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weatherdude88

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Re: The 2017 freezing season
« Reply #50 on: August 29, 2017, 01:52:04 PM »
NSIDC northern hemisphere sea ice extent had another uptick today. we are now 102000 Kilometers squared above 8.25.2017. 8.28.2017 is now the highest value in the last 5 days.

Sterks

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Re: The 2017 freezing season
« Reply #51 on: August 30, 2017, 09:11:39 AM »
Significant cooling and snowing over the CAB toward the Beaufort side in the next days. The snow models of ESRL and GFS:
https://www.esrl.noaa.gov/psd/forecasts/seaice/
Not sure how to bring these animations here out of the noaa page.
The winds seem to keep pushing the ice from the South at Laptev and ESS from this model.

Ned W

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Re: The 2017 freezing season
« Reply #52 on: August 30, 2017, 11:53:38 AM »
Surprise! (or not)  -- it turns out that Aug 26 was not the JAXA extent minimum.  A pretty normal drop yesterday. 

Shared Humanity

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Re: The 2017 freezing season
« Reply #53 on: August 30, 2017, 07:07:12 PM »
Surprise! (or not)  -- it turns out that Aug 26 was not the JAXA extent minimum.  A pretty normal drop yesterday.

Not....at least not for me.

Brigantine

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Re: The 2017 freezing season
« Reply #54 on: September 04, 2017, 11:42:00 PM »
The re-freeze has now reached CIS maps.

Peabody bay as of 2017-09-04 18Z has 1/10 new ice alongside the 2/10 - 9/10 of one-summer-old ice. (Eureka - WIS36CT)

BTW, is this necessarily the result of freezing? Or is it possibly snow?

Ned W

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Re: The 2017 freezing season
« Reply #55 on: September 05, 2017, 02:50:57 PM »
That's three consecutive days of increasing extent in JAXA, since 1 September.  There are often several days of "false start" like this, but 2017 is tied with 2004 for the earliest three-day period of consecutive increases.  2015 had a similar run of three days starting a day later.

Tealight

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Re: The 2017 freezing season
« Reply #56 on: September 06, 2017, 11:24:48 AM »
By now over 95% of this years solar energy was either absorbed or reflected by the Arctic Ocean and I can finally post my refreeze-forecast.

When thinking about refreezing, the lowest sea minimum should also correlate with a low sea ice area / extent during the freezing season because a lot of open water has to refreeze. But the September minimum isn't quite as good as my AWP anomaly calculation, which considers absorbed heat by the oceans as well. For the last 11 years I compared the sea ice area minimum, the sea ice extent minimum and the cumulative AWP anomaly against the average sea ice area and extent anomaly during the October-December refreeze.

An Overview about individual years can be found here:
https://sites.google.com/site/cryospherecomputing/warming-potential


The AWP correlation is negative, because a higher solar energy absorption results in a slower refreeze, hence a negative area anomaly. See the attached graph for all 11 years.(the zero line is not the same for both axis and the secondary axis is inverted due to the negative correlation)

Correlation with Oct-Dec Extent anomaly
Minimum Area   0.779236221
Minimum Extent   0.699103822
Cumu AWP anomaly   -0.84296024
   
Correlation with Oct-Dec Area anomaly
Minimum Area   0.748245297
Minimum Extent   0.637113296
Cumu AWP anomaly   -0.784477392

Surprisingly for me all forecast methods correlate better with the sea ice extent anomaly and not the sea ice area anomaly. The ranking however always stays the same. The best is my cumulative AWP anomaly, followed by the sea ice area minimum and least skillful is the sea ice extent minimum.

For 2017 with a "cumu AWP" of +15.8 MJ/m2 we should expect an average extent anomaly of -0.22 million km2

Edit: without 2009 the AWP anomaly would correlate to 94% with sea ice extent and 93% with sea ice area
« Last Edit: September 06, 2017, 11:33:11 AM by Tealight »

Niall Dollard

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Re: The 2017 freezing season
« Reply #57 on: September 06, 2017, 11:13:20 PM »
The re-freeze has now reached CIS maps.


Yes. Today's map shows an area of pink (new ice) in the Kane Basin.

My interest today though switched to the Nansen Sound above Eureka, Ellesmere Island.

Eosdis Worldview image shows a lot of what looks like new ice in the sound (esp compared with previous clear image on 4th Sep).

However Sentinel does provide a nice close up of Nansen Sound on the 4th with some new ice.

