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Author Topic: What is the historical correlation between atmospheric CO2 and ocean acidity?  (Read 4270 times)

Offline CliffordK

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I was reading about PETM today, and noticed a comment (similar on several websites).

since the presence of CO2 in the atmosphere is directly correlated with decreased oceanic pH, we can study past levels of atmospheric CO2 and extrapolate the corresponding oceanic pH to build models showing levels of ocean acidity throughout time.
[...]
The last levels of acidification which approach today’s occurred 55 million years ago during the Paleocene-Eocene Thermal Maximum.

This just seems absolutely opposite from what I would expect. 

As I understand it in past times, as global temperatures would increase, it would drive CO2 out of the oceans and up into the atmosphere. 

That would then indicate that a higher temperature would correlate with lower ocean CO2 concentrations, and higher ocean pH (more basic). 

Lower temperatures, on the other hand, would correlate with more uptake of CO2 from the atmosphere, and lower ocean pH (more acidic).

So, I would expect the ocean pH to have rapidly increased during PETM (more basic) (as well as having increased (more basic) with the temperature increase over the last 15,000 years). 

The acidification is when there is less carbon stored in the soil, and more in the oceans, as we are doing now with the fossil fuel burning.  If the temperature in prehistoric times was the same as it is today, but with higher atmospheric CO2 (before it was sequestered in fossil fuels), then one would also expect lower pH (more acidic).  However, rapid temperatures rises as occurred during PETM would increase the pH (more basic).

Am I missing something?


 

Offline alancalverd

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High atmospheric temperatures are due to increased water content, and high global temperatures increase insect and other cold-blooded animal activity, which raises the atmospheric concentration of CO2.  Direct absorption of CO2 in the oceans is much less significant than CO2 washout by rainfall as the surface area of rain is orders of magnitude larger than that of the oceans, and rain is generally colder than seawater.

So high temperatures = more rain + more CO2 = more acidic seawater

Presumably fish "exhale" CO2 so surface acidity may well depend on fish populations and activity.
 

Offline SimpleEngineer

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The other question is, can anyone think what reactions may occur with a more acidic ocean? (higher erosion near limestone?) is there any neutralising factor?

 

Offline yor_on

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Acidity is what is going to decide our survival I think. Just saw a rather depressing Swedish science program about it, more or less confirming my worst ideas. Arctic plankton are losing their shells, they've gone down 35% from the nineties, and as they are the first food-chain? And as if that doesn't sux enough for one evening? Then, "every other breath you take are produced from organisms like those" according to the scientists making that program. And no, I don't think they are trying to create a panic, what they are doing is research on what organisms that may survive acidity, and then especially coral reefs. Although coral reefs only consist of one percent of our oceans, they contain twenty five percent of those oceans fish.

"The fish that grow and live on coral reefs are a significant food source for half a billion people worldwide – many of whom live far from the reefs that feed them. Millions of people in coastal villages of tropical developing countries depend on reefs for their livelihoods, with 25 percent of all fish caught in these regions coming from coral reefs. These benefits are not limited to developing countries – approximately half of all federally managed fisheries in the United States depend on coral reefs and related habitats for a portion of their life cycles. The NOAA National Marine Fisheries Service estimates the commercial value of U.S. fisheries from coral reefs to be over $100 million. "

To study it they have been studying a place with a lot of under water volcanic activity, where the acidity already is, and has been for a hundred years, what is expected to be in the oceans around 2100. Not that far away in time, I won't see it, and my own kids may miss that date, but Embla, my daughters daughter, will definitely be there to witness it. And it was a sad sight. Very little fish, no coral reefs left in the parts where that acidity was, except a few that seemed sturdier, no colors though. they also tried to see what the 'seeds(coral bloom)' would do to plates they anchored under water, both where the water still was fresh (control sites) as well as inside thoseCO2 areas. Coming back one year later instead of corals they found algaes growing on the plates inside those areas, thriving in the new climate.

High time to stop treating this as a political question I think, blaming it on different political agendas.
« Last Edit: 11/11/2013 21:05:45 by yor_on »
 

Offline yor_on

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As for "As I understand it in past times, as global temperatures would increase, it would drive CO2 out of the oceans and up into the atmosphere."

