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Author Topic: Arctic Refreeze Discussion: 2014/2015  (Read 164624 times)

OSweetMrMath

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Re: Arctic Refreeze Discussion: 2014/2015
« Reply #350 on: March 11, 2015, 11:48:10 PM »
I've been holding off on an update on my predictions for the NSIDC extent and PIOMAS volume until the PIOMAS volume numbers for February were posted. Well, this update is now very late, and the PIOMAS monthly volume still hasn't been posted, but Wipneus calculated it as 21.5 thousand cubic km based on the gridded monthly data, so I'm running with that. UPDATE: When I checked the monthly file earlier, it had not been updated. I just poked it again and the February value is 21.456. I've recomputed my predictions, and there have been slight changes due to rounding.

Last month's prediction for the NSIDC monthly extent for February was 14.4 million sq km. The reported value was 14.43 million sq km, so my prediction was accurate to rounding. The interesting thing here is the daily behavior of the ice extent, which started falling in mid February and has continued to fall through March. Because my time series model only uses the monthly data, my prediction for March assumes the extent would increase through March, as it would in a more typical year. This means that my prediction for March is unchanged at 14.7 million sq km, with a 95% confidence interval of 14.2 - 15.3 million sq km. There is still some chance that the extent will increase enough in the next two weeks so the March extent will fall inside my confidence interval, but next month is still likely to result in one of my largest prediction errors of the last year.

I've been waiting for the PIOMAS data to see if the monthly value for the volume would reflect the recent extent loss even if the monthly value for the extent did not. I anticipated a possible reverse of last summer, where the PIOMAS volume was well above my prediction in July, but the NSIDC extent followed my prediction in July and then was above my prediction in August. This possibility was complicated by the fact that extent peaks in February or March, but volume continues to grow until April.

As it turns out, a break in the growth rate for the volume is visible in the daily data, although the volume is continuing to increase. On the other hand, the monthly volume is actually above my prediction. My predicted value was 21.1 thousand cubic km, and the reported value is 21.456 thousand cubic km. The prediction error is larger than I would like, but not so large as to be exceptional.

I have updated my prediction for the maximum volume in April to 24.7 thousand cubic km, with a 95% Confidence Interval of 23.7 - 25.6 thousand cubic km. The change in growth in the daily PIOMAS data in late February implies that this prediction maybe somewhat high, so I would not be surprised if the volume ends up at the low end of this range.
« Last Edit: March 12, 2015, 01:12:50 AM by OSweetMrMath »

Neven

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Re: Arctic Refreeze Discussion: 2014/2015
« Reply #351 on: March 11, 2015, 11:51:31 PM »
PIOMAS has been updated, OSMM, all the way up to March 8th.
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viddaloo

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Re: Arctic Refreeze Discussion: 2014/2015
« Reply #352 on: March 11, 2015, 11:57:57 PM »
PIOMAS has been updated, OSMM, all the way up to March 8th.

That's probably the day before they started their script. Meaning it has been running for two three days straight before it spat out (among other things) 36 daily volume numbers. My advice would be to look into their code to rewrite possible unnecessary loops and other inefficient code, ideally so it can run every day and present volume numbers (total and regional) before lunchtime.

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« Last Edit: March 12, 2015, 12:44:46 AM by viddaloo »
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seaicesailor

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Re: Arctic Refreeze Discussion: 2014/2015
« Reply #353 on: March 12, 2015, 12:28:53 AM »
PIOMAS has been updated, OSMM, all the way up to March 8th.

(...)

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OSweetMrMath

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Re: Arctic Refreeze Discussion: 2014/2015
« Reply #354 on: March 12, 2015, 01:09:59 AM »
PIOMAS has been updated, OSMM, all the way up to March 8th.

Thanks. When I checked earlier, the monthly file still had not been updated. I've made small corrections to my previous post based on the correct number.

I realized that I had intended to mention that my post last month provoked some discussion of the maximum extent for the year, with DavidR supporting 14.7 million square km as the daily maximum for the year, rather than the March monthly average as I was predicting. Based on subsequent events, it seems we were both wrong, but I was more wrong than him.

BornFromTheVoid

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Re: Arctic Refreeze Discussion: 2014/2015
« Reply #355 on: March 13, 2015, 11:20:35 AM »
I won't be calling a maximum yet. The latest ECM suggests a gradual increase in area and extent for the next week.

