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Nightvid Cole

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Re: The 2015 melting season
« Reply #450 on: April 03, 2015, 06:29:07 PM »
Well, opinions differ, of course, but facts say otherwise. Feel free to read up on the long–plateau hypothesis and the correlation with extreme melt seasons. In any case, I think this year we've got all the right players onboard. We'll see in June whether I'm right or not.

No, we'll see in September whether you're right or not.

viddaloo

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Re: The 2015 melting season
« Reply #451 on: April 03, 2015, 11:56:04 PM »
Good point. We'll see in September, and April, May, June, July, August & October. It'll be fun!
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Siffy

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Re: The 2015 melting season
« Reply #452 on: April 04, 2015, 12:35:32 PM »
I suspect this is an error, but for a brief moment I ended up doing a spit take.


Meirion

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Re: The 2015 melting season
« Reply #453 on: April 04, 2015, 04:47:02 PM »
Amazing how little protection from old ice the Pole has from a Kara/Laptev direction melt this year  there is almost no cover in 85º North quadrants facing Russia.

w.aari.ru/odata/_d0015.php?lang=1&mod=0&yy=2015

This time last year almost totally protected in 85º quadrants

http://www.aari.ru/odata/_d0015.php?lang=1&mod=0&yy=2014


OSweetMrMath

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Re: The 2015 melting season
« Reply #454 on: April 04, 2015, 10:13:25 PM »
Last month the PIOMAS volume update was relatively late. This month it is up already, so I can give updates on my ice prediction models.

As I discussed last month, my prediction for the monthly Arctic sea ice extent as measured by the NSIDC in March was for 14.7 million sq km, with a 95% confidence interval of 14.2 million - 15.3 million sq km. By the time this prediction was posted, there was already strong evidence that the actual extent would be at the low end of the range. The reported extent was 14.39 million sq km, so the prediction was somewhat high. This was the largest prediction error in this direction during the last 11 months of predictions. (The actual extent in August 2014 was 0.6 million sq km above my prediction, a substantially larger error in the other direction.) As a result, the monthly extent for March was slightly below the monthly extent for February of 14.43 million sq km. Although the maximum typically occurs in March, it is not unheard for the maximum to occur in February.

Looking forward, the current prediction for the April extent is 13.9 million sq km, with a 95% confidence interval of 13.4 - 14.4 million sq km. Given the current behavior of the ice, I do not have a sense of whether the lower or the upper part of the range is more likely. (At this point, there is likely interest in predictions for the extent in September. I am holding off on computing the prediction until we have the April data. However, I can say that because last year's September extent was 5.28 million sq km, which is relatively high compared to recent years, the predicted extent for September is also likely to be relatively high.)

Last month's prediction for the ice volume as estimated by PIOMAS was 23.7 thousand cubic km. As with the extent, the actual volume was below the prediction, at 23.206 thousand cubic km, barely within my confidence interval. This balances my prediction from last month, when the actual volume was above my prediction. I have been making monthly predictions of volume for 11 months, and this is the first time the actual volume was substantially below my prediction.

The prediction for the maximum volume in April is now substantially lower than it was last month, at 23.9 thousand cubic km, with a 95% confidence interval of 23.4 - 24.4 thousand cubic km.  (I will provide a prediction for the September minimum after this year's maximum has occurred.)

Nightvid Cole

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Re: The 2015 melting season
« Reply #455 on: April 05, 2015, 07:17:41 PM »
Last month the PIOMAS volume update was relatively late. This month it is up already, so I can give updates on my ice prediction models.

As I discussed last month, my prediction for the monthly Arctic sea ice extent as measured by the NSIDC in March was for 14.7 million sq km, with a 95% confidence interval of 14.2 million - 15.3 million sq km. By the time this prediction was posted, there was already strong evidence that the actual extent would be at the low end of the range. The reported extent was 14.39 million sq km, so the prediction was somewhat high. This was the largest prediction error in this direction during the last 11 months of predictions. (The actual extent in August 2014 was 0.6 million sq km above my prediction, a substantially larger error in the other direction.) As a result, the monthly extent for March was slightly below the monthly extent for February of 14.43 million sq km. Although the maximum typically occurs in March, it is not unheard for the maximum to occur in February.

