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Examining the impacts of ocean acidification

Posted on 17 March 2011 by alan_marshall

The current debate on the connection between CO2 emissions and climate change has largely overlooked an independent and equally serious problem, the increasing acidity of our oceans. Last December, the respected  journal “Oceanography” published projections (see graphic below) for this rising acidity, measured by falling pH [i], through to the end of the century [ii]. In 2095, the projected average ocean surface pH is 7.8, and lower still in the Arctic Ocean.

Fig 1: Ocean surface pH - historical values and projected future values based on current emission projections.

CO2 in the atmosphere has increased from 278 ppm in pre-industrial times to 390 ppm today. During this time, the amount of CO2 dissolved in the ocean has risen by more than 30% [iii], decreasing the pH of the ocean by 0.11 units. As with CO2 and global warming, there is some lag between cause and effect. That means that, even if all carbon emissions stopped today, we are committed to a further drop of up to 0.1 units.

The close relationship between CO2 in the atmosphere, CO2 dissolved in the ocean, and the effect of the latter in falling pH, is illustrated by the graph [iv] below:

Fig 2: Annual variations in atmospheric CO2, oceanic CO2, and ocean surface pH. Strong trend lines for rising CO2 and falling pH.

CO2  dissolves in water to form carbonic acid. (It is worth noting that carbonic acid is what eats out limestone caves from our mountains.) In the oceans, carbonic acid releases hydrogen ions (H+), reducing pH, and bicarbonate ions (HCO3-). 

CO2 + H2O => H+ + HCO3-     (1)

The additional hydrogen ions released by carbonic acid bind to carbonate ions (CO32-), forming additional HCO3-.   

H+ + CO32- => HCO3-     (2)

This reduces the concentration of CO32-, making it harder for marine creatures to take up CO32- to form the calcium carbonate needed to build their exoskeletons.

Ca2+ + CO32- => CaCO3   (3)

The two main forms of calcium carbonate used by marine creatures are calcite and aragonite. Decreasing the amount of carbonate ions in the water makes conditions more difficult for both calcite users (phytoplankton, foraminifera and coccolithophore algae), and aragonite users (corals, shellfish, pteropods and heteropods).

The photo below left shows healthy specimens of calcifying phytoplankton Gephyrocapsa oceanica. The photo below right shows the damage to the same creature under conditions expected by the end of the century.

         

Fig 3: Healthy phytoplankton; same species with malformed shell plates as a result of damage by seawater with simulated end of century chemistry.

Source: Nature, Reduced Calcification of Marine Phytoplankton in Response to Increased Atmospheric CO2, Issue 407 p.364 -367

It is often said that a picture is worth a thousand words.

Research in the Southern Ocean provides evidence that the formation of foraminifera shells is already being affected. Even though these creatures use calcite, which is less soluble than aragonite, there are already clear signs of physical damage. According to Dr. Will Howard of the Antarctic Climate and Ecosystems Cooperative Research Centre in Hobart, shells of one species of foraminifera (Globigerina bulloides) are 30 to 35 percent thinner than shells formed prior to the industrial period. [vi]. The photo below left shows a pre-industrial exoskeleton of this species obtained from sea-floor sediment. The photo below right shows a exoskeleton of a live specimen of the same species obtained from the water column in the same area in 2007. These stunning images were obtained using an electron microscope. (An interview with Dr. Howard was broadcast on the Catalyst television program). [vii] What is staggering is the amount of erosion in the right image compared to the left. The right sample look porous with larger holes and a 10-fold increase in their number. These and creatures like them are at the base of an ocean food chain, and they are already seriously damaged. If they are lost, it is not just biodiversity we are losing, but our food supply as well.

       

Fig 4. Pre-industrial and current samples of Globigerina bulloides from same location. Latter shows extensive erosion with a ten-fold increase in holes.

Source: Australian Broadcasting Corporation, Ocean Acidification – The Big Global Warming Story, 13 September 2007

The implications of all of this are disturbing. For corals to absorb aragonite from seawater, the latter needs to be saturated in this mineral.

Now a report from NOAA scientists found large quantities of water undersaturated in aragonite are already upwelling close to the Pacific continental shelf from Vancouver to northern California [v]. Although the study only dealt with the area, the authors suggest that other shelf areas may be experiencing similar effects. 

For corals like those in Australia’s Great Barrier Reef, the outlook is grim. They are threatened with destruction on two fronts, both caused by CO2 emissions. Not only do increased ocean temperatures bleach coral by forcing them to expel the algae which supplies them with energy (see photo at left) [viii], but increased ocean CO2 reduces the availability of aragonite from which reefs are made.

It is time to wake up. Our planet is dying. I urge you to find the time to view a 20 minute documentary on the problem of ocean acidification produced by the international Natural Resource Defence Council. Simply go to: www.acidtestmovie.com

Fig 5. Coral killed by above average ocean temperatures.



