Support the Arctic Sea Ice Forum and Blog

Author Topic: "Smart" and "Stupid" Questions - Feel Free To Ask  (Read 1031643 times)

Peter Ellis

  • Grease ice
  • Posts: 619
    • View Profile
  • Liked: 33
  • Likes Given: 14
Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« Reply #250 on: August 07, 2014, 07:04:06 PM »
No they do not, especially deeper down at the start of their rise, since they have a small surface area to volume ratio, rise comparatively slowly and thus readily equilibrate in temperature with the surrounding water, i.e. the bubble expansion will thus be largely isothermal.

Edit: removed scuba diving example as it's not just wrong but hilariously wrong

If the bubbles are large and also rise really fast over the last few metres, you might see gas escaping at fractionally below the water temperature. I don't think it would be easily measureable.
« Last Edit: August 07, 2014, 10:01:02 PM by Peter Ellis »

johnm33

  • Guest
Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« Reply #251 on: August 07, 2014, 08:46:53 PM »
Thanks for the replies, I was thinking of its cooling effect under the ice but of the larger surface eruptions, say 50-100m,  [or even up to 1000m] where I'm assuming, for now, that there'd be less opportunity to establish equilibrium with the water it rises through.

anthropocene

  • Frazil ice
  • Posts: 128
    • View Profile
  • Liked: 37
  • Likes Given: 2
Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« Reply #252 on: September 06, 2014, 08:53:12 AM »
Could somebody with in-depth knowledge answer the following questions. A link to a resource which provides information about arctic atmospheric conditions would be great.
I've recently been taking a course on meteorology.  This introduced me to the ideas of lapse rate and temperature inversions (positive lapse rate) producing a stable atmospheric layer. The example given was on land at night time when the land cools the surface atmosphere producing a stable atmospheric layer (I think it was stated this layer was typically 100-200m thick). This stable layer stops higher level winds reaching ground level and reduces atmospheric mixing (and therefore temperature transfer). This got me to thinking about what happens in the arctic  above the sea ice. For this case lets concentrate on 80degN and above.

1) Because the ice provides a constant cooling force the default state is for there to be a temperature inversion from the ice surface to 100 to 200m altitude?

2) In summer the sun will heat the surface but most of the heat will be reflected. Does the heating from the sun ever get strong enough to destroy the temperature inversion (i.e. set up thermal convection currents at the surface)?

3) Obviously if the sea is ice-free for a significant area then the thermal dynamics will be completely different. Convection will occur and higher altitude winds will transfer to the surface. What happens when these surface winds hit the areas with ice and the stable atmospheric regions? e.g. This air will be warmer so does it rise and ride over the stable air mass or does it push the stable air mass off the ice?

4) During the melting season  temperature maps are often provided. The map shows temperature at a certain pressure which often translates to a certain altitude (I think I remember 500m being mentioned). The assumption seems to be that the temperature at the surface will be higher than this temperature (negative lapse rate is being assumed). If 1) is correct isn't this assumption likely to be incorrect above the sea-ice?

Richard Rathbone

  • Nilas ice
  • Posts: 1730
    • View Profile
  • Liked: 387
  • Likes Given: 24
Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« Reply #253 on: September 07, 2014, 12:38:05 PM »
Thanks for the replies, I was thinking of its cooling effect under the ice but of the larger surface eruptions, say 50-100m,  [or even up to 1000m] where I'm assuming, for now, that there'd be less opportunity to establish equilibrium with the water it rises through.

These aren't bubble sizes. These are the size of areas within which bubbles were seen.

To use a football analogy, what you are quoting here is the size of the pitch, not the size of the ball.

Mike H

  • New ice
  • Posts: 1
    • View Profile
  • Liked: 0
  • Likes Given: 0
Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« Reply #254 on: September 10, 2014, 11:26:58 PM »
For years I have heard the proposition that the disappearance of sea ice produces a significant positive feedback which will accelerate melting and global warming in general. I think I understand the mechanism. However, it has occurred to me that this feedback might be somewhat limited, as the timing of maximum solar insolation occurs much before the maximum amount of open water in the Arctic.

Also, the increase in open water in fall and early winter produces a negative feedback due to extra release of heat to space.

Has anybody tried to estimate the net effects of these two feedbacks ? That is, how much extra ice volume should be lost in spring/summer due to reduced ice area of say, 1 million km2 between 70-80 N ? And how much extra ice volume should be gained due to a similar decrease of ice area during fall/early winter ?

I have tried to follow the math of various forcings but find myself overwhelmed, given that short-term noise (wind and ocean currents, other effects of weather) tend to dominate the action in any given year.

jdallen

  • Young ice
  • Posts: 3410
    • View Profile
  • Liked: 650
  • Likes Given: 244
Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« Reply #255 on: September 11, 2014, 01:10:11 AM »
For years I have heard the proposition that the disappearance of sea ice produces a significant positive feedback which will accelerate melting and global warming in general. I think I understand the mechanism. However, it has occurred to me that this feedback might be somewhat limited, as the timing of maximum solar insolation occurs much before the maximum amount of open water in the Arctic.

Also, the increase in open water in fall and early winter produces a negative feedback due to extra release of heat to space.

Has anybody tried to estimate the net effects of these two feedbacks ? That is, how much extra ice volume should be lost in spring/summer due to reduced ice area of say, 1 million km2 between 70-80 N ? And how much extra ice volume should be gained due to a similar decrease of ice area during fall/early winter ?

