1. Version 2 ROMS Model for Computation of GEMBOX Exchanges Version 2 model changes:  Open boundary forcing of large-domain model taken from regional model (C. Chen’s FVCOM).  Spatially variable wind forcing from high-resolution atmospheric model (also from Chen).  Two additional rivers (plus WWTF) entering western end of Greenwich Bay. Version 2 model skill improved in comparison to Version 1. Have generated version 2 model dye exchanges for 2006. 2007 run in progress. Computing flushing times for GEMBOX elements.

2. Large-Domain Model Forcing Changes: Low-pass filtered sea level, velocity, temperature, and salinity from FVCOM simulation applied along open boundaries of large- domain model (in addition to tides as in standard run). Spatially variable wind. Fullbay Model Forcing Changes: Addition of river inflows in W. Greenwich Bay. Spatially variable wind. Bay mouth open boundary forcing from new version of large domain model. Open boundaries Blue: “large-domain” model Red: “fullbay” model New Rivers

3. Subtidal Sea Level, Velocity Blue: observations Black: model v1 Red: model v2 Sea Level: Providence Sea Level: Newport Sea Level Difference Velocity: E. Passage Channel

4. Model/Obs. Comparison, Greenwich Bay Version 2Version 1

5. Model Skill, Salinity at DEM Stations SurfaceBottom Version 1a: large-domain model forced with FVCOM results. spatially variable wind forcing.

6. Utility of Dye Exchange Estimates (In Addition to Use for GEMBOX) Hypothesis: Dye exchange fractions can reveal details of physical exchange of materials throughout N. Bay. Long time series of exchange fractions provides information on exchange under a wide range of forcing conditions. Can compute flushing times on a daily basis for individual box model elements (or groups of elements) using exchange fractions. Aim is to develop a statistical description of flushing and exchange processes.

7. Element Flushing Times: Salt or Freshwater Dye fluxes represent gross (one-way) advective plus diffusive transport. Net salt flux between elements i and j expressed using dye fractions (similar for Freshwater (FW)): Estimate flushing time from salt (FW) mass within an element and salt (FW) flux into or out of that element: for j where flux_salt i,j < 0 or for j where flux_salt i,j > 0

8. V2 Model: Time Evolution of Flushing Time

9. Version 2 Model: Median Flushing Times Upper Layer ElementsLower Layer Elements

10. What Causes Variability of Flushing Time? Seems to be complex interplay of factors. e.g. river discharge and northward wind: northward southward Box 2, surfaceBox 2, bottom

11. Next Steps Finish dye exchange run for 2007 using version 2 model (within next couple of weeks). Simulation of additional years:  2008, and possibly 2009? Relatively straightforward to obtain forcing data. Simulations will thus be comparable to 2006-2007.  2014? Open boundary and wind forcing data may not be available from the same source. Can explore other options. Upshot may be that simulations will not be easily compared with 2006-2007 because of different model forcing. Papers: 1.ROMS model description/skill assessment. 2.Flushing time and its variability.