东海内陆架春季跃层和内波影响下的环境要素分布

INFLUENCE OF STRATIFICATION AND INTERNAL WAVES ON DISTRIBUTION OF ENVIRONMENTAL FACTORS OF SEAWATER ON THE EAST CHINA SEA INNER CONTINENTAL SHELF IN SPRING

基于东海内陆架P2连续站春季流速和环境要素的观测数据,发现该站存在由浙闽沿岸水系和陆架混合水系界面形成的较强跃层,跃层的浮频率在1×10-3s-2左右。跃层上下水体的温盐值变化和流场的变化有相关关系。环境要素在跃层的影响下呈现显著的分层结构,说明跃层对环境要素的垂直交换起到了限制作用。同时跃层的存在也为内波的产生提供了条件,斜压结构主要由具有半日潮频率的内潮和近惯性频率的内波组成。在观测开始和结束时刻,跃层深度显著抬升,跃层中存在Ri-1大于4的情况,这与叶绿素溶解氧跨跃层现象存在的时刻对应,说明这两个时刻水体由于内波活动改变了跃层深度并存在剪切不稳定的情况,进而引起了水体的垂向交换,为环境要素的跨跃层混合提供了条件。跃层和内波分别对环境要素的垂直混合起到了阻碍和加强的作用。

Based on the measurements of the velocity and the environmental factors of seawater at the P2 anchor station on the East China Sea inner continental shelf in spring, it was found that strong stratification （with a value of buoyancy frequency of 1 × 10-3 s-2） is caused by the interface between coastal water and shelf mixing water. The variations of temperature and salinity in the water column are related to the flow field. Under the influence of stratification, distribution of environmental factors presents a two-layered structure, above and below the pycnocline. Internal waves consisted of semidiurnal internal tides and near inertial waves are simultaneously generated by the stratification. The time when stratification layer jumps up and Ri-1 〉4 exists in the pycnocline corresponds to that when cross-stratification of chlorophyll and dissolved oxygen takes place. This indicates internal waves provide environmental factors that energize the cross-stratification mixing. Stratification and internal waves work together toward vertical mixing of environmental factors; the former inhibits, and the latter enhances mixing.