Lagrangian Coherent Structures and the Dispersion of Green Algal Bloom in the Yellow and East China Sea

Abstract

During the summer 2011, the Geostationary Ocean Colour Imager (GOCI) detected patches of the recurrent massive floating green algae in the central part of the Yellow Sea (YS) and East China Sea (ECS). This study utilizes the Lagrangian Coherent Structures (LCSs) analysis to demonstrate the horizontal dispersion pattern of algal bloom patches. This approach is based on the assumption that unstable manifolds such as ridges in the finite-time Lyapunov exponent (FTLE) fields coincide with material transport barriers. To calculate the FTLE fields, flow fields derived from the Regional Ocean Modeling System (ROMS) and wind fields were utilized. The combined effects of winds and currents in material transport in coastal and ocean environments were investigated. Comparison of LCSs derived by current only and current-wind combined flow showed that the results of current-wind combined flow cases match better the observation results from GOCI than those of current only cases. This implies that the distribution pattern of green algae patches would be controlled by the combined effect of the surface current and wind that was included LCS in terms of leeway effect.