Lateral Circulation in a Partially Stratified Tidal Inlet

Linlin Cui,Chunyan Li,Haosheng Huang,Dubravko Justic

doi:10.3390/jmse6040159

Linlin Cui, Chunyan Li + Show 2 more

Open Access

https://doi.org/10.3390/jmse6040159

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Abstract

Using a three-dimensional, hydrostatic, primitive-equation ocean model, this study investigates the dynamics of lateral circulation in a partially stratified tidal inlet, the Barataria Pass in the Gulf of Mexico, over a 25.6 h diurnal tidal cycle. Model performance is assessed against observational data. During flood tide, the lateral circulation exhibits the characteristics similar to those induced by differential advection, i.e., lateral flow consists of two counter-rotating cells and is convergent at the surface. The analysis of momentum balance indicates that, in addition to the pressure gradient and vertical stress divergence, nonlinear advection and horizontal stress divergence are also important contributors. During ebb phase, the lateral circulation is mostly toward the right shoal (when looking into the estuary) for the whole water column and persisting for almost the whole period. The surface divergence suggested by the differential advection mechanism lasts for a very short period, if it ever exists. The main momentum balance across most of the transect during ebb is between the along-channel advection of cross-channel momentum and pressure gradient. The sectional averaged lateral velocity magnitude during ebb is comparable to that during flood, which is different from the idealized numerical experiment result.

Highlights

The lateral circulation in tidally dominant estuaries can be driven by various mechanisms
This flood–ebb asymmetry in the lateral circulation strength was observed by Scully et al [13] in the Hudson River estuary, where stronger lateral flows were observed during flood tides while lateral flows were suppressed during ebb tides
It is connected to the Gulf of Mexico through several tidal inlets including Barataria Pass, which is between two barrier islands, Grand Isle Island and Grand Terre Island (Figure 1b)

Summary

Introduction

The lateral circulation in tidally dominant estuaries can be driven by various mechanisms. In the same idealized numerical experiment, Lerczak and Geyer [2] found that lateral flow is about four times stronger during flood tides than during ebb tides. They attributed it to the interaction between the along-channel tidal currents and nonlinear advective processes over a tidal cycle. This flood–ebb asymmetry in the lateral circulation strength was observed by Scully et al [13] in the Hudson River estuary, where stronger lateral flows were observed during flood tides while lateral flows were suppressed during ebb tides.

Study Area

Model Description and Configuration

Observations

Time Series of Cross-Sectional Salinity and Currents Structures

Driving Mechanism of Lateral Circulation

Flood–Ebb Asymmetry