When will Arctic Extent dip below 1,000,000 Km^2 (2022 poll)

[crandles]

It seems there is a degree of ambiguity on headline statement to some. I just noticed that someone is perhaps referring to the winter time disappearance year 2100 and beyond. That is a completely different thing to summer time as sea ice will keep forming in innumerable winters to come.

Good point.
I interpreted the poll as being the September minimum. Does the OP agree? Let's clarify that.

I can't modify the opening post any more so you will have to make do with the following saying just one day is sufficient (providing it is real not some glitch)

That is true, but I wanted to stick with the same question as last time and as this question says dips below and doesn't mention BOE it seems that one day will suffice if it is correctly measured not some glitch in the system for calculating the extent.

Hope that is ok.

[A-Team]

2026-30. Ice loss will be slow until isn't. Diminishing ice age means increasing brittleness and greater floe wind mobility which precondition the ice for an unfortunate but not unlikely sequence of unfavorable weather that bring abrupt collapse.

Right. We've noted before that 1 million sq km is arbitrary (has no special physical, geophysical, basin or bathymetric geometric significance) and that seasonally extensive effects of ice loss beyond the Arctic have already set in though scarcely limited to the day or month of Sept minimum.

These effects will continue to expand on the low side of 1 million sq km whether or not it brings a more radical 'state change'.

It's no longer so clear to me - despite well-established and continuing Arctic Amplification - that loss of sea ice will be the very first tipping point. It seems several other unwelcome effects of global warming are setting in far earlier than advertised. What is coming in later? We may become so preoccupied with these others so as to scarcely notice opening waters at the pole.

The reason for this is that straight thermodynamics (eg IPCC greenhouse) is only adequate at providing an upper bound, broad-brush climate change. We see that in ice models too, effects inconvenient to model and impossible to observe are brushed off, leading to understated linearity (note every function is linear in first order Maclaurin expansion).

Frankly there's a disconnect between Arctic models and satellite / buoy observations. That Polarstern year … all that planning, all the best people yet it came to naught as the ship blew straight through. Who predicted and explained the persistent polar dispersion we are seeing then and now?

The ENSO bit has gotten a bit silly across the board — one year they say "aha el nino, i told you so' but then it happens again during la nina so it becomes "aha la nina, i told you so' as if people can't remember what they said before. Going back and forth on the summer monsoon in the US southwest has lost them all credibility.

It doesn't work to use long term data averaging in a rapidly and unpredictably worsening climate. Effects having real but meagre statistical significance aren't determinative for a single year, often being swamped out by combinations of other developments.

[Michael Hauber]

A recent paper on ENSO effects on the Arctic:

"Record Low Arctic Sea Ice Extent in 2012 Linked to Two-Year La Niña-Driven Sea Surface Temperature Pattern"

By nudging observed tropical SSTs in a state-of-the-art coupled climate model, we identified the impact of tropical SST anomalies on the 2012 record low Arctic SIE. In the case when the tropical SSTs from 2010 to 2012 are nudged to the observations in the model, the dramatic Arctic sea ice loss in 2012 summer is reproduced well. Specifically, our model simulation demonstrates that La Niña conditions in the summer of 2010 and 2011 increased lower tropospheric temperature over the Pacific sector of the Arctic, whereas a negative phase of Pacific Meridional Mode (PMM) in 2012 strengthened the anomalous Greenland high and the associated transpolar drift of sea ice toward the Fram Strait.

Note the reference to the PMM, which is an expression of ENSO in the Northern Hemisphere, and whereas ENSO is dominated by east to west variability, PMM is dominated by north to south variability.  Also while the recent 2 year la nina has had no impact, the PMM has not really reflected a La Nina state and if anything the North East Pacific has been acting like it has been in an el nino mode through this period.

La Nina features strengthened high pressure systems in the east Pacific, which increase trade winds along the equator (E-W variation and ENSO).  But also the La Nina high pressure increases N-S winds in the NE Pacific and S-N winds in the NW Pacific (N-S variation hence PMM).  So this increases atmospheric heat transport in the NW Pacific, and I suspect that at least on some occasions this may extend into the Arctic.

[Richard Rathbone]

A recent paper on ENSO effects on the Arctic:

"Record Low Arctic Sea Ice Extent in 2012 Linked to Two-Year La Niña-Driven Sea Surface Temperature Pattern"

By nudging observed tropical SSTs in a state-of-the-art coupled climate model, we identified the impact of tropical SST anomalies on the 2012 record low Arctic SIE. In the case when the tropical SSTs from 2010 to 2012 are nudged to the observations in the model, the dramatic Arctic sea ice loss in 2012 summer is reproduced well. Specifically, our model simulation demonstrates that La Niña conditions in the summer of 2010 and 2011 increased lower tropospheric temperature over the Pacific sector of the Arctic, whereas a negative phase of Pacific Meridional Mode (PMM) in 2012 strengthened the anomalous Greenland high and the associated transpolar drift of sea ice toward the Fram Strait.

Note the reference to the PMM, which is an expression of ENSO in the Northern Hemisphere, and whereas ENSO is dominated by east to west variability, PMM is dominated by north to south variability.  Also while the recent 2 year la nina has had no impact, the PMM has not really reflected a La Nina state and if anything the North East Pacific has been acting like it has been in an el nino mode through this period.

La Nina features strengthened high pressure systems in the east Pacific, which increase trade winds along the equator (E-W variation and ENSO).  But also the La Nina high pressure increases N-S winds in the NE Pacific and S-N winds in the NW Pacific (N-S variation hence PMM).  So this increases atmospheric heat transport in the NW Pacific, and I suspect that at least on some occasions this may extend into the Arctic.

There's reference to work in the discussion of that paper which finds that 2012 was particularly strongly connected to the Pacific. There are quite a few papers cited that find the Pacific set up was important to 2012. Double La Nina certainly isn't sufficient for a high melt season, I don't think they've even shown its necessary, just that the state of the Pacific is important.

[binntho]

I voted for the first half of the next decade, don't ask me why.

I've always had an intuitive feeling that the ratio of open water to ice would become a critical factor well before we have 1m km2 left. The more open ocean, the bigger the waves and the more wind driven turbulence to bring up heat, and more space to push the remaining ice around in.

Looking at the map, this ratio should apply to the "continous" Arctic ocean, i.e. the CAB, Beaufort, Chuckhi, ESS and Laptev, with a total of just under 7m km2 or half the total Arctic. Most year sees some ice lingering outside of this area, but the very lowest years such as 2012 have almonst no ice outside the seas mentioned above.

