Observed and Simulated Drifter Tracks and Lyopanov Exponents During the RIVET 2012 Experiment

GPS-tracked drifters are used to investigate tidally driven flow at the New River Inlet, NC during the RIVET 2012 experiment. Observed Drifters were released on 8 days of the experiment during ebb, flood, and slack tides. Model currents are obtained for the observed drifter times using the nearshore circulation model NearCom forced by observed tides. Simulated drifter tracks, with the same release location and duration to the observed tracks, are found using the modeled currents to advect model drifters. The observed and simulated drifter tracks, and therefore observed and simulated drifter velocities, are compared. Lyopanov exponents of simulated drifter tracks are also determined. High/low values of the Lyopanov exponent indicate that two particles initially close together quickly/slowly separate from each other. Hence, ridges in the maps of Lyopanov exponents help to determine 1) whether ocean water on a flood tide returns to the ocean on ebb tide, 2) whether fresh inlet water on an ebb tide returns to the inlet on flood tide, and 3) the sensitivity of drifter paths to initial release locations.