On the role of filamentation in the merging of anticyclonic lenses

Abstract

It has been previously noted that, if two warm-core rings were to merge to form a single new eddy, there would be more energy in the final state than in the initial, premerging state, and that therefore, merging is energetically prohibited. However, field and laboratory observations reveal spontaneous merging occurrences and thus challenge this energy argument. The paradox is resolved here by noting that the merging need not be complete; specifically, that the final state in fact consists of a center eddy containing almost all the energy but only a fraction of the mass, surrounded by a pair of thin filaments holding the mass difference, a residual of energy and most of the angular momentum. Existing numerical and experimental results point to the likelihood of such a composite state as the outcome of the merging of two warm-core rings.