References and Notes

   [i]  pH is a measure of the acidity or alkalinity  of a solution. It uses a negative logarithmic scale where a decrease of 1.0 units represents a 10-fold increase in acidity. In   their natural state prior to industrialization, the oceans were slightly alkaline with a pH of 8.2 (see reference iii). Pure water has a pH of 7.0.
   [ii]  Feely R., Doney S., Cooley S. (2009). Present Conditions and Future Changes in a High-CO2 World. Oceanography 22, 36-47
   [iii]  Australian Antarctic Division, Ocean Acidification and the Southern Ocean, available at http://www.aad.gov.au/default.asp?casid=33583
   [iv] Feely, Doney and Cooley, op. cit, using Mauna Loa data from the US National Oceanic and Atmospheric Administration and Aloha data from the University of Hawaii.
   [v] Feely RA, Sabine CL, Hernandez-Ayon JM, Ianson D, Hales B (June 2008). Evidence for upwelling of corrosive "acidified" water onto the continental shelf. Science 320 (5882): 1490–2, available at http://www.sciencemag.org/content/320/5882/1490
   [vi] Inter Press Service, Acid Oceans Altering Marine Life, available at http://ipsnews.net/news.asp?idnews=46055
   [vii] Australian Broadcasting Corporation, Ocean Acidification  – The Big Global Warming Story, downloadable at http://www.abc.net.au/catalyst/stories/s2029333.htm
   [viii]  Great Barrier Reef Marine Park Authority, What is Coral Bleaching?, available at http://www.gbrmpa.gov.au/corp_site/key_issues/climate_change/climate_change_and_the_great_barrier_reef/what_is_coral_bleaching

Note: this blog post has been used as the Intermediate Rebuttal to "Ocean acidification isn't serious". The short URL for this rebuttal is http://sks.to/acid

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Comments

Comments 1 to 48:

  1. Great post, overlooked issue. On my way to watch the vid now. Thanks.
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  2. There is one passage from this long article that I think is particularly valuable, something we can use as our basic message as we focus public attention on this issue. That is:

    "These and creatures like them are at the base of an ocean food chain, and they are already seriously damaged. If they are lost, it is not just biodiversity we are losing, but our food supply as well."

    That people will understand, that underlines how important this really is.
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  3. Good job. But there is another reason to worry. Carbon dioxide saturate water in our polar area will contribute to global cooling. That is why the ice is growing astronomically at the South Pole and prior to the BP breech it had been growing for two years in the Arctic. The BP methane, in the main, stayed in the northern hemisphere until in reached the Arctic, then it dives and goes to the South Pole and it oxidize along the way ending up at CO 2 It takes 22 degrees F to freeze carbon saturated water and the Souith Pole can get it there. Once frozen it is then 60 times stronger than regular ice. The north pole with the aid of hydrate cold seeps can also.

    We are between the proverbial devil and the deep blue sea. The heat is killing our oceans and speeding up hydrate dissociation, and therefore methane emmissions which are the main culprit in global warming, because they release heat to the water tht used to hold them when they transverse the solid to gaseous state, but my theory is that it is global cooling that will win in the end, unless we can get the oil and gas industry out of our seas, which is needed but is highly unlikely to happe.

    Yes I agree the planet is dying and doing so very quickly. My theory is it is also shaking apart from hydrate action as well.

    I have read discussion between hydrate specialist and Japanese scientists discussing hydrates in the trench where the earthquake split the earth open almost five years ago.

    Andrea Silverthorne
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    Moderator Response:

    [DB] For the 2nd time tonight I have to say: Huh?

    I know your words are English but collectively they do not parse.

  4. This reads like science fiction. Can you please substantiate:

    "Carbon dioxide saturate water in our polar area will contribute to global cooling." Huh?

    "ice is growing astronomically at the South Pole" it is?
    The reason for overall decline in artic ice than was??

    If its methane driven, then why dont we see it? (Noting the fossil methane has no C14 whereas biogenic does). If anything oil/gas production has reduced fossil methane in atmosphere by reduction in natural losses (but of course our burning of fuel massively increases CO2).

    "methane emmissions which are the main culprit in global warming" They are? Where is your data to support that? (Try IPCC WG1 for actual contributions of each GHG).
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  5. You might like to read Realclimate on methane eg
    here and and especially here. Climate looks grim but lets understand the real reasons.
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  6. Dr Gretchen Hoffman (UCSB) warned of this problem in 2009 when she described pteropods (Thecosomata) as “chips of the sea” because they were so widely consumed by fish on which larger fish preyed and on which, ultimately, a billion humans depended for protein. Alan Marshall’s article is a good reminder of the dangers posed by ocean acidification.

    Frankly, I am somewhat shocked by acidification expected over the rest of this century (Fig. 1) If it develops, the gloomy prognosis in my article “No Chips, No Fish” (http://www.onlineopinion.com.au/view.asp?article=8934) will indeed be realised with disastrous effects on marine habitat and human diet. That outcome is exacerbated by the fishing industry’s penchant for over-fishing and destroying marine habitat.

    An example of this is the Newfoundland cod fishery, over fished until 1992 when no cod appeared. Cod did not return. The Canadian government closed the fishery. Nineteen years later, cod have still not returned in quantity, 40,000 jobs have been lost and a valuable food source has been destroyed.

    The prime threat of ocean acidification is the loss of plankton and other calcifying animals, creating a break in the food chain and loss of habitat, particularly that provided by coral reefs. Some argue that fish-farming can replace the effects of open water species depletion and that there is nothing to worry about. Anyone who has studied the extent of fish farms and the inputs required or their operating cost knows that this is wishful thinking.

