长江口盐水入侵对海平面上升的响应特征

Responses of saline water intrusion to sea level rise in the Yangtze Estuary

基于MIKE3软件建立了潮流作用下长江口三维水动力及盐度输运数学模型,采用实测潮位、流速、流向以及盐度资料对模型进行了验证。运用验证好的数学模型对海平面上升后长江口枯季盐水入侵进行了模拟,从而分析海平面上升条件下长江口枯季盐水入侵的响应特征,得出以下结论:海平面上升1 m后,北支上段、南支、南北港以及南北槽的盐度均上升,南支平均盐度均超过0.45 psu,北支中下段的盐度却明显减小;海平面上升后潮汐的作用更强,北支下段底层层化现象减弱,北支径流动力增强,表层层化现象增强,表层Richardson数达150;南槽Richardson数底部减小,表层增大,但垂直结构趋势变化不明显。

A3D numerical model of hydrodynamic and salinity transport of the Yangtze Estuary under the influenceof tide is established based on MIKE3software.This model is validated with the field measured tidal level,flow velocity,flow magnitude and salinity.The validated model is used to simulate the saline water intrusion caused by sea level rise(SLR)in the Yangtze Estuary in the dry season.The responses of saline water intrusion to SLR in the Yangtze Estuary are analyzed.The results indicate that:the salinity in the upper reach of the North Branch,the South Branch,the North Channel,the South Channel,the North Passage and the South Passage obviously increase due to1meter of the SLR,especially when the average salinity of the South Branch entirely exceeds0??45psu,however it decreases significantly in the lower reach of the North Branch.This is induced by the increased flow split ratio of the North Branch due to SLR.The greater flood tidal current and flow split ratio of the North Branch due to SLR make stratification phenomenon of salinity increase with the Richardson number reaching150in the surface layer.For the South Passage,the bottom stratification phenomenon is weakened and the surface stratification phenomenon is enhanced,however the vertical trend is not apparent.