I have tried to follow the math of various forcings but find myself overwhelmed, given that short-term noise (wind and ocean currents, other effects of weather) tend to dominate the action in any given year.
This is far from a stupid question ;)

I haven't wrestled with the details of math, instead trying to understand processes.

I no longer think we are on a short path to a *persistently* ice free arctic  I do think over the last decade we have reached a change in hysteresis such that 1) return to pre 2007, perhaps even pre 2000 behavior is not possible for centuries, if ever and 2) short term forcings of weather will have a fair greater role in the state of the ice at the end of any given melt season. My sense right now is, the entire system has been thrown into a state which is to chaotic for us to skillfully predict behavior past a rather short event horizon; a distance measured months at most, weeks more probably.

I'm focusing  now less on the specific state of the ice, and more on the changes in sensible heat in the arctic ocean, and the condition of permafrost around it.  That heat and how accessible it is seasonally will I hope give me a better handle on how the climate is going to change, and how fast.

This space for Rent.

johnm33

  • Guest
Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« Reply #256 on: September 11, 2014, 02:22:00 AM »
Richard, this http://www.theage.com.au/articles/2003/10/22/1066631498889.html is the best reference I can find about large scale eruptions of the kind I was thinking of, and I'm thinking more of a release of balloons over the pitch [to extend your analogy]. But thats not the question the question is about the physics of that scale of gas release, specifically the cooling effects as the expanding gas rises, especially if it rises to an ice covered surface.   

anthropocene

  • Frazil ice
  • Posts: 128
    • View Profile
  • Liked: 37
  • Likes Given: 2
Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« Reply #257 on: September 11, 2014, 09:27:41 PM »
For years I have heard the proposition that the disappearance of sea ice produces a significant positive feedback which will accelerate melting and global warming in general. I think I understand the mechanism. However, it has occurred to me that this feedback might be somewhat limited, as the timing of maximum solar insolation occurs much before the maximum amount of open water in the Arctic.

Also, the increase in open water in fall and early winter produces a negative feedback due to extra release of heat to space.

Has anybody tried to estimate the net effects of these two feedbacks ? That is, how much extra ice volume should be lost in spring/summer due to reduced ice area of say, 1 million km2 between 70-80 N ? And how much extra ice volume should be gained due to a similar decrease of ice area during fall/early winter ?

I have tried to follow the math of various forcings but find myself overwhelmed, given that short-term noise (wind and ocean currents, other effects of weather) tend to dominate the action in any given year.

There was a paper a few months back (sorry no link) which put the total effect of the reduction in albedo in the arctic (IIRC this was total reduction in snow cover, loss of sea ice and reduction in albedo of ica+snow) as 25% of the global effect of GHG added to the atmosphere in the last century. Off the top of my head the effect of GHG is approx 3.2W/m2 so albedo reduction would be increase of 0.8W/m2 when averaged across the whole globe. Of course the actual impact would be much greater if considering just the arctic: The area would be considerably less but in this analogy I can't remember how they handled solar insolation.

Sorry, for heat loss from open sea water I've no idea. I suspect it would be highly dependent on the amount of clouds.
 Most probably the key issue is that as the removal of ice moves closer to the north pole the increase in insolation will get less and the increase in heat loss to space will most probably accelerate. (the amount and type of clouds is the main variable which can complicate this scenario).  Combined together this will be a negative feedback as we move towards an ice free arctic.


Richard Rathbone

  • Nilas ice
  • Posts: 1730
    • View Profile
  • Liked: 387
  • Likes Given: 24
Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« Reply #258 on: September 12, 2014, 02:27:17 PM »
Richard, this http://www.theage.com.au/articles/2003/10/22/1066631498889.html is the best reference I can find about large scale eruptions of the kind I was thinking of, and I'm thinking more of a release of balloons over the pitch [to extend your analogy]. But thats not the question the question is about the physics of that scale of gas release, specifically the cooling effects as the expanding gas rises, especially if it rises to an ice covered surface.

The thermal capacity of the water in the wake is of the order of 1,000 (for a small spherical bubble) to 10,000 (for a large spherical cap bubble) times that of the bubble. If anything affects the surface, its the water brought up with the bubble. (just as in your linked story, its the wake that sinks the toy boat, not the bubble).

kingbum

  • New ice
  • Posts: 35
    • View Profile
  • Liked: 0
  • Likes Given: 0
Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« Reply #259 on: September 16, 2014, 02:54:45 AM »
I got plenty of stupid questions for everyone here.....let me start by saying I'm not a denier of AGW but I also don't accept it blindly provide me evidence and I will listen.....My big thing right now is with the increase in seismic activity we have had worldwide, specifically I'm talking about bardabunga in Iceland and how it seems to be following eerily the same eruption pattern Laki did in 1784....For those who aren't familiar with this read about the winter of 1784 about 6 million deaths in Europe were attributed to SO2 and other gases....which leads me to why I'm posting this question on this forum....given the reduction in TSI and the increase of both ice and SO2 in the atmosphere how can we logically assume that the ice cap in the arctic won't recover more.....just look at Antarctica and the record extent its at and near record area....all of that ice must produce an albedo effect and at what time does all this become like a domino effect? Its just something that's bugging me

jdallen

  • Young ice
  • Posts: 3410
    • View Profile
  • Liked: 650
  • Likes Given: 244
Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« Reply #260 on: September 16, 2014, 09:28:58 AM »

Welcome kingbum and thank you for your willingness to enter into dialog.

Let me take a number of items you list in turn.

...My big thing right now is with the increase in seismic activity we have had worldwide,

That's an illusion of sampling.  The world isn't having more earthquakes.  It's measuring more earthquakes because more seismographs are being installed in more places they've never been before.  If more earthquakes started happening on Iceland, in areas other than that where the volcano is erupting, it might be a reasonable to think there was some connection.

