Typhoon-induced Full Vertical Mixing and Subsequent Intrusion of Yangtze Fresh Waters in the Southern Yellow Sea: Observation with an Underwater Glider and GOCI Ocean Color Imagery

Typhoons have been regarded as an important forcing to control oceanographic phenomena, particularly in the Yellow and East China Seas. The influences of typhoons have become increasingly severe due to global warming. An autonomous underwater glider was deployed west of Jeju Island for 10 days from 15th to 25th August, 2018 to observe changes in physical environments induced by Typhoon Soulik. The glider data show that the stratified water masses were destroyed by the typhoon into a fully mixed stage of the entire water column. This de stratification is manifested by many environmental parameters including temperature, salinity, chlorophyll-a, and suspended sediment concentrations. Accordingly, calculated parameters, density, and Richardson number, indicate de-stratification. The water column displayed, however, a rapid return to the stratification stage immediately after the typhoon passage. In addition, the GOCI geostationary ocean color imagery was analyzed that were obtained during and after the passage of Soulik between 15-25 August, 2018. These satellite images suggest that the discharge of the Yangtze River fresh water so increased during the typhoon that the intensified freshwater plume could move toward Jeju Island. As a result, observations with an autonomous glider may provide a promising means in analyzing oceanographic processes occurring during the peak of typhoons.