"Smart" and "Stupid" Questions - Feel Free To Ask

[Siffy]

I've a bit of a stupid question if any one can humour me.

Is there a study or any material which discusses the effect that fog has on thermal transfer mechanisms such as convection and that describes the difference of fog vs normal air at transferring heat to ice.

My casual understanding is that fog for a given temperature will transfer more heat to the ice than clear air with little relative humidity.

[Yuha]

What is the immediate ghg equivalency of methane? I understand using the 20 or 100 year equivalency when reporting the release of a particular mass of methane such as 50 gt. I don't understand using a 20 or 100 year equivalency when reporting parts per billion. If methane in the atmosphere is 1865 ppb its ghg effect will only decrease if its parts per billion decreases. It makes more sense to me to report the 100 year effect when discussing a mass or volume of menthane but use the immediate effect when discussing fractions of the atmosphere.

A nice source of information on greenhouse gasses is the NOAA Annual Greenhouse Gas Index (AGGI).

Based on the formulas there, the radiative forcing of methane at current levels is about 0.36 W/m²/ppm. For example, if the methane levels increase by 100 ppb, the radiative forcing increases by about 0.036 W/m². For CO₂ the number is about 0.014 W/m²/ppm, which makes methane about 25 times stronger greenhouse gas in this sense.

Often the comparison is made in terms of mass instead of concentration. The molecular mass of CO₂ is about 2.75 times the molecular mass of methane, which makes methane about 70 times stronger greenhouse gas in terms of mass.

These numbers are not constant but change with the atmospheric concentrations. When concentrations go up both forcing factors go down but the CO₂ factor goes down faster and thus the methane/CO₂ ratio tends to increase.

[wili]

The GWP for methane was increased, from 25 to 28 over a 100-year timespan and from 72 to 84 over a 20-year timespan.  When carbon-climate feedbacks are taken into account, the 100-year GWP of methane increases to a punishing 34 times that of carbon dioxide.  Methane is a growing source of emissions in many countries including the United States due to increased use of natural gas for energy.

http://www.enn.com/press_releases/4210

But then there's the Schindell paper:

Shindell et al., “Improved Attribution of Climate Forcing to Emissions“,
http://www.sciencemag.org/cgi/content/abstract/326/5953/716

This paper argues that methane is more potent than previously realised due to the interaction with black carbon. The paper gives a revised Global Warming Potential for methane measured over 100 years as 33. This is an increase of over 30% compared to the value of 21 given in the IPCC Second Assessment Report used for the Kyoto Protocol.

Over 20 years, Shindell et al. calculate this GWP to be 105.

....
I have my own stupid question, though. (As usual, my apologies if this has been addressed and I missed it.):

It is my understanding that acidic water melts at a lower temperature than non-acidic water. The ocean has famously become more acidic. Is that a significant factor in increased melt from ocean water, both of regular sea ice and of ice shelves we've been hearing so much about recently?

Thanks ahead of time, and apologies if this is over-the-top boneheaded.

[Anne]

Thank you, Jim and jda for replies to my previous Stupid.*  Here's a new one:

People talk about the weather as though it were the ultimate factor affecting ice melt. What about currents and bottom melt? Where is the heat going from Siberia and western Alaska? What has happened to the Fram Strait export, and why? How are Arctic currents changing? Woods Hole seems to have precious little about what's changing.
http://www.whoi.edu/main/topic/currents--gyres-eddies
How are current currents being monitored?

PS: Wili has a question just above this post and I'm v interested in the answer to that too.

*(Re how good are the data, I guess a better question would have been to ask what sort of confidence intervals attend the various models but I can find that out by looking them up. I was just getting the sense of disagreement between what the heat input seems to be suggesting and the CT etc measurements. I see NSIDC works to 95%.)
http://nsidc.org/data/docs/noaa/g02135_seaice_index/   

[johnm33]

Hi Anne, Fram export, open this http://earth.nullschool.net/#current/wind/surface/level/orthographic=-56.26,85.26,512 click on Earth, go down to control and click the left << [-1 day] shows winds blowing up through Fram for 5 days

[Anne]

Thanks, John! But why had it stalled for so long? I think when we look at the atmosphere alone we are looking at barely half the story.

