A Numerical Study of the Salinity Structure of a Shallow Bay - Case of Copano Bay, TX
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The Gulf of Mexico has 39 estuaries, in which most of them are characterized as bar-built, shallow bay estuaries. Located at the northwest Gulf of Mexico, the Mission Aransas Estuarine Research Reserve is an area with 750 km^2 with 6 bays. The second largest bay is named Copano Bay, an area with 200 km^2 that has two main river sources, from Mission River and Aransas River, which are the only source of fresh water to the system. The bay is opened at one tidal channel at the south that exchanges salty water with Aransas Bay. As part of the monitoring system for Copano Bay, we used the two stations located at the east and west sides of the bay to understand the temporal variability of salinity in the bay. Because the salinity pattern is not as well defined as the temperature profile, we used a 3D hydrodynamic model (ROMS) to analyze how changes in river discharge, precipitation and winds will affect the bay. After running the simulations for 5 years, from January/2010 to December/2014, we found that the salinity of the bay is controlled by flooding events on the upper bay and by tides on the channel side. During ’wet years’ (2010 and 2015), the salinity is kept in a range between 10 gkg^-1 and 25 gkg^-1. For ’dry years’, where the discharge is low, the salinity was kept in a range of 30 gkg^-1 to 45 gkg^-1, considered hypersaline conditions. The year of 2011, considered a ’transition year’, had the lowest river discharge and precipitation, causing the salinity to increase at a constant rate. By comparing the east and west sides, we saw that the east side is barely influenced by river discharge, responding mostly to the tides, while the west side is mostly influenced by the river discharge. The flooding events are responsible for an increase in vertical and horizontal stratification. A closer look at local events showed the water column took longer to stabilize, after a change in wind due to a storm or front, under hypersaline conditions than under normal years.
Ramos, Arthur Eduardo Amaral (2016). A Numerical Study of the Salinity Structure of a Shallow Bay - Case of Copano Bay, TX. Master's thesis, Texas A & M University. Available electronically from