Looking forward, the current prediction for the April extent is 13.9 million sq km, with a 95% confidence interval of 13.4 - 14.4 million sq km. Given the current behavior of the ice, I do not have a sense of whether the lower or the upper part of the range is more likely. (At this point, there is likely interest in predictions for the extent in September. I am holding off on computing the prediction until we have the April data. However, I can say that because last year's September extent was 5.28 million sq km, which is relatively high compared to recent years, the predicted extent for September is also likely to be relatively high.)

Last month's prediction for the ice volume as estimated by PIOMAS was 23.7 thousand cubic km. As with the extent, the actual volume was below the prediction, at 23.206 thousand cubic km, barely within my confidence interval. This balances my prediction from last month, when the actual volume was above my prediction. I have been making monthly predictions of volume for 11 months, and this is the first time the actual volume was substantially below my prediction.

The prediction for the maximum volume in April is now substantially lower than it was last month, at 23.9 thousand cubic km, with a 95% confidence interval of 23.4 - 24.4 thousand cubic km.  (I will provide a prediction for the September minimum after this year's maximum has occurred.)

Why are you using April extent to guess September extent? They are totally unrelated.

OSweetMrMath

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Re: The 2015 melting season
« Reply #456 on: April 05, 2015, 11:30:59 PM »
Why are you using April extent to guess September extent? They are totally unrelated.

They are not totally unrelated, but my prediction for April would have to be off by half a million sq km to have a measurable effect on my prediction for September. The real reasons I haven't computed the September prediction yet include:
1. I'm lazy.
2. The NSIDC revised all of the extent data recently, and I haven't updated my predictions to use the new data yet. (But I don't expect this to have any noticeable effect on my predictions.)
3. Once the data for April is available, I will have been running this prediction for a full year, and I plan to run some tests to evaluate my performance and revise my prediction methods if necessary. I don't currently expect to make any major revisions.
4. I'm lazy.

In general, the single most important input into my predictions is the extent one year previously. Last year's April extent was 14.14 million sq km, and my prediction for this April at that time was 14.11 million sq km. This prediction was updated every month based on each month's data, but was more or less unchanged, reaching a maximum of 14.18 based on December's data. The year over year change in extent is highly correlated at a range of 1 or 2 months, and the fact that March was so much lower than predicted has pushed my prediction for April to 13.89.

The correlation at a distance of 5 months is very slight, so I could have run a prediction for September 2015 based on the data from September 2014, and my prediction would have been more or less unchanged since then. Instead, I'm holding off and will generate the prediction after the April data is available.

DavidR

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Re: The 2015 melting season
« Reply #457 on: April 06, 2015, 09:34:14 AM »
Why are you using April extent to guess September extent? They are totally unrelated.
NightVid
The trend relationship between Maximum and Minimum extent is  Min =  1.503* Max -17.396  in M km^2.  This gives us a prediction for this year  of 2.555 M km^2.  Why do you consider them unrelated?
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OSweetMrMath

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Re: The 2015 melting season
« Reply #458 on: April 06, 2015, 03:23:43 PM »
DavidR,

The short answer is because you haven't detrended the data. I'll have a longer answer later, but it will take a bit of time to do the calculations and make some graphs, and I'm not going to have time to do it until later today.

Nightvid Cole

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Re: The 2015 melting season
« Reply #459 on: April 06, 2015, 04:28:33 PM »
Why are you using April extent to guess September extent? They are totally unrelated.
NightVid
The trend relationship between Maximum and Minimum extent is  Min =  1.503* Max -17.396  in M km^2.  This gives us a prediction for this year  of 2.555 M km^2.  Why do you consider them unrelated?

Because the correlation of the detrended data is not significant at the P < .05 level.

plinius

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Re: The 2015 melting season
« Reply #460 on: April 06, 2015, 05:51:19 PM »
I suspect DavidR would like to take a refreshment on omitted variable biases, proxy variables and correlation by time-dependence. Some more humorous blog on this:
https://lgsquirrel.wordpress.com/2014/05/26/where-babies-come-from/

With compliments from www.duckduckgo.com (google doesn't provide easy links anymore to reap the last independence in the internet from us)

OSweetMrMath

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Re: The 2015 melting season
« Reply #461 on: April 06, 2015, 07:56:17 PM »
Okay, here's the longer answer on why the April extent is not correlated with the September extent. This conversation started with April extent and September extent, and then DavidR started talking about the maximum and minimum (not sure if you mean daily or monthly). I'm going to split the difference and talk about March monthly extent and September monthly extent. All of my numbers come from the NSIDC (different sources will have different numbers, but will have similar results).

