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rboyd

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The Fast Transition
« on: April 27, 2017, 09:04:47 PM »
Will a "Blue Ocean" event in September trigger positive feedbacks that will rapidly (e.g. a decade or so) lead to a seasonally ice free Arctic with blue ocean being the predominant state throughout the summer months?
These feedbacks would include:
- Albedo Effects (possibly mitigated by cloud effects)
- Reduced separation between the Arctic and Northern Hemisphere climate regions, allowing for greater amounts of heat transfer into the Arctic
- Greater level of storms and waves driven by open ocean (and heat contrast between ocean and land)
- Mixing of the water column in the absence of a thick ice cover, bringing up deeper, warmer water to the surface

With the extra heat taken into the open waters during Spring/Summer being vented into the atmosphere in the Fall/Winter months, will the freezing season be significantly reduced (i.e. less and less FDD's) - reducing the ability of the ice to reform and thicken?

Could the Arctic then transition to near ice free year round as the increased energy taken in through the spring/summer, together with greater heat transport from the south, reduces the FDD's further and further?
- Thinner ice at the start of the melt season leads to greater warming from reduced albedo, leads to less FDD's, leads to yet thinner ice the next melt season.

rboyd

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Re: The Fast Transition
« Reply #1 on: April 27, 2017, 09:06:08 PM »
The Sensitivity of the Arctic Ocean Sea Ice Thickness and Its Dependence on the Surface Albedo Parameterization

ABSTRACT

In this study, the response of sea ice thickness to changes in the external forcing is investigated and particularly how this response depends on the surface albedo formulation by means of a one-dimensional coupled ocean–ice–atmosphere model. The main focus is on the thickness response to the atmospheric heat advection Fwall, solar radiation FSW, and amount of snow precipitation Sprec. Different albedo parameterization schemes [ECHAM5, CSIRO, and Community Climate System Model, version 3 (CCSM3)] representing albedos commonly used in global climate models are compared together with more simplified schemes. Using different albedo schemes with the same external forcing produces large differences in ice thickness. The ice thickness response is similar for all realistic albedo schemes with a nearly linear decrease with increasing Fwall in the perennial ice regime and with a steplike transition into seasonal ice when Fwall exceeds a certain threshold. This transition occurs at an annual-mean ice thickness of 1.7–2.0 m. Latitudinal differences in solar insolation generally leads to increasing ice thickness toward the North Pole. The snow response varies significantly depending on which albedo scheme is used. The ECHAM5 scheme yields thinner ice with Sprec, the CSIRO scheme gives ice thickness nearly independent of Sprec, and with the CCSM3 scheme the ice thickness decreases with Sprec. A general result is that the modeled ice cover is rather sensitive to positive perturbations of the external heat supply when it is close to the transition such that just a small increase of, for example, Fwall can force the ice cover into the seasonal regime.

http://journals.ametsoc.org/doi/pdf/10.1175/JCLI-D-12-00085.1

If I understand correctly, this is saying that there is an ice-thickness / forcing threshold beyond which a move to seasonal sea ice occurs in a step-wise fashion - due to the albedo feedback mechanism. 

As the temperature differential between the Arctic and the rest of the Northern Hemisphere reduces, it becomes easier for warm air masses to enter the Arctic from the south (the Jet Stream weakens and becomes wavier). So the value of Fwall may increase, and the ice will have to be thicker to survive the melt season.

This of course does not take into account any mechanical changes in the ice as it thins, nor the possible mixing of the water column where there are areas of open water/thin ice.

Jim Williams

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Re: The Fast Transition
« Reply #2 on: April 27, 2017, 11:26:14 PM »
Will a "Blue Ocean" event in September trigger positive feedbacks that will rapidly (e.g. a decade or so) lead to a seasonally ice free Arctic with blue ocean being the predominant state throughout the summer months?
These feedbacks would include:
- Albedo Effects (possibly mitigated by cloud effects)
- Reduced separation between the Arctic and Northern Hemisphere climate regions, allowing for greater amounts of heat transfer into the Arctic
- Greater level of storms and waves driven by open ocean (and heat contrast between ocean and land)
- Mixing of the water column in the absence of a thick ice cover, bringing up deeper, warmer water to the surface

With the extra heat taken into the open waters during Spring/Summer being vented into the atmosphere in the Fall/Winter months, will the freezing season be significantly reduced (i.e. less and less FDD's) - reducing the ability of the ice to reform and thicken?

Could the Arctic then transition to near ice free year round as the increased energy taken in through the spring/summer, together with greater heat transport from the south, reduces the FDD's further and further?
- Thinner ice at the start of the melt season leads to greater warming from reduced albedo, leads to less FDD's, leads to yet thinner ice the next melt season.

I can only respond that the ice cores tell us there are sudden and complete changes in the climatic regime.  These seem to be in years or less, not centuries.

I will go with the ice cores rather than the models.

slow wing

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Re: The Fast Transition
« Reply #3 on: April 28, 2017, 12:16:52 AM »
Jim, that's interesting and scary. Can you give a reference and/or more information on that?

Archimid

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Re: The Fast Transition
« Reply #4 on: April 28, 2017, 12:30:38 AM »
rboyd, thanks for starting this thread. I'm still re-reading and digesting what I understand from the paper but here is an interesting quote from the paper:

Quote
This study shows that, regardless of which albedo parameterization is being employed (except the constant one), the transition into seasonal ice, due to the surface albedo feedback, is abrupt and occurs at a critical mean ice thickness hice of around 1.7–2.0 m

Attached is tealight's FDD's calculations which register the theoretical thickness according to temperatures north of 80 as 1.6 M. PIOMAS has a similar numbers. http://psc.apl.uw.edu/wordpress/wp-content/uploads/schweiger/ice_volume/Bpiomas_plot_daily_heff.2sst.png

As we stand we already are below the threshold given by these models for transition from perennial to seasonal ice.
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dosibl

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Re: The Fast Transition
« Reply #5 on: April 28, 2017, 12:45:11 AM »
I've also seen some stalling of thickness in my HYCOM graphs, however that data is a little rough so I'm looking for the next PIOMAS numbers to hopefully shed some light.

rboyd

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Re: The Fast Transition
« Reply #6 on: April 28, 2017, 02:32:18 AM »
One of the biggest drivers of a rapidly receding ice pack may be the seasonal transfer of the Sun's energy from Spring/Summer to Fall/Winter, through the release of heat into the atmosphere from open water during Fall and Winter. The effect seen in 2016, when a high heat intake from early Spring lead to delayed refreeze and loss of FDD's.