[SteveMDFP]

Thanks, John! But why had it stalled for so long? I think when we look at the atmosphere alone we are looking at barely half the story.

At some point in following this forum (or the blog), there was a link to an article about Fram export.  That paper, if memory serves, described Fram export as being highly seasonal.  Sluggish transport during the summer is normal; most transport is during the winter. 
If memory serves, we had reasonable brisk transport during the past spring, possibly above average.  I think the 20013 season had sluggish transport from late winter through the summer.

This year, *some* degree of significant transport happened not through the Fram, but through the other side of Svalbard, the not-named-Olga Strait. 

Actually following this mechanism of ice export out of the arctic seems, for most of us, to consist of looking at wind fields.  I understand, however, that PIOMAS models Fram export.

[LRC1962]

@Anne The reason there is a lot of talk about weather is many fold. Easily noticed, described, somewhat forecastable  and has more immediate impact. There are many other influences, some we are only now discovering quantifiably, but they tend to be still in the study stage, more expensive to conduct those studies and I feel partly because they can be depended upon so many other variables hard to nail down exactly how much and where that impact will be felt most. 1 of those are ocean currents. They do all have big impacts on the ice, its just very hard to know exactly how much, what kind and where it will hit.
With weather, its a far easier job. You have x weather hitting this area you can guess pretty closely you will have Y happening to the ice. The rest ... well if you had about 20 times as many working buoys we could get a far better picture.

[Bruce Steele]

Wili, 
"It is my understanding that acidic water melts at a lower temperature than non-acidic water. The ocean has famously become more acidic. Is that a significant factor in increased melt from ocean water, both of regular sea ice and of ice shelves we've been hearing so much about recently?"

That's a good one. I really don't know about pH and freezing point of water but the science fair experiment I found on google makes it look like you might be on to something. My question would be whether you would have the same effect by bubbling Co2 to change water pH as you get by dissolving a solid like citric acid?

 https://www.usc.edu/CSSF/History/2004/Projects/J0509.pdf

[wili]

Yeah, I saw that science fair project too. The take away, which I'm pretty sure is generally right, is that pretty much anything that mixes with pure water makes lowers its melting point.

I'm just not sure how large an effect that would be with CO2 > carbonic acid, especially since we are not starting with pure water.

Also, iirc, though the oceans are indeed becoming more acidic, it is from a slightly basic starting point, so the increased acidity actually moves the water closer to neutral--still bad for various life forms that have evolved in the older pH range, but we certainly aren't talking about battery acid, here.

[Bruce Steele]

Wili, something just doesn't seem right about this premise. I mean does a steam in N.Y. with a 6.2 pH freeze at a different temperature ( at sea level ) than a steam on the west coast with a pH of 7.4 ? So before I make a total fool out of myself I am putting this one on the shelf a while.

[greatdying2]

http://en.wikipedia.org/wiki/Freezing-point_depression

ΔTF = Kf · b · i

The above says that freezing (/melting) point depression (delta Tf) for stuff dissolved in water is directly proportional to its molar concentration (b) and a constant (Kf) (and i, which I guess is 1 for CO2 dissolved in water: http://en.wikipedia.org/wiki/Carbonic_acid? Anyways, it makes little difference, because...).

The above link suggests that Kf is ~2. However the following link suggest it may be ~3: http://www.wiredchemist.com/chemistry/data/molal-freezing-boiling .

But again, it makes little difference, because the difference (due to anthropogenic CO2?) in the concentration of dissolved CO2 seems to be something on the order of ~300 umol/kg, and pH change of say (to be generous) 8.1 to 7.6 (right?) = (10^-8.1) - (10^-7.6) = 8e-9 - 2.5e-8 ~= 2e-9.

http://www.pmel.noaa.gov/pubs/outstand/feel3087/images/fig02.jpg

So like on the order of a billionth of a degree (times 2 or 3) (for increased H+) or at best on the order of a thousandth of a degree (for dissolved CO2).

But OTOH this may be a stupid answer... mainly trying to remember my chemistry. Hope it helps though.

[ktonine]

People talk about the weather as though it were the ultimate factor affecting ice melt. What about currents and bottom melt?