    Clearly, if we do not stop CO2 emissions and overfishing, our days of dining on fish and chips will be numbered and a dish once considered the preserve of the working class because of its affordability will become a rarity enjoyed by the rich. Frankly, the prognosis is not good.

    scaddenp @ 4

    I think what andthorne is referring to is the possibility of methane released by melting clathrates creating anoxic conditions resulting in loss of marine species. My view is that marine species will be long gone before that occurs.
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  7. andthorne "the ice is growing astronomically at the South Pole and prior to the BP breech it had been growing for two years in the Arctic."

    This is complete nonsense, as any cursory look at either Cryosphere Today or NSIDC will demonstrate.

    As for the rest of your post, I'll say in chorus: uh?
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  8. I get so caught up in dealing with climate denier nonsense that it often slips my mind to work in an explanation of ocean acidification, but it's clear that I can't afford to let this issue slip away any longer. Thanks for the straightforward article.

    Couple of things, though.
    1) When I follow the note links, I'm directed to a forum I can't access instead of the footnotes on this page.

    2) Someone once got all pedantic and insisted that "ocean acidification" was a misnomer because oceanographers referred specifically to alkalinity, not pH, when talking about acidity of the seas; I remember from college chemistry that the two measures are not interchangeable. I take it that the "alkalinity only" thing is not really a hard-and-fast rule? All the public messages I've seen on CO2 and ocean acidification referred to pH rather than alkalinity.
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    Moderator Response: [DB] If you're referring to the last source note, the URL was truncated. Here's the full URL: http://www.gbrmpa.gov.au/corp_site/key_issues/climate_change/climate_change_and_the_great_barrier_reef/what_is_coral_bleaching. I'll look into fixing the original post at top as soon as I can (the linked references in the main body appear to be gremlined).
  9. No, I mean clicking on the Roman numerals in the article itself tries to direct me to a Skeptical Science Forum (with a *thread.php* in the url and everything), that I'm apparently not allowed to access. Also the links pointing towards notes iii and vi are not actually links in the article body.
    It's the same when I visit the Intermediate Rebuttal version of this post, I'm afraid.
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    Moderator Response: [DB] Should be all fixed. HTML anchors were all hosed, corrupting links. Had to rebuild the whole post. The Intermediate Rebuttal I'll have to kick up to John to fix.
  10. "Our planet is dying" I believe that this is a very excessive statement that should not be on this otherwise excellent web site.

    I invite readers to check the EPOCA blog (http://oceanacidification.wordpress.com/) for more recent and better documented general articles on ocean acidification and its effects on marine organisms and ecosystems.

    Note also that the Oceanography special issue referred to at the beginning of this post was published in 2009, not last year.

    Jean-Pierre Gattuso, coordinator of EPOCA
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  11. Here is another photo showing the damage to marine life we can expect to see if we do not act to reduce greenhouse gas emissions. As you can see from Fig. 1 in the article, the projected end-of-century pH for all oceans other than the Arctic, under a business-as-usual scenario, is 7.8. In the Arctic along the coast of Siberia it gets down to 7.6. A recent study of the effects of sea water with pH of 7.6 was published on 7 March 2011 by The Age newspaper in Melbourne. As you can see from the photo below, the growth of sea urchin larvae under such conditions is very seriously impeded.

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  12. WheelsOC @ 9

    Yes, there are skeptics who think that the term ocean acidification is a misnomer. They argue that while the pH of the ocean remains above 7.0, the ocean is alkaline, and so it is. But as the references in my article explain, and as my above post (11) demonstrates, the ocean chemistry that supports marine life is compromised when conditions become less alkaline through rising emissions of CO2. It does not require blue litmus paper to turn red for biodiversity to be lost. I am happy to use the term "ocean acidification" as I am in the business of climate communication and this is the name by which the phenomenon is best known. In so far as dissolved CO2 increases the supply of H+ ions (see equation 1 in the main article), it moves the chemical balance further towards the acid end of the pH scale.

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  13. Hey Alan, Jean-Pierre Gattuso commented on your article. I've read a lot of his work in the scientific literature. I think he has a point, the planet won't die. Humans and many other species may, but not the planet.
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  14. gattuso @ 10 (and Rob Painting @ 13)

    Thanks for the link. It looks like a good site. I checked the latest article title "Ocean Acidifciation: The Acid Sea" published 16 March 2011, and I quote:

    Will organisms be able to adapt to the new ocean chemistry? The evidence from Castello Aragonese is not encouraging. The volcanic vents have been pouring CO2 into the water for at least a thousand years, Hall-Spencer told me when I visited. But the area where the pH is 7.8—the level that may be reached oceanwide by the end of the century—is missing nearly a third of the species that live nearby, outside the vent system. Those species have had "generations on generations to adapt to these conditions," Hall-Spencer said, "yet they're not there.

    So your own site suggests that conditions expected by the end of century will cause one third of species to disappear! I also refer you to the article “The Earth’s Sixth Mass Extinction May be Underway”, posted on this site on 9 March, with which I agree.

    I have been careful with my language, but I don’t regret using the words “the planet is dying”. Obviously I am not saying that all life is under threat. What I am saying is that with the climate projected to warm by 4 degrees C, and ocean surface pH projected to fall to 7.8 by the end of the century, many species are threatened with extinction due to human negligence, threatening the capacity of the Earth to support its present population.

    In my article I included Dr Will Howard’s photos showing damage to Globigerina bulloides. This damage did not occur in simulated conditions, but in 2007 in ordinary Southern Ocean seawater. It doesn’t look very encouraging, does it?.

