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When will the Arctic Extent dip below 1,000,000 Km^2

2018-2019
12 (17.9%)
2020-2025
21 (31.3%)
2026-2030
13 (19.4%)
2031-2040
15 (22.4%)
2041-2060
2 (3%)
2061-2080
0 (0%)
2081-2099
1 (1.5%)
2100-beyond
3 (4.5%)

Total Members Voted: 66

Voting closed: July 27, 2018, 07:46:32 AM

Author Topic: When will the Arctic Go Ice Free?  (Read 17231 times)

oren

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Re: When will the Arctic Go Ice Free?
« Reply #200 on: October 10, 2018, 11:49:17 PM »
I once made an animation of the Chukchi as it went from perennial ice cover to seasonally ice-free ("BOE"). I'll dig it up and repost it. Hudson ans Kara are not very similar to the CAB. The Chukchi is more similar but still quite different as it has a sea ice repository next to it, while the CAB does not.

oren

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Re: When will the Arctic Go Ice Free?
« Reply #201 on: October 12, 2018, 03:48:45 AM »
Here is the animation I mentioned. It focuses on the behavior of the Chukchi on its way to being seasonally ice-free. Before 1990 the Chukchi was rather stable, with about half of it melting each year. But then changes came along - earlier melt onset, a higher percentage of melt culminated by the first BOE in 2007, a later refreeze onset, and a later refreeze completion. The process wasn't immediate, but over two decades the changes are enormous. The length of time in which the Chukchi is less than fully ice-covered has increased from ~5 months to ~8 months.
I believe the CAB will undergo a quite similar process, though hopefully longer. The process has already started, and 2012 and 2016 proved a lot of the CAB is vulnerable, while 2018 is proving that the refreeze can be delayed significantly.

Notable years pushing the Chukchi envelope:
1991 (late refreeze)
1993 (new minimum)
1998 (new minimum)
2004 (new minimum)
2006 (late refreeze)
2007 (new minimum near zero, late refreeze)
2012 (earlier near zero)
2016 (late final refreeze, first into January)
2017 (early melt, late refreeze)

Notes: January of the following year is appended to each year. The date range shown is April 15th to January 20th. Data is NSIDC extent.

Pmt111500

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Re: When will the Arctic Go Ice Free?
« Reply #202 on: October 12, 2018, 04:57:54 AM »
Thanks Oren. Here at forum, it's easy to pick up some alarmistic views as people present their pet theories. It's easy to forget main stream science has some very good arguments too.
Amateur observations of Sea Ice since 2003.

Klondike Kat

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Re: When will the Arctic Go Ice Free?
« Reply #203 on: October 12, 2018, 01:47:44 PM »
Yes, very nice.  The trend is clearly towards less ice, but once ice-free, there is nothing preventing refreezing.  I suspect the CAB will follow suit - hopefully longer as Oren stated.

Stephan

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Re: When will the Arctic Go Ice Free?
« Reply #204 on: October 12, 2018, 05:26:20 PM »
Thank you oren for this animation.
I am willing to investigate the area/extent, thickness and volume changes over the years and to look at "BOE" predictions derived from area/extent, thickness and volume. Can anyone send me the .xls or .csv files of area/extent, thickness and/or volume for Kara, Chukchi and Hudson Sea? Would be nice, thanks in advance.

GoSouthYoungins

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Re: When will the Arctic Go Ice Free?
« Reply #205 on: October 12, 2018, 08:48:18 PM »
Thanks Oren. Here at forum, it's easy to pick up some alarmistic views as people present their pet theories. It's easy to forget main stream science has some very good arguments too.

There are times when an alarm is supposed to go off. This is one of those times. It is not possible to be "alarmistic" currently.

The Pacific and Atlantic have drastically encroached on the Arctic Sea Ice. 2014,2015,2016 set consecutive heat records. 2017 and 2018 experienced a slight reprieve due to la nina. 2019 will be absurdly hot again. CO2 levels are 10% higher relative to baseline than they were in the beginning of 2014.

There is a significant lag if the heating effect from GHG emissions. The is also a significant lag in developing the physical and institutional infrastructure necessary to substantially reduce emissions. Thus we are almost certain to experience about twice the warming from emissions we have felt thus far.