It (incorrectly) appears that there is a relationship between the March extent and the September extent. After all, in early years in the data, the March extent is large and the September extent is also large. In more recent years, the March extent is small and the September extent is small. So it's a reasonable first step to assume that the March extent predicts the September extent. Let's analyze this, then show that this conclusion is not correct.

We can test this by building a linear model. Sure enough, the equation we get is
Sept = 1.531 * March - 17.315. (all units are million sq km)
(My numbers are close to DavidR's numbers, but not the same. I assume the difference is because he is using the daily maximum and minimum, and I'm using the monthly numbers.) We have a nice linear relationship. If we want to test whether the relationship is statistically significant, we should check the p-value. The p-value reported by R for this linear regression is 10^-6. p-values close to zero indicate significance, so March extent, considered alone, is a statistically significant predictor of September extent.

Going further, using the March value of 14.39, the predicted September extent is 4.72. (I don't know how DavidR computed 2.555. Either he is not computing the NSIDC extent, or there was a computation error.) However, the standard error is 0.7673, which means that the 95% prediction interval is 3.04 - 6.40. This prediction interval is so wide as to be almost useless. (Phrased another way, this prediction interval is saying that the September extent this year is highly likely to be lower than the September extent in 2001, but it could plausibly be higher than the extent any year since then.)

So let's go back to the original observation. We observed that the extent was high in early years and was lower more recently. So maybe we should perform regression on both the year and March extent. Numbering the years with 1979 = 1 for convenience, we get
Sept = -0.088 * March - 0.090 * year + 9.412
Notice that not only is the coefficient on the March extent much smaller, but it's actually changed sign. This means that when we use the year as a predictor, as the March extent decreases, the September extent actually increases. The general declining trend in September extent is due to the year, not the March extent.

We should perform a statistical analysis for significance. The p-value for March extent is 0.809. This is about as large as a p-value can get. The clear conclusion is that after controlling for the year, the March extent is not a statistically significant predictor of September extent.

Using this linear model to predict the September extent this year, we get 4.80. But now the standard error is smaller, at 0.57, so the 95% confidence interval for the prediction is 3.54 - 6.06. That's still not very good, but it's an improvement over what we had before.

The conclusion is that first, we need to include the year when we do any analysis of sea ice extent. Second, if we are correctly using the year, March extent is not related to September extent. (Or more generally, the annual minimum is not related to the annual maximum.)

A couple of follow up points. First, when using earlier values in a time series to predict later values in the same series, detrending the data is essential. Adding the year as a covariate in the linear regression does not correctly detrend the data, but it shows the role that the year plays, so I considered it good enough for demonstration purposes.

Second, I haven't mention R-squared values at all. This is deliberate. R-squared is the wrong statistic to examine if you are trying to demonstrate statistically significant correlations. The correct statistic is a p-value, computed from either a t-statistic or an F-statistic.

Neven

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Re: The 2015 melting season
« Reply #462 on: April 06, 2015, 11:04:47 PM »
I suspect DavidR would like to take a refreshment on omitted variable biases, proxy variables and correlation by time-dependence. Some more humorous blog on this:
https://lgsquirrel.wordpress.com/2014/05/26/where-babies-come-from/

No need for sarcasm. Or perhaps do some work first.  ::)
Il faut comparer, comparer, comparer, et cultiver notre jardin

DavidR

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Re: The 2015 melting season
« Reply #463 on: April 07, 2015, 03:17:31 AM »
(I don't know how DavidR computed 2.555. Either he is not computing the NSIDC extent, or there was a computation error.)
oops simple matter of using the CT Area max rather than the NSIDC Extent Max. As to the other difference I  am using the NSIDC 5 day extent average.