Niall Dollard

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Re: The 2017 freezing season
« Reply #58 on: September 10, 2017, 12:06:43 PM »
An animated GIF on the thickening new ice in Nansen Sound, Ellesmere Island 3rd to 9th Sept.

2phil4u

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Re: The 2017 freezing season
« Reply #59 on: September 10, 2017, 04:10:10 PM »
By now over 95% of this years solar energy was either absorbed or reflected by the Arctic Ocean and I can finally post my refreeze-forecast.

When thinking about refreezing, the lowest sea minimum should also correlate with a low sea ice area / extent during the freezing season because a lot of open water has to refreeze. But the September minimum isn't quite as good as my AWP anomaly calculation, which considers absorbed heat by the oceans as well. For the last 11 years I compared the sea ice area minimum, the sea ice extent minimum and the cumulative AWP anomaly against the average sea ice area and extent anomaly during the October-December refreeze.

An Overview about individual years can be found here:
https://sites.google.com/site/cryospherecomputing/warming-potential


The AWP correlation is negative, because a higher solar energy absorption results in a slower refreeze, hence a negative area anomaly. See the attached graph for all 11 years.(the zero line is not the same for both axis and the secondary axis is inverted due to the negative correlation)

Correlation with Oct-Dec Extent anomaly
Minimum Area   0.779236221
Minimum Extent   0.699103822
Cumu AWP anomaly   -0.84296024
   
Correlation with Oct-Dec Area anomaly
Minimum Area   0.748245297
Minimum Extent   0.637113296
Cumu AWP anomaly   -0.784477392

Surprisingly for me all forecast methods correlate better with the sea ice extent anomaly and not the sea ice area anomaly. The ranking however always stays the same. The best is my cumulative AWP anomaly, followed by the sea ice area minimum and least skillful is the sea ice extent minimum.

For 2017 with a "cumu AWP" of +15.8 MJ/m2 we should expect an average extent anomaly of -0.22 million km2

Edit: without 2009 the AWP anomaly would correlate to 94% with sea ice extent and 93% with sea ice area

Do you talk about the difference of the anomaly now and the anomaly later ?
So if now for example we have -1 Mio, a Dezember of -1.2 Mio  is 200k change ?
Why dont you take the invert instead of getting a negative correlation.
In general i think in very low ice years we see a stronger refreeze, so if we have 3 Mio Minimum, in November we  surely have less then with a 5 Mio Minimum, but not 2 Mio less i guess.
Maybe you can find a formula that fits optimal for the years,you can also change the Nov values a bit if you think weather was unusal.
« Last Edit: September 10, 2017, 04:29:07 PM by 2phil4u »

Pavel

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Re: The 2017 freezing season
« Reply #60 on: September 10, 2017, 05:04:22 PM »
2017 looks warmer in the Laptev\ESS\Chuckchi than 2016. It's colder in the Kara\Barents but this side hit by fall\winter warm cyclones and freezing momentum is weak there. In general one should expect mild fall and sluggish ice growth

Pavel

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Re: The 2017 freezing season
« Reply #61 on: September 11, 2017, 07:30:58 PM »
Comparing some clear Wolrdview views from 30 of July and today we see the surface refreeze have taked place north of Greenland. Also there was significant ice retreat near Svalbard where it was 4-metres thick ice at the start of melting

Brigantine

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Re: The 2017 freezing season
« Reply #62 on: September 13, 2017, 10:49:05 PM »
My interest today though switched to the Nansen Sound above Eureka, Ellesmere Island.

Wise choice. That's the only place anywhere showing grey ice floes forming on the weekly CIS maps released today. (Eastern Arctic, areas V and EE have up to 3/10 of grey ice as 20-100m floes within the pink ice)

Niall Dollard

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Re: The 2017 freezing season
« Reply #63 on: September 14, 2017, 07:41:40 PM »
Ah yes Brigantine, Ellesmere and north Greenland the last cold bastion of the northern Hemisphere.  :)

There have been some nice clear images this September and looking back through Worldview on 10th September, it looks a lot more frozen than on the same date last year. (images attached, one year apart).  A little better than the other years shown on Worldview but I expect it's not that much different to what climatology would suggest, but maybe snow is a little more deep and extensive.

My hope for this freezing season is that the Ellesmere/Greenland cold will spread/extend readily across the CAA. The tongue in the eastern Beaufort should help the ice to develop in that section and help close the Beaufort Bite.

The western Beaufort and Chukchi will be problematic due to high SSTs and I expect slow extension into these seas.