Throw in a couple positive feedbacks, most notably the melting of the northern hemispheres ice cap, and we are quite clearly headed towards a drastically different climate system in the next decade or two.

BE ALARMED
big time oops

Stephan

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Re: When will the Arctic Go Ice Free?
« Reply #206 on: October 12, 2018, 09:18:20 PM »
(This post is in the wrong thread but it must be said)
Here in Germany we suffer almost without exception from a too warm and too dry summer since beginning of April. We had almost no rain throughout June to October with a lot of crop failure and forest fires. And tomorrow daily max. temp is forecasted to be 27-29°C almost nationwide. Many people are alarmed, and the green party is really up in public polls. Diesel discussion and the end of coal mining is in every news show...

oren

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Re: When will the Arctic Go Ice Free?
« Reply #207 on: October 15, 2018, 03:16:41 AM »
Thank you oren for this animation.
I am willing to investigate the area/extent, thickness and volume changes over the years and to look at "BOE" predictions derived from area/extent, thickness and volume. Can anyone send me the .xls or .csv files of area/extent, thickness and/or volume for Kara, Chukchi and Hudson Sea? Would be nice, thanks in advance.
Apologies for the delay in responding.
The best is to download the data from the appropriate sources that you should bookmark, and plug them into a spreadsheet that fits the analysis you want to do.
My (very messy!) Excel workbooks normally have a worksheet where I paste the raw data, and other worksheets that build on that data using index/if functions, so as time goes by and the data becomes longer I am ready to go, though I still need to change the scale of the graphs to use all the new data.
Data fro text files (Wipneus) is pasted into a single column, then the function "text to columns" with delimited-space is used to unpack it into useful spreadsheet form.

The best source is ArctischePinguin - Wipneus' site, without it nothing would get done.
Regional daily PIOMAS data (since 2000)
https://sites.google.com/site/arctischepinguin/home/piomas/data/PIOMAS-regional.txt.gz?attredirects=0

"Home brew" regional AMSR2 extent and area (since 2012).
https://sites.google.com/site/arctischepinguin/home/amsr2/data/Jaxa_AMSR2_L3_10km_Area_Extent-v0.0.txt?attredirects=0&d=1

NSIDC regional daily data for both extent and area. But for area data of the CAB you must add back the size of the pole hole, varying by year.
Quote
ftp://sidads.colorado.edu/DATASETS/NOAA/G02135/seaice_analysis/Sea_Ice_Index_Regional_Daily_Data_G02135_v3.0.xlsx

NSIDC documentation of the sea ice index, including explanation of the pole hole on page 37 and its sizes on page 38.
https://nsidc.org/data/g02135

I hope I haven't missed anything. Browse the data parts of ArctischePinguin for various other files.
https://sites.google.com/site/arctischepinguin/site

I really hope all this helps. I can try to locate sample workbooks that I use, but it is one big mess so if you can build your own you will have a much better chance of success.

Stephan

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Re: When will the Arctic Go Ice Free?
« Reply #208 on: November 05, 2018, 08:52:56 PM »
It is time for the monthly update of my extrapolation when the extent [Extent], volume [Volumen] and thickness [Dicke] will reach zero. The extrapolation occured linearly and by a logarithmic function; the latter one almost constantly resulting in earlier times. October value now includes 2018, and BOE for October seems to appear much earlier than extrapolated last year (up to 9 years difference than last year (!), see my last posting on Sep 09 in this thread), mostly due to the late minimum in September 2018 compared to 2017 and the delayed refreezing in the first half of October (see for details the sea ice area and extent thread). According to thickness October is the earliest month of the year compared to all other months.
Please note that this is not a forecast but a trend!
See attached table.

Klondike Kat

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Re: When will the Arctic Go Ice Free?
« Reply #209 on: November 05, 2018, 10:32:40 PM »
That 2070 timeframe looks about right.

magnamentis

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Re: When will the Arctic Go Ice Free?
« Reply #210 on: November 05, 2018, 11:18:11 PM »
That 2070 timeframe looks about right.