... how it seems to be following eerily the same eruption pattern Laki did in 1784...

That similarly is illusory.  We know rather little about Laki aside from its aftermath - the evidence left lying around after the eruption stopped.  There's very little which we can say about the current eruption which it holds in common with Laki.  Beyond the facts that
1) Its on Iceland in an area split by a crustal spreading center
2) we have a fissure eruption producing a moderate volume of fluid magma
3) there are moderate amounts of gasses typical to Icelandic eruptions being released (SO2, F, CL, CO2, CO, water vapor, et. al.)

... we really can't conclude the current eruption will evolve anything like Laki. It's complete speculation to think so.

....given the reduction in TSI and the increase of both ice and SO2 in the atmosphere how can we logically assume that the ice cap in the arctic won't recover more.....

It's important to avoid the mistake to conclude a small number of events (2) can permit one reliably predict a change.  2013/2014 don't yet imply a recovery.  There need to be quite a few more of them - at least 3 or 4 - before we can start talking recovery.  There would also need to be significant increases in coverage - volume did increase year over year 2013/2014 - but still not so much that they made it back to pre-2007 levels.  2013/14 Area and Extent are in a dead heat.  That outcome was driven by weather and feedbacks to the 2012 melt, which it seems was way outside of the trend.

Further, the impact of aerosols from the current eruption will not be enough in scale, or importantly persistent enough to seriously influence the ice.  Smoke from the wildfires in Canada and Siberia are more likely to affect the state of the ice than volcanic gasses, even if we reach "Laki" levels of emissions.

....just look at Antarctica and the record extent its at and near record area

Once again correct in fact, but incorrect in underlying assumption - that the increase of Antarctic ice signals some sort of recovery in the system.  The best research suggests that ice in the Antarctic is in rather dire straights - a number of large shelves have disintegrated over the last few seasons, and warm southern water has undermined and mobilized sheets of ice coming off of the west antarctic sheet.  The "recovery" is the product of a feedback which has tended to isolate the Antarctic from intrusions of warmer air from lower latitudes.  The effect isn't more ice so much as it is greater volatility.  The heat entering the system is still increasing.

....all of that ice must produce an albedo effect and at what time does all this become like a domino effect? Its just something that's bugging me

The "dominoes" are neither massive enough nor numerous enough to change the trend.  Albedo is just one component of the system as a whole, which affects heat transfer.  There are many other aspects of the system which would require significant positive change to affect.
This space for Rent.

viddaloo

  • Nilas ice
  • Posts: 1302
  • Hardanger Sometimes
    • View Profile
  • Liked: 1
  • Likes Given: 0
Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« Reply #261 on: September 16, 2014, 11:57:08 AM »
Albedo during polar Winter is also close to insignificant, yet as we now enter into Antarctic Spring, it may play an increasing role.
[]

crandles

  • Young ice
  • Posts: 3379
    • View Profile
  • Liked: 239
  • Likes Given: 81
Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« Reply #262 on: September 16, 2014, 02:36:21 PM »
..given the reduction in TSI and the increase of both ice and SO2 in the atmosphere how can we logically assume that the ice cap in the arctic won't recover more.....just look at Antarctica and the record extent its at and near record area....all of that ice must produce an albedo effect and at what time does all this become like a domino effect? Its just something that's bugging me

SO2 needs to get up into the stratosphere for it to be long lasting and produce a cooling effect. Even if there was a large eruptive event this effect only lasts three years and that is for event in tropics. Near Arctic the effect is less clear as there are counteracting effects. Some Ash SO2...won't get high enough so will not be long lasting in atmosphere so the main effect would be pollutants on the ice which makes it easier for the ice to melt. We may well not have a large eruptive event so this melting ice effect may dominate.

Anyway best scenario would be a three year temporary blip then atmospheric sulphur conditions would be back to where they are and CO2 and other GHG would be higher than now.

Antarctica
It does look like there will be a record ice area for Antarctica. A good part of the explanation for this seems to be higher winds probably caused by shift in the polar cell in turn probably caused by ozone loss. OZone hole seems to have steadied and may be showing signs of a very slow recovery.

Higher winds may be causing more rapid movement of ice so that it is thinner but travels further. I am not sure whether it is clear whether there is more sea ice or not.

If the cause of the higher winds has ceased to get stronger then it is possible that other effects may start to overwhelm this current dominant effect. I don't know how long this might be. Does anyone? What do you suppose might start to dominate? Higher ocean temperatures? GHG levels? Can you name more likely effects that would further increase sea ice extent?

There seems to me to be a big difference between something we know is continuing to increase in effect, like GHG levels, and something where we know the cause seems to be ceasing if not reversing like Antarctic sea ice levels.

Domino effect
There does appear to be positive feedback in the system. This should not be confused with runaway positive feedback. Runaway positive feedback seems extremely unlikely and is not expected. If conditions for this ever existed then we wouldn't have a long history of a survivable climate for life on Earth. The positive feedback we have got is more like a temperature increase of 3C causes a 1C increase. That 1C increase causes a further 1/3C increase which in turn causes a 1/9C increase and so on. Thus the 3C forcing increase causes an eventual total temperature rise of 4.5C.

