Is the melt season too short to produce a BOE?

[Paul]

Something that crosses my mind quite a bit as realistically the main basin melting season starts at the end of May and finishes in early September giving just 3 months to melt roughly 10 million square miles of ice to produce a BOE. So is it actually possible to melt that much ice in a reletively short time period  even in an ever warming world?

Or is it going to be something unexpected that will produce a BOE, for example true expansive open water along the CAA and Greenland leaving in effect an island of ice?

[Glen Koehler]

     That pretty well sums up the Slow Transition theory that there will continue to be enough winter refreeze to exceed the amount of melt possible during the May - September melt season.  It would be interesting to compare the volume of ASI lost during a typical modern melt season with the volume of ice contained in a thin covering of ice of the Arctic Ocean.  Of course, with each year of warming, the potential melt season loss grows.  And with Atlantification and Pacific water intrusion it gets more complicated.  I suppose that the global models account for all of those factors in projecting possible BOE dates.

[El Cid]

It's my theory that there will be no BOE until the Barents and Bering (and parts of Chukchi) are ice-free all around the year reliably. These seas need to become like the N.Atlantic and if/when that happens, the "attack" on the inner Arctic will start from a better position and will be possible. If you look at ice extent in March/April, there is almost no change at all in 30 years!!! Until this is so, a BOE is hardly possible (or you need a lot of random processes happening at the same time, eg extremely strong HP and insolation during May/June, then huge storms during July and August, very strong, continuous warm air advection into the Arctic during summer, etc)

[Jim Hunt]

Mind you, there is also all that stuff about there being enough heat not too far below the surface to melt all the ice several times over:

[HapHazard]

Yeah, melt from below will do it. Also I expect the basin to become more rubble-fied as time goes on, making it more mobile/easier to export towards warmer waters & vulnerable to storms.

[Richard Rathbone]

Mind you, there is also all that stuff about there being enough heat not too far below the surface to melt all the ice several times over:

That only gets to melt it once, and then next winter the ice is back and the heat is gone. It requires a mechanism that releases it in a catastrophic fashion, and at the right time of year, and it still just delivers one BoE. Even if the half the Arctic burps one year and the other half the next year, no BoE and the heat is gone. Its not renewable on an annual timescale.

To get a renewable BoE takes a mechanism that stops as much ice forming in the winter, and one that doesn't depend on a one-off melt. A few more decades of GHG BAU should do it, there's just not enough CO2 up there. Yet.

[Freegrass]

That only gets to melt it once, and then next winter the ice is back and the heat is gone. It requires a mechanism that releases it in a catastrophic fashion, and at the right time of year, and it still just delivers one BoE. Even if the half the Arctic burps one year and the other half the next year, no BoE and the heat is gone. Its not renewable on an annual timescale.

To get a renewable BoE takes a mechanism that stops as much ice forming in the winter, and one that doesn't depend on a one-off melt. A few more decades of GHG BAU should do it, there's just not enough CO2 up there. Yet.

When you lose stratification, and you're not making new ice anymore in winter, you don't have fresh water from the melting season anymore to restore that stratification. From then on there's only open ocean, with warm salt water that's releasing heat to the atmosphere in winter that's keeping the atmosphere too warm to make it freeze hard enough to create enough ice.

But I think that'll take many more years before that happens. We need a catastrophic August storm to mix the entire Arctic ocean for that to happen, and I don't see that happening any time soon yet.

So for the next 20 to 30 years or so, freezing season and melting season will be at equilibrium with each other, with only the weather to dictate minimums...

But that's just my humble opinion...

Edit: and what happens when the AMOC collapses in the mean time, and doesn't transport any warm water to the arctic anymore? Will the Barents sea start freezing over again if that happens?

Who knows? So keep reading the ASIF! 

[oren]

I think a BOE needs a combination of strong melting weather (early snowmelt, sun, warm air advection) and strong export. The export is the wildcard, much less heat is needed in the basin when a lot of ice has gone to the Barents and Greenland seas.
Due to the geography of the Arctic, export in mass can only happen in that direction, so the basic setup is a classic dipole with continental WAA.
Yes, the average melt season is too short to produce a BOE, but a crazy one could do it, in my opinion. It probably also needs that the winter volume is rather low, so back to back strong years should be part of the recipe.
As I've written elsewhere, early 2017 volume setup, with 2007 weather, could probably produce a BOE and almost certainly a strong new record.
Probability? Unknown. But I would hazard a guess of few percent per year currently, and growing with time and AGW. 5%? 10%?

