The world’s marine ecosystems risk being severely damaged by ocean acidification unless there are dramatic cuts in CO2 emissions, warn scientists.
The researchers warn that ocean acidification, which they refer to as “the other CO2 problem”, could make most regions of the ocean inhospitable to coral reefs by 2050, if atmospheric CO2 levels continue to increase.
This does indeed sound alarming, until you consider that corals became common in the oceans during the Ordovician Era – nearly 500 million years ago – when atmospheric CO2 levels were about 10X greater than they are today. (One might also note in the graph below that there was an ice age during the late Ordovician and early Silurian with CO2 levels 10X higher than current levels, and the correlation between CO2 and temperature is essentially nil throughout the Phanerozoic.)
Perhaps corals are not so tough as they used to be? In 1954, the US detonated the world’s largest nuclear weapon at Bikini Island in the South Pacific. The bomb was equivalent to 30 billion pounds of TNT, vapourised three islands, and raised water temperatures to 55,000 degrees. Yet half a century of rising CO2 later, the corals at Bikini are thriving. Another drop in pH of 0.075 will likely have less impact on the corals than a thermonuclear blast. The corals might even survive a rise in ocean temperatures of half a degree, since they flourished at times when the earth’s temperature was 10C higher than the present.
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Bill D (13:46:15) :
The take home message is that natural systems are complex and showing that one factor is important does not mean another factor is not also important. Indeed, we often see interactive effects, where, for example effects of the negative effects of increased UV light might accentuate the negative effects of warming temperature.
I would be surprised if any scientists in that field would agree with your first conclusion above.
Yes it would effect their funding .
Fortunately we have two Global United Nations Environment Programmes eg
Environmental effects of ozone depletion and its interactions with climate change: Progress report, 2008
http://www.rsc.org/Publishing/Journals/PP/article.asp?doi=b820432m
There are conflicts with the 2 expert panels in a number of areas.This raises some interesting issues, but would sidetrack from the issues here.
Let us discuss the area of UV and ecosystems and changes perceived or otherwise.
For expediency of response I will cut from some papers
The ability of biological species to adapt to adverse environments is one of the paradoxes of Ecological science.How the exclusion of some “players” from the” marketplace” will allow for smaller players to dominate the market due to enhanced adaptability.
To understand this lets pose a simple question ” Is Brown the new green in an ultraviolet world ? ”
Changes to the ozone levels and UV penetration are cyclical over the solar cycles from the 27 day rotation, the 11 year cycle ,the Gleissberg cycle and longer orbital parameters.eg Rozanov 2005
Solar variability is observed on three main time scales: solar rotation (27-day), solar cycle (11year) and the Grand Minima time scale. The magnitude of the variability progressively increases from the short to long scales. Earth’s climate responses are now found on all these scales. The most recognized are the responses to solar irradiance variations. These variations strongly depend on wavelength rising from 0.1% per solar cycle in total irradiance (mostly infrared-optical range) to 10% in UV and 100% per solar cycle in X-ray range. The variations in the total irradiance produce a small global effect. More substantial is the effect of solar UV variability on large-scale climate patterns. These patterns are naturally excited in the Earth’s atmosphere as deviations (anomalies) from its mean state.
How does the distribution of UVB, UVA, and photosynthetically active radiation vary on sensitive surfaces within the biosphere in the agricultural and forest canopies over the growing season? Plants have widely varying sensitivity to solar UV radiation. This can result in shifts in the competitive advantage of one plant species over another and consequently composition and health of both manages ecosystems.
“Daylength is the major environmental factor affecting the seasonal photosynthetic performance of Antarctic macroalgae. For example, the “season anticipation” strategy of large brown algae such as Ascoseira mirabilis and Desmarestia menziesii are based on the ability of their photosynthetic apparatus to make use of the available irradiance at increasing daylengths in late winter-spring. The seasonal development and allocation of biomass along the lamina of A. mirabilis are related to a differential physiological activity in the plant. Thus, intra-thallus differentiation in O2-based photosynthesis and carbon fixation represents a morpho-functional adaptation that optimizes conversion of radiant energy to primary productivity”
It is now known that various of the reproductive- and life history events in Antarctic macroalgae are seasonally determined: microscopic gametophytes and early stages of sporophytes in Desmarestia (Wiencke et al. 1991, 1995, 1996), Himantothallus (Wiencke & Clayton 1990) and P. antarcticus (Clayton & Wiencke 1990) grow under limited light conditions during winter, whereas growth of adult sporophytes is restricted to late winter-spring. Culture studies under simulated fluctuating Antarctic daylength demonstrated that macroalgae exhibit two different strategies to cope with the strong seasonality of the light regime in the Antarctic (Wiencke 1990a, 1990b). The so-called “season responders” are species with an opportunistic strategy growing only under optimal light conditions mainly in summer, whereas the “season anticipators”, grow and reproduce in winter and spring.
