Oceans losing oxygen mainly due to global warming, say researchers — but what about CO2?

Posted: April 16, 2021 by oldbrew in Ocean dynamics, research
Tags: ,
ocean_co2

The ocean carbon cycle [credit: IAEA]

Quoting from the article: ‘The main reason for this is global warming, which leads to a decrease in the solubility of gases and thus also of oxygen.’ Surely the same applies to carbon dioxide (CO2): warmer water causes release of some of it from the oceans into the atmosphere? Diagrams of the Earth’s natural carbon cycle seem conclusive enough.
– – –
The life of almost all animals in the ocean depends on the availability of oxygen, which is dissolved as a gas in seawater, says Phys.org.

However, the ocean has been continuously losing oxygen for several decades. In the last 50 years, the loss of oxygen accumulates globally to about 2% of the total inventory (regionally sometimes significantly more).

The main reason for this is global warming, which leads to a decrease in the solubility of gases and thus also of oxygen, as well as to a slowdown in the ocean circulation and vertical mixing.

A new study published today in the scientific journal Nature Communications shows that this process will continue for centuries, even if all CO2 emissions and thus warming at the Earth’s surface would be stopped immediately.

“In the study, a model of the Earth system was used to assess what would happen in the ocean in the long term if all CO2 emissions would be stopped immediately,” explains the author, Professor Andreas Oschlies from GEOMAR Helmholtz Centre for Ocean Research Kiel. “The results show that even in this extreme scenario, the oxygen depletion will continue for centuries, more than quadrupling the oxygen loss we have seen to date in the ocean,” Oschlies continues.

The long-term decrease in oxygen takes place primarily in deeper layers. According to Prof. Oschlies, this also has an impact on marine ecosystems.

A so-called ‘metabolic index,” which measures the maximum possible activity of oxygen-breathing organisms, shows a widespread decline by up to 25%, especially in the deep sea (below 2000 meters).

This is likely to lead to major shifts in this habitat, which was previously considered to be very stable, explains the oceanographer. These changes have already been initiated by our historical CO2 emissions and are now on their way to the deep ocean.

He recommends that a comprehensive investigation of the deep ocean habitat, which has only been studied randomly so far, should take place before this environment, that is deemed as having been stable for many millennia, is likely to change significantly due to the now expected decrease in oxygen.

Full article here.

Comments
  1. Oxygen in the oceans.
    , a model of the Earth system was used to assess what would happen in the ocean in the long term if all CO2 emissions would be stopped immediately,” explains the author, Professor Andreas Oschlies

    The long-term decrease in oxygen takes place primarily in deeper layers. According to Prof. Oschlies,

    a widespread decline by up to 25%, especially in the deep sea

    He recommends that a comprehensive investigation of the deep ocean habitat, which has only been studied randomly so far

    In other words, he is writing scary stuff to promote fear because fear sells. He used a model, like he understands the oceans well enough to write a correct model. He only has a few random measurements and no idea what they mean. It is easy to find places in the oceans where Oxygen is low.

    Sea creatures move around because they can do go to where the conditions are better.

  2. Graeme No.3 says:

    The cure is simple, confiscate the computers of all Climate “Scientists”. No more computer models, they might have to do some measurements. A thorough survey of even one ocean would take them a lifetime. I nominate the Southern Ocean where the white pointers roam.

  3. Phil Salmon says:

    You’re not allowed to talk about more than one thing in a scientific paper on climate. “Warming – bad” – that’ll do nicely. Oxygen and CO2 – that’s two things. Too many.

  4. Phil Salmon says:

    Not to mention plain wrong.
    Counter-intuitively, increasing CO2 in the atmosphere actually increases oxygenation of the deep ocean:

    https://www.nature.com/articles/s41598-020-63628-x

    https://ptolemy2.wordpress.com/2020/10/14/atmospheric-co2-is-good-for-the-deep-ocean/

  5. Gamecock says:

    Oxygen in sea water comes from photosynthesis. Increased (allegedly) temperatures would result in MORE photosynthesis.

  6. Curious George says:

    Would an increased CO2 in sea water, combined with a speculated increase in temperature, boost an oxygen production by sea plankton and sea weed?

  7. In other words, natural responses of the self correcting climate system takes care of any out of balance stuff. If you think about it, if this was not true, our ancestors would have not survived and we would not be here. Our ancestors did not have the means to control trace gases to regulate climate. After fifty million years, one more molecule of CO2 per ten thousand molecules in the atmosphere did not stop the natural self correcting internal cycles that have kept us alive since even before we have good history. now that I think about it, we do not have the knowledge or means to control trace gases to regulate climate, and if we did, it could not work.

  8. oldbrew says:

    Ocean outgassing of CO2 due to higher water temperature is standard physics, the same as a chilled fizzy drink going ‘flat’ if left at room temperature.