This reduces the ice volume at the beginning of the melt season, which then reduces the time for transformation to open water and increases the time available for the Sun's energy to be taken up by the water. More heat is then transferred into the freezing season, and the next year there is even less ice. In the short-term of course, cloudy weather early in the season can negate this effect.

Abstract

Observed and projected climate warming is strongest in the Arctic regions, peaking in autumn/winter. Attempts to explain this feature have focused primarily on identifying the associated climate feedbacks, particularly the ice-albedo and lapse-rate feedbacks. Here we use a state-of-the-art global climate model in idealized seasonal forcing simulations to show that Arctic warming (especially in winter) and sea ice decline are particularly sensitive to radiative forcing in spring, during which the energy is effectively ‘absorbed’ by the ocean (through sea ice melt and ocean warming, amplified by the ice-albedo feedback) and consequently released to the lower atmosphere in autumn and winter, mainly along the sea ice periphery. In contrast, winter radiative forcing causes a more uniform response centered over the Arctic Ocean. This finding suggests that intermodel differences in simulated Arctic (winter) warming can to a considerable degree be attributed to model uncertainties in Arctic radiative fluxes, which peak in summer.

2016 was the perfect case of this, where the albedo was highest in the Spring with the added energy being carried into the Fall season. We are running a bit behind of 2016 so far according to Nico Sun (details of his methodology on the Albedo Warming Potential Topic).

https://sites.google.com/site/cryospherecomputing/warming-potential/graphs

nick

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Re: The Fast Transition
« Reply #7 on: April 28, 2017, 12:24:06 PM »
Will a "Blue Ocean" event in September trigger positive feedbacks that will rapidly (e.g. a decade or so) lead to a seasonally ice free Arctic with blue ocean being the predominant state throughout the summer months?
These feedbacks would include:
- Albedo Effects (possibly mitigated by cloud effects)
- Reduced separation between the Arctic and Northern Hemisphere climate regions, allowing for greater amounts of heat transfer into the Arctic
- Greater level of storms and waves driven by open ocean (and heat contrast between ocean and land)
- Mixing of the water column in the absence of a thick ice cover, bringing up deeper, warmer water to the surface

With the extra heat taken into the open waters during Spring/Summer being vented into the atmosphere in the Fall/Winter months, will the freezing season be significantly reduced (i.e. less and less FDD's) - reducing the ability of the ice to reform and thicken?

Could the Arctic then transition to near ice free year round as the increased energy taken in through the spring/summer, together with greater heat transport from the south, reduces the FDD's further and further?
- Thinner ice at the start of the melt season leads to greater warming from reduced albedo, leads to less FDD's, leads to yet thinner ice the next melt season.

There is a negative feedback mechanism that will likely prevent any runaway scenario in that more open ocean leads to more moisture in the air which leads to more snow cover on the surrounding continents. More snow covers leads to later/colder spring air temps (through increased albedo over land) and thus to a greater chance of more ice surviving into the following year.

I can only respond that the ice cores tell us there are sudden and complete changes in the climatic regime.  These seem to be in years or less, not centuries.

I suspect you're referring to events like the Younger Dryas and the various Bond events? The consensus is that these are all caused by freshwater pulses in the north atlantic (indeed they're not global phenomena) caused by large lake releases. In theory this could be replicated by rapid total ice melt, but Lake Agassiz was around 22,000 km3 in volume which is ~4 times the current summer minimum ice volume so it's hard to see it having the same sort of effect. Indeed, the seasonal arctic ice volume variation is around 20,000 km3 and, coincidentally, the annual loss from the Greenland ice cap is about the same again, which suggests that the ocean is absorbing 40k km3 of fresh water annually anyway (plus whatever drains from siberia). So you would likely have to have a marked increase in Greenland melting to trigger climate changing amounts of freshwater release.

I've never worked it completely through before but those figures do kind of suggest that even should all the summer ice melt out there wouldn't be a dramatic effect on the global climate (at least not from from freshwater pulses) and we should be more worried about the surface mass balance of the Greenland cap.

Jim Williams

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Re: The Fast Transition
« Reply #8 on: April 28, 2017, 02:20:38 PM »
I can only respond that the ice cores tell us there are sudden and complete changes in the climatic regime.  These seem to be in years or less, not centuries.

I suspect you're referring to events like the Younger Dryas and the various Bond events? The consensus is that these are all caused by freshwater pulses in the north atlantic (indeed they're not global phenomena) caused by large lake releases. In theory this could be replicated by rapid total ice melt, but Lake Agassiz was around 22,000 km3 in volume which is ~4 times the current summer minimum ice volume so it's hard to see it having the same sort of effect. Indeed, the seasonal arctic ice volume variation is around 20,000 km3 and, coincidentally, the annual loss from the Greenland ice cap is about the same again, which suggests that the ocean is absorbing 40k km3 of fresh water annually anyway (plus whatever drains from siberia). So you would likely have to have a marked increase in Greenland melting to trigger climate changing amounts of freshwater release.

I've never worked it completely through before but those figures do kind of suggest that even should all the summer ice melt out there wouldn't be a dramatic effect on the global climate (at least not from from freshwater pulses) and we should be more worried about the surface mass balance of the Greenland cap.

