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pearscot

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Re: The 2020/2021 freezing season
« Reply #350 on: October 16, 2020, 07:40:39 PM »
One thing I would like to remark on is the substantial wave action as of late on the Siberian side of the Arctic. To me, it is extremely important and I think it will have some profound effects. I realize the below image is created with models and is not 100% accurate, however current winds in that region are substantial and I think there are some significant waves.

Completely still water only needs to cool the very surface to the sea water freezing point, however during such wind events, mixing ensures that the ENTIRE column of water must reach that temperature in order to freeze during extremely strong winds. Moreover, I believe the effects of the winds will be twofold.

First, my understanding (and is shown in the animation of the stagnation and/or slight advancement of the Laptev Bite recently), that the current weather is affecting the ice edge and either stalling the melt or causing bottom melt. I would have to imagine 19ft waves crashing into the ice edge is going to cause some significant damage.

Second, and I think more importantly, (as Tor stated), the substantial waves are promoting mixing during a time in which the sea is SUPPOSED to be covered with ice. That cool surface layer is now being agitated and is in no way helping the ever-diminishing halocline layer. I don't know the long term implications of wave action in terms of how it affects the refreeze, but for me the most concerning aspect is the constant mixing during the transition period going into winter.

I think both of these are important components and will continue to define the Arctic in the modern era. Granted I cannot prove this as fact, but it is evident how streams can continue to flow well below freezing due to the water's movement.
pls!

RoxTheGeologist

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Re: The 2020/2021 freezing season
« Reply #351 on: October 16, 2020, 07:51:33 PM »
There is enough heat in the Arctic Ocean to keep the surface functionally or literally ice-free, we are told, but much of this heat is stored beneath the halocline.  With an ice-free surface, winds will cause the upper part of the Arctic Ocean to mix, making more of this heat available to the lower atmosphere (and beyond).  Stronger winds will remove heat from the surface of the water faster, but these stronger winds will also mix more of the water column.  At some point, with continuous-enough and strong-enough winds, the halocline will disappear and 'all' of the ocean heat becomes available to be transferred to the air.  And if what we're told is true, the Arctic Ocean will cease to freeze over.  With climate change, the "-enoughs" become more and more achievable, as the speed of heat removal from the lower atmosphere to outer space slows due to the thickening CO2e blanket.

If the autumn winds are really just breezes that minimally mix the water, then the water column below the halocline remains out of the picture [the hot plate, with 200 mm of insulation on top of it, on which the tea cup sits has 'no' influence on the blown-on cup of tea].  Here, the surface water cools faster with the breeze - faster than if there is no breeze - with time that heat transfers to space, or is replaced with an 'endless' supply of cold dry air from 'elsewhere'.  So with cooled water and the heat removed from the air above the water, ice can now form.  I'm pretty sure a breeze coming off the continents in October will speed up the surface cooling, thus hastening the surface freezing.

There will always be a halocline in the Arctic because of the inputs of freshwater from the rivers and through the Bering Strait. It is almost an enclosed ocean (like the black sea or the baltic).  The depth and extent of the halocline will reduce as amplification of the halocline through the freeze/thaw distillation process is a lot less effective, and there is more mixing without ice cover.

FishOutofWater

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Re: The 2020/2021 freezing season
« Reply #352 on: October 16, 2020, 09:21:51 PM »
There's a reason that meteorologists and scientists studying climate change use complex models with multiple independent variables. If we assume that the Arctic ocean is a cup of tea, then blowing on harder it will cool it more. I mean, what's wrong with the assumption? A cup of tea is bowl shaped and so is the Arctic ocean. Well, that is a starting point, but do we really want to reinvent climate modelling starting with the assumption that the Arctic ocean is like a cup of tea?

Anyone who has lived in a cold region can tell you that strong cold winds will cool off a lake faster than a still cold night with similar temperatures but if the lake is large enough, like a great lake, temperatures rise as the winds cross the lake. In fact, intense turbulence and extreme lake effect snow can develop. So it's already not hard to see why we can't apply the simple tea cup model to the Arctic ocean. It's a complicated problem that includes the effects of water vapor and clouds on outgoing radiation. The cloud tops radiate out at a much colder temperature than the sea surface so they reduce radiational cooling.

Research has shown - see Judah Cohen's blog and publications - that open water in the Barents and Kara seas leads to displacement of the polar vortex in the fall and winter months towards the Atlantic ocean. Moreover, the vortex is weakened by the warming subpolar seas on the Atlantic side. So we have a very complex problem with multiple coupled processes when we deal with increasing release of oceanic heat from the Arctic ocean in the fall and winter months.

We have a classic case of a weak tropospheric polar vortex now. (see figure) Heat release from the Arctic ocean is contributing to the dome of warm air over the Arctic, but much of the dynamics for it came from warmer than normal waters in the North Pacific and north Atlantic.

