Feedbacks

[crandles]

Started this thread for any comments on what might or might not be an arctic sea ice feedback and how well established or otherwise they might be.

A couple discussed recently:

methane cycle: more release of methane when windier and less ice cover causing methane GHG effect which in turn causes less cover and stormier weather. Positive feedback.

Ice cracking in February 2013 from thinner more mobile ice allows more ice to form in February and March. Negative feedback -  though cracking later that approx mid April is likely to be positive feedback though albedo effect. Probably only speculation not established.

[Neven]

Good thread! Something I always wanted to do a blog post on, but, of course, never came around to (psychological time).

Here's one of my favourite negative feedbacks: Increase in snowfall during autumn and winter.

[crandles]

Here's one of my favourite negative feedbacks: Increase in snowfall during autumn and winter.

On sea ice or on land?

On sea ice it increases the insulation and decreases the equilibrium thickness that the ice can reach which is a positive feedback assuming we get more snowfall with warmer autumn but it increases the albedo in spring which is negative feedback and I am not sure which is more important.

Increases snow on land presumably just keeps temperatures down so is a simple negative feedback.

[johnm33]

If the snow falls on the permafrost too early it would inhibit maximum freezing, just as it protects winter wheat in the mid west.
Shattered ice sheets are more susceptible to wind action, so if the winds are increasing the flow through Fram, it can only be replaced by warmer AW, leading to thinner more fractured ice, and if that water comes in at the bottom more/sooner potential ch4 release.

[ggelsrinc]

If the snow falls on the permafrost too early it would inhibit maximum freezing, just as it protects winter wheat in the mid west.
Shattered ice sheets are more susceptible to wind action, so if the winds are increasing the flow through Fram, it can only be replaced by warmer AW, leading to thinner more fractured ice, and if that water comes in at the bottom more/sooner potential ch4 release.

Fram isn't the only place on Earth and we have been destroying our northern forests for thousands of years. That has a cooling effect.

If Fram is so much of a problem, plug it up! Plug up the whole ASI distribution system! ASI only exists, because land masses plug it up and it gets cold at the poles.

[jdallen]

If Fram is so much of a problem, plug it up! Plug up the whole ASI distribution system! ASI only exists, because land masses plug it up and it gets cold at the poles.

I'm trying to find words which adequately describe just how impossible an idea this is.

It would demand more resources and energy than has been expended building every dam and canal    ever constructed, anywhere, by anyone.

I think that the fact our climate will change is now a foregone conclusion.  We can only remediate the effects on society and human welfare.

Attenuating the rate of change is still a good idea.  You have far different results when dropping a basket of eggs vs lowering it to the floor.  Reducing fossil carbon burn would be a lowering vs dropping move. It is also far, FAR less serious a challenge than plugging up the arctic.

Will that prevent the sublimation of clathrates?  I doubt it, but I'm also find dubious assertions we will see exponential increases in their melt.  The water needs to warm far more, and even if it were prompt, it will take decades for the heat to reach the deposits through overlying sediments insulating them.

[wili]

Feedbacks are often complex.

Take just water vapor.

With a newly open Arctic Ocean (even for part of the summer), there will be much more evaporation and so humidity in the region. That will lead (as noted above) to more snowfall in the fall, which has different effects (as feedbacks) when it falls on sea ice than on land.

The water vapor itself is a GHG, of course, so clearly positive feedback, and that is and will continue to be its main overall effect, afaics.

But as the water vapor extends up higher and higher into the troposphere, it also increases the ability of heat to be conducted from near ground level up to higher altitudes and ultimately out to space. (These behaviors are sometimes subsumed under the term "lapse rate," an area I'm still learning about, and I would love to have instruction on it if anyone has studied it in more depth.)

It is my understanding that so far it is only in the tropics where humidity is high enough throughout the air column for this kind of conduction to be a significant factor. On average, globally, humidity is a fairly strong positive feedback. My point is just that these things do get complicated in (to me) interesting ways.

And of course then there is the complex issue of clouds from said humidity both blocking sun (negative feedback, in evidence last summer) and holding in heat (positive feedback).

These complexities are some of the reasons that people turn to computer models. But ultimately you first need to know something of the relative power of each of the factors (and to include at least all significant factors) for the models to have any use at all.

[Richard Rathbone]

Lapse rate is a fancy term for the temperature gradient in an atmosphere.

If the atmosphere is simple, its easy to calculate and the surface temperature can be easily obtained by integrating the lapse rate from the edge of the atmosphere to the surface.

When the atmosphere isn't simple, the lapse rate gets complicated but the temperature calculation is still best done from space to ground by integration of a complicated lapse rate.

The ability of water to exist in vapour, liquid and solid phases in our atmosphere makes it complicated and no one has a decent model of it yet. (I reckon the sort of errors that are around 10 W/m2 in current climate models should be under 1 before I'd count the models as decent and I'd prefer them under 0.1 before I put much confidence into their predictions.)

If you want a detailed textbook treatment try "Principles of Planetary Climate" by Pierrehumbert. 

[ggelsrinc]

If Fram is so much of a problem, plug it up! Plug up the whole ASI distribution system! ASI only exists, because land masses plug it up and it gets cold at the poles.

I'm trying to find words which adequately describe just how impossible an idea this is.

It would demand more resources and energy than has been expended building every dam and canal    ever constructed, anywhere, by anyone.

I think that the fact our climate will change is now a foregone conclusion.  We can only remediate the effects on society and human welfare.

Attenuating the rate of change is still a good idea.  You have far different results when dropping a basket of eggs vs lowering it to the floor.  Reducing fossil carbon burn would be a lowering vs dropping move. It is also far, FAR less serious a challenge than plugging up the arctic.

Will that prevent the sublimation of clathrates?  I doubt it, but I'm also find dubious assertions we will see exponential increases in their melt.  The water needs to warm far more, and even if it were prompt, it will take decades for the heat to reach the deposits through overlying sediments insulating them.

Dams are made with concrete. Now, what is the most sensible material to use in the Arctic? Is there some reason why ice can't be anchored in the ocean or rigged with sails to control it's direction? I'm not talking about using thin ice. Consider:

Pykrete is a composite material made of approximately 14 percent sawdust or some other form of wood pulp (such as paper) and 86 percent ice by weight (6 to 1 by weight). Its use was proposed during World War II by Geoffrey Pyke to the British Royal Navy as a candidate material for making a huge, unsinkable aircraft carrier. Pykrete has some interesting properties, notably its relatively slow melting rate (because of low thermal conductivity), and its vastly improved strength and toughness over ice; it is closer in form to concrete.

Source: http://en.wikipedia.org/wiki/Icecrete

It sounds like a good way to get rid of junk mail and old newspapers.

