Study: Ancient ocean oxygen levels associated with changing atmospheric carbon dioxide

A Texas A&M-led study analyzed ocean floor sediment cores to provide new insights into the relationship between deep ocean oxygenation and atmospheric carbon dioxide levels in the 50,000 years before the last ice age

Texas A&M UniversityShare Print E-Mail

IMAGE
IMAGE: Deep ocean floor sediment cores hold chemical clues to Earth’s past. view more  Credit: Texas A&M University

Why do carbon dioxide levels in the atmosphere wax and wane in conjunction with the warm and cold periods of Earth’s past? Scientists have been trying to answer this question for many years, and thanks to chemical clues left in sediment cores extracted from deep in the ocean floor, they are starting to put together the pieces of that puzzle.

Recent research suggests that there was enhanced storage of respired carbon in the deep ocean when levels of atmospheric carbon dioxide concentrations were lower than today’s levels. But new research led by a Texas A&M University scientist has reached back even further, for the first time revealing insights into atmospheric carbon dioxide levels in the 50,000 years before the last ice age.

“One of the biggest unknowns about past climate is the cause of atmospheric carbon dioxide variability over global warm-cold cycles,” said Franco Marcantonio, lead author of the study and professor and Jane and Ken R. Williams ’45 Chair in the Department of Geology and Geophysics at Texas A&M. “Here we investigated the ‘how’ of varying carbon dioxide with the ‘where’ — namely, the Eastern Equatorial Pacific Ocean, which is an important region of the world ocean where, today, significant carbon dioxide is exhaled into the atmosphere and the greatest rates phytoplankton growth are found.”

The National Science Foundation-funded research was recently published in Scientific Reports, a Nature Research journal.

To examine ancient carbon dioxide levels, Marcantonio and a team of researchers analyzed an ocean floor sediment core extracted from the deep Eastern Equatorial Pacific Ocean. The 10-meter long core spans about 180,000 years, and the chemistry of the layers of sediment provide scientists with a window into past climates. The chemical measurements they make serve as a proxy for oxygen levels of the deep sea.

Measuring minute traces of uranium and thorium isotopes, the team was able to associate periods of increased storage of respired carbon (and low deep-sea oxygen levels) with periods of decreased global atmospheric carbon dioxide levels during the past 70,000 years.

“By comparing our high-resolution sediment record of deep-sea oxygenation in the Eastern Equatorial Pacific with other areas of the Pacific and Southern Ocean, we find that the Pacific Ocean, like the Southern Ocean, is a location for deep-ocean respired carbon storage during periods of decreased global atmospheric CO2 concentrations,” he said. “Importantly, we put constraints on the location in the water column of the extent of the respired stored carbon pool during cold periods.

“Understanding the past dynamics of Earth’s carbon cycle is of fundamental importance to informing and guiding societal policy-making in a warming world with increasing levels of atmospheric carbon dioxide.”

Co-authors of the study were Ryan Hostak, a former Texas A&M graduate student who earned his master’s degree in geology in 2019; Jennifer E. Hertzberg, who received her Ph.D. in oceanography from Texas A&M in 2015 and is now a postdoctoral researcher in the Department of Earth, Ocean and Atmospheric Sciences at Old Dominion University; and Matthew W. Schmidt, associate professor of Ocean, Earth and Atmospheric Sciences at Old Dominion. Marcantonio and his colleagues designed the study, he and Hostak performed the isotope analyses, and the team interpreted the data.

“By performing similar studies in sediment covering a wider swath of the deep Pacific Ocean, we’ll be able to spatially map the extent of this past deep pool of respired carbon,” Marcantonio said, looking forward to future research.

###

The study’s radiogenic and trace element analyses were conducted in the College of Geosciences’ R. Ken Williams Radiogenic Isotope Facility. The sediment core was extracted by Marcantonio and colleagues on an NSF-funded research cruise aboard the R/V Melville in 2010.

From EurekAlert!

Advertisements

34 thoughts on “Study: Ancient ocean oxygen levels associated with changing atmospheric carbon dioxide

  1. “Why do carbon dioxide levels in the atmosphere wax and wane in conjunction with the warm and cold periods of Earth’s past? Scientists have been trying to answer this question for many years, and thanks to chemical clues left in sediment cores extracted from deep in the ocean floor, they are starting to put together the pieces of that puzzle.”

    Experiments with warm and cold beer and champagne would have solved this mystery for the scientists.

  2. Do they know inter-glacial periods occur within ‘ice ages’? 180Kya isn’t back to the last ice age.

    • But 180Ky is interglacial between the last ice age and the upcoming one.

    • yeah.
      It probably was saying 50,000 year before the beginning of last Glaciation period??