+1

and i'm glad he calculated zero.

unfortunately some impatient observers who want to witness ice-free under all circumstances or seek headlines will come up with all kinds of arbitrary values that should serve as "ice-free"

the most common of such numbers at the moment is < 1'000'000 km2 of extent which i find ridiculous, 1M km2 is a lot of ice and visible with the naked ice as well as it will be a kind of homogeneous mass, at least in parts.

ice-free = zero ice and zero is 0-0.999999999999....... IMO
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Alison

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Re: When will the Arctic Go Ice Free?
« Reply #211 on: November 06, 2018, 01:31:30 AM »
Quote
impatient observers who want to witness ice-free

Given it is unfortunately going to happen, I’d like to see it. I’ll be a deceased observer by 2070, so perhaps you could forgive a little impatience :)
« Last Edit: November 06, 2018, 01:43:16 AM by Alison »

Sleepy

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Re: When will the Arctic Go Ice Free?
« Reply #212 on: November 06, 2018, 06:50:08 AM »
unfortunately some impatient observers who want to witness ice-free under all circumstances or seek headlines will come up with all kinds of arbitrary values that should serve as "ice-free"

the most common of such numbers at the moment is < 1'000'000 km2 of extent which i find ridiculous
Heh, the Arctic Ocean is ~14,000,000 km² and the origin of that number is:


The dashed line represents nearly ice-free conditions (i.e., when sea ice extent is less than 106 km² for at least five consecutive years). For further technical details see the
Technical Summary Supplementary Material {Figures 6.28, 12.5, and 12.28–12.31; Figures TS.15, TS.17, and TS.20}
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gerontocrat

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Re: When will the Arctic Go Ice Free?
« Reply #213 on: November 29, 2018, 02:58:21 PM »
Extract from a post by AbruptSLR.
https://forum.arctic-sea-ice.net/index.php/topic,2205.msg182527.html#msg182527

Goodbye snow, hullo rain. That would tend to slow down winter sea ice formation?
(And not do bbr's hypothesis a lot of good).

Quote
Towards a rain-dominated Arctic
Richard Bintanja and Olivier Andry
Royal Netherlands Meteorological Institute (KNMI), De Bilt, Netherlands (bintanja@knmi.nl)
Current climate models project a strong increase in Arctic precipitation over the coming century, which has been attributed primarily to enhanced surface evaporation associated with sea-ice retreat. Since the Arctic is still quite cold, especially in winter, it is often (implicitly) assumed that the additional precipitation will fall mostly as snow.

However, very little is known about future changes in rain/snow distribution in the Arctic, notwithstanding the importance for hydrology and biology. Here we use 37 state-of-the-art climate models in standardised twenty-firstcentury (2006–2100) simulations to show that 70◦ – 90◦N average annual Arctic snowfall will actually decrease, despite the strong increase in precipitation, and that most of the additional precipitation in the future (2091–2100) will fall as rain. In fact, rain is even projected to become the dominant form of precipitation in the Arctic
region. This is because Arctic atmospheric warming causes a greater fraction of snowfall to melt before it reaches the surface, in particular over the North Atlantic and the Barents Sea. The reduction in Arctic snowfall is most pronounced during summer and autumn when temperatures are close to the melting point, but also winter rainfall is found to intensify considerably. Projected (seasonal) trends in rain/snowfall will heavily impact Arctic hydrology (e.g. river discharge, permafrost melt), climatology (e.g. snow, sea ice albedo and melt) and ecology (e.g. water and food availability).
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Dharma Rupa

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Re: When will the Arctic Go Ice Free?
« Reply #214 on: November 29, 2018, 10:03:33 PM »
Extract from a post by AbruptSLR.
https://forum.arctic-sea-ice.net/index.php/topic,2205.msg182527.html#msg182527

Goodbye snow, hullo rain. That would tend to slow down winter sea ice formation?
(And not do bbr's hypothesis a lot of good).

Quote
Towards a rain-dominated Arctic
Richard Bintanja and Olivier Andry
Royal Netherlands Meteorological Institute (KNMI), De Bilt, Netherlands (bintanja@knmi.nl)
Current climate models project a strong increase in Arctic precipitation over the coming century, which has been attributed primarily to enhanced surface evaporation associated with sea-ice retreat. Since the Arctic is still quite cold, especially in winter, it is often (implicitly) assumed that the additional precipitation will fall mostly as snow.

