Drifter dispersion in the Adriatic Sea: Lagrangian data and chaotic model

We analyze characteristics of drifter trajectories from the Adriatic Sea wi th recently introduced nonlinear dynamics techniques. We discuss how in qua si-enclosed basins, relative dispersion as a function of time, a standard a nalysis tool in this context, may give a distorted picture of the dynamics. We further show that useful information may be obtained by using two relat ed non-asymptotic indicators, the Finite-Scale Lyapunov Exponent (FSLE) and the Lagrangian Structure Function (LSF), which both describe intrinsic phy sical properties at a given scale. We introduce a simple chaotic model for drifter motion in this system, and show by comparison with the model that L agrangian dispersion is mainly driven by advection at sub-basin scales unti l saturation sets in.