And even 2012 only just managed a 50/50 proportion of ice to open water on average in September.

However, once extent starts to trend even lower, say towards 2m km2 average for September, this ratio becomes 70/30, i.e. more than twice as much open water as ice. Given a typical speed of melt, on average more than half of the continous Arctic would be open water for the three month period of july-september.

I don't think the remaining ice would survive this scenario - constant wind and wave action, winddriven turbulence and the ice being pushed around. Which basically means that there is no point talking about 1m km2 as something that will be reached as part of a continous decline. There will have been a total collapse well before.

[crandles]

https://www.realclimate.org/index.php/archives/2019/02/the-best-case-for-worst-case-scenarios/

Interesting read, not quite sure where to post it but perhaps this part belongs here

There are plenty of scientists happy to make dramatic predictions (with varying levels of competence). Wadhams and Mislowski made dramatic predictions of imminent Arctic sea ice loss in the 2010s (based on nothing more than exponential extrapolation of a curve) with much misplaced confidence. Their critics (including me) were not ESLD { ‘erring on the side of least drama’} when they pointed out the lack of physical basis in their claims. Similarly, claims by Keenlyside et al in 2008 of imminent global cooling were dramatic, but again, not strongly based in reality.  But these critiques were not made out of a fear of more drama. Indeed, we also made dramatic predictions about Arctic ozone loss in 2005 (but that was skillful).

[Jim Hunt]

Wadhams and Mislowski made dramatic predictions of imminent Arctic sea ice loss in the 2010s (based on nothing more than exponential extrapolation of a curve) with much misplaced confidence.

Gavin's memory seems to have let him down somewhat. Wieslaw Maslowski made a linear projection of sea ice volume, but was rather misrepresented by Al Gore:

https://GreatWhiteCon.info/2013/09/shock-news-why-isnt-the-arctic-ice-free/

[The Walrus]

"Given the estimated trend and the volume estimate for October–November of 2007 at less than 9,000 km3, one can project that at this rate it would take only 9 more years or until 2016 ± 3 years to reach a nearly ice-free Arctic Ocean in summer. Regardless of high uncertainty associated with such an estimate, it does provide a lower bound of the time range for projections of seasonal sea ice cover."

https://www.annualreviews.org/doi/full/10.1146/annurev-earth-042711-105345

Of course, that was his second attempt.  His first claim was an ice-free Arctic by 2013.
"Our projection of 2013 for the removal of ice in summer is not accounting for the last two minima, in 2005 and 2007.  So given that fact, you can argue that may be our projection of 2013 is already too conservative."

http://news.bbc.co.uk/2/hi/7139797.stm

[Jim Hunt]

And your point is Walrus? Here's another extract from my helpful link above:

Instead of relying on what David Rose says Jonathan Amos says Wieslaw Maslowski said, why don’t we instead take a look at what Prof. Maslowski actually said...

Note that he didn’t say words to the effect that “The Arctic will be ice-free in summer by 2013” as claimed by David Rose. What he actually said, and converting the mathematical symbol into plain English, was "IF this trend persists the Arctic Ocean will become ice-free by AROUND 2013!" which is a very different thing.

As I pointed out elsewhere:

For the benefit of those who seem unable to understand either English or Mathematics, a “projection” is not the same thing as a “prediction”.

[Juan C. García]

2012 was a very bad year. Some of us were in contact with Neven, when he forecasted a huge drop, some days before the Great Arctic Cyclone. After 2012, we have been waiting to break this record. But it has not happened. It has passed 10 years, but 2012 is still the lowest on record.

From my point of view, there is a strong negative feedback influencing the ASI melting. Even that I haven’t see scientific studies saying this, I think that the strong negative feedback is the melting of ice above land, also the melting of ice above sea that is attached to land ice sheets, and finally, the melting of permafrost at the Arctic coast.

What I expect to happen is that the Arctic sea ice will melt at a slower pace. Some new records, maybe some strong low records, but returning to several bounces again.

But the oceans are now melting the Greenland ice. OMG: Oh, my God! Oceans Melting Greenland! And I think that in the following years, what we are going to see is the acceleration of sea level rise. Because oceans are not only melting Greenland ice. They are also melting Antarctic ice. These melting ice temporarily cools all oceans, and on greater extent, they cool the Arctic Ocean.

So, well, we will have to wait another 20 or 30 years, to see if I am right.

My vote goes for the 2041-2050 range, on this poll.

[The Walrus]

And your point is Walrus?

He extrapolated a straight line from the steepest part of the curve, and wrote "If this trend persists the Artic Ocean will become ice-free by ~2013!"

https://www.academia.edu/75754012/When_will_Summer_Arctic_Sea_Ice_Disappear

There is a term here for those who do that, and it is no wonder that his predictions failed to come true.

[Paul]

I think we got to remember also the 2012 extent number was so low that there was always a chance it could take a long time for it to be broken again. Also other factors would include the summer melt until August was within the  previous low years and it only separated during August thanks no doubt In part due to the GAC. This meant unlike in 2020, refreeze quickly shot the extent back up again and ice in the ESS for example formed quicker than other years.

Until the ice becomes mostly 1 year old ice, I just can't see how we get a BOE anytime soon with any ice to the 'left' of the pole being more resilient.

[oren]

When will the Arctic extent dip below 1 M km2? When 2007 weather strikes again, a combination of sun, warmth, export and compaction.
A couple of animations prepared by uniquorn and posted in the test thread, which I thought were too interesting to leave there.
Note how quickly and how sharply thickness drops in May-July in large swaths of the Chukchi, ESS and Beaufort. Eventually by season end this destroyed a significant part of the MYI that was helping the ice survive in these regions. Also note how during both winter and summer the ice keep moving towards the Fram. The end result took the ice a very large notch down, from which it has never really recovered.
Just wondering if anyone thinks that such weather cannot return, or is so rare as to require decades to repeat. A reminder that after 5 years there was 2012 weather, a different breed of the monster.

[uniquorn]

The 2007 Bering Strait oceanic heat flux and anomalous Arctic sea-ice retreat
Rebecca A. Woodgate, Tom Weingartner, Ron Lindsay
First published: 07 January 2010  https://doi.org/10.1029/2009GL041621 Citations: 285

Abstract

[1] To illuminate the role of Pacific Waters in the 2007 Arctic sea-ice retreat, we use observational data to estimate Bering Strait volume and heat transports from 1991 to 2007. In 2007, both annual mean transport and temperatures are at record-length highs. Heat fluxes increase from 2001 to a 2007 maximum, 5–6 × 1020 J/yr. This is twice the 2001 heat flux, comparable to the annual shortwave radiative flux into the Chukchi Sea, and enough to melt 1/3rd of the 2007 seasonal Arctic sea-ice loss. We suggest the Bering Strait inflow influences sea-ice by providing a trigger for the onset of solar-driven melt, a conduit for oceanic heat into the Arctic, and (due to long transit times) a subsurface heat source within the Arctic in winter. The substantial interannual variability reflects temperature and transport changes, the latter (especially recently) being significantly affected by variability (> 0.2 Sv equivalent) in the Pacific-Arctic pressure-head driving the flow.

