Observational characteristics and dynamic mechanism of low-salinity water lens for the offshore detachment of the Changjiang River diluted water in August 2006

• Published in: Acta oceanologica Sinica Vol. 40; no. 3; pp. 34 - 45
• Main Authors: Liu, Zhenyu, Zhang, Wenjing, Xiong, Xuejun, Zhu, Shouxian
• Format: Journal Article
• Language: English
• Published: Beijing The Chinese Society of Oceanography 01.03.2021; Springer Nature B.V; College of Meteorology and Oceanography,National University of Defense Technology,Nanjing 211101,China%First Institute of Oceanography,Ministry of Natural Resources,Qingdao 266061,China%College of Oceanography,Hohai University,Nanjing 211101,China
• Subjects: Baroclinity; Climatology; Dilution; Earth and Environmental Science; Earth Sciences; Ecology; Engineering Fluid Dynamics; Environmental Chemistry; Isobaths; Marine & Freshwater Sciences; Neap tides; Ocean circulation; Oceanography; Offshore; Residual currents; River mouth; River mouths; Rivers; Salinity; Salinity effects; Spring tides; Three dimensional models; Tides; Upwelling; Water; Wind; Wind effects; Winds; Changjiang River; dynamic mechanism; Changjiang River diluted water; observational characteristics; upwelling; numerical simulation; low-salinity water lens; observationalcharacteristics
• ISSN: 0253-505X; 1869-1099
• DOI: 10.1007/s13131-021-1710-9

The Changjiang River diluted water (CDW) spreads into the East China Sea (ECS) primarily in a plume pattern, although in some years, low-salinity water lenses (LSWLs) detach from the main body of the CDW. In-situ observations indicate that in August 2006, a LSWL detached from the main body of the CDW near the river mouth. In this paper, the effects of winds, tides, baroclinity and upwelling on LSWLs are explored with a three-dimensional model. The results show that: (1) winds play a crucial role in these detachment events because wind-induced northerly Eulerian residual currents impose an uneven force on the CDW and cut it off, thus forming a LSWL; (2) upwelling carries high-salinity water from the lower layer to the upper layer, truncating the low-salinity water tongue vertically, which is conducive to the detachment and maintenance of LSWLs; and (3) upwelling during the evolution of a LSWL is caused by the combined effects of winds and tides. The influences of wind-induced upwelling are mainly near the shore, whereas the upwelling along the 30 m isobath is predominantly affected by tides, with the effect increasing from neap tide to spring tide.