      And, would that not have been somewhere before the beginning of the Last interglacial period called the
      Eemian??
      Wiki says: Eemian was the interglacial period which began about 130,000 years ago at the end of the Penultimate Glacial Period.
      So somewhere during the “Penultimate Glacial Period”. Or somewhere in middle of second to last glaciation period.
      But it’s all the Ice Age

    • You’re absolutely correct. The authors have an incorrect view of geologic history. We’ve been in an ice age for about 2.5 million years. They first need to get the basic fact right.

      • Or the past 34 million years, if you date the Cenozoic Ice Age from the onset of Antarctic ice sheet glaciation, caused by the formation of the Southern Ocean, with deep channels between Antarctica and South America and Australia.

        Its Plesitocene, Northern Hemisphere phase began about 2.6 Ma, after the Isthmus of Panama interrupted tropical oceanic circulation.

  3. “One of the biggest unknowns about past climate is the cause of atmospheric carbon dioxide variability over global warm-cold cycles,”

    There is an Aggie joke in there somewhere. (Native Texan speaking)
    No Aggie has been smart enough to notice how a warm soda and cold soda react differently when shaken and opened?

    • These are the same people who believe in the 12th man. I you really played 12 on 11 over the last 30 years you should be about 390 – 0. Go figure?

    • Why yes they did, to wit : “By comparing our high-resolution sediment record of deep-sea oxygenation in the Eastern Equatorial Pacific with other areas of the Pacific and Southern Ocean, we find that the Pacific Ocean, like the Southern Ocean, is a location for deep-ocean respired carbon storage during periods of decreased global atmospheric CO2 concentrations,”. This is quite interesting because it means that during cold periods (low CO2) , carbon is being stored in the ocean, which is what you would expect as more CO2 is contained in the oceans during cold periods. As the oceans warm, CO2 is given off and less carbon is stored in the oceans. This fits perfectly with atmospheric CO2 changes lag ocean temperature, i. e., warming oceans increase atmospheric CO2. Of course it would have killed funding to state that explicitly.

      • No reason to put the funding at risk when you can claim that this is just confirming evidence that the cold periods are brought on by inexplicable sudden increases in carbon dioxide storage while the warming periods must be due to similarly inexplicable sudden releases of carbon dioxide (such as has been proven to be the case in modern times, as the prophets have foretold).

        That’s far more scientific than to say that increased CO2 storage resulted from cooler oceans and decreased storage from warmer oceans, dontchaknow? Settled science and all that!

        Note the EurekAlert! catchphrase “In a warming world with increasing levels of atmospheric carbon dioxide.”

  4. First, let’s get the terms correct. 50,000 years before the last ice age which is what we are in now is something like 1.2 million years ago. Really?

    We are in an ice age comprised of glacial and interglacial periods, roughly 90,000 years of glacial and 10,000 years of interglacial, alternating. So, what they really mean is that they are looking at 50,000 years back from this interglacial or 50,000 years before the last glacial? Which would be the middle of the glacial period before our last one. They really need to get their timelines in line.

    I glean that they are really talking about the middle of the most recent glacial period but . . . what does that mean for the cogency of their work?

  5. “Understanding the past dynamics of Earth’s carbon cycle is of fundamental importance to informing and guiding societal policy-making in a warming world with increasing levels of atmospheric carbon dioxide.”

    Even more important is the understanding of the current dynamics of earth’s carbon cycle. The random variations and uncertainties in these flows for example. Carbon cycle flows are an order of magnitude greater than fossil fuel emissions such that even their variations and flow uncertainty are greater that fossil fuel emissions. In this mix, it is not possible to even detect the presence of fossil fuel emissions let alone compute the impact of fossil fuel emissions on atmospheric composition.

    https://tambonthongchai.com/2018/05/31/the-carbon-cycle-measurement-problem/

    https://tambonthongchai.com/2018/12/19/co2responsiveness/

    Postscript: The phrase “respired carbon” occurs in the text at least 5 times. How was it determined that it was respired carbon? and respired by land creatures or by sea creatures? 150,000 years is a long time ago. C14 has a half life of 5,000 years.

  6. As CO2 does not drive the climate and natural processes have the penchant to permanently sequester CO2, basically trying to kill life on Earth, we only survive by volcanic emissions and periodically warming oceans. The assumption that Earth has a balance is completely wrong. We are in a life struggle to have enough CO2 to survive.

    If you look at the CO2 concentrations over the last 600 million years it is clear that CO2 has been steadily decreasing, saved occasionally by huge eruptions like the Siberian traps.

    • “…saved occasionally by huge eruptions like the Siberian traps.”

