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Paul

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Re: The 2021 melting season
« Reply #250 on: April 16, 2021, 11:49:22 PM »
NSIDC Sea Ice Comparison Tool

To add a little to BFTV's post...
And to add a bit more,


Strikingly similar patterns, except pacific side is ahead big-time. Apply 2012-like melt season to this - results would be nothing short of extreme.

Does not always work out like that though and besides 2 melt seasons are never quite the same.

I do feel given how the CAB is probably less thick than usual, low pressure systems could be more damaging for the ice long term and we could see more dispersion like we saw in years 2012, 2013, 2016 and 2017 in the CAB.

Jim Hunt

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Re: The 2021 melting season
« Reply #251 on: April 17, 2021, 12:45:57 AM »
After a couple of modest upticks AMSR2 area is still (just!) lowest for the date.

However as you have probably been able to surmise, compaction (or rather lack thereof) is firmly in 1st place at the moment:

Edit - Now with appropriate Y axis label!
« Last Edit: April 17, 2021, 11:38:30 AM by Jim Hunt »
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charles_oil

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Re: The 2021 melting season
« Reply #252 on: April 17, 2021, 09:56:58 AM »
Thanks for these -


Shouldn't the graph scale read "% compaction" on the vertical axis or "Area/Extent %" ?

Aluminium

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Re: The 2021 melting season
« Reply #253 on: April 17, 2021, 10:02:17 AM »
April 11-16.

2020.

Aluminium

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Re: The 2021 melting season
« Reply #254 on: April 17, 2021, 10:46:51 AM »
According to measurements in Cape Vankarem and Uelen, dew point exceeded -1.8°C. In Uelen, measured snow cover fell from 46 cm to 29 cm in 1 day.

Jim Hunt

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Re: The 2021 melting season
« Reply #255 on: April 17, 2021, 11:33:59 AM »
Shouldn't the graph scale read "% compaction" on the vertical axis or "Area/Extent %" ?

It should indeed. Unfortunate cut'n'paste malfunction!

It will be corrected in the near future.
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uniquorn

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Re: The 2021 melting season
« Reply #256 on: April 17, 2021, 01:55:39 PM »
According to measurements in Cape Vankarem and Uelen, dew point exceeded -1.8°C. In Uelen, measured snow cover fell from 46 cm to 29 cm in 1 day.
Thanks Aluminium, so those max temps making a big difference to snow depth in Uelen. Average daylight in April of 15.6h.

Some refreeze in the Barents recently, awi amsr2 v104, apr12-17
https://go.nasa.gov/3uXdpf1,  slight adaptive contrast.

« Last Edit: April 17, 2021, 02:18:55 PM by uniquorn »

El Cid

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Re: The 2021 melting season
« Reply #257 on: April 17, 2021, 05:47:55 PM »
According to measurements in Cape Vankarem and Uelen, dew point exceeded -1.8°C. In Uelen, measured snow cover fell from 46 cm to 29 cm in 1 day.

Isnt this just snow compaction, ie. fluffy snow becoming more dense? You don't have real melt at those temperatures, do you?

Aluminium

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Re: The 2021 melting season
« Reply #258 on: April 17, 2021, 06:10:27 PM »
Isnt this just snow compaction, ie. fluffy snow becoming more dense? You don't have real melt at those temperatures, do you?
I think, persistent southerlies (10-20 m/s) did most of it. However, -1.8°C is just a threshold for the ice. It was exceeded in two points, 320 km one from other. Actual temperatures were positive and some melting is quite possible.

gerontocrat

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Re: The 2021 melting season
« Reply #259 on: April 17, 2021, 06:24:09 PM »
According to measurements in Cape Vankarem and Uelen, dew point exceeded -1.8°C. In Uelen, measured snow cover fell from 46 cm to 29 cm in 1 day.

Isnt this just snow compaction, ie. fluffy snow becoming more dense? You don't have real melt at those temperatures, do you?
Meteoblue shows mid-week some full on sunny days with daytime temps approaching 5 celsius, but still well below freezing at night. (Then after Saturday weather goes horrible )

I don't know what the weather was recently - especially sunshine hours.

