Meeting Abstracts
Using Lagrangian Coherent Structures to understand coastal water quality
Laura Fiorentino, Josefina Olascoaga, Javier Beron-Vera, Ad Reniers, Zhixuan Feng
RSMAS
(Abstract received 05/14/2012 for session B)
ABSTRACT
The accumulation of pollutants near the shoreline can result in low quality coastal water levels with negative effects on human health. To understand the water quality of a particular beach requires the study of the Lagrangian circulation in the vicinity of the beach in question. Here we demonstrate the utility of dynamical systems methods in achieving such an understanding. The specific dynamical system notion considered is that of Lagrangian Coherent Structure (LCS). Hidden in the currents, the LCSs constitute the centerpieces of patterns formed by fluid particle trajectories. As such, the LCSs act as skeletons of the Lagrangian circulation. Particular focused is placed on Hobie Beach, a recreational marine beach located in Virginia Key in Miami, Florida. According to studies of water quality, Hobie Beach is characterized by high microbial levels. Possible sources of pollution in Hobie Beach include human bather shedding, dog fecal matter, and sand efflux at high tides. Consistent with the patterns formed by satellite-tracked drifter trajectories, the LCSs extracted from simulated currents reveal a Lagrangian circulation which favors the retention near the shoreline of pollutants released along the shoreline, which can help explain the low quality water levels registered at Hobie Beach.