      Maybe the Siberian traps gave so much CO2, that plant life has become excessively
      gluttonous.

      Btw, when in history of Earth has trees been bigger?

      • Redwoods, eucalyptus or other groups might have grown taller and bigger in the Mesozoic or early Cenozoic, when Earth enjoyed up to five times as much plant food in its air as now.

    • Yes, exactly whole life is dependent on carbonates from sea floor cooking by volcanic processes, delivered by plate tectonics. Any previous local maximum or minimum in content of carbon delivered to volcanoes is mirroring on current CO2 situation.
      Whole life on Earth is similar to bacteria colony in Petri Dish, consuming all sources and die off. Our source is CO2. We have some replenishment driven by Sun, aka tectonics. If life flourishes too much, it consumes too much, will die off and after CO2 recovery it will reappear.

  7. The problem is that no one can definitively explain the warm periods, therefore ease with which many can blame CO2. “Increased CO2 levels in the atmosphere cause the warming – we know this because there is no other good explanation…”

    The problem is of course that temperatures begin to increase before CO2 begin to rise. This leads to the belief by skeptics (myself included) that CO2 is a symptom of warming, not a cause – or at least not an initial cause although it could play a role once warming begins.

    If you achieve an equilibrium (or at least approach one) with dissolved CO2 levels in the oceans and then those levels decrease, the sediments should return some CO2 to the waters. Some chemical reactions might slow down due to a decrease in ion availability, but then if the waters are warming that should also increase some reaction rates. Like anything in nature, it’s complicated.

    The initial warming is likely caused by more than one forcing, and it could be different forcings for different warming events. Nature does not care that some scientists are so dim they think everything has to be easily explained. My own belief is that the Sun likely play’s a big role in the initial warming – and it could be at the higher wavelengths. Orbital values play another. It’s probably when several of these overlap that a large warming event begins.

    If CO2 starts playing a role once the warming begins, it would not surprise me. It would not surprise me that fossil fuels contribute as much as 5% of the total warming by CO2 in the atmosphere, and I could be convinced that as much as half of the observed warming is caused by additional CO2 in the atmosphere (the rest is either noise, contaminated data, or other causes) (NOTE: I could also be convinced that CO2 plays a much smaller role, but first I need to see non-contaminated data that is up to the analysis). So if you do the math, mankind burning fossil fuels could be responsible for as much as 2.5% of the observed warming – not enough for me to get excited or worried about.

    • In this respect 2.5% = 0
      It certainly doesn’t justify imploding western civilization
      But to many it does
      Climactically insane

    • Like stealing police cars because they thought they were Porsches? 🤣🤣🤣🤣

  8. With all these newly minted thousands and thousands of Phd students graduating in the climate sciences every year across the planet, how are they all going to make a living? How many climate scientists are we going to need to justify their employment through academic studies that keep telling the same story, that CO2 done it all? And if/when there is no climate crisis, will they still get their tax payer funded pensions in 40 years? Seems to be a like a liberal arts degree now, especially they can’t even think for themselves anymore, nor would it be allowed. Maybe the kids are right..I’m just a grumpy Old Fogey now.

  9. Why is the quality of university research so very very bad these days. I would never have been permitted to publish work of this quality to avoid bringing the company and university into disrepute.

    I simply cannot understand this.

    • Let us not forget that what we are looking at is not the paper itself. It seems to be a press release written by a “Communication Specialist” who seems not to have understood anything at all about the paper. The paper is at https://www.nature.com/articles/s41598-020-63628-x and appears to be relatively coherent. After reading the paper, I’m still not sure what it’s trying to tell me. But it looks like it probably contains information that a reasonable person who for some reason cares about Pleistocene sea bottom Oxygenation levels (That’s for sure not me) would find of interest.

  10. An I missing something here? Surely the outgassing occurs because the ocean temperature has risen and conversely when the ocean temperature falls the gasses are once again dissolved. What they need to discover is why the ocean temperature goes up and down. Everything else follows from that. Climate scientists always seem to have the cart before the horse.

  11. It’s a simple matter of “cause and effect”. When the Sun warms the atmosphere and ocean it increases CO2 outgassing from ocean. Raising CO2 levels in atmosphere and lowering CO2 levels in ocean. When the Sun cools the atmosphere and ocean more CO2 is dissolved into ocean lowering atmospheric CO2 and raising ocean CO2. The bottom line is its no mystery its the SUN

    • And Milankovitch forcing cycles that can (de) amplify insolation at longer time cycles, including other longer term Sun/orbital variations about the Milky Way. I too think the Sun has a lot do with things, especially short term sine wave climate oscillation on a periodic basis of 60-65+ years (120-130+ years for a full cycle) Things get slightly colder for 30+ years and slightly warmer for 30+ years, and sometimes the Sun goes to sleep in grand minimums and we get less energetic spectrum from the Sun over longer time scales like the LIA. I don’t think we completely understand everything yet, which is why the (climate) science should never be settled. But shirly no one can believe that CO2 is the dominant control knob on long term climate oscillations. CO2 is the symptom, not the cause. If there was any reason for humans evolving on the good Earth in the long term scheme of things, it was to put more life sustaining CO2 into the atmosphere and thank God for that.