I'd hope there is early/extensive/deep snowfall across the top of Russia. Snow and associated low autumnal temps could help the pack extend readily through the Laptev/Kara and ESS. But as it stands there is a considerable gap between the ice edge and Russia. I think if we do not see a good extension of a solid pack covering much of the Arctic Basin quite soon, the DMI N80 temps will struggle once again to reach the ERA40 (1958-2002) mean over the winter half of the year (like last year). Already the drift away from the old "norm" has begun . http://ocean.dmi.dk/arctic/meant80n.uk.php

The SSTs in the Barents perplexes me. Especially in the northern part. Typically the last few years, the SSTs in the Barents have been very high. Recent months they are lower. But I doubt if this will have much significant effect on ice extension until maybe late this Winter/Spring as no doubt there will be many autumn/winter Atlantic storms to come preventing ice extension.

Having said all this, it can and probably will all go pear shaped and we will end up next May with yet another thin/weak pack. It looks like we will still be scratching around hanging on until the next big El Nino year wreaks havoc. Probably needs a miracle at this stage or somehow a plateauing of CO2 emissions.


Brigantine

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Re: The 2017 freezing season
« Reply #64 on: September 15, 2017, 09:33:34 AM »
A reasonable amount of pink ice forming in the Chukchi sea (per CIS).

At 78N, only where the surface waters are kept chilled by melting open drift ice from last winter, and even then it's patchy. (for reference: at 78N, 135W - 150W)

Compared with the same date 2014 and 2015, the re-freeze this year is a bit further advanced.
(and surviving ice much sparser)

Though by this date (+1 day) in 2016 at the same latitude, the refreeze had already developed even further - comprehensive new ice (9+/10) in areas without more than a trace of surviving ice, and around open drifts of surviving ice the re-freeze was already at the stage that Nansen Sound is this year (on 2017-09-11).
« Last Edit: September 15, 2017, 09:40:21 AM by Brigantine »

Niall Dollard

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Re: The 2017 freezing season
« Reply #65 on: September 15, 2017, 06:19:03 PM »
Yes on many of the CIS regional maps Chukchi/Beaufort/Northern parts of CAA, there are many areas now coloured pink (new ice).

It has been cold. For the week ending Sept 11th mean temp at Eureka was -8.8 C (norm -4.3) and Resolute -3.4 C (norm -2.8 ).

Thomas Barlow

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Re: The 2017/2018 freezing season
« Reply #66 on: September 16, 2017, 10:43:58 PM »
Judging by this, the Arctic Ocean itself (ignoring all peripherals such as CAA and Fram, etc., and thick ice crushed against land - "bits of ice stuck to land", as Wadhams puts it, re. a future 'Blue Ocean Event') looks like the overall ocean itself (ignoring fjords and coastal build-up) is about as bad a state as it gets for volume, maybe worst, at the start of freezing season.

Niall Dollard

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Re: The 2017/2018 freezing season
« Reply #67 on: September 16, 2017, 11:53:31 PM »
Judging how, by eye, Thomas ? As to pronounce which is worst, I wouldn't wish to comment as brain/eye can be deceptive.

Pavel

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Re: The 2017/2018 freezing season
« Reply #68 on: September 16, 2017, 11:53:58 PM »
Very much of survived FY ice. The ice formed last October in the Laptev sea now above the Pole. Another issue is that export goes mostly to the Beaufort but not Fram strait. In general the start of refreeze in terms of accumulated FDD is similar with 2016. It will take a long while when the periphery seas start to freeze up. The question should be whether the  freezing season will be very mild or extremely mild

Thomas Barlow

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Re: The 2017/2018 freezing season
« Reply #69 on: September 17, 2017, 12:37:53 AM »
Judging how, by eye, Thomas ? As to pronounce which is worst, I wouldn't wish to comment as brain/eye can be deceptive.
No, not really. It's pretty clear to a well trained eye. ;-)

Pavel

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Re: The 2017/2018 freezing season
« Reply #70 on: September 18, 2017, 06:48:30 PM »
These two DMI graphs of north of 80 latitude temps and Greenland ice sheet mass budget pretty show the mild and snowy story continues. Could be a pattern for the whole season

Alec aka Daffy Duck

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Re: The 2017/2018 freezing season
« Reply #71 on: September 19, 2017, 01:06:14 AM »

Daniel B.

