Guest commentary by Peter Minnett (RSMAS)
Observations of ocean temperatures have revealed that the ocean heat content has been increasing significantly over recent decades (Willis et al, 2004; Levitus et al, 2005; Lyman et al, 2006). This is something that has been predicted by climate models (and confirmed notably by Hansen et al, 2005), and has therefore been described as a ‘smoking gun’ for human-caused greenhouse gases.
However, some have insisted that there is a paradox here – how can a forcing driven by longwave absorption and emission impact the ocean below since the infrared radiation does not penetrate more than a few micrometers into the ocean? Resolution of this conundrum is to be found in the recognition that the skin layer temperature gradient not only exists as a result of the ocean-atmosphere temperature difference, but also helps to control the ocean-atmosphere heat flux. (The ‘skin layer‘ is the very thin – up to 1 mm – layer at the top of ocean that is in direct contact with the atmosphere). Reducing the size of the temperature gradient through the skin layer reduces the flux. Thus, if the absorption of the infrared emission from atmospheric greenhouse gases reduces the gradient through the skin layer, the flow of heat from the ocean beneath will be reduced, leaving more of the heat introduced into the bulk of the upper oceanic layer by the absorption of sunlight to remain there to increase water temperature. Experimental evidence for this mechanism can be seen in at-sea measurements of the ocean skin and bulk temperatures.
During a recent cruise of the New Zealand research vessel Tangaroa, skin sea-surface temperatures were measured to high accuracy by the Marine-Atmospheric Emitted Radiance Interferometer (M-AERI), and contemporaneous measurements of the bulk temperature were measured at a depth of ~5cm close to the M-AERI foot print by a precision thermistor mounted in a surface-following float. The M-AERI is a Fourier Transform Infrared spectroradiometer that has very accurate, NIST-traceable, calibration. The skin temperature can be measured with absolute uncertainties of much less than 0.1ºK The thermometer in the surface following float is accurate to better than 0.01ºK. Both are calibrated using the same equipment at the University of Miami.
Clearly it is not possible to alter the concentration of greenhouse gases in a controlled experiment at sea to study the response of the skin-layer. Instead we use the natural variations in clouds to modulate the incident infrared radiation at the sea surface. When clouds are present, they emit more infrared energy towards the surface than does the clear sky. The incident infrared radiation was measures by a pyrgeometer mounted on the ship, and the emission from the sea surface was calculated from the Stefan-Boltzmann equation using the skin temperature measurements of the M-AERI. The difference between the two is the net infrared forcing of the skin layer. If we can establish a relationship between the temperature difference across the skin layer and the net infrared forcing, then we will have demonstrated the mechanisms for greenhouse gas heating the upper ocean. That is seen in the flow chart on the right.
The figure below shows just the signal we are seeking. There is a clear dependence of the skin temperature difference on the net infrared forcing. The net forcing is negative as the effective temperature of the clear and cloudy sky is less than the ocean skin temperature, and it approaches values closer to zero when the sky is cloudy. This corresponds to increased greenhouse gas emission reaching the sea surface.
There is an associated reduction in the difference between the 5 cm and the skin temperatures. The slope of the relationship is 0.002ºK (W/m2)-1. Of course the range of net infrared forcing caused by changing cloud conditions (~100W/m2) is much greater than that caused by increasing levels of greenhouse gases (e.g. doubling pre-industrial CO2 levels will increase the net forcing by ~4W/m2), but the objective of this exercise was to demonstrate a relationship.
To conclude, it is perfectly physically consistent to expect that increasing greenhouse gas driven warming will heat the oceans – as indeed is being observed.
Acknowledgements:
The need for such an analysis grew out of a series of discussions with S. Fred Singer. The M-AERI was developed with funding from the Earth Observing System program of NASA. Participation in the SAGE cruise was supported by a grant from the NSF (OCE 0327188). Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author and do not necessarily reflect the views of the National Science Foundation.
Very interesting, and surprising to me. Is this skin layer an actual physical layer in the sense that water molecules in that layer tend to stay in that layer? I have trouble imagining that it is, but if it isn’t then wouldn’t the constant mixing negate the kind of insulating effect you are talking about here?
Quote
“how can a forcing driven by longwave absorption and emission impact the ocean below since the infrared radiation does not penetrate more than a few micrometers into the ocean?”
It strikes me as sad that this question needs answering or even asking.
RE: #1 – Indeed, I would think that any net increment in energy due to a net increment in long wave incident radiation would rapidly and efficiently dissipate in the enormous mass of water. So, yes, it would ever so slightly warm the mass. Ever so slightly ….
Coby, see the link in the second paragraph, it describes observations of the layer, and how persistent it is, and how it is reestablished after being broken up. It seems to make sense as described.
