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AMOC stability landscape and edge/ghost states in the NASA GISS model

Characterize the Atlantic Meridional Overturning Circulation stability landscape in the NASA GISS-E2-1-G climate model as a function of atmospheric CO2, and determine the existence and properties of AMOC edge states and post-crisis ghost states that could explain the reported ensemble bifurcation under SSP2-4.5 forcing.

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Background

The authors compare PlaSim-LSG trajectories with those from the NASA GISS-E2-1-G model, which exhibits an ensemble splitting of AMOC behavior under SSP2-4.5. They hypothesize that the phase-space region of ensemble divergence aligns with the edge/ghost state region found in PlaSim-LSG.

Due to model complexity, the detailed AMOC stability landscape and the presence of edge or ghost states in GISS are not yet established, limiting mechanistic interpretation of the observed bifurcation and its relation to boundary crises.

References

Due to the complexity of the GISS model, its AMOC stability landscape with respect to CO$_2$ and the properties of potential edge states or ghost states are not known.

— Boundary crisis and long transients of the Atlantic overturning circulation mediated by an edge state (2504.20002 - Börner et al., 28 Apr 2025) in Section 6.2 (Stochastic bifurcation in the GISS model)