By virtue of their fine morphology, have a high content of pigments per weight unit, a high photosynthetic efficiency, very low light requirements for photosynthesis, and they are better suited to dim light conditions than adult sporophytes. This strategy ensures the completion of the life-cycle under seasonally changing light conditions. Low light requirements for growing and photosynthesizing are developed to cope with Antarctic seasonality and constitute adaptations to expand depth zonation of macroalgae.
This suggests that the microalgae have adapted to predicting not only the early spring photosynthetically active radiation, but also high spring flux of UV due to ozone loss as seen by the levels of melanin pigmentation.
Envisat has captured the first images of Sargassum from space reports the ESA. The brown kelp famous in nautical lore for entangling ships in its dense floating vegetation, has been detected from space for the first time thanks to an instrument aboard ESA’s environmental satellite.
The discovery was made using the MERIS maximum chlorophyll index (MCI) which provides an assessment of the amount of chlorophyll in vegetation to produce detailed images of chlorophyll per unit area. MERIS is uniquely suited for this because it provides images of above-atmosphere spectral radiance in 15 bands, including three bands at wavelengths of 665, 681 and 709 nanometres in order to measure the fluorescence emission from chlorophyll a.
Chlorophyll is the green photosynthetic compound in plants that captures energy from sunlight necessary for photosynthesis. The amount of chlorophyll present in vegetation plays an important role in determining how healthy it is. Accurately monitoring chlorophyll from space, therefore, provides a valuable tool for modelling primary productivity.
“The 709 band used by MERIS is not present on other ocean-colour sensors. It was essential to our detecting Sargassum,” Gower said. “The MCI index has allowed us to find so many interesting things, including Sargassum and Antarctic super blooms. It really gives us a new and unique view of the Earth.”
In the arctic with similar radiation properties affecting the aquatic biosphere we see similar properties in the growth function of brown alga.
ABSTRACT. The effect of artificial ultraviolet (UV) and natural solar radiation on photosynthesis, respiration and growth was investigated in 14 red, green and brown macroalgal species on Spitsbergen (Norway) during summer 1998. In June, maximum mean solar radiation at sea level was 120 W m-2 of visible (370 to 695 nm) and 15 W m-‘ of UV radiation (300 to 370 nm), and decreased gradually until the end of the summer. In spite of incident irradiance, levels were low in comparison with other latitudes, and UV radiation stress on growth of Arctic macroalgae was evident. Transplantation experiments of plants from deeper to shallow waters showed, for most algae, an inhibitory effect of both UVA and UVB on growth, except in the intertidal species Fucus djstichus. The growth rate of selected n~acroalgaew as directly correlated to the variations in natural solar radiation during the summer. Underwater experiments both in situ and using UV-transparent incubators revealed a linear relationship between the depth distribution and the growth rate of the algae. In almost all species the photosynthetic oxygen production decreased after 2 h incubation in the laboratory under 38 pm01 m-‘ s-‘ photosynthetic active radiation (PAR 400 to 700 nm) supplemented with 8 W m-‘ UVA (320 to 400 nm) and 0.36 W m-‘ UVB (280 to 320 nm) compared to only PAR without UV. Like in the growth experiments. the only exception was the brown alga F. distichus, in which photosynthesis was not affected by UV. The degree of inhibition of photosynthesis showed a relation to the depth distribution, i.e. algae from deeper waters were more inhibited than species from shallow waters. In general, no inhibitory UV effect on respiratory oxygen consumption in all macroalgae studied was detected under the artificial radiation regimes described above, with the exception of the brown alga Desmarestia aculeata and the green alga Monostroma arcticum, both showing a significant stimulation of respiration after 2 h of UV exposure. The ecological relevance of the seasonal variations in the solar radiation and the optical characteristics of the water column with respect to the vertical zonation of the macroalgae is discussed.
Jose Aguilera et al MARINE ECOLOGY Vol. 191: 109-119, 1999
In summary we can conclude that high latitude species are adapted to changes in UV flux. That the response in species with elevated melanin pigmentation is more suited to early levels of available PAR where photosynthesis is present. In other species due to defensive response the populations do not significantly decrease ,however photosynthesis is attenuated due to light limitations (they go deep)
Ric Werme (06:26:51) :
Going back to the “more acidic” means an acid became more so doesn’t work since seawater isn’t an acid. So, let me substitute with “less alkaline”:
Since the process involved is the generation of H+ it is correctly described as becoming more acidic.
