What makes this even scarier are the people who propose we sequester CO2 deep under the ocean.

From the DOE

It's strange ocean acidification doesn't get more media attention. I guess the public can only be interested in one environmental issue at a time.

...still getting used to this link system : )

Yeah I've long said that even if you don't believe humans are causing global warming, ocean acidification is reason enough for us to seriously reduce our CO2 emissions.  Basically the acidification is in the process of disrupting major aquatic ecosystems, which is never a good thing.

Of course, the same people who deny that humans are causing global warming also deny that ocean acidification is a real problem.  Convenient.

This is yet another example of an effect happening faster than climate models predicted.

Back when I was in school, we had a lecture about climate change and ocean patterns.  I only vaguely remember it, but I think it was something about how as temperatures warm, ice melts (obviously), which then of course pours into the sea.  And the theory was that that influx of fresh water could potentially throw off the oceanic currents.  Do you guys know anything about that?

Hi stins,

You're referring to the "thermohaline circulation". There is indeed some danger that it could shut down if a massive amount of fresh water were to enter from the arctic (it has happened at least once in recent geological history, creating a global cold snap known as the Younger Dryas of about 10,000 BC.)

It is very unlikely however there will be something as severe as the Younger Dryas any time soon, mainly because it was caused by the bursting of a giant lake rather than meltwater, but some scientists are still concerned global warming will lead to enough meltwater that it could potentially slow or stop the circulation, along with the Gulf Stream, which would cause Europe's temperature to fall into a sort of mini ice age.

This is a completely different issue from ocean acidification, however, which is caused by higher CO2 being dissolved into the ocean and has nothing to do with currents.

See also this article describing the shutdown.

Yeah, that's the thermohaline circulation.  The theory goes that as ice melts into the north Atlantic (particularly from Greenland), it dilutes the salty ocean water.  This can shut down the thermohaline circulation, part of which is the Gulf Stream, which warms Europe.

So if sufficient ice melts to sufficiently dilute the Atlantic, this current could shut down and essentially send Europe into an ice age.  However, recent studies seem to suggest that this is highly unlikely to happen within the next 100 years.

A bit further discussion of this on RealClimate.

dang, Dawei beat me to it!

Marine biologists have been warning about ocean acidification for years.  Of course, nobody really paid much attention until Feely and Sabine actually measured the effect.  One of the problems with this idea is going to be that if you look at the paleo record (here: 

http://www.eur-oceans.eu/WP9/Factsheets/FS7/FS7_webprint.pdf

) ocean pH has been decreasing for a while.  Some skeptic is going to find this out and we're never going to hear the end of it (e.g., the skeptic argument is that pH has been decreasing over millions of years and this is just a natural trend).  But forewarned is forearmed (or fourarmed if you grew up near Chernobyl (haha mutant humor is always welcome)) so it's not a bad idea to start thinking about how to respond.  I'm not sure how to answer this, if skeptics bring it up, except to maybe cite this:

http://igbp-scor.pages.unibe.ch/gfx/PAGESnews.pdf

which states "... data so far suggest that there is no exact past analog of present-day CO2 emissions ..." showing that looking at the paleo record is not a good proxy for ocean acidity changes from here forward.  The SCOR document (second link above) is also nice because it talks about the linkage between acidification events in the paleo record and recovery of ocean biology. 

And, I haven't read this but I knew it was out there, so I'm giving myself this as homework to:

http://www.ucar.edu/communications/Final_acidification.pdf

I think that modelling the ocean uptake of CO2 may be a bit too challenging.  The system is too big and complex and the time constants are too large for equilibrium calculations.  Perhaps we should be looking at acidification in freshwater lakes that are smaller and easier to model and then use scaling to extrapolate the results to larger bodies of water.

Respectfully, I disagree with this post and I think so would geochemists like Feely.  Looking at acidification in freshwater lakes isn't the same since freshwater systems in general don't have the dissolved inorganic carbon that the ocean does. There is a lot that is known about the chemistry, the physics of exchange of CO2 across the air-sea interface, and how large-scale circulation affects ocean surface chemistry.  Geochemical models are now doing really well modeling long-term ocean uptake and storage of CO2, and the agreement between the ocean general circulation models and tracer data (such as CFC invasion and bomb-14C) is very good.  So there is no reason that these models can't (and aren't) be used to project ocean surface pH response. 

