Historical Climate and Future Projection in the Arctic and North Atlantic: Insights from High-Resolution EC-Earth3 Simulations

Future climate projections in CMIP indicate that sea ice will continue to decline under all emission scenarios, although there is uncertainty regarding the timing of a summer ice-free Arctic. Additionally, while models agree that the Atlantic Meridional Overturning Circulation (AMOC) will weaken, they diverge on the rate of weakening and the underlying processes. Results from the HighResMIP initiative have highlighted the benefits of increased model resolution in improving the representation of key climate processes in the North Atlantic and Arctic oceans.

Building on this, we use the high-resolution global climate model EC-Earth3-HR, a higher-resolution version of the EC-Earth3 configuration developed for CMIP6, to investigate future changes in the Arctic and North Atlantic Oceans. EC-Earth3-HR consists of the IFS atmospheric model (T511, ~40 km), the NEMO ocean model (0.25°), and the LIM3 sea ice model. The model has undergone a tuning process, a long spin-up, and 350 years of pre-industrial control simulations, followed by full historical (1850–2014) and future (2015–2100, SSP2-4.5) simulations.

We will highlight the impact of increased horizontal resolution, compared to the lower-resolution version, on simulating the historical climate, with a focus on ocean and sea ice conditions in the North Atlantic and Arctic and their projected changes under SSP2-4.5. Our results show that EC-Earth-HR effectively captures sea ice trend and rapid sea ice loss events, and projecting a summer ice-free Arctic by 2050. It also shows a 40% weakening of the AMOC by the end of the century. Furthermore, we present a novel method for estimating deep water formation rates and examining the processes contributing to the weakening of the AMOC.