The position of the continents helps fill the oceans with oxygen. Most deep ocean creatures would be killed by continental movement.
"Continental drift seems so slow, like nothing drastic could come from it, but when the ocean is primed, even a seemingly tiny event couldtrigger the widespread death of marine life," said Andy Ridgwell, a co-author of the study.
As the ocean gets closer to the north or south pole, the water becomes denser and colder. Oxygen is transported down to the ocean floor when the water sinks.
When a return flow brings sunken organic matter back to the ocean, it fuels the growth of plankton. An incredible diversity of fish and other animals can be found in the ocean thanks to the continuous supply of oxygen and organic matter.
The circulation of oxygen and nutrients can end abruptly according to new findings. The researchers looked at whether the locations of continental plates affected how the ocean moves oxygen. They were surprised that it does.
The finding is detailed in the journal.
After animal life in the ocean got started, the entire global ocean circulation seemed to periodically shut down. We weren't expecting to find that the movement of the continents could affect the way life evolved on Earth.
Modelling the evolution of marine oxygen over the last 540 million years was relatively simple and did not account for ocean circulation. There was a drop in atmospheric oxygen concentrations when the ocean anoxia occurred.
The first author of the study is a paleoclimate modeler at Université Bourgogne Franche-Comté in France.
The ocean was represented in three dimensions and ocean currents were accounted for for the first time in this study. Collapse in global water circulation leads to a separation of oxygen levels in the upper and lower depths, according to results.
For tens of millions of years, the entire seafloor, except for shallow places close to the coast, lost oxygen when it was separated.
It 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. There are strange-looking fish, giant worms and crustaceans, squid, sponges and more in the deepest part of the ocean.
The paper doesn't address if or when Earth might expect a similar event in the future, and it's hard to know when a collapse might occur. Climate models show that global warming will weaken ocean circulation, and some models show that the branch of circulation in the North Atlantic will eventually collapse.
A higher resolution climate model is needed to predict mass extinction events. There is evidence that the flow of water to depth is declining in the North Atlantic.
Ridgwell believed that a warm summer or the erosion of a cliff could cause a cascade of events that could end life.
The surface of the ocean is where all the action is. The ocean is providing vital oxygen to animals in darkness.
Life can flourish in the ocean, but it can be taken away again. As continental plates continue to move, anything is possible.
More information: Alexandre Pohl, Continental configuration controls ocean oxygenation during the Phanerozoic, Nature (2022). DOI: 10.1038/s41586-022-05018-z. www.nature.com/articles/s41586-022-05018-z Journal information: Nature
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