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Dharma Rupa

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Re: The 2018/2019 freezing season
« Reply #400 on: October 18, 2018, 01:04:22 AM »
This should slow down the freezing season in the Chukchi this winter and slow the onset of deep convection in the Labrador sea.
Roughly, what is the time it takes for Chuckchi water to reach the Labrador sea?


FishOutofWater

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Re: The 2018/2019 freezing season
« Reply #401 on: October 18, 2018, 03:53:09 AM »
Water that gets subducted into into subsurface layers takes years to do anything in the Arctic ocean.  When the oceanographers figure out when that water comes back up I will tell you or you will tell me. The paper did not report on subducted heat resurfacing. So the answer is, I don't know.

What's important to us now is that the Chukchi is changing rapidly before our eyes into a mostly ice free region in the arctic. This will affect both the atmosphere and the ocean in years to come and this year well into late fall and early winter.

I took another look at the Mercator scales. They were the same. Don't trust the forecasts.

Aluminium

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Re: The 2018/2019 freezing season
« Reply #402 on: October 18, 2018, 06:25:23 AM »
October 13-17.

Niall Dollard

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Re: The 2018/2019 freezing season
« Reply #403 on: October 18, 2018, 09:19:52 AM »
Thanks for that animation Aluminium.

The time lapse shows something we don't see too often. A flash freeze in the central Beaufort. Usually ice freeze either extends out from the main pack edges or from the continent edges. Here we can see a large freeze in the central Beaufort that was not connected to the main pack.

Not sure if this is connected with that patch of old ice in the Beaufort (I thought it had migrated further west) or maybe an area of low salinity water surrounded by slightly higher salinity that froze first ?

gerontocrat

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Re: The 2018/2019 freezing season
« Reply #404 on: October 18, 2018, 12:00:30 PM »
What's important to us now is that the Chukchi is changing rapidly before our eyes into a mostly ice free region in the arctic. This will affect both the atmosphere and the ocean in years to come and this year well into late fall and early winter.

I attach graphs showing the progress of the Chukchi to an open water sea.
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uniquorn

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Re: The 2018/2019 freezing season
« Reply #405 on: October 18, 2018, 12:44:23 PM »
Thanks for that animation Aluminium.

The time lapse shows something we don't see too often. A flash freeze in the central Beaufort. Usually ice freeze either extends out from the main pack edges or from the continent edges. Here we can see a large freeze in the central Beaufort that was not connected to the main pack.

Not sure if this is connected with that patch of old ice in the Beaufort (I thought it had migrated further west) or maybe an area of low salinity water surrounded by slightly higher salinity that froze first ?
ascat, sep27-oct17 appears to show it is related to the plucky patch of old ice

@FOoW, agree, mercator forecasts often don't appear to match with last analysis. Even using fixed scale images.

Phil.

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Re: The 2018/2019 freezing season
« Reply #406 on: October 18, 2018, 04:12:37 PM »
Thanks for that animation Aluminium.

The time lapse shows something we don't see too often. A flash freeze in the central Beaufort. Usually ice freeze either extends out from the main pack edges or from the continent edges. Here we can see a large freeze in the central Beaufort that was not connected to the main pack.

Not sure if this is connected with that patch of old ice in the Beaufort (I thought it had migrated further west) or maybe an area of low salinity water surrounded by slightly higher salinity that froze first ?

Looks like it's the main ice breaking up and being carried west, here's a shot from a couple of days ago from Worldview:
https://go.nasa.gov/2R4ExVN

oren

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Re: The 2018/2019 freezing season
« Reply #407 on: October 18, 2018, 04:16:19 PM »
A look at FDDs confirms that the season has not started well.

FishOutofWater

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Re: The 2018/2019 freezing season
« Reply #408 on: October 18, 2018, 04:21:25 PM »
Phil, I don't think ice moved quickly enough to do what you think it did. I think that the freezing front propagated quickly along a freshwater layer created by melting ice in the summer months. I think there was clear sky and radiational cooling in the area of freeze up. Without clouds heat is lost rapidly in the in the Arctic darkness.