We have been cooler in the recent past so there is no reason to expect a runaway event in the cooling direction. Similarly we have been warmer perhaps 6000 years ago also in Eocene and other longer ago times, therefore there is no reason to expect a full blown Venus style runaway effect in the warming direction. A more limited runaway effect in warming direction if permafrost and methane hydrates are destabilised may be low probability possibilities in the warming direction but I don't see any possibility for something like that in the cooling direction; GHG levels are simply too high and going upwards not downwards. While other things can be larger than GHG levels over a few years, GHG level effects keep accumulating so that over three decades or more GHG clearly dominate.

viddaloo

  • Nilas ice
  • Posts: 1302
  • Hardanger Sometimes
    • View Profile
  • Liked: 1
  • Likes Given: 0
Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« Reply #263 on: September 30, 2014, 10:23:11 PM »
Also, could someone explain to a novice why we talk about a '40-year delay' of CO2 emissions before they take effect? Does that imply NO radiative forcing of temperatures for 40 years?
[]

jdallen

  • Young ice
  • Posts: 3410
    • View Profile
  • Liked: 650
  • Likes Given: 244
Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« Reply #264 on: September 30, 2014, 10:59:02 PM »
Also, could someone explain to a novice why we talk about a '40-year delay' of CO2 emissions before they take effect? Does that imply NO radiative forcing of temperatures for 40 years?

Not quite correctly stated.

More correct would be... 40 year delay before the effects are *felt*.  The radiative forcing is taking place.  The lag is how long before the sensible heat increases they cause reach a new balance with the changes in forcing.
This space for Rent.

viddaloo

  • Nilas ice
  • Posts: 1302
  • Hardanger Sometimes
    • View Profile
  • Liked: 1
  • Likes Given: 0
Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« Reply #265 on: September 30, 2014, 11:11:47 PM »
Thx. But CH4, by contrast, is felt immediately through local heating?
[]

Laurent

  • Young ice
  • Posts: 2546
    • View Profile
  • Liked: 13
  • Likes Given: 50
Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« Reply #266 on: September 30, 2014, 11:39:18 PM »
I think (not sure) that almost all the heat goes into the oceans (because they absorb the heat and because it is 70 % of the surface). 40 years must be the shortest of the oceanic cycles, where we see the heat that is stored is upwelled on the surface. Last time I asked a scientific, he said a drop of the ocean can take 500 years to go around the full cycle of the oceanic currents.

All the gazes have a direct effect, Ch4 is 200 times less than CO2 (nearly 2ppm compared to 400 ppm of CO2). I do think it is the direct effect that is important not the one calculated for 100 years (because it is calculated for a decaying amount, but when it is replenish...) Ch4 is also said to be 100 times more powerfull so...(Would love to have official datas)

crandles

  • Young ice
  • Posts: 3379
    • View Profile
  • Liked: 239
  • Likes Given: 81
Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« Reply #267 on: October 01, 2014, 12:34:31 AM »
Thx. But CH4, by contrast, is felt immediately through local heating?

Not sure if it creates much local heating. But so what if it does? Urban heat island effect is not considered an important forcing is it? So effect of adding to long term radiative forcing seems more likely to be the worrying effect?

Quote
The radiative forcing is taking place.  The lag is how long before the sensible heat increases they cause reach a new balance with the changes in forcing.

I would suggest you need a lot of radiative forcing imbalance to get the ocean temperatures moving upwards and well over 100 years for ocean temperatures to get anywhere close to reaching equilibrium with the radiative forcing. What happens to ocean temperatures this year could well be mainly noise but the underlying trend depends mainly on last 40 years of radiative forcing imbalance. So something vastly different than usual anthro emissions would have an effect beginning immediately (and lasting for 100 years+ before ocean temperatures catch up). Note that something different from 10Gt of carbon emissions like 50Gt, sounds like a big difference but when you add it to 300Gt over last 40 years, 350 versus 310 doesn't seem like such a large difference (less than 13%). 

However emissions are generally growing quite smoothly so you rarely, if ever, get anything 'vastly different than usual anthro emissions'. Hence even with a different emission path where the emissions grow more different each year it still takes a long time of these growing accumulated RF difference before the expected temperature path differs significantly.


The short explanation for a novice is that it is the huge thermal inertial of the oceans.

viddaloo

  • Nilas ice
  • Posts: 1302
  • Hardanger Sometimes
    • View Profile
  • Liked: 1
  • Likes Given: 0
Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« Reply #268 on: October 01, 2014, 02:09:32 AM »
Not sure if it creates much local heating. But so what if it does? Urban heat island effect is not considered an important forcing is it? So effect of adding to long term radiative forcing seems more likely to be the worrying effect?


There is the element of thawing even more methane hydrates creating even more local heat in the same area, if already thawing seabed hydrates are the source of the methane causing local warming. So there is that....
[]

crandles

  • Young ice
  • Posts: 3379
    • View Profile
  • Liked: 239
  • Likes Given: 81
Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« Reply #269 on: October 01, 2014, 02:31:24 AM »
There is the element of thawing even more methane hydrates creating even more local heat in the same area, if already thawing seabed hydrates are the source of the methane causing local warming. So there is that....

How deep do you think these seabed hydrates are and how much thermal inertia does that sea provide?

Permafrost giving off methane, causing some local warming, causing more permafrost degradation may be a little more plausible. Even then I have difficulty imagining there being enough methane being released for it to linger around enough to create much of a local heating effect and then the heat has to get through the active layer to the permafrost and that has to release sufficient extra methane to at least maintain the locally higher temperature rather than winds dispersing it.

