Impacts of tropical cyclones on wave and current regime in a shallow, microtidal bay

Abstract

In shallow, microtidal coastal regions storms play a significant role in influencing wave climate and circulation patterns. In the northern Gulf of Mexico, understanding the effects of tropical cyclones on hydrodynamic processes is crucial for making predictions in the face of rapid wetland loss and increasing human interventions via restoration and protection strategies, such as river diversions. In this study, two bottom-mounted upward-facing Acoustic Current Doppler Profilers and separate wave recorders were installed in Barataria Bay (Louisiana, USA) to measure waves and current velocities responding to the passage of multiple tropical cyclones in fall 2020 and summer 2021. Analyses of depth-averaged current velocities suggest diurnal astronomic constituents drive currents over a 6-8 day period during and after storms, despite the microtidal nature of the bay. Wind-driven flow reversals of subtidal surface currents were observed during surge events. Storms that made landfall to the west of the bay resulted in enhanced subtidal current velocity magnitude during pre-and post-landfall periods while the one storm that made landfall to the east of the bay showed substantially less subtidal current response. Wave heights during storms are well reproduced by a semi-empirical model based on wind speed, fetch, and water depth, indicating that waves are locally generated. Tropical cyclones significantly influenced sub-tidal current velocities, depending on storm track and time of impact relative to the tidal cycle.