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Re: The 2017/2018 freezing season
« Reply #72 on: September 19, 2017, 03:28:08 PM »
These two DMI graphs of north of 80 latitude temps and Greenland ice sheet mass budget pretty show the mild and snowy story continues. Could be a pattern for the whole season

Already ahead of the pace set in 2016/17.

Shared Humanity

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Re: The 2017/2018 freezing season
« Reply #73 on: September 19, 2017, 03:57:12 PM »
These two DMI graphs of north of 80 latitude temps and Greenland ice sheet mass budget pretty show the mild and snowy story continues. Could be a pattern for the whole season

Already ahead of the pace set in 2016/17.

Our climate is changing. We should expect to be surprised by new persistent features of this changing climate. With more moisture in our atmosphere, increased snowfall would seem to be a logical result.

Shared Humanity

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Re: The 2017/2018 freezing season
« Reply #74 on: September 19, 2017, 04:02:23 PM »
These two DMI graphs of north of 80 latitude temps and Greenland ice sheet mass budget pretty show the mild and snowy story continues. Could be a pattern for the whole season

A snowier Greenland would suggest a snowier Arctic Ocean as well, at least on the Atlantic side. This was a point of heated discussion during the just completed melt season. If the Atlantic cyclone cannon fires up like it did last winter, I would think that more snow would fall. Could this heavier snowfall explain the conditions we find on the Atlantic side of the Arctic where the ice was remarkably resistant to melt?

Daniel B.

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Re: The 2017/2018 freezing season
« Reply #75 on: September 19, 2017, 05:14:43 PM »
These two DMI graphs of north of 80 latitude temps and Greenland ice sheet mass budget pretty show the mild and snowy story continues. Could be a pattern for the whole season

Already ahead of the pace set in 2016/17.

Our climate is changing. We should expect to be surprised by new persistent features of this changing climate. With more moisture in our atmosphere, increased snowfall would seem to be a logical result.

That would be true only for those locations consistently below freezing.  Otherwise, we would expect more of the snow to fall as rain.

Dharma Rupa

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Re: The 2017/2018 freezing season
« Reply #76 on: September 19, 2017, 05:21:05 PM »
That would be true only for those locations consistently below freezing.  Otherwise, we would expect more of the snow to fall as rain.
I think you can use the northward march of the permafrost and several species of trees as a pretty good proxy for the rain/snow line.  Still far enough south that I think we can expect plenty of snow this winter, but maybe not a decade from now.


Pavel

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Re: The 2017/2018 freezing season
« Reply #77 on: September 19, 2017, 10:38:33 PM »
The Garlic Press still in action. Winds may change direction backward for some days but then it should resume. Ice was squeezing through the strait for the entire September not even depended on winds very much

Brigantine

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Re: The 2017/2018 freezing season
« Reply #78 on: September 20, 2017, 12:12:01 AM »
First sight on CIS daily charts of grey ice in the Eastern Arctic - in the Parry Channel around 102W.
(Approaches to Resolute 2019-09-19, areas D, G and M)

Also the first time in the Chukchi Sea that grey ice is forming in areas without surviving drift ice.
(Area D)

The new ice in Nares Strait and the Beaufort Tongue OTOH is struggling just to survive.

Alec aka Daffy Duck

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Re: The 2017/2018 freezing season
« Reply #79 on: September 20, 2017, 10:37:32 PM »
Hopefully this image comparing SST for Kara and Barents 2016 v 2017 will work:




<Alec, if you highlight the link, and then click on the img/image button (middle row, second from left, next to small f/flash button), the links will then show up as images. Or you can click 'attachment and other options' below the comment box and upload them to the Forum server directly; N.>
« Last Edit: September 21, 2017, 03:51:21 PM by Neven »

Pavel

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Re: The 2017/2018 freezing season
« Reply #80 on: September 20, 2017, 11:32:51 PM »
Hopefully this image comparing SST for Kara and Barents 2016 v 2017 will work:
https://s19.postimg.org/7f2nx4c9f/aab_sst_2016_2017.png
https://postimg.org/image/k6gu3mm1b/
Interesting that Hycom shows very warm currents north of Svalbard resume. North of Kara almost the only area relatively cold in terms o SSTs but it most likely should be hit by warm storms, it's not the area to build meters of ice. The Laptev sea that is the factory of ice for CAB looks warmer, ESS\Chukchi\Beaufort are terrible. The Hudson Bay and Sea of Okhotsk are overheated and promising low extent for the entire freezing season. Most likely we'll expierence the negative phase of the Arctic Oscillation

Niall Dollard

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Re: The 2017/2018 freezing season
« Reply #81 on: September 21, 2017, 08:04:48 PM »
Judging how, by eye, Thomas ? As to pronounce which is worst, I wouldn't wish to comment as brain/eye can be deceptive.
No, not really. It's pretty clear to a well trained eye. ;-)

So the PIOMAS half September figures are in and the min volume this year was 4.542 x 103 km3.

