Atlantic Meridional Overturning Circulation (AMOC)
Collapse of critical Atlantic current is no longer low-likelihood, study finds
Context: Recent studies warn that the Atlantic Meridional Overturning Circulation (AMOC) may be closer to a tipping point than previously believed. New model runs suggest collapse could become inevitable within the next few decades, even under low-emission scenarios, highlighting the urgency of cutting fossil fuel emissions.
What is an AMOC?
- AMOC stands for Atlantic Meridional Overturning Circulation. It’s a massive system of ocean currents that acts like a conveyor belt, moving warm, salty water from the tropics northward to the North Atlantic. There, the water cools, becomes denser, sinks, and flows back southward at deeper levels.
- This cycle is driven by differences in water temperature and salinity—a process called thermohaline circulation. It’s slow but powerful, taking about 1,000 years for a parcel of water to complete the full loop.
What is the significance of AMOC?
AMOC plays a critical role in regulating global climate and ocean health:
- Climate Stabilisation: Keeps Western Europe warmer than other regions at similar latitudes (e.g., Canada). Influences monsoon systems in South Asia, West Africa, and the Amazon.
- Ecosystem Support: Circulates nutrients and oxygen, supporting marine biodiversity and fisheries.
- Carbon Sink Function: Absorbs and stores atmospheric CO₂, helping mitigate global warming.
- Weather Patterns: Affects rainfall distribution, hurricane activity, and sea ice formation.
Without AMOC, many regions would experience extreme climate shifts, including colder winters in Europe, rising sea levels along the U.S. East Coast, and droughts in the Sahel and South Asia.
How does climate change influence AMOC?
Climate change is weakening AMOC, and could eventually cause its collapse:
- Melting Ice & Freshwater Influx: Greenland’s melting ice adds freshwater to the North Atlantic, reducing salinity and density. This disrupts the sinking of cold water, a key driver of AMOC.
- Ocean Warming: Warmer surface waters are less dense, making it harder for them to sink and complete the circulation loop.
- Increased Rainfall: More precipitation dilutes ocean salinity, further weakening the thermohaline engine.
- Model Predictions: Studies show AMOC is at its weakest in over 1,600 years. Under current emissions trajectories, there’s a 25–70% chance of collapse by 2100, depending on the scenario.
A collapse would trigger irreversible climate shifts, including: Severe cooling in Europe, Disruption of tropical rain belts, Accelerated sea level rise, and Altered marine ecosystems.