Anne, there have been many papers written on stronger currents and the influx of warmer Pacific waters into the arctic and their affect on the sea ice - for example The role of Pacific water in the dramatic retreat of arctic sea ice in summer 2007

[greatdying2]

Stupid question to follow my stupid answer:

Has anyone modelled what would happen to the weather if (/when) the arctic sea ice buffer is gone? I.e., Just remove the arctic sea ice from the model(s) to see what happens.

The results might be interesting to those experiencing 'heat waves'. Maybe more people would start putting 2+2 together?

Thanks.

[Shared Humanity]

Stupid question to follow my stupid answer:

Has anyone modelled what would happen to the weather if (/when) the arctic sea ice buffer is gone? I.e., Just remove the arctic sea ice from the model(s) to see what happens.

The results might be interesting to those experiencing 'heat waves'. Maybe more people would start putting 2+2 together?

Thanks.

I have to believe that climate modelers are doing this. How else would they arrive at what future climate may look like which they periodically report? I do think they are likely very cautious about what they report because there is a certain degree of uncertainty with any of these models and they do not want to appear alarmist. I would love to be a fly on the wall and watch "what ifs" as they explore various climate scenarios. I bet some of the climate model outputs are terrifying.

[crandles]

Only a couple of studies I know of:

Schröder, D. and W.M. Connolley, 2007: Impact of instantaneous sea ice removal in a coupled general circulation model. Geophys. Res. Lett., 34, L14502, doi:10.1029/2007GL030253

and

Tietsche et al "Recovery mechanisms of Arctic summer sea ice"

These are looking more at what happens to sea ice than weather and the answer is the models quickly go back to level of sea ice they had before in just a couple of years. Therefore I don't think it sensible to look at weather impacts as these will be too much affected by instant removal and too far from normal ice levels for the model. Possibly you could look at weather effects in runs of removal in 2060 that Tietsche did but you probably need a whole lot of runs to identify what becomes more likely in absence of sea ice.

You really need a climateprediction.net to run models many times over to see different frequencies of weather events. I have asked them (CPDN) if their partial attributions of weather events can be sound if they don't attempt attribution to sea ice retreat. Their answer seemed rather 'well it isn't clear that sea ice retreat effects will dominate'.

Shorter version: I doubt the models can be made to run sensibly as you want reliably enough that you could trust the results.

[seattlerocks]

Hi, what are the implications of Nares strait breaking up? Why it seems relevant. I googled a lot but could not find explanation about it. Thx!

[Jim Hunt]

Hi, what are the implications of Nares strait breaking up? Why it seems relevant.

See for example "Large sea ice outflow into the Nares Strait in 2007":

http://onlinelibrary.wiley.com/doi/10.1029/2009GL041872/pdf

We note that the exported ice (at 4 – 5 m) found north of Nares Strait represent some of the thickest ice in the Arctic Ocean. This thick, old ice occupies the tails of the thickness distribution and takes years with the right conditions to replenish.

Once the Nares Strait breaks up export of that older, thicker ice from the Central Arctic begins.

[seattlerocks]

Thank you  very much, Jim!

[greatdying2]

Which illustrates how dependent the Arctic is on its peculiar geography. What if, for example, Ellesmere Island didn't exist. Might there be ice-free summers already?

[greatdying2]

Another stupid question. (Forgive me if it's not directly about ice.) Plots of atmospheric CO2 concentration are a lynchpin of the global warming debate. But what about CH4? Is methane being monitored (it must be?!), and if so, why aren't these plots more focussed on? I know that it has a *much* shorter half-life, but it's also far more potent while it lasts, right? And isn't there (still) concern about catastrophic release, e.g. from frozen methane deposits or from rotting no-longer-perma-frost?

Thanks!

[trebuh]

answer is $

[greatdying2]

Thanks again. Scary. Given the potential, it boggles the mind there isn't more research being done.

[wili]

My understanding of J. Frances's theory about 'stuck' weather patterns is that it is a consequence of disproportionate warming of the Arctic, including the ever greater melting of sea ice. But wouldn't that only explain north hemisphere phenomena?

But aren't stuck patterns now becoming more common also in the southern hemisphere (for example, what NZ is experiencing now)?