[wili]

Thanks, Richard. I'll just point out that, while temperature is the usual variable that lapse rate refers to, it can refer to variable that changes with altitude in a column of atmosphere.

http://en.wikipedia.org/wiki/Lapse_rate

But again, this is an area that I am still struggling to comprehend. So any insight is very welcome.

jd, all it takes for the methane to get into the water column is pathways. As Shakhova points out in this video, there are plenty of potential and actual pathways. But yes, uncertainty still abounds in this area. http://climatestate.com/2013/08/29/arctic-methane-outgassing-on-the-east-siberian-shelf-an-interview-with-dr-natalia-shakhova/

(Meanwhile, try to avoid the temptation to ftt. There is no more hope in trying to address bottomless idiocy than to fill in the Fram.)

[jdallen]

jd, all it takes for the methane to get into the water column is pathways. As Shakhova points out in this video, there are plenty of potential and actual pathways. But yes, uncertainty still abounds in this area. http://climatestate.com/2013/08/29/arctic-methane-outgassing-on-the-east-siberian-shelf-an-interview-with-dr-natalia-shakhova/

(Meanwhile, try to avoid the temptation to ftt. There is no more hope in trying to address bottomless idiocy than to fill in the Fram.)

Noted on both counts, wili.

Regarding methane, I'm not so much doubting it can escape, so much as I question the idea of prompt massive releases.  I don't see a way where methane release acts as it's own positive feedback; it will take significant time for a modest increase in trapped heat to warm ocean to where that heat can be picked up by clathrates. The energy required for phase change is our friend here.  I see the methane as having more impact on weather, particularly arctic.

[Wipneus]

These behaviors are sometimes subsumed under the term "lapse rate," an area I'm still learning about, and I would love to have instruction on it if anyone has studied it in more depth.

The lapse rate ( the temperature profile ), is at the heart of the green house gas effect:

Increasing greenhouse gas concentration effectively raises the height at which thermal radiation is transmitted to space.  Normally on earth the higher level is cooler and the radiation is less creating an in-balance and the earth heats in response.

Without the lapse rate there is no greenhouse gas effect. In cases  where temperature increase with height, the greenhouse gas effect actually increases the outgoing radiation. Interestingly this may happen on earth in (ant-) Arctic winter when the absence of solar warming of the surface creates a temperature inversion.
 

 

[wili]

Thanks for those points, jd. I've been telling myself much the same thing--the very act of these things dissociating will have a cooling effect on the surrounding area. Of course, the melting of Arctic sea ice also required a phase change. And yet, as we all know, minimum ice volume levels went from around 20,000 k^3 in the '70's to 3,000 last year in spite of those basic physics and in spite of all the physics-based models saying that couldn't happen for at least many more decades to centuries.

As neven keeps saying, the Arctic is full of surprises. I just hope seabed methane doesn't 'surprise' us with an utterly disastrous 'discontinuity.'

It's surely worth keeping an eye on, I trust you agree.

Wipneus, thanks for those pointers. But I lost you at your last two sentences: "In cases  where temperature increase with height, the greenhouse gas effect actually increases the outgoing radiation. Interestingly this may happen on earth in (ant-) Arctic winter when the absence of solar warming of the surface creates a temperature inversion."

How can GHG's create increased outgoing radiation. Are you talking about the conductive qualities of water vapor that I mentioned? Or is there another dynamic? (These are exactly the complications that confuse me about what would seem a fairly straightforward concept--the temperature gradient of the atmosphere as you go up the air column.)

Care to elaborate a bit, or point me in the direction of an accessible source on it? (I know, I should break down and buy the Pierrehumbert text book. Maybe tomorrow...)

[Richard Rathbone]

Simplified model.

Planet is sufficiently far from sun that it radiates at a significantly different wavelength. (true for Earth)

Atmospheric gasses are effectively transparent to incoming solar radiation but not outgoing IR radiation which gets absorbed and re-emitted within the atmosphere.

Divide the atmosphere into layers such that each layer is just thick enough to completely absorb the IR radiation coming to it from the layer above and the layer below. The bottom layer receives energy from the surface, (and the layer above), the top one emits it to space (and the layer below) and the ones in between just bounce it around between them.

All radiation to space goes from that top layer and depends on its temperature, which is fixed by a balance with the incoming solar radiation. Adding greenhouse gasses increases the number of layers, making each layer thinner. If the top layer is thinner, radiation to space happens from higher up and there is more of the atmosphere in between that layer and the surface.

If temperature increases as you go down through the atmosphere, this extra height will translate to a higher temperature at the surface. (this being the normal situation) If temperature decreases as you go down through the atmosphere, the extra height will result in a lower temperature at the surface.

[Wipneus]

How can GHG's create increased outgoing radiation. Are you talking about the conductive qualities of water vapor that I mentioned? Or is there another dynamic? (These are exactly the complications that confuse me about what would seem a fairly straightforward concept--the temperature gradient of the atmosphere as you go up the air column.)

No, I am just talking about temperature profiles and IR active gasses (aka greenhouse gasses).

On earth the atmosphere is heated at the bottom (from incoming solar for which the atmosphere is largely transparent), the cooling is mostly higher in the atmosphere (by longer wavelength outgoing radiation emiited by the green house gas molecules) . This is the basic reason why it is colder when you go up.

On Saturn moon Titan, the incoming solar radiation is absorbed by haze high in the atmosphere, little reaches the surface. This leads to an atmosphere where the temperature increases with height. Perhaps google, for "greenhouse effect Titan" to see what consequences this has.

In Antarctic winter there is no incoming solar at all. Under clear sky the surface can cool to -80 ^oC, much colder than the atmosphere above. Satellite measurement  of outgoing heat radiation spectrum show that CO2 causes radiation in the specific bands to be enhanced (where elsewhere CO2 supressed outgoing radiation):


(Nimbus 4, Hanel etal, 1972)

Note that this does not say that the enhanced greenhouse gas effect is cooling Antarctic surface temperatures, most of the heat there comes from more moderate latitudes.

Care to elaborate a bit, or point me in the direction of an accessible source on it? (I know, I should break down and buy the Pierrehumbert text book. Maybe tomorrow...)

The PoPC book is indeed excellent for those that are not afraid of the (differential) equations. The pre-print pdf that  Pierrehumbert had on his home page, is still downloadable if you look for it on the net.

[Wipneus]

Forgot to mention, Science of Doom is an excellent blog dedicated to climate science, especially the atmospheric science. Look at the series "CO2" and "Atmospheric Radiation and the Greenhouse Effect".

[wili]

"On Saturn moon Titan, the incoming solar radiation is absorbed by haze high in the atmosphere, little reaches the surface. This leads to an atmosphere where the temperature increases with height."

