Effect of SST change of the Mediterranean sea and Atlantic Ocean over Western Europe over a 30-years period

With climate change accelerating, a key open question is how ocean warming will modulate regional atmospheric conditions. Sea-surface temperature (SST) is a major boundary condition forcing for the atmosphere, influencing near-surface temperature, humidity, and precipitation. We quantify the atmospheric response to prescribed SST warming using a suite of long, convection-permitting regional climate simulations with the Weather Research and Forecasting (WRF) model.

We performed 7 continuous simulations spanning 1996–2024 (29 years), centered on France and Western Europe, with a horizontal resolution of 20 km (90 × 80 grid points). One of the simulations serves as a baseline/reference case. The remaining six experiments impose SST perturbations designed to emulate end-of-century warming and to isolate the role of different basins. They form two families: (i) warming applied to the Mediterranean Sea only, and (ii) warming applied to both the Mediterranean Sea and the Atlantic Ocean. Within each family, three SST-forcing scenarios are considered: (1) mean SST anomalies representative for the year 2100 under RCP4.5, (2) mean SST anomalies representative for 2100 under RCP8.5, and (3) a “trend-shift” case in which SSTs are localy offset by the observed/prescribed multi-decadal SST increase, effectively shifting boundary conditions toward a warmer future.

We compare all experiments with the reference simulation to diagnose the regional climate's sensitivity to SST warming, focusing on near-surface air temperature and precipitation. The analysis distinguishes the magnitude of the response and the relative contributions of Mediterranean versus Atlantic warming, providing a controlled assessment of basin-specific SST impacts on Western European climate over multi-decadal timescales. The first conclusion is that, for RCP 4.5 and 8.5, the land temperatures show little change on average. However, when only the Mediterranean Sea is heated, a temperature anomaly of up to 5°C occurs north of the Atlantic Ocean. Further analysis is underway as the simulations run.