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The Impact of Water Column Mixing in a Salt-Wedge Estuary
  • Joshua Johnson
Joshua Johnson

Corresponding Author:[email protected]

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The Puget Sound is a complex estuarine system within the Salish Sea, fed by both high salinity water from the Pacific Ocean and freshwater from a number of rivers. The Snohomish River is one of the largest of these freshwater inputs, transporting freshwater from the Skykomish and Snoqualmie rivers to Port Gardner Bay off the coast of Everett. At its mouth, the higher density salt water from the Puget Sound intrudes into the freshwater, forming a salt wedge that causes a highly stratified water column which rapidly changes with the tidal cycle. In this stratified water column, little mixing occurs between the different layers of the water, resulting in a lack of nutrients near the surface. This study aims to quantify the amount of mixing occurring at this location in relation to tidal patterns and season and analyze the effect varying levels of mixing have on related chemical properties. This research is being conducted at the Ocean Research College Academy (ORCA), a dual enrollment program through Everett Community College. In cooperation with Gravity Marine Consulting and the Port of Everett, ORCA has permanently moored a SeaBird CTD 3 meters below the surface in the mouth of the Snohomish River. The CTD captures temperature, salinity, chlorophyll, turbidity, and dissolved oxygen measurements at 30-minute intervals. Velocities in 3-dimensions are recorded by a Nortek Aquadopp. This study will define the characteristics of the salt wedge in relation to temperature and salinity and then look at its influence on chlorophyll and turbidity levels.