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Messages - tzupancic

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1
Arctic sea ice / Re: The 2020 melting season
« on: August 09, 2020, 06:22:49 AM »
Arctic Sea Ice melt 2020.

I do not agree with the current implication that the recent reduction in arctic sea ice extent decline indicates that the melting of ice in the Arctic Ocean in 2020 is not exceptional. 

To the contrary it appears that the melt in 2020 is unique and unprecedented. I would suggest, rather, that the current ongoing melt is ‘transformational’.


2
Arctic sea ice / Re: The 2020 melting season
« on: August 05, 2020, 05:03:38 AM »
Arctic Sea Ice

Anticipating what happens next.  Is it bad? Is it good? Is it… whatever?

What to believe… Area? Extent? … Volume? 

What is the significance of what just happened to the Arctic during this melt season?

The effects of temperatures (WAA’s)  and Solar Insolation…  Did they have a substantive impact?

Based on what model? What data source?  How are these hypotheses relevant?

Or is it simply about the weather in August? And nothing has really changed in the Arctic.

As the 2020 melt season enters a key stage.


3
Arctic sea ice / Re: The 2020 melting season
« on: July 24, 2020, 03:52:21 AM »
Looks like events in 2020 are at an interesting point. Just a short note to list a summary of a few aspects of this complex system that would appear to drive how it behaves.

Important Elements Affecting Arctic Sea Ice Melt:

Melt season starting conditions/Sea Ice thickness, extent, and distribution

Early melt season ice conditioning/melt momentum/melt pond formation

Mid melt season solar insolation as a source of energy added to the system

Weather systems and atmospheric temperature as a source of energy added to the system

Sea Ice Concentration/Fragmentation and the effect of ice concentration on surface melt and bottom melt over time

The effect of total energy added to the system up until late July on the ice in August and September

Weather events that affect if energy in the system contacts/melts the ice.

The behavior of complex systems are difficult to understand and explain. It will be interesting to see what is learned as ongoing events are observed and analyzed.



4
Arctic sea ice / Re: The 2020 melting season
« on: July 16, 2020, 06:40:41 AM »
Can concentrated ice melt like dispersed ice? Did early season preconditioning matter? Did solar insulation in July have an effect? What will happen next?

5
Arctic sea ice / Re: The 2020 melting season
« on: July 08, 2020, 06:01:32 AM »
Browned ice is simply vanishing in situ.
What makes the ice brown? You don't see that on thick ice, so is the ice so thin that the dirt (algae?) on the underside gets exposed? Or are those the remnants from black carbon that fell on the ice?

Freegrass, I believe the brown color of the thin ice is due to algae that grow inside or attached to the underside of the ice.  There are a variety of different species.
I think so too, but I'm also wondering if those algae wouldn't have "washed off" by now through bottom melt.

Could it be waves washing over the ice and depositing those algae on top?

Edit: Or dirt (black carbon) washing off the top of the ice feeding an algae bloom that ends up mingled with the ice?


Edit 2: If it were algae that show through thin ice, then why is this big (10km) floe also brown? Another one is whiter, but they're both big, and thus must be thick. So the only explanation IMHO is that something ended up on top of that large floe. But how can waves wash up over an entire 10km ice floe? So it must be black carbon from the fires, no?


Dirty rain?

Freegrass, those are great questions, but even though the brown discoloration seen in thin, melting ice would appear to decrease albedo and be quite relevant to the melting season thread, I kind of think that getting into the details of sea ice algae biology would be seen as 'off topic' regardless of the extent to which it is actually relevant. Nevertheless, it does appear that most, if not all of the coloration of the thin, melting ice is due to algae. How they stay there as bottom melt occurs is a great question, since it would appear to be a significant factor affecting albedo. 

