Seasonality of surface turbulence in the Mediterranean Sea observed from space

The Mediterranean Sea is a climate change hotspot, experiencing warming rates faster than the global average. However, its surface fine-scale dynamics remain largely unexplored, despite robust evidence that oceanic fine scales play a key role in regulating the oceanic energy cycle, material transport, and air–sea exchanges, with direct implications for climate. Here, we use the Surface Water and Ocean Topography (SWOT) mission resolving sea surface height at kilometer scales, enabling the observation of surface submesoscale dynamics previously inaccessible to conventional altimetry. Using two years (from August 2023 to November 2025) of SWOT L3 swath sea surface height data, we show for the first time that surface dynamics in the Mediterranean Sea exhibit a clear seasonal cycle. SWOT reveals eddy kinetic energy levels 1.8 times higher than those previously obtained by conventional gridded altimetry products. The basin-mean eddy kinetic energy increases by 50% from summer minima to winter maxima while standard altimetry product do not exhibit this seasonal variability. Strain and relative vorticity distributions likewise display a clear seasonal cycle, in agreement with the seasonal variability of eddy kinetic energy. These results demonstrate that submesoscales fundamentally revise the observed energy and seasonality of Mediterranean surface dynamics with an impact on climate.