So the seawater gets less alkaline because the decrease in alkalinity
outweighs that of total carbon and [CO2] increases.
Sorry, I can’t get past that first line. You have me thinking H+ and OH- dancing in a circular argument then you shift to a black (or clear) solid and [a gas in brackets]. Good thing I got sucked up by computers before getting serious about my ChemE major. What the significance of those brackets? ChrisJ used that too, also TCO2, is that shorthand for Total CO2?
[X] is chemical shorthand for ‘the concentration of X’.
TCO2 is shorthand for Total CO2, i.e. ∑([CO2], [H2CO3], [HCO3_], [CO3–])
Steven Goddard:
No. Not with all of them.
But don’t let the handful around here get a rise out of you. Keep in mind that out of the many thousands of people who visit this site every month, only about a half dozen or so are the AGW groupies who always run interference. Someone has wired around their On/Off switch, and they’ve blown a fuse.
Most people are reasonable, and that’s why the tide is turning against the dwindling number of believers in the silly catastrophic AGW/CO2 fairy tale.
Following this thread there has been something bothering me. I haven’t read all the comments, so forgive me if I’ve missed some crucial points.
I’m trying to imagine local conditions in an area of reef forming shallow ocean say 1 km2, no more than a few metres deep and with a few metres of atmosphere above it….
So we have more CO2 in the atmosphere above this portion of ocean. More of this CO2 dissolves in the ocean and makes it slightly more acidic. However let’s say the temperature of the ocean has also increased, this will result in a release of CO2 from the ocean – I read somewhere recently a figure of ~60ppm CO2 release for a 1ºC temperature rise.
So the question is, what is the net change in CO2 and net change in pH? Let’s assume that the net change in pH is a decrease of 0.1 (8.2 to 8.1) near the average change reported above (0.075).
The next question is – which is more of a problem for corals etc. – pH or temperature? – (OK, so it is probably the combination, but bear with me)
In surface waters the carbonate ion is at supersaturating concentrations. However, as ocean pH falls, so does the concentration of this ion which makes it less available for reef formers (that want to lay down calcium carbonate). This is one of the main ‘problems’ cited by the media in reporting ocean acidification.
Another thing to consider is that calcium is also supersaturated (and highly so). Now calcite (calcium carbonate) is more soluble at lower pH, which would be a problem, but it is also less soluble at higher temperatures. Given that increases in CO2 should be accompanied by increases in temperature (if climate alarmists are to be believed) is it possible that if temperature has more of an effect than the pH change, the worst effects as far as ease of CaCO3 precipitation are concerned, could cancel each other out?
So which would win out in terms of effect – the 0.1 unit decrease in pH or say a 1ºC increase in temperature?
“”” Bill D (22:56:13) :
George E. Smith (14:08:20) :
1. “” foinavon (13:02:16) :
George E. Smith (12:07:00)
saw tooth; and that suggests to me that the southern CO2 uptake, is likely more ocean related, than land plant growth.
So you see, I was not trying to be smart alecky; but hinting that the waveform isa clue to the mechanism.
But as I said, if you took it as frivolous comment on your post please accept my apology; it wasn’t intended that way at all.
George\
George:
The problem is here that we should not just be looking at time series that and guessing about plausible explanations. Scientists have long had reasonably good estimates of terrestrial photosynthesis. More than forty years ago they did all of the calculations and found that the seasonal dynamics of atmospheric CO2 match the changes in seasonal changes in photosynthesis and respiration of terrestrial vegetation (and respiration including decomposers like bacteria and fungi). Moreover, no one (published paper) cites credible scientific evidence for an alternative explanation, such as one related to the oceans. “””
Bill; I believe you may have misunderstood my position.
There is no way that I am challenging the plant photosynthesis explanation for the sawtooth cyclic variation of the ML CO2 data; In fact I thought my “seat of the pants” description of how such a saw tooth cyclic variation could arise from such processes, clearly supports the notion that the northern hemisphere plant growth cycle creates that sawtooth data.
