| Abstrakt: |
Subtidal water level and current variability in Barataria Bay—a microtidal bar‐built estuary within the Mississippi Delta—and its relation to local and remote wind forcings were analyzed using three different methods: (1) statistical analysis of in situ observations, (2) an analytical model with idealized wind field, and (3) a barotropic numerical model. Remote wind effects (i.e., the coastal water levels imposed by Ekman transport) are dominant at forcing currents at the bay mouth and thus control estuary‐shelf exchanges. In contrast, subtidal water level variability, which ranges from 0.35 m at the bay mouth to 0.55 m at the bay head, is mainly associated with local wind effects, especially at the head of the bay. This occurs because the local wind‐induced water level tilting within the bay is larger than the coastal sea level pumping, i.e., the spatially uniform variations in water levels forced by remote winds. This result contrasts with (1) most coastal plain, fjord, and tectonic estuaries and (2) with other bar‐built estuaries in the region, in which remote wind effects dominate water level variability within the estuary. These differences are due to geomorphological features unique to Barataria Bay, such as its limited estuarine‐shelf connectivity and its orientation relative to local shoreline. Plain Language Summary: Water level and current speed in an estuary can be influenced by atmospheric forcing at periods from days to months. These effects can be the major driver of water level variability in estuaries with a small tidal range, such as those located in the southeast and Gulf Coasts of the United States. Thus, understanding these processes is important to predict a variety of processes, including transport of sediment, nutrients, and biota, as well as flooding of coastal areas. This study attempts to illustrate the relative importance of local and remote winds on subtidal water level and currents behavior in Barataria Bay, an estuary in the northern Gulf of Mexico. Results show that estuarine water level variations are largely affected by the passage of cold fronts over the northcentral Gulf of Mexico. The local and remote wind forcings are of about equal importance in controlling the overall water level variations at the bay mouth, whereas the local forcing is the dominant driver inside the bay. On the other hand, remote wind forcing dominates the subtidal currents at the bay mouth thus controlling the exchange between the estuary and the ocean. Key Points: Subtidal water levels are coherent with along‐estuary wind stress over 3‐ to 10‐day periods, consistent with the passage of cold frontsLocal wind forcing dominates over remote wind forcing at controlling water levels and water level slope within the bayRemote winds are dominant at forcing bay mouth currents and estuary‐shelf exchange [ABSTRACT FROM AUTHOR] |
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