A new mechanism for synchronising Heinrich events with Dansgaard-Oeschger cycles

The northern hemisphere climate during the last glacial period (about 65,000-15,000 years before present) was dominated by two prominent signals of glacial climate variability, known as Dansgaard-Oeschger cycles and Heinrich events. The episodic Heinrich events, defined by an enhanced ice discharge from the Laurentide Ice Sheet, tend to coincide with cold phases of the Dansgaard-Oeschger cycles, which are periodic and abrupt warming and cooling cycles. This suggests a close connection, but the exact mechanisms have remained enigmatic to this day. In their recent study, Clemens Schannwell, Uwe Mikolajewicz, Marie-Luise Kapsch and Florian Ziemen introduce a new mechanism that explains how Heinrich events are synchronised with Dansgaard-Oeschger cycles.

Using simulations with a coupled ice sheet-solid earth model that are forced with a synthetic Dansgaard-Oescher cycle, Schannwell et al. present a Heinrich event mechanism that overcomes previous shortcomings and reproduces all main characteristics of Heinrich events from the paleo record under a wide range of forcing scenarios. In their mechanism, internal ice-sheet instabilities are the underlying cause for triggering Heinrich events. The timing of these events, however, can be locked into the cooling phase of the Dansgaard-Oeschger cycle through an atmospheric perturbation (e.g., snowfall and surface temperature) that is induced by the Dansgaard-Oeschger cycle itself.  The atmospheric mechanism permits a pan-ice sheet response and allows for the occurrence of synchronous Heinrich events from two ice streams of the Laurentide Ice Sheet – a characteristic from the paleo-record that previous theories revolving around the ocean as the key driver have so far failed to explain.

A distinct advantage of the atmosphere-driven mechanism is that it is applicable to both ice streams terminating in the ocean as well as ice streams terminating on land. Therefore, the mechanism could provide insights not only on episodic glacier accelerations in the past, such as Heinrich events, but also on modern-day episodic accelerations observed from mountain glaciers and ice streams draining the Greenland and Antarctic ice sheets.

Original publication

Schannwell, C., Mikolajewicz, U., Kapsch, M.-L., Ziemen, F. (2024).  A mechanism for reconciling the synchronisation of Heinrich events and Dansgaard-Oeschger cycles. Nature Communications 15, 2961, https://doi.org/10.1038/s41467-024-47141-7


Dr. Clemens Schannwell
Max Planck Institute for Meteorology
Email: clemens.schannwell@we dont want spammpimet.mpg.de

Uwe Mikolajewicz
Max Planck Institute for Meteorology
Email: uwe.mikolajewicz@we dont want spammpimet.mpg.de

Dr. Marie-Luise Kapsch
Max Planck Institute for Meteorology
Email: marie-luise.kapsch@we dont want spammpimet.mpg.de

Dr. Florian Ziemen
German Climate Computing Center
Email: ziemen@we dont want spamdkrz.de