The immediate concern we face is the increasing Atlantification of the Eurasian side of the Arctic ocean. That is relevant to the weather and ice conditions we are watching today.
« Last Edit: October 16, 2020, 09:53:37 PM by FishOutofWater »

Positive retroaction

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Re: The 2020/2021 freezing season
« Reply #353 on: October 16, 2020, 09:51:49 PM »
  leads to displacement of the polar vortex in the fall and winter months towards the Atlantic ocean. Moreover, the vortex is weakened by the warming subpolar seas on the Atlantic side. So we have a very complex problem with multiple coupled processes when we deal with increasing release of oceanic heat from the Arctic ocean in the fall and winter months.
Totaly agree
This is what is happening right now
Watch the jet stream outgrowth over Western Europe and the North East Atlantic
It's been several weeks since this has been happening without interruption, and the cold weather that it generated in France has drawn attention, we went from summer to winter without transition (in france we are living the coldest autumn period since 1974)!
We can see also how disorganized and low is the polar vortex in this moment on the Atlantic ans European side
« Last Edit: October 17, 2020, 12:18:22 AM by Positive retroaction »
Sorry, excuse my bad english

A-Team

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Re: The 2020/2021 freezing season
« Reply #354 on: October 17, 2020, 12:11:51 AM »
Quote
There's a reason scientists studying climate change use complex models not tea cups
Right. The discussion has not been at the level of the mid-1700's.

How many people here can expand the acronym SHEBA -- was there a need or could it all have been intuited from gedanken experiments?

Worst freeze season ever underway ... would never know it from the posts. How can 1 person on twitter (https://twitter.com/ZLabe) cover it better than 1777 persons?

1738 – Daniel Bernoulli publishes Hydrodynamica, initiating the kinetic theory
1749 – Émilie du Châtelet derives the conservation of energy from Newtonian mechanics.
1761 – Joseph Black shows ice absorbs heat without changing its temperature when melting
1772 – Dan Rutherford discovers nitrogen which he explains in terms of phlogiston theory
1776 – John Smeaton paper on power, work, momentum, and kinetic energy
1777 – Carl Scheele distinguishes heat transfer by thermal radiation from convection and conduction
1783 – Tony Lavoisier discovers oxygen and develops caloric explanation for combustion
1784 – Jan Ingenhousz describes Brownian motion of charcoal particles on water
1791 – Pierre Prévost shows that all bodies radiate heat, no matter how hot or cold they are

Here's what we are watching unfold (Oct 11):

« Last Edit: October 17, 2020, 12:31:18 AM by A-Team »

Cook

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Re: The 2020/2021 freezing season
« Reply #355 on: October 17, 2020, 12:52:33 AM »
One thing I would like to remark on is the substantial wave action as of late on the Siberian side of the Arctic. To me, it is extremely important and I think it will have some profound effects. I realize the below image is created with models and is not 100% accurate, however current winds in that region are substantial and I think there are some significant waves.

Completely still water only needs to cool the very surface to the sea water freezing point, however during such wind events, mixing ensures that the ENTIRE column of water must reach that temperature in order to freeze during extremely strong winds. Moreover, I believe the effects of the winds will be twofold.

First, my understanding (and is shown in the animation of the stagnation and/or slight advancement of the Laptev Bite recently), that the current weather is affecting the ice edge and either stalling the melt or causing bottom melt. I would have to imagine 19ft waves crashing into the ice edge is going to cause some significant damage.

Second, and I think more importantly, (as Tor stated), the substantial waves are promoting mixing during a time in which the sea is SUPPOSED to be covered with ice. That cool surface layer is now being agitated and is in no way helping the ever-diminishing halocline layer. I don't know the long term implications of wave action in terms of how it affects the refreeze, but for me the most concerning aspect is the constant mixing during the transition period going into winter.

I think both of these are important components and will continue to define the Arctic in the modern era. Granted I cannot prove this as fact, but it is evident how streams can continue to flow well below freezing due to the water's movement.

I think you are on the money with this. The difference between a well mixed salty sea and one that is poorly mixed with a fresh top layer is very significant.  It will be fascinating to watch how this plays out.
« Last Edit: October 17, 2020, 01:09:16 AM by Cook »

passenger66

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Re: The 2020/2021 freezing season
« Reply #356 on: October 17, 2020, 01:18:18 AM »
How can 1 person on twitter (https://twitter.com/ZLabe) cover it better than 1777 persons?
I do think Gerontocrat is pointing this out in his daily updates e.g. "Average remaining extent gain (of the last 10 years) would produce a maximum in March 2021 of 13.04 million km2, 0.84 million km2 below the March 2017 record low maximum of 13.88 million km2."

binntho

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Re: The 2020/2021 freezing season
« Reply #357 on: October 17, 2020, 03:45:55 AM »
Correct me if I misunderstand - the ocean and air both lose heat through emission of LWIR.
I'm not sure what you mean here. Everything is constantly losing and gaining heat from emssion or abosrbtion of long-wave radiation. But this is not an effective heat transfer mechanism at atmospheric temperatures. Conduction and convection are much more effective, and both are at play at the wind/water interface.

The atmosphere loses heat into space from the top of the atmosphere (as Aslan pointed out above), not from the surface of the ocean. And the more water (vapor and clouds) in the atmosphere, the less heat is radiated out.
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binntho

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Re: The 2020/2021 freezing season
« Reply #358 on: October 17, 2020, 03:53:43 AM »
Quote
There's a reason scientists studying climate change use complex models not tea cups
Right. The discussion has not been at the level of the mid-1700's.

How many people here can expand the acronym SHEBA -- was there a need or could it all have been intuited from gedanken experiments?

A little less of that olde time sarcasm, Oren says. But keep it coming, says I, it shines a light into our doldrums.

A lot of us posting here are interested laymen with very different levels of background knowledge. Thought experiments are one way for us to try to understand what is happening, to try to visualise it.

