长江口洪季水动力对海平面上升的响应特征

考虑到海平面上升对长江口水动力构成的严重威胁,该文基于MIKE21软件建立了长江口二维水动力数学模型,采用实测潮位、流速以及流向资料对模型进行了验证。对相关文献和IPCC报告进行总结归纳,得到2100年海平面保守上升值约为0.5 m。运用验证好的数学模型对海平面上升0.5 m后长江口洪季水动力进行了数值模拟。计算结果表明:海平面上升后,涨潮时间增长,落潮时间缩短;海平面上升0.5 m后,长江口南北支、南北港以及南北槽高潮位增加了0.43 m–0.46 m,高潮位增幅沿程向上减小,北支上段涨潮动力受阻较明显(潮位增幅较大);海平面上升0.5 m后,北支流速增幅比南支大,北支上段落潮流量增幅达82.8%,对北支水道的发展有利。总体而言,海平面上升对目前长江口沿岸的标准构成了一定威胁,但对已经衰退的北支水道有利。

Hydrodynamic responses in the flood season to sea level rise in the Yangtze Estuary

Considering the serious threat of sea level rise (SLR) on the hydrodynamics in the Yangtze Estuary,a hydrodynamic numerical model in the Yangtze Estuary was established using MIKE21.The measured tidal level,flow velocity and direction were applied to verify this model.Based on the relative references and IPCC report,the conservative estimated value of SLR will attain to 0.5 m by 2100.The verified model was then used to simulate the hydrodynamic changes in the flood season in the Yangtze Estuary due to 0.5 m SLR.The computed results show that:the flood duration is lengthened and the ebb duration is shortened after SLR.The high tidal level increases 0.43-0.46 m in the North and South Branchs,the North and South Channels and the North and South Passages after 0.5 m SLR.The amplification of high tidal level decreases upward the channel and the flood tidal force in the upper reach of the North Branch is blocked obviously (with the great amplification of high tidal level).The amplification of flow velocity in the North Branch is greater than that in the South Branch and the increasing ratio of ebb discharge in the upper reach of the North Branch reaches to 82.8％ after 0.5 m SLR,which is benefit to the development of the North Branch.In general,SLR will threaten the current seawalls in the Yangtze Estuary,however,it will mitigate the declining of North Branch.