Thanks, Wipneus. That makes sense.

[jdallen]

Thanks for those points, jd. I've been telling myself much the same thing--the very act of these things dissociating will have a cooling effect on the surrounding area. Of course, the melting of Arctic sea ice also required a phase change. And yet, as we all know, minimum ice volume levels went from around 20,000 k^3 in the '70's to 3,000 last year in spite of those basic physics and in spite of all the physics-based models saying that couldn't happen for at least many more decades to centuries.

Absolutely, wili; 2007, 2011 and 2012 collectively shocked the daylights out of a lot of people.

I would point out a few key differences.

Surface ice at the interface between air and water is a far more dynamic system vis-a-vis heat exchange.  There are means by which heat may be transported rapidly to either side of the interface, and the nature of the media (air, seawater) permit rapid transfer of heat over large areas and long distances in prompt time frames (hours to weeks).

By contrast, clathrates tend to be isolated from direct exposure to "volatile" media.  Those which *do* form on the sea floor exposed directly to sea water are indeed subject to similar but much lesser exposure to rapid transfers of energy, but most are buried at depth - a few to hundreds of meters - away from the primary surface at which heat is exchanged. 

The media in which clathrates are held - oceanic sediment - also itself is static.  Heat moves via conduction rather convection, so for clathrates to be exposed to higher temperatures requires that the entire body be heated .  Add the higher density of the material - sediment which is at least twice the density of water - and by nature there will be considerable buffering of heat. That increased density provides insulation which physically insulates clathrates against higher temperature.

So in short, from a systems standpoint, the increased but continuous release of methane makes considerable sense to me.  In effect, it is part of the secondary effects which will continue to provide thermal forcing long after we stop burning fossil fuel, and long term will almost no doubt dwarf the contribution of carbon made to the atmosphere by humanity.  Unlike human CO2 emissions, I think the rate at which methane is released will be both smoother, and longer term. 

What humanity in effect has done is lit the "kindling" of climate change.  We can try to damp the fire some as it were by reducing our emissions. Absent dramatic decades long efforts to dump excess heat out of our environment, there is no way now I think we can put out the "fire".  Our task then becomes to manage the change to produce the least harm, which is also a huge challenge.  But by pursuing it, we may be able to prevent a controllable change from escaping to become conflagration that consumes most of civilization.

As neven keeps saying, the Arctic is full of surprises. I just hope seabed methane doesn't 'surprise' us with an utterly disastrous 'discontinuity.'

It's surely worth keeping an eye on, I trust you agree.

OH I most certainly do.  One of my best academic products (never published, but still well received) when pursing my BS in Geology was on the topic of paradigm change in science, in particular the struggle between incrementalism vs catastrophism in the 19th and early 20th centuries.  In specific I looked at the evolution of understanding of a geologic feature in Eastern Washington State, surveyed extensively by one J Harlen Bretz who in my view is a little known but one of the more notable contributors to 20th century geology.

(Slightly Off topic but relevant links - they do include ice - :
http://hugefloods.com/Mystery.html
http://www.glaciallakemissoula.org/story.html
)

So, by extension, I am quite accepting of possible departures from incremental state changes in a system.  It is in exactly my study of the history of science that led me to my current understanding of dynamic systems and "tip over" - points at which a system transitions dramatically and irreversibly to a new state.  Methane by all means bears considerable watching.

[Shared Humanity]

jd, all it takes for the methane to get into the water column is pathways. As Shakhova points out in this video, there are plenty of potential and actual pathways. But yes, uncertainty still abounds in this area. http://climatestate.com/2013/08/29/arctic-methane-outgassing-on-the-east-siberian-shelf-an-interview-with-dr-natalia-shakhova/

(Meanwhile, try to avoid the temptation to ftt. There is no more hope in trying to address bottomless idiocy than to fill in the Fram.)

Noted on both counts, wili.

Regarding methane, I'm not so much doubting it can escape, so much as I question the idea of prompt massive releases.  I don't see a way where methane release acts as it's own positive feedback; it will take significant time for a modest increase in trapped heat to warm ocean to where that heat can be picked up by clathrates. The energy required for phase change is our friend here.  I see the methane as having more impact on weather, particularly arctic.

It certainly seems unlikely that increased levels of methane released into the atmosphere by the slow degradation of frozen soils underwater would trigger a sudden burst of methane. Could this sudden burst be triggered, instead, by the physical changes in the  sea floor that are causing slow  increases of methane in the East Siberian Sea?

Melting permafrost on land results in the creation of karsts and these depressions and resulting drainage accelerate the deterioration  of the surrounding permafrost. Could a similar mechanism work in the East Siberian Sea? Is it really necessary for the water temperature to increase in order for there to be a burst of methane?

[jdallen]

It certainly seems unlikely that increased levels of methane released into the atmosphere by the slow degradation of frozen soils underwater would trigger a sudden burst of methane. Could this sudden burst be triggered, instead, by the physical changes in the  sea floor that are causing slow  increases of methane in the East Siberian Sea?

Melting permafrost on land results in the creation of karsts and these depressions and resulting drainage accelerate the deterioration  of the surrounding permafrost. Could a similar mechanism work in the East Siberian Sea? Is it really necessary for the water temperature to increase in order for there to be a burst of methane?

I think the effect would still be localized, much like the current regions we observe currently.  To get a burst would require one of two things.  1) that a collapse of near-shore basin occur such that vast amounts of clathrate become directly exposed to warmer sea water  or 2) that by some means, sufficient quantity of methane would be trapped by overlying sediments at depth that the eventual failure would act much like a volcanic eruption. 

I do not think either event is even low probability.  I'm not aware of any instability by which the ESS coastal shelf could be forced by heating into a slide, and mechanically, the conditions to trap a massive methane release would be difficult to create.

[Shared Humanity]

It certainly seems unlikely that increased levels of methane released into the atmosphere by the slow degradation of frozen soils underwater would trigger a sudden burst of methane. Could this sudden burst be triggered, instead, by the physical changes in the  sea floor that are causing slow  increases of methane in the East Siberian Sea?

Melting permafrost on land results in the creation of karsts and these depressions and resulting drainage accelerate the deterioration  of the surrounding permafrost. Could a similar mechanism work in the East Siberian Sea? Is it really necessary for the water temperature to increase in order for there to be a burst of methane?

I think the effect would still be localized, much like the current regions we observe currently.  To get a burst would require one of two things.  1) that a collapse of near-shore basin occur such that vast amounts of clathrate become directly exposed to warmer sea water  or 2) that by some means, sufficient quantity of methane would be trapped by overlying sediments at depth that the eventual failure would act much like a volcanic eruption. 