Is the warming of the southern oceans enough to create a similar dynamic there as in the north?

Or is there something else affecting the movement of these systems?

(This is where the really stupid question part comes in...so be nice )

Another thing we know about the basic changes going on in the atmosphere is that there is more water vapor (up by about 6% on average, iirc). Even though there is also more energy in the system, would all that extra water tend to slow down these system--are they just too heavy to move along as fast as they used to?

[Kethern]

My understanding of J. Frances's theory about 'stuck' weather patterns is that it is a consequence of disproportionate warming of the Arctic, including the ever greater melting of sea ice. But wouldn't that only explain north hemisphere phenomena?

But aren't stuck patterns now becoming more common also in the southern hemisphere (for example, what NZ is experiencing now)?

Is the warming of the southern oceans enough to create a similar dynamic there as in the north?

Or is there something else affecting the movement of these systems?

(This is where the really stupid question part comes in...so be nice )

Another thing we know about the basic changes going on in the atmosphere is that there is more water vapor (up by about 6% on average, iirc). Even though there is also more energy in the system, would all that extra water tend to slow down these system--are they just too heavy to move along as fast as they used to?

My first guess would be that it doesn't. The molecular weight of dry air is ~29, the molecular weight of water is 18. Assuming the water vapor displaces an equal amount of dry air than the extra water should be making the atmosphere lighter not heavier. Given the relatively small percentage of water to vapor to the total atmosphere I doubt it has any appreciable effect.

[helorime]

You are neglecting density.  MW does not tell the story.  Air is a gas, water is a liquid.  If the densities were equal our atmosphere would be under the oceans.  Humid air is substantially more dense than dry air.

[wili]

Thanks, helorime.

[Vergent]

Humid air is substantially more dense than dry air.

helorime,

I am afraid you have this backward. Oxygen has a molecular weight of 32 g/mole, nitrogen 28 g/mole. Water vapor has a molecular weight of 18 g/mole. Water vapor and steam are lift gasses.

We often talk of humid air as "heavy", this is a mistaken notion.

Verg

[SteveMDFP]

Humid air is substantially more dense than dry air.

helorime,

I am afraid you have this backward. Oxygen has a molecular weight of 32 g/mole, nitrogen 28 g/mole. Water vapor has a molecular weight of 20 g/mole. Water vapor and steam are lift gasses.

We often talk of humid air as "heavy", this is a mistaken notion.

Verg

For a slightly more academic discussion:
http://antoine.frostburg.edu/chem/senese/101/gases/faq/wet-air-dry-air-density.shtml

At a given temperature and pressure, a container of a given size will have a specific number of gas molecules.  If those molecules are of higher molecular weight, the gas is heavier.  If of a lower molecular weight (e.g., hydrogen, H2, or Helium, for example) the gas can be closer in weight to a vacuum than to atmosphere. 
Humid air may *feel* heavy, but it is actually lighter than dry air.

[helorime]

I stand corrected!  I did not know that.  In my head water in air was like a solute in water, incresing density.  I assumed that the polar nature of water would interact with the gasses in the air in a way not dissimilar to what it does in water, increasing the density with its transient electrical forces.

[be cause]

I suppose if the above were not true rain would have nowhere to fall from ..

[wili]

H, I obviously made the same assumption.
I guess that's why we come here, to learn.
What is the quote about the things we know for sure that just aren't so?
Thanks all.

[johnm33]

I'm suprised by this too,  does this mean that wherever evaporation is taking place the atmosphere expands at a prodigious rate? and of course with condensation the reverse?
 Plus a supplemental when exactly was sea level so high as to cover the Yamal peninsular?

[jdallen]

I'm suprised by this too,  does this mean that wherever evaporation is taking place the atmosphere expands at a prodigious rate? and of course with condensation the reverse?
 Plus a supplemental when exactly was sea level so high as to cover the Yamal peninsular?

You are mostly correct, and are now describing one of the major driving mechanisms of the great heat engine that is our weather.

In this case, the "steam engine" component

[Vergent]

Plus a supplemental when exactly was sea level so high as to cover the Yamal peninsular?