What you mean is that there should be a threshold for the ocean capacity to contain the CO2 right? But that is a very tricky question where I don't think we know yet. Cold water should be the first waters though, to reach that threshold as they accumulate more CO2 than warm waters can as I think, but I'm not sure? We've already passed "an average daily level above 400 parts per million of carbon dioxide"

Last time we had that concentration was around three millions years ago, as a best guess. We are fracking those days, and using what we call 'natural gas' (methane). There are evidence that those fields leak, although how much is still debated. Combined with underwater pipelines, as that is the new trend? This is what we are planning to use, combined with atomic energy, unless we really decide to start developing the natural renewable resources we have, water wind sun etc, as far as possible. But we need to do it now Clifford, the CO2 we already have in the atmosphere clings there for a long time, the tail of it being millenniums, not centuries. And we've already passed one suggested limit.
 

Offline evan_au

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Quote
as global temperatures would increase, it would drive CO2 out of the oceans and up into the atmosphere
  • There is another effect in operation apart from varying solubility with temperature: The concentration of CO2 in the atmosphere and dissolved in the ocean surface water are in equilibrium.
  • If atmospheric CO2 goes up, then more CO2 will be dissolved in surface waters, making the surface water more acidic.
  • If atmospheric CO2 goes down, then CO2 will come out of solution, making the surface water more neutral.
  • Over time, oceanic surface waters mix with deeper waters, by means of currents flowing towards the poles, cooling, and dropping to the bottom of the ocean. This mixes CO2 through the water column, and also brings fresh water to the surface to dissolve more CO2.
There are now unmanned ocean submersibles now studying CO2 concentration through the depth of the water column.
 

Offline yor_on

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There is an awful lot we don't know about how the ocean take care of CO2 deposits as I think. It would be nice if it was so that we could count on some vertical 'down (and up) welling' that continuously took care of 'surface' CO2, but I don't think it is enough.

 "Surface waters are mixed by winds and deep ocean water mixing is driven by density differences. Circulation in the depths of the ocean is referred to as thermohaline circulation. The deep ocean is layered with the densest water on bottom and the least dense water on top. Water tends to move horizontally throughout the deep ocean, moving along lines of equal density. Vertical circulation is limited because it is easier for water to move along lines of constant density (isopycnals) than across them."

But sure, down and up welling exist, and is the ground for some of the richest fishing grounds in the world, as in Peru. But I don't think it will be fast enough.
 

Offline alancalverd

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I live on what was once the bed of a tropical sea. Massive quantities of chalk, with a few hippopotamus bones in the more recent layers. (It's now one of the coldest parts of England!)

Now how did all that chalk get there if there wasn't plenty of CO2 in the water? Sometime, way back in the past, the temperature was a lot higher and the CO2 level likewise, but instead of dying, the oceans burst into bloom.

But when did any climate terrorist concern himself with facts?
 

Offline yor_on

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Sorry Alan, but I'm not sure what you're meaning there? That the chalk you find is evidence of CO2 being beneficial to oceans, and marine life? There are ideas of using nickel to sequester carbon, highly interesting.

“We had set out to understand in detail the carbonic acid reaction, which is what happens when CO2 reacts with water, and needed a catalyst to speed up the process,” said Šiller of Newcastle University in a press release. “At the same time, I was looking at how organisms absorb CO2 into their skeletons and in particular the sea urchin which converts the CO2 to calcium carbonate

“When we analyzed the surface of the urchin larvae we found a high concentration of nickel on their exoskeleton. Taking nickel nanoparticles which have a large surface area, we added them to our carbonic acid test and the result was the complete removal of CO2.”

But this is not addressing the acidity already existing, coming from man made CO2 existent in the atmosphere, today and the main portion existing for some one, to two, hundred years forward. And that's even if all man made CO2 sources, as those cars we use was stopped today. It's also a unproven idea, needed to be proved to be cost effective as involves an awful lot of nickel, and practically possible, as well as used globally, example-wise for heavily CO2 polluting industries. The bottom line though, is that it won't change anything before one, or a couple of, centuries has gone, if found feasible. Still, it is one possible way to lock up CO2, although there are more, saw someone using suggest fast growing bamboo for it too. "It sequesters 35% more than trees." Also stating that if you "carbonize bamboo older than three years, it turns glassy because of it's high silica content." You can use grass too, as long as you can guarantee no erosion of soil. I don't know how one can guarantee that though, other than from a short time perspective. Should make it popular with politicians :)

