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The Yellow Sea Cold Water Mass (YSCWM), one of the most vital hydrological features of the Yellow Sea, causes a seasonal thermocline from spring to autumn. The diel vertical migration (DVM) of zooplankton is crucial to structural pelagic communities and food webs, and its patterns can be affected by thermocline depth and strength. Hence, we investigated zooplankton community succession and seasonal changes in zooplankton DVM at a fixed station in the YSCWM. Annual zooplankton community succession was affected by the forming and fading of the YSCWM. A total of 37 mesozooplankton taxa were recorded. The highest and lowest species numbers in autumn and spring were detected. The highest and lowest total densities were observed in autumn (14 464.1 inds./m3) and winter (3 115.4 inds./m3), respectively. The DVM of the dominant species showed obvious seasonal variations. When the YSCWM was weak in spring and autumn, most species (e.g. Paracalanus parvus, Oithona similis, and Acartia bifilosa) stayed above the thermocline and vertically migrated into the upper layer. Calanus sinicus and Aidanosagitta crassa crossed the thermocline and vertically migrated. No species migrated through the stratification in summer, and all of the species were limited above (P. parvus and A. crassa) or below (C. sinicus and Centropages abdominalis) the thermocline. The YSCWM disappeared in winter, and zooplankton species were found throughout the water column. Thus, the existence of thermocline influenced the migration patterns of zooplankton. Cluster analyses showed that the existence of YSCWM resulted in significant differences between zooplankton communities above and below the thermocline. [ABSTRACT FROM AUTHOR]

The vertical mixing parameterization scheme, by providing the effects of some explicitly missed physical processes and more importantly closing the energy budgets, is a critical model component and therefore imposes significant impacts on model performance. The Yellow Sea Cold Water Mass (YSCWM), as the most striking and unique phenomenon in the Yellow Sea during summer, is dramatically affected by vertical mixing process during its each stage and therefore seriously sensitive to the proper choice of parameterization scheme. In this paper, a hindcast of YSCWM in winter of 2006 was implemented by using the Regional Ocean Modeling System (ROMS). Three popular parameterization schemes, including the level 2.5 Mellor-Yamada closure (M-Y 2.5), Generic Length Scale closure (GLS) and K-Profile Parameterization (KPP), were tested and compared with each other by conducting a series of sensitivity model experiments. The influence of different parameterization schemes on modeling the YSCWM was then carefully examined and assessed based on these model experiments. Although reasonable thermal structure and its seasonal variation were well reproduced by all schemes, considerable differences could still be found among all experiments. A warmer and spatially smaller simulation of YSCWM, with very strong thermocline, appeared in M-Y 2.5 experiment, while a spatially larger YSCWM with shallow mixed layer was found in GLS and KPP schemes. Among all the experiments, the discrepancy, indicated by core temperature, appeared since spring, and grew gradually by the end of November. Additional experiments also confirmed that the increase of background diffusivity could effectively weaken the YSCWM, in either strength or coverage. Surface wave, another contributor in upper layer, was found responsible for the shrinkage of YSCWM coverage. The treatment of wave effect as an additional turbulence production term in prognostic equation was shown to be more superior to the strategy of directly increasing diffusivity for a coastal region. [ABSTRACT FROM AUTHOR]

Hydrographic observation and biological samplings were conducted to assess the distribution of phytoplankton community over the sloping shelf of the eastern Yellow Sea in May 2012. The concentration of chlorophyll a was determined and phytoplankton was microscopically examined to conduct quantitative and cluster analyses. A cluster analysis of the phytoplankton species and abundance along four observation lines revealed the three-dimensional structure of the phytoplankton community distribution: the coastal group in the mixed region, the offshore upper layer group preferring stable water column, and the offshore lower layer group. The subsurface maximum of phytoplankton abundance and chlorophyll a concentration appeared as far as 64 km away from the tidal front through the middle layer intrusion. The phytoplankton abundance was high in the shore side of tidal front during the spring tide. The phytoplankton abundance was relatively high at 10-m depth in the mixed region while the concentration of chlorophyll a was high below the depth. The disparity between the profiles of the phytoplankton abundance and the chlorophyll a concentration in the mixed region was related to the depth-dependent species change accompanied by size-fraction of the phytoplankton community. [ABSTRACT FROM AUTHOR]

In order to investigate the environment and acoustic filed change induced by typhoon in shallow sea, we conducted two experiments just before and after the passage of typhoon Damrey, which is the strongest to affect the area north of the Yangtze River since 1949, in the Yellow sea in 2012. The data show that the temperature of the whole water column increases dramatically except the sea surface layer after the passage of Damrey while the salinity decreases obviously. The thermocline deepens and weakens, which leads to a change of internal wave activity. The transmission losses (TL) of the two experiments show that the environment change induced by typhoon can increase the TL as large as 8 dB at a distance of 9.2 km and depth of 15 m. The scintillation index (SI) of the sound intensity is simulated to estimate the change of the effect of internal wave activity on acoustic field showing that the SI decreases to a half after the typhoon's passage. The normal mode structures of the two experiments are also significantly different due to the thermocline changes. In addition, the signal arrives earlier after the typhoon's passage due to the water temperature increase. [ABSTRACT FROM AUTHOR]

Based on observed temperature data since the 1950s, long-term variability of the summer sharp thermocline in the Yellow Sea Cold Water Mass (YSCWM) and East China Sea Cold Eddy (ECSCE) areas is examined. Relationships between the thermocline and atmospheric and oceanic forcing were investigated using multiyear wind, Kuroshio discharge and air temperature data. Results show that: 1) In the YSCWM area, thermocline strength shows about 4-year and 16-year period oscillations. There is high correlation between summer thermocline strength and local atmospheric temperature in summer and the previous winter; 2) In the ECSCE area, interannual oscillation of thermocline strength with about a 4-year period (stronger in El Niño years) is strongly correlated with that of local wind stress. A transition from weak to strong thermocline during the mid 1970s is consistent with a 1976/1977 climate shift and Kuroshio volume transport; 3) Long-term changes of the thermocline in both regions are mainly determined by deep layer water, especially on the decadal timescale. However, surface water can modify the thermocline on an interannual timescale in the YSCWM area. [ABSTRACT FROM AUTHOR]

After a classification of the physical processes which affect the vertical mixing, diffusivity induced by the surface wave momentum and tidal currents and its influence on the vertical temperature structure are discussed. Based on three mixing schemes, the vertical temperature structure of the Yellow end East China Seas (YECS) is simulated. Results show that in summer, the surface wave-induced mixing plays a key role in forming the upper mixed layer in the YECS. The tidal mixing controls the lower layers within 30 m above the bottom, which is the main factor in forming the platform-shaped temperature structure in the southern Yellow Sea (YS). Together with the strong surface wave-induced mixing, the tidal mixing hakes the thermocline ventilate near the east coast of the southern YS. The double cold cores in the deeper layers of the East China Sea have different causes. The western one is the maintenance of the winter cold water, while the eastern one is configured by circulation. The simulated vertical temperature structure of the YECS with the surface wave-induced mixing and tidal mixing has similar features to the observations, which indicates that rinse mixing processes are key factors in simulating the thermocline end pycnocline of the coastal oceans. [ABSTRACT FROM AUTHOR]