Spatial distribution of tidal currents and quantification of transport timescales in the Salish Sea - Data/Model Synthesis

The tidal currents and tide-induced transport in major basins and sub-basins were studied at a Salish Sea-wide scale using the newly developed high-resolution version of the Salish Sea Model. Potential increase in the ship traffic through the Salish Sea and associated oil spill risk and the community interest in currents hind-cast and forecast information with sufficient accuracy and spatial resolution for use in water quality and ecosystem led to this development. The model performance was evaluated using tides monitoring data from National Oceanic and Atmospheric Administration (NOAA), monthly monitoring temperature and salinity data from 23 Ecology stations. A robust currents skill assessment was also conducted using an extensive Acoustic Doppler Current Profiler (ADCP) data set from 135 stations. In the Salish Sea, tides play a dominant role in the estuarian circulation and basin-wide transport. However, transport time scales such as resident and flushing times and residence times in many major and sub-basins of the Salish Sea have not yet been quantified in a stand-alone manner. A model/data synthesis was performed to examine the spatial distribution of tidal currents for inner Salish Sea regions sub-basins. The results of the analysis are illustrated as tidal-current ellipses diagrams of the dominant harmonic constituent for different regions. As part of this study, we also estimated the resident and flushing times for the main basins and sub-basins of interest using a Lagrangian particle-based approach. These transport time scales are substantially important for the regional scientific community to assess the level of pollution in sub-basins and embayments in the inner Salish Sea.