As Wipneus pointed out in the other thread, this is the 4th lowest min. The list being, in order of lowest:

3.673 (2012)
4.303 (2011)
4.402 (2016)
4.542 (2017)

2017 was close to 2016, but still an uptick in volume. Is this in line with what your well trained eyes was suggesting ?

From a PIOMAS volume POV, it is hardly the worst ever start to the freezing season. 

Niall Dollard

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Re: The 2017/2018 freezing season
« Reply #82 on: September 21, 2017, 10:52:29 PM »
The ECMWF shows some cooling on the Russian side over the weekend and early days of next week. If this comes to fruition we may finally see a bit of a move on the ice edge at the Russian side. Surface chart show temps circa -9 C between Severnaya Zemlya and New Siberian Islands. Temp at the 850hPa down to -18 C and then surface temps sub -9C for much of the week in that area.

At the end of the run, cold moves on down over the Chukchi but at the same time much warmer over Svalbard and the Atlantic side. So it is going to be give and take. 

2phil4u

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Re: The 2017/2018 freezing season
« Reply #83 on: September 22, 2017, 01:08:30 PM »
Looking at dmi forecast you can see that the pacific side is still melting a bit, it will take maybe 2-3 weeks before we see big refreezes here.
In my opinion after this year we can see, that very often the effect of open ice in september in many years like last years may have a positive effect of next years ice.
Maybe the water just cools down more if it refreeze later.
So many years with catastrophic ice and regain the next year now.

jdallen

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Re: The 2017/2018 freezing season
« Reply #84 on: September 23, 2017, 03:13:17 AM »
Looking at dmi forecast you can see that the pacific side is still melting a bit, it will take maybe 2-3 weeks before we see big refreezes here.
In my opinion after this year we can see, that very often the effect of open ice in september in many years like last years may have a positive effect of next years ice.
Maybe the water just cools down more if it refreeze later.
So many years with catastrophic ice and regain the next year now.
South of 80N will refreeze more slowly, possibly not refreeze for quite a while.

Not sure if the heat loss will make up for the net increase in enthalpy.

We may see a lot of imported heat from cyclonic storms pulling moisture north from tropical and mid latitutdes.

That will slow heat loss from the Arctic.
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meddoc

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Re: The 2017/2018 freezing season
« Reply #85 on: September 23, 2017, 08:54:19 AM »
Last Year massive Re- freeze only began by mid- December- according to HYCOM.
This Year should be no different, as Hycom is still showing Melt ongoing and Dispersion around the NP.

gerontocrat

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Re: The 2017/2018 freezing season
« Reply #86 on: September 23, 2017, 01:14:36 PM »
I know people have considerable reservations on the usefulness of the DMI 80+ N temperature graph. For observers such as me, at least it gives an idea of the direction of travel. At the moment, it suggests slow refreezing in the high Arctic.
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Pavel

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Re: The 2017/2018 freezing season
« Reply #87 on: September 23, 2017, 01:30:29 PM »
Most of the survived ice stored north of 80 latitude. Since it relatively thick it needs more FDDs to grow. Freezing at open waters isn't happening yet. It should take quite while to strengthen the freezing momentum

Niall Dollard

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Re: The 2017/2018 freezing season
« Reply #88 on: September 23, 2017, 02:24:54 PM »
As said already with high SSTs and globally it being a warm year, arctic freezing is struggling.

Latest Eurasian snow cover image only shows snow at far north and sprinklings elsewhere. A decent Siberian snow cover would be beneficial to ice devlopment in the Laptev and ESS. When the large Siberain anticyclone develops even SW winds coming off the Asian land mass will be very cold. I think we would need something like a snow cover that would manage to fill the magenta coloured area below, over the next few weeks (October).

The changing Arctic climate is starting to produce more snow, but it remains to be seen whether there will be much progress this autumn.