6
Arctic sea ice / Re: The 2020 melting season
« on: July 07, 2020, 09:35:32 PM »
Browned ice is simply vanishing in situ.
What makes the ice brown? You don't see that on thick ice, so is the ice so thin that the dirt (algae?) on the underside gets exposed? Or are those the remnants from black carbon that fell on the ice?

Freegrass, I believe the brown color of the thin ice is due to algae that grow inside or attached to the underside of the ice.  There are a variety of different species.

7
Arctic sea ice / Re: The 2020 melting season
« on: June 26, 2020, 06:06:35 AM »
Just one thing, the conditioning of the ice.

Was 2020 unusual regarding the conditioning of the ice?

Whatever happened in this regard this year was not something that would have been reflected in standard measures of sea ice extent, area, or volume.

Thus, if 2020 was exceptional in ‘conditioning’ one would not expect to see any impact of this at the present time.

I suggest this here because the peak of solar insolation is obviously a time to consider what happens next.

Many have commented that 2020 is not exceptional, referring to sea ice extent, area, and volume.  Regarding what happens next, is early season ‘conditioning’ (such as early formation of melt ponds over extensive areas) a factor to be considered?

8
Arctic sea ice / Re: The 2019/2020 freezing season
« on: October 24, 2019, 04:58:52 AM »
Forum members will recall that earlier this year the discussion was largely about conditioning the ice. In particular heat transfer from water vapor just above the ice was seen as key to creating melt ponds that would drive melt. Low humidity, clear skies would not do this.  Solar energy impacting the system was not seen as a key driver of sea ice melt.

Thus, when significant low humidity clear skies occurred over substantial areas in the arctic basin many predicted a non record breaking melt. Which is exactly what transpired.

But what is the significance of the heat that entered the Arctic Sea system?  Is this added energy now affecting the re-freeze?

9
Arctic sea ice / Re: The 2019/2020 freezing season
« on: October 24, 2019, 04:28:33 AM »
As the historically late advancement of the Arctic Sea Ice re-freeze continues, it would appear that understanding what changes in the system are affecting the current observed results would be useful.  I suggested that accumulated heat in the Arctic Ocean system is important and various sources such as http://ocean.dmi.dk/arctic/satellite/index.uk.php support that hypothesis.  Data does indicate that heat has increased in the Arctic Ocean. If so, where did this heat come from and how did it get there? This appears to be an important and interesting question.  I would suggest that aside from transport from outside the Arctic basin, total solar irradiance on the Arctic Sea itself had a significant impact on adding heat to the Arctic Ocean system in 2019. This was significantly affected by weather, of course, and also by early season reductions in albedo. 

Comments?

10
Arctic sea ice / Re: The 2019/2020 freezing season
« on: October 22, 2019, 06:48:09 AM »
The historically late advancement of the Arctic Sea Ice extent is quite noteworthy, to say the least. It is also fascinating that so little attention has been paid to this ongoing event on this forum. Nevertheless, it would appear that accumulated heat in the Arctic Ocean/system is an important factor.

11
Arctic sea ice / Re: The 2019 melting season
« on: September 21, 2019, 06:12:06 AM »
As the arctic freezing season begins I would just reiterate that with such a complex system, which is presently changing in multiple dimensions, that comparisons with historical events to understand present and future behavior, is a problematic hypothesis.

I would suggest that what is about to happen next is different than what is expected.

12
Arctic sea ice / Re: The 2019 melting season
« on: September 17, 2019, 06:55:33 AM »
It looks like the JAXA Arctic Sea Iced extent has now gone below 4 million... to

3991187

13
Arctic sea ice / Re: The 2019 melting season
« on: September 15, 2019, 05:52:54 AM »
The 2019 melt season is on the verge of surpassing  2016.