    I know many scientists, and some of my colleagues on this site, dislike emotive language. But I think it is rational to use language proportionate to the threat, and the threat we face is unprecedented in history.
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  15. Alan, I think the problem with the phrase 'the planet is dying' is that, while it is a reasonable way of describing the degree of biodiversity loss we are facing, it implies the end result of continuing down this path would be 'the planet is dead'... and that isn't going to happen. The changes we are making would result in a massive decline of human population, down to a level where we would no longer be making those changes, long before it would wipe out ALL life on the planet.

    Not an issue of disagreement on what is going to happen, but rather the implications of the particular turn of phrase. The planet is 'wilting', 'being poisoned', possibly 'decimated'... but not going to die and ergo not in the process of 'dying'.
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  16. Alan Marshall #14

    On the positive side, if the oceans are acidifing, then the surface layers (top 700m) are mainly involved.

    If the deep oceans were involved (700m - 3700m av depth) then the amount of dilution of the man made CO2 dissolved in this vast extra volume, would change the pH by an infinitesimal amount.

    If that conclusion seems logical, then transport of absorbed CO2 and heat energy to the deep oceans by deep mixing would be very limited and therefore the missing heat supposed to be down below 700m is not there either.
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  17. "I know your words are English but collectively they do not parse."

    Bot or human?
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    Moderator Response:

    [DB] Me or commentator #3? ;)

    #3 has posted similar comments here in the past; I've also seen comments of that ilk likewise posted on other climate sites as well. Infrequent, but there.

    My guess: Human

    .
  18. World ocean PH in 1875 ? It looks like Beck's curves for atmospheric CO2 !
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  19. Ken Lambert #16 - You assume that heat and carbonic acid disperse through seawater at identical rates?
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  20. FWIW, I was thinking of a response to Rob's comment on the planet-dying phrase, but I see that Alan's reply #14 matches my original interpretation of his words.

    On the pedantic side of language, andthorne's comment does indeed parse, but the tokens do not create a well-formed expression. :P

    Regarding Ken and CB, I'd be interested in seeing some math to support either position. It's conceivable that the upwelling of the deep ocean will, or is, providing something of a buffer, but it is not clear whether that is enough to prevent a large enough change in pH to dramatically change the nature of life in the oceans. Current trends indicate it is not.

    However, Ken's use of "if" is a bit off-putting. What do you mean "if"? Measuring pH is not difficult, and there exist records. We have measurements and basic chemistry that both tell us that the ocean is and should be becoming more acidic. It smacks of an attempt to cast doubt where there really isn't any.

    More acidic/less alkaline, they mean the same thing; let's not get hung up on the name. The general population believes that acids dissolve things, and that is what is happening. If you say the oceans are becoming less alkaline, it does not convey the meaning of what is really happening. Well, if does to those with a solid foundation in chemistry, but that isn't the majority of the audience. So, we have to deal with some backlash with the Dunning-Krugers when they learn that the actual pH is still technically on the alkaline side before they learn that alkaline water does in fact still dissolve the shell material, and that it dissolves it a lot more at 8.1 than it does at 8.2. A pH of 7.8 is downright frightening from an ocean food web perspective.
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  21. "ocean acidification" is no more wrong than discussing "warming winters".
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  22. @8 WheelsOC-
    In oceanography, alkalinity and pH are two distinct parameters.

    Alkalinity is essentially the measure of the buffering capacity of seawater. Usually in the case of ocean acidification we're talking specifically about carbonate alkalinity, which measures the amount of buffering provided by carbonate and bicarbonate ions.

    Rest assured that when oceanographers are talking about the acidity of the sea, we use pH just like everyone else.

    The confusion comes from the fact that seawater has a pH>7, so it can be described as alkaline- though that term is unrelated to the measure of alkalinity.

    As the seas take up CO2, they become less alkaline, but alkalinity isn't directly affected. Confusing enough? ;)

    FWIW, while we are concerned about the reduction in pH, the real concern is the impact that that reduction in pH has on CaCO3 saturation. Even under pH below 7.8 many calcifiers do just fine so long as carbonate concentrations are maintained. Unfortunately, that works well in an aquarium but doesn't happen in nature.
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  23. Ken, you're forgetting the significance of the biological pump and the the effects of depth/temperature on CO2 solubility. Unlike heat, the pH and dissolved inorganic carbon patterns aren't determined by the mixing depth or diffusion rates.
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  24. dhogaza at 03:40 AM, "warming winters" is the equivalent of " declining alkalinity".
    "Hotter winters" is a more appropriate comparison for ocean acidification.
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  25. Mike G,
    Thanks for the explanation. I recall some back of the envelope calculations that we could correct for extra CO2 by adding carbonate compounds to the ocean. They calculated that if we were to mine all of the cliffs of Dover, grind it up, and disperse it through the world's oceans, that would neutralise the extra CO2, but I can't recall whether that was at present levels of CO2 or a doubling, or what. In any case, no, that doesn't happen in nature, at least not at the rate required to accommodate the rate we are adding CO2.