[Richard Rathbone]

Some people do think it takes decades.

Fingerprints of internal drivers of Arctic sea ice loss in observations and model simulations

https://www.nature.com/articles/s41561-018-0256-8

This simulated internal variability shows a strong similarity to the observed Arctic atmospheric change in the past 37 years.  Through a fingerprint pattern matching method, we estimate that this internal variability contributes to about 40–50% of observed multi-decadal decline in Arctic sea ice.

Also MYI volume is not the same as FYI area. MYI volume became unstable sometime in the late 20th century and it was essentially gone by 2010. FYI area has a stable trend because open arctic water loses heat far more rapidly in the autumn than it accumulates during the summer. Consequently extrapolating trends from MYI into FYI has led to spectacularly failed BOE predictions during the past decade.

[uniquorn]

A shame that article is paywalled. Here is a free access one attempting to link atmo and ocean.

Recent upper Arctic Ocean warming expedited by summertime atmospheric processes
Zhe Li 1 , Qinghua Ding 1 ✉, Michael Steele2 & Axel Schweiger 2
Open Access   Published: 18 January 2022
https://www.nature.com/articles/s41467-022-28047-8

The observed upper (0–50 m) Arctic Ocean warming since 1979 has been primarily attributed
to anthropogenically driven changes in the high latitudes. Here, using both observational
and modeling analyses, we demonstrate that a multiyear trend in the summertime large-scale
atmospheric circulation, which we ascribe to internal variability, has played an important role
in upper ocean warming in summer and fall over the past four decades due to sea ice-albedo
effect induced by atmospheric dynamics. Nudging experiments in which the wind fields are
constrained toward the observed state support this mechanism and suggest that the internal
variability contribution to recent upper Arctic Ocean warming accounts for up to one quarter
of warming over the past four decades and up to 60% of warming from 2000 to 2018. This
suggests that climate models need to replicate this important internal process in order to
realistically simulate Arctic Ocean temperature variability and trends.

extract:

Discussion
Our study suggests that a portion of upper Arctic Ocean warming over the past few decades can be explained by low-frequency atmospheric variability characterized by a trend toward anomalous anticyclonic circulation over the Arctic Ocean and Greenland. This process produces subsidence and adiabatic warming which acts to warm the atmosphere, melt sea ice, and deepen the ocean mixed layer. The resulting open water warms via shortwave radiation absorption and enhanced vertical mixing.
 Our nudging experiments confirm that adiabatic dynamical forcing associated with winds in the Arctic is able to explain up to 24% of SON upper ocean warming from 1979 to 2018, which is mostly confined to the Chukchi, East Siberian, and Laptev Seas, and up to ~60% of the Pan-Arctic upper ocean warming for the period 2000–2018.

SON Sep-Nov

4th image is a crop from the Fig3, gateways are shown centre

b SON upper 50m POHT through the Atlantic Ocean gateway in a (blue line), c SON upper 50m POHT through the Pacific Ocean gateway in a (red line).

[Steven]

When will the Arctic extent dip below 1 M km2? When 2007 weather strikes again, a combination of sun, warmth, export and compaction.

Would it really?

The image below shows the 2007 volume loss between early May and mid September 2007 according to PIOMAS.  If such volume loss were to happen again one of the next years, it would not cause a BOE.  Not enough melt for the high latitudes and Atlantic side.  To get a BOE, it needs strong melt weather over basically the entire Arctic ocean, not just on the Pacific side. 

On the other hand, since the ice is generally thinner and younger than in 2007 the albedo feedback could start earlier, enhancing the volume loss.  But to just assume that a repeat of 2007 weather would automatically cause a BOE seems highly dubious to me.

A shame that article is paywalled.

There's a pdf of it here: https://par.nsf.gov/servlets/purl/10095527

[The Walrus]

Some people do think it takes decades.

Fingerprints of internal drivers of Arctic sea ice loss in observations and model simulations

https://www.nature.com/articles/s41561-018-0256-8

This simulated internal variability shows a strong similarity to the observed Arctic atmospheric change in the past 37 years.  Through a fingerprint pattern matching method, we estimate that this internal variability contributes to about 40–50% of observed multi-decadal decline in Arctic sea ice.

Also MYI volume is not the same as FYI area. MYI volume became unstable sometime in the late 20th century and it was essentially gone by 2010. FYI area has a stable trend because open arctic water loses heat far more rapidly in the autumn than it accumulates during the summer. Consequently extrapolating trends from MYI into FYI has led to spectacularly failed BOE predictions during the past decade.

The loss of MYI volume during that time accounts for the large drop in sea ice area.  Once gone, the decline in minima extent appears to have returned to the same trend as before the loss was initiated.

[uniquorn]

Thanks Steven. Towards the end of 'Fingerprints of internal drivers of Arctic sea ice loss in observations and model simulations' it says this:

The importance of the low latitude–high latitude linkages in the analysis of sea ice sensitivities is masked by the fact that global temperatures not only drive sea ice loss but also respond to sea ice retreat and thinning. In fact, as much as 30% of global surface air temperature change may be in response to sea ice loss rather than being driven by it

ASI probably doesn't need to be the canary in the coal mine any more. We have wild fires, drought and flooding for that now.

[oren]

When will the Arctic extent dip below 1 M km2? When 2007 weather strikes again, a combination of sun, warmth, export and compaction.

Would it really?

The image below shows the 2007 volume loss between early May and mid September 2007 according to PIOMAS.  If such volume loss were to happen again one of the next years, it would not cause a BOE.  Not enough melt for the high latitudes and Atlantic side.  To get a BOE, it needs strong melt weather over basically the entire Arctic ocean, not just on the Pacific side. 

On the other hand, since the ice is generally thinner and younger than in 2007 the albedo feedback could start earlier, enhancing the volume loss.  But to just assume that a repeat of 2007 weather would automatically cause a BOE seems highly dubious to me.

