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Rossby dynamics in the Mediterranean and associated Lagrangian transport properties
Enrico Zambianchi, Stefano Pierini
Università Parthenope, Napoli
enrico.zambianchi@uniparthenope.it(Abstract received 04/30/2005 for session B)
ABSTRACT
Rossby dynamics is one of the main aspects of oceanic variability. The importance of Rossby waves is first discussed in the context of large scale ocean circulation, looking at their role in shaping the wind-driven response as revelaed by altimeter data. We then focus on the Mediterranean Sea, and suggest the possibility of the presence of barotropic planetary Rossby waves in its western subbasin, and of topographic Rossby normal modes in the Straits of Sicily. We present an analytical model for Rossby normal modes in a circular domain and investigate the Lagrangian transport properties associated with them. The adimensional study is shown to be compatible with the previously discussed Mediterranean examples. As a result of chaotic advection, the first normal mode is seen to produce a strong mixing in the direction of phase propagation while the second mode produces a stronger dispersion in the normal direction. A quantitative analysis of chaotic advection is carried out by computing in several relevant cases the particle pair correlation function and the Finite Size Lyapunov Exponent. The comparison of the derived estimates of effective diffusivity with diffusivities drawn from Lagrangian data relative to the same areas shows that chaotic advection may contribute significantly to tracer dispersion in basins characterized by the presence of Rossby normal modes.
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2005 LAPCOD Meeting, Lerici, Italy, June 13-17, 2005