EGU24-12078, updated on 09 Mar 2024
EGU General Assembly 2024
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.

Understanding the influence of Atlantic Meridional Overturning Circulation interannual variability on European cold extremes

Eduardo Alastrué de Asenjo1,2, Jana Sillmann3, and Johanna Baehr2
Eduardo Alastrué de Asenjo et al.
  • 1International Max Planck Research School on Earth System Modelling (IMPRS-ESM), Max Planck Institute for Meteorology, Hamburg, Germany
  • 2Institute of Oceanography, Center for Earth System Research and Sustainability (CEN), University of Hamburg, Hamburg, Germany
  • 3Research Unit for Sustainability and Climate Risks, University of Hamburg, Hamburg, Germany

Changes in the Atlantic Meridional Overturning Circulation (AMOC) impact the redistribution of heat across the climate system and can therefore influence surface temperatures over land. A large AMOC weakening, frequently analysed through idealised model simulations (e.g., freshwater hosing experiments), would lead to a strong cooling over the Northern Hemisphere. This cooling is most pronounced for winter months, suggesting a potential influence on cold extreme events; and for Europe, this influence has been hinted at. However, whether a more realistic interannual variability in the AMOC, rather than an idealised long-term weakening, also influences European mean temperatures and cold extremes is thus far unknown.

To unravel this issue, we use the historical simulations of the 50-member MPI-ESM1.2-LR large ensemble, whose size is particularly suitable for analysing extremes. In these simulations, we categorise European temperatures based on their preceding interannual AMOC strengths. For yearly mean temperatures in a pre-industrial climate, we find that the distribution of temperatures following weak interannual AMOC strengths is significantly shifted towards colder values compared to years preceded by strong interannual AMOC strengths. Among all seasons, this shift is largest in winter; and spatially it is accentuated for northern latitudes. When considering present-day climate, the same shift still occurs, although less pronounced and strongest now for Eastern Europe. For daily extreme cold temperatures, the distribution of events is again colder following years of prevalent weak AMOC strengths; and this difference also becomes less clear and moves south-eastward in present-day climate. We complete the analysis by looking at the potential chain of physical atmospheric mechanisms that explains not only the connection between AMOC strengths and European extreme cold temperatures but also the evolution of this connection in the recent past.

How to cite: Alastrué de Asenjo, E., Sillmann, J., and Baehr, J.: Understanding the influence of Atlantic Meridional Overturning Circulation interannual variability on European cold extremes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12078,, 2024.

Comments on the supplementary material

AC: Author Comment | CC: Community Comment | Report abuse

supplementary materials version 1 – uploaded on 23 Apr 2024, no comments