I do realize my statement above was overconfident... but here are some more details relevant to the claim. The "secret" of 2007 weather was for the whole annual cycle, not just summer. I am quoting a post I made back in 2020 when I had some more time, showing overall year over year loss. Seems 2007 was a winner thanks to both a vigorous summer and a poor preceding winter, my guess is the export engine worked all year, but I lack the means to dig deeper.
Certainly a day 266 to day 266 PIOMAS or a mid-Sep to mid-Sep difference graphic could be useful.

Also bear in mind that after 2007 both gains and losses grew larger, an obvious consequence of the loss of MYI and the increased open water at summer end, so a comparison of just summer to summer or just winter to winter is problematic.

Indeed, here is an expanded version of that post which is found upthread. As my PIOMAS Excel is built around Wipneus data, the following only looks at daily data since 2000.
For each year, I look at the volume gain over the preceding autumn and winter, starting at day 266 of the previous year (~Sep 23rd) and ending at day 121 of that year (~May 1st). Then I look at the volume loss over that year's spring and summer, until day 266. The four worst years in each column are bolded. The results are quite interesting.
Indeed, 2007 is the winner for total net loss. However, its main claim to fame should be the low winter gain. Its summer loss was high for its time but nothing much compared to later years. Looking at the data in chart form clearly shows that something was different after 2007, much higher losses and much higher gains as a larger part of the Arctic participated in the seasonal cycle. In my next post I will look at the various regions, and attempt to find out where the missing 2007 winter volume was located.
In general, high net losses typically occur in years that had a low winter gain compared to their surrounding neighbors, marked in the chart. Also marked is 2017, the year the Arctic dodged a cannonball despite poor winter gain, by having the lowest summer loss since 2004.
In addition, most top years for high summer losses were also top years for high early summer losses.

Click to enlarge images.

[trm1958]

or is so rare as to require decades to repeat.

It would be decades expected, not 'required'. That is similar to the gambler's fallacy.

[Steven]

I do realize my statement above was overconfident... but here are some more details relevant to the claim. The "secret" of 2007 weather was for the whole annual cycle, not just summer. I am quoting a post I made back in 2020 when I had some more time, showing overall year over year loss. Seems 2007 was a winner thanks to both a vigorous summer and a poor preceding winter, my guess is the export engine worked all year, but I lack the means to dig deeper.

There was indeed strong export during the 2006/2007 freezing season from the Pacific side toward the Atlantic side of the Arctic and particularly toward Fram Strait.  That may have preconditioned the Pacific side.

But that doesn't really change the point.  Regardless of export, most of the ice at the high latitudes would be over 2 meters thick at the start of the melt season.  The weather pattern in Summer 2007 caused strong melt on the Pacific side, but mediocre melt for the high latitudes.  I don't see how that weather pattern could lead to a BOE, at least not in the current climate.  Maybe it could after several more decades of global warming, or with a modified weather pattern that combines the worst parts of 2007, 2016 and 2020, but that seems really low probability.

[Comradez]

I do think that some of the "burden" of a BOE will need to be shouldered by having lower winter maxima, in addition to having more melt out in the summer seasons.  I don't think we can get to a BOE as long as there is still substantial winter ice in the Bering and Barents seas. 

If we start to see winters where the ice never makes it past the Bering straight, and simultaneously also fails to make it past a line on the Atlantic side marked by Svalbard/Franz Josef Land/Novaya Zemlya, then maybe we can start talking about the possibility of Blue Ocean Events in the summers afterwards. 

[Paul]

I do think that some of the "burden" of a BOE will need to be shouldered by having lower winter maxima, in addition to having more melt out in the summer seasons.  I don't think we can get to a BOE as long as there is still substantial winter ice in the Bering and Barents seas. 

If we start to see winters where the ice never makes it past the Bering straight, and simultaneously also fails to make it past a line on the Atlantic side marked by Svalbard/Franz Josef Land/Novaya Zemlya, then maybe we can start talking about the possibility of Blue Ocean Events in the summers afterwards.

I think its more down to ice thicknesses rather than extent personally. I do think ice in the bering sea has little to no effect on ice extent by the end of summer and we have seen at times in the last decade of the Barants sea lacking ice but yet still no significant effects on the ice although an ice free Barants has more chance of having an effect if warming continues as it is.

Years like 2007 and 2020 did follow winters with a positive AO but a positive AO does seemingly tend to compact ice more towards the CAA so even though a positive AO may increase the chances of a record low(due to poor thickness across the Siberian Arctic), it may favour less chance of a blue ocean event especially if the summer is high pressure dominated as the ice stays compact although very warm SSTS may eventually override that and we did see that in 2020 in particular but the reality is, the CAB is a different environment than areas closer to landmasses.

[El Cid]

I do think that some of the "burden" of a BOE will need to be shouldered by having lower winter maxima, in addition to having more melt out in the summer seasons.  I don't think we can get to a BOE as long as there is still substantial winter ice in the Bering and Barents seas. 

If we start to see winters where the ice never makes it past the Bering straight, and simultaneously also fails to make it past a line on the Atlantic side marked by Svalbard/Franz Josef Land/Novaya Zemlya, then maybe we can start talking about the possibility of Blue Ocean Events in the summers afterwards.

I totally agree with that. And the reason is that this would show that enough hot water from the tropics has reached the Arctic to keep these areas open even during winter. This would show that heat content near the surface is very high and that heat then would melt enough Central Arctic Ice during the summer to create the conditions for a BOE.

[HapHazard]

IDK, I can see it melting from the middle. More rubblefication and who knows. That low concentration area near the pole - that only needs to happen a bit more aggressively and lookout.

[The Walrus]

I do think that some of the "burden" of a BOE will need to be shouldered by having lower winter maxima, in addition to having more melt out in the summer seasons.  I don't think we can get to a BOE as long as there is still substantial winter ice in the Bering and Barents seas. 

If we start to see winters where the ice never makes it past the Bering straight, and simultaneously also fails to make it past a line on the Atlantic side marked by Svalbard/Franz Josef Land/Novaya Zemlya, then maybe we can start talking about the possibility of Blue Ocean Events in the summers afterwards.

I totally agree with that. And the reason is that this would show that enough hot water from the tropics has reached the Arctic to keep these areas open even during winter. This would show that heat content near the surface is very high and that heat then would melt enough Central Arctic Ice during the summer to create the conditions for a BOE.

I agree also.  Comparing the minimum, maximum and average sea ice extent, only the minima show a steep decline during the late 90s and early 2000s.  In addition to 2007, the ice was low for much of the year in 1995 and 2016 as well.  The rest of the years show a slow decline.  Hence, I tend to agree ith Steven that it will be many more decades before we witness a BOE. 