14
Arctic sea ice / Re: The 2019 melting season
« on: September 15, 2019, 05:45:55 AM »
Looks like the high pressure system has driven another reduction in arctic sea ice extent

15
Arctic sea ice / Re: The 2019 melting season
« on: September 15, 2019, 04:54:08 AM »
Regarding the 2019 Arctic Sea Ice Melt Season, has anyone noticed that the persistent chunk of ice off the Northeast Coast of Greenland is on the verge of going away this year? This is the persistent chunk that appears to be attached below the sea surface. It has had an amazing history of surviving. It will be interesting to see if this arctic sea ice survives in 2019.

16
Arctic sea ice / Re: The 2019 melting season
« on: September 15, 2019, 03:36:54 AM »
It has been extremely interesting to observe the late season reduction in Arctic Sea Ice extent that has been occurring over the past few days. While it appears that this event is being driven by a high pressure weather system over the central arctic that is concentrating the ice, as a long term follower of the forum it was surprising that there has been so little discussion of this very interesting event that has been occurring. It has been particularly surprising that essentially no one is posting on the geophysical mechanisms involved. If this event is being driven by the high pressure system presently in place over the arctic, it would appear that there could be a late season minimum this year; perhaps going below 4 million.
 

17
Arctic sea ice / Re: The 2019 melting season
« on: July 29, 2019, 05:06:57 AM »
First off, I think that the observation of landfast ice melt off of the Northeast coast of Greenland is relevant to the current 2019 Artic Sea Ice melting season discussion (to pre-empt inevitable comments from forum members who would suggest that this particular subject ought to be discussed somewhere else.)

Turns out, I have followed the annual melting off of the Northeast coast of Greenland with some interest for a number of years now. What I have observed is that this large chunk of ice is particularly resistant to dispersion and melting. It has been a very interesting element of the melting season to track.

In particular, there appears to be an underwater geologic feature that stabilizes the ice off the coast of Northeast Greenland such that going back on Worldview one will see that some big chunk of ice inevitably persists here every year. 

It now looks like some significant dispersion events are beginning to happen here.

I suggest that it will be interesting to see what happens to this ice as the current melting season progresses.
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18
Arctic sea ice / Re: The 2019 melting season
« on: July 19, 2019, 07:46:06 AM »
Just a quick comment on the discussion. Regarding the 2012 melt and it’s relation to 2019. Multiple sources at the time said that the ice lost during the cyclone was going to melt sooner or later. The issue appears to be to what extent the GAC event disrupted ice to the north leading to subsequent melting there that would not have occurred if the GAC event had not taken place.

19
Arctic sea ice / Re: The 2019 melting season
« on: July 19, 2019, 07:38:00 AM »
Neven, my most sincere condolences.


20
Arctic sea ice / Re: The 2019 melting season
« on: July 15, 2019, 07:11:36 AM »
To provide some technical detail related to my initial post tonight

I'm sure there are also many times more similar items besides, interacting in mostly unknown and unforeseen ways. I hope that you may find some better answers here, as I suspect there are experts lurking who may point you to the latest and greatest review articles and whatnot. But I guess the take home message is obvious -- who knows?! We are witnessing a grand experiment.

I am not expecting a lurking technical expert to show up. My point, again, is that given the complexity of the system and the rapid change it is experiencing, be careful about making projections based on historical data.

<edit Neven: This is not the right thread to discuss these things. Please, take it elsewhere. I would kindly ask others to stop responding in this thread.>

21
Arctic sea ice / Re: The 2019 melting season
« on: July 15, 2019, 04:38:00 AM »
To provide some technical detail related to my initial post tonight

Components of the Arctic Sea and the Arctic Region that are changing over time

The start dates of significant freezing and significant melting
   Sea Ice Area/extent throughout the year
   The effect of reduced Sea Ice Area on solar insolation/albedo (when solar energy is available)
   Sea Ice volume
Arctic temperatures during Fall, Winter and Spring
The relative amounts of first year ice vs multi year ice (considering the different properties of such ice)
Ice thickness
Ice fragmentation
Ice mobility
The effect of ice condition on sea ice export
Effect of open water on wave formation and size
The effects of arctic sea waves on ocean heat distribution
The movement of ocean heat from the Atlantic and Pacific into the Arctic ocean
The frequency and intensity of arctic cyclones

