Future projections of sea level rise in the Mediterranean Sea

Future sea level change in the Mediterranean Sea is one of the major climate hazards for populations living in low-elevation coastal zones (≤10 m above mean sea level). In this study, we analyze projections of mean sea level rise in the Mediterranean Sea by the end of the 21st century. To address this, we use a set of multi-decadal simulations from three pairs of regional climate system models (RCSMs) of the Med-CORDEX initiative together with the simulations of their driving global climate models (GCMs). For the first time, we analyze the mean relative sea level simulated by a set of high-resolution and fully coupled regional models to provide a detailed characterization of regional and local patterns of future Mediterranean sea level change. By 2100, under the high-emission SSP5-8.5 scenario, the basin-averaged total sea level is projected to rise by +71 cm from RCSMs and +76 cm from GCMs (central estimates). Among the sea level components, the sterodynamic term (dynamic sea level + global mean thermosteric sea level) is the largest contributor to total sea level rise, with 91% of its contribution driven by global thermal expansion. The sterodynamic term and the vertical land motion drive local sea level adjustments in regions such as the Balearic Sea and the Ionian islands, leading to the highest sea level rise in the Mediterranean. We find that sea level rise in the Mediterranean is expected to be slower than the nearby Atlantic due to a dynamic adjustment within the basin. Furthermore, compared to the GCMs, the RCSMs show a higher spread (extremes) of the sea level response without a mean regional effect.