| 摘要: |
| 利用2015年4、5、6月在长江口外开展综合海洋调查获取的实测数据，分析春季口门外海域长江冲淡水（Changjiang diluted water，CDW）时空分布特征及扩散过程，并结合同期的多源环境观测数据，探讨各环境动力因素对春季长江冲淡水分布的影响，深化对冲淡水在口门外海域扩展及其动态变化的认识。观测结果显示，2015年春季长江冲淡水的扩散范围逐月增大，主体最远可到达123°E以东海域，其逐月变化主要受控于口外水文气象环境。长江径流量大小决定了冲淡水出口门后的分布范围以及表层水盐度，风向则控制冲淡水的扩展态势。在风场与径流的共同作用下，春季口门外海域长江冲淡水的扩散呈现三种模式：4月份的顺岸南下型（冬季型）、5月份的东北转向型（过渡型）和6月份的东南-东北双向分支型（夏季型）。春季台湾暖流深层水已到达长江口外海域，与表层冲淡水层相互作用较弱，但随着上升流的逐月增强，其与上层低盐冲淡水之间的跃层效应愈发显著，一方面抑制长江冲淡水的向下扩展，同时上升流的涌升也减薄了冲淡水的厚度。再悬浮泥沙向上扩散的厚度显示出春季潮混合过程难以影响至表层，但在大潮情况下，水位波动变化更为剧烈，使外海高盐海水向陆上溯更远，导致5月份12250E断面的水体盐度整体相对较高。 |
| 关键词: 长江冲淡水 口门外海域 逐月变化 春季 实地调查 |
| DOI：10.11759/hykx20210107002 |
| 分类号:P736.21;P731.16 |
| 基金项目:中国科学院战略性先导科技专项（XDB42010203，XDA23050503，XDA9060401）；国家自然科学基金面上项目（41476045） |
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| The monthly changes and its influencing factors of the Changjiang Diluted Water off the estuary in spring |
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ZHAO Yu-xi1,2, WANG Zhen-yan1,2,3,4
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1.CAS Key Laboratory of Marine Geology and Environment, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China;2.University of Chinese Academy of Sciences, Beijing 100049, China;3.Laboratory for Marine Mineral Resources, Pilot National Laboratory for Marine Science and Technology(Qingdao), Qingdao 266071, China;4.Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao 266071, China
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| Abstract: |
| Based on the field surveys data off the Changjiang River Estuary in April, May and June 2015, the distribution characteristics and the diffusion process of the Changjiang Diluted Water (CDW) in spring were analyzed, and combined with the same period of multi-source environment observation data, discussing the influence of various environmental dynamic factors of the CDW off the estuary in spring, to improve the understanding of the continuous diffusion and dynamics of CDW. Results show that the expansion range of CDW increased monthly in spring, and its main body can reach the east of 123°E. Its monthly changes were mainly controlled by the hydrodynamic environment outside the estuary. Runoff determined the range of CDW and the surface salinity, and the wind controlled the direction of CDW. Under the joint action of wind and runoff, the diffusion of CDW presented three types:alongshore southward in April (winter type), northeastward in May (transitional type) and northeast-southeast bi-direction in June (summer type). The Taiwan warm current has reached the Changjiang river estuary, and the interaction with the surface water layer is weak. But the upwelling strengthened monthly, the thermocline between TWC and the upper CDW became stronger, which inhibited the downward expansion of CDW, while the upwelling also reduced the thickness of CDW. The thickness of the resuspension showed that tidal mixing could not spread to the surface. During the spring tide, the fluctuation was more violently and the seawater had a farther upstream distance, resulting in an abnormally high salinity in the 12250E section in May. |
| Key words: Changjiang Diluted Water off the Changjiang River Estuary monthly expansion spring field surveys |
