长江口M_(2)内潮生成、传播和耗散的机制研究及其季节性特征  

STUDY ON THE MECHANISMS OF M_(2) INTERNAL TIDAL GENERATION,PROPAGATION,AND DISSIPATION IN THE CHANGJIANG

作　　者：蓝鑫 张凡[1] 汪亚平 LAN Xin;ZHANG Fan;WANG Ya-Ping(State Key Laboratory of Estuarine and Coastal Research,East China Normal University,Shanghai 200241,China)

机构地区：[1]华东师范大学河口海岸学国家重点实验室,上海200241

出　　处：《海洋与湖沼》2024年第4期853-863,共11页Oceanologia Et Limnologia Sinica

基　　金：国家自然科学基金,U2240220号,42006151号;上海市科学技术委员会面上项目,23ZR1420300号。

摘　　要：河口海域,冲淡水可造成强烈的水体层化,而潮流在层化海水中经过复杂地形时可形成活跃的内潮;内潮引起的输运与混合可对河口海域的物质交换造成重要影响,然而过去对该海域内潮的形成演变机制鲜有研究。为了研究河口海域内潮的形成演变机制,利用高分辨率数值模型深入探讨了长江口及其邻近海域M_(2)内潮的时空特征。结果表明,在20 m等深线、岛屿周边以及水下河谷等区域,正压潮强迫力尤为显著,正压至斜压的能量转换率高,斜压动能强。能量收支分析表明,M_(2)内潮动能主要从近岸区域向外传播,当能量传播至20 m等深线或岛屿周边地形陡峭区域时会发生显著的能量耗散。此外,M_(2)内潮呈现出显著的季节性变化,总体看来斜压动能在夏季最高,秋季在舟山群岛附近较强,而冬季则变得非常微弱,这种季节性变化与长江口海域的季节性层化紧密相关。长江口内潮的时空变化特征可对该海域物质的输运与混合有重要的影响,研究结果可为理解该海域的生态、沉积等过程提供理论依据。Near estuaries,river plume can result in strong stratification in the coastal ocean;and the tide-topography interaction in the highly stratified ocean can generate active internal tides.The transport and mixing induced by the internal tide have a significant impact on the material exchange in estuarine areas.However,research on the formation and evolution mechanisms of internal tides in estuarine areas remains limited at the present.To investigate the formation and evolution mechanisms of the internal tide in estuarine areas,the spatiotemporal characteristics of the M_(2) internal tide in the Changjiang(Yangtze)River estuary and its adjacent seas were intensively examined using a high-resolution numerical model.The results show that the barotropic tidal forcing is particularly significant in the areas including the 20-m isobath,around islands,and in submerged shelf valleys.The conversion rate from barotropic to baroclinic energy is high,resulting in strong baroclinic kinetic energy.Energy budget analysis reveals that the M_(2) internal tide kinetic energy propagates mainly outward from nearshore regions,and dissipated significantly when energy encounters abrupt topographic features such as the 20-m isobath or areas around islands.Additionally,the M_(2) internal tide exhibits significant seasonal variations.In general,the baroclinic kinetic energy is the highest in summer,stronger near the Zhoushan Archipelago in autumn,and becomes very weak in winter.The seasonal variations are closely related to the seasonal stratification in the estuary area.The spatiotemporal variation of internal tides in the estuary plays a crucial role in the transport of materials and mixing in local area.The research findings can provide a theoretical basis for understanding the ecological,sedimentary,and other processes in this area.

关 键 词：长江口 M_(2)内潮 季节性变化 混合 

分 类 号：P731[天文地球—海洋科学]