120 kybp

http://geochemistry.usask.ca/bill/Courses/International%20Field%20Studies/Sea%20level.pdf

[ktonine]

"It ain't what you don't know that gets you into trouble. It's what you know for sure that just ain't so."  Usually attributed to Mark Twain.

[TerryM]

Look to the clouds to see how heavy water vapor is.
Terry

[crandles]

Look to the clouds to see how heavy water vapor is.
Terry

Clouds are not water vapour but small water droplets.

Water vapour is light and tends to rise and the droplets are small so have large surface area to volume so that the droplets tend to get carried up with rising air until the droplets get large enough that their weight overwhelmes the updraft effect and they fall.

However the updraft effect is largely driven by water vapour condensing into droplets releasing latent heat, warming the air which expands to create lower density.

So I don't think you can tell water vapour is light by looking at clouds.

[johnm33]

So at sea level what volume would 1cc of water occupy as vapour, and how much lighter than 'air' would it be?

[crandles]

Googled density of water vapour to get:
At equivalent temperatures it is buoyant with respect to dry air, whereby the density of dry air at standard temperature and pressure is 1.27 g/l and water vapor at standard temperature and pressure has the much lower density of .804 g/l.

Water, Density 999.97 kg/m³

(news to me I thought it was 1000. g/l is the same as Kg/m^3)

so 1cc of water becomes 1000/0.804 = 1244 cc.

[TerryM]

Thanks Crandles
It's an old saw i learned from a pilot decades ago & it's stuck in my head like a commercial jingle.
I remember the phrase & forget that it's BS, such is the aging process.
Terry

[jdallen]

Googled density of water vapour to get:
At equivalent temperatures it is buoyant with respect to dry air, whereby the density of dry air at standard temperature and pressure is 1.27 g/l and water vapor at standard temperature and pressure has the much lower density of .804 g/l.

Water, Density 999.97 kg/m³

(news to me I thought it was 1000. g/l is the same as Kg/m^3)

so 1cc of water becomes 1000/0.804 = 1244 cc.

Actually, density changes dramatically with temp.  It is most dense at around 4C, paradoxically, because of the structure of the molecule, and how transitory hydrogen bonds are formed.  Check out the water temperature/density graph.

This also helps illustrate why some sea level rise is a direct function of temperature, rather than melt.

http://www.engineeringtoolbox.com/water-density-specific-weight-d_595.html

[plg]

Googled density of water vapour to get:
At equivalent temperatures it is buoyant with respect to dry air, whereby the density of dry air at standard temperature and pressure is 1.27 g/l and water vapor at standard temperature and pressure has the much lower density of .804 g/l.

Water, Density 999.97 kg/m³

(news to me I thought it was 1000. g/l is the same as Kg/m^3)

so 1cc of water becomes 1000/0.804 = 1244 cc.

Water vapor has less density ("lighter" is not an appropriate term), but water vapor and air as not as oil and water, the vapor will not rise and float on top of the air, it will be a homogenous mixture. If you take a container and put in any arbitrary gases, they will be perfectly mixed. Only at extremely low temperatures (close to 0K) will the heavier molecules perhaps drift downwards (I think).

Of course, there are many other factors in the weather system that will affect the gas composition: pressure and temperature gradients, which may cause condensation, as well as other factors I know little about.

Having said all this, I may be completely wrong...

[crandles]

Having said all this, I may be completely wrong...

Pretty sure that people living at sea level don't suffocate in Argon and/or other heavy molecules so I don't think you are completely wrong

[Andreas T]

......
However the updraft effect is largely driven by water vapour condensing into droplets releasing latent heat, warming the air which expands to create lower density.
....

maybe I am stating the obvious but I want to stress that warming is this context is not an increase in temperature. What the condensation does, is it allows the air to rise and expand without (or with less) cooling. The difference between moist adiabatic lapse rate and dry adiabatic lapse rate shows that. Therefore the previously humid air is warmer and less dense than other air at that altitude which gives it its buoyancy.
 Another way to express that is looking at its potential temperature, should this air move to lower altitude its temperature will rise due to the compression but since temperature rise is steeper for the now drier air it will end up at sea level warmer than it started there as humid air.
So in that case there will be a rise in temperature and the increase in potential temperature shows that possibility.

