Decomposing steric and dynamic sea level trends in a future high-emission scenario of the Mediterranean Sea

Over the past few decades, the rise of sea level has emerged as a critical concern for coastal regions across the globe, driving intense scientific efforts to understand the underlying processes. However, disentangling and interpreting ocean physics’ contributions (sterodynamic) to these changes remains a complex challenge. To contribute to a better understanding of future sea level rise patterns, this study proposes a sterodynamic sea level decomposition for Boussinesq models with a specific focus on the mass change contribution. In particular, we explore the interplay between mass and density-driven changes and disentangle the respective influences of freshwater and salt mass changes. Based on a high-emission (SSP5-8.5) coupled regional projection of the Mediterranean climate system, we apply this methodology to the Mediterranean Sea.
Under the investigated scenario, the Mediterranean sterodynamic sea level is projected to rise by 32 cm by the end of the 21st century. We find that 24 cm are attributable to the global ocean temperature increase and 8 cm to regional hydrographic and mass changes, the so-called “dynamic sea level change”. Focusing on these regional patterns, our results reveal that the mediterranean dynamic sea level rise is predominantly caused by an increase in salt mass. Specifically, this increase results from an enhanced net volume transport through the Strait of Gibraltar in response to increased evaporation and steeper sea level gradient with the Atlantic Ocean. Finally, we attribute local sea level variations to changes in the mediterranean circulation and horizontal density variations. Overall, this study emphasizes the added value of a comprehensive decomposition of mass’ contribution for interpreting future sea level rise patterns.