Intraseasonal variation in the salinity of the Yellow and East China Seas in the summers of 2011, 2012, and 2013

Hydrographic data obtained during eight cruises in the summers of 2011, 2012, and 2013 reveal a substantial intraseasonal variation in the salinity of the Yellow and East China Seas. Salinity variation reflects changes in the water masses in which jellyfish grow from juveniles to adults and changes in the circulation system that can transport jellyfish. The primary change occurred in surface salinity due to inconstant plume pathways caused by the swerve of the offshore current. Distinctive events occurred in the Yellow Sea in 2012, and also occurred in a zone spanning from the mouth of the Changjiang to Jeju Island in 2013. The observations indicated the advancement and recession of the Taiwan Warm Current (TWC), especially its inner branch and the Kuroshio intrusion, induce substantial variations during summer (June, July and August). Atmospheric forcing, the buoyancy input from rivers, Kuroshio transport and a water level discrepancy between the Bashi Channel and the Taiwan Strait that controls the TWC, influence the circulation regime. The changes in all of the aforementioned forcings need to be recorded to understand the mechanism of the dynamic patterns in water masses, temperature and salinity and predict the characteristics of the jellyfish blooming environment.