Effects of wave forcing on a subterranean estuary
Effects of wave forcing on a subterranean estuary
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DOI：
10.1029/2010wr009632
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发表时间：
2010-12
影响因子：
5.4
通讯作者：
P. Xin;C. Robinson;Ling Li;D. A. Barry;R. Bakhtyar
中科院分区：
文献类型：
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作者：
P. Xin;C. Robinson;Ling Li;D. A. Barry;R. Bakhtyar
波浪和潮汐是重要的强迫因子，通常在沿海环境中共存。数值研究进行了调查的个人和综合影响，这些力量的流动和混合过程中的近岸地下河口。采用基于浅水方程的水动力学模型，模拟了波浪和潮汐驱动下的动态海平面振荡。振荡的海平面决定了沿海含水层的向海边界条件，在那里模拟了非饱和的变密度流。模拟结果表明，波浪在相位平均海平面（波浪设置）中引起向岸向上倾斜。由此产生的水力梯度产生的孔隙水循环在近岸区的沿海含水层，这导致形成的上部盐羽（USP）类似于由于潮汐形成。然而，在高频波浪振荡下，USP中的再循环海水与底层淡水的混合强度较低。在联合强迫的情况下，波浪引起的环流与潮内流相结合，加强了潮汐期间近岸区的平均循环孔隙水流量。循环流增加了地下河口和海洋之间的交换，贡献了61%的总海底地下水排放的模拟条件相比，40%和49%的比例所造成的相同，但单独的潮汐和波浪强迫，分别。这两股力量的合力还创造了一个更广泛的USP，淡水排放区进一步向海转移。在潮间带的地下河口的淡水流路径进行了修改与相关的过境时间显着增加。波浪和潮汐的相互作用导致排放的新鲜地下水和再循环海水之间的混合增加。这些结果进一步证明了近岸地下水系统的复杂性，并对未来调查排放到海洋之前地下河口中陆源化学品的命运产生影响。
Wave and tide are important forcing factors that typically coexist in coastal environments. A numerical study was conducted to investigate individual and combined effects of these forces on flow and mixing processes in a nearshore subterranean estuary. A hydrodynamic model based on the shallow water equations was used to simulate dynamic sea level oscillations driven by wave and tide. The oscillating sea levels determined the seaward boundary condition of the coastal aquifer, where variably saturated, variable density flow was modeled. The simulation results showed that waves induced an onshore upward tilt in the phase‐averaged sea level (wave setup). The resulting hydraulic gradient generated pore water circulations in the nearshore zone of the coastal aquifer, which led to formation of an upper saline plume (USP) similar to that formed due to tides. However, mixing of recirculating seawater in the USP with underlying fresh groundwater was less intensive under the high‐frequency wave oscillations. In the case of combined forcing, wave‐induced circulations coupled with the intratidal flows strengthened the averaged, circulating pore water flows in the nearshore zone over the tidal period. The circulating flows increased exchange between the subterranean estuary and ocean, contributing 61% of the total submarine groundwater discharge for the simulated condition in comparison with the 40% and 49% proportions caused by the same but separate tidal and wave forcing, respectively. The combined forces also created a more extensive USP with the freshwater discharge zone shifted farther seaward. The freshwater flow paths in the intertidal subterranean estuary were modified with a significant increase in the associated transit times. The interplay of wave and tide led to increased mixing between discharging fresh groundwater and recirculating seawater. These results further demonstrate the complexity of nearshore groundwater systems and have implications for future investigations on the fate of land‐sourced chemicals in the subterranean estuary prior to discharge to the ocean.