Climate change could cause 'disaster' in the world's oceans, say scientists

The ocean's ability to remove carbon dioxide from the atmosphere will be severely limited if climate-driven heating of seawater continues.

In a recent study published in Nature Climate Change, researchers analyzed projections from three dozen climate models and found that the Atlantic and Southern circulations will slow by as much as 42% by the year 2200. Simulations suggest that the SMOC could cease by 2300.

The analysis shows that a shutdown of the ocean deep circulation could be caused by global warming. It would be a climate disaster like the melting of the ice sheets on land.

It's important to overturn circulation.

Warm water in the Atlantic makes it saltier and denser. The heavier water sinks into the deep ocean and proceeds to the south where it eventually rises back up.

There is a powerful factory for the processing of atmospheric carbon dioxide in the ocean. Moore and his colleagues call it a "solubility pump", because it draws CO 2 into the ocean. The net amount of carbon is sequestered in the ocean's depths.

There is a biological pump that occurs when CO 2 is used in forming carbonate shells. The plankton and larger animals sink when they die. A portion of the body of water remains banked beneath the waves.

Moore said that a disruption in circulation would affect the ocean's absorption of carbon dioxide. The decline in global-ocean biological productivity would be caused by the trapping of the nutrients in the deep ocean.

Humans rely on the biological pump and the solubility pump to remove some of the CO 2 from the air through fossil fuel burning, land use practices and other activities.

Reducing greenhouse gas emissions can prevent the complete shutdown of the deep circulation in the future.

Moore was joined on the project by Yi Liu, a student in Earth system science at the University of California, Irvine; Francois Primeau, a professor and chair of the Department of Earth System Science at the University of California, Irvine; and a professor of ocean and Earth sciences at the University The study relied heavily on simulations developed by the CMIP6 project.

There is more information on Nature Climate Change. There is a DOI called 10.1038/s415522-01555-7.

Journal information: Nature Climate Change