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Re: The 2018/2019 freezing season
« Reply #409 on: October 18, 2018, 05:42:34 PM »
The GFS 2M temperatures forecast shows cold building in Siberia throughout the next week... the open ocean water really seems to be keeping air temperatures in the Arctic Ocean anomalously warm over the same timeframe.  My current darling is the warm arctic cold continents scenario, perhaps there is a glimpse into the future based on what emerges.  Certainly, there are considerable regions of colder 2M air temperatures over land than over water.  But, I didn't come here to point and grunt at the GFS.. I'm wondering if there is an existing WACC index time series?

Looking at various troposphere pressure anomalies in the latter half of GFS forecast shows ... I wanna say kaleidoscopic ? is there a better term for this pattern?  It's like vortex lows swirling eachother but it breaks into two patterns with one over Siberia, one over CAA/Greenland... Kaleidoscopic I wanna say.  Reminds me of a bucket of swirling paint.

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Re: The 2018/2019 freezing season
« Reply #410 on: October 18, 2018, 06:20:14 PM »
I believe the sudden growth in the Beaufort/CAB is thanks to the sliver of ice that remained in the Beaufort. That small amount of ice begat more ice very fast, encircling a huge swath of the ocean, giving it the perfect conditions for fast refreeze.
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Niall Dollard

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Re: The 2018/2019 freezing season
« Reply #411 on: October 18, 2018, 07:16:07 PM »
Here is an image of the developing ice patch in the Beaufort on Oct 15th. Oriented top north. The main pack is located over 300km to the east - too far away to be break off. I agree it is most likely linked to the plucky patch of old ice. 

Pmt111500

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Re: The 2018/2019 freezing season
« Reply #412 on: October 18, 2018, 07:34:42 PM »
October 13-17.
Hey, that's a cool animation, could you extend it to start few days (say 4) days earlier and end in about 4-7 more?

Tor Bejnar

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Re: The 2018/2019 freezing season
« Reply #413 on: October 18, 2018, 07:41:13 PM »
Niall,
Is that a giant jellyfish on the right?
 ;D ::) :P
Arctic ice is healthy for children and other living things because "we cannot negotiate with the melting point of ice"

Niall Dollard

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Re: The 2018/2019 freezing season
« Reply #414 on: October 18, 2018, 08:40:20 PM »
Niall,
Is that a giant jellyfish on the right?
 ;D ::) :P
Yes, Tor I saw that earlier. Thought it was a bit like a euro symbol.
 :).

bbr2314

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Re: The 2018/2019 freezing season
« Reply #415 on: October 18, 2018, 09:10:54 PM »
Foxe Basin is now home to a rapidly growing area of grey ice. As of 10/15,


litesong

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Re: The 2018/2019 freezing season
« Reply #416 on: October 18, 2018, 09:57:10 PM »
The time of the great loss of 2012 Arctic sea ice, setting the lowest ever sea ice extent spanning months, has come to an end, now past mid-October. The to-date arctic sea ice extent for 2007 is now the lowest extent, & 2007 is soon to be passed by 2016 sea ice low, which was a tremendous comparative downward surge during this period of rapidly gathering Arctic sea ices. It is not coincidental that the 2016 wild DECREASE in sea ice GAIN, occurred when the gap between the satellite average High Arctic temperature & 2016 High Arctic temperature, was at its widest ever ( ~ +20degC) averaged over millions of square kilometers.
With all this sea ice... "decrease of the increase", it will be very interesting to see what the to-date sea ice extent of 2018 will bring in these future weeks, since to-date 2018 sea ice extent is rivaling 2012, 2007, & 2016, & a "long term" 2018 High Arctic high temperature is presently reigning.
« Last Edit: October 18, 2018, 10:06:18 PM by litesong »

Aluminium

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Re: The 2018/2019 freezing season
« Reply #417 on: October 18, 2018, 10:09:00 PM »
Hey, that's a cool animation, could you extend it to start few days (say 4) days earlier and end in about 4-7 more?
After 4-7 days, of course. I saved single images since June 8.

uniquorn

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Re: The 2018/2019 freezing season
« Reply #418 on: October 18, 2018, 11:48:12 PM »
ESRL ice and snow thickness forecast, oct17-24. Steady pack expansion and Alaskan, ESS and Laptev coastal ice growth over the next week. (Missed the Beaufort flash freeze though)
edit: Not sure how that forecast will turn out with current SST's, though there are already signs of those coasts freezing on amsr2

https://floe.keytwist.net/esrl-daily-forecasts/2018-10-17
« Last Edit: October 18, 2018, 11:58:41 PM by uniquorn »

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Re: The 2018/2019 freezing season
« Reply #419 on: October 19, 2018, 12:15:22 AM »
Laptev looks to be in for a bit of heat, especially on the CAB side.  We might still see some decent ice growing along the Siberian coast.