I do not think either event is even low probability.  I'm not aware of any instability by which the ESS coastal shelf could be forced by heating into a slide, and mechanically, the conditions to trap a massive methane release would be difficult to create.

Thanks for the answer. It makes sense. The formation of karsts or release points in the East Siberian Sea, I guess, would only cause an acceleration near the original release. This would likely result in an exponential trend upwards of methane releases but this would not be seen as a burst but merely an acceleration, a doubling of the amount released per unit of time.

Given the relative stability of sea temperatures vs. atmosphere, couldn't this exponential growth that we are, possibly, already seeing be very difficult to slow or reverse? In other words, is it possible that an established exponential growth trend, if in place, would ultimately release all of the trapped clathrates over time?

[AbruptSLR]

Back to Candles' original topic of identifying feedback factors associated with ASI:

(a) A positive feedback is that reduced sea ice area warms the surrounding Arctic land masses which both increases shrub growth (which reduces albedo) and accelerates permafrost degradation (which increases both CO2 and CH4 emissions).
(b) The classic "Warm Arctic Cold Continent" theory predicts that as the Arctic warms the North American, European and Asian continents will have colder winters; which has been the case since at least 2000; and as stated earlier in this thread early snowfall on these continents reduces freezing depth of the ground, resulting in earlier melting of the Spring snow resulting in reduced albedo, resulting in a positive feedback.  Furthermore, colder NH winters means more anthropogenic burning of fossil fuels (coal, etc), which can mean more Black Carbon; again a positive feedback.
(c) Melting of Arctic glaciers (Canada, Alaska, Greenland, Russia, Norway, Iceland) can promote local earthquakes that can result in more local marine methane emissions and low elevation volcanic emissions which can decrease local albedo; both positive feedbacks.
(d) It is my personal belief that the faster that the permafrost degrades (say due to rapid ASI loss) the more methane emissions will occur from the permafrost as the land will not have adequate time to drain (submerged degraded permafrost produces more methane than does dry degrading permafrost), which is a potential positive feedback factor depending on the rate of Arctic warming vs land drainage.
(e) Anthropogenic activity will increase in the Arctic as ASI decreases due to such activities as: shipping, mining, oil/gas extraction; which is a certain positive feedback factor.
(f) As local sea level increases (due to global warming), many local areas of coastal tundra will be inundated by seawater; which will increase permafrost degradation and which might decrease local albedo; both positive feedbacks.
(g) With a decrease in ASI it is projected that the North Atlantic currents will penetrate further and further into the Arctic Ocean, which is a very strong positive feedback.
(h) Increasingly frequency (due to global warming) of large Atlantic hurricanes will telecommute more atmospheric energy into the Arctic; which is a clear positive feedback.
(i) Decreasing ASI can increase Arctic cyclonic activity which can increase ocean mixing resulting in more marine methane emissions (as mentioned previously).

Lastly, I would like to note that due to the interactions of such positive feedbacks the resulting increases in Arctic temperatures can be highly non-linear (i.e. the classic "Arctic Amplification" effect that is well documented in GCM projections and in the paleo-record).
 

[AbruptSLR]

Some other Arctic feedback mechanisms that I omitted in my prior post include:

•  The weather phenomenon known as Arctic Dipoles, was unknown before the 1990's and has caused a drastic decrease in the volume of Arctic multi-year ice, as has more frequent atypically strong Arctic Oscillations.  As multi-year ice helps to stabilize the entire Arctic Ice Cap, this reduction in multi-year ice is serving to accelerate the total reduction of Arctic sea ice volume and extent.
•  First year Arctic sea ice is more saline and thus denser than multi-year sea ice.  When it melts the 0oC melt water sinks and causes upwelling of warmer water from the depths of the Arctic Ocean to be directly beneath the sea ice.
•  Potential increase in the frequency of strongly negative Arctic Oscillations, AO, in the summer months, resulting in more Arctic Ice melting from solar irradiance due to reduced cloud cover.
•   Increased frequency of summer rain, and decreased frequency of summer snow in the Arctic, resulting in reduced reflection of sunlight and reduced insulation of both the Arctic sea ice and the Greenland ice sheet.
•  The continued warming of the ocean's upper layers results in: (a) increased melting of sea level glaciers; (b) increased melting of the Arctic sea ice from warm ocean currents entering the Arctic; and (c) reduced absorption of atmospheric CO2.
•   Loss of the Arctic sea ice volume, and associated loss of latent heat of melting, will eventually lead to an acceleration of the warming of the northern ocean water temperatures.

[AbruptSLR]

To clarify two issues on my two prior posts:

(a)  The "Warm Arctic Cold Continent" model does promote atmospheric telecommunication of heat into the Arctic; and
(b)  The increased humidity and increased precipitation in the northern latitudes should increase methane emissions from organic decomposition under freshwater lakes and rivers (ie northern wetland); which is a positive feedback factor.

[AbruptSLR]

Obviously, in my hurry I forgot to mention an increase in Arctic wildfires as a meaningful positive feedback factor.

[wili]

ASLR, thanks for the great lists and commentary!

jd, thanks for the careful notes. Very interesting stuff about how this connects to your earlier research!

I would just point out that none of us (I presume) and few in the world have been down in the seabed of the ESAS, so it's hard to say exactly what is down there. That cuts either way--it could be even more stable than the folks that are saying it is stable presume. But it could have a lot of meta-stable, close-to-the-surface methane hydrates of the sort that has been seen and studies in some terrestrial contexts (see recent interesting discussion at RC).

There could be all sorts of events that free deeper methane deposits suddenly, including seismic activity (possibly triggered by SLR/collapsing coastlines??).

There are also variations in depth of various sorts. What concerns me the most are areas near slopes where the hydrates meet the ocean floor. I know that according to standard tables this should be hundreds of meters under sea level. But shifts in currents, warmer river water, changes in salinity...could all effect the release of these, and that could potentially trigger slope failures releasing ever more, it seems to me. But obviously this is far outside my expertise and experience.

[AbruptSLR]

While the increasing Global Warming Potential, GWP, of methane with decreasing atmospheric hydroxyl ions is not a positive feedback strictly limited to the Arctic; nevertheless, over on RealClimate I posted the following information indicating how research from the list of references at the bottom of the post support the idea that for high methane emission scenarios, the GWP of methane could increase from its current value of 34 (over 100 years) to 50 (over 100 years) by as early as 2060:

"Isaken et al (2011) quantify how as atmospheric methane concentrations increase, the global warming potential, GWP, of methane also increases (see references at end of post).   Also note that any source increasing atmospheric methane concentrations, increase the GPW of all previously emitted methane remaining in the atmosphere.  As an example of the possible extreme change in radiative forcing in a 50-year time horizon for Isaken et al (2011)'s 4 x CH4 (i.e. quadrupling the current atmospheric methane burden) case of additional emission of 0.80 GtCH4/yr is 2.2 Wm-2, and as the radiative forcing for the current methane emissions of 0.54 GtCH4/yr is 0.48 Wm-2, this give an updated GWP for methane, assuming the occurrence of Isaksen et al's 4 x CH4 case in 2040, would be: 33 (per Shindell et al 2009, note that AR5 gives a value of 34) times (2.2/[0.8 + 0.48]) divided by (0.54/0.48) = 50.