The problem with arctic melting seems to involve a lot of unknowns. One example I saw recently is what sunlight penetrating formerly 'dark waters' protected by ice, might do to the marine bottom life, and their biology? Light-driven tipping points in polar ecosystems. (pay site)

 
 

Offline alancalverd

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I didn't use words like "beneficial". The evidence is simply that it has been a lot hotter in the past, there was a lot more CO2 in the atmosphere, and ocean critters used it to make their calcium carbonate skeletons. Whether that is a good or bad thing depends principally on whether you are a calciferous diatom, I guess. 
 

Offline yor_on

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Yes, that is a possibility, but I don't think it relate to most of the marine shell building life we see today? Although, one could assume 'dormant genes, as genes not being used at the moment, stepping in, as a possibility? And possibly also mutations through natural selection, meaning those surviving/adapting to the acidity, mating.

The Science program I watched discussed something opposite, not about the Arctic and shells though, but in the tropics. Although you could find a few stubborn bleached corals surviving in those CO2 saturated tropical waters, containing some few species of fish, it seemed as the CO2 saturation made them lose their understanding of 'smell'. Comparing fish living outside those waters with those living inside it was found that the ones 'inside' no longer avoided the (chemical) smell of 'fish predators' in the water. They had in fact stopped recognizing it as a danger signal. Now, if I assume that this is a result of genetics, recognizing danger, then those genes no longer was able to communicate that danger, even though the ability to 'smell' still was there.

If I then take a fast look at the 'biological carbon pump' by which a lot of CO2 are moved into deeper layers of the ocean, by decomposing shells, feces from krill etc, and all dead marine, or not, animals in general? "Bacterial decomposition releases CO2 into the coldwater of the deep ocean currents during respiration. Thus, carbon may stay in deep ocean currents for hundreds of years, and in sediments for thousands to millions of years." Even though only a fraction of shells etc, reaches the deep bottoms of the ocean intact, I believe that we safely can assume that the deeper down it dissolves, the longer the storage of the CO2, generally speaking.

"Shell-building phytoplankton and animals build theirshells from carbonate ions. The carbonate ions are produced when dissolved CO2combines with seawater H20 to produce carbonicacid(H2CO3), bicarbonate(HCO3-) and carbonate ions(CO32-)

When shelled organisms die, their shells sink to the bottom of the oceans and accumulate as carbonate-rich ocean sediments. However, most shells dissolve before reaching bottom-sediments, especially in deep, cold water! Most of the carbon that reaches deep ocean sediments are from shell-building plankton like the foraminifera and coccolithophores."

But now it dissolves and 'corrodes' in the upper layers instead.

"In a review of hundreds of paleoceanographic studies, a team of researchers from five countries found evidence for only one period in the last 300 million years when the oceans changed even remotely as fast as today: the Paleocene-Eocene Thermal Maximum, or PETM, some 56 million years ago.  In the early 1990s, scientists extracting sediments from the seafloor off Antarctica found a layer of mud from this period wedged between thick deposits of white plankton fossils. In a span of about 5,000 years, they estimated, a mysterious surge of carbon doubled atmospheric concentrations, pushed average global temperatures up by about 6 degrees C, and dramatically changed the ecological landscape.

The result: carbonate plankton shells littering the seafloor dissolved, leaving the brown layer of mud. As many as half of all species of benthic foraminifers, a group of single-celled organisms that live at the ocean bottom, went extinct, suggesting that organisms higher in the food chain may have also disappeared, said study co-author Ellen Thomas, a paleoceanographer at Yale University who was on that pivotal Antarctic cruise. “It’s really unusual that you lose more than 5 to 10 percent of species over less than 20,000 years,” she said. “It’s usually on the order of a few percent over a million years.” During this time, scientists estimate, ocean pH—a measure of acidity--may have fallen as much as 0.45 units.  (As pH falls, acidity rises.)

