Diagnosing Regional Sea Level Change Over the Altimeter Era

Since 1993, satellite altimeters have been mapping sea level changes globally, revealing both the global mean rate and detailed patterns of regional variations. The global mean rate is well studied, closely linked to global energy and water cycles, while regional patterns are influenced by a complex mix of internal climate dynamics and external factors like greenhouse gases and aerosols. Yet, a synthesis of these regional patterns using a comprehensive diagnostic approach has been lacking. Our research addresses this gap by integrating oceanic and atmospheric observations with large ensembles of state-of-the-art global climate models. This approach sheds new light upon the mechanisms behind basin-scale sea level patterns worldwide. A key finding is the dominant influence of wind forcing, particularly Ekman and Sverdrup dynamics, in shaping sea level changes from the tropics to higher latitudes. We find that the pattern of sea level rise since 1993 is primarily driven by wind-induced changes in ocean circulation, which can affect sea surface height through ocean mass and heat distribution. Interestingly, these wind-driven changes are not just products of internal climate variability; most of the observed patterns are recovered by global climate model projections driven by historical anthropogenic forcings, and single-forcing experiments provide further insight into which forcings are responsible for various features in the satellite altimetry record. Understanding the drivers of regional sea level rise, including differentiating anthropogenic signals from natural variability, is essential for effectively adapting to climate change impacts on global infrastructure and society.