Observational evidence for a shift toward a warming-dominated phase of Mediterranean SST evolution

Abstract Mediterranean Sea surface temperature (SST) has warmed consistently over the past century, with a clear intensification in recent decades. Using multiple observational SST products spanning more than 170 years, we jointly analyse the low-frequency SST, T ( t ), and its temporal derivative, d T /d t , to characterize the interplay between historical multidecadal modulation and long-term warming in Mediterranean SST evolution. During the satellite era (1982–2025), the basin-mean SST exhibits a linear warming trend of 0.34 ± 0.06 °C/decade and pronounced warm-season amplification. After removing the component linearly associated with global mean SST, an Atlantic Multidecadal Variability-like modulation remains evident in Mediterranean residual variability, whereas multidecadal reversals become less apparent in the total SST record. Change-point and phase-space diagnostics indicate an early twentieth-century shift toward higher low-frequency SSTs and a late twentieth-century shift toward sustained positive warming rates, placing recent decades in a warmer and faster-warming region of the ( T ( t ), d T /d t ) phase space. Overall, the observational record suggests that long-term warming is becoming increasingly dominant in shaping Mediterranean SST variability.