Subtidal Water Level and Current Variability in a Bar‐built Estuary during Cold Front Season: Barataria Bay, Gulf of Mexico

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.