Guest Post by Willis Eschenbach [See updated graph]
Inspired by some comments on another thread, I decided to see what I could find in the way of actual measurements of the amount of CO2 in the surface layer of the ocean. I found the following data on the Scripps Institute web site. What they did was drive around the ocean on four different cruises, measuring both the atmospheric CO2 levels and at the same time, the amount of CO2 in the surface seawater. Figure 1 shows those results:
Figure 1. All air-ocean simultaneous measurements from four Scripps cruises are shown as blue dots. The horizontal axis shows sea surface temperature. The vertical axis shows the difference between the CO2 in the overlying air, and the CO2 in the water. The red line is a lowess curve through the data. The paper describing the Scripps data and methods is here.
Now, I have to say that those results were a big surprise to me.
The first surprise was that I was under the impression that there was some kind of close relationship between the atmospheric CO2, and the CO2 in the surface seawater. I expected their values to be within maybe 5 ppmv of each other. But in fact, many parts of the ocean are 50 ppmv lower than the CO2 concentration of the overlying air, and many other parts of the ocean have 50 ppmv or more of CO2 than the CO2 in the air above.
The second surprise was the change in not only the size but even in the sign of the trendline connecting temperature and CO2 (red line in Figure 1). Compared to the CO2 level in the air, below about 17°C the seawater CO2 decreases with increasing temperature, at a rate of about -2 ppmv per °C.
Above about 17°C, however, the seawater CO2 content relative to the air increases fairly rapidly with temperature, at about +4 ppmv per °C.
To describe the situation in another way, when the water is cool, it contains less CO2 than the overlying air … but when the water is warm, it has more CO2 than the overlying air.
Say what? I gotta confess, I have little in the way of explanations or comprehension of the reason for that pattern … all suggestions welcome.
w.
[UPDATE] By popular request, here is the same data, but in absolute rather than relative units and without the lowess curve.
Figure 2. As in Figure 1, but showing the CO2 content of the surface seawater directly. Atmospheric CO2 varied very little during the time of the measurements.
My main question in all of this is, how does the CO2 content of the seawater get to be up to 100 ppmv above the CO2 content of the overlying air? It seems to me that the driver must be biology … but I was born yesterday.
Regards,
w.
RACookPE1978 says:
November 29, 2013 at 9:08 pm
Doc Martyn is getting much closer as he brings up several factors that – at ALL times – prevent ANY assumption of equilibrium conditions from being attained – at ANY time – on the real world earth.
While there never is an equilibrium, there is no problem to establish an average CO2 level in the atmosphere: after mixing into the bulk of the atmosphere (which acts as a filter), the CO2 levels are the same everywhere on earth within 2% of full range, except near huge sources/sinks (that is the first few hundred meters over land):
http://www.ferdinand-engelbeen.be/klimaat/klim_img/co2_trends.jpg
The ice cores with a resolution of less than a decade to 600 years (depending of accumulation speed) show a quite nice equilibrium between CO2 and temperature:
http://www.ferdinand-engelbeen.be/klimaat/klim_img/antarctic_cores_010kyr.jpg
except for the last 150 years or so.
Thus if you “filter” the data, you see that there is a quite linear releastionship between CO2 and temperature, before humans did release quite large quantities of CO2.
Thus whatever the momentary, hourly, daily, seasonally and yearly pCO2 data in the oceans, a weighted average can be used to calculate the change in uptake/release for a change in seawater pCO2 at one side or a change in pCO2 in the atmosphere at the other side.
Even if the average pCO2(aq) estimates are a factor 2 too low or too high, that doesn’t change the fact that the 14CO2 bomb test pulse decay rate doesn’t reflect the excess 12CO2pulse decay rate:
The 14CO2 bomb test pulse changed the atmospheric concentration of 14CO2 going into the oceans with +100% without changing the mass flows or the return concentration.
The 12/13CO2 human emissions pulse changed the atmospheric concentration of 12/13/14CO2 with +30% but also changed the isotopic ratio’s in the atmosphere and the mass flows, both going into the oceans and coming out of the oceans, without changing the return concentrations or isotopic compositions.
That gives different decay times for the concentration/ratio changes as for mass changes, practically independent of each other. The 14CO2 decay is much faster than the excess mass decay…
DocMartyn says:
November 29, 2013 at 5:04 pm
Now if you instantaneous increase the amount of carbon in one reservoir the the flux from that reservoir increases by the ratio of size increase, double the amount of carbon and double the flux. However, the opposite flux is unaffected until you increase the concentration of carbon in this reservoir. The two reservoirs do not exchange information and agree how much to change their exchanges.