Also, systems with large time constants are precisely where equilibrium chemistry applies, since the chemistry is in local equilibrium with something that is changing slowly.  So, there's no reason to study reductionist systems.  The problem is not modeling or that equilibrium models are inapplicable, but that the response over the surface will be non-uniform and will require a very large observational effort to acquire data for model validation.  (Mapping ocean surface pH requires a program similar in scope to the ocean surface carbon survey (the results of which can be found at the CDIAC website run out of Oak Ridge National Laboratory).  There are also issues of defining pH in high ionic strength media like seawater, but those issues are too complicated for me to want to get into here.) 

-Bill

Point taken gncp.  Do your comments extend to the deep oceans or did you have the surface layer in mind?

It's really the surface that is an issue as far as acidification is concerned.  That is partly because the biology that is of interest is mainly photosynthetic (or eats photosynthesizers) so it lives near the surface (which is also where air-sea gas transfer occurs).  But of equal importance is that stuff happening deep in the ocean is already below the lysocline and the increasing solubility of calcite as pH decreases makes no difference to anything. 

CO2 chemistry is fairly well known both as a function of temperature and pressure, so modeling the response in CO2 chemistry to acidification is largely depth-independent.  But the largest effects will be felt in the mixed layer.  For example, one of the hot-topic organisms people are interested in are coccolithophores, which I mention only to use coccolithophore in a post, and you can find lots of studies on cc's and the effect of pH (e.g., here).  (These critters figure in the link between biology and cloud-condensation nuclei because they produce dimethyl sulfide, which gets oxidized to methane sulfonic acid, which gets neutralized by ammonia (see the CLAW hypothesis).  Therefore, if they get reduced in number, or bloom everywhere, it could affect cloud formation, which would have very large climatic effects.)

I realize I should find some references for this, but if you run through that document from UCAR I cited above it should have most of this in it.  Also, a lot of the current work is given here on the EPOCA news site:

http://oceanacidification.wordpress.com/

Anyway, don't get me started on air-sea gas exchange. 

In reading about Austrailan efforts to sequester CO2 deep in the ocean I read that the idea hac been conceived of when researchers discovered that deep in ocean valleys they were encountering liquid CO2 that just stayed there.

Their concept was proven by running a pipe down to a level that their computations indicated because of pressure CO2 would have to be liquid. Well, the liquid leaving the pipe did drop toward the bottom of the oceans, so they built the production scale unit a bit deeper to account for delay in liquification and it appears that the CO2 does drop to ocean bottom.

Concern has been expressed that volcanic or even seismic activity might send that liquid CO2 into the upper layers of the ocean, where reduced pressure could cause the CO2 to gassify and escape into the air.  I am not sure whether that concern is sound.

However I have a more significant concern, significant to me at least. When we create a cache of CO2 deep in the ocean we have a recycling problem. We urgently need the oxygen from that CO2. We should be converting that CO2 back to O2  plus other food or fuel.  Ie we should ideally be using plants to absorb that CO2 and get the oxygen from it.

Now CO2 deep in the ocean does not contribute to ocean acidification, even though the natural (Brownian) method of getting CO2 down there will cause acidification as it spends time in the upper layers of the ocean.

So, I am not concerned about deap ocean sequestration from an acidification point of view as long as it stays down there.

Blue-green algae will cause acidification because it fixes atmospheric nitrogen to become nitrate in the ocean, and breakdown of igneous rock does release sulphides and sulphates, phosphates that all remain long term in ocean water.

This is one area that ocean water is very different from lake water because water flows on through a lake. In an ocean it keeps on regenerating as plants decompose. It never flushes out of the ocean except by precipitation.

Don:

There are a couple of misconceptions in your post.  First off, the loss of the oxygen atoms in sequestering CO2 from combustion is trivial compared to the global supply.  There is plenty of bicarbonate in the ocean available for photosynthetic production of oxygen.  I forget exactly, but burning all coal and oil reserves wouldn't change global oxygen levels very much, and most geochemists put oxygen depletion very low on the list of things we ought to lose sleep over (e.g., here). 

Deep-ocean sequestration of CO2 is a bad idea because it cannot be assumed it will stay there over long timescales, even as a liquid (CO2 liquifies under pressure) and we know relatively little about deep benthic ecologies.  For instance, I have heard anecdotal stories of early CO2 injection experiments acting like the hand of god on the sea floor, sweeping it clean of all organisms (no reference available for this).  As such, any plan to inject CO2 into the ocean should be seen as a very short-term emergency response while alternative technologies are brought into use. 

Secondly, the nitrogen cycle has little effect on ocean surface pH.  The reason is that if you add mineral acidity (or alkalinity) to the ocean, it drives CO2 out (or in) so that the net change in pH is small (e.g., if you add acidity, CO2 leaves, bringing pH up).  You can find references explaining this here.  (The context of that paper is anthropogenic nitrogen/sulfur input, but the chemical response is the same regardless of the source of the nitrogen.)

