Annual Cycle of Stratification and Tidal Fronts in the Bohai Sea: A Model Study

Copyright©The Oceanographic Society of Japan/TERRAPUB/Springer observed between sufficiently mixed regions and highly stratified regions (Simpson and Hunter, 1974; Bowers and Simpson, 1987; Zhao et al., 2001), which are generally characterized by sharp horizontal salinity or temperature gradients and are able to block the free exchange of materials effectively. Therefore, a better understanding of the evolution of stratification and the position of tidal fronts is needed for a thorough knowledge of ecosystem dynamics as well as pollutant transportation in shelf seas. The Bohai Sea (BS) is a semi-enclosed shelf sea with a mean depth of about 18 m (Fig. 1). Hydrodynamics in the BS have been intensively studied in past decades (Fang and Yang, 1985; Zhao and Shi, 1993; Huang et al., 1996, 1999; Wei et al., 2004; Liu et al., 2005). However, little attention has been paid to the evolution of its stratification. Huang et al. (1996, 1999) have given a brief analysis based on the simulated seasonal variation of the temperature profiles along two cross sections. Using the stratification model formulated by Simpson and Hunter (1974), Zhao et al. (2001) have presented a detailed description of tidal fronts in the BS under weak wind conditions. These studies are substantive, but do not reveal the comprehensive temporal and spatial variation of stratification in the BS. This paper attempts to discuss this problem by means of the simulated SST and SBT. In addition, by computing the Loder parameter (1986), this paper further examines the tidal fronts in the BS during summer months, which are characterized by weak wind mixing (Zhao et al., 2001). Annual Cycle of Stratification and Tidal Fronts in the Bohai Sea: A Model Study