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• 1. [Article] Archival Water-Level Measurements: Recovering Historical Data to Help Design for the Future

  Improving methods of assessing risk and designing structures to withstand extreme events and changing sea levels is a vital component of strategies for reducing risk to coastal resources and assets. An ...

  Citation × Citation Citation Abstract Copy Title: Archival Water-Level Measurements: Recovering Historical Data to Help Design for the Future Author: Talke, Stefan A., Jay, David A. Year: 2017 Improving methods of assessing risk and designing structures to withstand extreme events and changing sea levels is a vital component of strategies for reducing risk to coastal resources and assets. An obvious approach to improving the statistical robustness of risk assessments is to increase the number, time span, and quality of available water-level data sets, and to assess trends and non-stationarity. In this report we discuss efforts to recover, digitize, and analyze hundreds of station-years of lost-and-forgotten tide data and other water-level measurements that extend back to the early 19th century. To date, more than 6,500 station-years of previously lost or forgotten tide data have been identified, of which more than 1,600 station-years have been recovered and more than 550 station-years digitized. An additional 500+ years of once-a-day river-stage measurements in tidal rivers have been recovered and digitized. Approximately 300,000 documents have been recovered. In this report we also demonstrate how data recovery can help engineers better characterize their water-level environment and understand long-term trends, resulting in better risk assessment and ultimately more robust design of new infrastructure and adaptation of existing infrastructure. Long records help improve hazard estimates and can help characterize whether statistics are nonstationarity over climate-relevant time scales. Further, long and more complete records exhibit more natural variability and can be used to validate numerical simulations of historical storms (e.g., the 1893 New York hurricane). Historical tide data can help inform how tidal datums such as High Water and Low Water have changed, can be used to hindcast historical river flow, and provide a much richer view of long-term trends in local sea level. Used with numerical models, historical data help explain how anthropogenic activities have changed tide range and river slope, with the largest effects often observed far inland from the coast. Moreover, numerical models combined with tide data can be used to assess whether local engineering or other long-term changes have influenced storm surge risk. In conclusion, improved assessment of the past can help us better plan for the future. Title: Archival Water-Level Measurements: Recovering Historical Data to Help Design for the Future Author: Talke, Stefan A., Jay, David A. Year: 2017 Improving methods of assessing risk and designing structures to withstand extreme events and changing sea levels is a vital component of strategies for reducing risk to coastal resources and assets. An obvious approach to improving the statistical robustness of risk assessments is to increase the number, time span, and quality of available water-level data sets, and to assess trends and non-stationarity. In this report we discuss efforts to recover, digitize, and analyze hundreds of station-years of lost-and-forgotten tide data and other water-level measurements that extend back to the early 19th century. To date, more than 6,500 station-years of previously lost or forgotten tide data have been identified, of which more than 1,600 station-years have been recovered and more than 550 station-years digitized. An additional 500+ years of once-a-day river-stage measurements in tidal rivers have been recovered and digitized. Approximately 300,000 documents have been recovered. In this report we also demonstrate how data recovery can help engineers better characterize their water-level environment and understand long-term trends, resulting in better risk assessment and ultimately more robust design of new infrastructure and adaptation of existing infrastructure. Long records help improve hazard estimates and can help characterize whether statistics are nonstationarity over climate-relevant time scales. Further, long and more complete records exhibit more natural variability and can be used to validate numerical simulations of historical storms (e.g., the 1893 New York hurricane). Historical tide data can help inform how tidal datums such as High Water and Low Water have changed, can be used to hindcast historical river flow, and provide a much richer view of long-term trends in local sea level. Used with numerical models, historical data help explain how anthropogenic activities have changed tide range and river slope, with the largest effects often observed far inland from the coast. Moreover, numerical models combined with tide data can be used to assess whether local engineering or other long-term changes have influenced storm surge risk. In conclusion, improved assessment of the past can help us better plan for the future. Close

• 2. [Article] The Columbia River Plume Study: Subtidal Variability in the Velocity and Salinity Fields

  A comprehensive study of the strongly wind driven midlatitude buoyant plume from the Columbia River, located on the U.S. west coast, demonstrates that the plume has two basic structures during the fall/winter ...