    Ah, found it. Not exactly what I remembered, but the point remains.

    http://www.realclimate.org/index.php/archives/2009/10/an-open-letter-to-steve-levitt/
    Gavin's comment #9

    Gavin's link is broken, but likely is related to
    Ocean acidification due to increasing
    atmospheric carbon dioxide

    Page 37

    "To counteract the changes in acidity caused by
    today’s ocean uptake of roughly 2 Gt C per year (IPCC
    2001) would require roughly 20 Gt CaCO3 per year
    (Caldeira & Rau 2000), which, for a limestone layer
    100 m thick, would require the removal of roughly
    60 km2 each year."

    "Furthermore, limestone does
    not dissolve in surface waters, so additional processing,
    and energy, would be needed (Kheshgi 1995; Rau &
    Caldeira 1999)."

    and

    "Although the vast amounts of carbonate minerals needed
    may make this approach infeasible at the scale required to
    mitigate global changes in ocean chemistry, this approach
    is widely used by salt-water aquarists to promote coral
    growth in fish tanks. Thus, it might be possible to use
    alkalinity addition to save specific coral reefs (Rau &
    Caldeira 2002), but such ideas have never been tested in
    situ and therefore must be regarded as speculative."


    Speculative indeed.
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  26. CB,
    Regarding use of the term dying, IDK, but the P/T extinction event is often referred to as The Great Dying, and no one takes it to mean the planet became totally dead. No matter.

    Otherwise, yeah. Someone asked me if I thought climate change would lead to man becoming extinct. My reply was something to the effect that we are like cockroaches; it is very difficult to kill all of us. But, there may not be nearly as many of us afterward.
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  27. Thanks for giving this important issue some exposure.

    I would like to add that data for pH or carbonate saturation that are global averages tell one story, but some areas are far more susceptible to these acidification effects than others. Here are some interesting references:

    McNeil BI, Matear RJ (2008). Southern Ocean acidification: A tipping point at 450-ppm atmospheric CO2. Proceedings of the National Academy of Sciences (105:48; p.18860). http://www.pnas.org/cgi/content/abstract/105/48/18860

    Bernie D, Lowe J, Tyrrell T, Legge O (2010). Influence of mitigation policy on ocean acidification. Geophys. Res. Lett. (37:15; p.L15704). http://dx.doi.org/10.1029/2010GL043181 DO - 10.1029/2010GL043181

    McNeil & Matear (2008) show in what a short term timeframe significant ecological impacts can be anticipated in high latitude waters, with Southern Ocean "wintertime aragonite undersaturation ... projected to occur by the year 2030 and no later than 2038. Some prominent calcifying plankton, in particular the Pteropod species Limacina helicina, have important veliger larval development during winter and will have to experience detrimental carbonate conditions much earlier than previously thought, with possible deleterious flow-on impacts for the wider Southern Ocean marine ecosystem."

    And later, "Our results show wintertime aragonite undersaturation to potentially begin once atmospheric CO2 concentration reaches 450 ppm, which is the year 2030 using the IPCC IS92a scenario (Figs. 3 and 4). It must be emphasized, however, that the timeframe for atmospheric CO2 to reach 450 ppm could be earlier or later depending on the trajectory of future CO2 emissions. ... Early aragonite undersaturation is of particular concern for the zooplankton species comprising Pteropods, which form aragonite shells. Southern Ocean Pteropods comprise up to one-quarter of total zooplankton biomass in the Ross Sea (13), Weddell Sea (14), and East Antarctica (15), can sometimes displace krill as the dominant zooplankton (16), and dominate carbonate export fluxes south of the Antarctic Polar Front (17), and even organic carbon export (18)."

    Troubling to me is not only the ecosystem implication, but also that the Southern Ocean is a major carbon sink, and shell-building zooplankton is an important part of that.

    Bernie et al. (2010) deals with averaged global effects, comparing onset and severity of acdification problems to climate models and climate change mitigation scenarios. It notes that the Arctic will undergo changes faster than the paper predicts, that effects in coastal areas and at depth around the world are highly variable and not examined. The paper estimates that if with "aggressive mitigation" CO2 emissions peak in 2016 and decline at 5% per year to a low long-term value, the global average pH decline could be limited to 8.02, "roughly a doubling of current acidfication." However, without mitigation by 2100 the level would be 7.67 to 7.81.

    The Bernie et al. paper notes limitations of similar previous studies and that this is the first to study "acidification under a range of emissions scenarios and analyze what aspects ... have most impact on future acidification. The key feature of this study is the explicit relation of future pH to aspects of global climate change mitigation policy."
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  28. Ken Lambert @ 16

    As far as I know, the transport of absorbed CO2 to the deep oceans is included in the models. The fact that surface pH is decreasing indicates that CO2 is absorbed from the atmosphere faster than it can be transported to the deep oceans. The model developed by the US National Centre for Atmospheric Research (Fig 1.) projects an end-of-century surface pH of 7.8, but it presumes a business-as-usual emissions trajectory.

    On the other hand, if the world urgently makes serious efforts to constrain emissions, the outlook is not quite so bleak. The UK Department of Energy and Climate Change (DECC), in drafting the UK Climate Change Act of 2008, commissioned a consortium of experts led by the Hadley Centre to model the trajectory for ocean surface pH under their ambitious “2016 4% Low” scenario. If annual global emissions were to peak in 2016 (developed countries sooner, developing countries later), and then decline in line with the Global Commons Institute’s Contraction and Convergence formula, the atmospheric concentration of CO2, as a result of cumulative emissions, would peak around 2050. DECC projects that under this scenario that by 2050, "the biological pump and deep ocean transport of carbon" will remove CO2 from the upper layers of the ocean as fast as the upper layers absorb CO2 from the atmosphere, resulting in pH levelling off at 8.0. I agree with their reasoning. Once atmospheric CO2 peaks, ocean surface pH can be expected to stabilise, even though the ocean average pH will continue to increase until the atmosphere and ocean are in equilibrium.

