Strong warming causes the deep overturning circulation to collapse.
The University of California, Irvine Earth system scientists have found that the Atlantic and Southern oceans’ deep circulation patterns are slowing down due to climate-driven heating of seawater. If this continues, the ocean’s ability to remove carbon dioxide from the atmosphere will be greatly hindered, intensifying the effects of global warming.
A recent study published in Nature Climate Change by these researchers found that the Atlantic Meridional Overturning Circulation and the Southern Meridional overturning Circulation may slow by up to 42% by 2100. The worst-case scenario of the simulations even suggests that the SMOC could completely stop by 2300.
“Analysis of the projections from 36 Earth system models over a range of climate scenarios shows that unchecked global warming could lead to a shutdown of the ocean deep circulation,” said co-author J. Keith Moore, UCI professor of Earth system science. “This would be a climate disaster similar in magnitude to the complete melting of the ice sheets on land.”
The importance of overturning circulation
In the Atlantic, as warm water flows northwards on the surface, it cools and evaporates, making it saltier and denser. This heavier water sinks into the deep ocean and proceeds to the south where it eventually rises back up, carrying from the depths the nutrients that are the food foundation of marine ecosystems.
In addition, globe-spanning ocean circulation creates a powerful factory for the processing of atmospheric carbon dioxide. The basic physical and chemical interaction of seawater and air – what Moore and his colleagues call a “solubility pump” – draws CO2 into the ocean. While ocean circulation sends some carbon back to the sky, the net amount is sequestered in the ocean’s depths.
Additionally, a “biological pump” occurs as phytoplankton use CO2 during photosynthesis and in forming carbonate shells. When the plankton and larger animals die, they sink, slowly decomposing and releasing the carbon and nutrients at depth. Some comes back up with circulation and upwelling, but a portion remains banked beneath the waves.
“A disruption in circulation would reduce ocean uptake of carbon dioxide from the atmosphere, intensifying and extending the hot climate conditions,” Moore said. “Over time the nutrients that support marine ecosystems would increasingly become trapped in the deep ocean, leading to declining global-ocean biological productivity.”
Humans depend on the solubility pump and the biological pump to help remove some of the CO2 emitted into the air through fossil fuel burning, land use practices, and other activities, according to Moore.
“Our analysis also shows that reducing greenhouse gas emissions now can prevent this complete shutdown of the deep circulation in the future,” he said.
Reference: “Reduced CO2 uptake and growing nutrient sequestration from slowing overturning circulation” by Y. Liu, J. K. Moore, F. Primeau and W. L. Wang, 22 December 2022, Nature Climate Change.
The study was funded by the U.S. Department of Energy. The study depended substantially on simulations developed by the Coupled Model Intercomparison Project phase 6 (CMIP6) project used to inform the IPCC climate assessments.
Could? May? What is the numeric probability +/-10%? Is the “worse-case scenario” the infamous RCP 8.5 emissions scenario that has been shown to be improbable? Are these the same models (CMIP6) that are running even warmer than the past generation models (CMIP5) that are admitted to be running warmer than actual?
Significant fossil fuel use for energy is improbable by 2300 as it becomes more expensive and technological advances are made for alternative energy. Even if controlled thermonuclear fusion should prove to be an intractable problem, there are, even now, designs for thorium-based fission reactors that have answered most of the objections to ‘nuclear’ power.
Highly speculative at best (and therefore worthless), but that’s what you do, here and elsewhere. Still getting those payments from Big Oil?
Payments? I wish! If speculations are worthless, as you claim, why should anyone pay attention to claims that something could or may happen? How could anything be more speculative than that?
For the record, the master that I serve is Truth.
Why would you accuse me, or anyone, of receiving payments from “Big Oil?” Even it it were true, which it isn’t, there is no way that you could prove the claim. In other words, you are knowingly claiming something for which you neither have proof or could obtain proof. What does that say about you?
It says that I won’t bother to engage in the necessary research to prove where you are receiving your funding. Your posting history indicates that you are HEAVILY engaged in constantly promoting bogus theories to disprove climate change, warming, anthropogenic sources and so on.
To be so engaged like this indicates that yes, you are indeed being supported in some fashion or another to poison the well on real climate websites.
For example, you post on WattsUpWithThat, Judith Curry, known climate denialists sites and sources (which you constantly reference).
You claimed “Anthropogenic CO2 is virtually constant compared to the seasonal variations of the natural sources and sinks. The monthly anthropogenic flux change is much smaller than the uncertainty in the net global monthly flux changes. Therefore, there is no support for the claims about anthropogenic CO2 driving the annual changes.”
Which is flatly false and untrue as the historical record clearly shows. Basically, you are constantly employed to spread lies and bullshit which makes no sense at all unless this is profitable for you.
I don’t need to “prove” where your funding comes from – you’re actions and your efforts are clear to see. You consistently seek to poison real science and research with your bogus claims and clearly have a vested interest in doing so.
Nothing you posit or post is worth reading, it’s utter garbage from a denialist who obviously has an axe to grind against real science.
6 words to address this junk science: maximum frequency absorption has been reached.
Robert, you are the problem, this trolling and denying real science, real risk, maybe only proved when it is too late, makes you look a real lazy turd person, I think you are a Dark Triad a hole, tell me I’m wrong. Your heart is empty, so is your head apparently. Asserting is not an argument, try less junk posting if you want less junk online, ok? Passing grade 10 basic science does not make you fit to have an opinion and I doubt you have credentials beyond that, tell me I’m wrong.
Denying real science??? By an ugly personal attack? Yes, that’s wrong.
Nice that this will probably not happen, according to this study, as we will almost certainly be able to reduce climate gas presence by the year 2100.
“…a range of climate scenarios shows that unchecked global warming could lead to a shutdown of the ocean deep circulation.”
So, how will lowering of our CO2 emissions to zero by 2050 possibly affect the shutdown of ocean circulation? That’s absurd. There is nothing humans can do that could possibly affect that. This is junk science.
I’m a lay person for sure, but I think that you have it backwards. I think that if we DON’T lower CO2 emissions it could affect the ocean currents. Models are just that; models. It’s not junk science to speculate, its all we have to formulate strategies moving forward. I don’t think anyone who charges “junk science” is in a position to judge.
This is a quick overview of how some proposals might reduce SOME of the carbon: https://www.youtube.com/watch?v=wOmmKTDSWCY
Even the most optimistic claims in this presentation likely won’t be enough.
The issues surrounding ocean circulation have been known (and warned about) for years. It’s extremely doubtful that C02 emissions will be reduced sufficiently to stop the heating of seawater. It actually does not make a lot of sense to make that claim, precisely because of all of the global ice that will be missing.
I’ve pointed out for years that we cannot replace the missing ice, and yet “studies” that ignore this critical element for helping to regulate heating, albedo and cooling tend to ignore this all too often.