Perhaps I am just being unduly sceptical of this?

viddaloo

  • Nilas ice
  • Posts: 1302
  • Hardanger Sometimes
    • View Profile
  • Liked: 1
  • Likes Given: 0
Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« Reply #270 on: October 01, 2014, 03:09:26 AM »
Perhaps :D

The ESAS — Eastern Siberian Arctic Shelf — is a vast and very shallow part of the ocean. If conditions in the seabed are already thawing before the CH4 driven local warming, this could push things over the edge and secure an even bigger release.
[]

jdallen

  • Young ice
  • Posts: 3410
    • View Profile
  • Liked: 650
  • Likes Given: 244
Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« Reply #271 on: October 01, 2014, 05:55:30 AM »
The obstacle for a prompt release of ESS hydrates is a sufficiently large and persistent heat source.

They hydrates are buried in sediment, which itself is close to 0C or below.  Before the hydrates can disassociate, you need to heat *that*, as well as provide the heat necessary to permit the phase change.  That much mass won't heat up fast, or uniformly.

The greater probability favors a slower, more uniform release.
This space for Rent.

viddaloo

  • Nilas ice
  • Posts: 1302
  • Hardanger Sometimes
    • View Profile
  • Liked: 1
  • Likes Given: 0
Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« Reply #272 on: October 01, 2014, 06:48:26 AM »
IMO, the Laptev Sea with currently 4+ anomalies will be that persistent heat source. Local CH₄ heatwaves will just add hurt to the injury.

The IPCC, BTW, says in its 5th report that seabed hydrates cannot melt, which is very reassuring. I feel so safe. Their argument is that the shallow seawater will expand due to the warming and thus increase the pressure on these hydrates. IPCC saves the day!
[]

wili

  • Young ice
  • Posts: 3342
    • View Profile
  • Liked: 602
  • Likes Given: 409
Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« Reply #273 on: October 01, 2014, 10:47:57 AM »
"hydrates are buried in sediment"

They aren't all uniformly buried in sediment. Along slopes, the hydrate strata meets the water, and that is exactly where people are worried about. Break down of hydrate on slopes can also lead to submarine landslides which could uncover further hydrate...



http://www.ruf.rice.edu/~hydrates/about.html

(Keep in mind that when it is directly exposed to sea water like this, melting is subject not only to increases in warming and decreases in temperature, but also to changes in salinity. )

Warming of such slope areas could come not only from above (as more and more of the ocean is ice free for more and more of the summer), but also potentially from changes in sea currents. Warm currents from the Atlantic have been intruding further and further into the Arctic recently, iirc.

Besides, the 'sediment' is largely sub-sea permafrost, as I understand it, which is itself subject to melting.

Furthermore, there can be trapped free gas beneath the hydrates.



http://energy.gov/fe/science-innovation/oil-gas-research/methane-hydrate

And again, there are big uncertainties in the models for how the Arctic will respond to warming.

http://www.sciencedaily.com/releases/2014/09/140926101859.htm#sthash.3eBFunfe.dpuf


 
« Last Edit: October 01, 2014, 11:09:47 AM by wili »
"A force de chercher de bonnes raisons, on en trouve; on les dit; et après on y tient, non pas tant parce qu'elles sont bonnes que pour ne pas se démentir." Choderlos de Laclos "You struggle to come up with some valid reasons, then cling to them, not because they're good, but just to not back down."

Peter Ellis

  • Grease ice
  • Posts: 619
    • View Profile
  • Liked: 33
  • Likes Given: 14
Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« Reply #274 on: October 01, 2014, 12:28:18 PM »
Some while back the folks at RealClimate ran the numbers and showed that sea floor volcanic eruptions can't have any effect on sea ice cover - there's just too much water in between, so the extra heat at the bottom of the ocean gets dispersed and has no measurable effect at the surface.

I think all of us on this forum intrinsically agree with that.  We don't buy the denialist trope of "OMG LOOK AT THE VOLCANOES!" and instead understand that the sea ice retreat is driven by global changes in heat dynamics rather than by small scale local effects.


Now, turn that model upside down and consider the converse situation of a localised methane "burp" which raises the temperature of the surrounding atmosphere by a few degrees. Just the same way a localised volcano _under_ the sea can't melt the ice at the _top_ of the sea, a localised warm air patch at the _top_ of the sea can't melt the hydrates at the _bottom_ of the sea.  It's just too small-scale and local to be even worth considering.

Peter Ellis

  • Grease ice
  • Posts: 619
    • View Profile
  • Liked: 33
  • Likes Given: 14
Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« Reply #275 on: October 01, 2014, 12:33:33 PM »
To forestall the next comment:

Yes, I know the volcano analysis was talking about the deeper ocean rather than the ESAS.  Given that you're talking about a couple of km depth compared to 50m depth, that's a little under two orders of magnitude difference. 

Might that mean that warm air can melt buried hydrates even though a volcano can't melt sea ice?

No, because the rock is at ~1000 degrees above ambient temperature, while the putative warm air patch from methane release is at best a few degrees above ambient - so there's your two orders of magnitude the other way in terms of heat flow.  Moreover, the specific heat capacity of rock is much higher than that of air, so you have yet more orders of magnitude difference going the other way.


It's just not remotely physically plausible.

jdallen

  • Young ice
  • Posts: 3410
    • View Profile
  • Liked: 650
  • Likes Given: 244
Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« Reply #276 on: October 01, 2014, 06:21:50 PM »
Wili - I will grant your points.  That said, even with them, catastrophic release of ch4 is still dependent on the *specific* confluence of multiple conditions - the right distribution of hydrate, the right temperature, the right salinity, the right sub-surface topography (on a large scale...) a lot of "rights" to line up. I'm very dubious they add up to catastrophic release.