It would take at least two 2007-type years, where the minimum dropped 1.6 M km2 from the preceding summer, to fall below the one million threshhold.  Since that has only occurred once in the four+ decades of satellite monitoring, and the second largest drop (0.95 M from 2011 to 2012) was significantly less, a BOE is unlikely in my lifetime (granted I am older than most, but I still expect to live a few more decades).

[Comradez]

If the Bering Sea remains almost totally ice-free all year round (I say almost because there will still probably be sea ice in sheltered bays for a long time like around Nome), it will warm up very quickly each April, and this will jumpstart the Chukchi melt.  And if the Chukchi Sea ice ever starts getting pushed back to around the Wrangel Island latitude by the first week of May, it will be game over.  That will be too much heat and insolation on the Pacific side too early to give the entire Pacific side any chance of survival.   

On the Atlantic front, an ice-free Barents Sea will jumpstart the Kara and Laptev Sea melts, which will in turn jumpstart the CAB melt later in the summer.  Note that in 2012 the Kara Sea had nearly melted out completely by early June.  I think this is an underappreciated aspect of the 2012 melt.  If the Kara and Laptev Seas begin to almost totally melt out by the first week of June, then the Atlantic sea ice will be toast. 

When both things happen at the same time (Pacific and Atlantic sides), then the CAB will be well set-up for a near full melt-out. 

When it comes to the other peripheral seas (Hudson Bay, Baffin Bay), I don't think there is enough of an oceanic/atmospheric connection to really matter for the rest of the arctic whether they melt out early or late, and I also think it will be a long long time before these cease to freeze completely over anyways because of continental climate influence. 

[Comradez]

Another way to look at a blue-ocean-event:  the arctic sea ice would probably need to be in mid-Sept. 2012's state by mid-August, or 1 month earlier.  That either means a BOE year would need to start off essentially 1 month ahead of 2012 and maintain the distance, or have some combination of an earlier start and even more vigorous melt (although I doubt whether a year's melt could be much more vigorous than 2012's).

Let's say, charitably, we split it half and half.  That means a BOE year would need to start off about 2 weeks ahead of 2012 in mid-April, and would need to gain a week on 2012 every two months, so that by mid-June the BOE year would need to be 3 weeks ahead of 2012 and then by mid-August would be 4 weeks ahead of 2012 and essentially in the condition of 2012's mid-September ice. 

3 weeks ahead of mid-June is roughly around the 4th of July.  Here's what 2012's ice looked like on July 4th, 2012.  A BOE year would, I would wager, need to reach this state by mid-June, or at the very least by the June solstice.  This means:
*Kara Sea ice-free. 
*Large ice-free Laptev bight
*Large ice-free Beaufort bight about the width of Banks Island
*The Chukchi icefront nearly reaching Wrangel Island
*(Ideally) a snow-free CAA and signs of breakup beginning in the main CAA channel.  A nice proxy for this is when you see the lakes on Victoria Island beginning to melt out. 
*(Ideally) signs of occasional loose floes/rubble here and there in the CAB proper.

[WildFit]

I do think that some of the "burden" of a BOE will need to be shouldered by having lower winter maxima, in addition to having more melt out in the summer seasons.  I don't think we can get to a BOE as long as there is still substantial winter ice in the Bering and Barents seas. 

If we start to see winters where the ice never makes it past the Bering straight, and simultaneously also fails to make it past a line on the Atlantic side marked by Svalbard/Franz Josef Land/Novaya Zemlya, then maybe we can start talking about the possibility of Blue Ocean Events in the summers afterwards.

I think its more down to ice thicknesses rather than extent personally. I do think ice in the bering sea has little to no effect on ice extent by the end of summer and we have seen at times in the last decade of the Barants sea lacking ice but yet still no significant effects on the ice although an ice free Barants has more chance of having an effect if warming continues as it is.

Years like 2007 and 2020 did follow winters with a positive AO but a positive AO does seemingly tend to compact ice more towards the CAA so even though a positive AO may increase the chances of a record low(due to poor thickness across the Siberian Arctic), it may favour less chance of a blue ocean event especially if the summer is high pressure dominated as the ice stays compact although very warm SSTS may eventually override that and we did see that in 2020 in particular but the reality is, the CAB is a different environment than areas closer to landmasses.

Instead of opposing each other simply combine the two valid theories and we're probably quite close to the truth.

😂

[Glen Koehler]

     Good discussion, but most of the reasoning assumes continuity in system behavior.  Granted, IPCC (or was it Stroeve and Notz 2018?, or some other expert opinion?) have said there are no identifiable tipping points with respect to future ASI decline.  I have no standing to disagree with that, but I will anyway...
   
     It seems to me that the gradualist, "continualist" perspective ignores some very potent discontinuous saltatory possibilities.
     Contributing factors:
     * Continued winter warming and less refreeze, especially with more extensive open water at end of the previous melt season.
     * Younger, saltier, thinner, weaker, less concentrated ice.
     * Rubblified/slushified ice with less (or no) pack constraint on movement.
     * Increase of ocean heat absorption through reduced albedo through earlier (thus closer to solstice) and more extensive open water and melt pond area.
     * More open water also leads to more dynamic ocean to air energy transfer and less thermal isolation.
     * Lower ice-to-water ratio allows a higher portion of heat energy to go into warming water vs. high thermal input required to melt ice.
     * Warmer and more dynamic Arctic atmosphere leads to stronger incursions of storm-driving warm air masses, including warm rain that can devastate ice.
     * Continued warming of Atlantic, Pacific, and land-based water infiltration increases heat energy at the surface and subsurface.
     * More active atmosphere and longer wind fetch over open water leads to greater wave action and vertical heat cycling.  Even if that is not enough break through the thermocline it would still result in greater upward heat diffusion.  And it might bring thermocline to surface in shallow areas.
     * Hansen and others suggest that the global surface temperature increase may itself exceed the linear trend as warming oceans and saturated vegetation no longer continue to absorb CO2 additions at the same rate.  In 2022 we are just past the bottom of the solar cycle (temperature response lags solar radiation curve by 1-2 years) and in a prolonged but probably fading La Nina phase.  In 5 years the solar cycle will be reaching max upward influence and odds are that El Nino of some degree will be in effect.
     * Less constricted export gateways through the CAA, Nares, and/or Fram.
 
     Bonus/fantasy factor:  I wonder what happens if/when Atlantic water incursion along the Siberian coast joins up with the Pacific water influx current that hugs the Alaskan-Canadian coast.  Will that create an Arctic Ocean-wide toilet bowl swirl that functions as the equivalent of an 'anti-Beaufort Gyre MYI nursery' (RIP) that sweeps ice out of the Arctic Ocean through the southern-facing exit doors before it even has a chance to melt in place? 