Components of the climate system that are changing over time

The amount of energy in the system
The amount of energy in the oceans
The stability and persistence of the jet stream
The persistence of weather patterns
The amount of water in the atmosphere
The transfer of heat into the Arctic
The frequency and intensity of extreme weather events

22
Arctic sea ice / Re: The 2019 melting season
« on: July 15, 2019, 04:26:42 AM »
Just follow along like we all do.  No one has figured out any magic formula for predicting what the ice will do. We watch and compare and speculate, then we see what actually happens.

How then does one understand and interpret real time data?  Shouldn’t the physical properties of the system be appreciated when comparing current observations with historical events?

I am not suggesting that there is some ‘magic formula’, rather, I am asking if there is some alternative way to talk about what is presently being observed.

23
Arctic sea ice / Re: The 2019 melting season
« on: July 15, 2019, 03:53:25 AM »
Components of the Arctic Sea and the Arctic Region that are changing over time

Components of the climate system that are changing over time

How do these forces affect present events? In particular I am curious how Forum Members factor in such changes when assessing real time observations and comparing present events with historical observations. Clearly, the melting of the Artic Sea Ice is a dynamic event occurring in a complex system where multiple fundamental elements and processes are rapidly changing simultaneously.

Obviously, 2012 was seven years ago and a lot has changed in the Arctic and on the planet since then. It would appear that the models being used do not move as fast as this complex system changes.

Setting aside the unpredictable variable of the weather, it would still appear that unanticipated events may well occur in 2019 as a result of fundamental changes in the system that have not yet been appropriately understood or articulated.

More generally, is it possible here to gain some insight into how to understand a highly complex and rapidly changing system?

24
Arctic sea ice / Re: The 2019 melting season
« on: July 09, 2019, 04:59:08 AM »
...
I think what is missing here is a discussion of the impact of increased solar irradiance.
...
I broadly agree, I have also the feeling that incoming solar radiation is probably a bit an understate factor.

Thanks Aslan. (and I liked the Yoda video)

25
Arctic sea ice / Re: The 2019 melting season
« on: July 09, 2019, 04:51:08 AM »
I further suggest, that a key reason that what happens during the remainder of the Arctic Sea Ice melt season here in 2019 cannot be projected from historical results is that the fundamental properties of the system have changed.

26
Arctic sea ice / Re: The 2019 melting season
« on: July 09, 2019, 04:38:08 AM »
ajouis, Agreed. A relatively large amount of solar energy has entered the arctic system so far this year.

I would even venture to say that 2019 started out too sunny in May, when clouds and moisture are more helpful for melt onset. This is why 2019 was trailing years like 2010, 2012 and 2016 in surface preconditioning during the first two weeks of June.

Neven, thank you. Your comment drives home my point. Which is, that while the major introduction of energy to the system comes from solar energy, the discussion here tends to focus on the weather. What happened to that solar energy added to the arctic system this year when it was 'too sunny'? Understood, the sunny weather conditions in May this year were not optimal for the humidity driven formation on melt ponds. But that intense solar energy must have gone somewhere. A large amount of it was not reflected due to albedo. It appears to have been absorbed into the system. Even though such events may not be reflected in relatively near term responses, it would seem that such addition of energy to the Arctic system is important.

27
Arctic sea ice / Re: The 2019 melting season
« on: July 07, 2019, 06:47:53 AM »
Although the mixing of salty vs relatively fresh water below the ice may be required to transfer the energy presently accumulated in the arctic sea to melt ice, (setting top down melting as a result of melt pond formation aside), it still would appear that having an increased amount of energy present in the system as a result of increased absorption of solar irradiance would increase the likelihood of significant melting as the season progresses in 2019.