[greatdying2]

Is extent simply the area that exceeds some arbitrary concentration threshold (e.g. 15%)? If so, is there any natural justification for the threshold, or is it arbitrary? More importantly, if it is just a threshold, then why does anyone care about extent? Shouldn't area be paramount?

(I'm tempted to say volume should be paramount, but since we can't see under water from satellites and have virtually no measurements, it's more likely a pipe dream...)

Taking the idea (that area has more information than extent) one step further, wouldn't it be useful to see area distributions rather than just averages. This is how it is displayed visually, but I haven't seen it tallied up on graphs, which would make for easier qualitative comparisons. Would this not go some way towards addressing the ice quality question?

[crandles]

Is extent simply the area that exceeds some arbitrary concentration threshold (e.g. 15%)? If so, is there any natural justification for the threshold, or is it arbitrary?

Yes.
Also the difference between area and extent depends on resolution.
Some organisation used (still use?) 30% rather than 15% but I think there seems to be a move towards 15%. There may be some justification for using these thresholds - eg above 30% there does not seem any ice free passage though the ice as seen from ship height whereas up to 15% looks like open water with just a few floes.

More importantly, if it is just a threshold, then why does anyone care about extent? Shouldn't area be paramount?

(I'm tempted to say volume should be paramount, but since we can't see under water from satellites and have virtually no measurements, it's more likely a pipe dream...)

It is fairly similar to the volume situation. Volume would ideally be paramount but we are not very sure of volume particularly if we go back in time.

If you want comparability over more than 50 years of time then extent is much better known than area as information comes from ships observations. Area may seem a better measure but if you have no ships within the ice to observe leads and polyna, then you have to use extent.

Taking the idea (that area has more information than extent) one step further, wouldn't it be useful to see area distributions rather than just averages. This is how it is displayed visually, but I haven't seen it tallied up on graphs, which would make for easier qualitative comparisons. Would this not go some way towards addressing the ice quality question?

Think Wipneus does a great job and has enough to do without having to edit the graphs to add the numeric information. Also do numbers on a single graph help much? I suspect it is the comparison of those numbers over time that is the useful information and Wipneus provides these graphs. (OK comparison to more years might be wanted but there are limits to what he can do.)

[Wipneus]

Is extent simply the area that exceeds some arbitrary concentration threshold (e.g. 15%)? If so, is there any natural justification for the threshold, or is it arbitrary? More importantly, if it is just a threshold, then why does anyone care about extent? Shouldn't area be paramount?

There are a couple of reasons for this. First area needs sea ice concentration from the whole Arctic. We only have reliable data from the end of 1978 to the present, before that nothing direct. Extent on the other hand can be estimated just from the position of the ice edge. We have useful observations of sea ice sightings since 1800 if not before that. Second the ice concentration from satellite observations in the marginal zones can be 10% or so off, so the cut-off is a trade-off between well above 10% and as low as possible.
Third, different satellite products differ far more in computed area while giving comparable extent values at the same time (even when resolution affect extent more than area). Fourth, even if those difference could be resolved, there is still the factor melt ponds. Unless compensated for, area which you get is not what you expect.

Taking the idea (that area has more information than extent) one step further, wouldn't it be useful to see area distributions rather than just averages. This is how it is displayed visually, but I haven't seen it tallied up on graphs, which would make for easier qualitative comparisons. Would this not go some way towards addressing the ice quality question?

I am always open to new ideas presenting the information that is out there. If this is one, can you please explain what exactly you would like to see?

[johnm33]

What are the physics of rising and expanding air [methane] bubbles in sea water? Specifically do they cool as they rise?

[SteveMDFP]

What are the physics of rising and expanding air [methane] bubbles in sea water? Specifically do they cool as they rise?

Any gas will cool as it expands under reducing external pressure.  But the bubbles would constantly also tend to exchange heat with surrounding water.  I'd be surprised if anyone has measured the temp of the gas that results. 

If you're thinking the cold gas could contribute to surface water freezing (or not melting), I'd suggest that any direct effect would be overwhelmed by the mixing action of rising bubbles, which would tend to bring warmish waters to the surface in the arctic. 

Any cooling action of expanding methane might also be overwhelmed over a longer period by bacteria oxidizing dissolved methane into CO2.