How much real melt & how much compaction? Je ne sais pas. I guess a good many scientists are still working on that equation. I guess that does mean Chukchi sea ice is vulnerable in that area.

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Aluminium

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Re: The 2021 melting season
« Reply #260 on: April 17, 2021, 06:57:40 PM »
How much real melt & how much compaction?
There is a third possible component. Winds can push snow away from where it measured.

solartim27

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Re: The 2021 melting season
« Reply #261 on: April 17, 2021, 09:02:52 PM »
How much real melt & how much compaction?
There is a third possible component. Winds can push snow away from where it measured.
Don't forget sublimation as well
FNORD

uniquorn

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Re: The 2021 melting season
« Reply #262 on: April 17, 2021, 09:42:16 PM »
For anyone interested in near real time ice thickness in the Beaufort/Chukchi, cryosphere innovation have 7 active SIMB buoys. (maybe 6)

Today's data from the Chukchi coast shown.

Jim Hunt

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Re: The 2021 melting season
« Reply #263 on: April 18, 2021, 01:16:59 AM »
Cryosphere Innovation have 7 active SIMB buoys.

Thanks, I hadn't spotted that. I wasn't expecting the deployment of 5 buoys in March!

A useful side effect of the Sea Ice Dynamics Experiment (SIDEx for short):

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Vince O

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Re: The 2021 melting season
« Reply #264 on: April 18, 2021, 03:34:54 AM »
The central pack seems to be breaking away from the Siberian side. a crack right along the ESS to the far side of the Laptev. Been opening up for four or five days now

https://worldview.earthdata.nasa.gov/?v=-1623107.735841838,1079256.464039864,364271.4674407155,2071412.5940736695&p=arctic&t=2021-04-17-T02%3A32%3A11Z

Would be nice to know what is going on underneath the ice not just above. I know there are bouys indicating surface movement but is there any way of tracking the currents below. sorry my ignorance. I have seen before someone linking to something mentioning the vertical columns being disrupted but can't remember anything else.  I would be interested in any links as I think more and more what is happeneing below will over ride what happens above. Maybe sooner than later.
   And as to my post before. I would prob normally said extent instead of area but with 5 mins to go to work and 8.30 am finesse isn't my strong point lol !

Aluminium

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Re: The 2021 melting season
« Reply #265 on: April 18, 2021, 07:57:08 AM »
In Uelen, measured snow cover fell from 46 cm to 29 cm in 1 day.
It's back to 54 cm next day. :) Without significant precipitation.

El Cid

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Re: The 2021 melting season
« Reply #266 on: April 18, 2021, 08:18:04 AM »
In Uelen, measured snow cover fell from 46 cm to 29 cm in 1 day.
It's back to 54 cm next day. :) Without significant precipitation.

MAGIC!

(or the wind pushing it around as you said...)

Aluminium

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Re: The 2021 melting season
« Reply #267 on: April 18, 2021, 09:18:47 AM »
If this table is correct, 10-20 m/s winds can move up to 0.4 kg/(m*s) of snow.

nadir

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Re: The 2021 melting season
« Reply #268 on: April 18, 2021, 11:09:01 AM »
The central pack seems to be breaking away from the Siberian side. a crack right along the ESS to the far side of the Laptev. Been opening up for four or five days now

https://worldview.earthdata.nasa.gov/?v=-1623107.735841838,1079256.464039864,364271.4674407155,2071412.5940736695&p=arctic&t=2021-04-17-T02%3A32%3A11Z

Would be nice to know what is going on underneath the ice not just above. I know there are bouys indicating surface movement but is there any way of tracking the currents below. sorry my ignorance. I have seen before someone linking to something mentioning the vertical columns being disrupted but can't remember anything else.  I would be interested in any links as I think more and more what is happeneing below will over ride what happens above. Maybe sooner than later.
   And as to my post before. I would prob normally said extent instead of area but with 5 mins to go to work and 8.30 am finesse isn't my strong point lol !

This is a very frequent sight this time of the year, the crack usually reveals the mobile pack drifting while the fast ice (ice fastened to the coast) remains static.