    We might then ask: how much of the CO2 rise in the last 200 years or so, as oceans have warmed in the recovery from the Little Ice Age, is due to such outgassing?

  9. Phoenix44 says:

    Seems to me this disproves Climate Change? The ocean contains huge amounts of CO2. Any natural increase in warmth releases CO2. That is claimed to increase warmth which releases more CO2 and so on. Thus there must be runaway global warming if CO2 can continue to increase warming.

  10. tom0mason says:

    I’m so glad we do not live on such a modeled world.

  11. oldbrew says:

    The problem for alarmists being, of course, that historically CO2 increases have followed warming, not caused it. As you might expect with ocean outgassing.

  12. Curious George says:

    Ocean outgassing of CO2 due to higher water temperature is standard physics [Oldbrew at 8:57]
    That applies to a saturated solution. Sea water is very far from being saturated with CO2.

  13. oldbrew says:

    CG – see diagram above: microbial respiration and zooplankton grazing also play a part.
    – – –
    Warmer oceans release CO2 faster than thought

    ‘Rising temperatures make carbon dioxide leak from the oceans for two main reasons. First, melting sea ice increases the rate that the ocean mixes, which dredges up CO2-rich deep ocean waters. Second, “when you warm the ocean up, just like warming up a Coke bottle, it drives the gas out,” says van Ommen.’

    Read more: https://www.newscientist.com/article/dn20413-warmer-oceans-release-co2-faster-than-thought/

  14. Curious George says:

    Oldbrew, that’s one beautiful diagram. It probably works more or less that way, but no data have been provided. Please pay attention to a sentence in your 2011 New Scientist link: “The oceans capture around 30 per cent of human carbon dioxide emissions and hide it in their depths.”

  15. oldbrew says:

    “The oceans capture around 30 per cent of human carbon dioxide emissions and hide it in their depths.”

    Does the carbon *cycle* know which CO2 is human-caused? Historically CO2 has been at much higher levels than today at various times and the planet has not gone haywire, judging by our presence on it today.

  16. Curious George says:

    Oldbrew – it could not care less. There is no such arrow in “your” diagram. Let’s say that the New Scientist is more new than scientist.

  17. Coeur de Lion says:

    The proof of our inability to control CO2, not that it matters, is the unchanged 2ppm/year at Hawaii seen during the COVID de-industrialisation. What will happen as the planet continues to cool?

  18. dennisambler says:

    The trouble with models is that their outcomes are regarded as fact. Those new facts are then input into the next models ad infinitum. And politicians believe what “Scientists Say”

  19. dennisambler says:

    The science is settled:
    “Models designed to represent coastal and shelf sea processes suggest there are large parts of the Celtic Sea, English Channel and Irish Sea that are prone to oxygen deficiency, but data is too sparse in time and space to support these findings. In addition, the ability of models to accurately represent oxygen dynamics is still under debate due to correct representation of physical and biological processes within models.”

    Mahaffey, C., Palmer, M., Greenwood, N. and Sharples, J. (2020) Impacts of climate change on dissolved oxygen concentration relevant to the coastal and marine environment around the UK. MCCIP Science Review 2020, 31–53.

    Or perhaps it’s just more of those annoying long term cycles.
    “The impact of fire on the Late Paleozoic Earth system”
    https://www.frontiersin.org/articles/10.3389/fpls.2015.00756/full

    Data from charcoal abundance in coal indicate a dramatic rise in p(O2) levels during the last 10–15 million years of the Devonian, atmospheric oxygen concentration then remained above present day levels, and usually above 23%, until at least end Permian.

    Levels of p(O2) appear to have peaked in the Middle-to-Late Cisuralian at levels of about 28%, before declining modestly into the Guadalupian and then recovering again in the Lopingian.”

    Current atmospheric oxygen content is 21%

    Also: https://www.livescience.com/56219-earth-atmospheric-oxygen-levels-declining.html

    “Atmospheric oxygen levels have declined over the past 1 million years, although not nearly enough to trigger any major problems for life on Earth, a new study finds.

    “There was no consensus on whether the oxygen cycle before humankind began burning fossil fuels was in or out of balance and, if so, whether it was increasing or decreasing,” said study lead author Daniel Stolper, a geo-chemist at Princeton University in New Jersey.

    Although a drop in atmospheric oxygen levels might sound alarming, the decrease the researchers found “is trivial in regard to ecosystems,” Stolper told Live Science. “

  20. dennisambler says:

    Consider also the effect of “the wonder fuel to be”, hydrogen and its combination with oxygen to form water vapour, the most potent “greenhouse gas”. The government wanted to know about this but they are seemingly not interested in the results from a review they commissioned:

    ‘https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/760538/Hydrogen_atmospheric_impact_report.pdf’

    “This review has identified two global atmospheric dis-benefits from a future hydrogen economy: stratospheric ozone depletion through its moistening of the stratosphere, and contribution to climate change through increasing the growth rates of methane and tropospheric ozone.”

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