Three climate models in a Nature Geoscience study recast the Atlantic Meridional Overturning Circulation as an “ocean heat valve,” not just a conveyor moving heat between hemispheres.
When AMOC was strong, North Atlantic deep convection vented large amounts of ocean heat to the atmosphere and space; when it weakened, that heat loss shut down and more energy accumulated in the ocean.
The framework also offers a new explanation for abrupt Dansgaard-Oeschger ice-age swings, linking Greenland’s rapid changes and Antarctica’s slower shifts to different parts of a global ocean-heat cycle.
Applied to today’s climate, the researchers say further AMOC weakening could throttle that valve and increase planetary heat storage, potentially amplifying warming.
The team cautioned the ice-age mechanism depended on extensive sea ice absent in a warmer future, making it a guide to risk rather than a direct forecast of collapse.