It happens in winter too but the ice is colder and less mobile, cracks refreeze, snows cover cracks, and there is no oblique sunlight to easily reveal them.

BornFromTheVoid

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Re: The 2021 melting season
« Reply #269 on: April 18, 2021, 11:31:14 AM »
This weeks slow sea ice animation Losses across the Pacific side of the Arctic almost balanced out by a large wind-driven increase east of Svalbard. We can see the first signs of melt in Hudson Bay also & large leads opening along the Siberian side - sign of a very mobile central pack.
(click to play)
I recently joined the twitter thing, where I post more analysis, pics and animations: @Icy_Samuel

Pagophilus

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Re: The 2021 melting season
« Reply #270 on: April 18, 2021, 08:01:32 PM »
This weeks slow sea ice animation Losses across the Pacific side of the Arctic almost balanced out by a large wind-driven increase east of Svalbard. We can see the first signs of melt in Hudson Bay also & large leads opening along the Siberian side - sign of a very mobile central pack.
(click to play)

Well put -- the central pack from your animation has the feel of a loose tooth about it.  The wind-driven extent increase E of Svalbard represents low concentration ice moving out to speedy doom in the Barents Sea, so in a way that ice extent gain is a soon-to-be-loss.  There has been much discussion about Fram export being potentially notably large -- does anyone know what Fram export has been like over the past two weeks?  I could not find data.   
You may delay, but time will not.   Benjamin Franklin.

Jim Hunt

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Re: The 2021 melting season
« Reply #271 on: April 18, 2021, 09:08:55 PM »
Does anyone know what Fram export has been like over the past two weeks?   

Wipneus will reveal all when (if?) the mid month PIOMAS gridded thickness numbers are released.

Here's the March 31st edition:

https://forum.arctic-sea-ice.net/index.php/topic,119.msg304896.html#msg304896

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be cause

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Re: The 2021 melting season
« Reply #272 on: April 18, 2021, 09:11:15 PM »
Sorry Pagophilus , no data , but I've tracked a floe for a total of 280km since 18.03 including 170km between 02.04 and 17.04 . Obscured today (and there is some reversal of flow today) . Yesterday it could be seen at 83.10 N 14'W on worldview , nearly 3' S of it's location a month ago . b.c.
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uniquorn

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Re: The 2021 melting season
« Reply #273 on: April 19, 2021, 12:51:38 AM »
ascat, atlantic side, day58-107

oren

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Re: The 2021 melting season
« Reply #274 on: April 19, 2021, 02:36:16 AM »
ascat, atlantic side, day58-107
Thanks for this.
It seems export from the heartland of the CAB, Greenland to the Pole, is still not as bad as it was in Feb-Mar 2020 when the entire section was pulled east in a sustained manner towards the Fram. However with the thick ice some of the models/sensors claim to be poised above the exit this year, some serious damage may have been done already. I am still waiting for the pattern to stop or reverse, the longer it continues the worse it becomes.

Jim Hunt

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Re: The 2021 melting season
« Reply #275 on: April 19, 2021, 08:54:32 AM »
ascat, atlantic side, day58-107

Thanks very much uniquorn.

Saves my alter ego lots of time!

https://twitter.com/GreatWhiteCon/status/1384037172005588992

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Note that the North Pole is now close to the edge of the remaining multi-year ice.
"The most revolutionary thing one can do always is to proclaim loudly what is happening" - Rosa Luxemburg

Jim Hunt

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Re: The 2021 melting season
« Reply #276 on: April 19, 2021, 10:45:26 AM »
Wipneus's mid April modelled Fram export graph has arrived. All that and much more at:

https://GreatWhiteCon.info/2021/03/the-2021-maximum-arctic-sea-ice-volume/#Apr-19

Quote
The mid month PIOMAS gridded thickness data has arrived, and also reveals an initial early peak in Arctic sea ice volume this year, and hence an increasingly negative anomaly.

