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 Fortnightly modulations in tidal mixing acting as an in-shore/off-shore value for nutrient fluxes
EP21453
Poster Title: Fortnightly modulations in tidal mixing acting as an in-shore/off-shore value for nutrient fluxes
Submitted on 25 Feb 2014
Author(s): Dewey, R(1)., Masson, D.(2), MacCready, P.(3)
Affiliations: 1: Ocean Networks Canada 2: Institute of Ocean Sciences 3: University of Washington
Poster Views: 1,596
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Poster Information
Abstract: Tidal currents in the Gulf and San Juan Islands of the Salish Sea drive turbulent mixing, which has a modulating effect on the superimposed estuarine circulation. Strongly influenced by the spring freshet of the Fraser River and the seasonal upwelling off the west coast of Vancouver Inland, the estuarine circulation brings dense salty, nutrient rich water into the Salish Sea via Juan de Fuca Strait. During spring tides, currents are strong and tidal mixing is intense. The estuarine circulation is some-what blocked by the vertically mixed water, but the vertical exchange enhances the export of salt and nutrients out of the estuary in the surface layer, feeding ecosystems on the west coast. Similarly, during neap tides, currents are weaker and tidal mixing is greatly reduced. The estuarine circulation is flattened, allowing undiluted salty, nutrient rich deep water to penetrate into the deeper recesses of the inner basins, thus feeding the inner seas. Historic and real-time observatory data suggest that the fortnightly tidal cycle results in a net transport of nutrients off-shore following spring tides and in-shore following neap tides.Summary: Tidal currents in the Gulf and San Juan Islands of the Salish Sea drive turbulent mixing, which has a modulating effect on the superimposed estuarine circulation.References: Benjamin, 1968: Gravity Currents and related Phenomena, JFM, v31, 209-248. Geyer and Cannon,1982: Sill Processes Related to Deep Water Renewal in a Fjord, JGR, v87, 7985-7996.

Crawford and Dewey, 1988: Turbulence and Mixing: Sources of Nutrients on the VI
Continental Shelf, A-O, v27, 428-442.

Griffin and LeBlond, 1990: Estuary/Ocean Exchange Controlled by Spring/Neap Tidal
Mixing, ECSS, v30, 275-297.

Masson, 2002: Deep Water Renewal in the Strait of Georgia, EC
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