Department of Oceanography, National Sun Yat-Sen University, Kaohsiung, Taiwan ROC.
Marine Science and Information Research Center, National Academy of Marine Research, Kaohsiung, Taiwan ROC.
Sci Rep. 2021 Jan 13;11(1):999. doi: 10.1038/s41598-020-80215-2.
Fundamentally, river plume dynamics are controlled by the buoyancy due to river effluent and mixing induced by local forcing such as winds and tides. Rarely the influence of far-field internal waves on the river plume dynamics is documented. Our 5-day fix-point measurements and underway acoustic profiling identified hydrodynamic processes on the dispersal pathway of the Pearl River plume. The river plume dispersal was driven by the SW monsoon winds that induced the intrusion of cold water near the bottom. The river effluent occupied the surface water, creating strong stratification and showing on-offshore variability due to tidal fluctuations. However, intermittent disruptions weakened stratification due to wind mixing and perturbations by nonlinear internal waves (NIWs) from the northern South China Sea (NSCS). During events of NIW encounter, significant drawdowns of the river plume up to 20 m occurred. The EOF deciphers and ranks the contributions of abovementioned processes: (1) the stratification/mixing coupled by wind-driven plume water and NIWs disruptions (81.7%); (2) the variation caused by tidal modulation (6.9%); and (3) the cold water intrusion induced by summer monsoon winds (5.1%). Our findings further improve the understanding of the Pearl River plume dynamics influenced by the NIWs from the NSCS.
从根本上说，河口水体的动力特性主要由河流排放物产生的浮力和局地风生流、潮汐等动力强迫引起的混合过程所控制。而远场内波对河口水体动力特性的影响则鲜有报道。我们为期 5 天的定点测量和走航式声学剖面测量，确定了珠江河口羽状流输运路径上的水动力过程。在西南季风的作用下，珠江河口羽状流的扩散主要受底层冷水入侵的影响。河水排放占据了表层水体，形成了强烈的分层结构，并由于潮汐波动呈现出沿离岸方向的变化。然而，间歇性的混合过程会打破分层结构，这是由风生流和来自南海北部的非线性内波（NIWs）的混合作用引起的。在遭遇内波事件时，河口水体羽流的明显沉降可达 20 米。EOF 分解并对上述过程的贡献进行了排名：（1）风生羽流和 NIWs 混合过程引起的分层/混合（81.7%）；（2）潮汐调制引起的变化（6.9%）；（3）夏季季风风引起的冷水入侵（5.1%）。我们的研究结果进一步提高了对内波对南海北部河口水体动力特性影响的认识。
