Impacts of an AMOC collapse on the North Atlantic jet stream and storm track

The Atlantic Meridional Overturning Circulation (AMOC) has a strong influence on global and regional climate. In particular over Europe, previous works have shown that an AMOC tipping to a weak state would lead to a substantial cooling and drying, especially in the high latitudes. In this work, we aim at identifying the impacts of an AMOC collapse to the atmospheric circulation in the North Atlantic by looking at the jet stream and the storm track and link them with changes in the European climate variability and extremes.

We use dynamically downscaled regional climate simulations at 15 km resolution over a 20-year period run with the Weather Research and Forecasting model (WRF). These regional simulations are forced by fully-coupled global runs performed with multiple Earth System models under various prescribed conditions. The experiments consist of a simulation with stable global warming of 2 K and an imposed AMOC collapse on top of the stable global warming. Cyclones are tracked in the WRF simulations and their number, intensity and associated impacts (strong winds and/or heavy precipitation) in the global warming and AMOC collapse experiments are compared to a baseline simulation with pre-industrial forcing. The physical processes leading to the identified changes in the storm track are also studied. This analysis allows us to better understand the modifications in atmospheric dynamics caused by crossing a tipping point and to quantify the subsequent impacts.