proxy for melt. Area is measured, but suffers from inaccuracies and is not widely published.
Extent is a proxy for area. It is measured more accurately and is widely followed.
Easy to see why extent equals melt in everyday speak, though it's not technically correct. Even the freezing thread is switched to the melting thread according to the extent maximum (March), not the volume maximum (May). So I would suggest to skip the technicalities and just keep on with the very interesting melting season.

Juan C. García

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Re: IJIS
« Reply #4687 on: July 25, 2017, 06:44:38 PM »
Given that the decrease is picking up again in the AMSR2 data set, it should be possible to squeeze a couple of century breaks out of JAXA until the end of the month, especially after that ridiculous 10K drop.  :)

I agree. IJIS uses an average of latest two days (day:N & day:N-1) So, as an example, if the average is only -10k, there could be the values N-1: -50k and N: 30k.
On the following day -45k average: N: 30k and N+1: -120k. So, we already have a day that is under -100k. Lets wait to see what we will have on day N+2, but I see a chance that we will have a century break today, on the 2-day average.
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: IJIS
« Reply #4688 on: July 26, 2017, 06:10:46 AM »
Small drop of only 60.9k km2. So, I didn´t guess it well...  8)
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.

Tensor

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Re: IJIS
« Reply #4689 on: July 26, 2017, 07:44:33 AM »
Small drop of only 60.9k km2. So, I didn´t guess it well...  8)

It's OK Juan, we did have a century drop, it just occurred over two days... ;)
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epiphyte

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Re: IJIS
« Reply #4690 on: July 26, 2017, 09:17:25 AM »

One year they will be right, much like a stopped clock. When that year comes, don't delude yourself that you deserve credit for your foresight.


I find myself driven to ask, which is worse; speculating that this might be the year, on the grounds that things look different from anything that we have ever had to cope with, or insisting that the old measures must be the best because they have always worked in the past?

We all know it's coming. No-one knows when. But when it does, it will be because the old metrics are no longer relevant. So IMO yes, they deserve credit for understanding that, when others don't.



Espen

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Re: IJIS
« Reply #4691 on: July 26, 2017, 09:55:03 AM »
IJIS:

6,943,764 km2
(July 25, 2017)down 60,918 km2 and 5th lowest measured for the date.
Have a ice day!

oren

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Re: IJIS
« Reply #4692 on: July 26, 2017, 09:59:29 AM »
IJIS is laughing at PIOMAS...  ???

crandles

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Re: IJIS
« Reply #4693 on: July 26, 2017, 11:18:50 AM »

One year they will be right, much like a stopped clock. When that year comes, don't delude yourself that you deserve credit for your foresight.


I find myself driven to ask, which is worse; speculating that this might be the year, on the grounds that things look different from anything that we have ever had to cope with, or insisting that the old measures must be the best because they have always worked in the past?

We all know it's coming. No-one knows when. But when it does, it will be because the old metrics are no longer relevant. So IMO yes, they deserve credit for understanding that, when others don't.

Who has the best forecasting ability? This depends on
1)how long it takes before a BOE happens. Guessing zero for many years in a row before being correct is not a good record. Guessing zero for just one year without it happening leaves a lot of skill needed the next year to catch up in forecast skill.

2) Whether the old metrics predict it when it does happen. While it might happen suddenly without other metrics predicting it, this is by no means assured. So there is no guarantee of much of a catch up in skill when it does happen.

Insisting the old measures are perfect would be wrong, but suggesting that the old measures have better skill (could be more wrong in one particular year but generally taken over several years a little better skill) seems quite easily defensible to me.

Dharma Rupa

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Re: IJIS
« Reply #4694 on: July 26, 2017, 02:17:19 PM »
Insisting the old measures are perfect would be wrong, but suggesting that the old measures have better skill (could be more wrong in one particular year but generally taken over several years a little better skill) seems quite easily defensible to me.

The problem is that the old measures are going to go from having fair skill to having no skill at all.

Ned W

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Re: IJIS
« Reply #4695 on: July 26, 2017, 06:02:13 PM »
IJIS is laughing at PIOMAS...  ???

FWIW, I just wrote up a long post addressing this volume-vs-extent conundrum, here:

https://forum.arctic-sea-ice.net/index.php/topic,2121.msg122431/topicseen.html#msg122431

Espen

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Re: IJIS
« Reply #4696 on: July 27, 2017, 11:03:57 AM »
IJIS:

6,858,612 km2(July 26, 2017)down 85,152 km2 and 5th lowest measured for the date.
Have a ice day!

Shared Humanity

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Re: IJIS
« Reply #4697 on: July 27, 2017, 03:15:43 PM »
Volume loss is the definition and measure of melt. But volume is not measured, just modelled, and is not published daily unfortunately.
Area is a good physical proxy for melt. Area is measured, but suffers from inaccuracies and is not widely published.
Extent is a proxy for area. It is measured more accurately and is widely followed.
Easy to see why extent equals melt in everyday speak, though it's not technically correct. Even the freezing thread is switched to the melting thread according to the extent maximum (March), not the volume maximum (May). So I would suggest to skip the technicalities and just keep on with the very interesting melting season.

Thank you. I get tired of conversations questioning the usefulness of the metrics available. Each of these measures provide us with some insight into what is happening.

greatdying2

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Re: IJIS
« Reply #4698 on: July 27, 2017, 04:29:13 PM »
Because of the incredible hypocrisy and short-sightedness here, I am permanently closing this thread, which in any case I find to be the least useful active thread. The IJIS numbers are available on Wipneus' graphs, along with far more useful context.
The Permian–Triassic extinction event, a.k.a. the Great Dying, occurred about 250 million years ago and is the most severe known extinction event. Up to 96% of all marine species and 70% of terrestrial vertebrate species became extinct; it is also the only known mass extinction of insects.

Neven

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Re: IJIS
« Reply #4699 on: July 27, 2017, 08:25:23 PM »
Because of the incredible hypocrisy and short-sightedness here, I am permanently closing this thread, which in any case I find to be the least useful active thread. The IJIS numbers are available on Wipneus' graphs, along with far more useful context.

I'm fed up with this nonsense, and so I had to ban greatdying2 and wish him all the best. It's not something I like to do, but I want the ASIF to be a pleasant place. If people see that as conservative groupthink, etc, so be it.

End of message.
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