     All of these forces are gathering strength simultaneously.  While none of them individually is a tipping point, they have synergistic effects that could result in a tipping vortex not too many years from now.  5+5 =10.  But 5*5 = 25.

     Yes, I am ignoring negative feedbacks, but the exacerbating positive feedbacks in the foreseeable future seem to outweigh the suppressive negative feedbacks.  Moreover, the more we learn about climate change, the new information more frequently (by a large margin) points to more rapid and radical change vs. less. Just this week Greenland melt rate estimate between now and 2100 essentially doubled.  Just today new study that ECS temperature sensitivity to CO2 in past climates may be much higher than previously estimated due to low bias in oxygen isotope methodology.  As for the "Slow Transition", yes FYI Extent increases rapidly.  But in doing so it also creates a thin winter cover to hold in ocean heat during winter yet easily melted out the following summer, so there is no salvation there.

     Extrapolating the straight-line trend of ASI volume decline suggests ~ 2030 for individual year chance of BOE reaching 50%.  That trend was "tainted" by the rapid loss of MYI in the early 2000s, and the most recent 10 years have flatlined.  But the observation that a single linear trend does not apply demonstrates that the ASI does not evolve in a smooth year-to-year progression.  Instead it occurs as jumps between periods of punctuated equilibrium (just like biological evolution).  The 42-year satellite-era record of ASI decline could be summarized as 22 years slow, 10 years fast, 10 years slow.  The next 10 years may continue slow, but when the dam breaks the transition is likely to be precipitous.  Convergence of a warm winter followed by strong early season melt weather, then a summer mid-latitude scale storm (Arctic hurricane?) compounded by high melt rate from greater portion of a shallower larger reservoir of subsurface heat reaching the surface compounded by mass export and lack of recharge from a depleted ESS/Laptev could synergistically cause a BOE within 10 years. 

     BOE won't happen this year.  And it won't happen next year. And it won't happen for X years.  Then in year Y it will happen in a flash surprising everybody.

     The 2022 melt season is more interesting than a 12th place final Extent or Area minimum.  As slushification continues a new more vulnerable Arctic is emerging.  One example is the (new to me at least) continuous bleeding of ice through the Nares Strait all summer long.  Ice that in the past would have piled up as fortress-like rafts against the CAA-CAB boundary.  Not this time, and probably not again for a very long time.

[Stephan]

Very well and comprehensively written, Glen.
Worth a "like", if not two.

[binntho]

     Good discussion, but most of the reasoning assumes continuity in system behavior.  Granted, IPCC (or was it Stroeve and Notz 2018?, or some other expert opinion?) have said there are no identifiable tipping points with respect to future ASI decline.  I have no standing to disagree with that, but I will anyway...

Thanks Glen. I agree with Stephan, a very comprehensive overview. Personally I have long felt that the forces causing the annual melt of Arctic Sea Ice can be divided into two categories - those originating outside the Arctic, and those originating inside the arctic.

The first category is basically atmospheric and ocean currents. The temperatures of both keep increasing at a rate close to linear on a decadal scale - but clouds (which belong to both categories) is a complicating factor, causing negative or (more often) positive temperature feedback. Increased kinetic energy in the global atmospheric system is also a factor (more wind) as is increased water vapor (more heat content, more efficient heat transfer).

The second category has traditionally been summer insolation and little else. But as you point out, with ever more open water, effects originating inside the Arctic become ever more important - much lower albedo of open water, increased wave action, increased dispersion etc. but also changes in cloudiness with unforeseen consequences. This is where I would expect a tipping point to originate from. There will come a year when all the different factors cooperate for a massive melt, and the coup de grace will be from the internal and not the external factors.

But a very important point to keep in mind: The Arctic has practically no memory from one year to another (as opposed to the multiyear memory which expresses itself in less MYI, less winter thickness). This means that every melt season is basically on its own, and the coming together of all the factors to create a perfect melt year could probably happen any year.

[dnem]

But a very important point to keep in mind: The Arctic has practically no memory from one year to another (as opposed to the multiyear memory which expresses itself in less MYI, less winter thickness). This means that every melt season is basically on its own, and the coming together of all the factors to create a perfect melt year could probably happen any year.

Great summary, Glen. Perfectly expands my glib and lazy "The transition will be slow until it isn't."

Not sure I get this last point, Bintho. The question of the degree of hysteresis in the arctic is critical. I think you are saying that wrt to the weather, there is no hysteresis (which is the definition of weather as opposed to climate), but that the steady decline of MYI and warmer winters does increase the arctic's vulnerability as we move forward. To me, a very key question is when the forces do align, and we get a big summer blowout that pushes the arctic to new lows, will the system have a hard time recovering and fall into a new dynamic equilibrium from which it can't climb out of? If so, that would mark the end of the slow transition and the arrival of a new regime, together with major knock-on effects in the larger climate system.

[binntho]

But a very important point to keep in mind: The Arctic has practically no memory from one year to another (as opposed to the multiyear memory which expresses itself in less MYI, less winter thickness). This means that every melt season is basically on its own, and the coming together of all the factors to create a perfect melt year could probably happen any year.

Great summary, Glen. Perfectly expands my glib and lazy "The transition will be slow until it isn't."

Not sure I get this last point, Bintho.

The point is very clear. The Arctic has almost no annual memory - none of the behaviour of one year has any predictive value for the following year. But decadal (or multi-year) memory is another thing. Every decade, the lows are lower and the maximus are lower as well, the ice is thinner etc. etc.

But if you want to rephrase this in hysteresic climate-vs-weather terms, that's fine. Both mean the same thing.

[The Walrus]

But a very important point to keep in mind: The Arctic has practically no memory from one year to another (as opposed to the multiyear memory which expresses itself in less MYI, less winter thickness). This means that every melt season is basically on its own, and the coming together of all the factors to create a perfect melt year could probably happen any year.

Great summary, Glen. Perfectly expands my glib and lazy "The transition will be slow until it isn't."

Not sure I get this last point, Bintho.

The point is very clear. The Arctic has almost no annual memory - none of the behaviour of one year has any predictive value for the following year. But decadal (or multi-year) memory is another thing. Every decade, the lows are lower and the maximus are lower as well, the ice is thinner etc. etc.

But if you want to rephrase this in hysteresic climate-vs-weather terms, that's fine. Both mean the same thing.

