Modeling mixing processes in the Columbia River estuary: A model-data comparison

Columbia River estuary is a macro-tidal estuary, shallow except for two narrow channels through which most of the salt transport takes place. Mixing processes in the two channels are strongly affected by Spring-Neap variations in the tidal range, river discharges (which typically exceed 10,000 m3/s during spring freshets) and coastal winds. The interactions between these forcings controls residual flows inside the estuary, which in turn impacts the extent of salt intrusion into the estuary. Using a new 3D baroclinic circulation model (ELCIRC, [12]), a year long database of numerical simulations has been developed and contrasted against data from a network of in situ instruments which form a part of CORIE. CORIE is a long term coastal-margin observatory system for the Columbia River. In this paper we (a) show that ELCIRC simulations are able to reproduce some but not all key complex interactions observed in the field, (b) study the spatial and temporal variations circulation patterns using a combination of simulations and observations, and (c) use simulations to quantify the role played by each of the forcings (tides, winds, and discharge) on the residual circulation and salinity intrusion patterns.