Warming is collapsing the deep ocean circulation

Jan. 5 () –

Climate-induced warming of seawater is causing a slowdown in deep circulation patterns in the Atlantic and Southern Oceans.

According to Earth system scientists at the University of California at Irvine, if this process continues, the ocean’s ability to remove carbon dioxide from the atmosphere will be severely limitedwhich will further aggravate global warming.

In a recent study published in Nature Climate Changethese researchers analyzed projections from three dozen climate models and found that the Atlantic Oscillation Meridional Circulation and the Southern Oscillation Meridional Circulation they will slow down by up to 42% between now and 2100. Simulations suggest that, in the worst case, GCOS could be completely gone by 2300.

“Analysis of projections from 36 Earth system models across a range of climate scenarios shows that runaway global warming could disrupt deep ocean circulation,” he says. it’s a statement J. Keith Moore, study co-author and UCI Professor of Earth System Sciences. “This would mean a climate disaster of a magnitude similar to the complete melting of the ice sheets on land.”

In the Atlantic, as warm water flows north at the surface, it cools and evaporates, making it saltier and denser. This heavier water sinks into the ocean depths and heads south, where it ends up rising, carrying nutrients from the depths. that constitute the nutritional base of marine ecosystems.

In addition, the ocean circulation that spans the entire planet creates a powerful factory for processing atmospheric carbon dioxide. The basic physical and chemical interaction of seawater and air—what Moore and his colleagues call a “solubility pump”—carries CO2 out into the ocean. Although ocean circulation returns some of the carbon to the sky, the net amount is sequestered in the depths of the ocean.

In addition, a “biological pump” is produced when phytoplankton use CO2 during photosynthesis and in the formation of carbonate shells. When plankton and larger animals die, they sink, slowly breaking down and releasing carbon and nutrients into the depths. A part returns to the surface with the circulation and upwelling, but another remains stored under the waves.

“A disruption to the circulation would reduce the ocean’s uptake of carbon dioxide from the atmosphere, thereby intensifying and prolonging warm weather conditions,” Moore explains. “Over time, the nutrients that support marine ecosystems would become increasingly trapped in the ocean depths, which would cause a decrease in the biological productivity of the global ocean”.

Humans rely on the solubility pump and the biological pump to help remove some of the CO2 emitted into the air through the burning of fossil fuels, land use practices and other activitiesaccording to Moore.

“Our analysis also shows that reducing greenhouse gas emissions now may prevent complete closure of the deep circulation in the future,” he said.