> I would think … would rapidly and efficiently dissipate
This is worth looking up, you will find a lot of information available about thermal layering in the ocean and in fresh water as well. Or take a dive into a deep lake sometime and notice the transition. See also ‘overturning’ as a seasonal phenomenon in lakes, for example.
I’m a bit confused. I think this is one of those cases where it is not what you don’t know that hurts you, but what you don’t know that is not so. Let me lay it out step by step so that someone can correct.
1) There in an exchange of heat energy between atmosphere and ocean.
2) Heating up the 1 mm (or smaller) topmost layers of the ocean (the “skin”) decreases the thermal gradient thus slowing the loss of heat from the ocean into the atmosphere.
3) If the ocean tends to lose heat to atmosphere, then this means that the ocean is warmer than the atomosphere? true? Heat tends to move from hot to cold.
4) But if we are warming that mm or less, then we are *increasing* the gradient between the warmer ocean and the cooler atmosphere.
All right, so I’m misunderstanding either what is being said or how heat exhange between the ocean and atmosphere works, probably both. Please correct. I’ve been a persistent poster here, and am obviously not a skeptic. I’m just having trouble following and need a clairification.
[Response: In a stable climate the net heat into the ocean would be zero. At some places there would be heating of the ocean, in other places, cooling of the ocean (generally, the cooling goes on at high latitudes, warming in the tropics, but there is a lot of variation associated with the shape of the basins, the thermohaline circulation etc.). In general, the heating would match the cooling and the ocean heat content would be roughly stable (though on short timescales that wouldn’t be true due to processes like ENSO etc.). There is a slight asymmetry in the heating and cooling because of the presence of convection (cooler seawater is heavier and therefore tends to sink), so the stable processes described above really relate mostly to the parts of the ocean where convection is not occuring. The skin temperature in areas where the ocean is being heated, is generally warmer than the bult temperature, but in this example, the ocean is losing heat to the atmosphere (the skin SST is less than bulk T). Along comes some extra LW forcing (due to greenhouse gases or clouds etc.), and according to the figure, this reduces the difference between the skin and bulk temperature and reduces the rate at which this area would be cooling (and thus causes anomalous heating). In a region where the ocean was already being heated, the same pattern would be seen but now since the skin SST was warmer, the skin-bulk difference would increase, causing more heat to go into the ocean. In an anomaly sense, the two cases are similar. -gavin]
[Response: I try a different way. To your point 3 the answer is yes – the ocean surface is on average warmer than the overlying air, because the ocean absorbs a lot of heat from the sun, part of which it passes on to the air above. Your confusion arises simply because we are now discussing how the bulk of the ocean below the skin layer gets heated. Thus we are talking not about the gradient between sea surface and overlying air, but we are talking about the gradient through the skin – i.e., the water temperature difference between the top and bottom of the skin layer, which controls how heat flows across this layer, from the bulk of ocean water below to the surface. Obviously, if you heat the top of the skin layer, this reduces the heat flow across this layer from below. Clear? Or still confusing? -stefan]
Hey All;
Just one quick question regarding a quote from the article.
“During a recent cruise of the New Zealand research vessel Tangaroa, skin sea-surface temperatures were measured to high accuracy by the Marine-Atmospheric Emitted Radiance Interferometer (M-AERI), and contemporaneous measurements of the bulk temperature were measured at a depth of ~5cm close to the M-AERI foot print by a precision thermistor mounted in a surface-following float.”
Does this mean that the following float was passing through water that had just been thoughly mixed by the Screws or Propellors of the ship?
Dave Cooke
[Response: Surface following, not ship following! – gavin]
Re: 6 – “bulk” being atmosphere?
[Response: No. Bulk is in reference to the ocean mixed layer – i.e. what you’d get if you sampled the first few meters of ocean. Sorry for the confusion. – gavin]
I would find the original post much easier to understand if information from the Response to Comment 6 was included. Since the assumption in the original post seems to be that the ocean is warmer than the atmosphere, it would be nice to state this at the beginning, even before explaining skin temperatures and gradients.
Ok -I think you finally hammered it into my simple mind. We have skin (first mm or less of ocean). We have bulk (next few meters of ocean). So:
Example 1) The ocean is losing heat to atmosphere (skin colder than first few meters of ocean ). A greenhouse effect heats the skin. The temperature difference between the skin and the first few meters of the ocean is reduced. The ocean loses heat more slowly than before.
Example 2) The ocean is gaining heat from the skin . The skin is warmer than the first few meters of ocean. A greenhouse effect heats the skin more. The temperature difference between the skin and first few meters of ocean is greater. The first few meters of the ocean warms faster.
Thanks!
