Using a composite grid approach in a complex coastal domain to estimate estuarine residence time

• Published in: Computers & geosciences Vol. 36; no. 7; pp. 921 - 935
• Main Authors: Warner, John C., Rockwell Geyer, W., Arango, Hernan G.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.07.2010; Elsevier
• Subjects: Brackish; Circulation; Coastal; Composite grid; Dispersions; Earth sciences; Earth, ocean, space; Estuaries; Estuary; Exact sciences and technology; Hudson river estuary; Mathematical analysis; Mathematical models; Neap tides; Position (location); Residence time; ROMS; Springs; Three-dimensional model; United States; Hudson River; Three-dimensional model; Composite grid; Hudson river estuary; Residence time; ROMS; Estuary; springs; exhibits; variability; North America; new methods; estuaries; computers; salt; tracers; data processing; chemically precipitated rocks; evaporites; intrusions; tides; sedimentary rocks; channels; circulation; three-dimensional models; geometry; residence time; dispersion
• ISSN: 0098-3004; 1873-7803
• DOI: 10.1016/j.cageo.2009.11.008

We investigate the processes that influence residence time in a partially mixed estuary using a three-dimensional circulation model. The complex geometry of the study region is not optimal for a structured grid model and so we developed a new method of grid connectivity. This involves a novel approach that allows an unlimited number of individual grids to be combined in an efficient manner to produce a composite grid. We then implemented this new method into the numerical Regional Ocean Modeling System (ROMS) and developed a composite grid of the Hudson River estuary region to investigate the residence time of a passive tracer. Results show that the residence time is a strong function of the time of release (spring vs. neap tide), the along-channel location, and the initial vertical placement. During neap tides there is a maximum in residence time near the bottom of the estuary at the mid-salt intrusion length. During spring tides the residence time is primarily a function of along-channel location and does not exhibit a strong vertical variability. This model study of residence time illustrates the utility of the grid connectivity method for circulation and dispersion studies in regions of complex geometry.