Permafrost adds its own ch4 contribution, but similarly, requires a large input of heat to unlock.  The key to my argument is, that even with the current incremental warming, neither the available heat nor the rate of transfer are high enough to support prompt release - gigatons over the course of a single melt season.

Do not mistake me though; I consider the methane release from clathrate and permafrost to be a serious problem.  I just don't think it will present itself in sudden events.
This space for Rent.

wili

  • Young ice
  • Posts: 3342
    • View Profile
  • Liked: 602
  • Likes Given: 409
Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« Reply #277 on: October 01, 2014, 07:15:48 PM »
"catastrophic release of ch4 is still dependent on the *specific* confluence of multiple conditions - the right distribution of hydrate, the right temperature, the right salinity, the right sub-surface topography (on a large scale...) a lot of "rights" to line up. "

I think that's true, and more (you forgot 'right pressure'--we can hope that destabilization will hold off till sea level rises enough to put enough added pressure on the buggers to keep 'em in place).

But I'm less sure that we know for certain how unlikely such a line up may be.

In any case, the main focus must remain on crashing our emissions down as fast and as far as possible, to avoid known unknown and unknown unknown dangers, and to give any unknown unknown negative damping feedbacks a chance to save our sorry @$$es in spite of ourselves.
"A force de chercher de bonnes raisons, on en trouve; on les dit; et après on y tient, non pas tant parce qu'elles sont bonnes que pour ne pas se démentir." Choderlos de Laclos "You struggle to come up with some valid reasons, then cling to them, not because they're good, but just to not back down."

johnm33

  • Guest
Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« Reply #278 on: October 02, 2014, 10:49:31 AM »
If an explosive reaction between salt and methane 70m [ish] below the surface in permafrost can happen onshore surely it can happen offshore too? Is there any evidence of such 'pockmarks' on the seabed of the ESAS or on the slopes of the continental shelves? I'm thinking such intrusions allowing [+4c?] water access to hydrate layers can only accelerate methane release? Ashore, if i understand correctly, the gas fields are directly below the permafrost layer and it's these depths that are the main source of methane outgassing in lakes, so i guess it's just a matter of luck whether one of these type of events 'tap' into a serious gas deposit or not, on land or at sea.
 Of course the argument holds even if there's a different explanation for the 'siberian holes'.

Peter Ellis

  • Grease ice
  • Posts: 619
    • View Profile
  • Liked: 33
  • Likes Given: 14
Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« Reply #279 on: October 02, 2014, 03:47:58 PM »
If an explosive reaction between salt and methane ...
I've seen this one noised around as an explanation for the Siberian crater, and I can't follow it at all.  Salt doesn't react with methane.  All efforts to trace this to its source end up at the Daily Mail.  I'm not going to believe it until someone with a relevant chemistry qualification posts the equation for the chemical reaction concerned and explains the mechanism.

jdallen

  • Young ice
  • Posts: 3410
    • View Profile
  • Liked: 650
  • Likes Given: 244
Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« Reply #280 on: October 02, 2014, 09:55:24 PM »
If an explosive reaction between salt and methane ...
I've seen this one noised around as an explanation for the Siberian crater, and I can't follow it at all.  Salt doesn't react with methane.  All efforts to trace this to its source end up at the Daily Mail.  I'm not going to believe it until someone with a relevant chemistry qualification posts the equation for the chemical reaction concerned and explains the mechanism.
Salt reacting with methane to cause an explosion quite simply is nonsense.

Methane release from warming will be an agonizing slow trial of a thousand cuts, not some apocalyptic evulsion.  That in no way detracts from how serious a problem it poses.

The eventual stable result will be a significant increase in atmospheric CO2. That is the problem we need to avoid.
This space for Rent.

johnm33

  • Guest
Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« Reply #281 on: October 04, 2014, 01:57:25 PM »
This is not where i first read of the idea but the names right "Anna Kurchatova from the Sub-Arctic Scientific Research Centre thinks the crater was formed by a water, salt and gas mixture igniting an underground explosion, the result of global warming. "[ From http://siberiantimes.com/home/] being unencumbered myself by a formal education in chemistry i assume she's basing this on something.   
I've just gone through the 'siberian hole' thread and it seems something similar does happen on the ESAS.

Andreas T

  • Nilas ice
  • Posts: 1149
    • View Profile
  • Liked: 18
  • Likes Given: 4
Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« Reply #282 on: October 05, 2014, 01:40:23 PM »
the article here http://siberiantimes.com/science/casestudy/news/first-pictures-from-inside-the-crater-at-the-end-of-the-world/ talks about the 'explosion' being like the popping of a champagne cork. The term explosion gets used loosely in the media with different meanings. Reading the whole article it also points out that there are no signs of burning so you should not think of a fireball kind of explosion just because it involves a flamable gas. Without more details it is difficult to interpret what the interaction between salt ice and gas is (probably not a chemical reaction), but it is more likely something which involves repeated melting and freezing over years creating the conditions where gas is released but builds up into a contained bubble and then burps and flips some muddy earths aside as it escapes. the depth of the whole may well be due to melting ice which has lost a protective layer of earth.

viddaloo

  • Nilas ice
  • Posts: 1302
  • Hardanger Sometimes
    • View Profile
  • Liked: 1
  • Likes Given: 0
Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« Reply #283 on: October 20, 2014, 10:36:55 PM »
I wonder how it is that Earth is only just within the Sun's habitable zone (Nature 2013), and still Ice was apparently most widespread during the last 2–3 million years, in accordance with Earth's overall cooler climate (ASI Blog 2012).