I think you are referring to the beginning of the Younger Dryas, not the end of the Younger Dryas.

http://www.pnas.org/content/97/4/1331.full

Quote
The Greenland records show that climate changes have been very large, rapid, and widespread. Coolings were achieved in a series of steep ramps or steps and warmings in single steps. The more dramatic of the warmings have involved ≈8°C warming (8, 25) and ≈2× increases in snow accumulation (9), several-fold or larger drops in wind-blown materials (17), and ≈50% increase in methane, indicating large changes in global wetland area (5, 24).

For the best-characterized warming, the end of the Younger Dryas cold interval ≈11,500 years ago, the transition in many ice-core variables was achieved in three steps, each spanning ≈5 years and in total covering ≈40 years (26). However, most of the change occurred in the middle of these steps. The warming as recorded in gas isotopes occurred in decades or less ( 8 ). The most direct interpretation of the accumulation-rate record is that snowfall doubled over 3 years and nearly doubled in 1 year (9). Several records show enhanced variability near this and other transitions, including “flickering” behavior in which climate variables bounced between their “cold” level and their “warm” level before settling in one of them (27).

Archimid

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Re: The Fast Transition
« Reply #9 on: April 28, 2017, 02:41:40 PM »
Quote
There is a negative feedback mechanism that will likely prevent any runaway scenario in that more open ocean leads to more moisture in the air which leads to more snow cover on the surrounding continents. More snow covers leads to later/colder spring air temps (through increased albedo over land) and thus to a greater chance of more ice surviving into the following year.


That feedback mechanism does not exist. While indeed more snow is forming during fall and winter (when the sun doesn't shine) during Spring it is melting faster than ever resulting in less extent when the sun is shining.
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bbr2314

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Re: The Fast Transition
« Reply #10 on: April 28, 2017, 07:18:47 PM »
Quote
There is a negative feedback mechanism that will likely prevent any runaway scenario in that more open ocean leads to more moisture in the air which leads to more snow cover on the surrounding continents. More snow covers leads to later/colder spring air temps (through increased albedo over land) and thus to a greater chance of more ice surviving into the following year.


That feedback mechanism does not exist. While indeed more snow is forming during fall and winter (when the sun doesn't shine) during Spring it is melting faster than ever resulting in less extent when the sun is shining.
I don't think we have enough data to determine whether it exists or not just yet. Despite the record or near-record warmth so far this year, spring extent numbers are now above normal, and volume is possibly at a record at the moment. While the trend has been downwards in recent decades, I suspect we may be at a sort of inflection point at the moment, and it is premature to expect the downward trend to continue given the signal emerging this year/the past few, concurrent with record-low sea ice #s.





I suspect it will be another five years or so before the volume trend amplifies enough that extent begins to follow a similar deviation above the norm. But I could easily be wrong!

rboyd

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Re: The Fast Transition
« Reply #11 on: April 28, 2017, 08:06:34 PM »
bbr2314 - your second graph would seem to support a "more snow area in the winter but melts faster in the spring" hypothesis. Will be interesting to see what happens to snow extent in the next few weeks.

If there is greater snow cover on Northern Hemisphere land in Fall/Winter that should tend to reduce temperatures (although insulating the ground beneath). With increased cloudiness over the open Arctic Ocean in the darkness of Fall/Winter, it will tend to stay warmer. The overall effect may be to reduce the temperature differential between the Arctic and the rest of the Northern Hemisphere further?

Jim Williams

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Re: The Fast Transition
« Reply #12 on: April 28, 2017, 08:25:44 PM »
bbr2314 - your second graph would seem to support a "more snow area in the winter but melts faster in the spring" hypothesis. Will be interesting to see what happens to snow extent in the next few weeks.

If there is greater snow cover on Northern Hemisphere land in Fall/Winter that should tend to reduce temperatures (although insulating the ground beneath). With increased cloudiness over the open Arctic Ocean in the darkness of Fall/Winter, it will tend to stay warmer. The overall effect may be to reduce the temperature differential between the Arctic and the rest of the Northern Hemisphere further?

That would be Warm Ocean Cold Continents (WOCC).  The best evidence we have on the past tends to support this as a regime.  One where the Arctic becomes a mist shrouded maritime climate and (at least at first) the continents become seasonally heavily snow covered holders of the remaining cold.

That may, or may not, give way to an equable climate.


bbr2314

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Re: The Fast Transition
« Reply #13 on: April 28, 2017, 08:31:19 PM »
bbr2314 - your second graph would seem to support a "more snow area in the winter but melts faster in the spring" hypothesis. Will be interesting to see what happens to snow extent in the next few weeks.

If there is greater snow cover on Northern Hemisphere land in Fall/Winter that should tend to reduce temperatures (although insulating the ground beneath). With increased cloudiness over the open Arctic Ocean in the darkness of Fall/Winter, it will tend to stay warmer. The overall effect may be to reduce the temperature differential between the Arctic and the rest of the Northern Hemisphere further?
We were relatively low on extent, but numbers have now come up, so I would say for this spring we are about average in terms of overall extent, but possibly at a record high in terms of its snow-water-equivalent.

I think the only regions where ground insulation comes into meaningful play are those with permafrost. This is another warming feedback for the very far northern tier (Siberia, etc), but for the vast majority of the NHEM that is not covered in permafrost, I think it is a net reduction for temps. Still, this supports warmer temps in the Arctic itself due to the feedbacks you mentioned (clouds, and warming ground in permafrost areas).

I still believe we will soon hit a tipping point where the ocean is warm/ice-free enough to really rev up fall/winter snowfall numbers, enough so that we see snowpack begin enduring more and more readily into spring and early summer. We are already seeing this manifest in the anomalously high snow-volume numbers seen this year. How much more snowcover needs to build in fall/winter for extent to follow suit in the spring? I do not think we need that much more for this to begin occurring, though I could obviously be wrong (and the general consensus among most posters here is that I am wrong, so there's that too).

