Rotation of floating particles in submesoscale cyclonic and anticycloniceddies: a model study for the southeastern Baltic Sea

Abstract. It was assumed that the overwhelming dominance of cyclonic spirals on satellite images of the sea surface could be caused by some sort of differences between rotary characteristics of the submesoscale cyclonic and anticyclonic eddies. This hypothesis was tested by means of numerical experiments with synthetic floating Lagrangian particles embedded in a regional circulation model of the southeastern Baltic Sea with very high horizontal resolution (0.125 nautical mile grid). The numerical experiments showed that the cyclonic spirals can be formed both from a horizontally uniform initial distribution of floating particles and from the initially lined up particles during the advection time of the order of 1 day. Statistical processing of the trajectories of the synthetic floating particles allowed to conclude that the submesoscale cyclonic eddies differ from the anticyclonic eddies in three ways favouring the formation of the spirals: the former can be characterized by a considerably higher angular velocity and a more pronounced differential rotation as well as by a negative helicity.