Mediterranean Sea seasons from submesoscale measured by Swot

The Mediterranean Sea is sometimes considered as a smaller version of the global ocean - a number of phenomena occuring in the vaster basins can be observed there, including vertical mixing, meso and submesoscale circulation, etc. It is also a region with dense population, fast-changing climate, heavy maritime traffic... all potentially impacted by ocean circulation, small and large-scale alike.

One of the breakthrough expected from Swot was to detail and measure the seasonality of submesoscale ocean features. Now, with about three years of "science" phase on the 21-day repetitive orbit, enough seasons have passed to begin checking on this. A joint team from France and Balears Islands looked at the Mediterranean sea small-scale structures along the seasons in Swot Sea Surface Height data. Resolving finer scales, particularly in the 20–60 km range, increases both the mean Eddy Kinetic Energy and the amplitude of its seasonal variations, compared with merged multimission nadir-only data equivalent. Swot-derived Eddy Kinetic Energy is nearly twice that inferred from conventional gridded altimetry. The winter intensification is strongest at scales below about 60 km, while larger-scale motions exhibit a different seasonal behaviour.

Normalized geostrophic relative vorticity, as indicator of intensity and structure of surface dynamics, computed for summer and winter shows higher values in winter, corresponding to expected intensification of submesoscale activity in the mixed layer. Longer time series should precise those findings, as the Swot missions continues.