28
Arctic sea ice / Re: The 2019 melting season
« on: July 07, 2019, 06:36:43 AM »
tzupancic, there are the albedo warming potential graphs that are posted here regularly, and they clearly show 2019 either first or second depending on whether we consider the whole arctic or high arctic only

ajouis, Agreed. A relatively large amount of solar energy has entered the arctic system so far this year.

29
Arctic sea ice / Re: The 2019 melting season
« on: July 07, 2019, 06:30:10 AM »
In fact, the arctic sea ice melt of 2019, regardless of whatever minimum extent occurs, is powerful evidence, coming at the solar minimum, after a solar cycle of reduced intensity, that the climate changes now being observed are not being driven by solar activity alone.

30
Arctic sea ice / Re: The 2019 melting season
« on: July 07, 2019, 06:24:39 AM »
...
I think what is missing here is a discussion of the impact of increased solar irradiance.
...

Are you talking about the reduced albedo, low cloud cover, something else?

Looking at only solar irradiance I believe we are at a solar minimum right now with a lower irradiance than in 2012 and most of the rest of this decade (even then that difference is tiny).

The low solar minimum that the earth is presently experiencing is not the key issue that I am talking about. Rather, the key issue is the amount of solar energy entering the system as a result of reduced albedo in the arctic. This difference far offsets the difference in energy coming from the sun due to the solar cycle.

31
Arctic sea ice / Re: The 2019 melting season
« on: July 07, 2019, 06:11:05 AM »
The most substantial potential source of energy to add to the ASI system is warm water that is 'held down' by the the halocline between 50 m and 250 m (per here)  Also, "In the central  Arctic Ocean, north of Svalbard and in the northern Barents Sea, a permanent pycnocline is present below the cold homogenous layer."

Occasional disussions of Ekman pumping refer to storms accessing this heat.  E.g., from here:
Quote
Abstract
... the contribution of the Ekman transport to the seasonal fluxes of heat and salt to the Arctic Ocean mixed layer will be discussed. It was found that the greatest seasonal variations of Ekman transports of heat and salt occur in the southern Beaufort Sea in the fall and early winter when a strong anticyclonic wind and ice motion are present. The Ekman pumping velocity in the interior Beaufort Sea reaches as high as 10 cm day−1 in November while coastal upwelling is even stronger. The contributions of the Ekman transport to the heat and salt flux in the mixed layer are also considerable in the region.

Solar input seems to be a bigger contributor to ASI melt than imported heat (via air or currents), except where Atlantic water is at the surface.

But I am definitely not an expert on these matters!



Tor Bejnar, Understood. I agreed that in the immediate term the heat energy impacting the sea ice system is being transferred to the ice from salty water. But what I am suggesting is that the significance of the introduction of this energy from solar irradiance is being underappreciated in the present discussion.

32
Arctic sea ice / Re: The 2019 melting season
« on: July 07, 2019, 06:03:45 AM »
...
I think what is missing here is a discussion of the impact of increased solar irradiance.
...

Are you talking about the reduced albedo, low cloud cover, something else?

Looking at only solar irradiance I believe we are at a solar minimum right now with a lower irradiance than in 2012 and most of the rest of this decade (even then that difference is tiny).

Really? are you saying that the arctic in 2019 has experienced exceptionally low solar irradiance?  I do not think so.

33
Arctic sea ice / Re: The 2019 melting season
« on: July 07, 2019, 05:22:11 AM »
Perhaps people here can correct me if I am wrong, but in comparison with air temperature, humidity, and wind action; solar insolation is the most substantial potential source of energy being added to the arctic system in terms of possible energy magnitude.


34
Arctic sea ice / Re: The 2019 melting season
« on: July 07, 2019, 05:12:17 AM »
That is a good list.  I’m pretty sure we try to address all of them.  If you read through the comments on this thread, I think you will find answers to your questions.

Rod,

I think what is missing here is a discussion of the impact of increased solar irradiance. While the increased energy added to the system may not immediately drive sea ice melt in the short term, it would appear to have important implications.

