EGU24-10579, updated on 08 Mar 2024
https://doi.org/10.5194/egusphere-egu24-10579
EGU General Assembly 2024
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.

A mechanism for reconciling the synchronisation of Heinrich events and Dansgaard-Oeschger cycles

Clemens Schannwell1, Uwe Mikolajewicz1, Marie-Luise Kapsch1, and Florian Ziemen2
Clemens Schannwell et al.
  • 1Max Planck Institute for Meteorology, Ocean Physics, Germany (clemens.schannwell@mpimet.mpg.de)
  • 2Deutsches Klimarechenzentrum, Germany

The evolution of the northern hemispheric climate during the last glacial period was shaped by two prominent signals of glacial climate variability known as Dansgaard-Oeschger cycles and Heinrich events. Dansgaard- Oeschger cycles are characterised by a period of rapid, decadal warming of up to 14°C in the high northern latitudes, followed by a more gradual cooling spanning several centuries. Temperature reconstructions from ice cores indicate a dominant recurrence interval of ∼1,500 years for Dansgaard-Oeschger cycles. Heinrich events are quasi-episodic iceberg discharge events from the Laurentide ice sheet into the North Atlantic. The paleo record places most Heinrich events into the cold phase of the millennial-scale Dansgaard-Oeschger cycles. However, not every Dansgaard-Oeschger cycle is accompanied by a Heinrich event, revealing a complex interplay between the two prominent modes of glacial variability that remains poorly understood to this day. Here, we present simulations with a coupled ice sheet-solid earth model to introduce a new mechanism that explains the synchronicity between Heinrich events and the cooling phase of the Dansgaard-Oeschger cycles. Unlike earlier studies, our proposed mechanism does not require a trigger mechanism during the cooling phase. Instead, the atmospheric warming signal associated with the interstadial phase of the Dansgaard-Oeschger cycle causes enhanced ice stream thickening such that a critical ice thickenss and temperature threshold is reached faster, triggering the Heinrich event during the early cooling phase of the Dansgaard-Oeschger cycle. An advantage of our mechanism in comparison to previous theories is that it is not restricted to marine-terminating ice streams, but applies equally to land-terminating ice streams that only become marine-terminating during the actual Heinrich event. Our simulations demonstrate that this mechanism is able to reproduce the Heinrich event characteristics as known from the paleo record under a wide range of forcing scenarios and provides a simple explanation for the observational evidence of synchronous Heinrich events from different ice streams within the Laurentide ice sheet.

How to cite: Schannwell, C., Mikolajewicz, U., Kapsch, M.-L., and Ziemen, F.: A mechanism for reconciling the synchronisation of Heinrich events and Dansgaard-Oeschger cycles, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10579, https://doi.org/10.5194/egusphere-egu24-10579, 2024.