Fig. 1.

Overview of global submesoscale structures and distributions. a Satellite image of a large bloom of cyanobacteria in the Baltic Sea on August 11, 2015 showing submesoscale eddies, fronts, and filaments. Figure 1a sourced from NASA (images by Norman Kuring, NASA's Ocean Color Web). See https://landsat.visibleearth.nasa.gov/view.php?id=86449. b Observations¹¹ of submesoscale structures from sunglitter in the Andikithiron Channel northwest of Crete on October 7, 1984. Ship tracks are labeled A, B. c, d Simulated global snapshot of ocean turbulence at ~2-km resolution, as well as expanded views for local regions, for c Northern and d Southern Hemisphere winters. The quantity shown is relative vorticity (s⁻¹), a measure of the spin of fluid parcels, that emphasizes fast-rotating submesoscale turbulence especially in the winter hemisphere (see Supplementary Figure 1 for Rossby number). The same global maps but with a higher pixel resolution can be found at web.gps.caltech.edu/~zhan/nailed/Figure1a.png