On physical factors that controlled the massive green tide occurrence along the southern coast of the Shandong Peninsula in 2008: A numerical study using a particle-tracking experiment

A Lagrangian-particle-tracking experiment has been conducted using Regional Ocean Modeling System to determine physical factors that controlled the occurrence of the record-breaking massive green tide along the southern coast of the Shandong Peninsula (SP) in 2008. The numerical results reveal that the southerly wind in May is responsible for the offshore movement of the green tide from the Jiangsu Province and the easterly wind in June is responsible for its extension up to the coast of the SP. From the analysis of 30 year wind fields, it was also found that the wind patterns in 2008, which were very unique and rare, provided the most favorable conditions for the migration of the bloom to the SP. Through analyzing the pathway of particles, a recurrent upwelling region due to tides was found between the Jiangsu coast and the western Yellow Sea where the massive green tide bloomed. This area seems to provide nutrients for the green tide blooms. In particular, it is estimated that the nutrient supply in 2008 was large because the upwelling occurred during a spring tide. These results suggest that the massive green tide along the SP in 2008 occurred due to the combination of a recent rapid expansion of seaweed aquaculture, unique wind patterns, and nutrient supplies due to strong tidal forcing in blooming regions. This implies that the massive green tides in the SP could occur again as a very rare event if all conditions become favorable for the blooming and migration in the future.