Ice age volcanoes linked to ancient Atlantic current shutdowns

by Robert Schreiber
Berlin, Germany (SPX) Feb 24, 2026
A new study from the Niels Bohr Institute at the University of Copenhagen reports that extreme volcanic eruptions during the last ice age were capable of disrupting the Atlantic Meridional Overturning Circulation, AMOC, and triggering abrupt and long lasting climate shifts. The AMOC transports warm water from the southern hemisphere into the North Atlantic and underpins the relatively mild climate of Northern Europe and countries such as Denmark.

Scientists regard the AMOC as a key element of the global climate system because its collapse could replace Northern Europe's temperate conditions with a much colder regime similar to that of Alaska, including winter temperatures that can fall to around minus 35 degrees. Today, global warming and increased meltwater from the Arctic are already stressing this circulation pattern, but there is still disagreement over how close the AMOC is to a critical threshold and how fast a collapse could unfold.

In the new work, an international team led from Copenhagen combined information from ice cores with hundreds of climate model simulations to investigate how very large volcanic eruptions affect the AMOC under glacial conditions. They find that eruptions of sufficient magnitude, especially those occurring near the equator, can push the circulation into a weakened or even fully collapsed state once the system is already close to instability.

Large explosive eruptions inject sulphur and dust high into the atmosphere and stratosphere, where these particles block incoming solar radiation and cool the planet's surface. According to the researchers, this cooling sets off a chain of processes that includes expanded sea ice cover and changes in the salinity structure of the ocean. Together, these changes can effectively switch off the overturning "pump" that keeps the AMOC running.

The last ice age lasted about 100,000 years and ended more than 10,000 years ago, yet climate records from that period show a series of rapid transitions between cold and warmer phases known as Dansgaard Oeschger events. The physical drivers of these abrupt shifts have been debated for decades. The new study suggests that very large volcanic eruptions may have provided the critical perturbation that tipped the ocean circulation and climate into a different state for centuries to millennia when conditions were already near a tipping point.

Co author Markus Jochum describes the effect using the analogy of a balance board, noting that if the climate system is already close to a critical threshold, only a relatively small additional push is required to make it tip. In this framework, a major volcanic eruption can act as that push, with the models indicating that such events have historically been able to collapse the Atlantic circulation and reshape climate patterns over very long timescales.

Lead author Guido Vettoretti emphasizes that the findings highlight how sensitive the AMOC can be to external disturbances under certain background conditions. By clarifying how past eruptions altered ocean circulation and climate, the study adds a new dimension to the assessment of how the AMOC might respond to strong perturbations in the future, including those associated with ongoing global warming and ice melt.

Research Report:Volcanism-induced collapse and recovery of the Atlantic meridional overturning circulation under glacial conditions