Sorry it took a few tries before I got it.
I used to determine heat flow heat in the sedimentary column, from both offshore and onshore exploration wells.The theory cited is fine.
Average ocean water depth of almost 4km for the oceans, of mass about 1.1*10exp24gram, reveals about 0.25*10exp18gram in that top 1mm surface zone. I did a quick google re-the annual mass of water flowing from the Amazon and get 6.6*10exp19gram water/year. The Amazon represents the greatest rate of return of all rivers.
Glaciers also retreat. The oceans are warming largely because the warming of the atmosphere makes the rivers warmer. I don’t doubt the skin effect I just think the obvious has been neglected.
So how does one calculate the skin temperature in the roaring forties, where gale force winds are constantly ripping the tops off of 5 meter swells?
WAGNER (wild assed guess no explanation required) you could manipulate the absorption of the skin layer by tossing a small amount of different oils onto the surface. The surface layer will spread efficiently over a fairly large area. Depending on the oil, the IR, UV and vis absorption properties of the skin layer will vary systematically.
RE: #5 – The first thermocline is usually a few fathoms down. That is not what this paper is addressing.
Unless the air temperature was significantly lower than the bulk water temperature, a skin temperature, albeit slightly elevated versus the bulk temperature, by incident long wave radiation, would have an truly insignificant effect. Most places in the tropics it would, if anything, tend to inhibit ingress of conducted thermal energy from the (warmer than the water) air. The two main places I can think of where this may be of consequence would be where the Japanese Current gets into higher latitudes and similarly where the Gulf Stream does. On cool or cold days where there is sufficient sunshine, GHGs would reradiate and warm the skin. The loss of heat from the warm current would indeed be inhibited by the slightly lower thermal gradient due to the “inversion layer” caused by the warmed skin. We are talking about a very particular combination of factors here. I really must wonder whether or not the study actually measured this mechanism at all or did they measure some other effect?
RE: #12 – Yes indeed. This effect would not be very likely in such a setting.
RE: #13 – on that note, consider the possible effects due to biological factors, plankton blooms, floating organic debris / organisms’ waste products, etc.
As an amateur, reading what’s there:
> 12 how would you calculate skin temperature in the roaring forties…
Not — see the link in the second paragraph of the main post,
or read at least this bit:
“… the eddy cannot transport heat across the ocean surface by itself. The heat balance in the skin layer must be accomplished by molecular processes, hence the thin skin layer. The actual thickness of the skin layer depends on the local energy flux of the molecular transports, which is usually less than 1 mm thick and can persist at wind speed up to 10 m/s. For stronger winds, the skin layer is destroyed by breaking waves. Observations indicate that the skin layer can re-establish itself within 10 to 12 seconds after the dissipation of the breaking waves (Ewing and McAlister, 1960; Clauss et al., 1970).”
Re Steve’s belief noted in 5 that heat would “rapidly and efficiently dissipate in the enormous mass of water … ” the article seems to say the thin skin prevents that while it’s in existence; when it’s broken up, mixing occurs– but still not completely, water sorts out in layers.
Again, no pretense I know about this, I’m just saying –read the articles linked in the first few paragraphs of the main post and some of these simple questions are answered there.
Add hurricanes, see Stoat today for link to a nice recent example of the sea surface showing a clear cooling track after passage of the most recent big storm off Japan.
I hate to be nit-picky, but temperatures in Kelvin should not include the degree symbol, right?
Re #6
Gar, I think you meant to write: …this is one of those cases where it is not what you don’t know that hurts you, but what you [do] know that is not so. Yes?
Re: 20 – yes.
Dr. Schmidt;
Thanks, I was able to locate this link regarding the surface following sensor.
http://uop.whoi.edu/technote/9611tn.html
Dave Cooke
Will wind speed alter this relationship substantially?
For example, supposing it is more windy when it is very cloudy.
A stronger wind would I imagine cause more evaporation and cooling of the skin layer, making the skin minus bulk temperature difference even more negative. Removing this effect from Figure 2 (ie removing some of the hypothetical skin minus bulk temperature differences due to windy, cloudy conditions) would increase the calculated gradient further.
Of course, if there is no relationship between wind speed and net radiation then this does not apply. Presumably this has been checked or would be easy to investigate?
[Response: Anything that effects the surface fluxes (latent, sensible, LW+SW) will effect the skin temperature difference – and so wind speed clearly will. There is a general relationship between the diurnal cycle and winds – though I’m not sure of the amplitude of that at this particular site. But the amount of data looked at here is averaged over a number of days and so variations in incoming SW and in wind speed are probably well enough sampled to give a robust result. Peter Minnett is currently on a cruise off Iceland, but when he gets back, I’m sure he’d be happy to give you more details on the other factors in this physics. – gavin]
The excerpt I quoted says below windspeed that disrupts the skin layer, heat transfer occurs by ‘molecular processes’ — my guess would be that includes include both radiation and evaporation — anyone know?