But if you look at the three dimensional CO2 data; that being the long term CO2 variation from the North Pole to the South Pole, you see that the ML amplitude of around 6ppm P-P, grows to about 18ppm P-P at the North Pole. (A contact at Scripps in La Jolla, who is a CO2 specialist says it is 18 ppm). But as you move south from ML, the ampliude diminishes greatly and eventually reverses phase; which is to be expected since the southern hemisphere seasons are six months out of phase with the northern ones. Once the phase has reversed, the amplitude never grows very much at at the South pole it is only of the order of 1 ppm P-P and maybe less; and based on the NOAA plot I have it is no longer saw tooth in shape either, but is a much more symmetrical looking waveform. From the graph I have it looks double humped, suggesting that part of the Nothern cycle phase is showing through the southern hemisphere cycle, so there is almost a doubling of the frequency of peaks. It’s abit ragged to describe as sinusoidal.
In any case my suggestion simply was that at the south pole, and in fact for latitudes below around -40 it looks like that, and what may be causing that is simply the seasonal variation in the temperature of the southern ocean; that being the ocean that surrounds Antactica; not the entire southern hemisphere.
What is a mystery to me, is that the largest cyclic amplitude (18ppm) occurs right at the North Pole, where there is no land plant growth of any kind. That leads me to query whether there is significant ocean photosynthesis going on in whatever open waters there are in the arctic (presumably in Spring/Summer), or whether this is the northern forests still able to affect the atmospheric CO2 as far north as the North Pole.
I’m not challenging in any way, what the common wisdom is on the causes of the annual cycling of atmospheric CO2; and I think the sawtooth waveform at ML is a fairly clear indication that such photosynthesis processes are causing that. On the other hand, I would expect ocean surface temperature variations would follow more of a sinusoidal waveform over the year simply from the geometry of the sun arrangement.
The pole to pole assymmetry of the atmospheric CO2 is one of the oddest global phenomena I am aware of
SImon Evans, circulatory ocean currents are typically 3-5 knots whereas atmospheric currents are an order of magnitude or so greater. A “back of the envelope” expectation might then be that ocean mixing would take around 10-20 times longer than atmospheric mixing.
I can see an argument that vertical mixing in the oceans would be much slower because it has an inherently stable temperature gradient whereas the atmosphere has an inherently unstable temperature inversion structure in many places.
That rather begs the question of whether vertical mixing is necessary to neutralise acidity given coastal waters and land runoff.
Simon Evans,
The only comments I have made about mixing speeds of the oceans have been in reference to the empirical turnover as seen by ENSO events, just as in my response to you. If you believe I have said otherwise, feel free to point to a specific quote.
So, please stop making things up – because I am attempting to have a serious discussion here.
Mary Hinge
I accept your mild correction but why does nobody take up my Cuba conundrum question? Is it perhaps because I’m right? You can argue chemistry and biology all night: Now we have acidity, UV, light, temperature and heaven knows what other stresses BUT all of those changes are present in Cuba too. The difference clearly seems to be due to human activity near the coast. This is very well acknowledged by the experts studying the coral reefs there. One quote i saw in the NY times from a scientist was that it was “like going back 50 years in time”. It just seems to me you are all missing the point for the sakes of defending the policy rather than the science. Do you realize just how much raw sewage is thrown in the sea replete with industry chemicals, fertilizers and female hormones, or how much fishing boats damage the coral? The very slight change in sea surface temperature has not even happened for at least 5 years. Most increase in the anomaly also actually comes from increased minimum temperatures, while maximums are roughly the same. Most of this tiny temperature change even happens in the north, not the tropics. Do these tiny alterations really lead to such an enormous die-off? Just bear in mind how important it is to get this right. Yes we need extreme focus on environmental issues but we absolutely need to do the right thing for the right reasons.
In the “calculation” method of determining ocean ph, is dissolved organic carbon included? I haven’t found a clear explanation of the practical definition is between “inorganic” and “organic” carbon, but maybe its along the lines of the difference in the chemical composition of calcite/argonite.
I’ve discovered that HOT “bottle extraction” data has no dissolved organic carbon record from 1989 through 2002.
http://hahana.soest.hawaii.edu/hot/hot-dogs/bextraction.html
New methods were tested during 2002 for organic carbon, and measurements were recorded from 2003 onward.
http://hahana.soest.hawaii.edu/hot/reports/rep_y4.pdf
I’ve been researching methodologies that determined ocean ph, and it seems that there have been and still are several methods with varying degrees of accuracy, with a history of inaccuracy. Here’s just one example of that
http://globalecology.stanford.edu/SCOPE/SCOPE_16/SCOPE_16_1.5.07_Takahashi_271-286.pdf
In 1992 spectrophotometric techniques were tested and ph values began to be recorded, shown on the “bottle extraction” site referenced above. It is claimed to be a very accurate methodology.