And SHEBA is bloody hard to understand (not the queen, though, being made up and all), let alone trying to explain to others, not to mention getting them to understand it. Which I don't, but I'm trying.
because a thing is eloquently expressed it should not be taken to be as necessarily true
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El Cid

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Re: The 2020/2021 freezing season
« Reply #359 on: October 17, 2020, 08:03:20 AM »
Everyone, thank you for your contributions! (and sorry for the poor analogy).

I know that it is complex system (not for nothing do weather models run on supercomputers) where everything has an effect on everything else with possible chaotic events and system changes.

As for gerontocrat's dilemma (whether this time we will follow 2019's or 2016's lead), i don't have the answer (probably none of us do) but I attach SST anomaly maps for 2016 vs 2020 and 2019 vs 2020.

The Laptev and ESS is warmer than ever. However, the Barents and Kara are colder than they were in 2016 but warmer than in 2019. I would say a very slow refreeze is likely...
« Last Edit: October 17, 2020, 09:45:15 AM by El Cid »

HapHazard

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Re: The 2020/2021 freezing season
« Reply #360 on: October 17, 2020, 08:26:51 AM »
I would say a very slow refreeze is likely...

I would think so! :

[ADS NIPR VISHOP (JAXA)] Arctic Sea Ice Extent.

October 16th, 2020:
     4,928,965 km2, a drop of -9,602 km2:o

oren

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Re: The 2020/2021 freezing season
« Reply #361 on: October 17, 2020, 11:16:19 AM »
In the years 2007, 2012 and 2019, after the very low minimum sea ice extent in those years, extent sharply rebounded in the second half of October and the first few days in November. After that, for the remainder of the freezing season, extent gains were much more average in those years.

This was NOT the case in 2016. There was no massive increase in extent gains at that time or during the entire freezing season. As a result the March 2017 maximum was a record low. What was the difference? I'm not sure.
So what happens in October and what happened in 2016? October is the month when the Siberian seas: ESS, Laptev and usually Kara freeze over, as can be seen in the cropped Wipneus NSIDC extent graphic. That is a huge region of 2.6M km2. However 2016 (the blue line) had a confluence of events. It saw half the ESS refreeze pushed to November, and the Kara pushed to late Nov and December.
Meanwhile, 1M km2 of Hudson Bay which usually freezes in Nov was pushed to early Dec., which is why no Nov spike appeared. December saw delays in the Chukchi and the Barents. Thus a cascade of events made the October spike disappear altogether.

This year, I fully expect the Siberian seas to have a delayed refreeze, though refreeze they eventually will. So the October spike will almost certainly not happen, but it is quite plausible that it will appear in November and/or December.

FishOutofWater

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Re: The 2020/2021 freezing season
« Reply #362 on: October 17, 2020, 11:22:32 AM »
Yep, worst start to a freezing season we have ever seen. The maps at Climate reanalyzer are crazy.

The northern hemisphere temperature anomalies are huge for both the air and the oceans. In the southern hemisphere La Niña is cranking up with intense atmospheric convection over Indonesia, strong trade winds across the Pacific and intense upwelling along the coast of South America and along the equator in the eastern Pacific. There is now a large imbalance in the thermal anomalies and the Arctic is where the largest warm anomalies are found.

The heat content of the north Atlantic is at record high levels in the historic record, and according to proxies the past 2000 years or more. This is a set up for a winter with a weak polar vortex and strong intrusions of warm air from both the Atlantic and Pacific oceans - a poor freezing season. ON the other hand, there's a fair chance of w midwinter sudden stratospheric warming and strong high pressure over the pole which could enhance midwiinter freezing. There is hope that after a record poor start to the freezing season that January through March could be good for new ice. I think there's a better than average chance of a SSW this winter given the La Niña and westerly QBO.

Niall Dollard

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Re: The 2020/2021 freezing season
« Reply #363 on: October 17, 2020, 01:43:32 PM »
Large area of old ice just north of Severnaya Zemlya is almost separated from the main pack. Only a thin channel of about 20cm thick ice connecting it.

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Re: The 2020/2021 freezing season
« Reply #364 on: October 17, 2020, 02:08:52 PM »
Large area of old ice just north of Severnaya Zemlya is almost separated from the main pack. Only a thin channel of about 20cm thick ice connecting it.

Due to those persistent easterly winds across the Siberian side of the Arctic we have been experiencing for the past 6 weeks. Normally a healthy freeze would fill in the leads that are created but the SST temps are too high for this. This is unusual.

Yuha

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Re: The 2020/2021 freezing season
« Reply #365 on: October 17, 2020, 02:44:08 PM »
This was NOT the case in 2016. There was no massive increase in extent gains at that time or during the entire freezing season. As a result the March 2017 maximum was a record low. What was the difference? I'm not sure.

I seem to recall that in 2016 from October to December there was a series of Atlantic storms entering the Arctic and bringing a lot of heat with them. These can be seen as spikes in the DMI temp chart.

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Re: The 2020/2021 freezing season
« Reply #366 on: October 17, 2020, 04:18:34 PM »
Here's an animation comparing the first 16 days of October with 2012
A slightly large file, ~7mb. Click to play.
(larger/better quality version is up on twitter: https://twitter.com/Icy_Samuel/status/1317469236709777416).
I recently joined the twitter thing, where I post more analysis, pics and animations: @Icy_Samuel

Freegrass

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Re: The 2020/2021 freezing season
« Reply #367 on: October 17, 2020, 04:48:26 PM »
Latest Five Day Forecast + Last 24h
Wind + Temp @ Surface
Large GiF!

