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Oceans Acidifying Faster Today Than in Past 300 Million Years

Posted on 5 March 2012 by John Hartz

This is a reprint of a news release posted by the National Science Foundation on March 1, 2012.

Few parallels for today's rapid ocean changes in geologic record

NOAA photo of ocean life

The oceans may be acidifying faster today than they did in the last 300 million years, according to scientists publishing a paper this week in the journal Science.

"What we're doing today really stands out in the geologic record," says lead author Bärbel Hönisch, a paleoceanographer at Columbia University's Lamont-Doherty Earth Observatory.

"We know that life during past ocean acidification events was not wiped out--new species evolved to replace those that died off. But if industrial carbon emissions continue at the current pace, we may lose organisms we care about--coral reefs, oysters, salmon."

The oceans act like a sponge to draw down excess carbon dioxide from the air.

The gas reacts with seawater to form carbonic acid, which over time is neutralized by fossil carbonate shells on the seafloor.

If too much carbon dioxide enters the ocean too quickly, it can deplete the carbonate ions that corals, mollusks and some plankton need for reef and shell-building.

In a review of hundreds of paleoceanographic studies, the researchers found evidence for only one period in the last 300 million years when the oceans changed as fast as today: the Paleocene-Eocene Thermal Maximum, or PETM.

In ocean sediment cores, the PETM appears as a brown mud layer flanked by thick deposits of white plankton fossils.

About 56 million years ago, a mysterious surge of carbon into the atmosphere warmed the planet and turned the oceans corrosive.

In about 5,000 years, atmospheric carbon doubled to 1,800 parts per million (ppm), and average global temperatures rose by about 6 degrees Celsius.

The carbonate plankton shells littering the seafloor dissolved, leaving the brown clay layer that scientists see in sediment cores today.

As many as half of all species of benthic foraminifera, a group of one-celled organisms that live at the ocean bottom, went extinct, suggesting that deep-sea organisms higher on the food chain may have also disappeared, said paper co-author Ellen Thomas, a paleoceanographer at Yale University.

"It's really unusual that you lose more than 5 to 10 percent of species," she said.

Scientists estimate that ocean acidity--its pH--may have fallen as much as 0.45 units as the planet vented stores of carbon into the air.

"These scientists have synthesized and evaluated evidence far back in Earth's history," said Candace Major, program officer in the National Science Foundation's (NSF) Division of Ocean Sciences, which funded the research.

"The ocean acidification we're seeing today is unprecedented," said Major, "even when viewed through the lens of the past 300 million years, a result of the very fast rates at which we're changing the chemistry of the atmosphere and oceans."

In the last hundred years, rising carbon dioxide from human activities has lowered ocean pH by 0.1 unit, an acidification rate at least 10 times faster than 56 million years ago, says Hönisch.

The Intergovernmental Panel on Climate Change (IPCC) predicts that pH will fall another 0.2 units by 2100, raising the possibility that we may soon see ocean changes similar to those observed during the PETM.

More catastrophic events have happened on Earth before, but perhaps not as quickly.

The study finds two other analogs for modern day ocean acidification--the extinctions triggered by massive volcanism at the end of the Permian and Triassic eras, about 252 million and 201 million years ago, respectively.

But the authors caution that because ocean sediments older than 180 million years have been recycled back into the deep Earth, scientists have fewer records to work with.

During the "Great Dying" at the end of the Permian, about 252 million years ago, about 96 percent of life disappeared.

Massive eruptions from what is known as the Siberian Traps in present-day Russia are thought to have triggered earth's biggest extinction.

Over 20,000 years or more, carbon in the atmosphere rose dramatically.

Scientists have found evidence for ocean dead zones, and preferential survival of organisms predisposed to carbonate-poor seawater and high blood-carbon levels, but so far they have been unable to reconstruct changes in ocean pH or carbonate.

At the end of the Triassic, about 201 million years ago, a second burst of mass volcanism associated with the break-up of the supercontinent Pangaea doubled atmospheric carbon and touched off another wave of die-offs.

Coral reefs collapsed and an entire class of sea creatures, the eel-like conodonts, vanished.