Yes I know, it is a dynamic equilibrium. But you are wrong about the opposite flux: if the pCO2 in the atmosphere increases and the concentration (pCO2) at the upwelling places remains the same, then the influx is reduced because the pCO2 difference is reduced.
For the 14CO2 bomb spike, only the concentration of the outlflux is affected, not the total outflux or influx, neither the influx concentration.
For the 12CO2 “human” spike, the concentration of 12CO2 is hardly affected, but that of 14CO2 and 13CO2 is, both the outflux and influx are affected , but not the influx isotopic ratio’s.
The simultaneous 12CO2 bomb spike also affects the 14CO2 bomb spike (and 13CO2) decay by diluting the 14CO2 signal with 14CO2-free (and low 13CO2) emissions, but also by increasing the total mass uptake of the deep ocean – atmosphere exchange, as there is slightly more uptake than release.
Greg Goodman says:
November 29, 2013 at 11:34 pm
Willis seems to have gone walkabout, so I thought I’d add this graph from the most recent (1963) cruise.
http://climategrog.wordpress.com/?attachment_id=715
Interesting to see how pCO2 changes with temperature and upwelling…
There was also a strong deficit in the region stretching out from the Gulf of Panama into equatorial Pacific.
I suppose that the drop is from the cold upwelling waters near the Chilean coast which by the trade winds is going West and slowly heating up over that traject. If I remember well from other cruises, the maximum pCO2 was reached around the Galapagos islands. But much depends of the trade winds, thus the ENSO index…
Ferdinand Engelbeen says:
November 30, 2013 at 1:50 am
The simultaneous 12CO2 bomb spike
I don’t think that the recent increase in total CO2 is caused by the atomic bomb tests… I am sure that it is a human 12CO2 (and some 13CO2) emissions spike…
“But you are wrong about the opposite flux: if the pCO2 in the atmosphere increases and the concentration (pCO2) at the upwelling places remains the same, then the influx is reduced because the pCO2 difference is reduced.”
You are describing classical kinetics; the sum of two exponentials is an exponential.
Please, please, please think about the three components INFLUX, EFFLUX and OVERALL FLUX.
You are confusing Influx plus efflux equals overall flux, with influx.
Stop using mechanistic magic. Ignore the damned bias you bring to the table in the form of preconceived ways the oceans move carbon around by upwelling and downwelling. Trust the damn data.
Look at the line shape of the 14C curve; first-order
Look at the endpoint of the decay curve; the atmosphere is interrogating a reservoir >40 times bigger than itself.
Look at he rate constant; the decay rate is constant even though total atmospheric carbon is increased
CO2 exchanges with the surface of the ocean all the damned time, it does not exchange with an ‘average’ slab of ocean. It exchanges during the night and during the day. You can see CO2 disappear from the atmosphere from sun rise to mid-afternoon, then watch it rise again.
The SST changes the partition coefficient of Argon and the Ar levels swing during the daily and annual cycles. This stuff is real, and using Henry’s law and ‘average’ SST is quite utterly dumb.
“You can see CO2 disappear from the atmosphere from sun rise to mid-afternoon, then watch it rise again.”
There is a comment in the Scripp’s documentation:
“The atmospheric air stream on the LUSIAD cruise displayed a diurnal cycle in measured CO2 mixing ratio [Waterman et al, 1996, p. 20-21], likely caused by degassing of the plastic airline when exposed to sunlight. Only nighttime air data was considered free of this effect and thus acceptable. There is an additional column containing a flag in the LUSIAD data sets, specifically a “1” for the accepted nighttime data. The listed ΔX values for non-flagged data are considered to be unreliable.”
Here is detail snip of the hourly data. Don’t see the effect you refer to.
http://climategrog.wordpress.com/?attachment_id=716
Do you have evidence of this other than ” the damned bias you bring to the table in the form of preconceived ways the oceans move carbon around” ? 😉
That’s air-water difference , so presumably if there was a diurnal cycle it would be even clearer as one goes up and the other goes down. I don’t see their air line problem either.
I would hope that the takeaway from all this is a recognition that this is a complicated system, and the pat answers and narratives require a great many assumptions and conjectures to reconcile them to the data.