  12. IntroductionThe dominant signal in global climate over the last 800,000 years is the 100-kyr co-variation of air temperature and atmospheric CO2 concentrations observed in the EPICA Antarctica ice core1. The temperature variations are likely modulated by the 100-kyr eccentricity signal and amplified by climate feedbacks which involve atmospheric CO2.

    Introduce presumptions and assumptions using waffle words; “dominant signal”, “likely modulated”, “amplified by climate feedbacks”, “involve”.

    Here we present high-resolution proxy data of bottom water oxygenation (authigenic U, see Methods)

    Merriam-Webster for authigenic: “formed where found —used of mineral particles of rocks formed by crystallization in the place they occupy”

    Why authigenic Uranium would form is ignored, especially since the uranium is formed from soluble U.

    “Thus, although the EEP is a net CO2 source to the atmosphere today, it could easily have been a CO2 sink in the past,

    More assumptions and speculative fantasy.

    “Here we present high-resolution proxy data of bottom water oxygenation (authigenic U, see Methods), biological productivity (230Th-derived excess Ba (xsBa) flux, see Methods), and dust (230Th-derived 232Th flux, see Materials and Methods) flux from a high-sedimentation-rate core collected on the Cocos Ridge bordering the Panama Basin of the EEP (MV1014-8JC (8JC), 6°14.0′N, 86°02.6′W; 1993 m water depth).”

    Note the conflation assumption that “high sedimentation” equals “high resolution”.

    1,993 meters is 2,180 yards or 6,540 feet deep.
    Simply stated as 1.24 miles deep.

    “Our record spans the past 180 kyr beginning in the penultimate glacial period (Marine Oxygen Isotope stage, MIS 6).”

    Don’t you just love when people use powerful sounding words for emotive response!? penultimate means “next to the last”.

    “We compare our new record with that at the equator (MV1014-17JC11) and attempt to unravel the relative contributions of organic matter flux and bottom water oxygen concentrations to pore water redox conditions.”

    “Attempt”? “Relative”?

    “Increases in aU concentrations in each of these records during the most prolonged periods of low glacial atmospheric CO₂ levels have been hypothesized to represent decreases in bottom water oxygen concentrations and, by inference, increased storage of respired carbon in the deep ocean at these locations.”

    “Hypothesized”? “By inference”? Speculative assumptions that the authors use to connect their 1.24 mile deep ocean floor core to atmospheric CO₂ obtained from surface cores of ice.

    Suure they did…

  13. Most people do not have a clue how minute those traces of CO2 are and how much smaller are the changes. The proverbial needle in the haystack is children’s play compared to that. Today’s CO2 concentration in the air is 0,04%. Thats 4 hundredths of one percent. Any variance is smaller still. And this minuscule amount of gas shall driver temperature? Yeahh right.

  14. Going to the paper (always best to ignore the dumbed down rehash) it’s a complex study of gas fluxes in the ocean in relation to plankton productivity and variables like temperature and atmospheric CO2. And “export production” which means organic material from the sea surface falling to the ocean floor. One important finding is a positive correlation between atmospheric CO2 and oxygenation of ocean bottom water. More CO2 in the atmosphere means more O2 in the deep ocean.

    This makes sense – the source of oxygen is photosynthesis by marine plankton and that is going to be enhanced by increased CO2. More CO2 leads to more O2 and vice versa.

    Reading this reminded me of a paper that suggested that the end Permian extinction (“the great dying”) was a catastrophe caused by CO2 starvation. In the context of this paper that makes sense. Low CO2 leads to anoxia (low oxygen) at the ocean floor as measured in this study by the aU uranium chemical marker.

    At the end Permian great dying, 96% of marine species died and much of the ocean became anoxic. This could be a consequence of a very low atmospheric CO2 concentration.

    All this reinforces how insanely dangerous it is to label CO2 as an enemy. It is good for the biosphere in every possible way. It is as central to multicellular life as oxygen – O2 and CO2 are flip sides of the same coin. And idiotically dangerous geo-engineering schemes aimed at reducing atmospheric CO2 represent a suicidal attempt to recreate the end-Permian great dying.

Comments are closed.