Dissolved Oxygen Distributions in Seawaters

In the 100 m depth coastal region, the mixture of upper and lower layers was strong so there was little difference between DO in the upper and lower layer seawater. But the seawater mixture in Leg 9410 was better than that in Leg 9404, so the DO was very low in the bottom waters in Leg 9404. In 100 m depth stations, the DO decreased with depth. The DO in seawater in Leg 9310 was similar to that in Leg 9410, but was obviously different from that in Leg 9404. The DO concentrations in Leg 9404 were higher than those in Leg 9310 and Leg 9410. It was obvious that the DO in seawater was mainly controlled by seasonal temperature. The subsurface maxima of DO appeared at only several stations. 

DO sectional distribution differences in various Legs could be due to  

In summary, seasonal temperature and climatic conditions were the main factors controlling ECS DO variation in Leg 9404 and Leg 9410 in the ECS. 

2 Dissolved Oxygen Concentration in the Changjiang River Estuary 

Generally, waters around the Changjiang River Estuary can be classified as three principal water masses (1) freshwater from the Changjiang River (2) seawater (continental shelf waters) entering the ECS, either with the Yellow Sea along shore current from the north or with the Taiwan Warm Current and its branches from the south (3) the transition zone between freshwater and seawater, resulting in estuarine mixed water. 

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