Nature of SPG–AMOC interaction and relative importance of convection regions

Determine the exact nature of the dynamical interaction between the North Atlantic subpolar gyre and the Atlantic Meridional Overturning Circulation (AMOC), and ascertain the comparative relevance of the Labrador Sea versus the Irminger Sea and Nordic Seas in contributing convection to the overturning circulation.

Background

The paper investigates whether a proposed mechanism for bistability of the North Atlantic subpolar gyre is represented in CMIP6 models using causal inference. While several internal feedbacks within the gyre are identified, the broader interaction between the subpolar gyre and the Atlantic Meridional Overturning Circulation (AMOC) is not analyzed directly and remains uncertain.

The authors highlight contrasting evidence: observational data indicates that much of the AMOC-related transport occurs in the eastern subpolar Atlantic, whereas the deepest convection is observed in the Labrador Sea. This motivates the need to clarify both the mechanistic link between the subpolar gyre and AMOC and the relative importance of different convection regions (Labrador, Irminger, Nordic seas) for the overturning circulation.

References

The exact nature of this interaction and the relevance of the Labrador sea compared to other convection regions such as the Irminger or Nordic seas are still open questions.

— Causal Mechanisms of Subpolar Gyre Variability in CMIP6 Models  (2408.16541 - Falkena et al., 2024) in Conclusion and Discussion

One of the open questions is how an SPG collapse would influence the AMOC; it has been shown in simulations that an SPG collapse under future warming may not necessarily imply a concurrent collapse of the AMOC.

— Disentangled Fingerprints suggest no historical weakening of Atlantic Overturning and Subpolar Gyre  (2609.18551 - Emirzade et al., 16 Sep 2026) in Introduction, paragraph beginning “The coexistence of positive and negative feedback mechanisms”

However, there is currently no consensus on the precise nature of the SPG-AMOC relationship, nor on how this coupling may evolve under anthropogenic climate change.

— Disentangled Fingerprints suggest no historical weakening of Atlantic Overturning and Subpolar Gyre  (2609.18551 - Emirzade et al., 16 Sep 2026) in Introduction, paragraph beginning “The SPG, nevertheless, influences the AMOC”