So dissolved organic carbon appears to have not been measured till the spectrophotometric method began in 1992. Looking at the HOT ph graph, it is obvious there is a disconnect between the “calculated” and “measured” ph data, starting when the “measured” data begins.
Was the pre-2002 data too high? Without that data, what would be the trend using both “calculated” and “measured” data? Offhand looks to me like there would no downward trend, or a small number approaching the error of measurement.
What is a mystery to me, is that the largest cyclic amplitude (18ppm) occurs right at the North Pole, where there is no land plant growth of any kind. That leads me to query whether there is significant ocean photosynthesis going on in whatever open waters there are in the arctic (presumably in Spring/Summer), or whether this is the northern forests still able to affect the atmospheric CO2 as far north as the North Pole.
George my interpretation is as follows:
Here’s the monthly data for 2007 from Point Barrow.
388.75 389.57 389.96 389.95 390.43 388.22 380.15 373.23 375.23 381.08 385.86 389.11
You can see that the CO2 concentration starts to drop in June just when the seaice starts to open up, exposing cold water which has been isolated from the atmosphere for about 6 months. Under those conditions you’d expect a rather rapid absorption of CO2, as observed. As you can see the CO2 starts to increase in October and stabilizes by December the same period during which the seaice closes back up. Point Barrow is at the coast and so is influenced by the periodic exposure of the cold water, the South pole on the other hand is far from the coast and influenced by katabatic flow so isn’t subject to the same effects.
Forgot to include the ph graph url in my last:
http://hahana.soest.hawaii.edu/hot/trends/trends.html
(select ph comparison)
Following up on the HOT ph graph to determine whether the early data could have been too high to accurately reflect ocean changes due to atmospheric CO2,
(ph graph)
http://hahana.soest.hawaii.edu/hot/trends/trends.html
(2003 article)
http://www.nature.com/nature/journal/v424/n6950/full/nature01885.html
“Here we analyse a 13-year time series of oceanic carbon dioxide measurements from station ALOHA in the subtropical North Pacific Ocean near Hawaii4, and find a significant decrease in the strength of the carbon dioxide sink over the period 1989–2001. We show that much of this reduction in sink strength can be attributed to an increase in the partial pressure of surface ocean carbon dioxide caused by excess evaporation and the accompanying concentration of solutes in the water mass. Our results suggest that carbon dioxide uptake by ocean waters can be strongly influenced by changes in regional precipitation and evaporation patterns brought on by climate variability.”
It appears that the “calculated” ph (although I am still in the dark as to exactly how ph was “calculated” by HOT from 1989 – 2002) may have been too high, influenced by natural variability.
I have some some documentation on how ph is “calculated” at least in 2006:
http://hahana.soest.hawaii.edu/hot/methods/dicalk.html
“(DIC) measured using a Single Operator Multi-parameter Metabolic Analyzer (SOMMA) … Total (titration) alkalinity (Talk) was determined using the modified Gran titration method… ”
Apparently it is possible to calculate a ph from basically from those two values. Normalizing and buffer factors are also required, and it seems all this gets quite complex and maybe a tad arbitrary. Of course,
http://www.bios.edu/Labs/co2lab/research/IntDecVar_OCC.html#tab2
“The anticipated rate of change surface ocean CO2 due to the accumulation of anthropogenic CO2 in the atmosphere and the surface ocean buffer factor (assuming that near-surface waters in the subtropical gyres have residence times long enough to equilibrate entirely with the anthropogenic perturbation in atmospheric CO2) can be theoretically calculated.”
I still don’t think I am way off on my suspicions that the HOT ph graph reflects “predicted” change. Set out to prove something and sooner or later you’ll find a way to do it.
Simon Evans (11:52:02) wrote:
“Steven Goddard,
“As Chris J has said above, anyone who’s followed this thread will be able to figure out who has been talking nonsense, so I rather think it pointless for either of you to keep making the claim.”
The exasperation level is getting high here, and shows no sign of resolution. And yet this dispute, or a large part of it, could easily be resolved if there were an acceptable referee who could make a ruling on it. How about an ad hoc panel of presumptively neutral and high-status chemists + geologists, chosen at random from officials or past officials of their scientific societies? This could be useful in resolving–or at least clarifying–other disputes on this site, and maybe other sites too.
Steven Goddard (17:53:30) :
Simon Evans,
The only comments I have made about mixing speeds of the oceans have been in reference to the empirical turnover as seen by ENSO events, just as in my response to you. If you believe I have said otherwise, feel free to point to a specific quote.
So, please stop making things up – because I am attempting to have a serious discussion here.