There is no true hysteresis effect in the Arctic.  Whether the current situation arose from increasing sea ice or decreasing is irrelevent.  The current condition is what is important.  Your memory statement is inaccurate.  While the most recent decade experienced a lower maximum, there has not been a lower minimum.

[dnem]

I don't think we have much of an idea how much hysteresis arctic sea ice will exhibit. The time series is short and the perturbations are increasing. I believe it remains entirely plausible that the ice will be pushed into a new regime from which it won't be able to escape, particularly as the perturbations will only continue to increase in the direction of more warmth and more melt.

[be cause]

It's being pushed pretty hard atm .

[The Walrus]

I don't think we have much of an idea how much hysteresis arctic sea ice will exhibit. The time series is short and the perturbations are increasing. I believe it remains entirely plausible that the ice will be pushed into a new regime from which it won't be able to escape, particularly as the perturbations will only continue to increase in the direction of more warmth and more melt.

Since Arctic sea ice is governed by the laws of physics, we do have a rather good idea of potential hysteria.

https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2011GL048739

"the hysteresis effect has nearly completely disappeared. Starting at a fully frozen planet or fully unfrozen planet results in the same outcome"

https://www.scirp.org/journal/paperinformation.aspx?paperid=73585

[dnem]

I only looked at the first one, and unsurprisingly, it's not relevant. The dynamic equilibrium described by the cartoon I posted can be thought about in two major ways. In the first, the magnitude of the "push" on the ball is drawn from some fixed distribution, so the likelihood of drawing a big enough push to drive the ball up and over the hump and into the adjacent, lower basin, is dependent on the parameters of the distribution.

The second way is if the distribution from which the push comes is not fixed, but is shifting continually to include more energetic "pushes". That's the situation we are in. The likelihood of the biggest ever (in the satellite record) push increases every year.

The first paper models increasing and then DECREASING CO2:
"We test sea ice reversibility within a state-of-the-art atmosphere–ocean global climate model by increasing atmospheric carbon dioxide until the Arctic Ocean becomes ice-free throughout the year and subsequently decreasing it until the initial ice cover returns."

That might be an interesting exercise but isn't relevant.

I can't say that there is unequivocally an adjacent, lower, basin as shown in my cartoon. Maybe the long and cold arctic night will always be enough to push the system back into the first basin. But I can say, if there is a second basin, all we know is that 2007, 2012, 2018, whatever, didn't provide a sufficient push to get us over. It's hubris to say that push can't exist. And the odds of it coming up are increasing every year, and will continue to do so for decades.

[The Walrus]

I only looked at the first one, and unsurprisingly, it's not relevant. The dynamic equilibrium described by the cartoon I posted can be thought about in two major ways. In the first, the magnitude of the "push" on the ball is drawn from some fixed distribution, so the likelihood of drawing a big enough push to drive the ball up and over the hump and into the adjacent, lower basin, is dependent on the parameters of the distribution.

The second way is if the distribution from which the push comes is not fixed, but is shifting continually to include more energetic "pushes". That's the situation we are in. The likelihood of the biggest ever (in the satellite record) push increases every year.

The first paper models increasing and then DECREASING CO2:
"We test sea ice reversibility within a state-of-the-art atmosphere–ocean global climate model by increasing atmospheric carbon dioxide until the Arctic Ocean becomes ice-free throughout the year and subsequently decreasing it until the initial ice cover returns."

That might be an interesting exercise but isn't relevant.

I can't say that there is unequivocally an adjacent, lower, basin as shown in my cartoon. Maybe the long and cold arctic night will always be enough to push the system back into the first basin. But I can say, if there is a second basin, all we know is that 2007, 2012, 2018, whatever, didn't provide a sufficient push to get us over. It's hubris to say that push can't exist. And the odds of it coming up are increasing every year, and will continue to do so for decades.

Actually, it is entirely relevent. 

Hysteresis means that similar conditions will produce different outcomes, when arriving at those conditions from different starting points.  That paper concluded that similar conditions in the Arctic will results in the same state, regardless of whether we are starting from high or low ice conditions.  Those pushing a hysteresis effect on Arctic sea ice claim that the sea ice will not return to previous extents, once exceeded.  That paper came to the conclusion that that is not the case.

It is a much better analysis than a simple cartoon with a ball and a few humps.

[interstitial]

Extent is more indicative of weather while volume is more indicative of climate. For a long time when the ice was thicker extent was an easier to measure proxy for volume. It is still easier to measure but as the thickness declines it makes a poorer proxy for volume. Now extent is mostly just an indicator of local weather conditions and not nearly as good of an indicator of climate.


Why do I say this? Given the insulative properties of ice approximately 1-1.5 meters of ice will form on arctic seas until the seas below become so warm they can loose heat all winter and still not freeze. Much thicker ice forms much slower.  Much thinner ice does not stay that way for long. Arctic air temperatures are cold enough in winter and will likely remain cold enough to do this for some time to come. Summer temperatures are warm enough to melt this ice completely in much of the arctic basically all the peripheral seas. Local weather determines how fast and when these peripheral regions melt but they mostly melt every year. This creates a very large extent signal due to geographical an orbital mechanics will remain relatively unchanged. Given how dramatically a little wind, sun or other weather can change thin ice extent it is difficult to tease climate changes out of the massive weather changes in the extent signal. Weather has a large impact on volume as well it is just smaller than its impact on extent. 

[binntho]

Off to work just now, so not much time for detailed answers, but I hope to be able to make some graphs during the day.

To begin with: Hysteresis is not a particularly good word to use in this context, and it has nothing to do wth hystery (hysteria, hysterical), as at least one poster above seemed to think.

Hysteresis, from greek "ὑστέρησις, shortcoming", "A property of a system such that an output value is not a strict function of the corresponding input, but also incorporates some lag, delay, or history dependence, and in particular when the response for a decrease in the input variable is different from the response for an increase."

Hystery from Latin hystericus, from Ancient Greek ὑστερικό “suffering in the uterus, hysterical”, from ὑστέρα  “womb”.

So let us go back to simple terms that we all understand. I will restate my position regarding Arctic Sea Ice, and hopefully provide some evidence during the day. By "history" I simply mean whether the state of ASI at one period in time can be used to predict the state in another period. Iif no: there is no discernable memory. If yes: there is some sort of memory in the system.

So my two claims:

1) There is no annual memory in the ASI system - the behaviour of 2023 cannot be predicted by anything that happened in 2022.