    I am pessimistic about the chances of securing an international agreement that would see global annual emissions peak in 2016. Nevertheless, I am a supporter of the Contraction and Convergence solution, and believe we need to start focussing politicians on setting a target to limit ocean acidification. Copenhagen secured an agreement on a target of limiting global warming to 2 C. We need to determine what this corresponds to in terms of a decrease in ocean surface pH. If we are to attempt to stop pH from falling below 8.0, I suspect a 2 C warming is too high. This is something for readers may like to investigate.
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  29. Alan Marshall - We need to determine what this corresponds to in terms of a decrease in ocean surface pH. If we are to attempt to stop pH from falling below 8.0, I suspect a 2 C warming is too high

    IIRC this may be addressed on the FAQ section at EPOCA. Remember we are talking about 2°C of atmospheric warming, not the ocean. The decline in CO2 solubility from ocean warming this century is negligible. The effect on ocean stratification, on the other hand, could be dramatic.
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  30. Rob Painting @ 29

    I was not talking about a direct connection between atmospheric warming and ocean acidification. What I meant was that any projected emissions trajectory for CO2 that succeeds in keeping atmospheric warming under a given limit (currently 2 C) will also keep ocean surface pH above a limit. The correspondence between the two is therefore an indirect one, and does not take into account any change in the relative concentrations of CO2 and those greenhouse gases such as CH4 which do not contribute to ocean acidification.

    I still think the relationship is worth exploring, and that an internationally agreed target to limit ocean acidification is necessary.

    The FAQ section at EPOCHA is quite lengthy, Can you point me to the information you are referring to?
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  31. Bringing politicians up to speed

    Over the past year I have enjoyed some modest success in a personal campaign in which I have written to all 226 members of the Australian parliament. Using old-fashioned mailed letters, complete with graphics and references, I have sort to contribute to their understanding of the science of climate change. The above article had its origin in a letter to parliamentarians about ocean acidification. It can be viewed on my web site at www.climatechangeanswers.org/campaign/OceanAcidification.pdf. I have received around 20 letters from politicians in response, and many of these can be found under Feedback Received. For example, the Hon. Malcolm Turnbull MP, former environment minister and former leader of the Liberal Party of Australia, wrote saying “I agree entirely with your concern about this issue”. I would encourage readers in the USA to do what they can to inform their representatives, particularly those Republicans trying to “repeal laws of physics”.
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  32. Another video

    Just in case you missed the reference at the bottom of my article, I recommend interested readers view the 10 minute video form the Catalyst program showing damage to foraminifera. The link is www.abc.net.au/catalyst/stories/s2029333.htm.
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  33. Alan @ 30 - Sorry, my bad, misinterpreted your comment. Here's the FAQ page at EPOCA
    0 0
  34. Chris G, I wouldn't take 'the great dying' to imply that everything died either... just that alot of things died. However, 'our planet is dying'.... there is only one planet involved. Either it is going to die or it isn't.

    Anyway, purely a semantic argument. We all agree on what is happening, but apparently there are differing views of what that particular turn of phrase implies. It was apparently intended to mean, 'much of the life on our planet is dying' rather than 'our planet is becoming devoid of life'.
    0 0
  35. What scientific "foundation" has the claim: ” The implications of all of this are disturbing ...” ?

    Ocean acidification, Gattuso, 2010.:
    “Surface ocean pH is estimated to have decreased from approximately 8.25 to 8.14 between 1751 and 2004 and may reach 7.85 in 2100.”
    “Although changes in the carbonate chemistry are well known, the biological and biogeochemical consequences are much less well constrained for several reasons. First, very few processes and organisms have been investigated so far (research in this area only began in the late 1990s). Second, most experiments were carried out in the short-term (hours to weeks), effectively neglecting potential acclimation and adaptation by organisms. Third, the interaction between pCO 2 and other parameters poised to change, such as temperature , concentration of nutrients and light, are essentially UNKNOWN."
    “It is not anticipated that oceanic primary production will be directly affected by these changes in carbonate chemistry because most primary producers use carbon concentrating mechanisms that rely on CO 2. Note, however, that primary production of some species is likely to be stimulated.”
    “Note, however, that some calcifiers either do not show any response to increasing pCO 2 or exhibit a bell-shaped response curve with an optimum rate of calcification at pCO 2 values close to current ones and rates that decrease at pCO 2 values below and above the current values.”
    (...)
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  36. from your graphs it's obvious that co2 concentrations in the ocean are correlated with atmospheric co2 concentrations and that makes sense. you show the pH declining but are there other factors in ocean pH other than co2 concentration? what else could affect the ocean pH?

    also, the pictures of the differences in calcification (i think that is the right word) is obvious but are there measurements taken at specific reefs over time to measure this and is this also correlated with pH?

    i seem to remember a post somewhere linking the PDO to the pH cycles as well. can you provide a link to prove or disprove that?
    0 0
    Moderator Response: [DB] Perhaps it would be best if you would hunt down a link to this post to which you refer, then this could be discussed further.
  37. Arkadiusz Semczyszak @ 35

    You quote Jean-Pierre Gattuso, whom I respect. There are a variety of articles on the EPOCHA site. In the article published on 16 March, which I quote in comment 10, Hall-Spencer reports that “the area [near vents] where the pH is 7.8—the level that may be reached ocean-wide by the end of the century—is missing nearly a third of the species that live nearby, outside the vent system”. He points out that these missing species have failed to adapt, even though they have had thousand of years to do so. At least in this instance, Gattuso’s optimism about the “potential acclimation and adaptation by organisms” does not seem to be justified. A global loss of one third of species of calcifying organisms would have severe consequences.

