Cascading tipping behavior of the interacting Greenland Ice Sheet and Atlantic Meridional Overturning Circulation in a model of low complexity

The Greenland Ice Sheet (GIS) and the Atlantic Meridional Overturning Circulation (AMOC) have been identified as possible tipping elements of the climate system, transitioning into a qualitatively different state with the crossing of a critical driver threshold. They interact via freshwater fluxes into the North Atlantic originating from a melting GIS on the one hand, and via a relative cooling around Greenland with a slowdown of the AMOC on the other. This positive-negative feedback loop raises the question how these effects will influence the overall stability of the coupled system. Here, we qualitatively explore the dynamics and in particular the emergence of cascading tipping behavior of the interacting GIS and AMOC by using process-based but still conceptual models of the individual tipping elements with a simple coupling under idealized forcing scenarios.

We identify patterns of multiple tipping such as (i) overshoot cascades, developing with a temporary threshold overshoot, and (ii) rate-induced cascades, arising under very rapid changes of tipping element drivers. Their occurrence within distinct corridors of dangerous tipping pathways is affected by the melting patterns of the GIS and thus eventually by the imposed external forcing and its time scales.

The conceptual nature of the proposed model does not allow for quantitative statements or projections on the emergence of tipping cascades in the climate system. Rather, our results stress that it is not only necessary to stay below a certain critical threshold to hinder tipping cascades but also to respect safe rates of environmental change to mitigate domino effects and in turn to maintain the resilience of the Earth system.