Interannual and long-term hydrographic changes in the Yellow Sea during 1977–1998

Interannual and long-term changes in water temperature and salinity (T-S) in the Yellow Sea were examined using seasonal observations made during 1977–1998. The winter and summer seasons are distinctly different in their stratification conditions. In winter the water column is well mixed and the dominant feature of the T-S distribution is the warm and saline Yellow Sea Warm Water occupying the deep region. The winter water temperature has interannual variations, a long-term warming trend, and distinct cold and warm phases before and after 1986. Changes in the winter water temperature are driven by the lateral heat input associated with the intrusion by the Yellow Sea Warm Current. Changes in winter sea-surface salinity correspond to changes in the rate of surface evaporation. In summer the water column is strongly stratified. Interannual changes in surface temperature are caused by changes in surface heat flux, while surface salinity changes correlate well with the changes in precipitation. The summer surface temperature (salinity) tends to be low (high) in El Niño years and increases (decreases) in the year after El Niño. In summer, changes in the bottom temperature and salinity are not coherent over the whole region. In the deep region, the summer bottom T-S represent a property of the Yellow Sea Cold Water, and their interannual changes correspond to T-S changes in the Yellow Sea Warm Water in winter.