The Variation Characters And Formation Mechanism Of Salinity In The Bohai Sea

The Bohai Sea and the Yellow Sea are the semi-enclosed shallow seas, with the unique environmental and dynamic characters. So far, the factors that affect the increase of salinity in the Bohai Sea has been analyzed preliminarily, but the formation mechanism of variation, especially the cause of interannual variation and the relative change of circulation in the Bohai Sea, have not been studied. All these questions are the most fundamental aspects to study the environmental variation in the Bohai Sea. As mentioned above, this paper studies the characters and formation mechanism of variation of salinity and related circulation.First, based on the historically observed data, the temperature and salinity as well as related climatology elements of the Bohai Sea and the Yellow sea are analyzed. The results show that the temperature and salinity have increased considerably, and the phenomena not only exist in the Bohai Sea and the Yellow Sea, but also appear on PN section in the East China Sea. In fact, the salinity in the Bohai and Yellow Seas not only has long-term variation, but also has remarkable interannual variation. The interannual variation of evaporation and precipitation is consistent with the variation of salinity, the interannual variation of salinity is probably induced by evaporation and precipitation. But the salinity in the East China Sea dose not have the same interannual variation because the water exchange with the Kuroshio is huge and the vapor flux has little influence on it.The effect of precipitation of the Bohai Sea and the Yellow Sea on the salinity is analyzed. We use the way of EOF analyses to study the spatial distribution of it and use the way of SVD analyses to study the relationship between salinity and temperature in global sea surface anomaly and as well as the wind. Consequently, the formation mechanism of interannual variation of salinity is explained further.As we all know, the long-term variation of salinity in the Bohai Sea is influenced by Yellow River flux, evaporation, precipitation and water exchange with the North Yellow Sea. So we use the Princeton Ocean Model to diagnose and analyzed contribution of each factor to the variation of salinity. First, when all the factors are considered, the formation of salinity in 1980s'is simulated successfully. The result shows: when the salinity increases, the density of sea water will increase accordingly, and the circulation velocity in summertime will increase while the structure dose not chang. But the increasing of salinity does not influence much on circulation in wintertime. Then, three numerical experiments are designed, in the first one only the Yellow River flux is considered, in the second one only the vapor flux is considered, and in the last one only the water exchange with the Yellow Sea is considered. The results show: the vapor flux contributes most to interannual variation of salinity, and the water exchange with the Yellow Sea has some influence on it too, but the Yellow River does little to it.To sum up the above works, there are some innovative points in this paper. Firstly, through the analysis of data, propose that the long-term increase of salinity and temperature not only exist in the coastal sea but also on the PN section for the first time. Secondly, successfully simulate the formation of the salinity of the Bohai Sea in 1980's. Take the Yellow River flux, vapor flux, and water exchange with the Yellow Sea together into consideration, to analyze contribution of each factor to the interannual variation of salinity. Lastly, preliminarily discuss the change of circulation in the Bohai Sea when the salinity increasse.