It is good always to keep in mind that every untested assumption in an argument is a point of vulnerability, and when a string of assumptions is required to support an argument, the probability that they are all true and correct decreases exponentially with the number. Thus, e.g. three 50% likely assumptions are only cumulatively 12.5% likely, and ten 90% assumptions are only 35% likely. It does not generally take many assumptions before your likelihood of being correct dips below 50%, and a hypothesis which is no better than a coin toss is not a useful hypothesis.
Any hypothesis which is supported by several assumptions is fair game to be questioned. The science is not settled.
DocMartyn says:
November 30, 2013 at 6:28 am
think about the three components INFLUX, EFFLUX and OVERALL FLUX.
In pre-industrial times for the deep ocean – atmosphere exchange:
influx = efflux = overall flux (or throughput)
and
net flux = efflux – influx = 0
For the 14CO2 bomb spike in 1960 (in % of the bomb spike):
air = 100 (twice the pre-bomb level)
influx = 100
outflux = 45
net flux = -55
For the pre-industrial atmosphere/ocean system (in GtC):
air = 290 ppmv
influx = 40
outflux = 40
net flux = 0
For the mainly 12CO2 human spike in 2000:
air = 390 ppmv
influx = 39.15
outflux = 40.85
net flux = – 1.7
in all cases ~99% 12CO2
The change in mass for a 30% change in atmospheric pressure caused by the extra 12CO2 is much smaller than the change in concentration of the doubling from the 14CO2 spike. Different mechanisms, different decay times…
Look at he rate constant; the decay rate is constant even though total atmospheric carbon is increased
The decrease of 14CO2 caused by 14C-free fossil fuels is slightly quadratic
The decrease of 14CO2 caused by the increase in total CO2 is sllightly quadratic
The influence of both on the linear decrease of 14CO2 due to deep ocean circulation would be hardly distinguishable from linear.
CO2 exchanges with the surface of the ocean all the damned time
The exchanges with the ocean surface are hardly of interest, any change in the atmosphere is followed by a 10% change in the ocean surface waters. It is the exchange with the deep ocean waters which is the main source/sink which removes or adds CO2 to the atmosphere.
————————–
About the diurnal variations, these are not that huge, not even in coastal environments, where one should expect the largest (temperature/biolife) variation:
https://www.academia.edu/2943276/Diurnal_variations_of_surface_seawater_pCO2_in_contrasting_coastal_environments
Temperature and wind are the main driving forces in the CO2 exchanges, biolife is far less important:
http://eprints.soton.ac.uk/358352/
Ferdi:
In pre-industrial times for the deep ocean – atmosphere exchange:
net flux = efflux – influx = 0
For the pre-industrial atmosphere/ocean system (in GtC):
net flux = 0
For the 14CO2 bomb spike in 1960 (in % of the bomb spike):
air = 100 (twice the pre-bomb level)
influx = 100
outflux = 45
net flux = -55
===
where do you get the net flux=0 assumptions from? Millennial-scale ice cores show significant change. How did that all happen with net zero flux?
Greg Goodman says:
November 30, 2013 at 10:19 am
where do you get the net flux=0 assumptions from? Millennial-scale ice cores show significant change. How did that all happen with net zero flux?
The change during a glacial-interglacial transition was ~100 ppmv over a period of ~5,000 years, or a change of 0.02 ppmv/yr or a net flux of 0.05 GtC/yr over the 40 GtC/yr in/out flux per year (if that didn’t change over glacial periods).
A very small difference, but still significant and measurable over the full period…
Over the whole Holocene, there was a small variation of +/- 5 ppmv, over a period of 10,000 years, again very small if one looks at the net flux changes needed to cause the change…
How on Earth do you change the rate at which carbon departs the ocean, into the atmosphere, by adding carbon into the atmosphere?
Do you think the molecules talk to each other and agree which way entropy is?
A rate constant is just that, a rate, a change per unit of time. Multiply the amount of stuff and you get flux. In a binary system you have two fluxes that are independent of one another. The relative amounts of stuff change the fluxes, but not the rate constants.
We know that the 14C went into the deep ocean at a rate of 0.056 y-1, this is the rate that CO2 goes into the deep ocean, 14C is a tracer for 12C. The atmospheric steady state is a function of influxes (ocean, land and man made fossil fuel emissions). The amount of carbon in the deep ocean is. essentially, unchanged since the industrial age and the flux of CO2 from the deep, into the atmosphere is also unchanged.