35
Arctic sea ice / Re: The 2019 melting season
« on: July 07, 2019, 03:41:16 AM »
Feel free to add your additions or comments to my list. Or to comment on my point about the relevance of solar energy to the arctic sea ice system.

36
Arctic sea ice / Re: The 2019 melting season
« on: July 07, 2019, 03:31:00 AM »
As the Arctic Sea Ice melt season advances from the summer solstice through the period of maximal sea ice melt I thought it might be useful to post a simple list of factors that are important for understanding what is occurring.

Just one comment. Since the greatest source of energy available to this system is the sun (solar insolation) and I understand how the temperature gradient of relatively fresh vs salty water comes into play here, I am still curious why there is not more discussion regarding the effect of the change in arctic albedo. It would appear to be a very significant factor in 2019.

Has more energy than usual been added to the system this year? If so, what effect does that have?


Anyway, here is my list.

Arctic sea ice: Factors affecting the melt

The weather;

Surface air temperature

High and low pressure systems

Solar irradiance/albedo/cloud cover

Humidity/precipitation

Wind/dipoles/sea ice export

Wind/dipoles/cyclones/mixing of water temperature gradients

(Water temperature/ocean currents/salty vs fresh water temperature gradient*)

The condition of the ice;

Sea ice age/thickness

Preconditioning

Melt pond formation

Fragmentation

Distribution – Dispersion vs Concentration

Relevant data;

Weather info

Satellite observations

Model based assessments

On site observations

Historical observations

Speculation…




37
Arctic sea ice / Re: The 2017 melting season
« on: July 11, 2017, 06:51:21 AM »
Regarding snow cover on the Arctic Sea Ice and its effect on the 2017 melt. Specifically, was there a lot of snow on the Arctic Sea Ice this past year? If so, how would that effect the ongoing melt, and how does one know? After all, it was anonymously warm during a lot of the previous freeze season. The atmosphere has increased H2O. It snowed a lot in the far North.  Did that phenomenon extend over the Arctic Ocean?  Or rather, should one hypothesize that the observed heavy snow fall over land suddenly stopped at the Arctic Sea?

I would suggest that it is most likely that the observed increased snowfall over many land areas adjacent to the Arctic Sea supports the hypothesis that it also snowed more than usual over the Arctic Sea Ice.

Setting the issue of definitive analytics aside, why should one think that Arctic Sea Ice snow cover was not unusually substantial this year?
 
Applying Occam’s Razor (the most simple hypothesis is most likely to be correct), heavy snow cover on the Arctic Sea Ice appears to be a significant factor this year.

38
Just fyi, I once posted at some length on an obscure Solar Cycle 24 discussion forum about the Arctic Sea Ice that was dominated by climate change denialists. I learned a thing or two. If it matters, I am a Ph.D. scientist.

40
Regarding the semantic definition of ‘Natural Variations’ the recent discussion in climate science about changes in the variability of Northern Hemisphere Jet Stream comes to mind. Given that the Jet Stream naturally varies, if the frequency, magnitude and intensity of such variations are observed to change in a concerted way over time, in correlation with key factors driven by human activity, is such a variation still ‘natural’?  Similarly, if Arctic Sea Ice melt is observed to correlate with increased heat in the climate system resulting from human activity and also changes in atmospheric circulation (kind of sounds like changes in the jet stream…) How does one determine that an observed change in a complex process is natural and not driven by other factors known to be altering the system?

41
In response to a number of posts discussing the issue of communication with a general audience and whether scientists in general or the authors here should be criticized for their language/format/style; here is an example of the climate denialist reaction; “Natural Variability’s Role in Arctic Sea Ice Decline Strengthens Case for Lukewarming”.

https://www.cato.org/blog/natural-variabilitys-role-arctic-sea-ice-decline-strengthens-case-lukewarming

In perusing this argument the concept of sophistry immediately comes to mind.