Nevertheless, the relationship between NHEM snow volume and arctic sea ice volume seems to have an inverse correlation, and as we continue seeing new lows throughout the year, it will be very interesting to see whether this relationship strengthens or weakens -- my bet is on the former.

Archimid

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Re: The Fast Transition
« Reply #14 on: April 28, 2017, 08:39:28 PM »
Quote
. Despite the record or near-record warmth so far this year, spring extent numbers are now above normal, and volume is possibly at a record at the moment

Please examine your second graph much more  closely. In particular:

1. Mean dates are from 1998-2011.The last graph I posted clearly show that the 1998-2016 mean  is much more lower than 50 years ago. Above 1 sd of this young mean probably means below a mean that included older data.

2. Extent is now slightly above 1sd of  1998-2011 mean and for the past week it has been so. But since the inflection point extent hugged the lower end of the variability for most of the end of winter and beginning of spring. In a cumulative manner, extent is running low, not high.

When you add this two the apparent big feedback is nothing but a whimper.


It wouldn't surprise me if the volume of snow reached record highs. There is much more water in the air,  but it doesn't have staying power.


Quote
While the trend has been downwards in recent decades, I suspect we may be at a sort of inflection point at the moment, and it is premature to expect the downward trend to continue given the signal emerging this year/the past few, concurrent with record-low sea ice

 See the years 1968 and 1989 on the Spring NH snow extent. As I hope you see, it is not unprecedented to have big drops followed by big recoveries. The problem is that the recoveries are much smaller in the recent years. There is no reason to think that trend will reverse.


Granted, after the ice disappears almost anything can happen. The Earth could freaking snowball for all we know. If that happens, then sure the ice might return, but it won't matter to any of us.
« Last Edit: April 28, 2017, 08:45:30 PM by Archimid »
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bbr2314

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Re: The Fast Transition
« Reply #15 on: April 28, 2017, 08:47:18 PM »
Quote
. Despite the record or near-record warmth so far this year, spring extent numbers are now above normal, and volume is possibly at a record at the moment

Please examine your second graph much more  closely. In particular:

1. Mean dates are from 1998-2011.The last graph I posted clearly show that the 1998-2016 mean  is much more lower than 50 years ago. Above 1 sd of this young mean probably means below a mean that included older data.

2. Extent is now slightly above 1sd of  1998-2011 mean and for the past week it has been so. But since the inflection point extent hugged the lower end of the variability for most of the end of winter and beginning of spring. In a cumulative manner, extent is running low, not high.

When you add this two the apparent big feedback is nothing but a whimper.


It wouldn't surprise me if the volume of snow reached record highs. There is much more water in the air,  but it doesn't have staying power.


Quote
While the trend has been downwards in recent decades, I suspect we may be at a sort of inflection point at the moment, and it is premature to expect the downward trend to continue given the signal emerging this year/the past few, concurrent with record-low sea ice

 See the years 1968 and 1989 on the Spring NH snow extent. As I hope you see, it is not unprecedented to have big drops followed by big recoveries. The problem is that the recoveries are much smaller in the recent years. There is no reason to think that trend will reverse.


Granted, after the ice disappears almost anything can happen. The Earth could freaking snowball for all we know. If that happens, then sure the ice might return, but it won't matter to any of us.
Those graphs are valuable, but I wish they had volume as well. Alas!

Jim Williams

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Re: The Fast Transition
« Reply #16 on: April 28, 2017, 09:13:49 PM »
I still believe we will soon hit a tipping point where the ocean is warm/ice-free enough to really rev up fall/winter snowfall numbers, enough so that we see snowpack begin enduring more and more readily into spring and early summer. We are already seeing this manifest in the anomalously high snow-volume numbers seen this year. How much more snowcover needs to build in fall/winter for extent to follow suit in the spring? I do not think we need that much more for this to begin occurring, though I could obviously be wrong (and the general consensus among most posters here is that I am wrong, so there's that too).

Nevertheless, the relationship between NHEM snow volume and arctic sea ice volume seems to have an inverse correlation, and as we continue seeing new lows throughout the year, it will be very interesting to see whether this relationship strengthens or weakens -- my bet is on the former.
If we had not been so overloading the atmosphere with C02 I think you'd be right, but as it is I think the snowpack will be a fleeting phenomenon.  I might buy into a short transition where the snow lasts as long as it did before....but not a state where the snowpack has any meaningful impact on overall climate.


oren

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Re: The Fast Transition
« Reply #17 on: April 29, 2017, 12:17:17 AM »
The snow discussion is getting off-topic. The topic itself is an excellent subject. I believe there are two key questions:
1. Can low ice cover at the end of summer (and/or anomalous accumulated heat in the water) cause significantly lower FDDs during winter?
2. Can lower FDDs and the resulting lower volume translate to low ice cover at the end of summer?
If both answers are true, we will have a fast transition.
The slow transition theory postulated FDDs unaffected by end-of-summer ice cover, cutting the feedback loop.
This year seems to show that  the answer to 1 is yes (though of course it could be just random coincidence). The jury is still out on 2. If we get a low ice cover in Sept, and then low FDDs next winter as well, it will give much more confidence in this fast feedback cycle.

Jim Williams

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Re: The Fast Transition
« Reply #18 on: April 29, 2017, 12:27:34 AM »
The snow discussion is getting off-topic.
I have to disagree in that an increase in snowfall seems to be one of the main characteristics of previous sudden warmings.  I might also add that there has been a marked increase in snowfall with the last winter.

Of course, winter snowfall is a marker, not the event.

