Three-dimensional Characteristics Of Isolated Water Mass And Its Resulting Material Transport Off Changjiang Diluted Water Extension Area

The Changjiang Diluted Water plays an important role in biochemical and sediment transport in the East China Sea.Its extension presents various patterns.The most obvious feature is that it turns to the northeast in summer.The mechanism of Changjiang Diluted Water has been a hot issue for a long time.The study in the north and south of Changjiang estuary from May to June 2017 shows the detachment of water mass in Changjiang Diluted Water expansion area,then move toward Jeju Island.This phenomenon has been found in some estuary all over the world,such as Columbia estuary.Based on in-situ observation off the Changjiang estuary in May 2017 and associated satellite-derived data,the three-dimensional structure and transport process of isolated lowsalinity water mass are investigated.Historic low-salinity water mass detachment events are also studied,which shows that the strong upwelling caused by tides dominates the detachment of low-salinity water mass.The life cycle of isolated low-salinity water mass is 7 to 10 days and its length is about 100 km.The detachment often occurs around 122°30?E,32°N in Changjiang estuary.Also,the detachment and transport are affected by the Changjiang runoff,wind field and anti-cyclonic eddy.The northerly and southerly wind inhibit and promote the transport process respectively.The impact of anti-cyclonic eddy on isolated low-salinity water mass is always negative.Detached low-salinity water mass enhances transport of nutrients and organic matter with diluted water,which has significance for the coupling between hydrodynamic process and ecological environment.Moreover,this study enhances our understanding of the detachment and transport of the low-salinity water mass off the Changjiang estuary.