Dharma Rupa

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Re: The 2017/2018 freezing season
« Reply #89 on: September 23, 2017, 05:27:13 PM »
Last year I thought this was an interesting diversion, but this year it is beginning to look like a trend:

Dharma Rupa

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Re: The 2017/2018 freezing season
« Reply #90 on: September 23, 2017, 06:01:36 PM »
I know people have considerable reservations on the usefulness of the DMI 80+ N temperature graph. For observers such as me, at least it gives an idea of the direction of travel. At the moment, it suggests slow refreezing in the high Arctic.

I'm perfectly fine with DMI 80N as a gross measure of what is going on.  I can understand why people might not like it when looking at the details, but it tells us rather directly that the big change in what is going on is happening in the Fall and Winter, not the Summer.

Niall Dollard

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Re: The 2017/2018 freezing season
« Reply #91 on: September 23, 2017, 07:51:05 PM »

I'm perfectly fine with DMI 80N as a gross measure of what is going on.  I can understand why people might not like it when looking at the details, but it tells us rather directly that the big change in what is going on is happening in the Fall and Winter, not the Summer.

What's going on in the autumn/fall and winter is a legacy of the summer conditions. It's all about the ice (or lack of it). Deviations on the DMI 80N are small in summer because we still have ice there (just about). However as we now move into autumn/winter we still only have a relatively small area of ice surrounded by warm seas. It's still easy enough to import milder air into the 80N circle. That's one of the reasons why the DMI graph starts to deviate so much from the norm at this time of the year.

If we had a blue ocean summer I'm sure the DMI graph would stray far away from norm too, in summer, once the ice is gone.

bbr2314

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Re: The 2017/2018 freezing season
« Reply #92 on: September 23, 2017, 08:13:09 PM »
Snowcover should build very rapidly through early October. GFS/CMS/EURO all show a massive area of anomalously cold temps building across most of Eurasia by D10 corresponding to generous snowfalls across much of Siberia and the Central Asian Plateau. We will also see the first falls across much of Alaska, the NW Territories/Yukon, and Quebec, with possible lasting duration across the latter.

I think it is important to reflect on the divergent signals that have emerged at the same time over the past few years. Namely, Greenland is now *increasing* in ice mass, with albedo massively increased in year over year comparisons due to the tremendous and ongoing snowfalls that have been occurring. In fact I believe we have probably still seen the same or more melt than is normally seen, however, the sheer frequency of massive snowfalls has been sufficient (IMO) to overwhelm -- i.e., the same thing resulting in Houston's floods is now seemingly occurring up north in a format that is white and not wet. This at the same time that global sea ice is once again setting a record-low maximum...!

My suspicion is that this massively unexpected positive albedo trend over Greenland was directly responsible for the surprisingly meek melt season. In fact, it is the most obviously glaring unexpected happening of the past 12 months that it is quite likely to have been the cause.

The question is what happens moving forward? Snowcover is currently somewhat above average, that should increase to well above average as we move into October, both according to the models and as indicated by recent changing climatology. Besides Greenland's increase in mass, the Himalayas have also stayed overwhelmingly white through the summer. The combination of these albedo anomalies and the record-warm Arctic ocean waters should yield more opportunities for early season snowfall (IMO) and we may see record #s.






Pavel

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Re: The 2017/2018 freezing season
« Reply #93 on: September 23, 2017, 08:21:18 PM »
The MYI floats drift toward the Fram strait. The animation below is from 19 to 23 of September. From Hycom forecast the Fram export will resume finally
« Last Edit: September 23, 2017, 08:27:52 PM by Pavel »

Dharma Rupa

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Re: The 2017/2018 freezing season
« Reply #94 on: September 24, 2017, 02:46:11 PM »
If we had a blue ocean summer I'm sure the DMI graph would stray far away from norm too, in summer, once the ice is gone.

I'm sure of that, but that will be in the future, not the present (and recent past).

Actually, the big change in DMI 80N happened in a single day in December 2015.  The question this winter is, will it continue for a third winter or revert to the norm -- and so far it's looking like it will continue.

Niall Dollard

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Re: The 2017/2018 freezing season
« Reply #95 on: September 24, 2017, 06:24:34 PM »

I'm sure of that, but that will be in the future, not the present (and recent past).

Actually, the big change in DMI 80N happened in a single day in December 2015.  The question this winter is, will it continue for a third winter or revert to the norm -- and so far it's looking like it will continue.

I see what you mean re Dec 2015. Around that time the big El Nino was in full swing. Global temp anomalies have remained high since.

Agreed there is little to indicate that we will have a different winter this time.

