Decadal variability in the Eastern and Western Mediterranean sea level trends

Abstract

The Mediterranean Sea, a semi-enclosed basin highly sensitive to climate change, exhibits complex variability in sea level trends with important environmental and societal implications. This study investigates the sea level rise decadal variability from 1993 to 2024 at sub-basin and coastal scales using satellite altimetry, ocean reanalyses, and tide gauges records. In the Western Mediterranean (WMED) sea level decadal trend has recently accelerated, partly driven by thermal expansion that exceeds halosteric contraction, with the remaining contribution likely associated with sea level mass variability. In the Eastern Mediterranean (EMED) sea level transitioned from a regime dominated by halosteric-induced drop to a recent state where steric contributions offset each other, allowing mass variability to dominate. Local trends generally confirm satellite-derived patterns, though larger differences reported in the EMED highlight the influence of regional processes, including vertical land movement. These results confirm that Mediterranean sea level change is non-linear, with decadal variability superimposed on a long-term positive trend, emphasizing the need to account for such fluctuations in regional adaptation strategies and coastal risk management.