I’d also think humidity at low windspeed would be pretty close to saturated in the air right next to the skin layer, limiting evaporation rate, and that wouldn’t change as quickly when cloud cover changed, compared to radiation rates.
I’m thoroughly confused. We’ve just had a recent post that said that there had been an unexpected drop in ocean temps. Or at least that a new batch of instruments had indicated a drop.
[Response: short term drop, long term heating. – gavin]
RE: #25
Dr. Schmidt;
If all things remained the same then what accounts for the “unexpected drop in ocean temps”? It appears the SST radiational and convective processes have not changed. The ocean currents have been relatively stable with a 20 Deg. E and about a 15 Deg. N deviation in the N. Atlantic seasonal Anti-Cyclonic position. (This is not unique over the last 30 years.) If anything the CO2 in atmospheric solution has increased, the data from ARM.gov indicates the solar SW/LW input appears stable,(with a slight SW decrease).
There has been a change in the apparent average humidity and air pressure according to the NESDIS NCEP data for the NH Analysis, indicating a greater deviation of the Northern Jet Stream and an apparent increased rate of pressure zone movements across the temperate zones. (I know this is a weather phenomenona and not climate; however, it would seem unusual that a possible natual deviation might be great enough to overcome an apparent 30 year trend suddenly without a noted significant weather event other then a possible SST heat transport of the 2005 Hurricane Season.)
Can you offer any insights as to the apparent deviation? BTW, I have not noticed it in any of the historic data; but, have you seen the New Foundland SST deviations as great as occured earlier this summer? Is it possible that the heat transport of the 2005 hurricanes may explain this years deviation? If this is true is it possible that the GHG as a contribution to GW may not be as big an issue as has been presented in the popular press? Thanks for you consideration, I apologize if it may be more appropriate to take this offline.
Dave Cooke
Regarding Figure 2: Have the data in this Figure been published in a peer-reviewed journal? What is the correlation coefficient associated with the linear fit of the data?
[Response: This is unpublished data, but I know that it is being written up as part of a larger discussion on ocean air-sea interaction. As mentioned above, Peter is on a cruise right now, but I’m sure he will be happy to answer your questions when he returns. -gavin]
As an oceanographer working on air/sea interaction and mixed layer dynamics, I hope I can clarify this issue somewhat (in fact, I’m at sea right now on the R/P FLIP, gathering data to study wave and mixed layer dynamics, but this is off the point).
I think a major aspect of the balance has been glossed over: the ocean is heated mainly by the visible part of the spectrum, the energetic part of the sun’s glare. This penetrates several meters (blue-green can penetrate several 10’s of meters, particularly in the clear water found away from coasts). In contrast, the only paths for heat LOSS from the ocean are infrared (blackbody) radiation and latent heat (evaporation). The sun heats the uppermost few meters; this has to find its way to the actual very thin surface layer to be lost. In equilibrium, then, there is a significan flux toward the surface a few cm under, and the sense of flux from infrared alone has to be significantly upward. Given this, it is quite clear that any reduction in the efficiency of upward radiation (by, say, reflecting it right back down again), will have to be compensated for by increasing the air/sea (skin) temperature difference, hence having a warmer subsurface temperature.
This still leaves aside the latent heat flux, which in general accounts for something like half the upward heat flux.
The balance is NOT, as portrayed here, between up and down infrared; rather it is downward “visible” (including ultraviolet, even), versus upward NET infrared and latent heat fluxes.
Once trapped in the mixed layer, any excess heat makes its way down into the interior via much larger scale processes, including lateral advection and mixed-layer deepening due to wind and wave induced motions. This large-scale vertical redistribution takes a while- decades to hundreds of years- before equilibrium is re-established. The fact that we can already see this is quite remarkable.
> The fact that we can already see this is quite remarkable.
Say more, please? For us non-experts, remarkable how? Change in rate compared to prior experience?
Thanks you JA Smith!
Just the fact you are commenting from the R/P FLIP is really interesting. I remember reading about FLIP when I was young and trying to pick a career. Info about the FLIP is here:
http://www.mpl.ucsd.edu/resources/flip.intro.html
The explaination about different wavelengths is very helpful. It’s useful to step back and see the big picture when you are trying to make out the details. I understand the orginal post better now.
I try will apply what I have learned about climate science and try to answer #29 (Hank Roberts). The large-scale vertical redistribution of the excess (anthropogenic) heat is remarkable because of how rapidly it is occuring and how widespread it is.
