EGU25-17351, updated on 15 Mar 2025
https://doi.org/10.5194/egusphere-egu25-17351
EGU General Assembly 2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
North Atlantic Deep Mixing Patterns Affect AMOC Responses to Abrupt-4xCO2 forcing
Muxin Hu, Joas Müller Müller, and Robert Jnglin Wills
Muxin Hu et al.
  • Institute for Atmospheric and Climate Science, Department of Environmental Systems Sciences, ETH Zürich, Zürich, Switzerland

The Atlantic Meridional Overturning Circulation (AMOC) is a crucial component in the Earth's climate system. Despite extensive research on the AMOC response to climate forcings, substantial discrepancies persist across models. These discrepancies may partly stem from differences in the representation of North Atlantic deep convection, particularly in the location of primary convection regions. This study investigates how difference in North Atlantic deep mixing patterns influence the AMOC response to CO2 forcing, using pre-industrial control and abrupt-4×CO2 experiments from 14 CMIP6 models. Based on winter mixed-layer depth (MLD) climatologies, we identified three main regions of North Atlantic deep mixing: the Labrador Sea, Irminger & Iceland Basins, and the Greenland-Iceland-Norwegian (GIN) Seas. Utilizing principal component analysis and k-means clustering, we identify two groups of models: (1) the LII cluster, with stronger mixing in the Labrador Sea and Irminger & Iceland Basins and (2) the GIN cluster, exhibiting stronger mixing concentrated in the GIN Seas. We find that the two clusters have similar mean-state AMOC in the pre-industrial scenario despite significant differences in regions of deep mixing. However, their projected responses to abrupt forcing diverge significantly. The LII cluster exhibits much stronger weakening and shoaling of the AMOC compared to the GIN cluster. Preliminary analyses of sea ice fraction indicate notable differences in the Labrador Sea. In the LII cluster, large parts of the Labrador Sea are ice-free, typical of models that are relatively warm and salty in the North Atlantic, whereas the GIN cluster demonstrates relatively high sea ice concentration, with its southern edge extending further. Our results suggest a possible link between deep convection representations and AMOC responses to greenhouse gas emissions, offering a potential reference for assessing model accuracy in projecting AMOC changes based on their climatological representation of deep mixing.

How to cite: Hu, M., Müller, J. M., and Jnglin Wills, R.: North Atlantic Deep Mixing Patterns Affect AMOC Responses to Abrupt-4xCO2 forcing, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17351, https://doi.org/10.5194/egusphere-egu25-17351, 2025.