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Re: The 2017/2018 freezing season
« Reply #96 on: September 25, 2017, 11:48:36 AM »
The UH AMSR2 site provides a very convenient one-click measure of open water in the Arctic Ocean for every day from August 2012 to the present. The first animation below looks at Sept 2012 relative to the minimum (for the month) on Sept 3rd and the melt-season maximum attained on Sept 12th.

The streaming numbers give the percentages of those days relative to those dates, minimum in the middle, maximum on the right. Open water has been mostly shrinking though on some days it increases. Reasons aren't determined by UH but could could include ice compaction, freeze, ridging and so on. The fixed gold line overlay shows the boundary of open water on the 12th.

The second animation takes the difference of each day relative to the 12th. The color scheme goes to 2D as the UH palette consists of 100 blues and whites, so subtraction results in a combinatoric palette, in effect what's called a bivariate chloropleth. Here the fixed open water boundary of the 12th is in light blue. The frame for the 12th is black from subtracting it from itself.

It is slightly more accurate to do the differencing earlier in the pipeline, from grid cells in the netCDF furnished by UH. That can be done in Panoply with the 'Combine Plot' feature that first subtracts the arrays grid cell by grid cell and only then draws the map in the chosen PS projection. (In Gimp, subtraction is done off the final map which is not quite equal area.) A still from grid subtraction is shown at the bottom in a red-blue diverging palette.

The third animation uses ten days of forecast data from RASM-ESRL concerning the compressive strength of the ice pack. Unsurprisingly, low concentration ice near the periphery is more compressible. While the units of that, newtons per meter, are not so intuitive, they measure how much the ice pack (considered as a viscous plastic) deforms in response to an applied force. These numbers range so widely that a logarithmic scale is more effective as palette animation. An inset shows shape change for the same dates in Hycom.

These animations can be made for any data range by scripting the download of netCDF data from a remote server (Fetch), opening a map in the desired palette and projection and saving out png frames (Panoply JavaScript) and cropping and layering up (Gimp batch). This just pipelines scientific visualization; the actual science went into processing satellite imagery and running the computationally intensive models that end up as the data archives.

The Arctic Ocean alone is the subject of 60-70 daily netCDFs describing the state of various physical parameters. Some of these are redundant, just using different satellites and algorithms for the same basic product, typically on different grids at different resolutions. Others are just input ingredients for models and don't overly concern us at the forums.

Validation of graphical products is complex. The data (like SMOS thin ice) may be more accurate in certain seasons than others; older published validations studies may not be applicable to New Arctic ice. Forecast 'skill' may be higher during stretches of really boring weather (summer 2017?) than during or after major wind events, significant on-edge wave heights, or moisture advection from the sout.

Some products like open water get 'reset' daily by easy-to-interpret satellite data, meaning models can't drift too far away from reality. Others like ice thickness or ice age get only partial resets in the fall as open water freezes to first year ice, allowing errors in older ice to accrue and persist.

Products concerned with long-term consistency and statistical trends are not likely to embrace new satellite technology (eg Sentinels) or integrate new hybrid methods because there's no way to go back to update earlier parts of the satellite record.

Below are three fairly recent studies on Arctic Ocean compressive strength and how it is measured.

Estimating the Sea Ice Compressive Strength from Satellite-Derived Sea Ice Drift and NCEP Reanalysis Data
LB Tremblay et al Nov 2006 free full text
http://journals.ametsoc.org/doi/pdf/10.1175/JPO2954.1+

On the mechanical behavior of compacted pack ice : A theoretical and numerical investigation
K Wang dissertation 2007
https://helda.helsinki.fi/handle/10138/23122

A younger, thinner Arctic ice cover: Increased potential for rapid, extensive sea-ice loss
JA Maslanik et al Dec 2007 free full text
http://onlinelibrary.wiley.com/doi/10.1029/2007GL032043/full
« Last Edit: September 25, 2017, 09:11:31 PM by A-Team »

Niall Dollard

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Re: The 2017/2018 freezing season
« Reply #97 on: September 25, 2017, 04:48:18 PM »
ESRL Initial (2017-09-24 00Z) and 5 day forecast ice thickness.


Daniel B.

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Re: The 2017/2018 freezing season
« Reply #98 on: September 25, 2017, 05:36:23 PM »
Snowcover should build very rapidly through early October. GFS/CMS/EURO all show a massive area of anomalously cold temps building across most of Eurasia by D10 corresponding to generous snowfalls across much of Siberia and the Central Asian Plateau. We will also see the first falls across much of Alaska, the NW Territories/Yukon, and Quebec, with possible lasting duration across the latter.