[Freegrass]

I think a BOE needs a combination of strong melting weather (early snowmelt, sun, warm air advection) and strong export. The export is the wildcard, much less heat is needed in the basin when a lot of ice has gone to the Barents and Greenland seas.
Due to the geography of the Arctic, export in mass can only happen in that direction, so the basic setup is a classic dipole with continental WAA.
Yes, the average melt season is too short to produce a BOE, but a crazy one could do it, in my opinion. It probably also needs that the winter volume is rather low, so back to back strong years should be part of the recipe.
As I've written elsewhere, early 2017 volume setup, with 2007 weather, could probably produce a BOE and almost certainly a strong new record.
Probability? Unknown. But I would hazard a guess of few percent per year currently, and growing with time and AGW. 5%? 10%?

If we would have had a 2012 GAC in 2020, we could have come close to our first BOE that year. But then the 2021 and 2022 cold seasons wouldn't have given us a much different outcome IMHO...

[Richard Rathbone]

That only gets to melt it once, and then next winter the ice is back and the heat is gone. It requires a mechanism that releases it in a catastrophic fashion, and at the right time of year, and it still just delivers one BoE. Even if the half the Arctic burps one year and the other half the next year, no BoE and the heat is gone. Its not renewable on an annual timescale.

To get a renewable BoE takes a mechanism that stops as much ice forming in the winter, and one that doesn't depend on a one-off melt. A few more decades of GHG BAU should do it, there's just not enough CO2 up there. Yet.

When you lose stratification, and you're not making new ice anymore in winter, you don't have fresh water from the melting season anymore to restore that stratification. From then on there's only open ocean, with warm salt water that's releasing heat to the atmosphere in winter that's keeping the atmosphere too warm to make it freeze hard enough to create enough ice.

But I think that'll take many more years before that happens. We need a catastrophic August storm to mix the entire Arctic ocean for that to happen, and I don't see that happening any time soon yet.

So for the next 20 to 30 years or so, freezing season and melting season will be at equilibrium with each other, with only the weather to dictate minimums...

But that's just my humble opinion...

Edit: and what happens when the AMOC collapses in the mean time, and doesn't transport any warm water to the arctic anymore? Will the Barents sea start freezing over again if that happens?

Who knows? So keep reading the ASIF! 

When stratification goes, there is briefly warm water everywhere, and shortly after that there is cold water everywhere, and shortly after that there is ice everywhere. Ice is what keeps the heat in.

Take the ice away with a one off event, and it comes straight back again. A covering of ice is a superb insulator. The ocean is warm because it has ice on top of it in winter. Open water in winter loses more heat than open water gains in summer. Loss of stratification has negligible effect on ocean transport of heat into the arctic, and the impact of the loss of heat from open ocean to space dominates.

Recovery mechanisms of Arctic summer sea ice
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2010GL045698

[Paul]

I think a BOE needs a combination of strong melting weather (early snowmelt, sun, warm air advection) and strong export. The export is the wildcard, much less heat is needed in the basin when a lot of ice has gone to the Barents and Greenland seas.
Due to the geography of the Arctic, export in mass can only happen in that direction, so the basic setup is a classic dipole with continental WAA.
Yes, the average melt season is too short to produce a BOE, but a crazy one could do it, in my opinion. It probably also needs that the winter volume is rather low, so back to back strong years should be part of the recipe.
As I've written elsewhere, early 2017 volume setup, with 2007 weather, could probably produce a BOE and almost certainly a strong new record.
Probability? Unknown. But I would hazard a guess of few percent per year currently, and growing with time and AGW. 5%? 10%?

If we would have had a 2012 GAC in 2020, we could have come close to our first BOE that year. But then the 2021 and 2022 cold seasons wouldn't have given us a much different outcome IMHO...

You see I'm not sure that would be the case, 2020's ice pack was compact(but thin) whereas 2012's ice pack was alot more diffused and the storm hit more or less in the right spot to seperate the ice pack. I still wonder if the after affects did bring some heat up beneath the ocean as ice melt was still strong afterwards.

2007's and 2020's weather patterns would be interesting against 2017's low volume but I still don't think it would be enough for a BOE.

[kassy]

It is not too short according to modelling studies you just have to wait a while.

I do think a strong start with lots of export is a good start, the trick is to get early open CAB water and mix it during summer and then see how long it takes to refreeze. 