If I remember correctly the signal of the excess heat detectable in the oceans is not just a local phenomenon. Because it was so widespread, natural cycles were ruled out.
Second the oceans, as a whole and not including current shifts like ElNino, change temperature slowly. The heat signal was detectable quickly and is increasing quickly and this is unusual in the normally stable oceans.
> Info about the FLIP is here: http://www.mpl.ucsd.edu/resources/flip.intro.html
Yeah! I remember when that was first launched and tested. Wonderful ship, amazing idea.
If the oceans aren’t ‘warmed’ by LW radiation then how come they are not significantly cooler than we see, closer to the -18C of a non ghg world?
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Peter, nobody said that. See #28.
Re #34, Hank, yes, of course. I’m not saying that what happens I’m saying it seems to me that’s (taken to an extreme) the implication of what Fred Singer is saying. Clear the world oceans do respond as the main post and #28 say.
Re #28: J.A. Smith’s commentary was on the mark. This RC post confuses the whole issue of ocean heat balance.
As a starting point, the only significant external heat source is incoming shortwave. This incoming shortwave heating is balanced by ocean heat loss through back radiation (41%), evaporative heat loss (53%), and heat loss by conduction and convection (6%). The net changes in heat loss through these processes are affected by GHG’s. For example, increased well-mixed CO2 and water vapor decrease the rate of heat loss through back radiation.
It is humbly suggested that the processes governing ocean heat changes are not as straitforward as they might seem however. Ocean heat content is ultimately controlled by a number of complicating factors including positive and negative forcings and feedbacks dealing with clouds, water vapor, and also CO2. These forcings and feedbacks effect the processes by which the ocean looses heat to remain in balance. It would be my suggestion that all the governing factors are still incompletely understood. Since the heat storage capacity of the ocean is >1000 times that of the atmosphere, having a solid handle on all these is crucial to accurately projecting even average mean climate across multi-decadal time. The new ocean heat numbers are not mearly interannual variability, but represent a challenge for the community to better understand all of these processes.
[Response: Actually, downward LW (~350 W/m2) is about twice as large as absorbed SW (~175 W/m2) as a heat input into the ocean. -gavin]
I was wondering if you were familiar with Lyman’s latest report (http://www.pmel.noaa.gov/~lyman/Pdf/heat_2006.pdf). My understanding of it is, is basically that every so often the equatorial oceans get hot enough they blow away the clouds and release heat into space. This accounts for the tropics not experiencing big temperature shifts during times of global warming. (But doesn’t let Europe and North America off the hook, unfortunately, since we’re not so close to the equator). I was wondering, did I get this simplification right, and how this would affect climate modeling?
[Response: See our recent post. -gavin]
Re #36: “This incoming shortwave is balanced by *net* ocean heat loss through back radiation (41%)” The key word *net* should have been used. Obviously much of the LW emmitted is absorbed in the atmosphere and emmitted to the ocean.
Gavin, thank you. For the layman however, this may be unclear (as is this thread). In its simplest form averaged over a year, can not the ocean heat balance be expressed as:
Q(s)=Q(b)+Q(e)+Q(h)
where: Q is the change of energy expressed in Joules,
Q(s)is incoming shortwave, Q(b) is the “net” back radiation loss, Q(e) is the net loss from evaporation, and Q(h) is the heat loss by conduction and convection
Please forgive a math-challenged geologist
Re# 28 onwards.
There’s more than just the physics of absorption/emission. Up to 9% of the incoming short wave radiation(400-700nm)is incorporated into biomass by photosynthesis, admittedly requiring other nutrients in optimal abundance. One third of this is lost by respiration, with degradation back to CO2, eg. at night. The biomass creates degraded longer wave energy at depth, well below the “skin depth”. The net effect of biomass is to enhance warming. The residue of biomass is incorporated into sediments, eventually as fossil carbon, limestone, sulphides and sulphates.
Photosynthesis is a pretty small contribution, as the necessary nutrients are almost never all available, particularly in the open ocean. I would be suprised if so much as 1% of incoming SW radiation was incorporated into biomass (1% is about as efficient as the most efficient land crops are at photosynthesis, net of respiration).
Also, virtually all of the biomass rots (degrades to CO2 or CH4) long before it has a chance to settle into sediments. This is a good thing, or else the biosphere would have run out of carbon long ago, as plate tectonics only recycles buried carbon on the scale of tens to hundreds of millions of years.
Re: #39
Hey Graham;
Of the remaining SW ~160 Watts/meter^2 what percentage results in the death of biomass and the removal of the associated carbon fixing activities? Is there an approximation as to the percentage of annual phytoplanton that has been killed by UV since 1970 as a result of the Stratospheric Ozone reduction. (By the way, how would this be measured, sampled turbidity and at what depth would this measure be appropriate?) Or maybe a correlation of Dobson Units to metric tons of global biomass reduction per day due to the UV ionizing effect?