On land, large plant-eating animals gave rise to meat-eating dinosaurs like Tyrannosaurus rex as the Jurassic era began.

A greater extinction of tropical species has led some scientists to question whether global warming rather than ocean acidification was the main killer at this time.

This study finds that the most notorious of all extinctions, the one that ended the Age of Dinosaurs with a falling asteroid 65 million years ago, may not have been associated with ocean acidification.

The asteroid impact in present-day Mexico 65 million years ago released toxic gases and possibly set off fires that sent surges of carbon into the air.

Though many species of plankton went extinct, coral reefs and benthic foraminifera survived.

In lab experiments, scientists have tried to simulate modern ocean acidification, but the number of variables currently at play--high carbon dioxide and warmer temperatures, and reduced ocean pH and dissolved oxygen levels--make predictions difficult.

An alternative to investigating the paleo-record has been to study natural carbon seeps from offshore volcanoes that are producing the acidification levels expected by the year 2100.

In a recent study of coral reefs off Papua New Guinea, scientists found that during long-term exposure to high carbon dioxide and pH 0.2 units lower than today--at a pH of 7.8 (the IPCC projection for 2100)--reef biodiversity and regeneration suffered.


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NSF Discovery Article: Trouble in Paradise: Ocean Acidification This Way Comes:

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Comments 1 to 20:

  1. Purely by coincidence, Joe Romm also posted today an article about the findings of the paper discussed in the above OP. The title of Romm’s article is:”Science: Ocean Acidifying So Fast It Threatens Humanity’s Ability to Feed Itself” It covers some ground not covered in the above OP. The two articles nicely complement each other. To access Romm’s article, click here.
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  2. The OP and Romm’s article are based on the findings contained in the peer-reviewed article, “The Geological Record of Ocean Acidification”, Hönisch, et al, Journal of Science, March 2, 2012: 1058-1063, DOI:10.1126/science.1208277 Unfortunately, this paper is behind a paywall.
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  3. I read the paper and I understand the implications, but it doesn't include a graph showing the recent, rapid change in ocean pH. The graph of ocean pH that it does show (figure 3) is on the scale of millions of years. Figure 2 shows their model of how the time course of atmospheric CO2 influences ocean pH. Does anyone know where I can find a graph showing recent ocean pH measures on the a finer time scale?
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  4. The paper can be found at: The supporting online material here: I found the figure 3 very illuminating, it tells the story of the response time of the oceans. The end conclusion of the article: "However, in additionally driving a strong decline in calcium carbonate saturation alongside pH, the current rate of (mainly fossil fuel) CO2 release stands out as capable of driving a combination and magnitude of ocean geochemical changes potentially unparalleled in at least the last ~300 My of Earth history, raising the possibility that we are entering an unknown territory of marine ecosystem change.". Is there a warm and maybe sour future that lies ahead of us? @TheNucleus For a graph look here:
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  5. The Feely article linked by JosHag is OK but there is a better one (also by Feely and written for a general audience) here. It is part of a special issue devoted to ocean acidification. Closer to home, if you mean 'recent' = 'last few years' then we gave a plot here at SkS based on the same data as the Feely plot. The plot, (second figure in the post, labelled Figure 6) shows (as do the Feely papers) measured and 'calculated' pH for the Hawaii Ocean Time Series (HOTS). (We just thought their figure was a bit ugly and we wanted to check their calculations using our own program). It is important to note that 'calculated' pH does not mean a guess. As we explained in the post, the marine carbonate system can be completely described with any two of the 4 marine carbonate parameters. The parameters are 'total carbon', 'total alkalinity', 'total pH', and pCO2 (or fCO2). (see note 1, note 2) These carbonate parameters are a bit like using trigonometry to solve a right angle triangle. Sometimes you might measure the hypotenuse and other times you might calculate it using the sine of an angle. But it would be foolish to say that because you had not directly measured the hypotenuse that any calculation was dodgy. Similarly, pH can be calculated from other measured carbonate parameters. (see note 3) pH for other definitions of 'recent' will be discussed in our next series (I know, I know, it is taking a while). Note 1: 'total pH' (pHT) refers to one of several pH scales – kind of like oF and oC are different scales for temperature (interconversion is possible between pH scales but is not as simple as temperature conversions). Note 2: alkalinity has a complex definition but it is not the opposite of 'acidity' – see our OA series for details. Note 3: There are several sets of internally consistent constants used in the calculations. The different sets perform better or worse depending on the input parameters (e.g. pH or alkalinity)and other environment describing factors (like salinity and temperature).
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  6. The PETM was an epochal event featuring the effect of the Indian subcontinent grinding into the southern borders of the Eurasian continent. It produced repeated stress fracturing all around the Eurasian continent. The result was oceanic-driven toxic acidity over millennia. The KT boundary featured oceans drenched in the downpour of atmospheric dust from the Chicxulub impact. Ocean poisoning was a key feature. The Great Dying of the Permian sea-featured one of three extinction processes - a massive oceanic die-off from ubiquitous dead-zones. Now industrial civilization beats the rate of disruption from any of those events ... and it won't have much effect. Okay, not much other than reef collapse, shell dissolution, reproductive cycle inhibition, and weakened resistance to disease and predation. Congrats, the winning ticket in the Great Bonehead Lottery is 'collapse due to pollution'. Best supporting perp award goes to - 'did nothing with the knowledge for half a century'.
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  7. Owl905 - "The PETM was an epochal event featuring the effect of the Indian subcontinent grinding into the southern borders of the Eurasian continent. It produced repeated stress fracturing all around the Eurasian continent. The result was oceanic-driven toxic acidity over millennia." That doesn't seem very likely. The PETM carbon isotope excursion happened in less than 20,000 years, there is no plausible volcanic/tectonic mechanism that could have caused such an abrupt event. I know James Hansen has made the same claim, but it does not stand up to scrutiny. It is, however, probable that the exposure of new rock, through India smashing into Asia, helped in rapid draw-down of atmospheric CO2 through the process of chemical (silicate/carbonate) weathering. "The KT boundary featured oceans.......... The Great Dying of the Permian" An interesting feature of the very latest research emerging from these extinctions events is that ocean acidification may have been a common 'kill mechanism". It's likely that other factors, such as ocean anoxia, played a part, but it's remarkable that so many different researchers are zeroing in on ocean acidification. SkS will cover many of these studies in the not-too-distant future.
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  8. @Rob Painting - it may not sound very likely to you, but the activity around the plates co-incides with the Indian plate interacting with the Asia plate, subduction/mountain raising, the closing of the Tethys Ocean, and a rearrangement of ocean currents. It co-incides with evolutionary jumps with species like the ancestors of the whale. It co-incides with a breakup of the South America connection to Antarctica to Australia. As well, your unsupported claim about "rapid" CO2 draw-down relating to India "smashing" into Asia is just nonsense - the start to end collision was a 40million-year process. (-Snip-). The ocean anoxia phenom is nothing new - Sciam was delivering article research about the food-chain collapse in the oceans for most, if not all extinctions, 15 to 20 years ago. The ocean-acidification isn't a new idea, but ... so what? Map of the world 50-60mya A megatrend - India pushing into Asia and the rise of the Himalaya's. (-Snip-).
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    [DB] Please model the type of tone and comment you expect from others.

    Inflammatory snipped.