Is the Cryosphere in a regular eon overcompensating for the Earth's closeness to the Sun? Strange effect, but it seems to support lifeforms pretty well and for long periods of time.
[]

Peter Ellis

  • Grease ice
  • Posts: 619
    • View Profile
  • Liked: 33
  • Likes Given: 14
Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« Reply #284 on: October 21, 2014, 01:08:39 AM »
Viddaloo:  There are at least four competing effects going on, across vastly differing timescales. Going from fastest to slowest scales, we have:

1) Milankovic cycles - the precession of the Earth's axis of rotation in relation to its orbit.  This currently favours ice growth.

2) Continental drift - the continents are currently in a configuration that favours ice growth, with land at one pole and a fairly isolated ocean basin at the other.  In contrast, when land is clustered round the Equator and the poles are open deep ocean, it is much harder for stable ice caps to form there.

3) Global CO2 budget - notwithstanding recent anthropogenic CO2 releases, overall CO2 levels have been dropping intermittently since the Carboniferous.  After all, all that coal we're burning now came from somewhere, and much of it was CO2 in the atmosphere.

4) Solar evolution - the Sun is gradually getting hotter, as is typical for stars of this type at this stage of their life cycle.


It's important to understand that the _amount_ of CO2 released, and indeed the overall temperature of the planet, is not the major problem with AGW.  The problem is the _rate of change_, meaning that habitats will alter and seas rise faster than living things can cope with.  The absolute temperatures and sea levels involved won't be anything particularly unusual in the geological record.

viddaloo

  • Nilas ice
  • Posts: 1302
  • Hardanger Sometimes
    • View Profile
  • Liked: 1
  • Likes Given: 0
Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« Reply #285 on: October 21, 2014, 01:15:56 AM »
Thanks, Ellis. I would have expected Earth to be at the outer (colder) rim of the habitable zone (around the Sun) when 'recent' status was a Snowball Earth type glaciation, and, as I understand it, without humans we'd be moving in the direction of an even colder state than 2–3 million years ago.

That's why I had to google the 'habitable zone' statement and re–read the Nature piece. Nature says we're just outside of the Sun–distance that would have made Earth too hot for life. Hard to reconcile.
[]

DavidR

  • Grease ice
  • Posts: 740
    • View Profile
  • Liked: 36
  • Likes Given: 3
Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« Reply #286 on: October 24, 2014, 01:43:50 PM »
Recently I  accessed a web site that  gave annual and monthly temperature anomalies for selected latitude ranges. eg 60-90 N or 66-90 N or 60-90 S. It suggested that June 2014 the Arctic was comparatively cold.  Stupidly I forgot to bookmark the site. If any one has a link that provides that information I would appreciate it.
It cannpt be coincidental that  June was very  cold in the record and July  had little melt.
Thanks in anticipation.
Toto, I've a feeling we're not in Kansas anymore

Jim Hunt

  • First-year ice
  • Posts: 6268
  • Don't Vote NatC or PopCon, Save Lives!
    • View Profile
    • The Arctic sea ice Great White Con
  • Liked: 893
  • Likes Given: 87
Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« Reply #287 on: October 24, 2014, 09:25:17 PM »
Recently I  accessed a web site that  gave annual and monthly temperature anomalies for selected latitude ranges. eg 60-90 N or 66-90 N or 60-90 S. It suggested that June 2014 the Arctic was comparatively cold.  Stupidly I forgot to bookmark the site. If any one has a link that provides that information I would appreciate it.

Was this the link by any chance? Here's the resulting anomaly plot:
"The most revolutionary thing one can do always is to proclaim loudly what is happening" - Rosa Luxemburg

ChrisReynolds

  • Nilas ice
  • Posts: 1764
    • View Profile
    • Dosbat
  • Liked: 20
  • Likes Given: 9
Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« Reply #288 on: October 24, 2014, 10:01:36 PM »
Recently I  accessed a web site that  gave annual and monthly temperature anomalies for selected latitude ranges. eg 60-90 N or 66-90 N or 60-90 S. It suggested that June 2014 the Arctic was comparatively cold.  Stupidly I forgot to bookmark the site. If any one has a link that provides that information I would appreciate it.
It cannpt be coincidental that  June was very  cold in the record and July  had little melt.
Thanks in anticipation.

Need more of a clue. GISS do latitude bands but only for annual means, so 2014 won't be included.
http://data.giss.nasa.gov/gistemp/

The link Jim gave is to a site that isn't working due to data outage:
http://www.esrl.noaa.gov/psd/cgi-bin/data/composites/printpage.pl

But their NCEP/NCAR reanalysis timeseries, from which you can get numeric data is working.
http://www.esrl.noaa.gov/psd/cgi-bin/data/timeseries/timeseries1.pl
Let me know if you need guidance, should you want to use that.

Fisch

  • New ice
  • Posts: 3
    • View Profile
  • Liked: 0
  • Likes Given: 5
Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« Reply #289 on: October 25, 2014, 06:13:40 AM »
Medium-time lurker, first-time poster, likely to stay a lurker outside this thread.

I've noticed that on the chart shown here:

http://psc.apl.washington.edu/wordpress/wp-content/uploads/schweiger/ice_volume/Bpiomas_plot_daily_heff.2sst.png

Max/min thickness seems to arrive about a month/month-and-a-half after when max/min extent/area/volume arrive. Anyone know the reason behind this?

