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• 1. [Article] Particle Trapping in Stratified Estuaries - Definition of a Parameter Space

  Estuarine turbidity maxima (ETM) retain suspended particulate matter (SPM) through advection, settling, aggregation and non-linearities in bed processes. This contribution defines for the first time a ...

  Citation × Citation Citation Abstract Copy Title: Particle Trapping in Stratified Estuaries - Definition of a Parameter Space Author: Jay, David A., Orton, Philip M., Chisholm, Thomas A., Wilson, Douglas J., Fain, Annika M., McGinity, John Year: 2003 Estuarine turbidity maxima (ETM) retain suspended particulate matter (SPM) through advection, settling, aggregation and non-linearities in bed processes. This contribution defines for the first time a parameter space descriptive of ETM water-column particle trapping processes through a scaling analysis of the local and integral SPM balances. In the absence of long-term deposition, there are five primary parameters for the large particles or aggregates that are typically trapped. Rouse number P, the ratio of settling velocity WS of the SPM relative to the shear velocity U*, describes the material trapped in the ETM in terms of the local vertical balance between vertical mixing and aggregate settling. Advection number A= P ΔU/UT scales the landward transport of SPM by tidal and mean flow processes in terms of flood-ebb velocity difference (ΔU) and maximum tidal current (UT). Supply number SR = P UR/UT defines SPM supply and removal (UR is river flow). Changes in the estuarine inventory of SPM are described in terms of a Trapping Efficiency E, a ratio of peak ETM concentration to fluvial or marine supply concentration. The effects of aggregation in the integral dynamic balance are quantified by a Floc number F that describes the tendency of aggregates to form through shear-driven collisions. This study uses observations from two strongly advective systems (the Columbia and Fraser Rivers) plus literature values from 13 other estuaries to illustrate the applicability of the above scaling. The primary question investigated is the relationship of trapping efficiency E and Floc number F to other parameters, especially river flow (expressed in terms of supply number SR). The strongest SPM trapping (high E) occurs in mid-ETM, where A ~0. The extreme high flows observed in the Fraser River estuary show how ETM trapping becomes ineffective as the estuary length contracts to one tidal excursion or less (limit of high SR). Use of data from all 15 estuaries shows that there is a strong trend toward more efficient trapping for low SR. E and F are positively correlated, so that aggregation becomes more prominent in systems with weak to moderate river flow. Examination of tidal monthly and seasonal particle properties at four closely-spaced moorings in the Columbia emphasize the importance of strong ETM gradients – particle properties are diverse even when the hydrodynamic regime is apparently similar. Finally, scaling variables and data are combined to express ETM properties in terms of U*, UR and UT.. Title: Particle Trapping in Stratified Estuaries - Definition of a Parameter Space Author: Jay, David A., Orton, Philip M., Chisholm, Thomas A., Wilson, Douglas J., Fain, Annika M., McGinity, John Year: 2003 Estuarine turbidity maxima (ETM) retain suspended particulate matter (SPM) through advection, settling, aggregation and non-linearities in bed processes. This contribution defines for the first time a parameter space descriptive of ETM water-column particle trapping processes through a scaling analysis of the local and integral SPM balances. In the absence of long-term deposition, there are five primary parameters for the large particles or aggregates that are typically trapped. Rouse number P, the ratio of settling velocity WS of the SPM relative to the shear velocity U*, describes the material trapped in the ETM in terms of the local vertical balance between vertical mixing and aggregate settling. Advection number A= P ΔU/UT scales the landward transport of SPM by tidal and mean flow processes in terms of flood-ebb velocity difference (ΔU) and maximum tidal current (UT). Supply number SR = P UR/UT defines SPM supply and removal (UR is river flow). Changes in the estuarine inventory of SPM are described in terms of a Trapping Efficiency E, a ratio of peak ETM concentration to fluvial or marine supply concentration. The effects of aggregation in the integral dynamic balance are quantified by a Floc number F that describes the tendency of aggregates to form through shear-driven collisions. This study uses observations from two strongly advective systems (the Columbia and Fraser Rivers) plus literature values from 13 other estuaries to illustrate the applicability of the above scaling. The primary question investigated is the relationship of trapping efficiency E and Floc number F to other parameters, especially river flow (expressed in terms of supply number SR). The strongest SPM trapping (high E) occurs in mid-ETM, where A ~0. The extreme high flows observed in the Fraser River estuary show how ETM trapping becomes ineffective as the estuary length contracts to one tidal excursion or less (limit of high SR). Use of data from all 15 estuaries shows that there is a strong trend toward more efficient trapping for low SR. E and F are positively correlated, so that aggregation becomes more prominent in systems with weak to moderate river flow. Examination of tidal monthly and seasonal particle properties at four closely-spaced moorings in the Columbia emphasize the importance of strong ETM gradients – particle properties are diverse even when the hydrodynamic regime is apparently similar. Finally, scaling variables and data are combined to express ETM properties in terms of U*, UR and UT.. Close