I am referring to your implication that observed ocean circulation expedites mixing to the extent of allowing the sea bed to buffer CO2 uptake at a fast enough rate, as indicated in these posts:
Steven Goddard (06:50:57) :
One of the arguments being propagated is that low mixing rates between shallow and deep water prevents pH buffering. However, we know that under normal Pacific Ocean conditions, cold deep water is continuously dragged to the east up the thermocline along the South American Coast, and is replaced by warm water sinking in the mid-Pacific. Under La Nina conditions this becomes even more exaggerated.
Steven Goddard (22:34:02) :
Chris J,
The point you are missing about the ocean system is that it contains large amounts of CaCO3 which buffer the alkalinity. Any push towards lower pH causes CaCO3 to dissolve, bringing the pH back up again. That is one reason why 5.2pH or less rainwater can continuously fall in the ocean, without any change in ocean pH. BTW – If ocean water did not circulate efficiently (as some have claimed) there would be an acidic layer near the surface, due to the rain. Instead, we find that pH decreases with depth.
Steven Goddard (09:04:15) :
Simon Evans,
Think about your last post.
The IPCC is claiming a much accelerated rate of acidification over the remainder of the century. How can CO2 absorption be slowing down and accelerating at the same time?
Secondly, as I have pointed out repeatedly, the existence of La Nina is proof of the rapid interchange of deep and shallow water in the Pacific. Where do you think the cold water came from?
The point is crucial. All discussion of rainwater falling on limestone, etc. etc., is moot if the buffer of the ocean floor is not rapidly exposed to the increasing CO2 concentration. It is not disputed that eventually the buffer would do its stuff, but if the current pace of CO2 increase exceeds the rate of the buffer then there is a change in the system, which is not discounted by the fact of atmospheric CO2 concentration having built to higher levels before at a much slower pace.
Another poster mentioned tritium traces which, as I’ve already said, indicate that ocean mixing to depth is far from ‘rapid’ on the time scales that are of concern in respect of the pace of acidification. In terms of CO2 mixing, see the following paper:
http://www.sciencemag.org/cgi/content/abstract/305/5682/367
– which found that 50% of anthropogenic CO2 is held in the top 400 m despite this making up only about 10% of the ocean volume. Most of the deep waters, especially those 1 km + deep, have yet to receive any anthropogenic CO2.
Waving your hand at ENSO upwelling doesn’t cut it. You might want to believe that the oceans mix fast enough for the buffering to keep pace, but the evidence tells us this is not so.
Simon Evans (04:42:45)
“El Nino also drastically reduced the amount of carbon dioxide this ocean region adds to the atmosphere. Unlike most parts of the world’s oceans, the equatorial Pacific is normally a major contributor to atmospheric carbon dioxide due to the carbon-dioxide-rich deep ocean waters brought to the surface here and the relatively low levels of biological activity.
The researchers calculate that the amount of carbon dioxide released to the atmosphere by the equatorial Pacific during the year of El Nino conditions was 700 million metric tons of carbon less than the previous year. This is equivalent to half of the United States’ total annual carbon dioxide emissions from fossil fuel burning. ”
http://svs.gsfc.nasa.gov/stories/elnino/press.html
K = Ka1/Ka2 = [HCO3-]^2 / [H2CO3][CO32-]
Pete D, try out this argument:
pKa = pH at which an Acid is exactly one half dissociated. In other words, at pKa, concentration of Acid = concentration of Conjugate Base formed from the Acid. They are “half and half”, existing in a ratio of 1:1.
pKCarbonic Acid/H2CO3 = 6.1
Therefore, at pH of solution = 6.1, [H2CO3] = [HCO3]. In other words at pH = 6.1, H2CO3 has exactly half-dissociated to produce an equal concentration of HCO3 – and it will stay exactly half-dissociated as long as pHsoln. = 6.1.
But at pHsoln. greater than 6.1, H2CO3 is more than half-dissociated. In other words, as the pH of the total solution increases, decreasing total [H+], existing H2CO3 more readily donates a proton H+, and so as to also produce more HCO3-.
Such that, [HCO3] >> [H2CO3]
Now looking at your equation, K = Ka1/Ka2 = [HCO3-]^2 / [H2CO3][CO32-]
For H2CO3 at pHsoln. > 6.1, [HCO3] > [H2CO3]
Therefore, [CO3] must increase in order to keep K constant when more H2CO3 is added to the solution, again, because any added H2CO3 at pHsoln > 6.1 will end up more than half-dissociated. Effectively, more HCO3 is added to the solution than H2CO3 at any pHsoln. > 6.1.