We also have the question of if the phytoplankton is not killed; but, just “mamed a little” by UV, would this have a negative effect on the carbon fixing level of activity? The next question is what is the ratio of UV affected biomass CO2 fixation to CO2 fixation of non-UV affected biomass?
Sorry if the questions appear retorical I actually am interested if work in this area has been done, I have seen little as of yet. As to the LW effects, I am curious if the phytoplankton are dead and they add to the turbidity then they would particpate in an increase in the conversion of incoming EMR to LW and it’s transfer to the liquid it is suspended in would they not? Would turbidity not also play in the potential heat content of the top 10-40 meters? Is it possible to extract the turbidity data from the OceanColor data?
Sorry for the many questions, I just have not seen any data that addresses them. Since my thoughts would not be unique, I can only assume that this data is not of any value in relation to the issues…
Dave Cooke
Just juming on this thread to signal that “The Economist” weekly is doing a special on climate change.
the editorial is free (I think) : http://www.economist.com/opinion/displaystory.cfm?story_id=7884738
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Cheers
Re#40 and 41
The ideal conditions I quoted, are perhaps never realised so I concur with Yartrebo that much lower efficiencies are probable. Of course if oceanic biomass or nutrient levels have not changed over time the system remains in equilibrium, there is no net change.
However, over the time frame cited for GW effects we have degraded landscapes, forest clearance and soil erosion carries an increased load of nutrients into the oceans. Increased algal and plankton blooms in the Mediterranean and European coastlines are now annual events.
Biomass carbon oxidises back to CO2, releasing the same heat of combustion that generated it utilising SW radiation. That gives rise to the upward kick in the Keeling curve saw teeth during the Northern winters. Most of the photosynthesis and respiration apparently occurs in the northern hemisphere.
Again, only a tiny fraction of carbon and sulphur are preserved in the crust and as Yartrebo points out cycling occurs over a very long timescale, ca.t1/2=300-400 million years. Igneous and volcanic rocks have very low carbon and sulphur contents and reduced iron(FeII), the exhaled gases are oxidised, CO2 and SO2. However,carbon in sediments is predominantly carbonate(1 carbon reduced atom to 5 Carbonate carbon atoms), sulphate S equi abundant with sulphide(reduced or elemental)and ferric(FIII).Conventional opinion has always considered that descending plates compress and heat adiabatically as a pure physical process. However, all of the carbonate, carbon in kerogen and coal and sulphates and oxidised Fe are transformed with silica into reduced silicate forms and oxidised gases CO2 and SO2, the free energy changes result in degraded heat. I’ve added this paragraph as it is peripheral to the remark as to what drives the plates. The plates are driven by the chemical free energy changes in the crust and not necessarily by the average isotropic heat flow ca. 70mW/m2, from below the crust. How variable are the annual heat flows concentrated along mid oceanic ridges? I don’t know. I just feel uneasy about accrediting a recent enhanced oceanic heat content to a purely physical process.
Re: #44 “only significant external heat source is incoming shortwave.”
A “non-significant” heat source is from seafloor spreading. Spreading rates have averaged 2-8 cm/year since early Mesozoic. The rate of heat transfer is very small relevant to the current climate discussion. There has been some work by a group from Japan. I will try and find a recent paper and post it.
The prevailing theory on plate motions involves mantle convection. Rates of seafloor spreading may however contribute (over geologic time) to significant eustatic sea level variation. Changes in sea floor spreading rates effect the volume of the mid-oceanic ridges which may contribute to changes in the volume of the ocean basins.
I have a stupid question, and I hope someone can provide me with a (perhaps less than stupid) answer. First of all, I have only been looking at this topic for about a week, and really have no idea what I’m doing, and really don’t know what to think. I would like to know if there is any importance to a possible increase in the potential energy of the planet (perhaps based on the biosphere, ie. trees grow, chamical potential is released when wood is burned, or perhaps some mechanical atmospheric effect that increases potential energy by separating air masses – maybe generation of wind would be related, just wondering.) I ask because my limited understanding is that temperature is related to kinetic energy, but would not register an overall increase in potential energy, in which case energy from the sun could be partitioned in heat energy emitted from the planet and work used to increase potential energy, possibly allowing an energy balance that does not require a radiation balance, and also does not require a warming effect. Is there any way that this sort of mechanism could have importance to the question? Maybe this is already included in the arguments, just not in a way that was obvious to me. Again, I apologise if the question is ridiculous, but I really am very new to this.