Missed one yesterday because of alcohol day, so I added the last 24 hours as well.
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binntho

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Re: The 2020/2021 freezing season
« Reply #368 on: October 17, 2020, 04:51:13 PM »
I've been looking at extent maps for the different years, trying to see if there is an obvious difference. And a thought (or "gedanken" as the clever people call it) struck me: Is this the first year when the entire Siberian shelf is ice free? An if so, could that make a signifcant difference to this freezing season - and why?
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jai mitchell

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Re: The 2020/2021 freezing season
« Reply #369 on: October 17, 2020, 05:08:32 PM »
I truly thought we would beat the 2012 minimum this year due to a massive decrease in global aerosol loading.  But we didn't.
Same here... But we did almost beat 2012 without a GAC or Dipole, and the temperatures were record breaking in the arctic. So that theory isn't dead IMHO...

Let's see what winter brings!

With reduced aerosols, I would expect a slight reduction in upper troposphere humidity with a (barely perceptible) reduction in temperatures during the Arctic Winter.
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oren

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Re: The 2020/2021 freezing season
« Reply #370 on: October 17, 2020, 05:33:35 PM »
Here's an animation comparing the first 16 days of October with 2012
Thanks BFTV. It seems to me that the regions that were late to melt are early to freeze in both years. If true, this is probably due to the mixing that goes on when a region has been ice free for a longer period.

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Re: The 2020/2021 freezing season
« Reply #371 on: October 17, 2020, 06:26:45 PM »
Thanks BFTV. It seems to me that the regions that were late to melt are early to freeze in both years. If true, this is probably due to the mixing that goes on when a region has been ice free for a longer period.

Cheers.
A useful comparison might the the date of ice loss (1st attachement) next to the October gain (2nd attachment). Judging by this, we should expect the Laptev sea to have the most difficult time freezing over.
This appears to be supported by the higher SST anomalies in the region currently.


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Re: The 2020/2021 freezing season
« Reply #372 on: October 17, 2020, 08:11:54 PM »
With the shallow ESS ice free, does the extra methane produce more lenticular clouds, capping heat transfer to space?

binntho

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Re: The 2020/2021 freezing season
« Reply #373 on: October 17, 2020, 09:07:10 PM »
With the shallow ESS ice free, does the extra methane produce more lenticular clouds, capping heat transfer to space?
Do you mean noctilucent clouds?
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Re: The 2020/2021 freezing season
« Reply #374 on: October 17, 2020, 10:23:19 PM »
Proposed possibility: the Siberian shelf might be taking a leap forward in its Atlantification schedule.

I'd love to be wrong. Usually am, here. heh

Aluminium

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Re: The 2020/2021 freezing season
« Reply #375 on: October 18, 2020, 08:52:35 AM »
October 13-17.

2019.

jdallen

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Re: The 2020/2021 freezing season
« Reply #376 on: October 18, 2020, 10:12:02 AM »
Quote
There's a reason scientists studying climate change use complex models not tea cups
<snip>
Worst freeze season ever underway ...
<snip>
Concur.  As I observed in the extent and area thread, the numbers on the eastern side of the basin - Kara, Barents, ESS and Laptev - are terrifying.

As FooW observes, this is already having an impact on northern hemisphere circulation and weather.

While the Beaufort and Chukchi numbers are not at record breaking levels, they are not good, and the sea surface temperatures are very much so.

Looking back at another question up thread about the influence of this all... you touch on it by way of stating the heat to melt the ice year round is already present in the Arctic, it just isn't accessible... the net enthalpy in the Arctic is rising almost exponentially, and combined with the observed destruction of the haloclines in the Atlantic side of the Arctic is a dire portent for the very near future. 

The buffers which used to keep a lid on that heat are gone.  Lack of ice growth will merely be a symptom.  The real story will play out in the changes we are going to see in winter weather in the northern hemisphere.

What happens with the weather next spring will be definitive in ways humanity has not experienced in over 10,000 years.  There is simply too much heat loose in the northern hemisphere.

The analogy I think of is one which actually came from my study of geology/vulcanology.  It ties back to the observation of events prior to a phreatic explosion at the rim of a atoll volcano.  Prior to the explosion, there were major jets of steam venting from the area which would later explode.  Someone asked if that would be sufficient for the energy to dissipate.  The point made then was that the steam jets were akin to a giant sticking his finger through the hole in the roof of a hut.  There was no way the giant was going to climb through it, nor would the roof of the hut be enough to contain him.

So it is with the increase in enthalpy in the Arctic.  What we are seeing now in fact is the culmination of years of build up and Atlantification, probably starting before 2012, probably before 2007. 

The last few years, we've watched the giant sticking his finger through a hole in the roof.  I think we are about to see him emerge.
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Re: The 2020/2021 freezing season
« Reply #377 on: October 18, 2020, 11:01:50 AM »
  The real story will play out in the changes we are going to see in winter weather in the northern hemisphere....  I think we are about to see him emerge.


I think the Siberian seas are going through Hudsonization: from now on they will quickly melt out in June/July and then stay open for long and then suddenly freeze over in a short timeframe (2-3 weeks) during November or early December.

how this will change NH winters is anyone's guess

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Re: The 2020/2021 freezing season
« Reply #378 on: October 18, 2020, 11:19:13 AM »
  The real story will play out in the changes we are going to see in winter weather in the northern hemisphere....  I think we are about to see him emerge.