What sets the level of atmospheric CO2 in geological time is the amount of life/dust driven mineralization of carbon in the marine sediments. This is where most of the worlds carbon is to be found in biotic organic and inorganic carbon; with the marsh forest of land long gone, unsupportable with low atmospheric [CO2].
DocMartyn says:
November 30, 2013 at 10:49 am
How on Earth do you change the rate at which carbon departs the ocean, into the atmosphere, by adding carbon into the atmosphere?
Form Wiki ( http://en.wikipedia.org/wiki/Henry%27s_law )
“At a constant temperature, the amount of a given gas that dissolves in a given type and volume of liquid is directly proportional to the partial pressure of that gas in equilibrium with that liquid.”
If you add CO2 to the atmosphere, the partial pressure of CO2(atm) increases. For a fixed water flow, concentration and surface temperature at deep ocean upwelling places, the pCO2(aq) didn’t change, but the pCO2 difference between ocean and atmosphere decreases. The influx from the oceans into the atmosphere is directly proportional to the pCO2 difference and thus the influx decreases.
That is the difference with the 14CO2 spike: that didn’t change the influx of outflux in mass, only in concentration. The human 12CO2 spike did change the influx and outflux in mass, but hardly in concentration.
partial pressure is just another way of saying amount; the atmosphere is the same size and the amount of carbon has increase. There is a hell of a difference between pressure and partial pressure, they have quite different meanings.
You quote is interesting on its caveats;
“At a constant temperature”, which only occurs at the edge of an ice pack where saline freezes and nowhere else on the planet.
“of that gas in equilibrium with that liquid.” Whereas we always have fluctuating temperature, bioconversion of CO2 into organic matter and back again and fluctuating atmospheric CO2
DocMartyn says:
November 30, 2013 at 11:29 am
Come on Doc, you were asking:
How on Earth do you change the rate at which carbon departs the ocean, into the atmosphere, by adding carbon into the atmosphere?
Well the answer is straight forward: if you add carbon to the atmosphere, the partial pressure of CO2 increases, for the same upwelling. Thus decreasing the CO2 flux from tha tupwelling.
That there are fluctuating temperatures, biolife and (seasonal) variations of CO2 in the atmosphere is true, with or without an extra increase in the atmosphere. But still the increase of pCO2 in the atmosphere does decrease the influx of carbon, no matter the variability.
DocMartyn says:
November 30, 2013 at 11:29 am
BTW, it doesn’t matter if the 0.0004 bar pCO2 in the atmosphere is in high vacuum or accompanied by 0.9996 bar of other molecules: as much CO2 is dissolved in water (if the water doesn’t get boiling).
If pCO2 in the atmosphere increases to 0.0008 bar, twice the amount will dissolve in (fresh) water at equilibrium (and a lot more in seawater).
If there is a disequilibrium, the flux will be in ratio with the disequilibrium. Thus with a higher pCO2 in water than in the atmosphere, the flux will be from water to atmosphere. If the pCO2 in the atmosphere increases, then the flux will decrease and can stop or reverse, depending of the pCO2 difference.
” if you add carbon to the atmosphere, the partial pressure of CO2 increases, for the same upwelling. Thus decreasing the CO2 flux from tha tupwelling”
Pathetic. Telepathic deep water carbon.
DocMartyn says:
November 30, 2013 at 2:11 pm
Pathetic. Telepathic deep water carbon.
From:
http://www.pmel.noaa.gov/pubs/outstand/feel2331/maps.shtml
The pCO2 maps are combined with the solubility (s) in seawater and the kinetic forcing function, the gas transfer velocity (k), to produce the flux:
F = k•s•ΔpCO2
—————————————————————————————
OK, enough for this time, will be absent a few days, so behave when I am not watching this blog…
DocMartyn says:
” if you add carbon to the atmosphere, the partial pressure of CO2 increases, for the same upwelling. Thus decreasing the CO2 flux from tha tupwelling”
Pathetic. Telepathic deep water carbon.
===
It’s not telepathic, it’s happening at the ocean surface in response to the temperature and partial pressure difference. This is well established physics. You may wish to argue about the relative importance of the biological effects but displaying bigoted ignorance of the physics is not likely to convince anyone to listen to you about the biology.
The question you asked of Ferdinand applies in spades to you. Do you have anything but ” the damned bias you bring to the table in the form of preconceived ways the oceans move carbon around” ?