Re #46: Steve, your question is not stupid. The first law of themodynamics governs system energy, heat and work. I hope someone with a better background in classical physics than myself will field your question.
Please indulge my jumping off the thread to respond to theJames Turner on Sept. 8. It deserved a retort.
James Turner, this is an attempt to use British Petroleum data to challenge your proposition tht CO2 increase is driven by global warming. If you really believed what you are saying:
[the level of CO2 in the atmosphere is growing BECAUSE of global warming]
you will conclude the planet is in a heck of a fix. That is, unless you refute (do you?) the physics of CO2:
Most of the light energy from the sun is emitted in wavelengths shorter than 4,000 nanometers (.000004 meters). The heat energy released from the earth, however, is released in wavelengths longer than 4,000 nanometers. Carbon dioxide doesn’t absorb the energy from the sun, but it does absorb some of the heat energy released from the earth. When a molecule of carbon dioxide absorbs heat energy, it goes into an excited unstable state. It can become stable again by releasing the energy it absorbed. Some of the released energy will go back to the earth and some will go out into space.
So in effect, carbon dioxide lets the light energy in, but doesn’t let all of the heat energy out, similar to a greenhouse. Agreed???
Because of our heavy use of fossil fuels, the amount of carbon dioxide in the atmosphere has been increasing since the industrial revolution. ( 280 ppmv Pre-IR and 380 ppmv, 2005) Agreed????
1. Global fossil fuel use data from British Petroleum Statistical Review of World Energy, June 2005 provided the following coal, oil and natural gas production for 2003 and 2004. I estimated 2005 data using conservative percent increase.
Coal
2003- 5.185 billion tons
2004- 5.538 billion tons
2005- 5.954 billion tons (7.5 percent increase)
Oil
2003- 28.1 billion barrels
2004- 29.3 billion barrels
2005- 30.8 billion barrels (5 percent increase)
Natural Gas
2003- 92,053 billion cu ft.
2004- 94,462 billion cu ft.
2005- 97,298 billion cu ft. (3 percent increase)
Global Tons of CO2
Coal
2004- 12.671 billion tons
2005- 13.621 billion tons
Oil
2004- 12.851 billion tons
2006- 13.494 billion tons
Natural Gas
2004- 5.526 billion tons
2005- 5.691 billion tons
Total CO2
2004- 31.048 billion tons
2005- 32.807 billion tons
1 GtC corresponds to ~3.67 Gt CO2
2.12 GtC or ~7.8 Gt CO2 correspond to 1 ppmv CO2 in the
atmosphere.
Source:
D. Schimel,et.al,CO2 and the carbon cycle. Pages 76-86
in [IPCC 95])
The January 2006 Mauna Loa CO2 concentration increase over 2005 was 2.98 ppmv, or 23 billion tons of CO2 equivalent.
If that increased CO2 concentration was driven by global warming, please tell us how much warming was observed from 2004 to Jan. 1, 2006. Or, do you want to revise your proposition?
Re# 45 and 46
For simplicity, for an Earth at “equilibrium” the energy of incoming SW radiation is balanced exactly, from physics, by the outgoing energy of LW radiation, otherwise the Earth would either warm up or cool down. This isn’t exactly true. You will remember James Lovelock writing, that by consideration of the planetary atmospheres of Mars and Venus with thermodynamically equilibrated products, they are dead planets, at least they are so now. Here on Earth, from the base of the crust upwards, the mix of elements as elements or compounds, up through to the top of the atmosphere are not at chemical equilibrium.
As a consequence of chemical potential and incoming SW radiation the observed mix is far from an equilibrium position. An analogy would be the two states of a re-chargeable battery or a fuel cell. The chemical potential or Gibbs energy state of a reaction is the driving force that drives the reaction to a mininum free energy or Delta G=0. The formula used unites all 3 laws of thermodynamics and is usually represented for a chemist or geochemist by the relation
DeltaG=DeltaH(enthalpy)- T*Delta S
Consider a reaction-
C + 2Fe2O3 == 4FeO + CO2
On the left is elemental and reduced C(carbon) and ferric oxide(oxidised iron). On the right is reduced iron as ferrous oxide and carbon dioxide(CO2).
On the left is how the Earth’s(crust), in part, exists now. On the right is how the Earth existed, in part, some time before the origin(s) of life.
We have ignored water as part of the fuel cell. Also ferric oxide is usually noticed as rust. It is a hydrate,ferric hydrate. I’ll write it as 2(Fe(OH)3.5H2O) so it is balanced(stoichiometric)with the above formula.
