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Modeling Study of Physical Processes over the Inner Shelf of the Georgia Coast


PI: Changsheng Chen (Univ of Massachusetts - Dartmouth, formerly: Dept of Marine Sciences, Univ of Georgia)

Support: Georgia Sea Grant College Program (R/HAB-1-PD, R/HAB-3-PD, R/HAB-3)

Timeframe: 10/1/95 - 2/28/04 (complete)

Project Overview:
The objective of this proposal is to build upon the accomplishments of our current model efforts and to develop a new hydrodynamic, suspended sediment, and water quality model which has the capability of simultaneously simulating both estuary-scale and tidal creek-scale features of the water movement and water quality in Georgia's estuaries. We have developed an unstructured grid, finite-volume, three-dimensional, primitive equation ocean model (called FVCOM) in the last two years. This new model combines the advantages of a finite element method for geometric flexibility and a finite-difference method for the simplest discrete computation. The currents, temperature and salinity in the model are computed following a conservative law, which is essential in the estimation of biological and chemical fluxes over salt-marsh, tidal creeks, and estuarine complex. This model has been successfully applied to the Satilla River, an estuary characterized by numerous tidal creeks, barrier islands, and inlets. The application of this new finite-volume model to Georgia estuaries has provided us with a very efficient scientific tool that can assist them in evaluating water quality in Georgia's estuaries.

Progress and Findings :

The new unstructured grid finite-volume model (FVCOM) has provided the coastal and estuarine community a unique model tool that is capable to simulate the circulation, transport, temperature and salinity as well as water quality variables in the estuarine-tidal creek-intertidal salt marsh complex. This tool also provides managers with a scientific tool for making decisions concerning efficient utilization of marine resources in Georgia estuaries. An operational model system of the Satilla River Estuary has been built on the frame of FVCOM, which has provided the State of Georgia a scientific monitoring tool for coastal protection and management.

  • The model has successfully simulated the amplitude and phase of the semidiurnal tide and fortnightly and monthly variations of tidal currents and sea level. The model results have shown that tides propagate towards the coast from the open ocean and turn clockwise when they reach the inner shelf. The amplitude of the M2 tide has its maximum of about 100 cm near the center of the Georgia coast and decreases offshore and toward both south and north ends of the shelf. Similar structures also were found for S2 and N2 tidal components.
  • Our model has simulated the formation of the low-salinity front in the inner shelf of the SAB. Modeling experiments showed a significant intensification of the buoyancy-driven southward flow in the inner shelf by tidal mixing. When an upwelling-favorable wind was impacted at the surface, a wave-like shape of salinity contours developed at the edge of the front in the mid-shelf where the tide was strongest. The low-salinity water at the crest can be "detached" from the front as a result of water replacement from the trough by combined upwelling and along-shelf northward advection. This detachment process may wash out the zoeae and postlarval from their nursery ground and directly influence their survival rate.
  • The current model has been modified to a non-orthogonal coordinate grid model, which has a much better fitting of the coastline and is more efficient for tidal simulation over the inner shelf of Georgia coast.
  • We have developed an ecosystem model for the inner shelf of the South Atlantic Bight. This biological model will be coupled into our physical model after the Gulf Stream is successfully included into the computational domain.

All model results have been compiled into 2D or 3D animation movies, which can be directly viewed from our research group web site: http://codfish.smast.umassd.edu/.

Publications:
Zheng, L. C. Chen, and F. Zhang, 2004. Development of water quality model in the Satilla River estuary, Georgia. Ecological Modeling, in press.

Zheng, L., C. Chen, and H. Liu, 2003. A modeling study of the Satilla River Estuary, Georgia. I: Flooding-drying process and water exchange over the salt marsh-estuary-shelf complex. Estuaries, 26, 651-669.

Chen, C, H. Liu, and R. C. Beardsley, 2003. An unstructured grid, finite-volume, three-dimensional, primitive equation ocean model: application to coastal ocean and estuaries. J. Atmos. Ocean. Technol., 20, 159-186.

Chen, C., J. Zhu, R. C. Beardsley, and P. S. Franks, 2003. Physical-Biological Sources for the Dense Algal Bloom over the Western Shelf of the East China Sea, Geophysical Research Letter, 30(10), 1515, 22-1:4.

Chen, C., 2000. A modeling study of episodic cross-frontal water transports over the inner shelf of the South Atlantic Bight. Journal of Physical Oceanography, 30, 1722-1742.

Chen, C., L. Zheng, and J. Blanton, 1999. Physical processes controlling the formation, evolution, and perturbation of the low-salinity front in the inner shelf off the Southeastern U.S.: A modeling study. Journal of Geophysical Research, 104, 1259-1288.

Visual Models:
(1) 3-D Animation movies of tidal simulation;
(2) Formation of the low-salinity front;
(3) Wind-induced offshore detachment of the low-salinity water;
(4) Lagrangian trajectories of fluid particles over the inner shelf of the South Atlantic Bight.

Modeling Page:
http://codfish.smast.umassd.edu/

Related Project:
Development of A Finite-Volume Ecosystem Model for Georgia Estuaries: A New Scientific Tool for the Coastal Environmental Management


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This page was updated October 13, 2006