Destabilization of glacial climate by the radiative impact of Atlantic Meridional Overturning Circulation disruptions

During each of the dramatic global warmings that ended the Pleistocene ice ages, the Atlantic Meridional Overturning Circulation (AMOC) was disrupted. It is not clear whether this was a contributing cause or simply an effect of deglaciation. Here we show that in an ensemble of simulations with a global climate model, AMOC disruption causes a consistent and sustained positive radiative imbalance of ~0.4 W m−2. The imbalance is accommodated by heat accumulation in the ocean interior, representing an overall planetary warming, subsequently released by deep convection in the North Atlantic when the AMOC resumes. The results suggest a means by which AMOC disruptions could have helped to tip the planet out of stable glaciated states. However, the fact that AMOC disruptions occurred during prior Heinrich Stadials without causing deglaciation shows that other factors, such as ice sheet dynamics, or controls on CO2, were also key for deglaciation. Key Points Bipolar seesaw is not a zero‐sum transfer of heat between hemispheres but causes a radiative imbalance of ~0.4 W m‐2 During AMOC disruptions, the energy imbalance accumulates in the middepth Atlantic, and is released during resumption Energetic impact of AMOC disruptions may have contributed to Quaternary climate instability