A newly published peer-reviewed study in the Journal of Geophysical Research: Oceans indicates that the Atlantic Meridional Overturning Circulation (AMOC)—a crucial system of ocean currents that helps regulate heat and weather patterns globally—could start collapsing as early as 2055. This alarming finding highlights the fragility of a vital component of our climate system.
The AMOC operates like a massive conveyor belt, transporting warm water northward along the ocean’s surface while sending cold, dense water southward along the ocean floor. This circulation is essential for maintaining the climate of the Northern Hemisphere, significantly influencing weather patterns in regions such as Western Europe, the African and Asian monsoons, and sea level patterns along the U.S. East Coast.
However, new simulations suggest that the stability of the AMOC may be more vulnerable than previously thought. The latest climate models indicate that even under a moderate emissions scenario—where global temperatures rise by approximately 4.8°F (2.7°C) above pre-industrial levels—the AMOC could face collapse by 2063. In more severe emission scenarios, this breakdown could commence as early as 2055.
“The chance of tipping is much larger than previously thought,” stated Sybren Drijfhout, a professor of physical oceanography at the University of Southampton and Utrecht University. This marks a significant shift from earlier estimates, which suggested that such an event might not occur until the late 22nd century.
The risk of an AMOC collapse is not merely theoretical. Recent observations reveal that deep water formation—the driving force behind the AMOC—is weakening, primarily due to melting Arctic ice and rising air temperatures. As the cold, salty water at the surface warms and becomes less dense due to freshwater dilution, it loses its ability to sink, leading to potential destabilization of the entire current system.
Tracking the AMOC’s strength in real-time has historically been challenging for scientists, as traditional metrics like sea surface temperature can be unreliable in rapidly changing climate conditions. In response, researchers have developed a new and more accurate indicator known as surface buoyancy flux. This parameter combines heat and salinity changes at the ocean's surface to estimate shifts in water density, which is crucial for deep water formation.
“The advantage of the surface buoyancy flux is that it can be calculated in many climate models,” explained René van Westen, postdoctoral researcher in climate physics at Utrecht University and lead author of the study. “We aimed to develop a new indicator that also works under climate change conditions.”
The findings are concerning. According to van Westen, the surface buoyancy flux remained stable until 2020, indicating little recent change in the AMOC. However, since then, the signal has been rising, suggesting that the current is weakening more rapidly than anticipated. When this indicator drops to zero, it signifies that no dense water is sinking, marking the onset of a functional collapse.
The potential collapse of the AMOC would have widespread and severe consequences. Europe could experience colder, stormier winters and decreased rainfall, which may lead to a reduction in agricultural output by as much as 30%. Meanwhile, cities along the U.S. East Coast could face a significant increase in sea levels due to shifts in water distribution.
Furthermore, regions like the Amazon rainforest, the African Sahel, and the South and East Asian monsoons could face major disruptions, impacting food security, migration patterns, and economic stability. Unlike sudden weather events, an AMOC collapse would unfold over decades, but its long-term effects could be profound.
While the study estimates it may take over 100 years for full disruption, some experts, including Drijfhout, argue that significant changes could occur within just 50 years—a blink in geological time. “The AMOC is like a campfire with a dwindling amount of fuel,” he said. “If we stop throwing new wooden blocks on the fire, the fire does not immediately die, but it keeps smoldering for some time.”
Despite the grim projections, researchers believe that there is still a narrow window of opportunity to avert disaster. They emphasize that a sharp reduction in carbon emissions could significantly alter the trajectory of the AMOC. “An AMOC collapse scenario can possibly be prevented when following a low emission scenario,” van Westen stated, “but this would require achieving net-zero carbon emissions around 2050.”
In conclusion, the future of the Atlantic Meridional Overturning Circulation is uncertain, and immediate action is crucial to mitigate its impending collapse. The implications of inaction could be catastrophic, underscoring the urgent need for global cooperation in tackling climate change.