[Tom Stedman]

I recall 2020 did have a fairly sizable storm that crossed the Beaufort at the end of July.. which did leave time for most of the ice to melt there. Maybe a larger storm crossing the North Pole would have done more damage? As we are at the moment, we would need everything to go wrong to get a BOE. Temperatures rise just above zero for barely two months north of 80°. As of yet we've only got a substantial drop in extent in the CAB a small handful of times.

[nadir]

No, it is not. At least not according to the models, not even the least pessimistic projections. It is a matter of how and when what is not clear. But that it will eventually happen is just physics, given our inability to react faster against climate change.

[Paul]

No, it is not. At least not according to the models, not even the least pessimistic projections. It is a matter of how and when what is not clear. But that it will eventually happen is just physics, given our inability to react faster against climate change.

But that's the thing, the models are just a prediction, it's not a fact until it happens. Factors like deep waters in the CAB, lack of warming in most of the CAB(as there is always ice there) and the fact the last ice to melt is likely to be multi year ice which does not always melt at lower latitudes and closer to landmasses could mean a BOE may not happen.

Of course regardless whether it does or not, that does not mean the predictions of the consequences of climate change can't and won't happen.

[wallen]

The last 2 years have produced La Ninas and a 3rd one is in the current predictions. Historically these tend to occur every 20-25 years. I think a return to the El Nino pattern will be required to see extent minimums drop below 4million sq kms and that a BOE will amongst many other factors will require 2-3 consecutive El Nino seasons.

[The Walrus]

The last 2 years have produced La Ninas and a 3rd one is in the current predictions. Historically these tend to occur every 20-25 years. I think a return to the El Nino pattern will be required to see extent minimums drop below 4million sq kms and that a BOE will amongst many other factors will require 2-3 consecutive El Nino seasons.

The last time we experienced an extended La Niña was 2010-13.  We all know what happened then.

https://ggweather.com/enso/oni.htm

[kassy]

Factors like deep waters in the CAB, lack of warming in most of the CAB(as there is always ice there)

The deep waters are not that important (deep part isn´t frozen anyway). Getting rid of the ice cover matters which is why early opening is important which could be caused by strong melt and export start on the Atlantic side. Did not happen yet but it could happen.

When modelling the future you are looking at things that have not happened but which are likely to happen. They will be facts some day (if the models are anywhere near correct). This does not mean they are perfect. When they say 2050 i already correct that to 2040 because everything shows up quicker then we model before.

Time shall tell.

[binntho]

Last year we had a heated (!) discussion on bottom melt - to recap, some posters hotly claimed that the central Arctic only ever experienced melt from above (insolation) with no or extremely insignificant bottom melt.

Other more (or less?) temperate posters pointed to the massive melt potential of the relatively warm deep ocean layers - and that perhaps it was only a question of time until we would start to see polynia opening up in the middle of the ice pack, caused by turbulence bringing these warm waters to the surface.

In other words, exactly what seems to have happened this year - the curiously resistent pole hole, the 10.000 km2 or so of extremely low extent close to the pole and inside the ice pack itself, that seemed to persist for a couple of months in more or less the same place in spite of the pack itself shifting back and forth.

Is this a harbinger of things to come, or a one-off fluke? Was the pole hole caused by warm waters brought to the surface by turbulence, or was it just a fluke caused by a series of lows settling over the same area, one after another?

If this was indeed caused by bottom melt brought on by turbulence of some sort bringing deep waters to the surface, then something very new has entered the Arctic, something which may well force a paradigm shift in our understanding of the Arctic and the future changes of BOE.

[nadir]

It was not a fluke, it was a month-long moderate storm dispersing the ice toward the periphery of the pack. This has happened before (2013).
 
After the storm in June/July, there have been others affecting the same region since this pattern has been predominant this year.

I don’t think bottom melt had anything to do with this year’s event. I am not claiming that bottom melt is zero across the CAB or even above 80N or at the Pole. In July 2020 temperatures were persistently above zero at the Pole so much so that I am confident there was great thinning from the bottom as well as from infinity of melt ponds. The pack was thin and deteriorated at the melt-pond scale (remember the vessel that reached the Pole that year and crew found very difficult to even lay foot over the ice). But the pack didn’t show big gaps visible from space because it was being compacted by the anticyclone.

Is there any direct oceanic heat influence at and near around the Pole? I don’t know, can only speak of the atmospheric influence which is apparent.