As NOAA's Mauna Loa measurement of atmospheric methane concentrations are only currently increasing at a rate of approximately 0.25% per year (or 12.5% change in 50-years); how could anyone be concerned that the change in atmospheric methane burden in 50-years could be 300% (as per Isaken et al (2011) case 4XCH4; which would require an additional 0.80 GtCH4/yr of methane emissions on top of the current rate of methane emissions of 0.54 GtCH4/yr)?
At the high CL scenarios, I note the following possible additional sources (beyond or current emissions, and see list of references at the end of this post):

• RCP 8.5 50%CL (which does not consider such possible methane sources as the ESAS, the permafrost or from shale gas) assumes an approximately doubling (Meinshausen et.al. 2011) of the present atmospheric methane burden by 2100, or a 50% increase fifty years primarily due to increase emissions from northern wetlands (see Bastviken et al 2011) and conventional anthropogenic sources.
•  Methane emissions from permafrost degradation (see Schuur and Abbott (2011)).
•  The Clathrate Gun Hypothesis postulated that methane hydrates can be destabilized due to geotechnical slope failures on the various continental slopes around the Arctic Ocean; which might take decades rather than millennia to accumulate meaningful methane emissions.
•  Anthropogenic methane leaks associated with the development of international hydrofracking operations (including significantly that from China) will likely exceed the comparable leaks from USA hydrofracking operations, within one decade.
•  The methanetrack.org website has shown significant increases in atmospheric methane concentrations over Antarctica this austral winter (which I believe are due to increases in methane emissions from the Southern Ocean seafloor due to increases in the temperature of bottom water temperatures), and if this trend continues, then the Southern Hemisphere could be a significant source of additional atmospheric methane (this century).
•  Similarly, Eillott et al (2011), Reagan (2011) and Reagan and Moridis (2008), for the equivalent of RCP 8.5 50% CL methane emissions from global marine methane hydrates could be 0.3 GtCH4/yr by 2100.
•  Significantly, the East Siberian Arctic Shelf, ESAS, has up to 1000 Gt of methane reserves, and it is highly believable that 1% of this (or up to 10 Gt) is in the form of free gas trapped underneath the currently degrading subsea permafrost cap, which could be released within the next few decades by a combination of increasing Arctic Ocean water temperatures, increased storm activity, and possible increases in seismic activity.


Bastviken, D., Tranvik, L.J., Downing, J.A., Crill, P.M., and Enrich-Prast, A. (2011), "Freshwater Methane Emissions Offset the Continental Carbon Sink", Science, Vol 331, pp. 50.

Elliott, S., Maltrud, M., Reagan, M., Moridis, G., and Cameron-Smith, P., "Marine methane cycle simulations for the period of early global warming", Journal of Geophysical Research, Vol. 116, G01010, doi: 10.1029/2010JG00 1300, 2011.

Isaksen, I. S. A., Gauss M., Myhre, G., Walter Anthony, K. M.  and Ruppel, C.,  (2011), "Strong atmospheric chemistry feedback to climate warming from Arctic methane emissions", Global Biogeochem. Cycles, 25, GB2002, doi:10.1029/2010GB003845. (see: http://onlinelibrary.wiley.com/doi/10.1029/2010GB003845/abstract)

Meinshausen, M., Smith, S.J., Calvin, K., Daniel, J.S., Kainuma, M.L.T., Lamarque, J-F., Matsumoto, K., Montzka, S.A., Raper, S.C.B., Riahi, K., Thomson, A., Velders, G.J.M., and van Vuuren, D.P.P., (2011); "The RCP greenhouse gas concentrations and their extensions from 1765 to 2300", Climatic Change, 109:213-241, doi: 10.1007/s10584-011 -0156-z.

Reagan, M.T. (PI), (2011), Interrelation of Global Climate and the Response of Oceanic Hydrate Accumulations, Lawrence Berkeley Laboratory: Task Report 10-1, January 31, 2011.

Reagan, M.T., and Moridis, G.J. (2008), "Dynamic response of oceanic hydrate deposits to ocean temperature change", J. Geophys. Res., 113, 107, 486-513, doi: 10.1029/2008JC004938.

Schuur, E.A.G. and Abbott, B., (2011), "High risk of permafrost thaw", Nature, 480, 32-33, Dec. 2011."

[wili]

Thanks again, ASLR.

The second figure in this article illustrates what I was trying to get at above, with methane escaping from the "upper edge of the stability zone" and a lot more methane beneath it that may come up once pressure is from the top level.


http://www.nature.com/scitable/knowledge/library/methane-hydrates-and-contemporary-climate-change-24314790

There is also a question about whether surface water might be drawn down toward the ocean bottom as the methane rushes upward. Whether disruptions from permafrost and methane hydrate destabilization might also release pools of thermogenic free methane seems to me to be an open question, too.

The last image in this piece illustrates how slope collapse can result from methane release:

http://www.nature.com/scitable/knowledge/library/methane-hydrates-and-contemporary-climate-change-24314790

https://www.google.com/search?q=methane+hydrates&client=firefox-a&hs=DLy&rls=org.mozilla:en-US:official&tbm=isch&tbo=u&source=univ&sa=X&ei=AgudUq67Bc_eyQG-nIC4AQ&ved=0CEQQsAQ&biw=1374&bih=748#facrc=_&imgdii=_&imgrc=SsHAeBksxPpWbM%3A%3B1x1yS-EvnUnYMM%3Bhttp%253A%252F%252Fwww.climate-change-knowledge.org%252Fuploads%252FUSGS.jpg%3Bhttp%253A%252F%252Fwww.climate-change-knowledge.org%252Fimages.html%3B585%3B434

I can't find the source right now, but I have read claims that there could be a 'zipper' effect, where collapse of one part of the slope triggers collapse further along the slope, that causes collapse further up, etc.