  9. Owl905 - "@Rob Painting - it may not sound very likely to you..." Nor to experts on the PETM either. Note Jerry Dickens comments in the SkS post: CO2 Currently Rising Faster Than The PETM Extinction Event he states: "With all deference to Dr. Hansen, this idea makes no sense given the timing. The massive carbon injection at the onset of the PETM happened within a maximum of 60,000 years, and probably less." Dr Dickens is one of the most published scientists on the subject of the PETM, but it doesn't take a genius to appreciate his point. "As well, your unsupported claim about "rapid" CO2 draw-down relating to India "smashing" into Asia is just nonsense - the start to end collision was a 40million-year process." Internal consistency is not your forte is it? If the process occurred over 40 million years, how exactly did it cause an event lasting 20,000 years? Some citations of peer-reviewed literature would be useful here, otherwise it is just your unsupported inexpert opinion. It would also benefit you to read studies, or watch some videos, on the chemical weathering process. Work by James Kasting, Robert Berner or Lee Kump would be a good start. As too would the video lecture by Richard Alley: The Biggest Control Knob: Carbon Dioxide in Earth's Climate History
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  10. There are many things that we can say with confidence about the PETM (likes the lower limit on the rates of acidification, timing constraints etc.) but I dont think cause is one of them. This is an active research area with many problems to solve - I'd keep away from definitive statements until some of the dust has settled. Oh, and watch the journals...
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  11. I have heard the objection that since ph fluctuates widely on a daily basis that this measurement of a average ocean ph level is useless. I get the feeling that this argument is akin to the bit of sophistry that involves the same argument we hear in regards to measuring global temperature.
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  12. Well paleoclimate cant actually measure pH directly. Instead the studies infer carbonate compensation depth which is a meaningful, ocean pH measure. Let's see the evidence that this fluctuates wildly.
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  13. Scaddenp...Don't they use delB-11 in borate to estimate past variations in pH? That is a more direct measure supposedly. It doesn't vary much either I believe.
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  14. Yes, but note a lot of research on its accuracy. The inferred changes in CCD is what I understand underpins the PETM event.
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  15. Trent1492 @ 11 - funny how ancient ocean acidification episodes have exterminated many calcifying (calcium carbonate shell/skeleton-building) marine life though eh? Evolution does not confer upon species magical invulnerability to rapid change. We are seeing that already off the Pacific Coast of North America, where large natural variations in pH are common. Shellfish have adapted to these conditions, but are presently struggling with ocean acidification. Pacific oyster larvae now being dissolved by the corrosive waters there.
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  16. Scaddenp...Understood. My question wasn't to do with the PETM so much as your response to Trent1492s query about variability in pH.
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  17. We have emitted 500+ gigatonnes carbon so far and will emit another 300 gt carbon in the next thirty years. If the PETM resulted from a 2100gt carbon release we will be halfway there pretty soon. In 1950 there were 2.5 billion people and Co2 emissions at 5gt annually, there are currently 7 billion people and we collectively emit 30 gt Co2 each year. In order to get Co2 emissions back to 1950 levels every human on earth would need to reduce their individual contribution to less than one ton Co2. The oceans were acidifying even at the Co2 emission of the 1950s. Does anyone out there have any idea how to get 7,8, or 9 billion people to voluntarily comply? Is anyone reading this trying to live on less than one ton of Co2?
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  18. Bruce - "Does anyone out there have any idea how to get 7,8, or 9 billion people to voluntarily comply?" People can either change, or the planet will make them change. The laws of physics cannot be repealed. "Is anyone reading this trying to live on less than one ton of Co2?' Perhaps your question should be addressed to those who seek to thwart the move to sustainable forms of energy? Everyone else isn't addicted to the idea of burning fossil fuels for energy.
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  19. Rob, o.k. We need to beat the drum but I am both a farmer and a fisherman. It is about impossible to produce fish for sale and avoid enormous fuel consumption. Small scale farming can be much more energy efficient but where I live (calif.) we aren't really fed by small scale farming. I have been pushing the ocean acidification message for five years, I was in the acid test movie but people don't understand the bottom line. Whether you're an australian or a u.s. consumer on average you are responsible for about 17 tons of Co2 emissions . We need to get that down to less than one ton. I'm not trying to bait anyone but let's get real , we need good working models for how to pull this off. How do we(and I'm trying) produce food with extremely low fossil fuel consumption? Energy in and calories out gallons of fuel consumed and pounds of food produced. Numbers Rob, what does it take ? Please excuse my frustration but I have used up 5 years of the 20 or 30 years I think we have to make the necessary changes , changes 7 billion of us need to make. I know the odds. I know the price of failure
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  20. Suggested reading: “In Fight to Save Coral Reefs, Finding Strategies that Work” posted by Dusti Becker, Yale Environment 360, Mar 13, 2012 In four decades as a marine biologist, Nancy Knowlton has played a key role in documenting the biodiversity of coral reefs and the threats they increasingly face. In an interview with Yale Environment 360, she assesses the state of the world’s corals and highlights conservation projects that offer hope of saving these irreplaceable ecosystems. To access this informative article, click here .
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