[binntho]

Nadir, you make a point that others have made before you, but did not appear to convince everybody. Whether we actually saw the same phenomenon in 2013 doesn't exclude it being caused at least partially by bottom melt.

Part of the discussion, which I did not mention above, was the possibility that hypothetical oceanic heat influxes due to oceanic turbulence have been there the whole time, but with increased temperatures and thinner ice, these phenomena may suddenly become visible as polynias. Low pressure areas hovering over the same spot could be an added factor.

Is there any direct oceanic heat influence at and near around the Pole? I don’t know, can only speak of the atmospheric influence which is apparent.

Uniqorn is the specialist here, but i seem to remember him showing how the ice-free area is coincident with bathymetric features, indicating the possibility of turbulence causing heat influx. As opposed to atmospheric turbulence which is readily visible from above, oceanic turbulence is opaque and requires direct measurement which is somewhat sparse.

[be cause]

can you show one sign of melt in the open hole all summer .. I looked daily and saw none and am largely in agreement with nadir that the obvious should not be discounted .

[nadir]

can you show one sign of melt in the open hole all summer .. I looked daily and saw none and am largely in agreement with nadir that the obvious should not be discounted .

I don’t say it has to be discounted. I just say we can’t observe it like we observe the weather and its effects. If NOAA deployed an array of oceanic observations in the Arctic such as that in the Equatorial Pacific (for El Niño/La Niña predictions) then we would be having a very different conversation.

[Freegrass]

can you show one sign of melt in the open hole all summer .. I looked daily and saw none and am largely in agreement with nadir that the obvious should not be discounted .

I'm pretty sure it's a combination of all of the above. Storms disperse the ice. This dispersion is movement of the ice, which causes bottom melt and movement in the water column. Open water then soaks up heat from the sun, which melts more ice. And as the hole grows, it becomes more vulnerable to wind and waves that stir up the water column, which causes even more ice to melt. Etc, etc, etc...

[binntho]

can you show one sign of melt in the open hole all summer .. I looked daily and saw none and am largely in agreement with nadir that the obvious should not be discounted .

I don’t say it has to be discounted. I just say we can’t observe it like we observe the weather and its effects. If NOAA deployed an array of oceanic observations in the Arctic such as that in the Equatorial Pacific (for El Niño/La Niña predictions) then we would be having a very different conversation.

Absolutely. Any putative bottom melt caused by turbulence-induced influx of deep oceanic heat is purely speculative. But perhaps worth looking into?

[nadir]

I was thinking out loud over the freezing season thread that we are somehow “lucky” that the Arctic during Fall releases most or all the excess heat from Arctic Amplification, and most or all of this heat ends up being radiated out to space or buried sufficiently deep into the ocean. Let’s say that the Arctic system is a well-behaving transmission boundary, like a room with an open window instead of closed concrete walls.

It seems apparent to me that, shouldn’t this heat be lost or buried but rather somehow stay near the ice and be able to reduce ice thickening during Fall/Winter and enhance melting the following summers, well, we would have had a BOE by now for sure, and also much higher global temperatures. The amount of excess heat is overwhelming, but luckily this heat goes where it can’t harm.

So at the end, a BOE in a very near future is more plausible if the Arctic Ocean enabled somehow more of this excess heat to stay around. How this harder boundary condition would work I have no idea, but I’m sure folks around have read about this and there are theories about this.

[Freegrass]

I keep thinking about Fram export as a tube of toothpaste that releases the pressure of overfilling the tube from the back... Ice thickens to about 2 meters, and then slows down significantly. So there 's some sort of limit to how thick the ice can get. Beyond that it's the wind that either stacks the ice, or squeezes it out of Fram...

And yes, the more open ocean we have, the more heat possibly gets released... A storm like the one that's predicted right now sure will release a lot of heat again...

Land heats up faster than water, so the further the ice edge gets away from land, the less impact the ice will experience from arctic amplification...

We had the rapid heating from land that melted the shore ice, and now we are waiting for the water to heat up more to melt the rest. But that'll take a lot longer...

[Paul]

We had the rapid heating from land that melted the shore ice, and now we are waiting for the water to heat up more to melt the rest. But that'll take a lot longer...

And yet despite the snow cover being the lowest on record over Eurasia during Spring, it did not result in rapid Siberian ice melt so ice thickness can counteract that it would seem.