StopTheApocalypse

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Re: The Fast Transition
« Reply #19 on: April 29, 2017, 01:04:04 AM »
The snow discussion is getting off-topic. The topic itself is an excellent subject. I believe there are two key questions:
1. Can low ice cover at the end of summer (and/or anomalous accumulated heat in the water) cause significantly lower FDDs during winter?
2. Can lower FDDs and the resulting lower volume translate to low ice cover at the end of summer?
If both answers are true, we will have a fast transition.
The slow transition theory postulated FDDs unaffected by end-of-summer ice cover, cutting the feedback loop.
This year seems to show that  the answer to 1 is yes (though of course it could be just random coincidence). The jury is still out on 2. If we get a low ice cover in Sept, and then low FDDs next winter as well, it will give much more confidence in this fast feedback cycle.

Excellent summary. I might generalize a bit and say: how much of the extra energy accumulated by the oceans in the case of a loss of summer sea ice will stay concentrated in the arctic, and how much will be distributed elsewhere in the earth? Is that a fair question? And if so, what are the main mechanisms by which this energy is distributed? I ask out of ignorance, not because I think the answers are not known.

Tor Bejnar

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Re: The Fast Transition
« Reply #20 on: April 29, 2017, 02:23:22 AM »
oren:  I like both your questions and your assessment of where we are in learning the answers.
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Archimid

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Re: The Fast Transition
« Reply #21 on: April 29, 2017, 02:37:13 AM »
The snow discussion is getting off-topic. The topic itself is an excellent subject. I believe there are two key questions:
1. Can low ice cover at the end of summer (and/or anomalous accumulated heat in the water) cause significantly lower FDDs during winter?
2. Can lower FDDs and the resulting lower volume translate to low ice cover at the end of summer?
If both answers are true, we will have a fast transition.
The slow transition theory postulated FDDs unaffected by end-of-summer ice cover, cutting the feedback loop.
This year seems to show that  the answer to 1 is yes (though of course it could be just random coincidence). The jury is still out on 2. If we get a low ice cover in Sept, and then low FDDs next winter as well, it will give much more confidence in this fast feedback cycle.

Spot on.
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DavidR

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Re: The Fast Transition
« Reply #22 on: April 29, 2017, 05:09:20 AM »
Will a "Blue Ocean" event in September trigger positive feedbacks that will rapidly (e.g. a decade or so) lead to a seasonally ice free Arctic with blue ocean being the predominant state throughout the summer months?

There is an assumption here that positive feedbacks are necessary to acheive this.  As the following graph shows, based on current trends, an ice free summer should become 'normal' within just a few years of an ice free September.

I expect the trigger for rapid collapse will be an ice free North Pole area,  say above 87degN. This will lead to slower ice formation after the summer peak and an alteration to the movement of the Beaufort Gyre. Even more MYI will be able to move into the Atlantic and disappear.  I expect Ice-Free summers to be a regular feature within a decade.
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Re: The Fast Transition
« Reply #23 on: April 29, 2017, 11:16:42 PM »
Will a "Blue Ocean" event in September trigger positive feedbacks that will rapidly (e.g. a decade or so) lead to a seasonally ice free Arctic with blue ocean being the predominant state throughout the summer months?

There is an assumption here that positive feedbacks are necessary to acheive this.  As the following graph shows, based on current trends, an ice free summer should become 'normal' within just a few years of an ice free September.

I expect the trigger for rapid collapse will be an ice free North Pole area,  say above 87degN. This will lead to slower ice formation after the summer peak and an alteration to the movement of the Beaufort Gyre. Even more MYI will be able to move into the Atlantic and disappear.  I expect Ice-Free summers to be a regular feature within a decade.

a) i share your opinion that this will be the case very soon as compared to some predictions (models)

b) BUT the graph shows nothing about the future, it shows the past and while the trends are clear, we have no clue which factors could either slow down or "beware" accelerate the process. it's just an assumption or "educated" guess at best. but again i share your point of view as to what lays ahead.

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Re: The Fast Transition
« Reply #24 on: April 30, 2017, 01:10:33 AM »
b) BUT the graph shows nothing about the future, it shows the past and while the trends are clear, we have no clue which factors could either slow down or "beware" accelerate the process.
The point of the graphs was to illustrate how quickly the projections show the arctic moving from an ice free September to an ice free summer. Its much  less than a decade without any trigger events.
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Chuck Yokota

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Re: The Fast Transition
« Reply #25 on: April 30, 2017, 02:50:44 AM »
Excellent summary. I might generalize a bit and say: how much of the extra energy accumulated by the oceans in the case of a loss of summer sea ice will stay concentrated in the arctic, and how much will be distributed elsewhere in the earth? Is that a fair question? And if so, what are the main mechanisms by which this energy is distributed? I ask out of ignorance, not because I think the answers are not known.

Since the net flow of heat has been and will continue to be from the warmer latitudes to the arctic, it might be a better way to ask the question as, will a warming arctic slow down the flow of heat from the lower latitudes?

From a simple heat conductance viewpoint, the answer might seem to be yes. For example, heat conductance through a wall decreases with a smaller temperature difference between the two sides of the wall.

However, the heat flow toward the arctic does not move by conduction, but by convection, with warmer air and water moving by currents carrying heat to the arctic, including water vapor that releases its heat through precipitation. A slowing AMOC would slow heat transport by ocean currents. On the other hand, increasingly turbulent weather would increase the flow of warm air to the arctic, and the air arriving at a warmer arctic would carry more precipitable water. I don't know what the net difference would be.

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Re: The Fast Transition
« Reply #26 on: April 30, 2017, 04:09:11 PM »
There was a paper linked and a very good graphic of the latest and best atmospheric modelling, back in January I think, perhaps on the freezing season thread, that showed the different atmospheric mechanisms and one scenario, possible even this year - a couple of months Ice free in summer they predicted Atmospheric heat transport to be ten times what we are used to, if memory serves. What it might get to if there is a full blown cyclone canon as Hansen suggests existed at the end of the last interglacial, that produced regular 60+m swells crossing the Atlantic to the Bahamas.

Doing a few numbers on the effect on water heat transport of the atmosphere dynamics we are seeing right now suggests that might be capable of being highly significant in increasing heat input and cold extraction also.

