The Atlantic Meridional Overturning Circulation (AMOC) is a large system of ocean currents in the Atlantic Ocean, transporting warm surface waters from the tropics northward and returning cold deep waters southward. The AMOC is part of a worldwide network of ocean currents driven by changes in salinity and temperature, a process called thermohaline circulation.
As warm surface waters travel northward, they cool and become denser and more saline. They eventually sink to the deep ocean and return southward as cold deep waters, completing the overturning cycle. This cycle can take 1,000 years.
The AMOC plays a central role in regulating Earth’s climate, particularly in the northern hemisphere. As warm surface waters travel north, they release heat into the atmosphere, keeping European winters milder than they would otherwise be. The Atlantic is the only ocean with a net northward heat transport.
As surface waters lose heat, become denser and sink, a process called deepwater formation, carrying large amounts of carbon from the atmosphere into the deep ocean. This makes the AMOC the main carbon sink in the northern hemisphere. Because the AMOC forms a large component of the global ocean circulation system, changes in the AMOC can affect climate patterns worldwide.
Understanding the AMOC is challenging because of its complexity and scale. Oceanographers have observed it continuously since 2004, and new-generation climate models are improving our understanding of its dynamics. Even so, fundamental questions remain: what drives the AMOC, and what makes it change over time? EPOC is working to answer them.
Scientists expects the strength of the AMOC to decline because of anthropogenic climate change, though the extent and timing of any decline remain highly uncertain. An increase in freshwater input from melting ice sheets and glaciers can alter density and temperature differences in the North Atlantic, potentially disrupting the sinking process and weakening the AMOC.
Weakened circulation means less heat transport northwards. This could cool the North Atlantic region by several degrees and make European climates significantly colder, with knock-on effects for regional and global weather patterns. Towards the end of the last glacial period, around 14,500 years ago, an AMOC shutdown may have triggered a series of abrupt temperature shifts. It is extremely unlikely that something similar would happen during the 21st century. Read more about AMOC shutdown risk.
As the climate changes, monitoring and understanding AMOC behaviour becomes more important. Better observations and models help us prepare for potential impacts and design a more effective observing system for the future.
Last updated: April 2026 | written by María Jesús Rapanague, post-graduate researcher in AMOC connectivity modelling, Max Planck Institute for Meteorology, Germany
Reference: Meredith, M. (2022) Carbon storage shifts around Antarctica. Nature Communications 13. DOI: 10.1038/s41467-022-31152-3