Disruptions to the Atlantic meridional overturning circulation (Amoc) will impact ocean currents, increase sea level rise, and bring freezing temperatures to Europe.
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The circulation of the Atlantic Ocean, a key component in global climate regulation, is “on route” to a tipping point, according to a new study, which describes the findings as “bad news for the climate system and humanity.”
Using computer models and existing data, the researchers developed an early warning indicator for the breakdown of the Atlantic meridional overturning circulation (Amoc), a large circulation of ocean currents transporting warm water from the tropics into the North Atlantic Ocean. The system is part of a global pattern called thermohaline circulation, or what scientists refer to as the “great ocean conveyor belt,” a constantly moving system of deep-ocean water driven by differences in temperature and salinity.
This natural process of global ocean current circulation helps ensure the Earth’s oceans remain continually mixed and that heat and energy are evenly distributed, which, in turn, directly affect the climate humans live in today.
According to the new study, published last week in ScienceAdvances, the increase in freshwater inflows in the Atlantic Ocean from rapidly melting ice sheets and swelling rivers from global warming are pushing the system to the brink, with potentially catastrophic repercussions on global climate. Indeed, without this constant flow of current circulation, regional temperatures would become more extreme – intense heat near the equator and freezing in the poles – making less land on Earth habitable.
In particular, a disruption in the Amoc would result in an increase in extreme weather conditions in Europe, North America, and North Africa such as heatwaves, drought, intense winter storms, and severe flooding. In particular, Western Europe would see substantially less precipitation and temperatures there could drop to pre-industrial levels, while other parts of the planet, especially the tropics and the southern hemisphere, would warm faster, since the current would no longer be able to transport the increasing ocean warmth northward.
A weaker circulation could also lead to rising sea levels, which would affect the East Coast of the US in particular, and would decrease the ocean’s effectiveness in absorbing atmospheric carbon dioxide (CO2), leading to a higher amount of greenhouse gases in the atmosphere.
“This leads to a lot of dynamic sea level rise, up to a meter in the North Atlantic under an Amoc collapse,” said René van Westen, co-author of the research. “And you need to add that on top of the sea level rise already caused by global warming. So the problems are really severe.”
A study last year had already warned that under the current emissions scenario, Amoc could collapse around mid-century, challenging the findings of the latest Intergovernmental Panel on Climate Change’s (IPCC) assessment, which suggested a collapse of Amoc in the 21st century to be very unlikely. According to 2021 research, the current is already at its weakest in over 1,600 years.
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