Exploring climate change exposure of the Mediterranean Sea through 3D climate velocity

Climate change is increasingly challenging the durability of marine conservation and spatial planning approaches that rely on contemporary climate baselines. In response, the identification and protection of climate refugia – areas expected to remain relatively stable under climate change – has emerged as a key strategy for climate-smart conservation. However, in marine systems, refugia are commonly delineated using surface conditions alone, overlooking the vertical structure of the ocean. Here, we assess climate change exposure across the entire Mediterranean Sea water column using an analogue-based climate velocity framework in three-dimensional space. We compared present (2006–2030) and near-future (2031–2055) temperature conditions using nine climate variables, constraining the search for climatic analogues within ecologically meaningful depth ranges. Projected temperature conditions shifted in three dimensions across most of the basin: 45.8% of the Mediterranean exhibited combined horizontal and vertical displacement of climate conditions, while an additional 13.4% showed predominantly vertical shifts, indicating that climate change does not operate solely through horizontal redistribution. The basin-wide mean three-dimensional climate velocity was 2.98 km yr−1, with pronounced depth- and region-specific differences. Climate exposure was highest in the euphotic zone and in deep regions such as the Ionian Sea, whereas deeper biozones of the Western Mediterranean appeared comparatively more stable than those of the Eastern region. By integrating depth-resolved climate data within a fully three-dimensional framework, this study provides the first basin-scale assessment of climate velocity across the Mediterranean water column and offers a robust foundation for climate-smart conservation and planning.