I just think a BOE is almost impossible whilst we got multi year ice and we will always have at least some multi year ice even if the numbers are slowly going down. All that said this is the Arctic so expect the unexpected!

[binntho]

The main thing to remember about the Arctic (besides it being bl***y cold and big) is that it is almost entirely landlocked. Dry land is very bad ad absorbing insolation, and the deep continentals of central Asia and N-America causes the northern half of the Temperate zone to become much colder than a similar stretch of ocean, and more or less covered in snow for much of the yar - while oceans in the northern temperate zone remain ice free all year round.

The Arctic Sea Ice is in effect protected by the surrounding land masses, and it is very possible that the speed of reduction in ASI is linked to a factor calculated by the following formula:

(Open water area * days per year) / (ice cover area * days per year)

This factor is still very low but growing slowly. My guess is that there will be a threshold where this factor starts to show exponential growth from one year to another, and quite possibly exceeding 1 at the time of BOE.

[kassy]

I was thinking out loud over the freezing season thread that we are somehow “lucky” that the Arctic during Fall releases most or all the excess heat from Arctic Amplification, and most or all of this heat ends up being radiated out to space or buried sufficiently deep into the ocean.

It is probably more a case of observer bias then luck. Lets slip details like does it really balance out?
Of course there is always extra heat coming to the arctic which is not related to AA simply because it originates somewhere else so that must go into the model too.

If we really simplify things then yes it still freezes over and more open water does mean more heat loss locally but it does not balance out over the long run.

The Arctic Sea Ice is in effect protected by the surrounding land masses, and it is very possible that the speed of reduction in ASI is linked to a factor calculated by the following formula:

(Open water area * days per year) / (ice cover area * days per year)

I always liked the poll where people had predictions for the minimum based on different calculations from early data. One of the winners featured was a simple model running on continental snow cover.

Many things drive the changes in ice cover and what happens when and how fast is not covered in that factor or it is all lumped together. It works for the last time the pond froze too.

[FredBear]

A BOE is literally a change of state - "It has melted", we have definitely done it!
It would be a marker, a warning, etc.

My question is now rather "Has this been superseded by changes in lower latitudes?"
Recently we have seen more significant changes in local temperatures, rainfall, storms than have been expected at this stage of anticipated global warming.
The "canary in the coal mine" is too late - the gases (literally) are out there whether they make a BOE or not - what are we going to do??

[kassy]

That goes beyond the threads question.

In general we do not have a really good handle on the rate things will progress the next few decades. I have not seen that much research delving into that. Even in the fifties it was predicted that if you go over certain limits things would get wild. Recently we got much more computing power but as far as i know we really have not looked into that much while growing CO2 emissions at a staggering rate.

So it is not so much superseded as details showing up we did not bother with much because most science is aimed at the longer time frame.

This debate could go into the Which pathway are we on thread in AGWIG/Science. As to what are we going to do i imagine watch in horror because we know what we have to do and we are not working hard on that.

[Glen Koehler]

RE Is the melt season long enough to produce a BOE?
    1) Each year's melt season starts with ice that froze in previous winter + residual ice that was already present before the winter refreeze, i.e. MYI.

    2) During the satellite era since 1978 there has been a strong trend for decline in September minimum volume (with a 75% decline), and about a 50% decline in Extent - the metric used to define a BOE.

    3) That trend is only possible if, on average, the melt seasons have been removing the amount of ice created in previous melt season and have also been removing ice from the ASI MYI bank account.

    4) So it must be the case that on average the melt seasons have removed more ice that was created during the previous winter's refreeze.

    5) Unless there is some negative feedback loop that overcompensates for the forces causing the long-term decline trend in April max ice, the amount of ice at the beginning of a future melt season will approach the amount which is removed by a melt season.

    6) With continued global warming augmented by Arctic amplification, the ability of melt seasons to remove ice will increase.   The strongest warming occurs during Arctic winter, and therefore, the winter refreezes will create smaller and smaller amounts of new FYI.

    So that all points to "Yes" as the answer to whether the melt season is long enough to produce a BOE. 

     The question of when is not clear even to the experts and the models.  Previous model projections have underestimated the rate of decline.  In a pair of 2018 journal articles, Notz & Stroeve / Stroeve & Notz provided two extrapolation benchmarks for when ASI could reach BOE (or was it zero ice in Sept?).  One of those benchmarks was the total cumulative  CO2 emissions.  The other was a global average temperature of 1.68C above the preindustrial average (usually approximated by the 1850-1900 average global average surface temperature). 

