The Study On Interannual Variability Of Yellow Sea Cold Water Mass

The interannual variability of the Yellow Sea Cold Water Mass is analysed based on the datasets of the China national standard section and Korea Oceanographic Data Center.The factors affecting the interannual variability of Yellow Sea Cold Water Mass are also studied. The dynamic effects of winter monsoon to the temperature of YSCWM are studied by using the sensitivity experiments. The main results showed that:(1)The temperature and the northern front of Northern Yellow Sea Cold Water Mass both have obvious interannual variation characteristics. The lowest temperature of the Northern Yellow Sea Cold Water Mass has a warming trend, and the northern front exist a weakening trend. The sea temperature, air temperature, meridional wind speed and radiation flux in winter has certain influence on the temperature of the NYSCWM. The influence of interannual variation of East Asian winter monsoon is a main mechanism of the interannual temperature variability of the northern Yellow Sea Cold Water Mass. By the interaction with East Asian winter monsoon, ENSO associated with northern Yellow Sea Cold Water Mass.(2)The mean salinity of the NYSCWM center has a slightly decreasing trend. The salinity front and the halocline of the NYSCWM display a weakening trend, which showed that the difference between the NYSCWM and the coastal water decreased. The Yellow Sea Warm Current intrusion, the E-P flux in winter, and the strength of the winter monsoon will affect the NYSCWM salinity.(3)The mean temperature of two centers of the SYSCWM had different long-term trends. The west center’s temperature of the SYSCWM was rising, while the east center’s temperature was falling. The mean temperature of the west center of the SYSCWM was related to the intrusion of the Yellow Sea Warm Current, the meridional wind speed and the air temperature in winter. Summer process played a primary role in the cooling trend of the east center’s temperature.The weakened warm water intrusion into the east center of SYSCWM in summer and stronger thermocline inhibits the horizontal and vertical heat transport, relatively. They commonly made the decreasing trend of the temperature. The weaker warm water intrusion might be caused by the weakened circulation of the SYSCWM. The higher surface temperature and less heat input in the deep layers intensified the thermocline of the east half of the SYSCWM.(4)The mean salinity of the center of the SYSCWM had a decreasing long-term trend. The mean salinity of the center of the SYSCWM was related to the saline water intrusion of the Yellow Sea Warm Current, the salinity of the source area of the YSWC, the evaporation minus precipitation(E-P) flux, and the discharge of the Changjiang River. The decreasing salinity trend to the southwest of Cheju Island led to the freshening trend in the YSWC, which caused the salinity of the SYSCWM to decrease. The freshening trends of the water from the northwest Pacific and Taiwan Strait could be seen as the reason for the decreasing salinity trend of the intrusion of water into the YS. The freshwater flux influenced the surface salinity and was brought to the deep layers by the circulation and the strong mixing in winter. The mean E-P flux signal and Changjiang River discharge signal lagged the first principal component of the SYSCWM for approximately 6 months.(5)Under the situation of the strong(weak) winter monsoon, big(small) sea surface height difference between the southern area and northern area of the YS drives strong(weak) YSWC. The strong(weak) YSWC makes high(low) temperature of the northern YS and the east area of the southern YS which will make higher(lower) temperature of NYSCWM and the east center of the SYSCWM. In the meantime, strong(weak) winter monsoon drives strong(weak) coastal current which makes the temperature of the west area of southern YS decrease. Then the west center of the SYSCWM temperature will decrease(increase).