Flow convergence caused by a salinity minimum in a tidal channel


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dc.contributor.author Warner, John C.
dc.contributor.author Schoellhamer, David H.
dc.contributor.author Burau, Jon R.
dc.contributor.author Schladow, S. Geoffrey
dc.date.accessioned 2007-05-11T18:49:11Z
dc.date.available 2007-05-11T18:49:11Z
dc.date.issued 2006-12
dc.identifier.citation San Francisco Estuary and Watershed Science 4 (2006): Issue 3, Article 1 en
dc.identifier.uri http://hdl.handle.net/1912/1633
dc.description © 2006 The Author et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The definitive version was published in San Francisco Estuary and Watershed Science 4 (2006): Issue 3, Article 1. en
dc.description.abstract Residence times of dissolved substances and sedimentation rates in tidal channels are affected by residual (tidally averaged) circulation patterns. One influence on these circulation patterns is the longitudinal density gradient. In most estuaries the longitudinal density gradient typically maintains a constant direction. However, a junction of tidal channels can create a local reversal (change in sign) of the density gradient. This can occur due to a difference in the phase of tidal currents in each channel. In San Francisco Bay, the phasing of the currents at the junction of Mare Island Strait and Carquinez Strait produces a local salinity minimum in Mare Island Strait. At the location of a local salinity minimum the longitudinal density gradient reverses direction. This paper presents four numerical models that were used to investigate the circulation caused by the salinity minimum: (1) A simple one-dimensional (1D) finite difference model demonstrates that a local salinity minimum is advected into Mare Island Strait from the junction with Carquinez Strait during flood tide. (2) A three-dimensional (3D) hydrodynamic finite element model is used to compute the tidally averaged circulation in a channel that contains a salinity minimum (a change in the sign of the longitudinal density gradient) and compares that to a channel that contains a longitudinal density gradient in a constant direction. The tidally averaged circulation produced by the salinity minimum is characterized by converging flow at the bed and diverging flow at the surface, whereas the circulation produced by the constant direction gradient is characterized by converging flow at the bed and downstream surface currents. These velocity fields are used to drive both a particle tracking and a sediment transport model. (3) A particle tracking model demonstrates a 30 percent increase in the residence time of neutrally buoyant particles transported through the salinity minimum, as compared to transport through a constant direction density gradient. (4) A sediment transport model demonstrates increased deposition at the near-bed null point of the salinity minimum, as compared to the constant direction gradient null point. These results are corroborated by historically noted large sedimentation rates and a local maximum of selenium accumulation in clams at the null point in Mare Island Strait. en
dc.description.sponsorship The authors acknowledge support for this research from the California Department of Fish and Game, the California Coastal Conservancy, the U.S. Fish and Wildlife Service Coastal Program, and the U.S. Geological Survey Federal/State Cooperative and Priority Ecosystem Science Programs. en
dc.format.mimetype application/pdf
dc.language.iso en_US en
dc.publisher CALFED Science Program, the California Digital Library eScholarship Repository, and the University of California—Davis John Muir Institute of the Environment. en
dc.relation.uri http://repositories.cdlib.org/jmie/sfews/vol4/iss3/art1
dc.rights.uri http://creativecommons.org/licenses/by/3.0/us/ *
dc.subject Salinity minimum en
dc.subject Longitudinal density gradient en
dc.subject San Francisco Bay en
dc.subject Converging flow en
dc.subject Particle tracking en
dc.title Flow convergence caused by a salinity minimum in a tidal channel en
dc.type Article en

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