Eg/ I suggested on the melting season thread last week that the Average basin seal level pressure may have dropped by some 20hpa in less than a week causing an average rise in basin sea level of around 20cm. That equates to 2800 cubic km of water incoming from the Pacific and Atlantic.
For this to happen in four days say:
2800 billion cubic m / 96hrs =29166666667 cubic m / hr
/ 3600 seconds per hr = 8.1 million cubic metres per second = 8.1 sverdrups

the AMOC is supposed to be around 15 sverdrups at present.

We saw a big inrush at that time through Bering Strait, but the channel cross sectional area through there is about 40km wide x 0.03 km deep = 1.2 square km = 1.2 million sqm

So for 8.1 million cubic km to have passed through there it would have had to have flowed at 8.1 million/ 1.2m = 6.75 m/s = 24kmph.

clearly it wasn't. And there was persistent high winds sending water and ice out the Atlantic exits at the time also. So quite on the cards that at depth (limited by the Europe-Faroe-Iceland-Greenland rise to not more than 500m depth of course, so warm Atlantic tidal mixed zone water, not bottom water) there was big incoming flows from the Atlantic, and the total inflow could well have been similar in volume to the AMOC, as it was replacing not just the 20cm but the windblown surface outflow additionally.

Now at present in Antarctica we have a high of over 1050hpa in the interior, and nearby large depressions with 940 hpa pressure.
If a scenario should develop with oscillation between basin pressures like those, and VERY powerful winds occurring also, as a result of over 20 C water temperatures flooding into the Basin, and Greenland and large melt-pool in the Nth Atlantic adjacent. Perhaps pressure changes of five times what we are currently seeing, or more, on the time scale of a few days, and very big storm surges, could set up a pumping mechanism with hot in and cold out ocean current transportation capability in the order of 10x what we are used to.  :o :P
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Re: The Fast Transition
« Reply #27 on: April 30, 2017, 09:42:56 PM »
I agree with Hyperion here, plus once the ice is shattered it will bleed out through the CAA taking a huge reserve of fresh water with it. Then we'll face accelerated base water exiting through Fram as evaporation and freezing in their turn contribute increasing amounts of dense saline water to the halocline, creating in it's turn to an increase of Atlantic water ingress.

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Re: The Fast Transition
« Reply #28 on: April 30, 2017, 10:14:39 PM »
I agree with Hyperion here, plus once the ice is shattered it will bleed out through the CAA taking a huge reserve of fresh water with it. Then we'll face accelerated base water exiting through Fram as evaporation and freezing in their turn contribute increasing amounts of dense saline water to the halocline, creating in it's turn to an increase of Atlantic water ingress.
I am also in agreement.

Perhaps Sandy was the first instance of such a storm? We've seen several close glances the past few years as well, but perhaps the record minimum in 2012 was directly to blame on the hybrid-monster situation.

If that is the case, and we see another record low this year, as all indicators seem to be pointing towards, perhaps we will see an even worse event this fall?

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Re: The Fast Transition
« Reply #29 on: April 30, 2017, 10:25:03 PM »
Should note how snowy the Rockies currently are as well, most all stations are WAY above normal in terms of volume. I suspect this is directly related to the record-low sea ice volume.


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Re: The Fast Transition
« Reply #30 on: May 03, 2017, 05:17:38 AM »
Greater role for Atlantic inflows on sea-ice loss in the Eurasian Basin of the Arctic Ocean

Abstract

Arctic sea-ice loss is a leading indicator of climate change and can be attributed, in large part, to atmospheric forcing. Here, we show that recent ice reductions, weakening of the halocline, and shoaling of the intermediate-depth Atlantic Water layer in the eastern Eurasian Basin have increased winter ventilation in the ocean interior, making this region structurally similar to that of the western Eurasian Basin. The associated enhanced release of oceanic heat has reduced winter sea-ice formation at a rate now comparable to losses from atmospheric thermodynamic forcing, thus explaining the recent reduction in sea-ice cover in the eastern Eurasian Basin. This encroaching “atlantification” of the Eurasian Basin represents an essential step toward a new Arctic climate state, with a substantially greater role for Atlantic inflows.

http://science.sciencemag.org/content/356/6335/285

"In winter from 2013-2015, the cap separating the deep water and surface water disappeared completely in some locations, allowing the warm Atlantic waters to reach the surface and cut further into sea ice pack. At the same time, warm air has further reduced sea ice, which is allowing still more mixing of the ocean layers. The result is a feedback loop that is essentially turning roughly a third of the eastern Arctic Ocean into something resembling the ice-free Atlantic Ocean ... Rapid changes in the eastern Arctic Ocean, which allow more heat from the ocean interior to reach the bottom of sea ice, are making it more sensitive to climate changes,” Polyakov said. “This is a big step toward the Arctic with seasonal sea-ice cover."

https://www.scientificamerican.com/article/the-arctic-ocean-is-becoming-more-like-the-atlantic-ocean/

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Re: The Fast Transition
« Reply #31 on: May 03, 2017, 05:49:56 PM »
Will a "Blue Ocean" event in September trigger positive feedbacks that will rapidly (e.g. a decade or so) lead to a seasonally ice free Arctic with blue ocean being the predominant state throughout the summer months?
These feedbacks would include:
- Albedo Effects (possibly mitigated by cloud effects)
- Reduced separation between the Arctic and Northern Hemisphere climate regions, allowing for greater amounts of heat transfer into the Arctic
- Greater level of storms and waves driven by open ocean (and heat contrast between ocean and land)
- Mixing of the water column in the absence of a thick ice cover, bringing up deeper, warmer water to the surface

With the extra heat taken into the open waters during Spring/Summer being vented into the atmosphere in the Fall/Winter months, will the freezing season be significantly reduced (i.e. less and less FDD's) - reducing the ability of the ice to reform and thicken?

