PNWTOX simulations

results - ocean/estuarine connectivity


Model results show strong connectivity between both the ocean and estuaries and along-coast estuaries similar to observations. For example, the dominant wind patterns are such that they can actually reverse the Salish Sea estuarine exchange flow during the winter. Additionally, preliminary model results that include passive dye tracers to separate different riverine sources of fresh water, suggest that the Columbia River, at the border of Washington and Oregon, intrudes all the way into the Salish Sea during strong downwelling winds.

Figure 1. Along-coast connectivity in the Pacific NorthWest

This movie shows the strong connectivity between the Columbia River and the Salish Sea. The left panel a) shows the modeled surface salinity field (darker blue is fresher, red is saltier). The middle panel b) shows a passive dye tracer in the Columbia River. This allows us to separate the fresh water coming from the Columbia River versus other rivers in the domain. The upper right panel c) shows the Columbia River passive dye tracer flux through a cross section in the middle of the Juan de Fuca Strait (marked on the left panel). When this value is positive, Columbia River water is entering the Salish Sea. The lower right two panels indicate forcing conditions d) River flow in the Columbia (cyan) and Fraser Rivers (blue) and e) the along-coast 8-day weighted mean winds (black line, Austin & Barth 2002) at the location marked by a star in the left two panels. A red line indicates the time stamp. Downwelling winds lead to a Columbia River plume hugging the Washington coast and entering the Salish Sea during strong downwelling.

exchange flow

The influence on exchange flow can be calculated using the Total Exchange flow method (MacCready 2011). Using this method, along with dye tracers and a model experiment in which the Columbia river is excluded from the simulation, we hope to quantify the impacts of downwelling both with and without an along-shore plume. These experiments will be part of a recently awarded NSF Ocean Sciences postdoctoral fellowship to SN Giddings. Preliminary model results suggest that the presence of an offshore river plume significantly alters exchange flow relative to downwelling oceanic conditions alone.