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

Abstract

Abstract. This study presents a new set of high-resolution global climate simulations conducted with the EC-Earth3 model, including a 350 year pre-industrial, followed by historical (1850–2014) and future (2015–2100, SSP2-4.5) simulations. The model features a horizontal resolution of ∼ 40 km in the atmosphere and 0.25° in the ocean. The high-resolution EC-Earth3 (EC-Earth3-HR) is compared to the standard-resolution version used in CMIP6 to assess the impact of increased resolution on the representation of key climate variables, focusing particularly on the Arctic and North Atlantic regions. The high-resolution model aligns more closely with reanalysis data, particularly for global mean surface temperature and sea surface temperature. Both model resolutions exhibit similar biases in North Atlantic sea surface temperature and salinity, and in Arctic sea ice concentration, although the higher-resolution version shows regional improvements. The EC-Earth3-HR model captures the observed AMOC variability in the early 2000s, along with the trend and rapid loss event in Arctic sea ice. For future projection under SSP2-4.5, the high-resolution model projects a nearly ice-free Arctic by 2040 – earlier than the standard-resolution model – while simulating less Arctic warming and a more pronounced weakening of the AMOC. We also introduce a framework to diagnose deep-water formation (DWF) in the Labrador, Irminger, and Greenland Seas and to quantify their regional contributions to the AMOC. Applying this framework, we find that projected DWF weakens across all regions, with the largest reduction in the Labrador Sea, making it the dominant contributor to long-term AMOC weakening. By 2100, diagnosed DWF ceases in the Labrador Sea, compared with declines of 62 % in the Greenland Sea and 13 % in the Irminger Sea.