I think the Siberian seas are going through Hudsonization: from now on they will quickly melt out in June/July and then stay open for long and then suddenly freeze over in a short timeframe (2-3 weeks) during November or early December.

how this will change NH winters is anyone's guess
I think you are a bit behind the curve. Winter sea ice is now looking vulnerable.

The Barents has already lost half its winter sea ice compared with the 1980's, and even that is looking vulnerable.

The Kara sea freeze continues into January / February and in some years does not fully freeze up.

And the same to a lesser extent with the Laptev & ESS.


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Re: The 2020/2021 freezing season
« Reply #379 on: October 18, 2020, 12:58:16 PM »
Latest slow animation, 12th to 17th
I recently joined the twitter thing, where I post more analysis, pics and animations: @Icy_Samuel

El Cid

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Re: The 2020/2021 freezing season
« Reply #380 on: October 18, 2020, 02:18:47 PM »

I think the Siberian seas are going through Hudsonization: from now on they will quickly melt out in June/July and then stay open for long and then suddenly freeze over in a short timeframe (2-3 weeks) during November or early December.
I think you are a bit behind the curve.

Yes, I might be behind the curve in many ways :)

I actually meant the Laptev and the ESS as the Barents (and some ways the Kara) has already fallen. I think that as these two (ESS,Laptev) are quite closed to the warmer oceans (unlike the Barents-Kara complex), so their behaviour should soon be like the Hudson (also pretty closed): very quick meltout during summer and late but fast refreeze. And the past few years are obvioulsy going into this direction. I just expect these processes to be even faster then now.

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Re: The 2020/2021 freezing season
« Reply #381 on: October 18, 2020, 03:31:51 PM »
a bit holey around the pole eh ? ..
https://go.nasa.gov/3lVesaU .. b.c.
2007 + 5 = 2012 + 4 = 2016 + 3 = 2019 + 2 = 2021 + 1 =  ' if only we could have seen it coming ' ...

Général de GuerreLasse

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Re: The 2020/2021 freezing season
« Reply #382 on: October 18, 2020, 03:40:15 PM »
Yep, worst start to a freezing season we have ever seen. The maps at Climate reanalyzer are crazy.

There is hope that after a record poor start to the freezing season that January through March could be good for new ice. I think there's a better than average chance of a SSW this winter given the La Niña and westerly QBO.

Hi FishOutofWater,
What does SSW mean? I couldn't find anything in the glossary. Thank you
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Re: The 2020/2021 freezing season
« Reply #383 on: October 18, 2020, 03:42:22 PM »

gandul

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Re: The 2020/2021 freezing season
« Reply #384 on: October 18, 2020, 03:51:20 PM »
@A-team.
Interesting papers, and more interesting is to note that Polyakov et al 2020 that you have brought several times has that conclusion (a mechanism by which Atlantic heat might be reaching the Laptev sea and perhaps this venting become permanent) as “hypothesis” (hopefully testable, otherwise a conjecture), not a fact as quickly taken by others here. It is not a fact that this hopefully testable conjecture has anything to do with current Arctic situation, it is not a fact that Atlantic heat is reaching the surface of the Arctic proper, and it is not a fact that this is a positive feedback.

<Slight edit. O>
« Last Edit: October 18, 2020, 04:25:52 PM by oren »

Shared Humanity

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Re: The 2020/2021 freezing season
« Reply #385 on: October 18, 2020, 04:27:41 PM »
Here's an animation comparing the first 16 days of October with 2012
A slightly large file, ~7mb. Click to play.
(larger/better quality version is up on twitter: https://twitter.com/Icy_Samuel/status/1317469236709777416).

Notable in that gif is the rapid refreeze in 2012 of the open water in the Chukchi and ESS. I think this is directly related to the late season, rapid melt of a large amount of sea ice that had virtually separated from the main pack. The GAC melted a lot of ice but very late in the season and this cold, fresh water lens was primed to refreeze rapidly. This is not the case this year and we should expect the freeze on the Siberian side to continue to be slow.

https://forum.arctic-sea-ice.net/index.php?action=dlattach;topic=3299.0;attach=288830;image

oren

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Re: The 2020/2021 freezing season
« Reply #386 on: October 18, 2020, 04:29:58 PM »
Gandul, I haven't read the paper itself yet but I get the feeling you are misreading this paragraph. While the positive feedback (reduced sea ice => higher mixing rates => reduced sea ice) is a (very reasonable) hypothesis, the increased coupling of AW heat and the sea ice is not, if I read this correctly.

Général de GuerreLasse

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Re: The 2020/2021 freezing season
« Reply #387 on: October 18, 2020, 05:36:10 PM »
Yep, worst start to a freezing season we have ever seen. The maps at Climate reanalyzer are crazy.

 ON the other hand, there's a fair chance of w midwinter sudden stratospheric warming and strong high pressure over the pole which could enhance midwiinter freezing.

