우리나라 주변해역의 양자강 저염수에 대한 연구

Abstract

The purpose of this thesis is to understand the distribution of Changjiang Diluted Water (hereafter CDW) around Korean Peninsula by analyzing the KODC(Korea Oceanographic Data Center) data during 1995 to 2007 for CDW distribution and calculating the numerical model with ROMS for the analysis of tidal effect to CDW movement and the reproduction of CDW distribution. The long-term effect of the Three Gorge Dam is also calculated. During 1995-2007, sea surface salinity off the west coast of Jeju Island has been increasing while the amount of Changjiang River discharge has been decreasing. However, CDW distributes very diversely around the Korea Peninsula. It tells us that the process of CDW movement is not simple. The main directions of CDW movement are to the Korea strait (2005), to the north along the west coast (2006), and to the south of Jeju Island (2007). It seems to be critically influenced by wind. The salinity distributions of 2005 to 2007 are reproduced for these 3 directions. The tidal effects on CDW movement and distribution are two ways. One is to diffuse CDW vertically and horizontally so that CDW distribution expands vertically and horizontally. The horizontal expansion of CDW distribution occurs near the coast. However, the total area of horizontal CDW distribution reduces because of strong vertical diffusion. The other is to increase the barotropic component of current so that the current closely aligns with the isobath. By this effect, the CDW distributes basically to the southeast off the river mouth along the isobath of bank. Including climatological temperature and salinity, daily wind, Changjiang River discharge and tide, the model reproduces well the salinity distributions in 2005-2007. In 2005, CDW moves to the Korea strait as usual. In 2006, CDW moves toward the Yellow Sea and also the south coast of Korea. According to the model calculation, the former is driven by wind and the latter is driven by tide, of which effect pushes CDW to the southeast. In 2007, CDW moves toward the south of Jeju Island by wind. The model reproduction represents the influences of current, wind, tide, and river discharge well. The effect of the Three Gorge Dam is not recognized in observed salinity around the Korea. The model calculation shows that the reduced river discharge by the Three Gorge Dam results in the increments of 3 psu near the Changjiang River mouth and 0.2 psu near Jeju Island in a short period. However, the salinity increment may be accumulated in a long period.