I  think your argument about no correlation may hold for the decline in extent, but not for the minimum. If you detrend the data then your minimum is a proxy for the loss.  There is no doubt that the confidence interval is wide but the range is 2M km^2 lower than the range in 1979 when the maximum was 2M km^2 higher
Toto, I've a feeling we're not in Kansas anymore

DavidR

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Re: The 2015 melting season
« Reply #464 on: April 07, 2015, 03:26:43 AM »
I suspect DavidR would like to take a refreshment on omitted variable biases, proxy variables and correlation by time-dependence. Some more humorous blog on this:
https://lgsquirrel.wordpress.com/2014/05/26/where-babies-come-from/

No need for sarcasm. Or perhaps do some work first.  ::)
Statistics is rarely a refreshment, however that was an amusing article. The simple truth is that  correlation does not prove causation, neither does it prove a lack of causation. 

It has been suggested that the cause behind the chocolate correlation is that chocolate consumption is an indicator of wealth and that wealthy countries are more likely to produce nobel laureates.
Toto, I've a feeling we're not in Kansas anymore

viddaloo

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Re: The 2015 melting season
« Reply #465 on: April 07, 2015, 08:49:44 AM »
Total Week 14 melt: 103% more than 2011 = 231427 km².





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seaicesailor

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Re: The 2015 melting season
« Reply #466 on: April 07, 2015, 02:45:19 PM »
El Niño is growing very fast.

http://goo.gl/Lg5cLz

Fast enough to affect Sep extent? I have read it takes at least one year to be felt but SSTs are sky-rocketting and it comes preceded by the weak 2014 Niño too...

jdallen

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Re: The 2015 melting season
« Reply #467 on: April 07, 2015, 04:16:47 PM »
El Niño is growing very fast.

http://goo.gl/Lg5cLz

Fast enough to affect Sep extent? I have read it takes at least one year to be felt but SSTs are sky-rocketting and it comes preceded by the weak 2014 Niño too...
Aimed further north as well, seems.  The "cone" of anomalies look to be tipped north about 20 degrees or so.
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themgt

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Re: The 2015 melting season
« Reply #468 on: April 07, 2015, 05:36:12 PM »
Total Week 14 melt: 103% more than 2011 = 231427 km².

Your graph shows the day of the week, but what dates do those represent? A given date doesn't fall on the same day of the week in 2011 and 2015.

viddaloo

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Re: The 2015 melting season
« Reply #469 on: April 07, 2015, 07:14:29 PM »
Total Week 14 melt: 103% more than 2011 = 231427 km².

Your graph shows the day of the week, but what dates do those represent? A given date doesn't fall on the same day of the week in 2011 and 2015.
That is correct, themgt, the weekdays may end up on any date of the month because 365/366 is not a product of 7, which is the number of days in a regular week. If current year is 2015, the Monday in week 15 will be on the 6th of April, and so on and so forth. This leaves ample room for confusion, of course, this being the Arctic Sea Ice Forum, when the 6th of April in the comparison year was *NOT* on a Monday. But it's still Monday in this year, the year all of us live and post in. If in doubt, think Monday of this week of this year. I guess I could set the weekdays to correspond with 2011 instead, but I fear that would maybe be even more confusing. Glad you asked.
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Lord M Vader

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Re: The 2015 melting season
« Reply #470 on: April 07, 2015, 07:32:14 PM »
Hi guys!

Did some fun calculating with the IJIS numbers thanks to Espen who showed me where the IJIS numbers can be found..

From April 6 to April 30 the melting during the years 2003-2014 have been in the range of 0,72-1,27 million km2. The lowest values are  roughly from 2009 (-0,72), 2005 (-0,73) and 2007 (-0,78) while the highest are from 2003-2004 with -1,25 and -1,27 million km2.

These numbers indicates that the SIE number at April 30 most likely will be the lowest on record for the date. Only if we end up with a very slow melting like 2009 and 2005 we won't have the lowest SIE on record for April 30.

//LMV

seaicesailor

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Re: The 2015 melting season
« Reply #471 on: April 07, 2015, 08:30:33 PM »
Will the Northwest Passage open up this year? HYCOM seems to show that thick multi-year ice is detaching from the entrance  right now

http://goo.gl/Ip2srj

jdallen

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Re: The 2015 melting season
« Reply #472 on: April 07, 2015, 08:47:19 PM »
 That's the Gyre at work. Not good news for the MYI caught in it.  Too soon to predict an open NW passage.
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viddaloo

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Re: The 2015 melting season
« Reply #473 on: April 07, 2015, 09:22:04 PM »
Icelook apr7: Average extent 4th lowest in 32 days, average volume will be 6th in 37 days, and p1k (Piomas minus 1000) will be 3rd in 8 months. The forecast certainly changed dramatically since last week: The difficult 10.28 million km² annual average extent line was crossed on Apr4, and the current weekly delta at 5917 km²/week could take us below 10.27 by Apr16, while the graph points to Apr13. By the end of April we could go below 10.24 by the graph, or past the 10.26 line with the current weekly delta. Currently, the forecast says we'll be lower than 2008 and 4th lowest by May 9th. Average volume is considerably more uncertain, but p1k could go lower than 2013 and be 3rd lowest around Dec9.


