Observational Evidence for Accelerated Warming and Salinification Propagating Into the Deep Mediterranean

Abstract Acceleration, rather than a gradual linear response, is emerging as a defining feature of ocean change in the Anthropocene. Surface‐forced warming propagates into the deep ocean over decades to centuries, but semi‐enclosed basins such as the Mediterranean Sea may respond more rapidly. Here, we analyse an in situ Mediterranean‐wide multiplatform data set spanning 1950–2025 and show that warming and salinification of the upper 1,000–2,000 m are not only continuing but accelerating, at increasing rates over the record. Acceleration rates reach up to 0.3°C decade −2 for temperature and 0.1 decade −2 for salinity. Coastal shallow basins exhibit additional acceleration in processes that precondition changes in deep basins, including warming of dense waters that cascade to the deep Mediterranean. These results indicate rapid, ongoing changes in Mediterranean water‐mass properties and position the basin as a natural laboratory for detecting and constraining accelerating ocean change.