    I find that disturbing.

    The projected end-of-century temperature rise of 4 °C under a business-as-usual scenario, coupled with an ocean surface pH of 7.8, will destroy almost all of our coral reefs. (Next to the tropical rainforest, they are the richest ecosystem on Earth. )

    I find that disturbing.

    When James Hansen gave his famous congressional testimony in 1988, atmospheric CO2 was still around 350 ppm. The danger of climate change was well understood even then. If politicians had heeded his warnings we would not be confronted with the crisis we are facing now.

    I find that disturbing.
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  38. garythomson @ 36

    In Fig 2 which you refer to, the increase in dissolved CO2 adequately explains the drop in pH. However, there are other factors that may contribute to ocean acidification. When sulphur dioxide (SO2) dissolves naturally in water, it forms sulphurous acid (H2SO3), not to be confused with the stronger sulphuric acid (H2SO4). However, much progress has been made in bringing emissions of SO2, responsible for “acid rain”, under control. The key to control of SO2 emissions in the US was a trading scheme similar to that now in use or being considered by nations in their efforts to control emissions of CO2. The latter is the bigger problem.

    The “differences in calcification” between current and pre-industrial Globigerina bulloides relate to specimens collected in the Southern Ocean, far away from any coral reef. As the photos came from a report on an Australian television science news program, I cannot tell you the latitude and longitude, nor the pH of the seawater in which the specimens were collected. I agree such information would be useful. All I can tell you at this point in time is that the damage has occurred in ordinary seawater, not a laboratory acid bath.
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  39. i should have done more homework on the links and the moderator's reply to my comments in #36 are valid. i found the link to the article in question. here is the link showing the pdo correlation with pH and it also suggests no correlation of calcification and pH. i can only read the abstract without a subscription so maybe someone has the full paper with the data. i did have access to the data on calcification and i graphed it below showing no correlation between pH and calcification. it should be noted that this was a lab experiment.



    this paper also suggests that there is no correlation with calcification and pH but instead dependent on CO2. although the R-squared of all these lab experiments were not strong in my viewpoint.
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  40. Pelejero's recent work strongly endorses the Anthropogenic component of oceanic acidifcation:

    "The anthropogenic rise in atmospheric CO2 is driving fundamental and unprecedented changes in the chemistry of the oceans. This has led to changes in the physiology of a wide variety of marine organisms and, consequently, the ecology of the ocean.

    This review explores recent advances in our understanding of ocean acidification with a particular emphasis on past changes to ocean chemistry and what they can tell us about
    present and future changes.

    We argue that ocean conditions are already more extreme than those experienced by marine organisms and ecosystems for millions of years, emphasising the urgent need to adopt policies that drastically reduce CO2 emissions."


    Apologies if this was already discussed. It's late & I'm tired.

    The Yooper
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  41. Gary Thompson @ 39 - just to clear up your confusion:

    1. The Pelejero 2005 study does not suggest the PDO is the cause of ocean acidification, rather that natural variations in pH (read deep ocean upwelling here) correlates with the PDO at that site. Where do you get the idea about calcification and pH?.

    2. As for Schneider & Erez 2006, you have that wrong too. They find that coral calcification correlates with carbonate concentration, not CO2. Increasing CO2 causes ocean pH to fall and carbonate concentration too. End result; more CO2 = very bad for coral.
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  42. garythomson @ 39

    Thanks for the links to these two papers.

    Regarding the graph of the lab experiment which plots calcification against pH, it is not clear to me what the context is. Specifically, you have not told us what is going on with CO32-, which as I will discuss below, is the critical parameter.

    The other paper (Schneider & Erez 2006) is the one that relates to the mechanics of ocean acidification. I quote from the abstract:

    "In all of these experiments, calcification (both light and dark) was positively correlated with CO32- concentration, suggesting that the corals are not sensitive to pH or CT but to the CO32- concentration. A decrease of 30% in the CO32- concentration (which is equivalent to a decrease of about 0.2 pH units in seawater) caused a calcification decrease of about 50%. These results suggest that calcification in today’s ocean (pCO2 = 370 ppm) is lower by 20% compared with preindustrial time (pCO2 = 280 ppm). An additional decrease of 35% is expected if atmospheric CO2 concentration doubles (pCO2 = 560 ppm)."

    This is entirely consistent with my article, which states “This reduces the concentration of CO32-, making it harder for marine creatures to take up CO32- to form the calcium carbonate needed to build their exoskeletons.” However, it is probably time to take the chemistry further, and include the extra material currently in my draft of the advanced rebuttal.