Niall Dollard

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Re: The 2018/2019 freezing season
« Reply #420 on: October 19, 2018, 12:46:47 AM »
ESRL ice and snow thickness forecast, oct17-24. Steady pack expansion and Alaskan, ESS and Laptev coastal ice growth over the next week. (Missed the Beaufort flash freeze though)


It's strange alright that ESRL did not pick up on the sudden changes in the more western Beaufort.

Here is the NSIDC view on Oct 17th. That Beaufort blob does look remarkable, compared with the image 3 days earlier.

be cause

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Re: The 2018/2019 freezing season
« Reply #421 on: October 19, 2018, 02:55:07 AM »
to see the beaufort blob and it's origins best to run Worldview from @ 5th Oct .. it is possible to see thru the clouds most days and on the 16th you can see the new ice with the old embedded ..
as for dmi80' .. the high Arctic .. the regional anomaly remains 10'C above normal and/or where it should have been 31 days ago .. and most of the last 23 days have broken daily records .
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litesong

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Re: The 2018/2019 freezing season
« Reply #422 on: October 19, 2018, 04:07:08 AM »
....the gap to the present "2010's Arctic sea ice" average widening again to 440,000 square kilometers LESS.
.....2018 Arctic sea ice is 550,000 square kilometers LESS than the to-date "2010's sea ice average". 2018 now has more to-date sea ice than ONLY the year 2012, which had a spectacular loss of sea ice, much going away due to fortuitous winds that drove ices into the North Atlantic.
To-date 2018 Arctic sea ice is 720,000 square kilometers LESS than the to-date "2010's sea ice average".

litesong

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Re: The 2018/2019 freezing season
« Reply #423 on: October 19, 2018, 04:41:35 AM »
It is not coincidental that the 2016 wild DECREASE in sea ice GAIN, occurred when the gap between the satellite average High Arctic temperature & 2016 High Arctic temperature, was at its widest ever ( ~ +20degC) averaged over millions of square kilometers.
Yes indeed! During this time of year when Arctic sea ice rapidly increases, there are very very few short periods of Arctic sea ice DECREASES. Yet, 2016 had two distinct periods of sea ice decrease, both losing periods occurring when 1) High Arctic temperature over millions of square kilometers  was 20(+?) degC above average & 2) High Arctic temperature over millions of square kilometers was ~ 16degC above average. As stated previously, 2018 may be setting itself up for a wild decrease in sea ice, if present 2018 High Arctic high temperatures go even higher.
We will see what the future temperatures & sea ices will do. There are two major cold fronts that could cool the High Arctic, one from the Canadian archipelago & one from the Greenland Ice Sheet, & a small cold front on High Siberia. So far the High Arctic resists the cold & predictions indicate that the High Arctic should stay warm.....for a while. 
« Last Edit: October 19, 2018, 02:14:26 PM by litesong »

Pmt111500

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Re: The 2018/2019 freezing season
« Reply #424 on: October 19, 2018, 04:59:59 AM »
Hey, that's a cool animation, could you extend it to start few days (say 4) days earlier and end in about 4-7 more?
After 4-7 days, of course. I saved single images since June 8.
Great, looking at the patterns of ice growth over all the marginal Seas could be illuminating.

litesong

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Re: The 2018/2019 freezing season
« Reply #425 on: October 19, 2018, 02:02:53 PM »
....the gap to the present "2010's Arctic sea ice" average widening again to 440,000 square kilometers LESS.
.....2018 Arctic sea ice is 550,000 square kilometers LESS than the to-date "2010's sea ice average". 2018 now has more to-date sea ice than ONLY the year 2012, which had a spectacular loss of sea ice, much going away due to fortuitous winds that drove ices into the North Atlantic.
To-date 2018 Arctic sea ice is 720,000 square kilometers LESS than the to-date "2010's sea ice average".
To-date 2018 Arctic sea ice is three quarters  of a million square kilometers LESS than the to-date "2010's sea ice average".