There is a huge difference between influx, efflux and net flux. Ferdinand appears to conflate changes with net flux to changes in both influx and efflux; this is quite clearly not the case.
You have a system where you have two equally sized reservoirs, A and B, with 1,000 molecules of dye in each, connected by a small pipe. The rate constant for movement, is 0.1 unit time-1.
At steady state/equilibrium per unit time 100 dye molecules go from A to B and 100 dye molecules go from B to A.
Now at t=0 add an extra 1,000 dye molecules to reservoir A.
At t=1, the rate of moment from A to B is 2,000 x 0.1 = 200.
At t=1, the rate of moment from B to A is STILL 1,000 x 0.1 = 100.
So now we have 1,900 molecules in A and 1,100 in B.
At t=2, the rate of moment from A to B is 1,900 x 0.1 = 190.
At t=2, the rate of moment from B to A is 1,100 x 0.1 = 110.
So now we have 1,820 molecules in A and 1,180 in B.
The flux from reservoir B does not know or care about the size of the gradient A/B, it only cares about the rate constant and the [dye] in reservoir B. The dye molecules do not say ‘hay guys, go back there are more dyes this direction than where we have just come from’
The net flux will give a single exponential and the endpoint will be at A=1,500 and B=1,500.
this end point tells us about the relative size of the reservoirs.
If the reservoir B was 9 times bigger than A, adding 1000 dyes molecules to A would give an end point of 1,100 in both reservoirs.
If the reservoir B was 39 times bigger than A, adding 1000 dyes molecules to A would give an end point of 1,025 in both reservoirs.
The end point of the 14CO2 decay profile tell us that reservoir B, the ocean, is >40 times bigger than reservoir A, the atmosphere.
If the 14CO2 were only being mixed with the surface of the ocean the 14CO2 pulse would have an end point near a third of its peak.
The 14CO2 disappearance is due to dilution of 14CO2 into the ocean void.
Now, as chemically 14CO2 and 12CO2 are almost identical, and as the ratio of B/A is >40 (from end point). We can determine the efflux rate that ALL CO2 from the atmosphere into the ocean, 0.056 y-1. Now, the rate of influx into the atmosphere must have matched this same outflux in the past so we know that the amount of CO2 from the oceans, into the atmosphere’s is pre-industrial CO2*0.056 y-1 or 290 (ppm) x 1.91 (conversion to GtC) x 0.056 y-1 = 36 GtC.
Note that this is about a third of the 90 GtC exchange between the atmosphere and surface layer of the ocean, which is about right given the two half-lives calculated for atmospheric 14CO2 of about 7.3 years for ocean surface and atmosphere and 12.3 years for disappearance in toto.
The rate that CO2 is going from the deep ocean, into the atmosphere, is essentially unchanged comparing an atmospheric [CO2] of 290 ppm with one of 400 ppm, as the total amount of increase in the oceans carbon is trivial as it is such a big reservoir.
Do not confuse a change in the overall flux in the system, with a change in both fluxes.
DocMartyn says:
December 1, 2013 at 8:01 am
The rate that CO2 is going from the deep ocean, into the atmosphere, is essentially unchanged comparing an atmospheric [CO2] of 290 ppm with one of 400 ppm
The error you make is that the transfers of CO2 are bidirectional at both the downwelling as the upwelling places, not unidirectional into the atmosphere at the upwelling and unidirectional into the oceans at the downwelling places.
For a molecule CO2 in the atmosphere it doesn’t make any difference in probability that it gets absorbed by the oceans if the oceans are completely devoided of CO2 or completely saturated. In the first case, all CO2 gets into the water and none comes back, in the second case as much CO2 gets back as is captured. But the probability of being captured is exactly the same.
If the pCO2 in the water is higher than in the atmosphere, simply more molecules escape from the liquid than enter the liquid from the atmosphere. Or reverse.
Take the CO2 levels as number of molecules (“in” is into the atmosphere)):
Upwelling at 500 μatm
Downwelling 100 μatm
Atmosphere: 300 μatm
Upwelling: 500 in, 300 out, net 200 molecules in
Downwelling: 100 in, 300 out, net 200 molecules out
Overall net: 0 molecules in or out
Now we increase CO2 in the atmosphere to 400 μatm:
Upwelling: 500 in, 400 out, net 100 molecules in
Downwelling: 100 in, 400 out, net 300 molecules out
Overall net: 200 molecules out