The Study Of Yellow Sea Warm Current, Yellow Sea Cold Water Mass And Their Evolution Process In Spring

The Yellow Sea is an important continent shelf region connected Bohai Sea and open sea. The coastal economy, coastal culture, fishery, military activities in this region is very heavy, thus, the research focus on the typical marine phenomenon is very helpful to reveal the hydrological character, and is very important to guard the economy construction, fishery, and military activities safety. Through the temperature, salinity and current data collected in the recent decades, the study of the typical marine phenomenon was made to reveal the basic characteristics and the mechanism of the formation, development and extinction, which include the Yellow Sea warm current and Yellow Sea cold water mass and their transition in spring.1. The direct evidence and cause of the Yellow Sea warm current in spring.In winter time, the tough of the Yellow Sea warm current from the southwest region of the Cheju island flow northward along the west of the Yellow Sea trough. In November, the front of it reached 35 °N, and the average speed is 5-8cm/s in the axis. The temperature raised about 4°C in the bottom layer at the warm current path. At 34°N,122°E, one branch of the warm current tough is separated and flow to the Qingdao offshore. The winter monsoon cause the water loss in the coastal region in the north Yellow Sea(Bohai Sea included), then the water flow southward along the west coastal and force the Lubei coastal current and the Subei coastal current. Then, the seasonal altitude difference in Yellow Sea region was founded, and the stable Yellow Sea warm current was forced. In the other side, the weather time scale Yellow Sea warm current also exist to compensated the difference. In spring, the front of the Yellow Sea warm current still can reach 37 °N, but lose of the support of the high temperature and salinity Tsushima warm current in Cheju southwestern region, the temperature and salinity decreased clearly(about 2 °C and 1.0)in the root of the warm tough. At the same time, decrease is very slow in the front of the warm tough, then the warm tough turned into the almost closed high temperature and salinity water mass. Although the compensation function of the Yellow Sea warm current was disappeared, but the different in the SSH in winter need to recovery, thus the water in the south Yellow Sea should flow northward, then the high temperature and salinity water keep move to the north. In this progress, the temperature of Yellow Sea warm current decreased very clearly, while the salinity very slowly, but with movement to the north, the temperature and salinity raised in its path. There is an interannual variability in the distinction of the Yellow Sea warm current. And it will disappeared within May to July. Because the space scale is very small, the northwest branch of the Yellow Sea warm current is disappeared before April, and only the high salinity tough was left.2. The characteristics and formation of the middle layer cold water in the southeast region of ShidaoThe middle layer cold water appeared near the 50 m isobaths at the southeast region of Shidao in spring. The cold water block exist between 10 m and 30 m layer, and it is 100 km wide in the latitude direction. The temperature in center is 2 °C lower than the around, 1.5 °C lower than the surface, and 1.0 °C lower than the bottom. The formation of it is the interaction of the Yellow Sea warm current water, the coastal cold water and the temperature rising in the surface in spring. The low salinity cold water flows northward from the Chengshantou, and meet the warmer surface water and high salinity Yellow Sea warm current bottom water, because the density of them, the cold water insert the other two water, and form the low temperature and salinity middle layer water.3. The formation of the Yellow Sea cold water mass in summerThe Yellow Sea cold water mass is mainly formed by the residual water in winter time, but weak water exchange happen inside. In spring, the cold water flow southward from Chenshantou, and become the middle layer cold water which is the main part of the Qindao cold water mass. According to the 10 °C isotherm, the Qingdao cold water mass is obviously the part of Yellow Sea cold water mass. In 36 oN section, there are two low temperature center, which in different place by years. The strength of the one near seashore is a little weak and the range is small too. There is no low salinity center in the same place. While the strength of the one in the west of Yellow Sea trough is strong and the range is big, correspondingly, there is a low salinity center in the same place. While in 35 °N section, there is only one low temperature center, and low salinity center appears correspondingly. There are two strong cold centers in the Yellow Sea cold water mass, one is the Qingdao cold water mass and the other is Inchon cold water mass. In the middle of the Yellow Sea cold water mass is the residual water of the Yellow Sea warm current water in winter. The strength of the residual Yellow Sea warm water is different in various years. If the high salinity center is the sign of the residual Yellow Sea warm water, it appears almost in the same place around the 70 m isobaths in different years.4. The driving mechanism of the Yellow Sea warm current and the Yellow Sea cold water mass.The obvious differences of the sea level are existing between the southern Yellow Sea and the northern Yellow Sea. In winter time, the sea level in Qingdao is lower than it in the southern Yellow Sea, and this happened early than the sea level reduce in the northern Yellow Sea, thus the northwest branch of the Yellow Sea warm current was forced. In the midwinter, the water losing is the most in the northern Yellow Sea, then the Yellow Sea warm current turns to the northward. In spring, the difference of the sea level quickly disappeared between Qingdao and south Yellow Sea, thus the northwest branch of the Yellow Sea warm current requite and turns to the northward. Although the difference of sea level between the northern Yellow Sea and southern Yellow Sea is become little and little, the weak northward flow still exist in the west of the Yellow Sea trough. In summer, under the southern wind, the sea level of northern Yellow Sea is higher than southern Yellow Sea, and then the southward flow was forced. And the low salinity cold water is carried to the south Yellow Sea cold water mass from the northern Yellow sea, and finally the stable structure of the Yellow Sea cold water mass was formed.