Fig. 3

Spirals on the sea. Sun-glint pattern in a photograph by an astronaut Scully-Power (1986) over the Mediterranean not far off the coast of North Africa. The lines are created by surfactants concentrated in convergence lines that alter the scattered reflection by short-surface gravity waves. Their patterns are organized by submesoscale currents. The vortex diameters are \(\approx\) 5 km, and the surfactant lines are \(\approx\) 100 m wide. The pattern suggests that a vortex-street roll-up has occurred from a lateral shear instability of some antecedent front, filament, or headland wake