Scientists at the University of California, Irvine have discovered that seawater’s deep circulation in the Atlantic and Southern Oceans is slowing due to climate warming. If this continues, the ocean’s ability to remove carbon dioxide from the atmosphere will be severely limited and the effects of global warming will be exacerbated.
A recent study published by these researchers Nature Climate Changeshowed that the Atlantic Meridional Tipping Circulation and the South Meridional Tipping Circulation could slow down by up to 42% by 2100. Worst-case scenario simulations even suggest that the SMOC could end completely by 2300.
“Analysis of forecasts from 36 Earth system models under different climate scenarios shows that uncontrolled global warming could lead to the cessation of deep ocean circulation,” said co-author J. Keith Moore, professor in UCI’s Department of Earth Sciences. “There will be a climate catastrophe on a similar scale to the complete melting of land ice sheets.”
The importance of disrupting circulation
In the Atlantic, warm surface water cools and evaporates as it flows north, making it saltier and denser. This heavier water sinks into the deep ocean and heads south, eventually rising, carrying nutrients from the depths that are the food base of marine ecosystems.
In addition, the circulation of the ocean covering the earth creates a powerful factory for processing atmospheric carbon dioxide. A major physical and chemical interaction between seawater and air—what Moore and colleagues call the “solubility pump”—pulls CO2 into the ocean. The ocean circulation sends some of the carbon back to the sky, while the net amount is absorbed in the ocean depths.
In addition, a “biological pump” occurs because phytoplankton use CO2 during photosynthesis and the formation of carbonate shells. When plankton and larger animals die, they sink, slowly decomposing and releasing carbon and nutrients deep down. Some rotate upwards with circulation and elevation, but some remain accumulated under the waves.
“Disturbed circulation will reduce the ocean’s absorption of carbon dioxide from the atmosphere, intensifying and prolonging warm climate conditions,” Moore said. “Over time, nutrients that support marine ecosystems will increasingly enter the deep ocean, reducing the biological productivity of the global ocean.”
According to Moore, humans depend on the solubility pump and the biological pump to help remove some of the CO2 released into the air through fossil fuel burning, land use practices and other activities.
“Our analysis also shows that reducing greenhouse gas emissions now can prevent the deep circulation from shutting down completely in the future,” he said. Source
Source: Port Altele