During the next day or 2, conditions remain ideal for further ice growth in the Baffin sea, perhaps setting the highest area coverage since 2008. The Bering sea has below average temps in the west and close to average in the east, which may allow for a small increase.
Meanwhile, mainly westerly winds an average/slight above average remain over the Barents/Kara region, so little change there or perhaps a slight drop.
Overall, a continued slight increase in area and extent could be expected.





Out to 3-4 days, Baffin sea continues to see cold north westerlies, which could result in further increases. The Bering sea sees a return to weak northerlies and generally average to slightly below average temps. While this generally wouldn't do much, given how low the sea ice currently is there, the forecast conditions will probably cause a continued increase in coverage.
The Barents/Kara region sees further strong westerly winds with well above average temps, so some slight decreases could be seen in this regions.
Overall, I think slight increases Arctic-wide ice coverage during this time.





Days 4-5 sees a considerable change.
Mixed conditions over the Baffin Sea should see things level off there and perhaps drop back a little. In the Bering sea, while temps remain close to or slightly below average, moderate northerly winds take hold which could help to spread ice south and increase area and extent coverage. Similarly, over the Barents and Kara sea's northerly winds take hold and become strong. With the ice being so mobile this winter, we will likely see a ice spreading out and down from the central Arctic, increasing area and extent here.
Overall, there could be moderate increases during this time.





Out to 7 days, the conditions remain favourable for extent and area increases. Northerlies (albeit light) continue in the Bering sea which could result in a slow increase, while Barents/Kara see cooler air and northerlies continuing giving a moderate increase.
Nowhere else should see much change, perhaps a small drop in Baffin. There is warmer air about, such as up near north west Greenland, but that's not enough to cause melt this early in the year.
Overall, continued increases are likely during this time.





While I doubt we'll see increases as dramatic as last year, I wouldn't go calling a maximum just yet. Last year saw about 500k increase in area around this time. I wouldn't be surprised if we put on 250k during the next week this year, which would challenge the previous max set in February.
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Neven

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Re: Arctic Refreeze Discussion: 2014/2015
« Reply #356 on: March 13, 2015, 02:55:08 PM »
Days 4-5 sees a considerable change.
Mixed conditions over the Baffin Sea should see things level off there and perhaps drop back a little. In the Bering sea, while temps remain close to or slightly below average, moderate northerly winds take hold which could help to spread ice south and increase area and extent coverage. Similarly, over the Barents and Kara sea's northerly winds take hold and become strong. With the ice being so mobile this winter, we will likely see a ice spreading out and down from the central Arctic, increasing area and extent here.
Overall, there could be moderate increases during this time.





Yes, that's the one. If this forecast comes about, things will get exciting!
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Re: Arctic Refreeze Discussion: 2014/2015
« Reply #357 on: March 13, 2015, 08:50:42 PM »
Also keep in mind the sea of Okhotsk.  While the charts show a little warmer than average conditions for the week keep in mind that the ice there is currently about 150k below previous record lowest max, so even average temps could sea some growth there.
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DavidR

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Re: Arctic Refreeze Discussion: 2014/2015
« Reply #358 on: March 19, 2015, 07:46:03 AM »
Also keep in mind the sea of Okhotsk.  While the charts show a little warmer than average conditions for the week keep in mind that the ice there is currently about 150k below previous record lowest max, so even average temps could sea some growth there.
Although there appears to be quite a bit of ice increase in the Bering Sea, looking at the satellite  images from EOSDIS I  am wondering if all we are seeing is a lot of ice being spread out over warmer waters where it will melt faster than if it stayed huddled together in the north.

There seems to  be a lot of rapid melt at the edges as well as large areas of open water appearing near the coastline.  This suggests that when the winds switch to southerly  there may not be a lot of ice to blow back to the coast.
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Tor Bejnar

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Re: Arctic Refreeze Discussion: 2014/2015
« Reply #359 on: March 19, 2015, 02:03:45 PM »
The  Arctic HYCOM site  projects a great deal of under 10% concentration ice spreading out east of Labrador, Canada in the next week.   Of course, this 'under 10% concentration ice' would, if realized, count as naught, but if it became '15% concentration ice', another story.  I wonder if this projection is ice spreading out or new growth or a mixture of the two; the HYCOM wind forecasts are not clear to me.
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Re: Arctic Refreeze Discussion: 2014/2015
« Reply #360 on: March 20, 2015, 04:17:57 PM »
I think  we  can put this Arctic refreeze thread to bed.  :-\

BornFromTheVoid

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Re: Arctic Refreeze Discussion: 2014/2015
« Reply #361 on: March 20, 2015, 05:00:08 PM »
I'd say wait until Monday, if we're not within 100k of the Feb max, then it's safe to call it.
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Michael Hauber

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Re: Arctic Refreeze Discussion: 2014/2015
« Reply #362 on: March 22, 2015, 03:23:38 AM »
Just let the thread die from lack of posting.  And if by some fluke, or collective error of reasoning we get a renewed max beyond expectation someone can post about it no problem.