The logical incongruity in the last few paragraphs stands out. Cato’s fallacy begins with “But if a sizeable proportion of the ice loss is being caused by natural variability (and not greenhouse gas emissions), then some proportion of the warming observed over the past 30 years must be caused by the same forces of natural variability”… their contrived argument spins illogically out of control from there.

Cato incorrectly asserts, “This means that when comparing the rates of observed warming with the rates of warming expected by climate models, that natural variability acting on Arctic sea ice has been making the models seem to be closer to reality than they actually are.”

Huh! ???  The premise of the paper is that models do not explain the observed Arctic melt, so some other factor must be involved. Thus, they modified the model.

Cato goes illogically downhill from there, asserting the complete opposite of the finding of the study which is that the observed melt of Arctic Sea Ice can indeed be explained by geophysics. And that human activity has been a major driver.

42
jdallen

I agree that you have recognized a key point, "I agree, and admit I haven't digested the paper in detail yet, but am skeptical that some/much of what they attribute to "natural variation" which may actually be driven by climate change outside of the Arctic."

Michael Hauber made this same point in the discussion above. If a circulation change is promoting the melt of the arctic sea ice, is this circulation change a natural variation, or is this circulation change the result of human activity?

43
Just a few comments regarding Ding et al, 2017; “Influence of high-latitude atmospheric circulation changes on summertime Arctic sea ice” and also the discussion of this paper.

First, a PDF of the paper can be found here: https://www.atmos.washington.edu/~david/Ding_etal_2016_submitted.pdf

Given that Nature Climate Change is a well-respected high profile journal with a rigorous peer review system, it appears that this paper is potentially important. The observed rapid decline of the Arctic Sea Ice is not explained by current hypotheses. Thus, there is a need for new ideas.

I do not agree with the notion that the scientists who did this work have motives other than advancing climate science. I further do not agree that the scientists who study this topic lack insight and creative thinking.

Regarding ‘models’ I have a somewhat different understanding than what is commonly expressed about models. I view climate models as hypotheses. Given that scientific understanding is inherently tentative and incomplete, of course these models (hypotheses) have limitations. The point is to pursue the scientific method. With a complex system like the geophysics of the Arctic, computational simulations of recognized processes makes sense.

As many have reiterated, the observed rapid decline of Arctic Sea Ice is not explained by present understanding of the function of the climate system. New insight is required.  “Influence of high-latitude atmospheric circulation changes on summertime Arctic sea ice” appears to be an interesting contribution to the discussion.

44
That is, assuming that an atmospheric circulation change has been an important contributor to the observed reduction in Arctic Sea Ice, is this hypothetical atmospheric circulation change a natural variation or is this proposed circulation change itself a result of climate change?

45
Arctic sea ice / Re: The 2017 melting season
« on: March 16, 2017, 05:26:01 AM »
Regarding the discussion of fundamental drivers of the observed Arctic Sea Ice melt, thanks to Archimid for establishing a separate thread to discuss emerging scientific insight into the fundamentals of the melt.

Those who are interested should check out the new "Arctic Sea Ice Changes: Natural Variation vs human influence" discussion thread.

The discussion begins with the paper published this week in Nature Climate Change "Influence of high-latitude atmospheric circulation changes on summertime Arctic sea ice"


46
Basically they are saying that the reason why the Arctic ice is melting faster than model predictions is due to a variation in circulationt, with increased high pressure over Greenland.  This change in circulation matches observations, and when the models are forced into this circulation change the modelled sea ice matches observations.  This seems to be strong evidence (maybe not conclusive)  that the increased sea ice melt is due to this circulation change, and is not due to loss of ice structure/strength, or a failure to include enough albedo effects, or failure to account for warming from the oceans below or mixing of the halocline.