Funny you should mention this.  I realized earlier today that my GCC links associated with oceans were thin, and promptly racked up 9 or 10 and now must go back and investigate them more thoroughly.  I'd like for the group to broaden this line of discussion.  I probably won't be chiming in much for a few days -- after the holiday I'm going camping to clear my head and walk off the cookies -- but may bring the laptop and check out the ocean related info so I know where I want to go with this.

Great discussion on the topic so far.  I can see you guys are going to keep me on my toes.  Just what I needed.

gcnp58.

I did not begin to understand all of what you wrote.

But when I see that adding nitrate does not change pH much, no, of course not. What it does is convert carbonate,  increase the amount of CO2 in the water, ready to escape. And as that increased CO2 hangs around a bit we get increased acidity from the CO2. the CO2 build up does move the CO2-carbonate equilibrium locally to greater acidity.

The Blue-green algae provide excess nitrate available to other plants which grow in the  air-water interface, grabbing CO2 out of the air and when they sink into the water and decompose, they release CO2 into the water. No big problem. But what the decomposition does is absorb oxygen from the water to such an extent that we get ocean dead zones, where animal life can not live. Animal life can tolerate the CO2 but not the low oxygen levels.

But the decomposition leaves CO2, Sulphate, Nitrate, Phosphate ions plus all the other fertilizer components in enriched mode where they decompose, allowing for ongoing growth of more excess plant life.

My evaluation of this process is that earth has seen this happen before, when large volumes of plant material, too large to be decomposed by available oxygen, have sunk to the  bottom to form our oil , coal and gas deposits.

When we get moderate areas of dead zones, I  expect we are approaching the stage when dead zones predominate, and the oceans become our main repository for CO2, sequestering it as newly formed fossil fuel deposits.

We do not have a lot to do with this other than perhaps harvest that excess plant matter before it sinks into the seas .

We can not save the ocean animal life by using herbicides, by preventing phosphates or nitrates from reaching the oceans, nor can we change anything by adding limestone, simply because as limestone disolves it supplies carbonate ion, we can accomplish nothing by firing the lime to produce calcium oxide and CO2, because the CO2 will also get back to the oceans.

No solution then remains  but to harvest the excess plant life and use it for fuel instead of coal and oil. That does nothing to improve the situation other than that we do not use the coal and oil, and the plant matter does not use oxygen from oceans. Plant matter thus burned will use oxygen from the air just as burning coal or oil would, so no gain or loss there.

Don:

Air-sea gas exchange is a rapid process compared to all the other things that are going on.  If production of mineral acid occurs in significant quantity from fixation of nitrogen, any reduction of pH won't persist because CO2 evasion will occur relatively rapidly (the time constant is on order of 20 days (Trenberth, Climate System Modeling, p 247)).  When people like Feely talk about ocean acidification, they are talking about a persistent long-term decline in surface pH. 

If you grind through all the energy you need to use to produce fuel from ocean biomass, and do it honestly by not neglecting things like the need to rinse all the salt out of the biomass before processing, you will find it is an energy-losing proposition (similar to how producing alcohol from corn uses more energy than it produces).  People don't like to be told this because none of us can conceive of such a world, but at some point we are going to have to resign ourselves to the fact we all have to get by on a fraction of the total energy we use per day (and I am talking about "us" in the sense of us in the developed nations).  There is no such thing as a free lunch, energy-wise, and if we are truly committed to minimizing the effect on global climate, we have to get away from the notion that there will be ways for us to live the exact same energy using lifestyles we now enjoy using "green" energy sources. 

You appear to be making the point that the CO2 in the atmosphere will not cause ocean acidification, and by inference that nothing can cause ocean acidification, since addition of acid to the oceans can not either.

Am I reading you correctly?

No, you are completely misreading me.  What I am saying, and have provided a paper from PNAS to back up (look back up the thread), is that adding mineral acid (i.e., any acid that is not carbonic acid) to the ocean does little to change pH.  The reason is that when you add mineral acid to the ocean, all that does it remove a little total dissolved inorganic carbon from the system (at the expense of raising the concentration of CO2 in the atmosphere) and the pH comes back to nearly what it was before you added the mineral acid (there is a theoretical limit that you can't add more milli-equivalents of mineral acid than there are milli-equivalents of bicarbonate, although well before you reach that point the atmosphere itself will buffer the changes from the mineral acid (so by adding a *lot* of mineral acid you can get the ocean pH to decrease (you will increase CO2 by a lot in the atmosphere though))).  However, raising atmospheric CO2 concentration *does* affect pH, because the carbonate system in the ocean responds to the increase in acidity from having more CO2 around but the ocean can't pump CO2 back into the atmosphere since the atmospheric increase forced the pH change to begin with. It seems counterintuitive, although nonetheless true, unless you have suffered through Chapters 3 and 4 of Stumm and Morgan. 