     Current projections have the global temperature anomaly trend reaching +1.7C in another 12 to 28 years (depending on future emissions trajectory, still unresolved climate sensitivity, and the activation of known and unknown feedback mechanisms).

[El Cid]

This is all fine, but somehow we should address the question as to why neither winter nor summer ice volumes have changed since cca 2010. March volume has been around 22500 km3 and winter around 4500 with amazing stability. That is why the questions arise.

Why is there no more summer melting of ice now than 10+ yrs before, despite global temperatures significantly higher?

Why is winter ice extent still almost identical to the extent of the 80s and volume similar to 10+ yrs ago?   

[gerontocrat]

Why is winter ice extent still almost identical to the extent of the 80s and volume similar to 10+ yrs ago?

looking elsewhere...

The year with the least average sea ice extent was 2020, not 2012.
For PIOMAS the lowest yearly average volume was in 2017, not 2012.

Two La Nina years seems to be the obvious reason for increases in that average in 2021 and 2022. And the2021/2022 saw a multitude of extreme weather events in the rest of the globe.

Are we seeing a far more reactive unstable atmosphere responding to changes in the ENSO cycle?

click images to enlarge

[El Cid]

Let me attach 3 charts. March piomas volume, September piomas voulme and average annual piomas voulme. I see no trend since 2010

(btw, reflecting to the above : there is no discernible scientific connection between ENSO and Arctic Ice extent as fas as I know)

[El Cid]

One more chart: Spring ice extent is almost identical to 30 yrs ago!

I believe it is almost impossible to create a BOE ("the melting season is too short") until the Barents and Chukchi stay reliably open all spring. We probably need more warm water transport for that to happen. Once that happens a BOE will be much more easily achieved

[oren]

El Cid, I disagree with some of what you wrote. Winter extent may be "almost identical" to the 1980s but is far from "identical". And your completely flat since 2010 trend requires some not so good 3-line division. I believe winter volume is still on a slow downward trend, though very far from previous trend rate.

A few additional charts of interest, all from https://www.epa.gov/climate-indicators/climate-change-indicators-arctic-sea-ice.

[nadir]

We can quibble on the details but El Cid is essentially correct.

Powerful greenhouse effect and ocean changes yet unknown are required to arrest the heat losses during the long Arctic night. Right now the Arctic night is a heat sink that cancels Arctic Amplification and resets the ice in Spring. Of course there is the loss of MYI but Oren’s MYI graph also shows a hiatus in MYI loss. Earlier arrival of Spring is a consequence of the very gradual increase of global atmospheric and ocean temperatures, which reduce the reach of the ice pack edge and snow cover, and accelerates the warming up of the NH ocean and continents, but not from Arctic amplification from the previous year. Otherwise we would be observing a much faster Arctic heating.

[The Walrus]

I will agree and disagree with El Cid.  I disagree that winter ice extent is almost identical to 30 years ago.  In 1992, the maximum sea ice extent (NSIDS) was 15.56 M km2, and the average for the 5-years ending in 1992 was 15.86.  The maximum in 2022 was 14.875 M km2, with a 5-year average of 14.79.  While the decline has been a mere 5% compare to the roughly 33% loss at minimum, there has been a steady [albeit small] decrease.

I agree with his analysis since 2010.  The trend has been flat, and it shows in the volume graphs presented and oren's extent plot for first through fifth year ice.

[Glen Koehler]

     I think the truth is in the middle, while not exactly flat since 2010, the rate of Volume and Extent declines have been less than in 2000-2010.  The experts point to internal dynamics of the Arctic system that outweigh the melting conditions during any individual year, or even a decade or more.  I don't understand enough about those dynamics to give details.  Maybe an ASI expert watching the forum will jump in to do so.  The point is that even with a strong long-term trend, there can be extended periods without an obvious decline in the metrics.

    The recent "hiatus" in ASI decline has a parallel to the mythical 1998 to 2013 global warming hiatus.  That spurious event generated all kinds of debate and skepticism and even serious scientific papers.  And of course, it was also manipulated as a political tool by the climate denial industry.  Alas then came 2014, then 2015, then 2016, 2017, 2018, 2019, 2020 until the present, which catapulted us into a new temperature regime from which I fear humanity shall never recover, certainly not in my lifetime, and probably not in my children's lifetimes (unless we get real serious about CO2 removal). 