Could the Arctic then transition to near ice free year round as the increased energy taken in through the spring/summer, together with greater heat transport from the south, reduces the FDD's further and further?
- Thinner ice at the start of the melt season leads to greater warming from reduced albedo, leads to less FDD's, leads to yet thinner ice the next melt season.


http://onlinelibrary.wiley.com/doi/10.1002/2016GL070526/full

On the atmospheric response experiment to a Blue Arctic Ocean

Abstract

We demonstrated atmospheric responses to a reduction in Arctic sea ice via simulations in which Arctic sea ice decreased stepwise from the present-day range to an ice-free range. In all cases, the tropospheric response exhibited a negative Arctic Oscillation (AO)-like pattern. An intensification of the climatological planetary-scale wave due to the present-day sea ice reduction on the Atlantic side of the Arctic Ocean induced stratospheric polar vortex weakening and the subsequent negative AO. Conversely, strong Arctic warming due to ice-free conditions across the entire Arctic Ocean induced a weakening of the tropospheric westerlies corresponding to a negative AO without troposphere-stratosphere coupling, for which the planetary-scale wave response to a surface heat source extending to the Pacific side of the Arctic Ocean was responsible. Because the resultant negative AO-like response was accompanied by secondary circulation in the meridional plane, atmospheric heat transport into the Arctic increased, accelerating the Arctic amplification.

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nick

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Re: The Fast Transition
« Reply #32 on: May 04, 2017, 01:25:48 PM »
I suspect you're referring to events like the Younger Dryas and the various Bond events? The consensus is that these are all caused by freshwater pulses in the north atlantic (indeed they're not global phenomena) caused by large lake releases. In theory this could be replicated by rapid total ice melt, but Lake Agassiz was around 22,000 km3 in volume which is ~4 times the current summer minimum ice volume so it's hard to see it having the same sort of effect. Indeed, the seasonal arctic ice volume variation is around 20,000 km3 and, coincidentally, the annual loss from the Greenland ice cap is about the same again, which suggests that the ocean is absorbing 40k km3 of fresh water annually anyway (plus whatever drains from siberia). So you would likely have to have a marked increase in Greenland melting to trigger climate changing amounts of freshwater release.

I've never worked it completely through before but those figures do kind of suggest that even should all the summer ice melt out there wouldn't be a dramatic effect on the global climate (at least not from from freshwater pulses) and we should be more worried about the surface mass balance of the Greenland cap.

Well that's embarrassing. I'm two orders of magnitude out on my Greenland figures. Annual loss is 200km3 not 20,000km3. Oops. So actually greenland melt is trivial compared to SI seasonal variation. That'll teach me for doing maths in my head. 

Anyway, not relevant but I thought I'd correct myself.

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Re: The Fast Transition
« Reply #33 on: May 04, 2017, 03:19:39 PM »
Hullo Nick,

I picked up this quote from you

"Annual loss is 200km3 not 20,000km3. Oops. So actually greenland melt is trivial compared to SI seasonal variation."

But Greenland melt is not trivial. PIOMAS say that the average annual loss of arctic sea ice is 280 km3. Annual Greenland ice loss since 2002 is estimated at (would you believe it) 281 (+/-24) gigatonnes, i.e.280 km3. (Data source: Ice mass measurement by NASA's GRACE satellites. Credit: NASA). i.e. equally significant as loss in sea ice volume.

To quote PIOMAS "To melt the additional 280 km3 of sea ice, the amount we have have been losing on an annual basis based on PIOMAS calculations, it takes roughly 8.6 x 1019 J or 86% of U.S. energy consumption." 

So in an average year (not that there is one) in the Arctic region about 560 km3 of ice is turned into liquid water permanently, using energy equal to about 170% of total US energy use.

Now I do not have a clue how much that represents of excess energy being trapped by increased CO2 concentrations, but relatively small differences can, I presume, have major climatic effects. Thanks for the quote, it made me hunt around a bit for the magic stuff called data.
« Last Edit: May 04, 2017, 04:17:06 PM by gerontocrat »
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Re: The Fast Transition
« Reply #34 on: January 04, 2020, 07:38:32 AM »
Greater role for Atlantic inflows on sea-ice loss in the Eurasian Basin of the Arctic Ocean
Arctic sea-ice loss is a leading indicator of climate change and can be attributed, in large part, to atmospheric forcing. Here, we show that recent ice reductions, weakening of the halocline, and shoaling of the intermediate-depth Atlantic Water layer in the eastern Eurasian Basin have increased winter ventilation in the ocean interior, making this region structurally similar to that of the western Eurasian Basin. The associated enhanced release of oceanic heat has reduced winter sea-ice formation at a rate now comparable to losses from atmospheric thermodynamic forcing, thus explaining the recent reduction in sea-ice cover in the eastern Eurasian Basin. This encroaching “atlantification” of the Eurasian Basin represents an essential step toward a new Arctic climate state, with a substantially greater role for Atlantic inflows.
...

"Decadal Changes of the Reflected Solar Radiation and the Earth Energy Imbalance" by Dewitte , Clerbaux and Cornelis.

Abstract: Decadal changes of the Reflected Solar Radiation (RSR) as measured by CERES from 2000 to 2018 are analysed. For both polar regions, changes of the clear-sky RSR correlate well with changes of the Sea Ice Extent. In the Arctic, sea ice is clearly melting, and as a result the earth is becoming darker under clear-sky conditions. However, the correlation between the global all-sky RSR and the polar clear-sky RSR changes is low. Moreover, the RSR and the Outgoing Longwave Radiation (OLR) changes are negatively correlated, so they partly cancel each other. The increase of the OLR is higher then the decrease of the RSR. Also the incoming solar radiation is decreasing. As a result, over the 2000–2018 period the Earth Energy Imbalance (EEI) appears to have a downward trend of −0.16 ± 0.11 W/m2dec. The EEI trend agrees with a trend of the Ocean Heat Content Time Derivative of −0.26 ± 0.06 (1 σ) W/m2dec.