You have just restated my original position, that by ocean driving CO2 into the atmosphere we set up conditions for atmospheric CO2 to increase the acidity of the ocean. Put another way, asumptions about CO2 leaving the ocean and thus not lowering the pH of the ocean take far too short term a view of the whole process.

Any and every process that puts CO2 into the atmposphere lowers ocean pH, and every source of acidity entering the oceans causes CO2 to enter the atmosphere from the ocean. Thus by a feedback mechanism, nitrate ions released into the water cause release of CO2 to the atmosphere which lowers ocean pH.

No, I didn't restate what you said.  You seem to be confusing which process is driving changes in alkalinity, addition of CO2 to the atmosphere from non-oceanic sources (which forces the pH of the ocean to decrease), and addition of mineral acid to the surface ocean (which forces CO2 out of the surface ocean into the atmosphere, which buffers the pH change, although that atmospheric CO2 increase does not "feedback" and cause a further decrease in ocean surface pH). 

The point of the PNAS article is that if you think of the problem in terms of adding moles of acid to the ocean, adding a specific amount of mineral acid to the ocean doesn't lower the pH nearly as much as adding enough CO2 to the atmosphere to drive the equivalent number of moles of CO2 into the ocean.  Thought of another way, although adding a mineral acid like nitric acid lowers the pH of the ocean, you get a much much larger decrease in ocean pH by adding CO2, from a source other than the ocean, to the atmosphere.  The reason is that in the former case, the atmosphere acts as a reservoir of excess CO2 from the ocean, buffering the pH change.  In the latter case, there is no reservoir for the excess CO2 since the atmosphere is driving the ocean. 

Finally, think about this, adding CO2 to the atmosphere causes acidity to enter the ocean because the net flux of CO2 is from the atmosphere to the ocean.  In other words, that is a process that adds acid to the ocean, yet the CO2 flux is opposite what you state is categorically true.  So your bolded statement is incorrect, which I point out not in a "nurnie nurnie nurnie" mode but in the Socratic mode showing that perhaps you haven't thought this through all the way. 

Please don't get mad.  I'm trying to understand why you are confused and make sure you understand the basic (no pun intended) difference between case 1 (addition of a non-CO2 acid to the ocean) and case 2 (addition of CO2 to the atmosphere).  I'll shut up now, likely nobody cares about this anyway. 

At the risk of letting this thread get too off topic, that is definitely an interesting theory. It still claims that meltwater from Lake Agassiz and a shutdown of the thermohaline current was responsible though:

The scientists say that the impact could have destabilized and melted the edges of the ice sheet resting on the northern tier of the continent.

Seems a bit one-in-a-million that a meteorite broke the ice rather than just warming, but stranger things have happened.

GCNP.  You totally lose me. Your terminology will not convey anything to most people with my ever so slight knowledge, or less.

I hope you learn to communicate with we who have only  a BSc degree.

So I will just bow out of this discussion.

Sorry Don, maybe GCNP's comments will be understood earier if you fall back on le Chatelier's Principle.  A system will react to minimize the change from an external forcing. For a start on the chemistry, look up the wiki on carbonic acid here http://en.wikipedia.org/wiki/Carbonic_acid

The article gives the results for 6 equations in 6 unknowns.  GCNP is essentially just elaborating on the basic system by considering the role of additional ions (more equations and unknowns to solve for) and giving you the results of the calculation in a qualitative manner. 

I hope that helps.

I found this link through Gore's website today.  I like it because the information is accessible and fairly well presented. 

http://www.economist.com/specialreports/displaystory.cfm?story_id=12798428

Just came across this article published on PlanetEarth yesterday, called "Ocean acidification - the other CO2 problem".  Here's just one tiny excerpt:

'By the end of this century, the oceans will be more acidic that they have been for more than 20 million years,' says Dr Ian Joint, a marine microbiologist at Plymouth Marine Library.

Yes, precisely.  The point is that the acid-base chemistry of the ocean is determined mostly by the carbonate system, and injecting CO2 into the atmosphere has the largest effect since there isn't any way to buffer (in a pH sense) the resulting increase in aqueous-phase CO2 concentration.  The ocean can buffer pH changes by mineral acids by releasing CO2 to the atmosphere.