However, very little is known about future changes in rain/snow distribution in the Arctic, notwithstanding the importance for hydrology and biology. Here we use 37 state-of-the-art climate models in standardised twenty-firstcentury (2006–2100) simulations to show that 70◦ – 90◦N average annual Arctic snowfall will actually decrease, despite the strong increase in precipitation, and that most of the additional precipitation in the future (2091–2100) will fall as rain. In fact, rain is even projected to become the dominant form of precipitation in the Arctic
region. This is because Arctic atmospheric warming causes a greater fraction of snowfall to melt before it reaches the surface, in particular over the North Atlantic and the Barents Sea. The reduction in Arctic snowfall is most pronounced during summer and autumn when temperatures are close to the melting point, but also winter rainfall is found to intensify considerably. Projected (seasonal) trends in rain/snowfall will heavily impact Arctic hydrology (e.g. river discharge, permafrost melt), climatology (e.g. snow, sea ice albedo and melt) and ecology (e.g. water and food availability).

While I do tend to agree with their projection, I object to their use of words like "will" rather than "might".  The models simply do not have the demonstrated skill which warrants definitive pronouncements.

Yes, I do expect the snow to change to rain....but I don't KNOW it will.

Stephan

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Re: When will the Arctic Go Ice Free?
« Reply #215 on: December 06, 2018, 10:24:14 PM »
It is time for the monthly update of my extrapolation when the extent [Extent], volume [Volumen] and thickness [Dicke] will reach zero. The extrapolation occured linearly and by a logarithmic function; the latter one almost constantly resulting in earlier times. November value now includes 2018. In contrast to October (see my post on Nov. 05) November 2018 showed a rapid freezing higher than average which also results in values above the linear trend line from 1979 to 2018. This results in slightly higher values of when zero will be reached, but not much of a difference compared to last year.
Please note that this is not a forecast but a trend!
See attached table.

oren

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Re: When will the Arctic Go Ice Free?
« Reply #216 on: December 06, 2018, 11:51:29 PM »
Stephan, can you extrapolate to 1M km2 of extent as well? The "nearly ice free" criterion.

El Cid

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Re: When will the Arctic Go Ice Free?
« Reply #217 on: December 07, 2018, 10:25:28 AM »
I don't want to be mean or nasty but these extrapolations are probably totally pointless. Extrapolations like this from around 2010 showed that we should already be ice free. The reason we are not - I believe - is that the Arctic has two distinct parts: the Central Arctic with deep seas below it and the periphery (mostly everything else) with shallow seas. It seems that these shallower seas have become mixed enough to either stay icefree even during the winter or to melt relatively quickly during the summer regardless of the weather. The Center, however, still holds. Only very favourable (for ice loss) weather can melt it partially during some exceptional summers (like 2012) and even then it freezes back quickly during autumn. Unless the Central Arctic Atlantifies - which will be hard due to bathymetry - I do not see it melting out soon.

So my point is that you can not project from total Arctic extent/volume/etc because the 2 parts of the Arctic are completely different and behave completely differently - probably because of bathymetry.   

El Cid

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Re: When will the Arctic Go Ice Free?
« Reply #218 on: December 07, 2018, 10:28:33 AM »
By the way, I believe that the above is the explanation for the "stall" since 2007: the shallow parts have entered a new era (system change) but the Central Arctic has not. When it will do so, I do not know. It could be next year (I very much doubt it ) but it also might stay like that for another 30 years

oren

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Re: When will the Arctic Go Ice Free?
« Reply #219 on: December 07, 2018, 10:46:09 AM »
The "stall" since 2007 is not a stall, yet. Check out 5-year and 10-year averages. Check out area instead of extent. Check out winter volume. The bad trend continues. Had 2012 weather happened in 2016 or 2017 a new record would have easily happened. As Neven said back then, we dodged a cannonball.
It's true though that the arctic is more complex than just the headline numbers: the bathymetry you mentioned, MYI causing an easy reduction in volume but now FYI makes it harder (the "slow transition" prediction), and the melting season is much shorter in the higher latitudes. So the linear trend may not happen just like that. But I still expect the coming decade to bring about at least one "outlier" year of nearly ice-free conditions in September.
Bear in mind the melting weather is a lot about prevailing wind and export, not just sunny vs. cloudy and warm vs. cold. Should the Central Arctic start flowing towards the Fram and the unlimited-capacity Atlantic front in earnest, as it did in parts of 2016 (and 2007), the melting season will have a much easier time than when the prevailing export of thick central ice is towards the limited-capacity Beaufort (as happened this year).

