Climatological Parameters Distributions Of Dissolved Oxygen In The East China Sea And Its Application In The Oceanography

Dissolved oxygen (DO) is not only the indispensable substance of maintaining the metabolism of marine lives, but also an important parameter in the investigation of marine biogeochemistry cycles. As Temperature (T) and Salinity (S), DO have been taken as an essential parameter in almost all marine researches. A basic understanding of the function of DO in the marine biogeochemistry has been set up based on previous studies, especially the DO atlas in the oceans of the world. However, up to now, we still have no systemic understanding of the characteristic of DO in the East China Sea (ECS), the foremost marginal sea of China. In this thesis we introduce data analysis procedures and horizontal maps showing annual, seasonal, and monthly climatologies of the DO in addition to the dissolved oxygen saturation (O2S) and the Apparent Oxygen Utilization (AOU) at selected standard depth levels between the surface and bottom in the ECS. We also take a preliminary discussion of chemical oceanography on DO in this area. The conclusions are as follows:This thesis presents an atlas which contains 510 plane distributions of the DO parameters (DO, O2S and AOU) in ten selected standard layers.From the figures of yearly mean value and seasonal and monthly distribution of dissolved oxygen (DO), below 50 m, the DO isolines at each standard layer are inclined to parallel the isobaths in the bottom; and the isolines above 50m follow this trend in yearly average and winter & spring distribution. Additionally, the DO contents of surface and bottom seawaters decline from northwest to southeast; opposite to the change of isotherm, which suggesting that the DO is determined by temperature in this area. While it does not show good parallel between the DO isolines and isobaths above 50m, but distributes in mass.The High value of the DO can be an index of the existence of cold eddy water in the ECS. And the change of the central DO high value zone seems to predict the formation and migration of the cold eddy water in the ECS. There was a peak of DO at upper level with the maximum concentration showed in April. But the peak of the O2S exhibited a month later (May). The DO and the O2S shared a similar change curve which seems to be a sine curve. Temperature and AOU also have a similar curve, but the tendency is opposite.There is a small range of high DO water in winter above 10 m, which located at 32°N, 122°E in the east of the Changjiang Estuary, especially in February. This may be due to the mixture of different waters, and this area could be a weak source of air-sea interfacial exchange of the oxygen.The DO and the O2S in the upwelling area of northeast Taiwan are obviously lower than the surrounding area, which means that the distribution of O2S could be an tracer of upwelling in winter.It is indicated from the historical data that serious hypoxia areas existed as early as half a century ago. The case has become even worse since 1980s. But it seems that the hypoxia zone does not become serious through the DOmin and the DOave., Maybe we have underestimated the complexity of hypoxia zone off the Changjiang Estuary.The diagram of O2S appears as a three-peak-structure in a yearly change. And both DO and O2S show a"V"in the bottom layer. The biogeochemical process of DO in the hypoxia zone can be classified into two types, the former is the oxygen consuming process (from Feb. to Aug.), while the later is oxygen supplying process (from Aug. to Feb. in next year). It is feasible to account for the mechanism of hypoxia zone according to the calculation, but a deep research will be done to give a quantitative explanation.Compared to the SOA Atlas, we find our atlas is better in both the spatial representability of the station and the time scale. In addition, we also find something wrong with the DO concentration in SOA Atlas, which needs to be corrected.