A new research published in the journal Nature suggests that while the Atlantic Meridional Overturning Circulation (AMOC) is expected to weaken this century due to climate change, a full collapse is unlikely.
The study, led by Dr. Jonathan Baker of the Met Office, simulated the development of the AMOC under extreme conditions, including a quadrupling of atmospheric CO₂ levels and a massive influx of meltwater. The researchers used 34 climate simulation models to calculate interactions between the atmosphere, cryosphere, and oceans, considering the Southern and Indian Oceans.
"Our modelling study suggests that the AMOC will resist pressures from rising global temperatures and inputs of freshwater into the North Atlantic, with the weakened system being largely driven by winds over the Southern Ocean," said Baker.
The main reason for the AMOC's resilience is persistent upwelling in the Southern Ocean, driven by strong westerly winds, which compensates for AMOC weakening. The mechanism prevents a total collapse of the AMOC this century, even under the most extreme climate scenarios, the study found.
However, scientists warn that even without a complete collapse, a weaker AMOC could have impacts on the global climate, including disruption to weather patterns, rising sea levels on North Atlantic coastlines, and effects on ocean ecosystems. According to New Scientist, weakening of the AMOC would change global rainfall patterns, impacting crop yields around the world, and in regions like the Mediterranean, there could be alterations in rainfall regimes, leading to more arid conditions and increased droughts.
According to The Independent, concerns about the stability of the AMOC have grown, with recent studies warning that it might be approaching a tipping point that could prompt catastrophic climate shifts. Some studies suggest that the advance of the climate crisis could lead to an imminent collapse, triggering extreme weather events.
"The new study does not contradict earlier modeling studies about future AMOC changes and their climatic impacts, nor does it claim this," said Dr. Stefan Rahmstorf, a climate researcher from the Potsdam Institute for Climate Impact Research (PIK), according to ORF Science.
Experts highlight that even a weakening of the AMOC, without a complete collapse, could have severe consequences. "It doesn't change our expectation that the AMOC will weaken over the 21st century, and that this weakening will have important impacts on climate," said Professor Andrew Watson from the University of Exeter.
According to Deutsche Welle, the Intergovernmental Panel on Climate Change (IPCC) considers a strong weakening of the AMOC in the 21st century to be very likely due to global warming. The IPCC assessment states with medium confidence that the AMOC will not collapse abruptly this century, undermining doomsday predictions of an imminent catastrophic collapse.
Warming temperatures and an influx of cold water from melting Arctic ice are weakening the AMOC, which has already slowed by about 15 percent since the mid-20th century. The ocean conveyor belt system transports rising warm water north and sinking cool water south and is a key factor in global weather systems.
"The study's results should certainly not be interpreted as showing that AMOC is a resilient system, given it finds that the AMOC still reduces to very weak strengths under human-caused global warming," said Dr. René van Westen, postdoctoral researcher at the Royal Netherlands Meteorological Institute, according to The Independent.
"The study also found that as the AMOC weakens, a weak Pacific Meridional Overturning Circulation (PMOC) may develop to compensate somewhat, although it is not strong enough to completely replace the AMOC's role," explained Baker. "However, this is not strong enough to balance all of the Southern Ocean wind-driven upwelling. Therefore, some level of sinking in the North Atlantic must be maintained, preventing a complete collapse of the AMOC," he added.
The article was written with the assistance of a news analysis system.