Abstract. A 3-D unstructured-grid hydrodynamic model for the
northern Gulf of Mexico was developed, with a hybrid s–z vertical grid and
high-resolution horizontal grid for the main estuarine systems along the
Texas–Louisiana coast. This model, based on the Semi-implicit Cross-scale
Hydroscience Integrated System Model (SCHISM), is driven by the observed
river discharge, reanalysis atmospheric forcing, and open boundary
conditions from global HYCOM output. The model reproduces the temporal
and spatial variation of observed water level, salinity, temperature, and
current velocity in Galveston Bay and on the shelf. The validated model was
applied to examine the remote influence of neighboring large rivers,
specifically the Mississippi–Atchafalaya River (MAR) system, on
salinity, stratification, vertical mixing, and longshore transport along the
Texas coast. Numerical experiments reveal that the MAR discharge could
significantly decrease the salinity and change the stratification and
vertical mixing on the inner Texas shelf. It would take about 25 and 50 d
for the MAR discharge to reach the mouth of Galveston Bay and Port Aransas,
respectively. The influence of the MAR discharge is sensitive to the wind field.
Winter wind constrains the MAR freshwater to form a narrow lower-salinity
band against the shore from the Mississippi Delta all the way to the
southwestern Texas coast, while summer wind reduces the downcoast longshore
transport significantly, weakening the influence of the MAR discharge on
surface salinity along Texas coast. However, summer wind causes a much
stronger stratification on the Texas shelf, leading to a weaker vertical
mixing. The decrease in salinity of up to 10 psu at the mouth of Galveston
Bay due to the MAR discharge results in a decrease in horizontal density
gradient, a decrease in the salt flux, and a weakened estuarine circulation and
estuarine–ocean exchange. We highlight the flexibility of the model and its
capability to simulate not only estuarine dynamics and shelf-wide transport,
but also the interactions between them.
A hydrodynamic model for Galveston Bay and the shelf in the northern Gulf of Mexico