[chart faq]
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OSweetMrMath

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Re: The 2015 melting season
« Reply #474 on: April 08, 2015, 12:27:29 AM »
I  think your argument about no correlation may hold for the decline in extent, but not for the minimum. If you detrend the data then your minimum is a proxy for the loss.  There is no doubt that the confidence interval is wide but the range is 2M km^2 lower than the range in 1979 when the maximum was 2M km^2 higher

I think you misunderstand me. Of course it's obvious that in in 1979, the March extent was 16.45 and the September extent was 7.20, while in 2014, the March extent was 14.76 and the September extent was 5.28. In this sense, the March extent and the September extent are correlated because the March extent fell about 2 million sq km during this period and the September extent also fell about 2 million sq km.

In math,
Sept = 1.531 * March - 17.315

What I am saying is that there is a better way of thinking about this relationship. The better way is the March extent depends on the year, and the September extent also depends on the year.

In math,
Mar = -0.040 * Year + 16.204
Sept = -0.087 * Year + 7.980

The two values are only correlated with each other because they are both individually correlated with the year. It turns out, as I have shown in my previous post, that if you use the year to determine the extent in September, knowing the March extent gives you no additional information about the September extent.

This is what "detrending" the data means. Establish the relationship between the data and the year first, and then look for other relationships in the data. This is the standard way to analyze time series, because it gives better results in basically all possible ways. (In this case, the prediction for September extent based on the year alone is more accurate (on average) than the prediction for September extent based on the March extent.)

Based on your post, it sounds like you are interpreting "detrend" to mean throwing away the data about the trend. That's not what I mean. The idea is to remove the trend so it's possible to understand the relationships between the data. Once those relationships are known, use the data about the trend and about the relationships between the data to predict future values for the data.

In this case, after the trend is removed, there is no relationship between the March data and the September data. The September extent is determined only by the trend, not by the March extent.

plinius

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Re: The 2015 melting season
« Reply #475 on: April 08, 2015, 12:36:02 AM »
Thanks, that has made my lengthy answer obsolete. I'd also point out that it may be necessary to _simultaneously_ fit the different impact factors. I.e. you detrend the maximum values and then fit the equation:
minVal = constant + a_1 * maxVal + a_2*time + a_3*time^2 + epsilon
where epsilon are the residuals to be minimized, a_n and constant are the fitting coefficients. Standard software can do this automatically, e.g. gnuplot with it's fit function. Those also provide direct calculation of errors/uncertainties, which are important.

jdallen

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Re: The 2015 melting season
« Reply #476 on: April 08, 2015, 07:21:37 AM »
Portents

Someone a week or so ago was saying that a huge bloom of heat was going to move across eastern europe into the lowlands leading up to the Kara and Laptev.

It seems they may have been right.

Now, the GFS is showing heat absolutely obliterating snow cover across millions of square KM of Siberia and Eastern Russia, almost all the way to the coast.

The GFS is also reporting a huge bloom of heat across the region from NE Greenland -> Svalbard->Franz Josef->Nova Zemlya, of at least 10C, ranging up to nearly 20C above normal.  In sort, most of the region will be close to or slightly above freezing.

The albedo drop will be huge.  Does anyone have a sense of precedent here?  Is this that much earlier a drop in snow cover than usual?  If it does occur, it also implies a huge burst of meltwater down the drainages to the Kara, Laptev (and eventually) the ESS, to be followed by more heat blowing off of the continent.

I'm keen to hear other folks' impression of what effect this may have on the early melt.

This space for Rent.

crandles

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Re: The 2015 melting season
« Reply #477 on: April 08, 2015, 01:26:47 PM »

day 97 2015


day 87 2015

So far this "heat 'anomaly' wave" seems to have brought more snow. But maybe it is thin and about to be obliterated?

viddaloo

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Re: The 2015 melting season
« Reply #478 on: April 08, 2015, 01:52:50 PM »
IJIS:

13,409,765 km2(April 7, 2015)down 36,123 km2 from previous and lowest measured for the date.