[Andreas T]

I have read suggestions that downward heat transfer from warmer water could be increased by localized methan escapes. I find it difficult to see mechanisms for that. Ok, rising bubbles can drag cold water up with them and increase mixing, but depending on the stratification of the water above I would not expect it to change water temperature at the sea floor to change very much and rather over a wider area than at the source of the methane.
Sea water has its density maximum at its temperature minimum unlike fresh water which has a density maximum at about 4deg C. This creates convection in meltlakes and thermocarst lakes which transfer heat from the surface to the bottom, in saltwater this convection does not exist.
I.e. on land there are feedback mechanisms which deepen the uneven heattransfer, which on the seafloor don't.

[AbruptSLR]

The linked article focuses on changes in the Arctic Ocean, and indicates that changes in the plankton there could result in a positive feedback (that will likely become more important with time) associated both with lower dimethyl sulphide production and lower CO2 absorption: 

http://www.egu.eu/news/76/tiny-plankton-could-have-big-impact-on-climate/

This article states:

""If the tiny plankton blooms, it consumes the nutrients that are normally also available to larger plankton species,” explains Ulf Riebesell, a professor of biological oceanography at the GEOMAR Helmholtz Centre for Ocean Research Kiel in Germany and head of the experimental team. This could mean the larger plankton run short of food.

Large plankton play an important role in carbon export to the deep ocean, but in a system dominated by the so-called pico- and nanoplankton, less carbon is transported out of surface waters. “This may cause the oceans to absorb less CO2 in the future,” says Riebesell.

The potential imbalance in the plankton food web may have an even bigger climate impact. Large plankton are also important producers of a climate-cooling gas called dimethyl sulphide, which stimulates cloud-formation over the oceans. Less dimethyl sulphide means more sunlight reaches the Earth’s surface, adding to the greenhouse effect. “These important services of the ocean may thus be significantly affected by acidification.”

Ecosystems in the Arctic are some of the most vulnerable to acidification because the cold temperatures here mean that the ocean absorbs more carbon dioxide. “Acidification is faster there than in temperate or tropical regions,” explains the coordinator of the European Project on Ocean Acidification (EPOCA), Jean-Pierre Gattuso of the Laboratory of Oceanography of Villefranche-sur-Mer of the French National Centre for Scientific Research (CNRS).

The increasing acidity is known to affect some calcifying organisms in the Arctic, including certain sea snails, mussels and other molluscs. But scientists did not know until now how ocean acidification alters both the base of the marine food web and carbon transport in the ocean. ..."


Furthermore, this article points to the free pdfs available on this topic from the following special issue of Biogenosciences

http://www.biogeosciences.net/special_issue120.html

[Bruce Steele]

AbruptSLR, Acidification and heating have several mechanisms that reduce the efficiency of the carbon  pump. A decrease in diatoms as a result of competition with nano and picophytoplankton  for nutrients is a new finding. This results in less carbon being moved from the surface to depth because diatoms form shell that ballasts organic matter and carries it down.  Heating of seawater is the largest positive feedback because cold water will hold more Co2 than warm water. Both of these will lead to more Co2 staying in the atmosphere due to a reduction the partial pressure differential  that the carbon pump provides.  Geoff Beacon was making a list of feedbacks and the nutrient competition made it in letter he sent to policy makers.
   Geoff, This study shows potential negative impacts to the biological pump at elevated Co2.
Nov.24 # 28   "Science" page "A list of missing feedbacks"

" The impact of Co2 enhanced nutrient utilization by pico- and nanophytoplankton growth at the expense of diatoms on biogeochemical cycling was visible in sedimentation fluxes, which were lower at elevated pCo2."

[Bruce Steele]

AbruptSLR, Could you do me a favor and post the chart on page 8 of this report. Chart of feedbacks from ocean acidification.

 http://www.mccip.org.uk/media/13199/2013arc_backingpapers_5_ocac.pdf

[wili]

As I understand it, the ocean is still catching up to absorbing the higher concentration of atmospheric CO2, so it can still acidify quite a bit before become a net contributor. And as atmospheric concentrations go up, it will take even longer to reach equilibrium.

Of course, that is just looking at one effect. When you add in warming and the biological effects noted above, we could be much closer to the ocean moving from a source to a sink, imho.

The other thing about the ocean absorbing so much CO2 directly is that it means that if atmospheric levels ever do start to go down, the ocean will then definitely become a source of CO2 and will slowly feed back into the system most of the CO2 it has been absorbing, keeping atmospheric levels from dropping as fast as they would otherwise. (At least, that's what my weary mind understands of the process--happy for any corrections or refinements, though.)

[Bruce Steele]

Wili, There are two processes that carry carbon from the surface to depth, physical mixing (those polynya that feed bottom water formation or ocean conveyer processes)and the carbon pump. Biological production of shell ( which counterintuitively causes acidification at the surface)  provides a mechanism to move surface water Co2 to depth via ballasting. This process will always provide a partial pressure differential between the surface and depth. The only point where this process would completely end is if all calcite or aragonite formation were to fail. ( Not Going To Happen ) 
 Both ballasting and physical mixing carry inorganic and organic carbon to depth . Both of those processes feed into the 37,000 Gt carbon dissolved in the deep oceans. That deep water carbon can upwell back to the surface where it can ventilate back into the atmosphere, mostly along the western equatorial pacific.
 The processes that move the deep water around the world and back to the surface along the western equatorial pacific are slow(~1000 years) so I wouldn't expect any big changes any time soon. The biological processes that drive the carbon pump are under stress and likely to be less effective as we continue to increase atmospheric Co2 levels.  So the physical processes that bring intermediate and deep water( with high pCo2) to the surface will have to overcome the biological and physical processes that take it down. Temperature will play a large role but we are only expecting a 2-3 degree increase in world ocean temperature averages by 2100. 
 So with the caveat ,I am a fisherman not a modeler, we are sometime into the 22nd century before this comes home to roost.     

 

[wili]

Thanks for the specifics, Bruce.

On your last point, though: A few recent articles I've seen suggest that 4 degrees C is now the mid-range number for estimations of end-of-century temperature (though, presumably, it will be cooler over the oceans than over land, at least for a good while).

http://www.abc.net.au/worldtoday/content/2013/s3903815.htm

http://www.climatecodered.org/2013/11/parts-of-australia-reaching-threshold.html

NASA, Tyndall, IEA, PCW, and a number of others are more in the neighborhood of 6 degrees C by about the turn of the century. 

[AbruptSLR]

Here is the table that Bruce Steele wanted me to post of a summary of future effects of ocean acidification.  However, I would like to note that this table states that the impact of the reduction of dimethyl sulfide maybe low; I would like to say while this positive impact may be uncertain, there is growing concern that this impact could be meaningful (see "Tiny Plants That Once Ruled the Seas" by Ronald Martin and Antonietta Quigg; Scientific American, June 2013, page 45).

