Satellite Altimetry Reveals Intensification of Eddy Kinetic Energy in the Mediterranean Sea

Mesoscale activity plays a central role in ocean variability, substantially influencing the mixing of biogeophysical tracers, such as heat and carbon, and driving changes in ecosystems. Eddy Kinetic Energy (EKE), a metric used for studying the intensity of mesoscale processes, has recently been shown to increase in regions of intense EKE worldwide. Strong EKE positive trends are, for example, observed in the principal western boundary current regions, such as the Gulf Stream, Kuroshio Extension, and the Brazil/Malvinas Confluence. In this study, we assess whether the Mediterranean Sea, known to be a hotspot for climate change impacts, also exhibits such intensification. Despite the high number of observational data (in-situ, satellite) and modeling experiments, there is a gap in understanding the long-term evolution of mesoscale dynamics and EKE trends in the Mediterranean Sea. This study investigates EKE trends in the Mediterranean Sea using altimetric data from the Copernicus Marine Service. Gridded altimetric products (L4) provide daily geostrophic velocities at the ocean surface from 1993 to 2023. The EKE is calculated from anomalies of these geostrophic velocities. We analyzed EKE trends computed from three different altimetric products: a global product derived from a stable two-satellite constellation (two-sat) and two others (global and European) incorporating all available satellites (all-sat). While all products reveal a general increase of EKE in the Mediterranean Sea over the period analyzed, trends calculated from the two-sat product are significantly smaller than those computed from the all-sat products. We surmise that this discrepancy is due to the increasing number of satellites over time used to construct the all-sat datasets, which enhances both spatial and temporal coverage, and, hence, their capacity to detect higher energy levels, and/or an underestimate of the EKE detected by the two-sat product. To further investigate these trends, along-track altimetric data (L3) were also used with a specific focus on the Alboran region. This area, dominated by intense mesoscale activity, holds strong statistically significant positive EKE trends. These findings highlight the importance of using altimetric products with a stable number of satellites and constructed for climate applications when addressing long-term ocean variability analysis.