uniquorn

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Re: The 2018/2019 freezing season
« Reply #426 on: October 19, 2018, 02:14:04 PM »
ESS coastal refreeze, Worldview, oct19  https://tinyurl.com/ybgwuykd

uniquorn

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Re: The 2018/2019 freezing season
« Reply #427 on: October 19, 2018, 02:21:44 PM »
ESRL ice and snow thickness forecast, oct17-24. Steady pack expansion and Alaskan, ESS and Laptev coastal ice growth over the next week. (Missed the Beaufort flash freeze though)


It's strange alright that ESRL did not pick up on the sudden changes in the more western Beaufort.

Here is the NSIDC view on Oct 17th. That Beaufort blob does look remarkable, compared with the image 3 days earlier.
That new ice is very thin. The NSIDC resolution may be exaggerating the change a little. ;)

edit: The old ice line north of Severnaya Zemlya. amsr2-uhh oct18, polarview oct19
« Last Edit: October 19, 2018, 04:06:53 PM by uniquorn »

seaice.de

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Re: The 2018/2019 freezing season
« Reply #428 on: October 19, 2018, 04:38:28 PM »
That new ice is very thin. The NSIDC resolution may be exaggerating the change a little. ;)

Indeed, have a look at SMOS data. Ice thickness calculation resumed after the melting pause.

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Re: The 2018/2019 freezing season
« Reply #429 on: October 19, 2018, 04:44:36 PM »
"For my part, whatever anguish of spirit it may cost, I am willing to know the whole truth; to know the worst and provide for it." - Patrick Henry

Sarat

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Re: The 2018/2019 freezing season
« Reply #430 on: October 19, 2018, 04:51:47 PM »
Is there a resource that catalogues the Northeast Passage opening and closing dates?

Is this year a record long open?

FishOutofWater

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Re: The 2018/2019 freezing season
« Reply #431 on: October 19, 2018, 05:18:27 PM »
The SMOS data are concerning. The thickest ice continues to decline to record low amounts. That means we are at a record low ice volume for the date, by a good margin, if SMOS is correct.

The PIOMAS mid month update showed 2018 volume above 2012 and pretty much tied with the other contenders for low volume, so there is apparently modest disagreement in volume estimates. Most likely that's because PIOMAS has more volume this year in the greater than 1m thick region in the central Arctic basin.
« Last Edit: October 19, 2018, 05:25:21 PM by FishOutofWater »

vox_mundi

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Re: The 2018/2019 freezing season
« Reply #432 on: October 19, 2018, 06:05:55 PM »
Air Pollution Reduces Arctic Cloud Lifetime, Study Suggests

Fossil fuel emissions from Asia and Europe may be cutting down the life expectancy of Arctic clouds, reducing the clouds’ ability to regulate temperatures in the polar region, according to new research.

A new study published in Geophysical Research Letters, a journal of the American Geophysical Union, suggests pollution plumes coming predominately from Northeast Asia and Northern Europe travel to the Arctic region and allow cloud droplets to freeze at higher temperatures.

This phenomenon triggers earlier than normal snowfall and can reduce the clouds’ lifetime, according to the new research.  The shorter the clouds live, the less they are able to regulate temperatures at the surface, the study’s authors said.


Pollution plume from Siberia mixing with clouds in the Arctic in July 2012. Contour lines indicate carbon monoxide concentrations. (Carbon monoxide is used as a proxy for air pollution) Ice clouds appear blue and liquid clouds appear white and gray. Credit: NASA and Quentin Coopman

Previous research conducted by Coopman and his colleagues showed Arctic cloud properties are extremely sensitive to pollution. They found clouds in the Arctic were two to eight times more sensitive to air pollution than clouds at other latitudes.

The new study’s results suggest pollution plumes lower the amount of cooling needed for cloud droplets to freeze by about 4 degrees Celsius (7.2 degrees Fahrenheit), a much stronger impact than expected, Coopman said. This means cloud droplets can freeze at higher temperatures. When cloud droplets freeze more readily, snowfall occurs sooner, which can decrease the clouds’ lifetimes and inhibits their ability to regulate temperatures at the surface, according to the study’s authors.

The new study did not examine how much this change in cloud formation is affecting surface temperatures but the study’s authors said previous work suggests a reduction of cloud lifetime would have an overall cooling effect on the surface and a warming effect in the upper atmosphere.