Or we can keep the thread going a little while longer arguing about whether to kill it or not :P
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Neven

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Re: Arctic Refreeze Discussion: 2014/2015
« Reply #363 on: March 22, 2015, 10:13:56 AM »
I've already un-stickied it.
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Re: Arctic Refreeze Discussion: 2014/2015
« Reply #364 on: March 22, 2015, 07:56:30 PM »
I've already un-stickied it.

Hmmmmmm, does this qualify as you calling the max?  :P
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Re: Arctic Refreeze Discussion: 2014/2015
« Reply #365 on: March 22, 2015, 08:11:20 PM »
I think it's perfectly safe to call the max now. The northerlies through into the Barents and Bering sea's didn't have the expected impact, especially as Hudson Bay lost some coverage at the same time. I wouldn't be surprised to see further increases over the next few days, just not enough to challenge the max.
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Neven

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Re: Arctic Refreeze Discussion: 2014/2015
« Reply #366 on: March 22, 2015, 08:56:59 PM »
Hmmmmmm, does this qualify as you calling the max?  :P

Don't tell anyone.  ;)

The northerlies through into the Barents and Bering sea's didn't have the expected impact, especially as Hudson Bay lost some coverage at the same time.

I had expected more of that combination of cold and winds, especially given the low extent, otherwise I wouldn't have written that blog post. Maybe an effect will become more noticeable in the next 2-3 days, but like you say, most probably not enough to challenge the prelim max.
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Neven

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Re: Arctic Refreeze Discussion: 2014/2015
« Reply #367 on: March 23, 2015, 09:27:16 AM »
I had expected more of that combination of cold and winds, especially given the low extent, otherwise I wouldn't have written that blog post. Maybe an effect will become more noticeable in the next 2-3 days, but like you say, most probably not enough to challenge the prelim max.

There it is, 100K in two days on JAXA SIE. Difference with the prelim max is now 137K.
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BornFromTheVoid

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Re: Arctic Refreeze Discussion: 2014/2015
« Reply #368 on: March 23, 2015, 10:36:27 AM »
I had expected more of that combination of cold and winds, especially given the low extent, otherwise I wouldn't have written that blog post. Maybe an effect will become more noticeable in the next 2-3 days, but like you say, most probably not enough to challenge the prelim max.

There it is, 100K in two days on JAXA SIE. Difference with the prelim max is now 137K.

Looking at the JAXA imagery, it seems like the Kara sea has seen a big increase, as well as fresh ice on the north west coast of Russia. Bering has seen an extra push south, and Barents a small increase too.

Looks like these conditions, for the Kara/Barents region, will be reversed during Thursday, so just 3 days left for coverage increases. 194k (265k) off the max with the 5 day (1 day) NSIDC data. A sliver of a chance remaining to beat the max.




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Neven

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Re: Arctic Refreeze Discussion: 2014/2015
« Reply #369 on: March 23, 2015, 11:53:06 PM »
What the heck, I wrote another blog post about the max: The Ns are calling the maximum.

Quote
As expected, the Bering and Barents show an uptick in recent days (black and purple trend lines):



And as expected, this uptick was dampened by the start of the melting season on the outer fringes of the ice pack in Baffin Bay and the Gulf of St. Lawrence, where sea ice levels have been high all winter:



I won't be posting the forecast in detail, but suffice to say that JAXA needs to report very big upticks in the next two days to make up for the 137K difference with the preliminary max. And all of this ice has to appear in the Barents Sea, because warm waters in the North Pacific seem to be hampering serious ice growth in the Bering Sea.

The forecast has temps increasing and winds decreasing/turning in the Barents Sea after these two days, and so this really is the last opportunity for a slightly higher record. If it wasn't for my promise, I would now be joining the other Ns and call the maximum.
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