Density structure in the outflow region of Colvos Passage: Observational analysis and model comparison

Puget Sound lies in a densely populated region of the state of Washington with many potential sources of pollution. A better understanding of circulation patterns within Puget Sound, such as the complex intersection of Colvos Passage with Main Basin, is critical to predicting the long-term effects of pollutants. Whether Colvos water is flushed out towards the ocean or recirculated depends on specific details at this intersection. This study compares observations of the outflow from Colvos Passage with the depiction of the same area in LiveOcean, a computer model developed by the UW Coastal Modeling Group. While it appears that Colvos water becomes the surface layer in the outflow area, there is evidence that it settles into an intermediate layer outside of this region. This study finds evidence that a larger portion of water coming out of Colvos Passage is directed seaward in Main Basin than is recirculated through East Passage. The model comparison shows that, while LiveOcean reproduces the general structure of water masses in the area, it does not adequately resolve the interaction between water masses in the outflow area of Colvos Passage