• 2. [Article] Decadal-Scale Changes in West Coast Shelf Internal Tides (the Tides, They are a Changin')

  The National Science Foundation (NSF) Co-OP (Coastal Ocean Program) Project RISE (River-Influenced Shelf Ecosystems) seeks to understand how primary and secondary productivity are enhanced by large river ...

  Citation × Citation Citation Abstract Copy Title: Decadal-Scale Changes in West Coast Shelf Internal Tides (the Tides, They are a Changin') Author: Jay, David A., Chisholm, Thomas A., Krause, A., Leffler, K. Year: 2004 The National Science Foundation (NSF) Co-OP (Coastal Ocean Program) Project RISE (River-Influenced Shelf Ecosystems) seeks to understand how primary and secondary productivity are enhanced by large river plumes in upwelling regions, using the Columbia River plume as a case study. Columbia River plume waters are rich in silicate and iron, but relatively depleted in nitrate. Mixing of nitrate-rich upwelled water with the plume is, therefore, important to plume primary production. Large internal tidal currents cause part of the necessary mixing. Accordingly, any long-term changes in these internal tides could impact productivity. Because no decadal-scale current observations are available to evaluate changes in internal tides, an indirect approach is needed ? we examine long-term changes in the surface tide (which is affected by internal tides) relative to the astronomical tidal potential. Of course, observed tides are affected by human manipulation of coastal environments as well as by changes in internal tides. Thus, four methods were used to separate estuarine human and coastal effects on observed surface tides: (A) Examination of historical changes in tidal admittance along the West Coast using long-term tide stations between 16ø and 60.5ø N; 14 million hourly tidal heights for 1854 to 2004 were analyzed. These stations show a broad range of human impacts, but most show increasing tides. (B) Use of tidal constituent ratios to diagnose processes; e.g., a channelization-induced reduction in estuarine friction affects the S?/M? ratio, while a decrease in K1/M? may indicate the changing influence of internal tides, at least north of 30ø N. (C) Examination of the spatial pattern of tidal properties in the three major West Coast shallow estuaries for which multiple stations with long records are available (San Diego and San Francisco Bays and the Columbia). (D) Analysis of seasonal patterns in tidal admittance relative to river flow and sea level in the Columbia, to separate fluvial and shelf processes. Title: Decadal-Scale Changes in West Coast Shelf Internal Tides (the Tides, They are a Changin') Author: Jay, David A., Chisholm, Thomas A., Krause, A., Leffler, K. Year: 2004 The National Science Foundation (NSF) Co-OP (Coastal Ocean Program) Project RISE (River-Influenced Shelf Ecosystems) seeks to understand how primary and secondary productivity are enhanced by large river plumes in upwelling regions, using the Columbia River plume as a case study. Columbia River plume waters are rich in silicate and iron, but relatively depleted in nitrate. Mixing of nitrate-rich upwelled water with the plume is, therefore, important to plume primary production. Large internal tidal currents cause part of the necessary mixing. Accordingly, any long-term changes in these internal tides could impact productivity. Because no decadal-scale current observations are available to evaluate changes in internal tides, an indirect approach is needed ? we examine long-term changes in the surface tide (which is affected by internal tides) relative to the astronomical tidal potential. Of course, observed tides are affected by human manipulation of coastal environments as well as by changes in internal tides. Thus, four methods were used to separate estuarine human and coastal effects on observed surface tides: (A) Examination of historical changes in tidal admittance along the West Coast using long-term tide stations between 16ø and 60.5ø N; 14 million hourly tidal heights for 1854 to 2004 were analyzed. These stations show a broad range of human impacts, but most show increasing tides. (B) Use of tidal constituent ratios to diagnose processes; e.g., a channelization-induced reduction in estuarine friction affects the S?/M? ratio, while a decrease in K1/M? may indicate the changing influence of internal tides, at least north of 30ø N. (C) Examination of the spatial pattern of tidal properties in the three major West Coast shallow estuaries for which multiple stations with long records are available (San Diego and San Francisco Bays and the Columbia). (D) Analysis of seasonal patterns in tidal admittance relative to river flow and sea level in the Columbia, to separate fluvial and shelf processes. Close