Q. Coopman et.al. Evidence for Changes in Arctic Cloud Phase Due to Long‐Range Pollution Transport Geophysical Research Letters, 21 September 2018

Quote
Abstract
Reduced precipitation rates allow pollution within air parcels from midlatitudes to reach the Arctic without being scavenged. We use satellite and tracer transport model data sets to evaluate the degree of supercooling required for 50% of a chosen ensemble of low‐level clouds to be in the ice phase for a given meteorological regime. Our results suggest that smaller cloud droplet effective radii are related to higher required amounts of supercooling but that, overall, pollution plumes from fossil fuel combustion lower the degree of supercooling that is required for freezing by approximately 4 °C. The relationship between anthropogenic plumes and the freezing transition temperature from liquid to ice remains to be explained.

Plain Language Summary
Anthropogenic pollution plumes from midlatitudes can be transported long distances to the Arctic. In this study, we analyze the impact of these plumes on how easily liquid clouds over the Arctic Ocean freeze by using a novel combination of satellite measurements and a pollution transport model. We find that liquid clouds in polluted air switch phase to become ice clouds at temperatures that are 4 °C higher they would otherwise in pristine air. Because ice clouds in the Arctic precipitate more easily than liquid clouds, the potential is that distant industrial pollution sources are acting to reduce arctic cloud life time.
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Tor Bejnar

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Re: The 2018/2019 freezing season
« Reply #433 on: October 19, 2018, 06:23:54 PM »
Noticing that the DMI 80N temp (sorry A-Team) has been hovering vaguely around -10º C, I wonder if the observed (reported on these threads) 'sea water functionally doesn't freeze until the air reaches -10' meme is related (heat of formation and all that physical chemistry stuff that I don't know anything about).
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uniquorn

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Re: The 2018/2019 freezing season
« Reply #434 on: October 19, 2018, 07:38:32 PM »
Couldn't resist comparing SMOS and 0m salinity.

oren

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Re: The 2018/2019 freezing season
« Reply #435 on: October 19, 2018, 08:11:31 PM »
Couldn't resist comparing SMOS and 0m salinity.
I used to be more agile with my animations, but can you or anyone compare SMOS to PIOMAS (from Wipneus' animation) for Oct 15th? If it's technically possible.

magnamentis

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Re: The 2018/2019 freezing season
« Reply #436 on: October 19, 2018, 08:44:24 PM »
Bremen has 2018 lowest for this date.

https://seaice.uni-bremen.de/data/amsr2/today/extent_n_running_mean_amsr2_previous.png

2007 is missing in that graph as far as i can see which is the real lowest at this date of the year if i'm not totally mistaken

uniquorn

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Re: The 2018/2019 freezing season
« Reply #437 on: October 19, 2018, 11:02:30 PM »
Couldn't resist comparing SMOS and 0m salinity.
I used to be more agile with my animations, but can you or anyone compare SMOS to PIOMAS (from Wipneus' animation) for Oct 15th? If it's technically possible.
not this late ona friday noght =

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Re: The 2018/2019 freezing season
« Reply #438 on: October 20, 2018, 03:32:06 AM »
Much is said about the "heat wave" in the High Arctic. But, the entire continent of Asia is warm too, with only very small areas of any coolness. The Asian heat slides into Europe & even continues south, over the islands of the Pacific & to Australia. 

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Re: The 2018/2019 freezing season
« Reply #439 on: October 20, 2018, 07:16:21 AM »
October 15-19.

oren

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Re: The 2018/2019 freezing season
« Reply #440 on: October 20, 2018, 08:34:10 AM »
October 15-19.
Thanks as always for this animation.
The good news is that first signs of actual freezing have finally appeared as offshoots from the pack on the Atlantic front, and even on the Laptev front. Better late than never.

sark

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Re: The 2018/2019 freezing season
« Reply #441 on: October 20, 2018, 09:16:29 AM »
in the long range forecast, (this is all the way out to November 4th) GFS expects increased Arctic heat anomalies.  climate reanalyzer shows up to +5.8C in the Arctic zone.  really pronounced warm Arctic with two colder regions on land.  this is bigger than October of 2016 in terms of DMI 80N.

