Reality of an AMOC boundary crisis in the Earth system

Ascertain whether a boundary crisis of the Atlantic Meridional Overturning Circulation—specifically, a collision of the vigorous AMOC attractor with an edge state leading to the emergence of a ghost state—occurs in the real climate system at plausible atmospheric CO2 levels.

Background

In PlaSim-LSG, the authors identify a boundary crisis at CO2 levels projected for the coming decades, wherein the ON (vigorous) AMOC attractor merges with an edge state, producing long-lived chaotic transients (a ghost state) and ensemble splitting under forcing. This mechanism provides a dynamical-systems explanation for divergent AMOC behavior observed in other models.

However, extrapolating this crisis mechanism to the real Earth system remains unresolved and is crucial for assessing AMOC tipping risks and predictability under ongoing anthropogenic forcing.