Mars and Venus had their compliment of water after accretion. It is believed water photolysis occurred on these planets, giving hydrogen and oxygen. The hydrogen was lost to space leaving highly reactive oxygen to combust reduced carbon(C and CH4) and sulphur(inc sulphide) to acid gases as well as oxidise near surface elemental or ferrous iron to ferric(red) iron. This water photolysis must have happened to the primordial Earth, with loss of Hydrogen to space but it was stopped, as it is today, by the presence of ozone(O3) which requires high oxygen tension to form and it quickly reoxidises hydrogen via OH hydroxyls back to water.
Carbon(oil/gas/coal)is highly reduced and combusts with Oxygen, both with high chemical potential) in the atmosphere to give rise to CO2, the well known GHG.It gives a lot of heat off in the reaction. In the top equation ferric oxide will combust C to CO2. The reason the Earth today does not resemble the right hand side of the equation is that life’s biochemistry does a great miracle; CO2 is driven by enzyme catalysts and SW radiation(the energy source)to produce a far from equilibrium source of reduced carbon, reduced sulfur amongst other elements,namely living flesh, plant or animal. Too much CO2 and the oceans become acidic. Too little CO2 and the oceans become basic. The living Earth is also described as a huge oxidative reductive system. A Scandinavian chemist, Sillen, revealed it was also a great acid/base catalysis system as well.
36% of the mass of the Earth is iron, free or elemental iron, Fe, typically highly reduced. If we could rehomogenise it the equilibrium process would prevail- a dead planet would result- and it’s unlikely that the life process could recommence.
The Earth’s crust(2.2*10^25g)contains 8.3% by mass of iron, not as FeII as one might expect on a primordial Earth but a mix with oxidised ferric. Geochemists or cosmochemists quote elemental compositions in atoms per 1000atoms of silicon. Elements like carbon and sulphur get lost in these classifications. If one analyses the crust and oceans in elemental compostions relative to carbon one gets the remarkable compoition
S(0.5),C(1),Ca(4)Fe(4)…H2O(10)…Si(30),(Al)30….
For every carbon atom in the crust there is half an atom of S, 4 atoms of Fe.etc. OK- one can recast as S1, C2 etc. The present day chemical potential ie. the excess energy stored from incoming SW over history has charged the original dead battery. It also contains historical information about the original stoichiometry. Note the 10 molecules of water for every carbon atom or for 2 of the ferric atoms that now reside in the crust(the other 2 in basalt and granite(minor)). If you add up the mass of carbon as carbonate(eglimestone) and carbon(kerogen/coal/oil/gas) in the crust it comes to ca. 98*10^21g. Those original 10 molecules of water(gas and liquid)would have been present as chemical hydrates, I’ve depicted them as rust above. The stoichiometry detailed above accounts for a water mass of 1.48*10^24g. The known water content of the Earth’s oceans is ca.1.2*10exp24g!
For those of you who are familar with Earth accretional history, the Earth’s water complement is a hidden assumption, it is based on an ad hoc late accretion by dirty snowball impacts. Years ago this stoichiometric chemical potential theory was rejected. A famous American geochemist pronounced it was fallacious. Were it true it would be valid and he stated that the Earth’s mantle was a far greater repository of carbon than the crust, at least 7 fold greater, yet without any evidence to support that claim. At the time my claim was that apart from the odd diamond, the mantle was barren of carbon.
Finally, going back to Bryan’s remark, he is certainly correct that the physical heat flow generated at ridges etc is tiny with respect to the flux of SW radiation. I’m addressing the biomass. On the desert surface that heat generated during the day is rapidly lost by more numerous LW photons at night. In those verdant valleys and oceans the SW has catalysed growth of biomass that doesn’t perish and re-oxidise overnight. It is stored and released as heat and delayed at the organims will. Of the 100% SW energy received, 100% was not re-emitted. How much is re-emitted? Over geological time ie the hundreds of millions of years it must balance out but with a chemical potential of components in a far from equilibrium state. Over the short term relevant to climate studies are their great swings in biomass abundance for reasons I mentioned before.
I’m not if this answers Part of Steve’s query but the chemical potential can be converted into mechanical and electrochemical equivalents.
Re #48: John, you say “you will conclude the planet is in a heck of a fix. That is, unless you refute (do you?) the physics of CO2:”
John McCormick, please understand that others do in fact comprehend and fully embrace Wein’s Displacement Law and Stefan Boltzmann, but are not yet convinced we completely understand the whole process of how the dynamic earth/ocean/atmosphere climate system works. Yes, most of us really do understand the basic physics that dictate a doubling of CO2 will warm the atmosphere 1 degree C. Please accept that beyond the fundamental laws however, there is a bunch more we are not as sure about. This includes all of the forcings and feedbacks that govern ocean heat content. Hopefully, we can all agree that we need to continue this wonderful research endeavor to better understand this facinating and important portion of earth science.