Estimated Week 15 melt: 36% more than 2011.


[chart faq]

After Week 15 (Week 12–15 total estimate): 45764 km² *less* melt than 2011
Week 14: 117210 km² more melt than 2011
Week 13: 122361 km² more melt than 2011
Week 12: 289745 km² *less* melt than 2011
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BornFromTheVoid

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Re: The 2015 melting season
« Reply #479 on: April 08, 2015, 04:14:31 PM »
The current 1 day NSIDC extent for day 97 (Apr 7), at 13.999, is the earliest on record to dip below 14 million km2.
The previous earliest was day 99 in 2006.
I recently joined the twitter thing, where I post more analysis, pics and animations: @Icy_Samuel

jdallen

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Re: The 2015 melting season
« Reply #480 on: April 08, 2015, 04:55:32 PM »
So far this "heat 'anomaly' wave" seems to have brought more snow. But maybe it is thin and about to be obliterated?
So the correct interpretation would be... Nothing unusual?  I'm wondering what the typical coverage would be for mid April across sub-arctic Russia and Siberia just east of the Urals.

If snow cover is thin, it could also suggest less drainage and heat transfer.
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crandles

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Re: The 2015 melting season
« Reply #481 on: April 08, 2015, 05:19:55 PM »
So far this "heat 'anomaly' wave" seems to have brought more snow. But maybe it is thin and about to be obliterated?
So the correct interpretation would be... Nothing unusual?  I'm wondering what the typical coverage would be for mid April across sub-arctic Russia and Siberia just east of the Urals.

If snow cover is thin, it could also suggest less drainage and heat transfer.

I don't think I explained well.




Suggest things are not normal with Alaska and Europe particularly low.

There was a huge positive heat anomaly that brought mild temperatures meaning 0 to -10C with winds from south which is quite conducive to snow fall, southerly winds having been warmer and therefore carrying moisture which has to be lost as they cool down.

i.e. I was saying the concentration on heat anomaly might be missing important aspects that brought snow and made the situation more normal rather than making the lack of snow worse.

Having pointed this out I didn't want to be seen to be saying the forecast you presented was going to be wrong. The new snow cover may well be thin and disappear again quickly as indicated by above maps.

>"I'm wondering what the typical coverage would be for mid April across sub-arctic Russia and Siberia just east of the Urals."
Do Rutgers and other maps I linked help answer this?
eg
http://climate.rutgers.edu/snowcover/chart_daily.php?ui_year=2014&ui_day=107&ui_set=1

Rubikscube

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Re: The 2015 melting season
« Reply #482 on: April 08, 2015, 05:49:42 PM »
I would be careful about trusting those snow cover forecasts too much. Predicting how much snow that is going to melt is a difficult exercise and I suspect there is quite some uncertainty range in those forecast maps. It will be interesting to see how reliable this new cci feature turns out to be.

BornFromTheVoid

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Re: The 2015 melting season
« Reply #483 on: April 08, 2015, 09:39:03 PM »
The AMO in March was the most negative since April 2009.

We haven't had a -ve AMO melt season since 1996 (the 4th highest and last +7 million km2 minimum), so it might be worth monitoring...
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Re: The 2015 melting season
« Reply #484 on: April 08, 2015, 10:14:56 PM »
Crandles - thank you, and the link is helpful. 

Progressing forward, it does imply the melt accross the region mentioned may in fact be several weeks ahead of schedule.
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jdallen

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Re: The 2015 melting season
« Reply #485 on: April 08, 2015, 10:46:27 PM »
The AMO in March was the most negative since April 2009.

We haven't had a -ve AMO melt season since 1996 (the 4th highest and last +7 million km2 minimum), so it might be worth monitoring...
Definitely a wild card.  It may not affect the current year, but may signal slowed melt.  I wonder what the correlations might be with the late 70s, 80s and early 90s melts?
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viddaloo

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Re: The 2015 melting season
« Reply #486 on: April 09, 2015, 07:11:20 AM »
IJIS:

13,387,030 km2(April 8, 2015)down 22,735 km2 from previous.
 2nd lowest for the date (2006 -27,236 km2)
Estimated Week 15 melt: 39% more than 2011.