2) There is a clear multiannual memory, or decadal memory (although tying it down to decades may not be the best thing). Any long-term graph shows this. By relying on decadal memory, we can predict with a fair degree of certainty that 2023 minimum and maximum will fall within the average of the last 10 years, and this can be done for any year, again with a fair degree of certainty, although I am sure that someone can find outliers that break this rule!

NB the decadal memory does not have to be intrinsic to the ice. An example of an external memory is the steady increase in global temperatures, an example of an internal memeroy is the loss of multi-year-ice.

[binntho]

ISO certification meeting coming up (YAAY!!) but managed to knock up a graph or two.

Let me begin by stating that, of my two memory statements, the first one does not really need substantiating. There is general consensus that no statistically verified methods have been found to predict one year from the behaviour of the previous year.

My second contention, the decadal memory, seems to need substantiation. However, we have a serious problem here which is lack of data points. We only have 42 years of satellite observations, so using one value per year (maximum or minimum) is not realistic. We may glean some idea of the general trends, but making any long-term predictions on 42 data points is simply not realistic.

Daily data, however, and averages, can help us overcome this. I have downloaded daily Piomas data ending in November 2022, and added December based on linear growth between November 30 and December 31 2022, for which day we do have data courtesy of Stephen and Gero.

The graph shows running 365 day average, with first datapoint being January 1st 1980 and last datapoint December 31st 2022. The shape of this graph is familiar, and we have all discussed this several times, including the following points:

• The graph wobbles downward at the beginning (begining of 1980) and back up at (maximum at end of1987). This is the biggest wobble in the entire data series.
• Most of the graph lies comfortably, and remarkably steady, above the long-term trendline from mid 1987 to end of 2010
• The last decade has one big and one small downward wobble
• Since mid 2019 the line looks flat and even has a pert rise at the end

However much we may like to argue about the finer details of the chart, the general 40+ year trend is downward, with a linear trend of -0.1837 km3 per day -0.8137 km3 per day (-297 km3 per year).

[binntho]

Since we are looking at decadal trends, I decided to make separate 365 day running average graphs for 10 years at a time and look at the trendline for each of the 10 years. Of course, the starting and ending conditions are important, so I did two runs. The linear trendline for each period is shown below:

Period	Linear trend
1983-1992	-0.1025
1993-2002	-0.7863
2003-2012	-1.6757
2013-2022	-0.2507

Period	Linear trend
1980-1989	0.0063
1990-1999	-0.6668
2000-2009	-1.3503
2010-2019	-0.2987

There are differences between the two tables which are caused by differing starting points which was to be excpected, since our graph has wobbles at the beginning and at the end.

This applies particularly to the beginning - it makes a big difference whether one starts in 1980 or 1983. Nobody looking at the graph from my previous post would, however, claim that the first decade in our dataseries was "flat".

The last decade has shown a rate of decline that exceeds the long-term linear rate, so there is nothing here to indicate that this coming decade (whether we count from 2020 or 2022) will not show similar behaviour. that is lower than the long-term rate, but still significant.

On the basis of this, I declare my second contention to be fully valid - the long-term memory is there for all to see, and the general downward trend is remarkably reliable.

Your memory statement is inaccurate.  While the most recent decade experienced a lower maximum, there has not been a lower minimum.

The Walrus seems to be mixing things a bit here, but my statement about the maximums being lower and the mininums lower each decade certainly seems to hold for the 365 day averages (but the Walrus, if memory serves me correctly, insists on using the unreliable 42 datapoints which have no bearing on the problem).

Here is the same graph as before, with the decadal maximums (green lines) and minimums (red lines). It is certainly true that the minimum for the last 10 years is not very much smaller than the mininum of the previous 10 years, however the drop in maximums is very large.

[oren]

A great series of posts, binntho.
Insisting on only using the minimum of each year, looking only at extent and at NSIDC, misses a lot of other data supporting the downward trend.

[Freegrass]

I don't know if it means anything, but I'm seeing a similar pattern in the graph at the start and in the end. It'll probably take another decade or so to see of the graph continues on it's downward trend, or if it will flatten out...

[gerontocrat]

I look more at tipping points, with the Barents Sea as the illustration.

If summer melt is high and early, the increase in open water allows solar insolation to increase heating of the ocean.
When insolation ceases, the additional open water allows more ocean heat loss, encouraging freezing.

If the ocean heat loss exceeds the ocean heat gain, the system is self-correcting.

But if ocean heat gain is more than ocean heat loss a tipping point is reached, with less winter ice leading to earlier melt, yet more ocean heat gain, even later freezing and even less winter ice.

That is why I think the winter sea ice trend in the Barents is important. I imagine that this winter ends with a low winter ice volume despite the recent and late spike in sea ice area and extent and melt under ENSO neutral conditions can be a bit earlier and stronger. Then an El Nino gives a mid late summer spike in Arctic temperatures adding to ocean heat gain and delaying ocean heat loss in late summer to early winter. Then perhaps ocean heat gain will exceed ocean heat loss during winter.

The loss in sea ice becomes built into the system?

Is this hysteresis?

Elsewhere things are changing - see this paper https://www.nature.com/articles/s41467-022-34785-6 Rise and fall of sea ice production in the Arctic Ocean’s ice factories

The paper concludes that "we are currently passing the peak of ice production in the Kara and Laptev seas".

These changes are not yet showing up in the daily minimum and maximum extent data. Mind you, the lowest annual average sea Arctic ice extent happened in 2020; 2012 was 6th lowest despite the extreme record low minimum that year.
__________________________________
Note: "We focus on the Kara and Laptev seas-sometimes referred to as Arctic “ice factories” for their outsized role in ice production"

[binntho]

Gero, I agree with you in general - but remember that the heat loss in the Barents is, to a large extent, from Atlantic waters carrying heat up from the mid latitudes and even the tropics.

More open water early in the refreeze season does of course mean more heat lost from the ocean. But it also leads to more humidity, more clouds and more isolation, thus balancing the loss of insolation. This could lead to a warming of the entire Arctic.

And the reverse early in the melting season - too much open water may lead to extra cloudiness during max insolation.

And don't forget the extra waviness that comes with more open water, which may itself lead to increased storm activity and higher winds. Waves have a very bad effect on ice!

Just as a reminder that nothing is simple when it comes to Arctic Sea Ice!

[Sublime_Rime]

However much we may like to argue about the finer details of the chart, the general 40+ year trend is downward, with a linear trend of -0.1837 km3 per day (-297 km3 per year).

Am I going crazy, or does the slope in the related graph not say -0.8137. I just bring this up because it would have a large effect on how the average slope compares with the decadal slopes, and makes more sense to me, as the last decade seems lower in slope than the overall trend.