Circulation Dynamics and Seasonal Variability for the Charlotte Harbor Estuary, Southwest Florida Coast

A hydrodynamic model was developed and validated for the Charlotte Harbor estuarine system, located in SW Florida, to elucidate freshwater fluxes within the system's various inlets during diverse hydrologic conditions. Fresh water entering the system not only varies seasonally but also, because of regulatory fresh water, releases controlling water levels within an upstream lake. The unnatural freshwater releases have been found to negatively affect the system's ecology, in particular within the Caloosahatchee River portion of the system. Neither the flood nor ebb phase exhibits uniform dominance in flushing the system's four major passes. Boca Grande Pass and Big Carlos Pass were mostly ebb dominant, whereas San Carlos Bay was largely flood dominant; neither phase dominated at Captiva Pass. The similarities and/or contradictions of these results in comparison to former field and modeling results are mainly attributed to the differences between the freshwater sources and environmental forces corresponding to each study that forces a different mass-balance condition over the estuary-bay system and, thereby, at each individual inlet. A Lagrangian particle tracking study revealed particles released within the Peace River during different hydrological conditions were comparably transported regardless of freshwater inputs and predominate wind direction. In contrast, particles released within the Caloosahatchee River were flushed into the Gulf of Mexico within 10 days during a usually wet El Nino, dry(November-April) season period whereas during the summer wet (May-October) season released particles remained in the estuary for a longer period (13 days), ultimately resulting in their further transport into Pine Island Sound and Matlacha Pass. The results also demonstrate the effect of freshwater river inputs and wind on the travel time of the neutrally buoyant particles within the estuarine system. The hydrodynamic and coupled particle tracking model serve as the first step in a forthcoming larval transport modeling study.