     The seven warmest years since humans began scientific measurements have been since 2015.  That will soon be the "8 warmest years have all been in the 8 years since 2015." https://public.wmo.int/en/media/press-release/2021-one-of-seven-warmest-years-record-wmo-consolidated-data-shows#:~:text=The%20warmest%20seven%20years%20have,pronounced%20compared%20to%20recent%20years. 

     Instead of saying 2021 was among the warmest years ever, it is just as accurate to use the opposite framing.  The current temperature regime, with new heat wave records vastly outnumbering new low temperature records, is cooler than what we will encounter for the next 50 years or more.  It only gets hotter from here on.  (Plus already statistically validated increases in extreme precipitation, sea level, etc.) 

      As for the current ASI decline hiatus, remember what the great Forrest Gump said: "It happens."  Look at Gero's average daily ASI volume or El Cid's average annual ASI volume graphs for 1981 - 1994.  I'm sure climate change skeptics in April 1995 were using the (at the time) flatline ASI volulme graph to say "Where's your global warming?" 

      Ditto look at El Cid's 1981 - 1997 September or 1982 - 1997 March ASI volume graphs (15-16 year hiatuses!).

     Ditto - look at Oren's September Extent graph for 1980 - 1997.  Or Oren's graph showing the 5+ MYI value for 1993 - 2003. 

      Flatline periods occur.  Tamino used statistical testing debunk false impressions of a global temperature hiatus, and also addressed the post-2012 ASI decline hiatus at an earlier stage (~ 2016).  Now that the "hiatus" has more years under its belt it looks even more visually convincing.  But you need a statistician to separate signal from visual noise and to counteract the human tendency to create patterns.

      Getting back to the global temperature analogy, this staircase chart ends in 2016, so does not even include the "within top 7 warmest years" of 2017-2021, but it demonstrates that nature sometimes requires a bit of patience to see trends.



     And this animated gif shows how starting with the big El Nino year of 1998 gave rise to a false hiatus impression.

  Source: Wikipedia https://en.wikipedia.org/wiki/Global_warming_hiatus

     The ASI is dying.  And we are causing it even though even apart from simple survival there are many other positive benefits and reasons to stop burning fossil fuels (e.g. bye bye Putin).  Despite the recent slowdown in decline, there is every reason to believe that there will be a melting season strong enough to cause a BOE within the next "X" years (I don't know what number X stands for, but my guess is that it is 15-25). 

     But the process does not necessarily increment smoothly.  My guess is that while the standard metrics appear stalled, there are qualitative and other changes to the Arctic system and the ASI that we do not measure that continue to erode.  Eventually, that weakened foundation will become apparent in the Volume, Area, Thickness, and Extent metrics that we monitor.  Termites can chew on a house foundation for years unnoticed, until one day the house collapses.

[nadir]

I don’t think it’s the same. From a subjective point of view, I never accepted the proposition that global temperatures had stalled in the 2005-2015 period, particularly because the Arctic kept showing the greatest increase of temperatures everywhere in the world, no hiatus, no anything. Yet, changes for the ice pack seem to have reached gradually a very slow decline and I am trying personally to find what explains that, after the 2007-2012 acceleration that had us all thinking it was a matter of a few seasons to reach a BOE.

[binntho]

Good post Glen!

And I agree with what El Cid says here:

I believe it is almost impossible to create a BOE ("the melting season is too short") until the Barents and Chukchi stay reliably open all spring. We probably need more warm water transport for that to happen. Once that happens a BOE will be much more easily achieved

Again, this is about land vs. ocean. The Arctic is protected by continental landmasses that:

• keep oceanic heat away - and 95% or so of global insolation and reflected radiation is absorbed by the oceans.
• extend the arctic winter far south into the upper temparate latitudes
• provide a platform for snow accumulation

All of the above work together to keep the Arctic as it is, and even if global warming might reduce snow cover, the other factors are immune to any greenhouse effects.

A BOE will not happen until the ice retreats sufficiently early from the continental landmasses to allow open-water insolation, wind-driven Ekman pumping and wave action to batter the ice for several months.

I have earlier proposed a simple factor that we should be keeping an eye on, calculated annually as the ratio of openwater-area-days vs. icecovered-area-days, within the Arctic basin itself, i.e. the ocean enclosed by the continental landmasses and the island chain from Svalbard to Severnaya Zemlya.