Stephan

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Re: When will the Arctic Go Ice Free?
« Reply #220 on: December 07, 2018, 06:07:28 PM »
Stephan, can you extrapolate to 1M km2 of extent as well? The "nearly ice free" criterion.
Here is the table (the right one with extrapolation to 1M).
I did it only for extent as I am not sure which volume should be attributed to the "1M km²" extent. The values are (of course) lower by 6 to 28 years.
The steeper the slope ("stg") the smaller is the difference until 1M is reached in comparison to 0M km²
« Last Edit: December 07, 2018, 06:16:37 PM by Stephan »

Stephan

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Re: When will the Arctic Go Ice Free?
« Reply #221 on: December 07, 2018, 06:19:19 PM »
By the way, I believe that the above is the explanation for the "stall" since 2007: the shallow parts have entered a new era (system change) but the Central Arctic has not. When it will do so, I do not know. It could be next year (I very much doubt it ) but it also might stay like that for another 30 years
Please check my 5 year averages I posted yesterday in the "latest PIOMAS" thread. There is no stall, only the volume has not further decreased in the years 2014-2018 compared to 2009-2013. (Re: Latest PIOMAS update (December)
« Reply #2680 on: December 06, 2018, 11:00:25 PM )

El Cid

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Re: When will the Arctic Go Ice Free?
« Reply #222 on: December 07, 2018, 09:53:56 PM »

[/quote]
 There is no stall, only the volume has not further decreased
[/quote]

That's a good one. No stall, only the volume stopped decreasing :)

jdallen

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Re: When will the Arctic Go Ice Free?
« Reply #223 on: December 08, 2018, 08:07:10 AM »

There is no stall, only the volume has not further decreased
[/quote]

That's a good one. No stall, only the volume stopped decreasing :)
[/quote]
The whole row over stall vs. non-stall strikes me as being akin to mistaking "weather" for "climate".

Metaphor - California had some pretty serious rainfall over the last few months.  However, most of the state *still* is in moderate to severe drought. 

The "stall" is a statistical construct, one created solely by how narrowly one decides to view the data.  It has no more relevance to what is happening in the Arctic than weather two weeks ago has on what will happen here tomorrow.
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El Cid

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Re: When will the Arctic Go Ice Free?
« Reply #224 on: December 08, 2018, 08:47:47 AM »
Maybe the "stall" is a statistical construct. Or maybe (a heresy to say on this site it seems) after the periphery melt out relatively quickly, the Central Arctic has different characteristics and will be a much harder nut to crack. In my opinion the "stall" is due to that the "easy" ice is gone and it is more difficult to melt the central parts. That is why you can not extrapolate from the past few years. The Central Arctic will be gone for (almost) sure but it is hard to model when in my view. Let me attach a picture how I see this whole process...

...the point is that the seeming stall could last only a very few but even a good many years as well

gerontocrat

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Re: When will the Arctic Go Ice Free?
« Reply #225 on: December 08, 2018, 09:04:15 PM »
Maybe the "stall" is a statistical construct. Or maybe (a heresy to say on this site it seems) after the periphery melt out relatively quickly, the Central Arctic has different characteristics and will be a much harder nut to crack. In my opinion the "stall" is due to that the "easy" ice is gone and it is more difficult to melt the central parts. That is why you can not extrapolate from the past few years. The Central Arctic will be gone for (almost) sure but it is hard to model when in my view. Let me attach a picture how I see this whole process...

