Three types of tipping dynamics in ice sheets

The polar ice sheets in both Antarctica and Greenland are considered tipping elements in the Earth system. However, the detailed nature of the underlying feedback mechanisms, hysteresis and irreversibility of ice loss on different temporal and spatial scales is an active research frontier.

Tipping dynamics can be triggered by forcing a system beyond a critical threshold (bifurcation-induced tipping), for instance through an increase in global warming beyond some critical level. Alternatively, tipping can also be initiated through fluctuations close to a critical threshold (noise-induced tipping), or by changing the forcing faster than a critical rate (rate-dependent tipping). These mechanisms have been described in complex systems theory and shown in conceptual modelling approaches, but a systematic insight into such dynamics in process-based models for Earth system components is lacking so far.

Here we explore these different types of tipping dynamics for the polar ice sheets based on simulations with the Parallel Ice Sheet Model, disentangling the complexity of critical transitions in response to anthropogenic climate change at different temporal and spatial scales. Our results underscore the importance of the rate of global warming, its variability, as well as the magnitude and duration of potential overshoots – all of which are decisive for the future evolution and long-term stability of the ice sheets.