- Columbia River Estuary (Or. and Wash.) -- Internal waves,
- Columbia River Estuary (Or. and Wash.) -- Tides -- Analysis
Tidal variations in estuarine stratification are revealed by the depth and thickness of the density interface. The depth of the interface may be predicted using an inviscid two-layer model that combines baroclinic estuarine circulation with barotropic tidal currents [Helfrich, 1995]. Here we present results from a two-layer model modified to include the effects of bottom friction and interfacial mixing. Modeled layer thickness and speed compare favorably with prior analytic studies [Farmer and Armi, 1986; Pratt, 1986]. We use a bulk Richardson number criterion to estimate the thickness of the pycnocline from two-layer model results; the predicted pycnocline depth and thickness compare remarkably well with observations. We also investigate the effects of changing bottom friction and barotropic currents on the pycnocline thickness.