Hi FishoutofWater,
Why do you think an SSW will automatically bring more cold to the Arctic?
Here is an excerpt from a 2018 Infometeo.be article. I hope the GIF will work. According to the GIF it's the heat that spreads on the ice after the polar vortex explosion after the SSW appeared. I'm a beginner, sorry if I missed something obvious. ;)
https://imeteo.be/2018/02/12/eclatement-vortex-polaire-consequences-meteo/

In the introduction, we were talking about a sudden stratospheric warming. As the name suggests, this is a sudden increase in temperature in the stratosphere. This change disrupts the temperature gradient that makes the vortex exist. Destabilized by this heat attack, the vortex eventually burst, which profoundly changed the wind regime in the stratosphere. The animation below, taken from the GFS model of a few days ago, shows the destabilization of the cold air mass (in blue) of the polar vortex by warmer air, this warm wave coming here from the troposphere.

GIF needs a click to run

« Last Edit: October 18, 2020, 06:36:31 PM by Général de GuerreLasse »
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Re: The 2020/2021 freezing season
« Reply #388 on: October 18, 2020, 05:40:00 PM »
Yep, worst start to a freezing season we have ever seen. The maps at Climate reanalyzer are crazy.

There is hope that after a record poor start to the freezing season that January through March could be good for new ice. I think there's a better than average chance of a SSW this winter given the La Niña and westerly QBO.

Hi FishOutofWater,
What does SSW mean? I couldn't find anything in the glossary. Thank you
Thanks, GdGL. I was sure SSW was in the glossary already. Added now.

Freegrass

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Re: The 2020/2021 freezing season
« Reply #389 on: October 18, 2020, 06:33:24 PM »
With the refreeze delayed, and melting coming earlier, what effect does that have on the halocline? If I understand correctly, it's ice production that creates saltier water that adds to the thickness of the halocline, right? So with less ice production, this should have a negative effect on the halocline, right? And a weak halocline prevents freezing, which is another negative feedback loop? Am I getting that right?
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Re: The 2020/2021 freezing season
« Reply #390 on: October 18, 2020, 06:48:11 PM »
Gandul, I haven't read the paper itself yet but I get the feeling you are misreading this paragraph. While the positive feedback (reduced sea ice => higher mixing rates => reduced sea ice) is a (very reasonable) hypothesis, the increased coupling of AW heat and the sea ice is not, if I read this correctly.
You read as I read. But the hypothesis here in particular is that there are mechanisms the enhanced turbulence due to shear and not diminished due to lack of ice will be able to breach the stratification and bring heat from the Atlantic Water.

Is it reasonable? I don’t know, I thought the top of this layer was 50 to 150m and a big storm like the GAC 2012 apparently was unable to pull energy from more than 50m (and that was a feat). But if these guys see it possible, I accept it, but as a hypothesis, not a fact. This forum is an echo chamber and pretty soon everyone will be accepting the Atlantification of Laptev sea as a fact.

oren

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Re: The 2020/2021 freezing season
« Reply #391 on: October 18, 2020, 07:10:28 PM »
Thanks for the clarification. I think the mixing in question is not about pulling energy from below but about losing the freshwater lens and getting higher surface salinity. But hey, maybe I should finally find the time to read the paper...
In any case, I don't feel this forum is an echo chamber.

Freegrass

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Re: The 2020/2021 freezing season
« Reply #392 on: October 18, 2020, 07:44:01 PM »
Latest Five Day Forecast
Wind @ Surface + Total Precipitable Water
Wind + Temp @ 850hPa
Large GiFS!
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Positive retroaction

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Re: The 2020/2021 freezing season
« Reply #393 on: October 18, 2020, 09:02:56 PM »
Gandul, I haven't read the paper itself yet but I get the feeling you are misreading this paragraph. While the positive feedback (reduced sea ice => higher mixing rates => reduced sea ice) is a (very reasonable) hypothesis, the increased coupling of AW heat and the sea ice is not, if I read this correctly.
You read as I read. But the hypothesis here in particular is that there are mechanisms the enhanced turbulence due to shear and not diminished due to lack of ice will be able to breach the stratification and bring heat from the Atlantic Water.

Is it reasonable? I don’t know, I thought the top of this layer was 50 to 150m and a big storm like the GAC 2012 apparently was unable to pull energy from more than 50m (and that was a feat). But if these guys see it possible, I accept it, but as a hypothesis, not a fact. This forum is an echo chamber and pretty soon everyone will be accepting the Atlantification of Laptev sea as a fact.

Hello,
This is an extract of one of the researchs in the Arctic about haloclin
excuse me, I don't see any assumptions here, but conclusions supported by measurements made on several points during 15 years, it is not the same thing. Some points are not well understood in arctic, but the weakening of the halocline is well noted

"Time series measurements from a 15-yr mooring record in the eastern EB of the Arctic Ocean demonstrate that the previously identified weakening of stratification over the halocline, which isolates intermediate depth AW from the sea surface, over the period 2003–15 (e.g., Polyakov et al. 2017, 2018), has continued at an increasing rate in more recent years (2015–18). In consequence, oceanic heat fluxes for the winters of 2016–18 are estimated to be greater than 10 W m−2. These fluxes are substantially larger than the previously reported winter estimates for the region for 2007/08 of 3–4 W m−2 (Lenn et al. 2009; Polyakov et al. 2019) and comparable to the estimates for the winters of 2013–15 (Polyakov et al. 2017), implying a significant enhancement of the role of oceanic heat in this region in recent years.