ChrisReynolds

  • Nilas ice
  • Posts: 1764
    • View Profile
    • Dosbat
  • Liked: 20
  • Likes Given: 9
Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« Reply #290 on: October 25, 2014, 08:38:01 AM »
Sorry Jim,

Yes it is working, I hadn't scrolled down, looks like most of what people here need will be available.

crandles

  • Young ice
  • Posts: 3379
    • View Profile
  • Liked: 239
  • Likes Given: 81
Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« Reply #291 on: October 25, 2014, 12:15:43 PM »

Max/min thickness seems to arrive about a month/month-and-a-half after when max/min extent/area/volume arrive. Anyone know the reason behind this?

The thickness is average thickness. When the freeze begins it adds lots of area of thin ice while it isn't cold enough to thicken thick ice. Thus the average thickness continues to decline past the point where ice is being added.

Similarly when the melt begins, it begins by melting out thin ice.

DavidR

  • Grease ice
  • Posts: 740
    • View Profile
  • Liked: 36
  • Likes Given: 3
Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« Reply #292 on: October 25, 2014, 02:31:30 PM »
Thanks Chris,
The third reference appears to be the one I lost. It shows June 2014 as one of the coolest Junes in the past 65 years, which says a lot about why the melt in July  was so low. 
Toto, I've a feeling we're not in Kansas anymore

viddaloo

  • Nilas ice
  • Posts: 1302
  • Hardanger Sometimes
    • View Profile
  • Liked: 1
  • Likes Given: 0
Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« Reply #293 on: October 25, 2014, 02:42:24 PM »
This one, DavidR?

Seems like an error:
[]

ChrisReynolds

  • Nilas ice
  • Posts: 1764
    • View Profile
    • Dosbat
  • Liked: 20
  • Likes Given: 9
Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« Reply #294 on: October 25, 2014, 06:59:15 PM »
Thanks Chris,
The third reference appears to be the one I lost. It shows June 2014 as one of the coolest Junes in the past 65 years, which says a lot about why the melt in July  was so low.

Good, damned useful page that one, shame you can't do it on a daily basis, but I'll make do with monthly.

Viddaloo,

I don't think it's in error. Of course as PIOMAS uses that NCEP/NCAR reanalysis as its atmospheric component arguing for the large volume increase being so striking against the previous volume drops as evidence for such cool temperatures seems rather circular. But I doubt if the Cryosat 2 data will fail to support PIOMAS.

Summer has generally been cold, back to 1980s levels. But the previous trend of summer warming suggests to me that this will be just a blip. We'll know in a couple of years whether we should start considering a regime shift to weather that aids ice retention.



Jan Feb March (overlapping December does not work) temperatures are still rising massively.



So if there is a regime change there is no evidence of it in Winter.


Both images are surface temperature north of 80degN to be close as possible to DMI temperatures.
http://ocean.dmi.dk/arctic/meant80n.uk.php
But that uses the ERA40 reanalysis.

viddaloo

  • Nilas ice
  • Posts: 1302
  • Hardanger Sometimes
    • View Profile
  • Liked: 1
  • Likes Given: 0
Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« Reply #295 on: October 25, 2014, 07:19:16 PM »
Thanks, Chris.

Do you think forest fire smoke can explain this sort of record cold Solstice? Blocking out sunshine more than ever should make a cold month, don't you think? Other explanations I haven't thought of?
[]

jdallen

  • Young ice
  • Posts: 3410
    • View Profile
  • Liked: 650
  • Likes Given: 244
Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« Reply #296 on: October 25, 2014, 11:41:48 PM »
Thanks, Chris.

Do you think forest fire smoke can explain this sort of record cold Solstice? Blocking out sunshine more than ever should make a cold month, don't you think? Other explanations I haven't thought of?

Speculation, with some supporting physics.

Increased open water means increased evaporation. 

The evaporation would tend to pull SSTs back to close to zero or slightly below. 

Evaporation also increases albedo via increased cloud cover.

I don't think we need to look too much further to identify a mechanism supporting steady/slightly cooler summer temperatures.  Heat required for phase change could more than make up for the drop.
This space for Rent.

Steven

  • Grease ice
  • Posts: 957
    • View Profile
    • Arctic sea ice data and graphs
  • Liked: 481
  • Likes Given: 19
Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« Reply #297 on: October 25, 2014, 11:47:07 PM »
Seems like an error:


Yes this seems to be an error.  The longitude range in the title of your graph goes from 0°W to 0°W, so I guess the graph only shows data for the (Greenwich) prime meridian.  You should probably select a longitude range from 0° to 360°, and perhaps also select the option "Area weight grids: Yes" on the above linked webpage.
 

ChrisReynolds

  • Nilas ice
  • Posts: 1764
    • View Profile
    • Dosbat
  • Liked: 20
  • Likes Given: 9
Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« Reply #298 on: October 26, 2014, 09:03:02 AM »
Thanks Steven, I missed that.  :-[

Viddaloo,

There have been fires before together with warm summer temperatures over the sea ice. I think the weather is more likely a candidate. In a study by Ramathan (IIRC) Asian particulate polution was found to increase insolation absorption in the mid troposphere, warming the atmosphere aloft. If it happened like that in the Arctic it might reasonably be expected to increase infra red back radiation, Ice is 'black' in infra-red, absorbing IR. Whereas in visible light it is white reflecting much of the sunlight (although you'd have to factor in albedo drop in summer). So smoke in the Arctic might not produce as much of a drop in net absorbed downwelling radiation (IR + visible) as one might suppose.

ChrisReynolds

  • Nilas ice
  • Posts: 1764
    • View Profile
    • Dosbat
  • Liked: 20
  • Likes Given: 9
Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« Reply #299 on: October 26, 2014, 09:28:46 AM »
June temperature attached.