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• 11. [Article] Adaptation of Classical Tidal Harmonic Analysis to Nonstationary Tides, with Application to River Tides

  One of the most challenging areas in tidal analysis is the study of nonstationary signals with a tidal component, as they confront both current analysis methods and dynamical understanding. A new analysis ...

  Citation × Citation Citation Abstract Copy Title: Adaptation of Classical Tidal Harmonic Analysis to Nonstationary Tides, with Application to River Tides Author: Matte, Pascal, Jay, David A., Zaron, Edward D. Year: 2013 One of the most challenging areas in tidal analysis is the study of nonstationary signals with a tidal component, as they confront both current analysis methods and dynamical understanding. A new analysis tool has been developed, NS_TIDE, adapted to the study of nonstationary signals, in this case, river tides. It builds the nonstationary forcing directly into the tidal basis functions. It is implemented by modification of T_TIDE; however, certain concepts, particularly the meaning of a constituent and the Rayleigh criterion, are redefined to account for the smearing effects on the tidal spectral lines by nontidal energy. An error estimation procedure is included that constructs a covariance matrix of the regression coefficients, based on either an uncorrelated or a correlated noise model. The output of NS_TIDE consists of time series of subtidal water levels [mean water level (MWL)] and tidal properties (amplitudes and phases), expressed in terms of external forcing functions. The method was tested using records from a station on the Columbia River, 172 km from the ocean entrance, where the tides are strongly altered by river flow. NS_TIDE hindcast explains 96.4% of the signal variance with a root-mean-square error of 0.165 m obtained from 288 parameters, far better than traditional harmonic analysis (38.5%, 0.604 m, and 127 parameters). While keeping the benefits of harmonic analysis, its advantages compared to existing tidal analysis methods include its capacity to distinguish frequencies within tidal bands without losing resolution in the time domain or data at the endpoints of the time series. Title: Adaptation of Classical Tidal Harmonic Analysis to Nonstationary Tides, with Application to River Tides Author: Matte, Pascal, Jay, David A., Zaron, Edward D. Year: 2013 One of the most challenging areas in tidal analysis is the study of nonstationary signals with a tidal component, as they confront both current analysis methods and dynamical understanding. A new analysis tool has been developed, NS_TIDE, adapted to the study of nonstationary signals, in this case, river tides. It builds the nonstationary forcing directly into the tidal basis functions. It is implemented by modification of T_TIDE; however, certain concepts, particularly the meaning of a constituent and the Rayleigh criterion, are redefined to account for the smearing effects on the tidal spectral lines by nontidal energy. An error estimation procedure is included that constructs a covariance matrix of the regression coefficients, based on either an uncorrelated or a correlated noise model. The output of NS_TIDE consists of time series of subtidal water levels [mean water level (MWL)] and tidal properties (amplitudes and phases), expressed in terms of external forcing functions. The method was tested using records from a station on the Columbia River, 172 km from the ocean entrance, where the tides are strongly altered by river flow. NS_TIDE hindcast explains 96.4% of the signal variance with a root-mean-square error of 0.165 m obtained from 288 parameters, far better than traditional harmonic analysis (38.5%, 0.604 m, and 127 parameters). While keeping the benefits of harmonic analysis, its advantages compared to existing tidal analysis methods include its capacity to distinguish frequencies within tidal bands without losing resolution in the time domain or data at the endpoints of the time series. Close

• 12. [Article] Particle Resuspension in the Columbia River Plume Near Field

  Measurements of suspended sediment concentration, velocity, salinity, and turbulent microscale shear in the near-field region of the Columbia River plume are used to investigate the mechanisms of sediment ...

  Citation × Citation Citation Abstract Copy Title: Particle Resuspension in the Columbia River Plume Near Field Author: Spahn, Emily Y., Horner-Devine, Alexander R., Nash, Jonathan, Jay, David A., Kilcher, Levi Year: 2009 Measurements of suspended sediment concentration, velocity, salinity, and turbulent microscale shear in the near-field region of the Columbia River plume are used to investigate the mechanisms of sediment resuspension and entrainment into the plume. An east-west transect was occupied during spring and neap tide periods in August 2005 and May 2006, corresponding to low and high river discharge conditions, respectively. During the high-discharge period the plume is decoupled from the bottom, and fine sediment resuspended from the bottom does not leave the benthic boundary layer. The primary modes of sediment transport associated with the plume are advection of sediment from the estuary and removal of sediment from the plume by gravitational settling and turbulent mixing. In contrast, the plume is much less stratified during low-discharge conditions, and large resuspension events are observed that entrained sediment through the water column and into the plume. Our measurements indicate that two factors control the magnitude and timing of sediment resuspension and entrainment: the supply of fine sediment on the seabed and the relative influence of tidal turbulence compared with buoyancy input from the river. The latter is quantified in terms of the estuary Richardson number RiE. The magnitude of vertical turbulent sediment flux is correlated with RiE during the low-flow period when there is a sufficient supply of bottom sediment in the near-field region. Such sediment resuspension may be an important mechanism for the delivery of bioavailable micronutrients to the plume during the summer. Title: Particle Resuspension in the Columbia River Plume Near Field Author: Spahn, Emily Y., Horner-Devine, Alexander R., Nash, Jonathan, Jay, David A., Kilcher, Levi Year: 2009 Measurements of suspended sediment concentration, velocity, salinity, and turbulent microscale shear in the near-field region of the Columbia River plume are used to investigate the mechanisms of sediment resuspension and entrainment into the plume. An east-west transect was occupied during spring and neap tide periods in August 2005 and May 2006, corresponding to low and high river discharge conditions, respectively. During the high-discharge period the plume is decoupled from the bottom, and fine sediment resuspended from the bottom does not leave the benthic boundary layer. The primary modes of sediment transport associated with the plume are advection of sediment from the estuary and removal of sediment from the plume by gravitational settling and turbulent mixing. In contrast, the plume is much less stratified during low-discharge conditions, and large resuspension events are observed that entrained sediment through the water column and into the plume. Our measurements indicate that two factors control the magnitude and timing of sediment resuspension and entrainment: the supply of fine sediment on the seabed and the relative influence of tidal turbulence compared with buoyancy input from the river. The latter is quantified in terms of the estuary Richardson number RiE. The magnitude of vertical turbulent sediment flux is correlated with RiE during the low-flow period when there is a sufficient supply of bottom sediment in the near-field region. Such sediment resuspension may be an important mechanism for the delivery of bioavailable micronutrients to the plume during the summer. Close

• 13. [Article] Particle resuspension in the Columbia River plume near field

  Copyrighted by American Geophysical Union.

  Citation × Citation Citation Abstract Copy Title: Particle resuspension in the Columbia River plume near field Author: Spahn, Emily Y., Jay, David A., Kilcher, Levi, Homer-Devine, Alexander R., Nash, Jonathan Copyrighted by American Geophysical Union. Title: Particle resuspension in the Columbia River plume near field Author: Spahn, Emily Y., Jay, David A., Kilcher, Levi, Homer-Devine, Alexander R., Nash, Jonathan Copyrighted by American Geophysical Union. Close

• 14. [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