Sensitive dependence of trajectories on tracer seeding positions – coherent structures in German Bight backward drift simulations

Abstract. Backward drift simulations can aid the interpretation of in situ monitoring data. In some cases, however, trajectories are very sensitive to even small changes tracer release position. A corresponding spread backward implies attraction forward passage time and, hence, uncertainty about probed water body's origin. This study examines surface German Bight (North Sea). Lines across which behaviour non-smoothly obtained as ridges fields finite-time Lyapunov exponent (FTLE), a parameter used dynamical systems theory identify Lagrangian coherent structures (LCSs). Results closely resemble those considering two-particle relative dispersion. It is argued that simulated FTLE might be support data, indicating when unreliable because their high sensitivity seeding positions.