EGU24-4017, updated on 08 Mar 2024
EGU General Assembly 2024
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.

The weakening AMOC under extreme climate change

Gaurav Madan1, Ada Gjermunsen1,2, Silje C. Iversen3, and Joseph H. LaCasce1
Gaurav Madan et al.
  • 1Section for Meteorology and Ocean Sciences, University of Oslo, Blindernveien 31, 0371 Oslo, Norway
  • 2Division for Climate Modelling and Air Pollution, Norwegian Meteorological Institute, Henrik Mohns plass 1,0313 Oslo, Norway
  • 3Department of Physics and Technology, UiT The Arctic University of Norway, P.O. Box 6050 Langnes, 9037 Tromsø,Norway

Changes in the Atlantic Meridional Overturning Circulation (AMOC) in the quadrupled CO2 experiments conducted underthe sixth Coupled Model Intercomparison Project (CMIP6) are examined. Increased CO2 triggers extensive Arctic warming,causing widespread melting of sea ice. The resulting freshwater spreads southward, first from the Labrador Sea and then theNordic Seas, and proceeds along the eastern coast of North America. The freshwater enters the subpolar gyre north of theseparated Gulf Stream, the North Atlantic Current. This decreases the density gradient across the current and the currentweakens in response, reducing the inflow to the deepwater production regions. The AMOC cell weakens in tandem, firstnear the North Atlantic Current and then spreading to higher and lower latitudes. This contrasts with the common perceptionthat freshwater caps the convection regions, stifling deepwater production; rather, it is the inflow to the subpolar gyre thatis suppressed. Changes in surface temperature have a much weaker effect, and there are no consistent changes in local orremote wind forcing among the models. Thus an increase in freshwater discharge, primarily from the Labrador Sea, is theprecursor to AMOC weakening in these simulations.

How to cite: Madan, G., Gjermunsen, A., Iversen, S. C., and LaCasce, J. H.: The weakening AMOC under extreme climate change, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4017,, 2024.