10mb center starts to move towards greenland as well.
« Last Edit: October 20, 2018, 09:27:20 AM by sark »

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Re: The 2018/2019 freezing season
« Reply #442 on: October 20, 2018, 11:31:05 AM »
Noticing that the DMI 80N temp (sorry A-Team) has been hovering vaguely around -10º C, I wonder if the observed (reported on these threads) 'sea water functionally doesn't freeze until the air reaches -10' meme is related (heat of formation and all that physical chemistry stuff that I don't know anything about).
I have a vague memory that there was a study that suggested temps had to drop below -10 celsius for sea ice to form in the Arctic ocean. This has been repeated so often that it seems to have become the generally accepted conventional wisdom. I have my doubts.

I can see no reason why in a calm sea, and with the sea having lost most of its accumulated summer heat, ice cannot form at air temperatures a bit below -1.8. There is ice forming here and there on the Arctic fringes, and I doubt everywhere is at -10 or below.

I am expecting to be shot down. But is the proof out there?
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Niall Dollard

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Re: The 2018/2019 freezing season
« Reply #443 on: October 20, 2018, 11:32:18 AM »
in the long range forecast, (this is all the way out to November 4th) GFS expects increased Arctic heat anomalies.  climate reanalyzer shows up to +5.8C in the Arctic zone.  really pronounced warm Arctic with two colder regions on land.  this is bigger than October of 2016 in terms of DMI 80N.

10mb center starts to move towards greenland as well.

Yeah. During September a lot of the focus here has been on the warmth coming up from the ATL and PAC fronts (and justifiably so) but this autumn the CAB is further compromised by very warm record breaking heat from Asia.
A favoured path was warmth from the chukchi running right across the top of Russia then turning right bringing further heat over the pole.
The Russian snow cover has been slow too and coupled with the very large open sea area in the Laptev the DMI N80 will struggle for a considerable time yet.
The Russian snow is beginning to develop now and there are small signs of ice developing along the north Russian coast, but it is going to take a few weeks yet before the warm Laptev is sealed off.

Niall Dollard

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Re: The 2018/2019 freezing season
« Reply #444 on: October 20, 2018, 11:46:53 AM »

I have a vague memory that there was a study that suggested temps had to drop below -10 celsius for sea ice to form in the Arctic ocean. This has been repeated so often that it seems to have become the generally accepted conventional wisdom. I have my doubts.

I can see no reason why in a calm sea, and with the sea having lost most of its accumulated summer heat, ice cannot form at air temperatures a bit below -1.8. There is ice forming here and there on the Arctic fringes, and I doubt everywhere is at -10 or below.

I am expecting to be shot down. But is the proof out there?

The Russian scientist Vladamir Vize ( the island was called after him ) was the Godfather of ice formation. There is a rather scary looking picture of him here on Wiki !

https://en.m.wikipedia.org/wiki/Vladimir_Wiese

Maybe earlier in the season temps close to -10 are needed to get things going but nilas will form with air temps at -7.
IIRC the recent thin new ice that formed in the western Beaufort temps were not much lower than -7 C (according to nullschool)

johnm33

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Re: The 2018/2019 freezing season
« Reply #445 on: October 20, 2018, 02:17:29 PM »
G, "I have my doubts." me too, here's Waynes post

Sterks

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Re: The 2018/2019 freezing season
« Reply #446 on: October 20, 2018, 02:50:36 PM »
G, "I have my doubts." me too, here's Waynes post
Wayne's assertion that you must have hace -1.8C water  and -11C surface temperatures is scientifically wrong. By thermodynamics, the water, the interface, and the air immediate to it must be at the same temperature. The other is alternative facts, or fake science, as bad as those that some deniers use to push fanatically or ignorantly or both their arguments.

Let’s keep respect to 200-year-old established science at least, even when current scientific work may not be all well established yet.

Another thing is the 2m temperatures that the weather forecast may provide which may substantially be lower. But I doubt that the -10C threshold sustained for days as a rule of thumb is correct, except in specific conditions. Certainly the 80N temp DMI is no indicator of anything of the Arctic proper in general.

gerontocrat

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Re: The 2018/2019 freezing season
« Reply #447 on: October 20, 2018, 05:50:36 PM »
G, "I have my doubts." me too, here's Waynes post
Wayne's post
Quote
New sea ice starts from 3 important concurring factors: -1.8 C water, little or no sea waves and colder than -11 C surface temperatures....