Over the 2000–2018 period the Arctic clear-sky RSR shows a decreasing trend of −0.13 W/m2dec.

Figure 8. Arctic clear-sky RSR compared to Arctic SIE. Purple curve, left scale: Clear-sky RSR contribution of zone from 60∘ N to 90∘ N. Green curve, right scale: Arctic SIE.


https://www.mdpi.com/2072-4292/11/6/663/htm#

Hefaistos

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Re: The Fast Transition
« Reply #35 on: January 04, 2020, 07:55:31 AM »
From the same paper as in previous post, with the "surprising" results from CERES with a negative trend of Earth Energy Imbalance as well as a negative trend of Ocean Heat Content Time Derivative :

"The Earth Energy Imbalance (EEI) shows a trend of −0.16 ± 0.11 W/m2dec. The decreasing trend in EEI is in agreement with a decreasing trend of −0.26 ± 0.06 W/m2dec in the Ocean Heat Content Time Derivative (OHCTD) after 2000.
The OHCTD over the period 1960–2015 shows three different regimes, with low OHCTD prior to 1982, rising OHCTD from 1982 to 2000, and decreasing OHCTD since 2000. These OHCTD periods correspond to periods of slow/rapid/slow surface temperature rise [16,17], to periods of strong La Ninas/El Ninos/La Ninas [14,18], and to periods of increasing/decreasing/increasing aerosol loading [19,20]. "

Figure 15. Purple curve: running yearly mean EEI. Green line: linear fit to running yearly mean EEI. Blue curve: 10 year running mean OHCTD. Orange curve: piecewise linear fit to OHCTD.

Glen Koehler

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Re: The Fast Transition
« Reply #36 on: March 10, 2020, 12:38:01 AM »
"Decadal Changes of the Reflected Solar Radiation and the Earth Energy Imbalance" by Dewitte , Clerbaux and Cornelis.
     For both polar regions, changes of the clear-sky RSR correlate well with changes of the Sea Ice Extent. In the Arctic, sea ice is clearly melting, and as a result the earth is becoming darker under clear-sky conditions. However, the correlation between the global all-sky RSR and the polar clear-sky RSR changes is low. Moreover, the RSR and the Outgoing Longwave Radiation (OLR) changes are negatively correlated, so they partly cancel each other. The increase of the OLR is higher than the decrease of the RSR. Also the incoming solar radiation is decreasing. As a result, over the 2000–2018 period the Earth Energy Imbalance (EEI) appears to have a downward trend of −0.16 ± 0.11 W/m2dec. The EEI trend agrees with a trend of the Ocean Heat Content Time Derivative of −0.26 ± 0.06 (1 σ) W/m2dec.
   Over the 2000–2018 period the Arctic clear-sky RSR shows a decreasing trend of −0.13 W/m2dec.

https://www.mdpi.com/2072-4292/11/6/663/htm#
And RE https://forum.arctic-sea-ice.net/index.php?action=dlattach;topic=1999.0;attach=140635;image

Very interesting article.  But it seems to contradict other reports that show continued increase in total ocean heat content (OHC).  Also hard to understand how net  earth energy balance and OHC can be trending down at same time as continued increase in global CO2 and with relatively consistent increase in measured surface temperature over same period.  Or maybe I am misinterpreting the conclusions.  Explanation or discussion by those who actually understand this stuff welcomed.


« Last Edit: March 10, 2020, 01:17:04 AM by Glen Koehler »

Glen Koehler

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Re: The Fast Transition
« Reply #37 on: March 10, 2020, 12:58:30 AM »
RE Wipneus Feb 29 2020 thickness graph
https://forum.arctic-sea-ice.net/index.php?action=dlattach;topic=119.0;attach=144514;image
and
RE 1.7-2m threshold thickness for seasonal ice
 https://forum.arctic-sea-ice.net/index.php/topic,1999.msg111458.html#msg111458

Jumping the gun, but with freezing season beginning to wane and so not too far from max thickness, areas that are yellow or green on the Wipneus graph are at high risk to be seasonal, thus to melt out by September (plus possible export of thick ice north of Greenland via the Fram Strait).
« Last Edit: March 10, 2020, 01:04:14 AM by Glen Koehler »

LRC1962

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Re: The Fast Transition
« Reply #38 on: March 10, 2020, 07:26:31 PM »
There is a brief mention of permafrost. If the land warms up beyond a certain point then the chances of seeing blue Arctic will become much greater as any ice near the land will be gone earlier in the melt season.
Now I normally avoid Fox like the plague, but I found this story interesting.https://www.fox43.com/article/news/local/contests/arctic-permafrost-is-melting-so-fast-its-damaging-the-equipment-scientists-use-to-measure-it/521-7adcbad7-1d7d-47a8-b938-d3749515ed75
Quote

In the Arctic, a changing climate isn’t something that might happen in the near future. In the uppermost stretches of the Northern Hemisphere, it’s already happening now.

Temperatures are warming; sea ice is retreating.
Now a better science approach is: https://www.theguardian.coam/environment/2019/jun/18/arctic-permafrost-canada-science-climate-crisis
Quote
Permafrost at outposts in the Canadian Arctic is thawing 70 years earlier than predicted, an expedition has discovered, in the latest sign that the global climate crisis is accelerating even faster than scientists had feared.
Granted this is old news and I have been avoiding this site for the last year or so because it is getting very depressing for me.
If you tie in the melting permafrost and what is happening with the ice then a fast transition is unavoidable. The permafrost kept the land cold which than was able to keep the water cold therefore allowed the ice to keep thick enough to stick around.  With the permafrost going much faster then thought possible, it is now unable to keep things cold. On top of that you now are seeing more  and more large scale fires because of that loss which is heating the air even more adding ash to the ice. End result is the ice will be hit harder every summer.
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