Reverse Estuarine Circulation Due to Local and Remote Wind Forcing, Enhanced by the Presence of Along-Coast Estuaries: REVERSE ESTUARINE CIRCULATION DRIVERS
Reverse Estuarine Circulation Due to Local and Remote Wind Forcing, Enhanced by the Presence of Along-Coast Estuaries: REVERSE ESTUARINE CIRCULATION DRIVERS
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DOI：
10.1002/2016jc012479
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发表时间：
2017-12
影响因子：
--
通讯作者：
S. Giddings;P. MacCready
中科院分区：
文献类型：
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作者：
S. Giddings;P. MacCready
河口交换流控制着海洋和河口之间的相互作用，因此在海洋地球化学过程中起着重要作用。本研究调查河口交换流的变化，由于离岸海洋条件，包括上升流/下降流，和离岸（从邻近的河口）的河流羽流的存在。我们通过数值模拟在萨利希海，在东北太平洋的一个大型河口系统的口解决这些过程。对总交换流量的分析表明，在上升流季节，交换流量的大小是相当一致的，并在一个积极的方向（进入河口的深度和表面）。然而，在有利的下行风期间，交换气流显示出明显更多的变化，包括多次逆转，与观测结果一致，以及起源于南部250公里的哥伦比亚河羽流的表面侵入。数值计算的沿海峡动量收支结果表明，气压梯度，特别是斜压梯度对交换流的强迫作用占主导地位。压力梯度受科里奥利和有时平流的艾德，突出了地转和局部调整的重要性。在没有近海河流羽流的情况下进行的实验中，逆转仍然发生，但较弱，斜压压力梯度起着减少的作用。这些结果表明，河口沿着强上升流的海岸线应经历显着的调制在上升流与下降流条件下的交换流。此外，他们强调了附近河口相互影响的重要性，不仅在连通性方面，而且还改变了交换流程。影响，威胁其重要功能。了解河口动力学是了解河口生态系统的关键。河口和沿海海洋之间的水动力连通性是影响关键生物和地球化学过程的关键动力驱动因素，如海洋/河口营养盐和浮游植物交换以及河口停留时间、溶解氧和酸化水平的调节。典型的河口-海洋交换将海洋水带入河口深处，在河口内向上混合，并将海洋和河流水的混合物从表面返回海洋。这份手稿记录了这种典型环流模式的季节性逆转以及逆转的水动力驱动因素。它强调了离岸风和与邻近河口连通的重要性。对这些机制的进一步理解可以帮助我们预测河口将如何应对气候变化。
Estuarine exchange flow governs the interaction between oceans and estuaries and thus plays a large role in their biogeochemical processes. This study investigates the variability in estuarine exchange flow due to offshore oceanic conditions including upwelling/downwelling, and the presence of a river plume offshore (from a neighboring estuary). We address these processes via numerical simulations at the mouth of the Salish Sea, a large estuarine system in the Northeast Pacific. An analysis of the Total Exchange Flow indicates that during the upwelling season, the exchange flow is fairly consistent in magnitude and oriented in a positive (into the estuary at depth and out at the surface) direction. However, during periods of downwelling favorable winds, the exchange flow shows significantly more variability including multiple reversals, consistent with observations, and surface intrusions of the Columbia River plume which originates 250 km to the south. Numerical along-strait momentum budgets show that the exchange flow is forced dominantly by the pressure gradients, particularly the baroclinic. The pressure gradient is modified by Coriolis and sometimes advection, highlighting the importance of geostrophy and local adjustments. In experiments conducted without the offshore river plume, reversals still occur but are weaker, and the baroclinic pressure gradient plays a reduced role. These results suggest that estuaries along strong upwelling coastlines should experience significant modulation in the exchange flow during upwelling versus downwelling conditions. Additionally, they highlight the importance of nearby estuaries impacting one-another, not only in terms of connectivity, but also altering the exchange flow. impacted, threatening their important functionality. Understanding estuarine dynamics is critical to understanding estuarine ecosystems. Hydrodynamic connectivity between estuaries and the coastal ocean is a key dynamical driver impacting critical biological and biogeochemical processes such as ocean/estuarine nutrient and phytoplankton exchange and regulation of estuarine residence time, dissolved oxygen, and acidification levels. Typically estuarine-ocean exchange brings oceanic water into the estuary at depth, mixes it upwards within the estuary, and returns an outflowing mixture of oceanic and riverine water at the surface to the ocean. This manuscript documents seasonal reversals to this typical circulation pattern and the hydrodynamic drivers of the reversals. It highlights the importance of offshore winds and connectivity with neighboring estuaries. Improved understanding of these mechanisms can help us predict how estuaries will respond to a changing climate.