Collaborative Research: Tidally rectified flows in multiple inlet/lagoon systems: Consequences for transport and residence times

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Shallow, bathymetrically-complex lagoon systems comprise a significant fraction of the world’s coastlines, including those of the United States. These systems are highly impacted by human activity, yet are vitally important regions for commercial and recreational fisheries, inland water transportation, buffering coastal communities from storms, and are home to sensitive coastal benthic and marsh ecosystems. This project would study lagoon systems with multiple inlets, using idealized and realistic numerical modeling studies combined with field observations. The work would focus on Barnegat Bay and adjacent lagoons in NJ to test the hypothesis that tidally-driven residual motions at inlets are the dominant mechanism controlling circulation, residence time and, consequently water quality of lagoons. Residence time, water quality and overall ecological health of lagoons are highly sensitive to net transport at lagoon inlets and are likely sensitive to inlet modification. The study would seek to characterize this sensitivity and provide a dynamical framework for understanding its ecological and societal implications. The project includes support for the professional development of two graduate students and will provide research opportunities and experiential STEM education for undergraduate students. Outreach presentations will be given to organizations, marine extension and public programs concerned with lagoon conservation. The project will use idealized and realistic modeling with ROMS, combined with observations to quantify both Stokes and Eulerian transport, which sum to the Lagrangian transport through the multiple inlets in the representative Barnegat Bay, NJ system. While the most detailed estimates of these transport quantities will be obtained from model output, estimates from observational data will provide key insights into the modulation of these terms by tidal amplitude, variability of subtidal sea level, and tidal period processes such as channel/shoal exchange and trapping. Three main hypotheses will be addressed: H1. Mean circulation and net transport at connections between the lagoon and the coastal ocean (inlets) are dominated by tidally-rectified flows. H2. The presence of multiple inlets significantly influences net transport between the lagoon and the coastal ocean as well as the circulation and residence time within the lagoon. H3. Buoyancy inputs and storms modify tidal rectification (and thus net transport) at inlets.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.