Fig. 5

Submesoscale surface vortex. A satellite image of plankton concentrated in surface convergence lines in the Baltic Sea. The lines indicate a submesoscale central cyclone with spiral arms that are dense filaments. A similar behavior is seen in a set of convergent surface drifter trajectories, first into an arm and then into the cyclone center, in the Gulf of Mexico (D’Asaro et al. 2018), but in a separate event from that depicted in Fig. 4