A new international study shows that large volcanic eruptions in the tropics could disrupt major ocean currents during the last ice age, triggering abrupt, strong, and long-lasting changes in the climate.
During the last ice age, the climate in the northern hemisphere experienced repeated, drastic swings between rapid warming and slow cooling periods. These jumps, known as Dansgaard–Oeschger events, brought temperature increases of up to 15 °C in Greenland within a few decades. Researchers have long suspected that shifts in ocean circulation played a major role, but what could push the system so suddenly?
Volcanic shocks to a sensitive ocean circulation system
A recent study points to an unexpected driver: volcanic eruptions in the tropics. The team behind the study, including Stephen Outten from the Nansen Center, used an advanced climate model and incorporated realistic records of strong volcanic eruptions preserved in ice cores. This way, they were able to test how volcanism may have interacted with the climate system in the period between 115,000 and 11,700 years ago, during the last ice age.
The results show that very large eruptions during the ice age could disrupt ocean currents, and entire systems of currents, such as the Atlantic Meridional Overturning Circulation (AMOC). This is a measure for the transport of warm, salty water in the upper layers northward through the Atlantic Ocean, where it cools, sinks (“overturns”), and returns southward at depth. It is a key part of the global ocean circulation and an important regulator of global climate.
When strong eruptions injected vast amounts of particles into the atmosphere, the temporary cooling that followed likely weakened the AMOC. These disruptions changed how heat and salt moved through the Atlantic, likely creating the right conditions for Dansgaard–Oeschger events to unfold.
A climate system pushed past its tipping point
The study suggests that strong volcanic eruptions during the last ice age could have caused shifts in the AMOC and triggered abrupt warming periods. In that sense, volcanic activity acted as a catalyst: a short‑lived atmospheric disturbance that set off long‑lasting changes in ocean circulation and climate.
Why these ancient events matter today
Although today’s world is very different from the ice age, the overall lesson is relevant: abrupt shifts can occur when the AMOC weakens, under the right conditions. Understanding how past disruptions unfolded helps researchers assess how close we may be to crossing a tipping point in the future.
Key researcher: Stephen Outten