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Killian

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Re: The 2021 melting season
« Reply #277 on: April 19, 2021, 03:51:23 PM »
Is it my imagination or did we see over 100k sq. km of sea ice exit the central basin via Fram duirng April? I used the Worldview area function to estimate the area of ice north of the Fram that went zipping out between the shoulder of Greenland and northwestern Svalbard.

jdallen

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Re: The 2021 melting season
« Reply #278 on: April 19, 2021, 07:00:11 PM »
How much real melt & how much compaction?
There is a third possible component. Winds can push snow away from where it measured.
Don't forget sublimation as well
Very much so, especially with those wind speeds.  It's quite dry overall - the precipitable water in the air column is less than 15 kg/m2, so mixing would carry moisture away quite rapidly.  The phase change would also tend to keep the 2m temperature between -1.8c & 0.  I've glanced at studies which indicate 3-40% of snow pack (not just Arctic) can be lost directly to sublimation over winter and during spring melt.
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oren

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Re: The 2021 melting season
« Reply #279 on: April 19, 2021, 07:43:53 PM »
Is it my imagination or did we see over 100k sq. km of sea ice exit the central basin via Fram duirng April? I used the Worldview area function to estimate the area of ice north of the Fram that went zipping out between the shoulder of Greenland and northwestern Svalbard.
As at least one floe was tracked along 280km over several weeks (upthread I think), and considering the width of the exported front is several hundred kilometers, your estimate makes sense.

gerontocrat

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Re: The 2021 melting season
« Reply #280 on: April 19, 2021, 08:38:33 PM »
Is it my imagination or did we see over 100k sq. km of sea ice exit the central basin via Fram duirng April? I used the Worldview area function to estimate the area of ice north of the Fram that went zipping out between the shoulder of Greenland and northwestern Svalbard.
As at least one floe was tracked along 280km over several weeks (upthread I think), and considering the width of the exported front is several hundred kilometers, your estimate makes sense.
I tried some arithmetic

Looking at Wipneus' Fram Export graph suggests an average export volume rate of about 0.4 thousand km3 per month for the first half of April. i.e. 200 km3 (say) left the building.

1 km3 of ice at 1 metre thick covers 1,000 km2.
So if the average ice thickness exported was 2 metres, total area exported would be 500 x 200 = 100,000 km2.

Arithmetic rules again, OK?
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pearscot

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Re: The 2021 melting season
« Reply #281 on: April 19, 2021, 09:19:23 PM »
Wow the export out of the Fram today is impressive and has been for a while now. I tried to make this as compact as possible, but hopefully this more clearly illustrates the power of the wind and how quickly it has moved the ice around. According to windy, winds are ripping thru the strait at around 40kt.

pls!

miki

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Re: The 2021 melting season
« Reply #282 on: April 20, 2021, 01:28:37 AM »
Wow the export out of the Fram today is impressive and has been for a while now. I tried to make this as compact as possible, but hopefully this more clearly illustrates the power of the wind and how quickly it has moved the ice around. According to windy, winds are ripping thru the strait at around 40kt.

... and that fast ice north of Greenland crumbling like a cookie!

Aluminium

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Re: The 2021 melting season
« Reply #283 on: April 20, 2021, 09:36:50 AM »
April 14-19.

2020.

OffTheGrid

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Re: The 2021 melting season
« Reply #284 on: April 20, 2021, 11:33:22 AM »
Wow the export out of the Fram today is impressive and has been for a while now. I tried to make this as compact as possible, but hopefully this more clearly illustrates the power of the wind and how quickly it has moved the ice around. According to windy, winds are ripping thru the strait at around 40kt.

Impressive indeed.
The apparent lack of inertia dampening the acceleration..
The surge of not just ice but entrained fresh surface lens.

IMHO speaks gratuitous of the lack of drag from deep keeled texture. Or cohesion. Suppose this to be expected with nowhere Atlantic side of the Lomonosov now experience anything but bottom melt thru winter due to the galloping atlantification .