[Bruce Steele]

AbruptSLR, The chart acknowledges a low level of understanding in some of the effects/feedbacks. Some of the feedbacks with large ve+ have some good confidence however. The negative effects on ballasting is fairly new research also so O/A effects on the carbon pump isn't settled.
Thanks

[Bruce Steele]

Wili, in my first post on the carbon cycle page Bopp et al 2013 has a projected average sea surface temperature increase at 2.73 degrees C from 1990 averages. R8.5.     
 I watched what happened to the local fauna while diving through both the 82-83 and 97-98 ENSO events. 2.73C above what happened 97-98would kill a lot of inverts. Lots.  Averages are just that so local temperature extremes might fluctuate quite a bit from that average. So 3 or 4C degree spikes would leave our local temperate reefs scalded. Hard to describe what happens when the normally pink and purple crustose coralline algae turns white and the color drains out of the bottom.

[wili]

I posted this on another thread, but it's really more appropriate here:

http://www.bbc.co.uk/nature/15835017

Storing carbon in the Arctic

researchers at MIT have found that with the loss of sea ice, the Arctic Ocean is becoming more of a carbon sink. The team modeled changes in Arctic sea ice, temperatures, currents, and flow of carbon from 1996 to 2007, and found that the amount of carbon taken up by the Arctic increased by 1 megaton each year.

But the group also observed a somewhat paradoxical effect: A few Arctic regions where waters were warmest were actually less able to store carbon. Instead, these regions—such as the Barents Sea, near Greenland—were a carbon source, emitting carbon dioxide to the atmosphere.

While the Arctic Ocean as a whole remains a carbon sink, MIT principal research scientist Stephanie Dutkiewicz says places like the Barents Sea paint a more complex picture of how the Arctic is changing with global warming.

"People have suggested that the Arctic is having higher productivity, and therefore higher uptake of carbon," Dutkiewicz says. "What's nice about this study is, it says that's not the whole story. We've begun to pull apart the actual bits and pieces that are going on."...

Manizza found a discrepancy between 2005 and 2007, the most severe periods of sea ice shrinkage. While the Arctic lost more ice cover in 2007 than in 2005, less carbon was taken up by the ocean in 2007—an unexpected finding, in light of the theory that less sea ice leads to more carbon stored...

In short, while the Arctic Ocean as a whole seems to be storing more carbon than in previous years, the increase in the carbon sink may not be as large as scientists had previously thought.

[AbruptSLR]

I posted the following in the Antarctic folder at the following link; however, I thought that it also belonged here:
http://forum.arctic-sea-ice.net/index.php/topic,41.250.html


The linked reference (with a free access pdf) provides evidence that the main source of uncertainty for Arctic climate variability, and its predictability, is the North Pacific.  As we know (see references at end of post) that the North Pacific is projected to warm-up over the next 25 years in order to synchronize with the North Atlantic, it seems likely that we can expect the Arctic to warm rapidly as the North Pacific warms:

Dmitry V. Sein, Nikolay V. Koldunov, Joaquim G. Pinto, William Cabos, (2014), "Sensitivity of simulated regional Arctic climate to the choice of coupled model domain", Tellus A, 66, 23966, http://dx.doi.org/10.3402/tellusa.v66.23966

http://www.tellusa.net/index.php/tellusa/article/view/23966


Abstract: "The climate over the Arctic has undergone changes in recent decades. In order to evaluate the coupled response of the Arctic system to external and internal forcing, our study focuses on the estimation of regional climate variability and its dependence on large-scale atmospheric and regional ocean circulations. A global ocean–sea ice model with regionally high horizontal resolution is coupled to an atmospheric regional model and global terrestrial hydrology model. This way of coupling divides the global ocean model setup into two different domains: one coupled, where the ocean and the atmosphere are interacting, and one uncoupled, where the ocean model is driven by prescribed atmospheric forcing and runs in a so-called stand-alone mode. Therefore, selecting a specific area for the regional atmosphere implies that the ocean–atmosphere system can develop ‘freely’ in that area, whereas for the rest of the global ocean, the circulation is driven by prescribed atmospheric forcing without any feedbacks. Five different coupled setups are chosen for ensemble simulations. The choice of the coupled domains was done to estimate the influences of the Subtropical Atlantic, Eurasian and North Pacific regions on northern North Atlantic and Arctic climate. Our simulations show that the regional coupled ocean–atmosphere model is sensitive to the choice of the modelled area. The different model configurations reproduce differently both the mean climate and its variability. Only two out of five model setups were able to reproduce the Arctic climate as observed under recent climate conditions (ERA-40 Reanalysis). Evidence is found that the main source of uncertainty for Arctic climate variability and its predictability is the North Pacific. The prescription of North Pacific conditions in the regional model leads to significant correlation with observations, even if the whole North Atlantic is within the coupled model domain. However, the inclusion of the North Pacific area into the coupled system drastically changes the Arctic climate variability to a point where the Arctic Oscillation becomes an ‘internal mode’ of variability and correlations of year-to-year variability with observational data vanish. In line with previous studies, our simulations provide evidence that Arctic sea ice export is mainly due to ‘internal variability’ within the Arctic region. We conclude that the choice of model domains should be based on physical knowledge of the atmospheric and oceanic processes and not on ‘geographic’ reasons. This is particularly the case for areas like the Arctic, which has very complex feedbacks between components of the regional climate system."

See also:

McGregor, S., A. Timmermann, M. F. Stuecker, M. H. England, M. Merrifield, F.-F. Jin and Y. Chikamoto, (2014), "Recent Walker circulation strengthening and Pacific cooling amplified by Atlantic warming", Nature Climate Change; doi:10.1038/nclimate2330

Summer K. Praetorius, Alan C. Mix, (2014), "Synchronization of North Pacific and Greenland climates preceded abrupt deglacial warming", Science 25 July 2014: Vol. 345 no. 6195 pp. 444-448 DOI: 10.1126/science.1252000

Seon Tae Kim, Wenju Cai, Fei-Fei Jin, Agus Santoso, Lixin Wu, Eric Guilyardi & Soon-Il An, (2014), "Response of El Niño sea surface temperature variability to greenhouse warming", Nature Climate Change, doi:10.1038/nclimate2326

[ChrisReynolds]

Forgot to mention, Science of Doom is an excellent blog dedicated to climate science, especially the atmospheric science. Look at the series "CO2" and "Atmospheric Radiation and the Greenhouse Effect".

Science of Doom did a twelve part blog post on the GH effect.
http://scienceofdoom.com/roadmap/atmospheric-radiation-and-the-greenhouse-effect/

Must re-read that sometime.