    If we combine equations (1) and (2) in my article above, and remove H+ from each side, we have:

    CO2 + CO32- + H2O <=> 2 HCO3-

    An article on RealClimate.com (The Acid Ocean – the Other Problem with CO2 Emission) explains the significance of this equation:

    "Since this is a chemical equilibrium, Le Chatlier’s principal states that a perturbation, by say the addition of CO2, will cause the equilibrium to shift in such a way as to minimize the perturbation. In this case, it moves to the right. The concentration of CO2 goes up, while the concentration of CO32- goes down. The concentration of CO3- goes up a bit, but there is so much HCO3- that the relative change in CO3- is smaller than the changes are for CO2 and CO32-. It works out in the end that CO2 and CO32- are very nearly inversely related to each other, as if CO2 times CO32- equalled a constant."

    The parameter that directly affects calcification is availability of CO32- rather than pH. However, there is a relationship between the parameters as shown in the diagram below. The blue column shows the fall in pH since pre-industrial times. Note that more acidic conditions caused by rising dissolved CO2 correlates with falling CO32-.

    The source of the problem is the increase in dissolved CO2 due to anthropogenic CO2 in the atmosphere. The immediate agent of the problem is the reduced availability of CO32-. A convenient way to track the availability of CO32- is to monitor pH.
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  43. Thanks Alan Marshall for the extra details and that helped me with understanding your post better.

    Also thanks to the yooper in #40 and for the recent paper from Pelejero.

    This is a very interesting and under reported topic - at least on the web sites I frequent.

    CO2 was high in prior intergacials as well as now so I can only assume that the oceans experienced a similar drop in carbonate ions and hence drops in calcification. Any idea how current ocean conditions compare with proxy data from the past? My apologies if the answer is in the link provided by the hooper - it's a long paper and I haven't finished yet.
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  44. Gary Thompson @ 43 - CO2 was high in prior intergacials as well as now so I can only assume that the oceans experienced a similar drop in carbonate ions and hence drops in calcification

    No Gary, you have that wrong. Previous interglacial CO2 levels were much lower than present (no industrial civilization). See ice core graph below:



    The peak atmospheric CO2 level during past interglacials is generally around 280 - 290 ppm. We are now at 390 ppm. So ocean pH was higher, and less acidic, during the previous interglacials. Thats what the boron isotopes tell us too.

    Earth has not experienced this level of ocean pH for at least 15 million years. Perhaps longer. See Tripati 2009
    0 0
    Moderator Response: [DB] The last time I looked at the ice core data, the peak CO2 levels attained during any interglacial over the past 800,000 years was 298.7 ppm, IIRC.
  45. It is without question that the atmospheric CO2 now is much greater than prior interglacials. But the ocean pH now is very similar to the pH in past interglacials (about 120,000 years ago) as shown by the graph below which was taken from the pelejero paper.

    So my question was regarding what was the impact on oceanic species and the possible extinction as related to now. And the fact that the pH in past interglacials was equal to the pH now seems to point to something else that changed the pH since the atmospheric CO2 now is much greater than in the past.

    0 0
  46. Gary Thompson @ 45 - Eye-balling the graph does indeed tend to convey similar pH levels to present during past interglacials, however that isn't the case. The graph simply lacks sufficient detail. Here's what the authors from Pelejero 2010 have to say:

    "The current human-induced perturbation of seawater pH starts at the low end of glacial–interglacial pH variability. From this perspective, and given that the surface oceans have already acidified by 0.1 pH units since the pre-industrial period, current conditions are already more extreme than those experienced by the oceans during glacial–interglacial cycles (Figure 2).

    Moreover, by the end of the twenty-first century, the projected decline in seawater pH might be three- times larger than perturbations observed as the Earth’s climate has oscillated between glacial and interglacial periods"


    Note that the 0.1 units referred to by the authors, represents almost a 30% increase in acidity over pre-industrial levels.

    Atmospheric CO2 (as contained in the ice cores) is a proxy for global ocean pH because of Henry's Law. More CO2 in the atmosphere dissolves into the oceans as concentrations in the atmosphere rise, causing pH to fall. (See the equations in the above post) . As atmospheric concentrations of CO2 fall (as in entering into a glacial period), CO2 dissolved in the oceans decline raising pH. The chemical reactions move in the other direction.

    Of course the ice cores only go back 800,000 years, and that's where the boron isotopes come into play as a paleo pH proxy.

    So your question as posed, is invalid. As stated earlier ocean pH levels have not been this low for millions of years. Here's what Pelejero 2010 have to say on that:

    "The average surface pH levels that oceans have reached today are already more extreme than those experienced by the oceans during the glacial–interglacial changes and beyond, probably being more extreme than at any time during the last 20 million years"

    Read the study, it summarizes the subject very well.
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  47. Thanks Rob, Yooper and Alan for sticking around and entertaining my questions. I did finally get thru the Pelejero study and that did answer my questions regarding paleo proxies.

    I noticed in his study he made the comment that measuring pH has always been difficult and I concur with that (both from college lab days and professional engineering days). I tried to access some of his sited references but couldn't find a good link showing the details of this pH measurement. I.e., what type of instruments are used, calibration, depths used in measurements! Frequency, time of day, etc.

    Any links to this subject are appreciated.

    Thanks!
    0 0
  48. i think i answered my own question from above. i found a paper that appears (from the abstract and first page) to give me what i need.
    0 0

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