I think it is important to reflect on the divergent signals that have emerged at the same time over the past few years. Namely, Greenland is now *increasing* in ice mass, with albedo massively increased in year over year comparisons due to the tremendous and ongoing snowfalls that have been occurring. In fact I believe we have probably still seen the same or more melt than is normally seen, however, the sheer frequency of massive snowfalls has been sufficient (IMO) to overwhelm -- i.e., the same thing resulting in Houston's floods is now seemingly occurring up north in a format that is white and not wet. This at the same time that global sea ice is once again setting a record-low maximum...!

My suspicion is that this massively unexpected positive albedo trend over Greenland was directly responsible for the surprisingly meek melt season. In fact, it is the most obviously glaring unexpected happening of the past 12 months that it is quite likely to have been the cause.

The question is what happens moving forward? Snowcover is currently somewhat above average, that should increase to well above average as we move into October, both according to the models and as indicated by recent changing climatology. Besides Greenland's increase in mass, the Himalayas have also stayed overwhelmingly white through the summer. The combination of these albedo anomalies and the record-warm Arctic ocean waters should yield more opportunities for early season snowfall (IMO) and we may see record #s.

The Western mountains of the U.S. has seen a swatch of snowfall also. 

A-Team

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Re: The 2017/2018 freezing season
« Reply #99 on: September 25, 2017, 08:20:32 PM »
Here is a nicely done HDF5 archive from NSIDC, sea ice concentration done now from microwave on the F18 satellite. The annotation is unusually thorough; to see it, download any date, open the file just like a netCDF and set the Source window view in Panoply to show all variables in the data set panel in enhanced mode.

Not being thrilled with 25 km x 25 km resolution sea ice concentration (while acknowledging the importance of such long-term records), I looked for other geolocated products (mappable in user's favorite projection and palette, designated as Geo2D in Panoply) in the HDF5 bundle.

There are two of interest, one called Melt Day Onset which seems to be a static file made in late spring 2017 and another called standard deviation of sea ice concentration which may be related to error assessment.

The former marks up ice pack locations according to the date when melt was first observed. That's of interest per se but only 2016 appears provided as a comparison year. This archive is something to be watched (along with ESRL's daily melt ponds) in spring 2018, presuming melt ponds are a helpful leading indicator for summer outcome.

The graphic below -- just the double-click default in Panoply -- shows Melt Day Onset in 'greenland down' stereographic projection in a sequential palette. It appears that the earliest melt recorded occurred on Day 60 but melt had been seen everywhere by Day 189. That latter date was presumably used for picturing the ice extent to be colored.

NSIDC may or may not have put a similar graphic somewhere on their vast web site. Note with the HDF file and Panoply, we can make a large colorful contoured map; however once past intrinsic data resolution that requires software interpolation which may not be physically meaningful.

The std dev we can make more simply in ImageJ off any sea ice product map (along with mean and variance filtering, for whole animation stacks too) but it's better to work from original girdded numeric data. Note here Panoply can export HDF5 data into human-readable form (the CDL option), though a lot of people here use the R statistical package which can read these files directly (package 'ncdf4'). Climate data can have lots of data hole, stored as NaN grid cell entries for Not a Number, which ImageJ can map out.

People may recall the endless hubbub over the 'hockey stick' graphic, it being claimed (wrongly) height and width scales were deliberately chosen to be misleading. However there is something to be said for seeking accuracy in scientific visualizations, or rather helping the viewer form an accurate impressions.

While there's been endless hubbub bashing rainbow palettes, misleading for a prevalent retinopathy in white males, there's been little discussion of palette optimization in rapid-fire gif animations. Over in that section of Dev Corner, there'll also be discussion of 'adaptive' palettes which are not aesthetic choices but rather objectively driven by 2D statistical properties of the data itself.

Note here that 'Integral Image Filters' over at ImageJ allows analysis and suppression of data outliers as well as various radial map statistics. The former allows objective setting of palette range which is very important to equalizing palette color usage and viewer feature discrimination. The latter show variation by distance out from a given pixel which could be useful in optimizing the  number of palette colors, avoiding maps that are too 'busy' to be contoured, etc.

ftp://sidads.colorado.edu/pub/DATASETS/NOAA/G10016/north/daily/2017/
« Last Edit: September 25, 2017, 09:09:23 PM by A-Team »