The residual salinity and circulation in a numerical ocean model of Tampa Bay is shown to experience significant temporal variation under realistic forcing conditions. A version of ECOM developed for Tampa Bay with 70 by 100 horizontal points and 11 sigma levels is examined for the years 2001-2003. Model output variables are averaged over 30 days to generate residual fields. The residual salinity varies with the freshwater inflow. During this experiment the residual surface salinity in the northern region of Tampa Bay varies from 12 to 33, and the bay mouth varies from 30 to 36. The residual axial current is usually dominated by the buoyancy-driven overturning circulation with a (southwestward) outflow at the surface and to the sides of the shipping channel, and a (northeastward) inflow usually occurring subsurface within or above the shipping channel. The residual circulation varies by nearly a factor of 3 in Middle Tampa Bay over the 3-year simulation and is partially disrupted when the buoyancy driven flow is weak and the surface winds are to the northeast. A scaling argument indicates the relative strength of buoyancy vs. wind goes as Dr H2w-2, where Dr is the head to mouth density difference across the bay, H is the depth, and w is the wind speed. Tampa Bay is usually in the buoyancy dominated regime.
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5/2/2006