Moreover, the increased vertical heat fluxes have been accompanied by increased upper-ocean current speeds |U| and the magnitude of vertical shear in the horizontal velocities |Uz| over the period 2015–18 (Polyakov et al. 2020b, manuscript submitted to Geophys. Res. Lett.). Using mooring observations from 2003 to 2018, these authors showed that time-averaged values of |U| and |Uz| in the upper 60 m of the water column increased by about 20% and 40%, respectively. In the lower halocline (110–140 m), |U| was generally larger after 2008, increasing on average from 2.5–3.5 cm s−1 in 2003–08 to about 4–5 cm s−1 in 2009–18 (Figs. 3c,d) although the change was not as strong in very recent years, 2016 and 2018, when compared to 2009–15. There is also a clear transition in |Uz|, with significantly larger shears evident post-2010, and in particular in the summer of 2018 (Figs. 3c,d). However, Pnyushkov et al. (2018a) found no significant change in the mean along-slope water transport over the same period.

The combination of reduced stratification and increased shear implies a decrease of the gradient Richardson number (Ri) defined in section 3 (Figs. 3e,f), consistent with an increased turbulent heat flux, associated with vertical mixing by shear instabilities. Although the Ri estimates are based on 20 m vertical resolution measurements, they show a clear trend toward reduced dynamic stability, which may be interpreted as a tendency toward increased turbulent mixing in recent years, coincident with the increase in maximum halocline heat content (Fig. 4). This tendency is particularly strong in 2018 with amplified velocity shear in the relatively weakly stratified upper ocean (Fig. 3)."

https://journals.ametsoc.org/jcli/article/33/18/8107/353233/Weakening-of-Cold-Halocline-Layer-Exposes-Sea-Ice

And. we spoked about effets if wind a few post before
This is an other action, winds increase thé CO2 from the athmosphere from the oceans
"The combination of open leads (i.e. lower ice concentration) and strong winds likely enabled large fluxes of heat, moisture, and gases between the ocean and atmosphere at these times56,57. For example, Fransson et al.57 estimated that the CO2 flux from the atmosphere into the ocean was approximately 20 times higher during storm periods, compared with average wind speed conditions and fewer open leads57."
https://www.nature.com/articles/s41598-019-45574-5

And about thé effet if wind cause deep mix or only surface mix in the océan, how deep are this effets?
 "I don’t know, I thought the top of this layer was 50 to 150m and a big storm like the GAC 2012 apparently was unable to pull energy from more than 50m (and that was a feat). But if these guys see it possible, I accept it, but as a hypothesis, not a fact. "
An other fact hère
Légend is:
"Time series of atmospheric, sea-ice, and oceanographic observations during the first two N-ICE2015 ice drifts in January–March 2015"
note that this does not concern an ice free area but an area with good concentration, in march with halocline thick
Légend for the ultimate diagram
"Ocean mixing given by dissipation rate60 (colour bar, warm colours correspond to stronger mixing), mixed layer depth62 (black line), and presence of Atlantic Water (red bar). Bold red bar indicates Atlantic Water (>2 °C) shallower than 250 m62. The two drift periods are highlighted by black bars in top of panel (a). Storm periods (M1-M6) are shaded as in Fig"

Please note the deep of mixed water, despite of the good ice concentration
Image here (i can't importe it, cause HTML sorry)
https://media.springernature.com/full/springer-static/image/art%3A10.1038%2Fs41598-019-45574-5/MediaObjects/41598_2019_45574_Fig5_HTML.png?as=webp
« Last Edit: October 18, 2020, 09:37:12 PM by Positive retroaction »
Sorry, excuse my bad english

morganism

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Re: The 2020/2021 freezing season
« Reply #394 on: October 18, 2020, 09:39:13 PM »
 (yes, meant noctilucent clouds. 

Looks like someone did a study in Alaska this year, and reported 50% of days in "season" (may til august) had NLCs, and that they were getting lower, and showed some "growth sedimentation mechinism"

http://ffden-2.phys.uaf.edu/atm/atm/theses/2020/Alspach,%20Jennifer_Thesis.pdf

looks like the sattelite is still operational

http://aim.hamptonu.edu/mission/status.php

http://aim.hamptonu.edu/

"The season continues to be a strong one, as shown in the figure. Throughout the 2020 season, daily PMC frequencies have exceeded frequencies in all or most previous years. Although not shown, this is consistent with lower-than-typical temperatures and higher-than-typical water vapor mixing ratios, as measured by the NASA Microwave Limb Sounder. These conditions are consistent with low solar activity, but definitive attribution is still under investigation."

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Re: The 2020/2021 freezing season
« Reply #395 on: October 19, 2020, 02:37:06 AM »
Gandul, I haven't read the paper itself yet but I get the feeling you are misreading this paragraph. While the positive feedback (reduced sea ice => higher mixing rates => reduced sea ice) is a (very reasonable) hypothesis, the increased coupling of AW heat and the sea ice is not, if I read this correctly.
<snippage>
I accept it, but as a hypothesis, not a fact. This forum is an echo chamber and pretty soon everyone will be accepting the Atlantification of Laptev sea as a fact.

Don't take our word for it.

You can listen to the mute testimony of Emiliania Huxleyi (EHux).

It is coming, in fact, in progress.

https://www.nature.com/articles/s41467-020-15485-5
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Re: The 2020/2021 freezing season
« Reply #396 on: October 19, 2020, 03:43:10 AM »
Freeze-up is still going very slowly and asymmetrically, with the 'lower half' more or less normal and the 'upper half' on the Siberian side still stalled. The first two images below measure the disappearance of open water using pixel counts on AMSR2_AWI.

