Earth

Surprise Discovery: Sleeping Giant Could End Deep Ocean Life

Red Medusa

Red medusa found just off the bottom of the deep sea in Alaska. Credit: Hidden Ocean 2005/NOAA

Continental movement is capable of throttling marine oxygen.

A previously overlooked factor — the position of continents — helps fill Earth’s oceans with life-supporting oxygen. Continental movement could ultimately have the opposite effect, killing the majority of deep ocean creatures.

“Continental drift seems so slow, like nothing drastic could come from it, but when the ocean is primed, even a seemingly tiny event could trigger the widespread death of marine life,” said Andy Ridgwell, University of California, Riverside geologist. Ridgwell is co-author of a new study on forces affecting oceanic oxygen.

As the water at the ocean’s surface approaches the north or south pole, it becomes colder and denser and then sinks. When the water sinks, it transports oxygen pulled from Earth’s atmosphere down to the ocean floor. 

Fish on a deep reef at Pearl and Hermes Atoll in Papahānaumokuākea Marine National Monument near Hawaii. Credit: Greg McFall, NOAA

Eventually, a return flow brings nutrients released from sunken organic matter back to the ocean’s surface, where it fuels the growth of plankton. Today’s oceans feature an incredible diversity of fish and other animals that are supported by both the uninterrupted supply of oxygen to lower depths and organic matter produced at the surface.

New research has found that this circulation of oxygen and nutrients can end quite suddenly. Using complex computer models, the scientists investigated whether the locations of continental plates affect how the ocean moves oxygen around. They were surprised to find that it does.

This finding led by researchers based at UC Riverside is detailed in the journal Nature. It was published today (August 17, 2022).

Resting balloonfish near the Florida Keys. Credit: OAR/National Undersea Research Program (NURP); University of Maine

“Many millions of years ago, not so long after animal life in the ocean got started, the entire global ocean circulation seemed to periodically shut down,” said Ridgwell. “We were not expecting to find that the movement of continents could cause surface waters and oxygen to stop sinking, and possibly dramatically affecting the way life evolved on Earth.”

Up until now, models used to investigate the evolution of marine oxygen over the last 540 million years were relatively simple and didn’t account for ocean circulation. In these models, ocean anoxia — times when oceanic oxygen disappeared — implied a drop in atmospheric oxygen concentrations.

“Scientists previously assumed that changing oxygen levels in the ocean mostly reflected similar fluctuations in the atmosphere,” said Alexandre Pohl, first author of the study and former UCR paleoclimate modeler, now at Université Bourgogne Franche-Comté in France.

Diorama of ancient Ediacaran period sealife displayed at the Smithsonian Institution. Credit: Smithsonian

For the first time,  this study used a model in which the ocean was represented in three dimensions, and in which ocean currents were accounted for. According to the results, collapse in global water circulation leads to a stark separation between oxygen levels in the upper and lower depths.

That separation meant the entire seafloor, except for shallow places close to the coast, entirely lost oxygen for many tens of millions of years, until about 440 million years ago at the start of the Silurian period.

“Circulation collapse would have been a death sentence for anything that could not swim closer to the surface and the life-giving oxygen still present in the atmosphere,” Ridgwell said. Creatures of the deep include bizarre-looking fish, giant worms and crustaceans, squid, sponges, and more.

The paper does not address if or when Earth might expect a similar event in the future. In fact, it is difficult to identify when a collapse might occur, or what triggers it. However, existing climate models confirm that increasing global warming will weaken ocean circulation, and some models even predict an eventual collapse of the branch of circulation that starts in the North Atlantic.

“We’d need a higher resolution climate model to predict a mass extinction event,” Ridgwell said. “That said, we do already have concerns about water circulation in the North Atlantic today, and there is evidence that the flow of water to depth is declining.”

In theory, an unusually warm summer or the erosion of a cliff could trigger a cascade of processes that upends life as it appears today, Ridgwell said.

“You’d think the surface of the ocean, the bit you might surf or sail on, is where all the action is. But underneath, the ocean is tirelessly working away, providing vital oxygen to animals in the dark depths,” Ridgwell said.

“The ocean allows life to flourish, but it can take that life away again. Nothing rules that out as continental plates continue to move.”

Reference: “Continental configuration controls ocean oxygenation during the Phanerozoic” by Alexandre Pohl, Andy Ridgwell, Richard G. Stockey, Christophe Thomazo, Andrew Keane, Emmanuelle Vennin and Christopher R. Scotese, 17 August 2022, Nature.
DOI: 10.1038/s41586-022-05018-z

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  • If you've spent years obtaining finance for your project and then doing the work, there must be a strong bias towards discovering 'surprising' game changing results? It's understandable they want to gain more funding, but should continental drift really be considered as an important contributer to deep sea current weakening over the next few decades?

  • Of course it always comes down to Global Warming. Scientists have sold their reputations when their research is beholding to politics. The fact that the earth has been warming up since the mini ice age is lost on them.

  • The writer is sure to author remarks of assumptions in the content of the article; Why? Lack of imperial data for factual conclusion. Most of this so called truth is based in men/women with years of assumptual education without solid conclusion circlular reasoning based on bits of imperial data and older educational men/women with years of assumptual education whom have written books.
    I am shocked that LIFTABLEtv would carry this hyperbole!

  • The headline along with the image was a little misleading, but the actual article was fascinating, and I'm glad i read it. More people should be aware of this. Cool your jets, George!

  • It's such a disappointment to see how man has destroyed our planet. If we don't step up to the plate and take control of our environment we are doomed.

  • George please havd a little more self respect. It can be hard to be confident in a world where a lack of understanding of science and concepts that require a level of education one doesnt posess for sure. But theres no need to be so hard on oneself. You are so much more than disgusting clickbait. Maybe just try to stick with easier topics and appropriate wedsites like sesame street or truth social where youll likely find more of a shared hive mind mentality that makes you feel safe and secure.

  • Ok, I might be wrong but doesn't fish breath water? I mean the suffocate when brought out of the water because they can't process the air, so .......

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University of California - Riverside

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