How winds and river discharge affect circulation in a mesotidal estuary, San Francisco Bay, USA

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Qianqian Liu, Huijie Xue, Fei Chai, Zhengui Wang, Yi Chao, Shivanesh Rao, Hongchun Zhang, Yinglong Zhang


Previous studies suggest importance of wind forcing on salt intrusion length and salt flux in river-dominated microtidal estuaries (with tidal range < 2 m). In this study, we investigate the role of wind forcing on salt intrusion in a mesotidal estuary, San Francisco Bay (SFB), with tidal ranges between 2 m and 4 m, through an open-source model of high transferability, the Semi-implicit Cross-scale Hydroscience Integrated System Model (SCHISM). Meanwhile, we investigate circulation and salinity variation of San Francisco Bay. The model’s performance in hydrodynamics at tidal, spring/neap and seasonal time scales is validated through model-observation comparisons. Through realistically forced and process-oriented experiments, we demonstrate that spring/neap tides can cause fortnightly variations in salinity and currents by modulating vertical mixing and stratification; and seasonal variability of circulation in North Bay is determined by change of river discharge and modified by winds, while in South Bay it is dominated by wind-driven flows. Furthermore, we revealed the role of wind on X2 (the distance from the Golden Gate Bridge to the 2-PSU isohaline at the bottom). The model results show that X2 is primarily influenced by river flow and proportional to river flow to the ¼ power. Meanwhile, wind plays a secondary role in modifying X2 by increasing X2 from 0 to 5 km during low discharge period, while spring/neap tide modulation on X2 is negligible but important for salt balance in sub-regions downstream of X2.



Earth Sciences


Hydrodynamic Modelling, estuarine dynamics, mesotidal estuary, seasonal variability, salt intrusion, wind, San Francisco Bay


Published: 2022-01-14 06:34

Last Updated: 2022-01-14 14:34


CC BY Attribution 4.0 International

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Data Availability (Reason not available):
Field data links are provided in the manuscript. Considering the large size of model dataset, model data are only available upon request.

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