<Vulcanism discussion removed. O>
« Last Edit: April 20, 2021, 12:09:01 PM by oren »

gerontocrat

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Re: The 2021 melting season
« Reply #285 on: April 20, 2021, 02:18:08 PM »
It is conventional wisdom to treat any weather forecasts for the Arctic of over 5 days forward with a bucket of salt. On the other hand some scientists suggest that AGW + polar amplification have weakened the polar vortex, one consequence of which is large slowly meandering Rossby waves of the jet stream that can mean that weather systems, once entrenched, can last for a long time.

This has happened in the UK for the last week, with a high pressure system that is now forecasted to last until at least the 3rd May. Until now that encouraged Atlantic lows to travel up into the Norwegian sea and beyond.

BUT now the UK high has joined forces with the Greenland high to block Atlantic weather from travelling North into the Barents. It also looks like that this will persist and strengthen. So are we in for a new Arctic weather pattern for some time (not just on the Atlantic Front)?

Consequences? I don't really know, except that it looks like the Baffin is going to get a lot warmer, and significant melt could occur on the coasts of Greenland.

I attach a gif of the 3, 5 & 10 day average MSLP. If nothing else the pictures are pretty.

click to start
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Shared Humanity

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Re: The 2021 melting season
« Reply #286 on: April 20, 2021, 02:24:01 PM »
some scientists suggest that AGW + polar amplification have weakened the polar vortex, one consequence of which is large slowly meandering Rossby waves of the jet stream that can mean that weather systems, once entrenched, can last for a long time.

I absolutely believe the scientists that argue polar amplification and the decline in temperature gradient between the equator and the pole results in sticky weather. This is why we see more persistent and extreme weather.

Tor Bejnar

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Re: The 2021 melting season
« Reply #287 on: April 20, 2021, 04:08:15 PM »
The name Jennifer Francis should jump to everybody's mind when reading the above, e.g.:
   Jennifer A. Francis, Natasa Skific, Stephen J. Vavrus.
   North American weather regimes are becoming more persistent: Is Arctic amplification a factor?
   Geophysical Research Letters, 2018; DOI: 10.1029/2018GL080252
or read the Science Daily version.
Arctic ice is healthy for children and other living things because "we cannot negotiate with the melting point of ice"

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Re: The 2021 melting season
« Reply #288 on: April 20, 2021, 08:10:42 PM »
If this table is correct, 10-20 m/s winds can move up to 0.4 kg/(m*s) of snow.
Well, correct or not - there is even simpler way to be sure. Yep, 20 m/s winds can move helluva lot of snow real quick.

Because, if one ever lived anywhere near polar circle, and if one ever happened to drive a bike around (or just put a hand outta car's window on the move) - that's already enough. 20 m/s is 72 km/h (45 mph), and feels quite strong a wind - more than strong enough to move massive amounts of snow.

Russians call it "v'yuga", which i don't think has any good english word equivalent. Basically, "v'yuga" means winter weather with wind strong enough to lift so much snow in the air that visibility is massively reduced - so much that russian peasants in the old times had difficulty doing their winter time things like going from their house to their barn and back, getting some firewood, fetching water from nearby well, etc.

I've seen hundreds of "v'yugas" - and their consequences. The most common of which - is big snow piles, often meters high, "here and there" over the landscape. Not unlike dunes in a desert.
To everyone: before posting in a melting season topic, please be sure to know contents of this moderator's post: https://forum.arctic-sea-ice.net/index.php/topic,3017.msg261893.html#msg261893 . Thanks!

Jim Hunt

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Re: The 2021 melting season
« Reply #289 on: April 21, 2021, 02:01:35 AM »
Via Ann Daniels on Twitter:

https://twitter.com/AnnDanielsGB/status/1380419350117675010

Quote
I just heard an icetracking buoy I deployed at the North Pole in April 2018 has reached Iceland and is still transmitting data. To be able to help knowledgeable people understand this amazing planet of ours fills me with joy.

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BornFromTheVoid

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Re: The 2021 melting season
« Reply #290 on: April 21, 2021, 09:08:39 AM »
Via Ann Daniels on Twitter:

https://twitter.com/AnnDanielsGB/status/1380419350117675010



That's a nice demonstration of the currents that used to produce the Odden ice tongue
I recently joined the twitter thing, where I post more analysis, pics and animations: @Icy_Samuel

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Re: The 2021 melting season
« Reply #291 on: April 21, 2021, 06:34:15 PM »
Hi Oren and BFTV,

Given that the N Pole is permanently frozen, does this mean that the buoy got there by the complete ice sheet moving ?