...  there is an apparent thermal balance,  where as,  colder than -11 C  surface air seems imperative for sea ice to form.WD October 4, 2016   

Where did he get that from? I tried to find out and failed, but I found some nice stuff on NSIDC for amateurs like me, and put the Lebedev formula into a simple spreadsheet -

https://nsidc.org/cryosphere/seaice/processes/thermodynamic_growth.html
Quote
The freezing temperature of ocean (saline) water is typically -1.8 degrees Celsius (28.7 degrees Fahrenheit). If the average daily temperature was -5.8 degrees Celsius (21.6 degrees Fahrenheit), this would be -4 degrees Celsius (24.8 degrees Fahrenheit) for one day, as the following equation shows:

(-1.8) - (-5.8) = 4 degrees below freezing

4 degrees below freezing, Day 1 = 4 cumulative FDD
7 degrees below freezing, Day 2 = 11 cumulative FDD
2 degrees above freezing, Day 3 = 9 cumulative FDD

Scientists have developed different formulas to estimate ice thickness from thermodynamic growth, using the FDD. One such formula (from Lebedev 1938) is:

Thickness (cm) = 1.33 * FDD (°C)0.58

The ice thickness increases at a rate roughly proportional to the square root of the cumulative FDD. Formulas such as this are empirical, meaning they are calculated only with observed data, so they really are simplifications of the ice growth processes. The formulas assume that the ice growth occurs in calm water and is reasonably consistent, and they do not take into account sea ice motion, snow cover, and other surface conditions.

Snow cover is one factor that dramatically alters the actual sea ice thickness calculated from the above formula. Snow is an effective insulator, slowing the transfer of heat from the ocean, through the ice, and to the atmosphere. Snow essentially slows the growth of ice.

And then we have The Northern Caspian Sea - https://core.ac.uk/download/pdf/77008517.pdf
Quote
Sensitivity of Caspian sea-ice to air temperature
Helen Tamura-Wicks a∗ Ralf Toumi a and W. Paul Budgell
Space and Atmospheric Physics Group, Imperial College London, UK
Institute of Marine Research, Bergen, Norway

Caspian sea ice concentration from satellite passive microwave data and surface
daily air temperatures are analysed from 1978 to 2009. Relationships between
mean winter air temperatures, cumulative freezing degree days (CFDD) and
the sum of daily ice area (cumulative ice area) are found. These show that
mean monthly air temperatures of less than 5.5 to 9.5◦C, and a minimum
CFDD of 3.6±11.2◦C, is required for ice formation in the Northern Caspian.

So far -11 degrees for sea ice formation looks like a load of....

Cumulative FDDs look much more like it (and of course any remaining ocean heat and upwelling etc etc etc).

How come we only have FDDs for North of 80? An FDD series for individual seas would seem to be a somewhat useful tool.
ps
"Para a Causa do Povo a Luta Continua!"
"And that's all I'm going to say about that". Forrest Gump
"Damn, I wanted to see what happened next" (Epitaph)

litesong

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Re: The 2018/2019 freezing season
« Reply #448 on: October 20, 2018, 05:58:18 PM »
.... a study that suggested temps had to drop below -10 celsius for sea ice to form in the Arctic ocean. This has been repeated so often that it seems to have become the generally accepted conventional wisdom. I have my doubts.
I quote from my post two days ago in this thread:
"During this time of year when Arctic sea ice rapidly increases, there are very very few short periods of Arctic sea ice DECREASES. Yet, 2016 had two distinct periods of sea ice decrease, both losing periods occurring when 1) High Arctic temperature over millions of square kilometers  was 20(+?) degC above average & 2) High Arctic temperature over millions of square kilometers was ~ 16degC above average."

Phil.

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Re: The 2018/2019 freezing season
« Reply #449 on: October 20, 2018, 06:38:04 PM »
My recollection is that it was the result of Wayne's own observations, he lives somewhere up in the Archipelago?  The ice thickness growth formula needs some surface ice to work with, surface ice will start to form once a stable density gradient is set up so there will be a delay while that occurs.  My guess is that the observation of the -10ºC is related to a heat transfer effect, bigger deltaT faster heat transfer.