Long-Term Changes in the Characteristics of the Yellow Sea Cold Water Mass in Spring and Autumn from 1996 to 2022

Long-term changes in the physical properties of the Yellow Sea Cold Water Mass (YSCWM) were examined based on observational data collected during the spring and autumn seasons from 1996 to 2022. Recent observations on the physical properties of seawater in the Yellow Sea (YS) in spring and autumn showed that temperature increased and salinity decreased over 2021–2022 compared to 1996. Owing to the variation in the distribution of the physical properties of seawater, the volume of the YSCWM decreased approximately 17% in spring and 50% in autumn during 2021–2022 compared to that in 1996 in the study area. In particular, a clear increase in temperature was observed in the distribution area of the YSCWM, and similar changes in physical properties were observed in both spring and autumn. These changes in the characteristics of the YSCWM are consistent with long-term trend changes in the bottom waters of the YS. In the eastern YS region, the bottom water showed a long-term trend of increasing temperature and decreasing salinity in spring and autumn with similar interannual variability. This temperature variability of the bottom water in the YS was closely related to the variability of the winter Artic Oscillation index.