So for every addition of H2CO3 to a solution of pH > 6.1, in particular by increasing dissolved CO2, [CO3] must increase – in order for K to remain constant.
Therefore, in the Oceans, where pH = 8.1, addition of more dissolved CO2 must increase CO3.
Imo, once again, when more H2CO3 is added to a solution of pH > 6.1, it is simply not possible to get more net H2CO3 formed/added than HCO3 formed, because at these pH’s, H2CO3 more than half-dissociates, so more HCO3 is formed net than H2CO3 is increased.
Therefore, by equation K, CO3 must increase net to keep K constant, regardless of the “strength” of equation 2 in tending to form HCO3 from CO3 and H.
That’s what K says [to me], in solutions of H2CO3 whose pH’s are > 6.1.
maksimovich (06:01:09) :
Simon Evans (04:42:45)
“El Nino also drastically reduced the amount of carbon dioxide this ocean region adds to the atmosphere. Unlike most parts of the world’s oceans, the equatorial Pacific is normally a major contributor to atmospheric carbon dioxide due to the carbon-dioxide-rich deep ocean waters brought to the surface here and the relatively low levels of biological activity….
I’ve added some bold! Besides which it’s rather obvious, isn’t it, that CO2-rich waters upwelling will increase the acidification pressure at surface levels and decrease the exposure of CO2 to the sea floor carbon buffer? How on earth is the observation of ENSO behaviiour supposed to answer the point that ocean floor buffering is globally a very slow process whilst near-surface CO2 absorption is developing rapidly?
J Peden, take the partial derivatives and I obtained this equation:
d( [CO3=] ) = (K1 * K2 / [H+]^2 * ( d( [H2CO3] ) – ( [H2CO3] / 3 * [H+] ) * d( [H+] )
In seawater ballpark values are:
[HCO3-] 1.86E-03
[CO3=] 1.20E-04
[H+] 1.62E-08
[H2CO3] 2.00E-05
K1 1.45E-06
K2 1.09E-09
So [H2CO3] / 3 * [H+] = 411
And K1 * K2 / [H+]^2 = 5.97
So an increase in acidity has 400 x the impact of an equivalent increase in dissolved CO2 and therefore forces carbonate lower. This is amplified further by the high degree of dissociation of H2CO3 in seawater.
This was the calculation I was going to use to show J Lo the error of his ways but instead it convinced me I should do the math next time before I open my mouth!
J Peden –
You are confusing yourself. Use the equilibria and work out the algebra.
If you start with the values listed by Alan Wilkinson (16:15:09) and increase the amount of dissolved CO2 by 10% (by increasing [H2CO3] to 2.20e-5 M), you get an increase in [H+] to 1.79e-8 M (pH = 7.75 as opposed to the initial pH = 7.79). This is accompanied by a negligible increase in [HCO3-] (because it is so high to begin with), but also by a significant decrease in [CO3=] from 1.20e-4 to 1.09e-4. Alan is right about doing the math. Equilbrium for multiprotic acids in a buffered system can be difficult to think about without doing the math!
Alan Wilkenson:
Yes, I understand that this is “their” argument – “increase in acidity” forces H + CO3 to the net formation of HCO3 with a decrease in CO3 – but I don’t see how they overcome mine, that K = Ka1/Ka2 = [HCO3-]^2 / [H2CO3][CO32-] must remain constant, and when adding CO2/H2CO3 to solution at pH > 6.1, more HCO3 is formed than H2CO3 results, meaning [CO3] must increase if K is to remain constant.
Another wrinkle from http://chimge.unil.ch/En/ph/1ph67.htm, slightly modified, i.e. H3O to H3O-1 and H3O-2, and adding 1] and 2] as notations:
pH doesn’t change regardless of Carbonic Acid concentration.
“Their” argument is that with the addition of CO2/H2CO3, H3O-1/”acidity” increases ~ “a lot”, causing the H3O-2 component to combine with CO3 so as to decrease [CO3], also because pKa of HCO3 = 10.3 [btw, which is nothing new to the interactions].
Still, if pH doesn’t change, “their” argument seems to make sense – increased H has to go somewhere – except that it contradicts the constancy of K, where, according to my argument, [CO3] must increase if CO2/H2CO3 is added at pHsoln > 6.1.
So what happens to the added H3O-1 instead of acting to decrease [CO3] net, which allows pH and K to remain constant, and [CO3] to increase net as per K?
I say it just forms H2O:
H3O + OH = 2H2O
In other words, I essentially don’t care about the extra “acidity”/H+ – unless it results from a source of acid other than CO2/H2CO3. I’m saying K must remain constant, so that the extra H from H2CO3 must simpy form H2O – that is, enough to keep pH constant, while allowing a net increase in CO3.