[chart faq]

After Week 15 (Week 12–15 total estimate): 36916 km² *less* melt than 2011
Week 14: 110128 km² more melt than 2011
Week 13: 129443 km² more melt than 2011
Week 12: 289745 km² *less* melt than 2011

37 k km² less melt than 2011 by September 10th would imply a seasonal melt of 10 million km² and an ice extent of 3.9 m km² in September. A minimum that low would secure 2015 the 2nd position — after 2012 but before 2007 & 2011.
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jdallen

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Re: The 2015 melting season
« Reply #487 on: April 09, 2015, 09:15:35 AM »
The AMO in March was the most negative since April 2009.

We haven't had a -ve AMO melt season since 1996 (the 4th highest and last +7 million km2 minimum), so it might be worth monitoring...
I just spent a few hours pondering AMO changes between 1979-2013 as compared to PIOMAS annual volume loss and NSIDC extent loss.

If there's a relationship, I'm not seeing it.  My crude ability is probably part of the problem, but normalizing the values against one another just to see where they might move in conjunction - I'm not seeing it.  At least, I'm not seeing anything which appears to suggest a correlation with some underlying force.

Timing and scale probably comes into play; AMO while trending in one direction or another, look volatile enough that even within a strong trend in one direction, there are points at which it swings briefly the opposite direction.  When those happen would be important, as specific timing would cause the temperature change to be more or less likely to act as a throttle or amplifier of heat transfer.

Deeper ponderage obviously required.
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Re: The 2015 melting season
« Reply #488 on: April 09, 2015, 02:25:49 PM »
The -tive AMO imho is being caused by increased flow through the archipelago/nares /fram, together with greenland meltwater, all gathering due to it's energetic state on the eastern seaboard. It's 'trying' to head west [and down] but in the pushme pullyou of the ocean spreads south to chesapeake where it's forced out into the atlantic with the GS. After a lot of turbulence the more or less opposite 'inclinations' of the two  streams equalise into a slower cooler NAD. If my hunch about arctic ice being less dense than it was [more snow] the flow will increase through the season.

viddaloo

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Re: The 2015 melting season
« Reply #489 on: April 10, 2015, 04:06:11 PM »
IJIS:

13,415,661 km2(April 9, 2015)up 28,631 km2 from previous and 2nd lowest for the date.
Estimated Week 15 melt: 3% more than 2011.


[chart faq]

After Week 15 (Week 12–15 total estimate): 81160 km² *less* melt than 2011
Week 14: 110128 km² more melt than 2011
Week 13: 129443 km² more melt than 2011
Week 12: 289745 km² *less* melt than 2011

81 k km² less melt than 2011 by Sep 10 would imply a seasonal melt of 10 million km² and an ice extent of 3.9 m km² in September. A minimum that low would secure 2015 the 2nd position — after 2012 but before 2007 & 2011.
« Last Edit: April 10, 2015, 08:37:40 PM by viddaloo »
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Jim Hunt

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Re: The 2015 melting season
« Reply #490 on: April 13, 2015, 12:50:31 PM »
Hamburg AMSR2 has burst back to life whilst the CCI Arctic view seems to have ceased to function. Nonetheless, the current anomalously high temperatures from Kara to the Pole seem to be having some effect:

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Re: The 2015 melting season
« Reply #491 on: April 13, 2015, 06:03:57 PM »
Hamburg AMSR2 has burst back to life whilst the CCI Arctic view seems to have ceased to function. Nonetheless, the current anomalously high temperatures from Kara to the Pole seem to be having some effect:

Concur on both, but would differ slightly in timing.  I've been following the temperature anomalies over the Kara/New Siberian Islands/Franz Joseph/Svalbard; the high temperatures have been around for weeks.  I think the weakness we see in your lower image is the consumation of that - weeks of "heat" interfering with thickening and strengthening of the pack, further undermined by increased Fram flow.

That GFS continues to show heat being pumped into that part of the Arctic, with large swaths of the pack at near zero, does not bode well.  The folk at Barneo may find their stay cut short yet again.
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Re: The 2015 melting season
« Reply #492 on: April 13, 2015, 09:20:14 PM »
the long range EPS and GFES suggest a dipole anomaly by day 10




viddaloo

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Re: The 2015 melting season
« Reply #493 on: April 13, 2015, 09:47:37 PM »
Total Week 15 melt: 62% less than 2011.