[AbruptSLR]

The referenced theory links Arctic amplification with La Nina-like events:

Sukyoung Lee, (2014), "A theory for polar amplification from a general circulation perspective", Asia-Pacific Journal of Atmospheric Sciences, Volume 50, Issue 1, pp 31-43, DOI: 10.1007/s13143-014-0024-7


http://link.springer.com/article/10.1007%2Fs13143-014-0024-7

Abstract: "Records of the past climates show a wide range of values of the equator-to-pole temperature gradient, with an apparent universal relationship between the temperature gradient and the global mean temperature: relative to a reference climate, if the global-mean temperature is higher (lower), the greatest warming (cooling) occurs at the polar regions. This phenomenon is known as polar amplification. Understanding this equator-to-pole temperature gradient is fundamental to climate and general circulation, yet there is no established theory from a perspective of the general circulation. Here, a general circulation-based theory for polar amplification is presented.  Recognizing the fact that most of the available potential energy (APE) in the atmosphere is untapped, this theory invokes that La-Niña-like tropical heating can help tap APE and warm the Arctic by exciting poleward and upward propagating Rossby waves."

[AbruptSLR]

Regarding my last post (that Lee 2014 shows that Arctic amplification can be linked to La Nina-like events), I note that the two attached images show that the first (2012), second (2011) and third (2007) lowest Arctic Sea Ice Extents (see the first image) all occurred in La Nina years (see  the second image).  I seriously doubt that this is the only feedback factor influencing ASIE as I believe that a coming warm phase of the PDO will push warm water through the Bering Strait to melt Arctic Sea Ice even during future strong El Nino event; nevertheless, the ability of La Nina-like event to activate available potential energy (APE) in the atmosphere appears to be a real consideration:

[AbruptSLR]

While a few years old, the first attached image shows a projection from an Earth Systems Model run at Lawrence Berkeley Labs of the change in Arctic Sea Floor temperatures between 2000 and 2100 for SRES A1B, indicating substantial warming particularly in the East Siberian Arctic Shelf, ESAS.
Furthermore, the second attached image indicates how under conditions with a high positive Arctic Oscillation (AO) index (which is positive about ½ the time), the Arctic Ocean circulation patterns transport relatively warm Atlantic Ocean water directly to the ESAS, thus promoting the degradation of the underwater permafrost in this area, contributing to the accelerated emission of methane from the seafloor
With these two images as background, the following linked reference addresses both the current, and future, situation in the West Yamal continental shelf with regards to degradation of the local subsea permafrost (and these findings will be relevant to the ESAS within two to three decades).  The Portnov et al 2014 paper shows that in the West Yamal shelf area the relict subsea permafrost (which traps methane gas beneath it and also stabilizes methane hydrates beneath it) are already degrading to the point of leaking methane gas in the 20 to 50 meter water depth range, and the reference notes that model projections indicates that in the next few decades the ocean water temperature at the seafloor in this area should increase from about 0.5 C to about 2.5 C, which should result in a rapid acceleration of the degradation of this relic subsea permafrost.  If indeed, the relict subsea permafrost in the Russian Arctic shelves degrade rapidly due to the introduction of warm ocean currents along the seafloor from the North Atlantic Current, within the next few decades then the world could experience a very large positive feedback, first from the associated release of free methane gas from beneath the previously impermeable permafrost and second from the destabilization of the methane hydrates that were kept in a quasi-stable condition since the last ice age due to the melting of the degrading permafrost keeping the hydrates in a transient low temperature condition.

Portnov, A., J. Mienert, and P. Serov (2014), Modeling the evolution of climate-sensitive Arctic subsea permafrost in regions of extensive gas expulsion at the West Yamal shelf, J. Geophys. Res. Biogeosci., 119, 2082–2094, doi:10.1002/2014JG002685.

http://onlinelibrary.wiley.com/doi/10.1002/2014JG002685/abstract

Abstract: "Thawing subsea permafrost controls methane release from the Russian Arctic shelf having a considerable impact on the climate-sensitive Arctic environment. Expulsions of methane from shallow Russian Arctic shelf areas may continue to rise in response to intense degradation of relict subsea permafrost. Here we show modeling of the permafrost evolution from the Late Pleistocene to present time at the West Yamal shelf. Modeling results suggest a highly dynamic permafrost system that directly responds to even minor variations of lower and upper boundary conditions, e.g., geothermal heat flux from below and/or bottom water temperature changes from above permafrost. Scenarios of permafrost evolution show a potentially nearest landward modern extent of the permafrost at the West Yamal shelf limited by ~17 m isobaths, whereas its farthest seaward extent coincides with ~100 m isobaths. The model also predicts seaward tapering of relict permafrost with a maximal thickness of 275–390 m near the shoreline. Previous field observations detected extensive emissions of free gas into the water column at the transition zone between today's shallow water permafrost (<20 m) and deeper water nonpermafrost areas (>20 m). The model adapts well to corresponding heat flux and ocean temperature data, providing crucial information about the modern permafrost conditions. It shows current locations of upper and lower permafrost boundaries and evidences for possible release of methane from the seabed to the hydrosphere in a warming Arctic."

Also see:
http://phys.org/news/2014-12-methane-leaking-permafrost-offshore-siberia.html

Extract: "Portnov used mathematical models to map the evolution of the permafrost, and thus calculate its degradation since the end of the last ice age. The evolution of permafrost gives indication to what may happen to it in the future.
If the bottom ocean temperature is 0,5°C, the maximal possible permafrost thickness would likely take 9000 years to thaw. But if this temperature increases, the process would go much faster, because the thawing also happens from the top down.
"If the temperature of the oceans increases by two degrees as suggested by some reports, it will accelerate the thawing to the extreme. A warming climate could lead to an explosive gas release from the shallow areas."
Permafrost keeps the free methane gas in the sediments. But it also stabilizes gas hydrates, ice-like structures that usually need high pressure and low temperature to form.
"Gas hydrates normally form in water depths over 300 meters, because they depend on high pressure. But under permafrost the gas hydrate may stay stable even where the pressure is not that high, because of the constantly low temperatures."
Gas hydrates contain huge amount of methane gas, and it is destabilization of these that is believed to have caused the craters on the Yamal Peninsula."

[AbruptSLR]

While paleo evidence is not proof of future possible developments, nevertheless, to elaborate on my immediate past post, in Reply #148 of the Paleo thread in the Antarctic folder (see the following link), recent evidence indicates that the PETM had two episodes of carbon emissions into the atmosphere, the first one likely being the trigger event (such as volcanic action) and the second one likely being methane emissions from hydrates in the seafloor (& most likely from the Arctic Ocean seafloor).

http://forum.arctic-sea-ice.net/index.php/topic,130.100.html#lastPost

If history repeats itself, it will be a sad commentary on human hubris.