Also, imo, “their” argument also seems to state that decreasing CO2/H2CO3 in solution increases CO3.
Equilbrium for multiprotic acids in a buffered system can be difficult to think about without doing the math!
Thanks, Pete, I might be wrong. But right now I don’t see how “the math” avoids the math problem that K = Ka1/Ka2 = [HCO3-]^2 / [H2CO3][CO32-] presents, given that at pHsoln > 6.1, adding H2CO3 results in more HCO3 formed net than H2CO3 remains after its addition – HCO3 increases more than H2CO3 – since at pHsoln > 6.1, H2CO3 is more than half dissociated, and likewise for any more added H2CO3, making the net increase in [H2CO3] necessarily more “neglible” than the increase in [HCO3]. So that to keep K constant, [CO3] must increase.
This is a math problem, too. Maybe these “neglibles” don’t really count in calculating or describing [CO3], but K says they do. Instead, do we just ignore K?
J Peden – I do not ignore K, but K is simply a relationship between Ka1 and Ka2 that helps to show the effect of raising one concentration. It is much clearer if you write down the equations and do the math yourself as you are pretty confused as to how acid-base equilbria are acting in this system (this is not to demean you in any way!). Or ask a chemist or chem eng to show you!
J Peden,
Your calculation for of the ratio K1/K2 = [HCO3-]^2/{[H2CO3][CO3=]} is fine. I think the point that is confusing you is that, since the concentration of HCO3- is so high an increase of X in [H2CO3] results in only a proportionally small increase in HCO3-.
For example, @ur momisugly 35 ppt, 1 atm, 25 C, 2300 ueq/kg TA (standard sea water) you’ll get these concentrations for DIC species at pHsws = 8.05, 7.95, 7.85 (K1 and K2 from Dickson and Millero, 1987; K2 for HSO4- from Dickson1990):
All conc. in umol/kg
pHsws = 8.05
CO2* = 10.79
HCO3- = 1761.60
CO3= = 219.03
pHsws = 7.95
CO2* = 14.28
HCO3- = 1851.07
CO3= = 182.82
pHsws = 7.85
CO2* = 18.73
HCO3- = 1928.75
CO3= = 151.31
For all sets you get the same K1/K2 = 1312.71. From pHsws = 8.05 to pHsws = 7.85 the concentration of CO2* increases by only 7.94 umol/kg while HCO3- increases by 167.14 umol/kg. However, CO2* increases by 74% while HCO3- only increases by 9%.
Your calculation was fine, but your reasoning of the effects of an increase in CO2* on the rest of the system was off, having not performed the calculations.
Well, there’s really been a whole lot of discussion about nothing here hasn’t there. The chemistry works just as expected, and is easily replicated at whatever set of conditions one likes. It’s a bit perplexing that it’s taken so much ‘debate’ to get to this point, but at least we got here.
Also, @ur momisugly Alan Wilkinson: good on ya. We need more folks like yourself.
Best,
Chris
Chris J:
Your calculation was fine, but your reasoning of the effects of an increase in CO2* on the rest of the system was off, having not performed the calculations.
Thanks, Chris. Maybe I’ll see if I can make the calculations using H2CO3 as the input, instead of specifying pH then calculating the species – as it appears you might have done? – “you’ll get these concentrations for DIC species at pHsws = 8.05, 7.95, 7.85”
And, again just shooting from the hip, another one of my problems is that looking at your pH calculations, they are all too low, at least if you use the H.-H. calculation as per human acid-base chemistry where [H2CO3] can be ignored, change in [CO2] is often the culprit/driver, and:
pH = 6.1 + log [HCO3]/[dissolved CO2]
But I’ll give it a rest!
J Peden-
I think I see the source of your confusion…the H-H equation gives you pH at equilibrium. So you need to use the equilibrium calculations to determine [HCO3-] and [CO2] (or [H2CO3]) before you use the H-H equation. It doesn’t seem like you are doing the equilibrium calculations before you plug in your concentrations and just trying to rationalize what will happen. The other complication is that at a pH~8.1 you are right between the pKa of Ka1 (for H2CO3) and Ka2 (for HCO3-), so there is a significant contribution from each equilibrium to the concentrations of each species in solution. By focusing only on Ka1, you are neglecting the effects of changes in H+ on the concentrations in the second equilbrium equation. It really helps to do the math instead of shooting from the hip. You would save yourself a lot of time and understand things a lot better!