Estuaries are among the most productive ecosystems on earth. Fundamental to shaping the estuarine ecosystem is the physical circulation that is characterized by a two-layer flow. In recent years theoretical and modeling studies have brought into question the classic model of estuarine exchange that dates back to the seminal work of Pritchard in the 1950's. The emerging paradigm of estuarine dynamics highlights the role played by tidal asymmetries in turbulent mixing, shear, stratification and secondary flows in driving the exchange flow. This recently funded project from the National Science foundation will be the first field effort to quantify the role of secondary circulation in driving the estuarine exchange flow.
We have chosen to use the James River estuary, a tributary of the Chesapeake Bay, for several reasons including the fact that it was the site of Pricthard's observations in the 1950's. The project includes a series of field experiments in the James River estuary, complemented by ROMS (Regional Ocean Modeling System) and LES (Large Eddy Simulations) modeling simulations. Field efforts include extensive moored and shipboard observations and a series of dye-release experiments and microstructure profiling. ROMS modeling will focus on the effects of secondary circulation on the estuarine exchange flows in this wide estuary, while LES modeling will examine the interactions and possible coupling between secondary flows and small scale turbulent flows. This project will advance our understanding of estuarine exchange flows. Estuarine dispersion is largely driven by the exchange flow and the ability to predict dispersion is critical in many applied problems such as determining the Maximum Total Daily Load (TMDL) permissible to an estuarine system More generally, this project will yield much-needed information regarding the circulation and mixing processes in estuaries and help develop state-of-the-art numerical models for simulating estuarine flows, which are required for predicting water quality, contaminant and fish larval transport.
The project is lead by Robert Chant of the Institute of Marine and Coastal Sciences with Co-Pi's Ming Li from the University of Maryland and Arnoldo Valle-Levinson from the University of Florida Gainesville. Field efforts will commence in the spring of 2009 and continue through spring 2010.