Because of the over-weighting brought in by the Beaufort, it is more instructive to measure the upper half separately, defined here by a line between Utqiagvik and eastern NovZem. The light blue data show not quite 7% loss of open water during the first 17 days of October.

Looking now at sea surface temperature, mixed layer depth, and surface salinity at the revolutionary new CMEMS-Lobelia tool, this unprecedented situation seems likely to continue well into November where it will be even farther outside natural variation than ever, consistent with the zonal vertical mixing data, marine dominance and tipping point analysis described in Polyakov 2019, 2020.

Atlantification of the Laptev has been slowly underway for decades according to those two papers (and 60 earlier journal articles cited) but de-stratification has gotten to the point where AW heat nearer the surface is seriously affecting the ability of fall weather to form ice. The Laptev will freeze over at some point but the ice formed will be thinner, weaker, brine-pocketed and more mobile by the beginning of melt season. We have no idea if, when and where Transpolar Drift winds will set up this fall but the combination could lead to a damaging trend.

https://tinyurl.com/y6zvqdwa

Technical note: the sea surface temperature uses kelvin in which system the freezing point of 32 psu seawater is 271.35. The display bound were then set ±7 around that; these work very similar to Nasa's worldview 'squeeze palette'. Then a divergent palette was selected, causing middle white to be the freezing point and blue/red colors to be the departure. Per NSIDC, each five units of change in salinity affect the freezing point by 0.28ºC so only very small errors are introduced over the current range of open water Arctic salinities. Grayscale salinities were contoured with the G'MIC filter in Gimp.
« Last Edit: October 19, 2020, 04:45:33 AM by A-Team »

oren

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Re: The 2020/2021 freezing season
« Reply #397 on: October 19, 2020, 06:00:22 AM »
Have finally read Polyakov 2020, very good paper and very concerning. Thanks A-Team for bringing it to our attention.
I also recommend reading the new Jennifer Francis paper, though I can't give an intelligent opinion about its contents.

I don't think I've seen this new Jennifer Francis paper referenced on the ASIF:
https://www.woodwellclimate.org/why-has-no-new-record-minimum-arctic-sea-ice-extent-occurred-since-september-2012/

https://iopscience.iop.org/article/10.1088/1748-9326/abc047
Abstract
One of the clearest indicators of human-caused climate change is the rapid decline in Arctic sea ice. The summer minimum coverage is now approximately half of its extent only 40 years ago. Four records in the minimum extent were broken since 2000, the most recent occurring in September 2012. No new records have been set since then, however, owing to an abrupt atmospheric shift during each August/early-September that brought low sea-level pressure, cloudiness, and unfavorable wind conditions for ice reduction. While random variability could be the cause, we identify a recently increased prevalence of a characteristic large-scale atmospheric pattern over the northern hemisphere. This pattern is associated not only with anomalously low pressure over the Arctic during summer, but also with frequent heatwaves over East Asia, Scandinavia, and northern North America, as well as the tendency for a split jet stream over the continents. This jet-stream configuration has been identified as favoring extreme summer weather events in northern mid-latitudes. We propose a mechanism linking these features with diminishing spring snow cover on northern-hemisphere continents that acts as a negative feedback on the loss of Arctic sea ice during summer.

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Re: The 2020/2021 freezing season
« Reply #398 on: October 19, 2020, 11:17:52 AM »

[...]

Looking now at sea surface temperature, mixed layer depth, and surface salinity at the revolutionary new CMEMS-Lobelia tool, this unprecedented situation seems likely to continue well into November where it will be even farther outside natural variation than ever, consistent with the zonal vertical mixing data, marine dominance and tipping point analysis described in Polyakov 2019, 2020.

Atlantification of the Laptev has been slowly underway for decades according to those two papers (and 60 earlier journal articles cited) but de-stratification has gotten to the point where AW heat nearer the surface is seriously affecting the ability of fall weather to form ice. The Laptev will freeze over at some point but the ice formed will be thinner, weaker, brine-pocketed and more mobile by the beginning of melt season. We have no idea if, when and where Transpolar Drift winds will set up this fall but the combination could lead to a damaging trend.

https://tinyurl.com/y6zvqdwa


Thank you A-Team, for all this clear exposition. I really enjoyed reading all this scientifically well informed discussion in this thread, and I thank Binntho, Aslan, Fish, Oren (and the rest) for the very interesting interchange that ensued after I wrote my brief "Late refreeze -> Energy lost" negative feedback comment.

Clearly I was not informed the so many mechanisms (oceanic but also of atmospheric disruption) in motion. This was a good "intensive course" week :-)

2019 had a slow refreeze until late October. 2020 is following the same path at least till mid-October. I'd wager a guess that "slow refreeze" is the new normal.

This is "good", in the sense that, although the Arctic seas contain more energy that the yesteryears, it is a recognized negative feedback that same Arctic seas are so wide open that refreeze is hard to come, and a lot of this energy excess is lost in the process. Otherwise Arctic sea ice would be collapsing much faster.
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Freegrass

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Re: The 2020/2021 freezing season
« Reply #399 on: October 19, 2020, 01:18:21 PM »
Latest Five Day Forecast
Wind + Temp @ Surface
Large GiF!

The ESS/Chukchi is starting to look a lot like the Barents...
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