This ratio is probably now in the low second decimals, and I expect that an BOE is bound to happen before this ratio reaches 1, but whether 0.5 would be enough?

[Freegrass]

Good post Glen!

And I agree with what El Cid says here:

I believe it is almost impossible to create a BOE ("the melting season is too short") until the Barents and Chukchi stay reliably open all spring. We probably need more warm water transport for that to happen. Once that happens a BOE will be much more easily achieved

Again, this is about land vs. ocean. The Arctic is protected by continental landmasses that:

• keep oceanic heat away - and 95% or so of global insolation and reflected radiation is absorbed by the oceans.
• extend the arctic winter far south into the upper temparate latitudes
• provide a platform for snow accumulation

All of the above work together to keep the Arctic as it is, and even if global warming might reduce snow cover, the other factors are immune to any greenhouse effects.

A BOE will not happen until the ice retreats sufficiently early from the continental landmasses to allow open-water insolation, wind-driven Ekman pumping and wave action to batter the ice for several months.

I have earlier proposed a simple factor that we should be keeping an eye on, calculated annually as the ratio of openwater-area-days vs. icecovered-area-days, within the Arctic basin itself, i.e. the ocean enclosed by the continental landmasses and the island chain from Svalbard to Severnaya Zemlya.

This ratio is probably now in the low second decimals, and I expect that an BOE is bound to happen before this ratio reaches 1, but whether 0.5 would be enough?

If I had to go to school again, I would want you to be my teacher...
I've learned so much from you already... Sometimes you just confirm and then finetune my assumptions... And then I learn so much more...

THANK YOU!

PS; To Glenn.
Yes, I'm kicking myself everyday for not replying yet...
Have patience my friend!
Shit happens...

[El Cid]

Glen,

I think noone on this site doubts that we are heading towards a BOE and the trend is intact.

However, I think that an interesting question is whether we have reached a new state ("the slow transition") where due to various factors (bathymetry, currents, stratification, you name it) the rate of decline has significantly slowed. It is not obvious whether this state will last another 30 years or will be over next year. If we can get closer to the truth of this matter then we will be able to answer the question:  "Is the melt season too short to produce a BOE? "

btw, even during the "hiatus" (1998-2013), despite not having a major El Nino, global temperatures hit a new high in 2002, then 2005, then 2010, so the uptrend remained evindent. Not so with ASI

[oren]

I think we can all agree Chris Reynolds was right and we are in a Slow Transition regime. Also that the rate of decline has significantly slowed (but is not zero, IMO).
ASI extent/volume/area display a high variability from year to year. 2012 was very strongly below trend, which led to "no min records" since then. However, We've had many volume, area and extent daily records, though not in September, and we've had other Sep contenders (2016, 2020) that IMO showed 2012 was not a one time thing. So I fully expect variability to strike again, and deeper.

I have these two charts I made at the end of 2020, which I lack the time to update. I don't think the results are changed since then, but in any case I think the data is interesting.

[Paul]

Yep we should not be forgetting that despite no record lows during September, we have seen record lows at various times in most years in the past decade, even last year.

I do believe the record will be broken at some point but I still feel whilst we got the multi year ice, a BOE will be very difficult to achieve.

[Freegrass]

Correct me if I'm wrong, but the winter of 2021-22 saw a record breaking export of ice through the Fram. That once in a lifetime expedition - to get frozen into the ice during winter ( I forgot the name) - couldn't have picked a worse year...

And after that winter with record breaking Fram export, and early open water in the ESS and Laptev, and then a record breaking HPS that melted a shitload of ice, we weren't even close to breaking the 2012 record...

We needed an August storm to break the 2012 minimum.


2012 still had lots of MYI...
And still it broke all records...
Just because of one storm...
Not because of the weather!
If it was the weather, we would have broken the record in 2020...
2020 was the perfect season for a new minimum, but we didn't make it, because we didn't have a GAC...

So without a GAC in August, we're not gonna break any records any time soon...

[oren]

I disagree. 2012 had lots going for it before/besides the GAC.
And 2020 had weather in Aug that was favorable for the ice. It could have been otherwise even without a GAC.
Note BTW that 2016 also had a GAC, so they are not that rare.

[Freegrass]

And 2020 had weather in Aug that was favorable for the ice.

True... After a remarkable 2020 preseason, in August it all just suddenly came to a halt... That was weird, and made me wonder how much bottom melt was worth inside the deep basin... That compacted ice pack just stopped melting...