The question then is whether the circulation change is a feedback to the ice loss, or to some other aspect of AGW.  They argue that it is not as the models do not show the circulation change.  However perhaps the models are missing a factor whereby AGW or ice loss leads to this circulation change. 

The final key would be to understand what is causing this circulation change.  If it is a naturally driven variation then presumably someone can uncover the mechanism by which this variation is driven over a multi-decadal period, similar to how we currently understand much of the mechanisms of how ENSO works, and some behind PDO and AMO (but a lot of gaps in our knowledge there IMO).  Until we understand this variation better it would remain possible that it is AGW forced in some way that the models cannot currently capture.

I'm sure this isn't the last word on research into the model-observation gap for Arctic ice loss.  I would note that all the research I am aware of on this topic does point to natural variation being the cause.  Is anyone aware of any research providing evidence otherwise?

Michael Hauber,

I agree. You have identified a key point. Assuming that a circulation change is driving Arctic Sea Ice melt, is this circulation change a natural variation, or rather,  a change due to external factors?

47
Just one more comment; perusing the blogosphere, Stoat has made a relevant comment, “Influence of high-latitude atmospheric circulation changes on summertime Arctic sea ice?”

http://scienceblogs.com/stoat/2017/03/15/influence-of-high-latitude-atmospheric-circulation-changes-on-summertime-arctic-sea-ice/

btw, check out this link to see the data, ie. click on 'PDF as submitted', in the first paragraph.



48
Just a short note, there were several ‘stories’ about Ding et al. that perhaps provide some useful background: “Up to half of Arctic melting can be explained by natural changes”, Christian Science Monitor; http://www.csmonitor.com/Environment/2017/0314/Up-to-half-of-Arctic-melting-can-be-explained-by-natural-changes

“Natural Environmental Swings Cause Up To Half Of Arctic Sea Ice Loss”; http://www.npr.org/sections/thetwo-way/2017/03/14/520104348/natural-environmental-swings-cause-up-to-half-of-arctic-sea-ice-loss

“Arctic Sea Ice Melt, Driven by Global Warming, Accelerated by Nature”; https://insideclimatenews.org/news/14032017/arctic-ice-melt-climate-change-science


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Thanks to Archimid for setting up this discussion thread on Arctic Sea Ice Changes: Natural Variation vs Human Influence.

It appears that Ding et al, 2017. “Influence of high-latitude atmospheric circulation changes on summertime Arctic sea ice”. Nature Climate Change.  is an important paper that addresses the widely recognized issue that the observed decline of Arctic Sea Ice is not projected by existing models. It further appears that this paper will stimulate a lot of discussion. Thus, opening a new thread to discuss this topic is useful.


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Arctic sea ice / Re: The 2017 melting season
« on: March 15, 2017, 10:45:22 PM »
Does anyone have any comments on the paper that came out on Monday in Nature Climate Change, "Influence of high-latitude atmospheric circulation changes on summertime Arctic sea ice". http://www.nature.com/nclimate/journal/vaop/ncurrent/abs/nclimate3241.html

The authors propose that a substantial amount of the recently observed summer decline in Arctic Sea Ice has been driven by natural variation in atmospheric circulation. "The Arctic has seen rapid sea-ice decline in the past three decades, whilst warming at about twice the global average rate. Yet the relationship between Arctic warming and sea-ice loss is not well understood. Here, we present evidence that trends in summertime atmospheric circulation may have contributed as much as 60% to the September sea-ice extent decline since 1979. A tendency towards a stronger anticyclonic circulation over Greenland and the Arctic Ocean with a barotropic structure in the troposphere increased the downwelling longwave radiation above the ice by warming and moistening the lower troposphere. Model experiments, with reanalysis data constraining atmospheric circulation, replicate the observed thermodynamic response and indicate that the near-surface changes are dominated by circulation changes rather than feedbacks from the changing sea-ice cover. Internal variability dominates the Arctic summer circulation trend and may be responsible for about 30–50% of the overall decline in September sea ice since 1979."

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