EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

AMOC instability during the Last Inerglacial

Augustin Kessler1, Didier Roche2,3, Eirik Galaasen4, Jerry Tjiputra1, Nathaelle Bouttes2, and Ulysses Ninnemann4
Augustin Kessler et al.
  • 1NORCE Norwegian Research Centre, Climate, Norway (
  • 2Laboratoire des Sciences du Climat et de l'Environnement, LSCE/IPSL, CEA-CNRS-UVSQ, Universite Paris-Saclay, Gif-sur-Yvette, France
  • 3Department of Earth Sciences, VU University Amsterdam, Amsterdam, The Netherlands
  • 4Department of Earth Science, University of Bergen and Bjerknes Centre for Climate Research, Bergen, Norway

Multiple evidences from the analysis of satellite, in-situ and proxy data show that the climate is already changing toward a warmer Earth System due to our emissions of CO2 into the atmosphere. However, the magnitude and the extent of changes remain difficult to predict. A change in the ocean thermohaline circulation and its consequences for climate, such as drought, regional sea-level and ocean carbon uptake remain under debate as this circulation has been long thought to be stable during warm Earth periods – Interglacials. However, recent high-resolution reconstructions of carbon isotopes (δ13C) from the deep North Atlantic challenge this idea of stability and point toward abrupt modifications in the ocean interior biogeochemistry and/or ocean thermohaline circulation during the Last Interglacial (LIG, 125ka – 115ka).


Our model simulation of the LIG reproduces the observed magnitude and timescale of the reconstructed variations of δ13C, highlighting crucial dynamical changes in two regions of the North Atlantic deep-water formation (south of Greenland and south of Svalbard). These regions are found to drive the variations in the strength of the Atlantic Overturning Circulation (AMOC) when the Arctic sea-ice extent is perturbed.


Our study suggests that the AMOC may have experienced great instability phase during some parts of the LIG. The water mass geometry reorganization from the warm onset at 125ka to the glacial inception at 115ka could also have greatly impacted the distribution of carbon in the interior Ocean. Changes in sea-ice cover either south of Svalbard or in the Southern Ocean seem to play a determining role. However, in our global warming context, our study suggests that the mechanisms responsible for the LIG AMOC instability of the LIG may not occur by the end of the century if the Arctic sea-ice retreats from the high latitudes of the North Atlantic as projected by climate models.


How to cite: Kessler, A., Roche, D., Galaasen, E., Tjiputra, J., Bouttes, N., and Ninnemann, U.: AMOC instability during the Last Inerglacial, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12364,, 2021.

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