Role of Baroclinic Processes on Flushing Characteristics in a Highly Stratified Estuarine System, Mobile Bay, Alabama
Role of Baroclinic Processes on Flushing Characteristics in a Highly Stratified Estuarine System, Mobile Bay, Alabama
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斜压过程对阿拉巴马州莫比尔湾高度分层河口系统冲刷特征的作用
DOI：
10.1029/2018jc013855
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发表时间：
2018
期刊：
影响因子：
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通讯作者：
B. Yoon
中科院分区：
文献类型：
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作者：
Jiabi Du;Kyeong Park;Jian Shen;B. Dzwonkowski;Xin Yu;B. Yoon
河口的冲刷量化了河口和沿海海洋之间的总体水交换，对水质以及系统内的生物和地球化学过程至关重要。在实际和各种受控强迫条件下，数值计算了移动的海湾的冲刷时间和淡水年龄。它们对外强迫的响应可以用系统内大气环流的三维特征来解释。在第25 - 75百分位河流流量下，冲刷时间为10 - 33天，几乎是以前仅基于正压过程估计的一半，表明斜压过程的重要贡献。它们的影响被量化为“新的海洋流入量”，在低至中等河流流量条件下，与河流流量处于同一量级。斜压影响随流量的增加先增大后减小，与水平密度梯度的响应一致。斜压过程主要通过密度驱动的环流增加海洋净流入量，有助于减少冲刷时间。干湿季差异较大的三维环流解释了冲刷特征的时空变化。风强迫影响系统的三维环流，东风和北风倾向于减少冲洗时间，而南风和西风则相反。
Flushing of an estuary quantifies the overall water exchange between the estuary and coastal ocean and is crucially important for water quality as well as biological and geochemical processes within the system. Flushing times and freshwater age in Mobile Bay were numerically calculated under realistic and various controlled forcing conditions. Their responses to external forcing were explained by the three-dimensional characteristics of general circulation in the system. The flushing time ranges from 10 to 33 days under the 25th–75th percentile river discharges, nearly half of the previous estimates based on barotropic processes only, suggesting the important contribution of baroclinic processes. Their influence, quantified as the “new ocean influx,” is on the same order of the river discharge under low to moderate river discharge conditions. The baroclinic influence increases and then decreases with increasing river discharge, aligning with the response of horizontal density gradient. By enhancing the net influx from the ocean mainly through density-driven circulation, baroclinic processes contribute to reduce flushing times. The three-dimensional circulation, which differs greatly between the wet and dry seasons, explains the temporal and spatial variations of the flushing characteristics. Wind forcing influences the three-dimensional circulation in the system with easterly and northerly winds tending to reduce the flushing time, while southerly and westerly winds the opposite.