In the last hundred years, atmospheric CO2 has risen about 30 percent, to 393 parts per million, and ocean pH has fallen by 0.1 unit, to 8.1--an acidification rate at least 10 times faster than 56 million years ago, says Hönisch. The Intergovernmental Panel on Climate Change predicts that pH may fall another 0.3 units by the end of the century, to 7.8, raising the possibility that we may soon see ocean changes similar to those observed during the PETM." from Ocean Acidification Rate May Be Unprecedented, Study Says. (2012)   

And it's not only plankton, but also deeper living shell building marine animals that are showing signs of shells 'corroding'. Ocean Acidification Corroding Shells of Antarctic Sea Snails. (2008) 

"Wherever mixing takes place in the ocean, or where currents bring the colder, nutrient-rich waters up from the depths, the surface waters will be enriched with added nutrients which may stimulate phytoplankton growth." But they also need the sun to reproduce. "The algae component of plankton grows in the surface water, down to a depth of a few dozen metres, where the sunlight is still strong enough to allow photosynthesis to take place. Like land-based plants, phytoplankton needs both mineral elements and sunlight to be able to grow. There are thousands of different species of planktonic algae, all of them microscopic. They comprise the lowest link in the marine food chain."

"Although large areas of the tropical and sub-tropical oceans have abundant light, they experience relatively low primary production because of the poor availability of nutrients such as nitrate, phosphate and silicate. This is a product of large-scale ocean circulation and stratification of the water column. In such regions, primary production, still usually occurs at greater depth, although at a reduced level (because of reduced light)."

"Ocean zones where phytoplankton (diatoms, flagellates, etc.) will proliferate are usually the zones where the nutriments are found close to the surface where light can penetrate (shallow waters or else deep waters where upwellings bring the nutriments to the surface)."

And the same should go for krill, well, as far as I know, feeding on phytoplankton. Will krill fare well under Southern Ocean acidification?
 

Offline yor_on

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The point is twofold. The shells doesn't build and that means more CO2, it also means a higher (plankton/krill etc) mortality, and so less oxygen produced for us land based, as well as sea based, animals (flora and fauna). It should also mean that coral reefs, as we know them today, will disappear in about a hundred years, with a lot of their food fish, all building on the research done so far. Now, we can naturally ignore this research, calling it 'flawed' as it doesn't sit too well with what we want to believe to be our 'natural rights' as 'conquerors of Earth'. Well, that's very Hollywood of us, isn't it :)
=

Of course, it also goes without saying, (although I do it this time:) that it is the first link in a presumably global food chain that may go missing. What will, or can, take its place I don't know, hopefully species migrating from places outside this formerly 'cold zone', now getting temperated. If they can do a same job, providing oxygen, becoming a first link in a 'new' food chain? That still stand to be proven though.

And Clifford. I found The Paleocene Eocene Thermal Maximum (chapter three) rather enlightening, comparing it with today.
« Last Edit: 13/11/2013 19:29:32 by yor_on »
 

Offline alancalverd

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All very intriguing, but CO2 levels and temperatures have been higher in the past. What evidence is there of correlated massive extinctions?
 

Offline yor_on

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Alan, the point that make CO2, especially man made CO2, a culprit to me is primary the statistics collected. When you look back geologically it seems as the best comparison would be The Paleocene Eocene Thermal Maximum, although that is more about what the consequences of a raised CO2 might mean for the future, than of it being for the exact same causes. "In the first decade of the 21st century evidence emerged from several scientific fields to clearly demonstrate that 55 million years ago a massive release of CO2 abruptly raised earth’s temperature. This event and its consequences is now commonly referred to as the Paleocene Eocene Thermal Maximum (or PETM for short)."

If we can assume the exact same I do not know, wish I did though. But I don't think making it into a political issue, as done in USA, helps solve the question of what we should do. Neither does it help throwing dirt, and lies, on those trying to unravel how our Earth system works. Those 'susceptible, as well as suspect, climate scientists, biologists,geologists' etc.. But that is what seem to come from treating it as someones political 'agenda', instead as of a 'disaster in the making'. At the same time as it allows business interests, interested, and locked, to keeping the old energy solutions alive (with the power that follows), to keep on doing 'business as usual', all my own view naturally.

Strange isn't it. As long as science doesn't rock the boat it's all good. But as soon as it states something, going against our short time interests?
« Last Edit: 15/11/2013 00:49:05 by yor_on »
 

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