[chart faq]

After Week 15 (Week 12–15 total): 130104 km² less melt than 2011
Week 15: 79930 km² less melt than 2011
Week 14: 110128 km² more melt than 2011
Week 13: 129443 km² more melt than 2011
Week 12: 289745 km² less melt than 2011

130 k km² less melt than 2011 by Sep 10 would imply a seasonal melt of 9.9 million km² and an ice extent of 4 m km² in September. A minimum that low would secure 2015 the 2nd position — after 2012 but before 2007 & 2011.



Judging from the above plot, the key to a record–breaking sea ice minimum is getting a Summer Melt at least a million km² bigger than the previous Winter Freeze. This happens in 2007 and 2012 and they're both the lowest at the time at minimum. For 2015 quite a bit more than a million is needed: 1.7 million, to be exact. The required Summer Melt is thus 10.8 million.
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Re: The 2015 melting season
« Reply #494 on: April 13, 2015, 10:32:09 PM »
the long range EPS and GFES suggest a dipole anomaly by day 10
That's a Very long stretch, but if it sets up, would combine warm southerly flow from Eastern Europe into the arctic with strong outflow through the Fram strait.

That would suggest pretty favorable melt conditions across the Kara and Barents, and outflow of ice through the Fram which would permit more leads to show up just as insolation across the region starts to ramp up seriously.

The only defense the ice would have left is cloud cover.

It will be interesting to see if that dipole evolves.
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Neven

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Re: The 2015 melting season
« Reply #495 on: April 13, 2015, 10:38:55 PM »
Hamburg AMSR2 has burst back to life whilst the CCI Arctic view seems to have ceased to function. Nonetheless, the current anomalously high temperatures from Kara to the Pole seem to be having some effect:

Thanks for those images, Jim. I'm going to be looking at the ice with more focus in about a week or so, as I'm planning on starting writing ASI updates come (what may in) May.
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BornFromTheVoid

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Re: The 2015 melting season
« Reply #496 on: April 13, 2015, 11:18:06 PM »
the long range EPS and GFES suggest a dipole anomaly by day 10





The 12z operational runs are in agreement, maintaining the dipole in the 8-10 day range.



Looks like the period around 5 days out is key, as a strong ridge gets thrown over the CAA from the NE Pacific. It's a case of whether the high pressure can become established or if this will just be a brief occurrence.
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Re: The 2015 melting season
« Reply #497 on: April 14, 2015, 01:42:20 PM »
The CCI Arctic view is back in action. A reminder that impressive anomalies don't necessarily mean the temperature is above freezing!

ITP 83 is now up and running in the NPEO 2015 buoy "farm". It reports that the current temperature at  89.5131° N, 20.3019° W is -17.25 °C. The field notes state that it's sat on an ice floe which is currently 1.8 m thick
« Last Edit: April 14, 2015, 01:56:50 PM by Jim Hunt »
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Re: The 2015 melting season
« Reply #498 on: April 14, 2015, 02:12:11 PM »
A reminder that impressive anomalies don't necessarily mean the temperature is above freezing!

Hmm, correct me if I'm wrong but you wouldn't really expect to see the temperatures rise much above that regardless whilst there is enough ice to act as a heatsink and cause a temperature inversion would you?

You'd expect the air around the ice to stay at around 0c unless there is a lot of mixing going on right?

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Re: The 2015 melting season
« Reply #499 on: April 14, 2015, 02:32:07 PM »
 That temperature is only at 2 metres, so isn't that around the temperature of the top of the ice as  well?

  If I'm understanding correctly, there is no reason for the top of the ice to be at 0 degrees. Around -2 degrees is the temperature of the bottom of the ice that is in contact with water. The top of the ice is in contact with the air and so sets the air temperature. Would the temperature of the top of the ice at this time of year mainly be determined by the boundary conditions of thermal long wave radiation into a cold sky and a thermal gradient to the bottom of the ice at -2 degrees, with the rate of heat flow upwards determined by the ice's thermal conductivity? The air itself has little thermal mass density and so won't much affect the temperature at the top of the ice - it's more the other way around, with the ice temperature mainly setting the air temperature.

  Is that how it is?