BornFromTheVoid

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Re: The 2021 melting season
« Reply #292 on: April 21, 2021, 07:00:27 PM »
Hi Oren and BFTV,

Given that the N Pole is permanently frozen, does this mean that the buoy got there by the complete ice sheet moving ?

Hi Jontenoy. There is always some ice there but it's not always fully frozen over. This is especially noticeable during summer and autumn when you can see many large gaps in between individual ice floes, which are also highly mobile so they can move about a lot.
So some of the floes move away from the N. Pole, other floes move in from elsewhere to replace them and new ice also forms from freezing.
I recently joined the twitter thing, where I post more analysis, pics and animations: @Icy_Samuel

johnm33

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Re: The 2021 melting season
« Reply #293 on: April 21, 2021, 07:52:59 PM »
Hi Oren and BFTV,

Given that the N Pole is permanently frozen, does this mean that the buoy got there by the complete ice sheet moving ?
Or to put it another way the ice sheet tends to expand from it's center, which is towards Alaska from the pole, and to fill the voids with fresh ice when gaps open. The Atlantic front has gaps opening more often due to both incoming Atl. waters and outoing Arctic ice so the ice, near the pole, expands towards Barents, then gets caught up in the general exit through Fram.

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Re: The 2021 melting season
« Reply #294 on: April 21, 2021, 11:03:05 PM »
A little speculation, looking at amsr2 below I wonder if the bottom melt[?] in Beaufort is caused by incoming Pacific water. For it to be moving at that pace suggests practically zero resistance, maybe even some assist either by a large shift in near surface waters to the Atlantic side or by a swift exit through the CAA of the same. 11th-20th
amsr2 from polarview has begun having two slightly different frames for the previous day as evidenced by the slower [double] frame before the last[x4]
« Last Edit: April 22, 2021, 09:42:44 AM by johnm33 »

Jim Hunt

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Re: The 2021 melting season
« Reply #295 on: April 21, 2021, 11:09:29 PM »
There is always some ice there but it's not always fully frozen over. This is especially noticeable during summer and autumn when you can see many large gaps in between individual ice floes, which are also highly mobile so they can move about a lot.

Photographic evidence that those "large gaps" can become "humungously large"!

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Re: The 2021 melting season
« Reply #296 on: April 22, 2021, 03:51:25 AM »
And Polarstern at the North Pole, August 2020.



Some more stuff in https://forum.arctic-sea-ice.net/index.php/topic,3280.msg284569.htm
« Last Edit: April 22, 2021, 04:01:51 AM by oren »

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Re: The 2021 melting season
« Reply #297 on: April 22, 2021, 09:24:39 AM »
Very warm air in the Chukchi Sea, ECMWF, 925 hPa.

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Re: The 2021 melting season
« Reply #298 on: April 22, 2021, 12:18:01 PM »
A little speculation, looking at amsr2 below I wonder if the bottom melt[?] in Beaufort is caused by incoming Pacific water. For it to be moving at that pace suggests practically zero resistance, maybe even some assist either by a large shift in near surface waters to the Atlantic side or by a swift exit through the CAA of the same. 11th-20th

Unlikely. There are 4 active cryosphere innovation buoys in the Beaufort and while thickening may have slowed recently, none show signs of bottom melt. Fast moving low concentration areas on AMSR2 are usually weather related interference, though they sometimes remain for some time as surface features, possibly due to freezing fog or rain.

amsr2 from polarview has begun having two slightly different frames for the previous day as evidenced by the slower [double] frame before the last[x4]
Interesting. Perhaps related to the twice daily AWI AMSR2 v104

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Re: The 2021 melting season
« Reply #299 on: April 22, 2021, 12:34:49 PM »
A fairly clear view of the ice in and around the Bering Strait, Chukchi Sea, April 21, Worldview.  Contrast pushed on Photoshop.
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