There is a new paper that I think supports your contention. Basically it says that increased ocean heat transport (OHT) affects the Arctic seas over the continental shelves while it is the atmosphere that drives SIE in  the central arctic (over the deep ocean). (I can't access the full paper)

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2018JC014525
The role of ocean heat transport in rapid sea ice declines in the Community Earth System Model Large Ensemble
Quote
Abstract
Many climate models, including the the Community Earth System Model Large Ensemble (CESM‐LE), predict future rapid sea ice declines in the Arctic linked with anomalous northward Ocean Heat Transport (OHT). Using CESM‐LE, we find that the partitioning of the poleward OHT between the different Arctic gates (Barents Sea Opening (BSO), Bering Strait and Fram Strait) is key to this link with the rapid declines. 64 of the 79 rapid declines in CESM‐LE are correlated with the anomalous OHT through one of the gates. Rapid declines that happen earlier in the simulations when the sea ice covers the continental shelves are correlated with anomalous OHT. The interaction between OHT and sea ice happens mainly over continental shelves since most rapid declines are correlated with the BSO or Bering Strait OHTs and only a few with the Fram Strait OHT (often also correlated with BSO or Bering Strait OHTs). In most rapid rapid declines not correlated with OHT, the September Sea Ice Extent (SIE) prior to the decline is smaller than the area covered by the deep basins. Those are associated with surface heat flux since the ice‐atmosphere heat fluxes are more strongly correlated with the sea ice concentrations over the deep basins than the ice‐ocean heat fluxes. Our results suggest that OHTs are causing rapid sea ice declines when the SIE is large enough to cover the continental shelves and that the atmosphere is the main driver when the initial SIE is located only over the deep basins.

Plain Language Summary
A significant decrease in the minimum sea ice extent has been observed since the beginning of the satellite era in the late seventies. Several climate models simulate drastically different future evolution of the minimum sea ice extent. In this study, we use output diagnostics from the Community Earth System Model Large Ensemble to verify if the pathway of ocean heat transport entering the Arctic has an impact on the presence or absence of rapid sea ice declines. We find that the interaction between ocean heat transport and sea ice happens mainly over the shallow continental shelves. There, ocean heat transport can contribute to the melting of the sea ice. This melting is afterward enhance by positive feedbacks, such as the ice‐albedo feedback, and can lead to a rapid decline of the Arctic sea ice cover. In the central Arctic, the sea ice is more sensitive to atmospheric heat than to ocean heat.
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magnamentis

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Re: When will the Arctic Go Ice Free?
« Reply #226 on: December 08, 2018, 10:05:31 PM »
Maybe the "stall" is a statistical construct. Or maybe (a heresy to say on this site it seems) after the periphery melt out relatively quickly, the Central Arctic has different characteristics and will be a much harder nut to crack. In my opinion the "stall" is due to that the "easy" ice is gone and it is more difficult to melt the central parts. That is why you can not extrapolate from the past few years. The Central Arctic will be gone for (almost) sure but it is hard to model when in my view. Let me attach a picture how I see this whole process...

...the point is that the seeming stall could last only a very few but even a good many years as well

100% +1
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El Cid

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Re: When will the Arctic Go Ice Free?
« Reply #227 on: December 08, 2018, 10:55:32 PM »
Maybe the "stall" is a statistical construct. Or maybe (a heresy to say on this site it seems) after the periphery melt out relatively quickly, the Central Arctic has different characteristics and will be a much harder nut to crack. In my opinion the "stall" is due to that the "easy" ice is gone and it is more difficult to melt the central parts.

There is a new paper that I think supports your contention. Basically it says that increased ocean heat transport (OHT) affects the Arctic seas over the continental shelves while it is the atmosphere that drives SIE in  the central arctic (over the deep ocean). [/size]
[/quote]

Exactly! Although I am not a climate scientist, that is what I suspect: shallow seas are prone to ocean heat transport but the deep Arctic Center is not...although the quickly melting and more and more open periphery is probably chipping away the Center so it will eventually yield. To melt the Center we need exceptional weather currently. Maybe it will not be so in 10,20,30 yrs time, but it is probably so now.

Avalonian

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Re: When will the Arctic Go Ice Free?
« Reply #228 on: December 09, 2018, 12:12:30 AM »
The problem I have with this idea is that the deep water shouldn't come into play since there is a pycnocline at (iirc) around 70 m down - equivalent to the outer shelf depth. Warm water resulting in OHT to the central basin will be limited to flowing over this pycnocline (if that breaks down, then everything melts due to the heat of the deep saline water being mixed upwards). Of course, the warm water will cool as it heads north, but this effect is reduced the less peripheral ice there is remaining. Unless it can spread into a much thicker (deeper) layer, this OHT surely has just as much potential for melting the CAB ice as it does the peripheral seas.

I'm very willing to hear that I'm missing something fundamental here, but can anyone tell me what it is?

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Re: When will the Arctic Go Ice Free?
« Reply #229 on: December 09, 2018, 01:57:49 AM »
Can anyone comment on the short term, local impact that these "burps" have on local temperatures? There is a lot of talk about the the global impact but the local impact on temperatures might have global consequences that global radiative forcing might not account for.
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jdallen

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Re: When will the Arctic Go Ice Free?
« Reply #230 on: December 09, 2018, 02:13:03 AM »
Possibly relevant to this discussion, certainly prompted by it, I just posted an analysis of volume changes over on the volume and thickness thread Here:

https://forum.arctic-sea-ice.net/index.php/topic,2268.msg183686.html#msg183686
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oren

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Re: When will the Arctic Go Ice Free?
« Reply #231 on: December 09, 2018, 09:07:29 AM »
The central arctic is less prone to OHT but is very vulnerable to export through the very gates mentioned above, especially once the adjacent seas (the continental shelves) are cleared.
Incoming OHT tends to sink (warm and saline), but outgoing ice floats, so the water depth cannot save it, as it meets the OHT on the surface.
2016 winter and spring were a great example, and I think only luck brought about a stall in export further into the season, or we would have gotten a new record.

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Re: When will the Arctic Go Ice Free?
« Reply #232 on: December 09, 2018, 01:03:13 PM »
Great points everone! Much to think about. I have not much else to add. The trillion dollar question to me is: can and will mixing occur in the Central Arctic? If not, then export will probably be a slow way to get rid of all the ice and make the Central Arctic ice free.

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Re: When will the Arctic Go Ice Free?
« Reply #233 on: December 09, 2018, 02:24:57 PM »
Maybe the "stall" is a statistical construct. Or maybe (a heresy to say on this site it seems) after the periphery melt out relatively quickly, the Central Arctic has different characteristics and will be a much harder nut to crack. In my opinion the "stall" is due to that the "easy" ice is gone and it is more difficult to melt the central parts.

There is a new paper that I think supports your contention. Basically it says that increased ocean heat transport (OHT) affects the Arctic seas over the continental shelves while it is the atmosphere that drives SIE in  the central arctic (over the deep ocean). [/size]

Exactly! Although I am not a climate scientist, that is what I suspect: shallow seas are prone to ocean heat transport but the deep Arctic Center is not...although the quickly melting and more and more open periphery is probably chipping away the Center so it will eventually yield. To melt the Center we need exceptional weather currently. Maybe it will not be so in 10,20,30 yrs time, but it is probably so now.
[/quote]

I agree. I don't think it is entirely a coincidence that annual minimum ice cover appears to mimic the bathymetry of the Arctic Ocean.

Shared Humanity

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Re: When will the Arctic Go Ice Free?
« Reply #234 on: December 09, 2018, 02:28:41 PM »
Great points everone! Much to think about. I have not much else to add. The trillion dollar question to me is: can and will mixing occur in the Central Arctic? If not, then export will probably be a slow way to get rid of all the ice and make the Central Arctic ice free.

Dispersion into the shallower seas due to a stormy Arctic will help.

Shared Humanity

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Re: When will the Arctic Go Ice Free?
« Reply #235 on: December 09, 2018, 02:33:27 PM »
That Ocean Heat Transport is a primary contributor to melt and reduced SIE in shallow, peripheral seas might explain the dramatic changes in what use to be the refuge for some of the thickest MYI along the north of Greenland and the CAA.

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Re: When will the Arctic Go Ice Free?
« Reply #236 on: December 09, 2018, 07:35:17 PM »
That would certainly explain the steep drop in sea ice during the 90s, and the slower decrease in recent years.