  Citation × Citation Citation Abstract Copy Title: The Columbia River Plume Study: Subtidal Variability in the Velocity and Salinity Fields Author: Hickey, B. M., Pietrafesa, Leonard J., Jay, David A., Boicourt, William C. Year: 1998 A comprehensive study of the strongly wind driven midlatitude buoyant plume from the Columbia River, located on the U.S. west coast, demonstrates that the plume has two basic structures during the fall/winter season, namely, a thin (~5~15 m), strongly stratified plume tending west to northwestward during periods of southward or light northward wind stress and a thicker (~10~40 m), weakly stratified plume tending northward and hugging the coast during periods of stronger northward stress. The plume and its velocity field respond nearly instantaneously to changes in wind speed or direction, and the wind fluctuations have timescales of 2-10 days. Frictional wind-driven currents cause the primarily unidirectional flow down the plume axis to veer to the right or left of the axis for northward or southward winds, respectively. Farther downstream, currents turn to parallel rather than cross salinity contours, consistent with a geostrophic balance. In particular, during periods when the plume is separated from the coast, currents tend to flow around the mound of fresher water. At distances exceeding about 20 km from the river mouth, the along-shelf depth-averaged flow over the inner to midshelf is linear, and depth-averaged acceleration is governed to lowest order by the difference between surface and bottom stress alone. In this region, along-shelf geostrophic buoyancy-driven currents at ~5 m (calculated from surface density) and along-shelf geostrophic wind-driven currents (computed from a depth-averaged linear model) are comparable in magnitude (~10-25 cm-1 ). Title: The Columbia River Plume Study: Subtidal Variability in the Velocity and Salinity Fields Author: Hickey, B. M., Pietrafesa, Leonard J., Jay, David A., Boicourt, William C. Year: 1998 A comprehensive study of the strongly wind driven midlatitude buoyant plume from the Columbia River, located on the U.S. west coast, demonstrates that the plume has two basic structures during the fall/winter season, namely, a thin (~5~15 m), strongly stratified plume tending west to northwestward during periods of southward or light northward wind stress and a thicker (~10~40 m), weakly stratified plume tending northward and hugging the coast during periods of stronger northward stress. The plume and its velocity field respond nearly instantaneously to changes in wind speed or direction, and the wind fluctuations have timescales of 2-10 days. Frictional wind-driven currents cause the primarily unidirectional flow down the plume axis to veer to the right or left of the axis for northward or southward winds, respectively. Farther downstream, currents turn to parallel rather than cross salinity contours, consistent with a geostrophic balance. In particular, during periods when the plume is separated from the coast, currents tend to flow around the mound of fresher water. At distances exceeding about 20 km from the river mouth, the along-shelf depth-averaged flow over the inner to midshelf is linear, and depth-averaged acceleration is governed to lowest order by the difference between surface and bottom stress alone. In this region, along-shelf geostrophic buoyancy-driven currents at ~5 m (calculated from surface density) and along-shelf geostrophic wind-driven currents (computed from a depth-averaged linear model) are comparable in magnitude (~10-25 cm-1 ). Close

• 3. [Article] Interfacial Mixing in a Highly Stratified Estuary: 2. A "Method of Constrained Differences" Approach for the Determination of the Momentum and Mass Balances and the Energy of Mixing

  This article is Part 2 of a set of papers addressing mixing in a highly stratified estuary. In Part 2, turbulence and mean flow measurements are together used to understand the role of mixing in the overall ...

  Citation × Citation Citation Abstract Copy Title: Interfacial Mixing in a Highly Stratified Estuary: 2. A "Method of Constrained Differences" Approach for the Determination of the Momentum and Mass Balances and the Energy of Mixing Author: Kay, David J., Jay, David A. Year: 2003 This article is Part 2 of a set of papers addressing mixing in a highly stratified estuary. In Part 2, turbulence and mean flow measurements are together used to understand the role of mixing in the overall dynamics of the system. Estimates of the partition of energy dissipation between bed-generated and internal mixing suggest that internal mixing accounts for about two thirds of the total turbulent kinetic energy (TKE) produced in the salt-wedge reach of the Columbia River estuary during the neap-tide, moderate river-flow observation period. This suggests that internal mixing plays a larger role in the energetics of such systems than has previously been recognized. The lack of near-bed mixing on the neap is also likely a major factor in the accumulation of sediment in the estuary on neap tides. Profiles of estimated turbulent kinetic energy (TKE) dissipation were obtained using a new approach, which we call the "method of constrained differences," that allows the calculation of all major terms in the momentum and density balances during ebb mixing events from data obtained by a single vessel. The method of constrained differences uses a local equilibrium turbulence closure and measured velocity and density profiles to determine the density flux divergence necessary for internal consistency in the momentum and mass equations. The calculated mixing rates from the iterative procedure compare favorably with measured dissipation rates, tending to validate both the measurements and the procedure. Although this method involves a constraint of the form of a known or inferred stress at some point in the water column, it has the potential for wide application, especially if point measurements of TKE dissipation rates are available. Title: Interfacial Mixing in a Highly Stratified Estuary: 2. A "Method of Constrained Differences" Approach for the Determination of the Momentum and Mass Balances and the Energy of Mixing Author: Kay, David J., Jay, David A. Year: 2003 This article is Part 2 of a set of papers addressing mixing in a highly stratified estuary. In Part 2, turbulence and mean flow measurements are together used to understand the role of mixing in the overall dynamics of the system. Estimates of the partition of energy dissipation between bed-generated and internal mixing suggest that internal mixing accounts for about two thirds of the total turbulent kinetic energy (TKE) produced in the salt-wedge reach of the Columbia River estuary during the neap-tide, moderate river-flow observation period. This suggests that internal mixing plays a larger role in the energetics of such systems than has previously been recognized. The lack of near-bed mixing on the neap is also likely a major factor in the accumulation of sediment in the estuary on neap tides. Profiles of estimated turbulent kinetic energy (TKE) dissipation were obtained using a new approach, which we call the "method of constrained differences," that allows the calculation of all major terms in the momentum and density balances during ebb mixing events from data obtained by a single vessel. The method of constrained differences uses a local equilibrium turbulence closure and measured velocity and density profiles to determine the density flux divergence necessary for internal consistency in the momentum and mass equations. The calculated mixing rates from the iterative procedure compare favorably with measured dissipation rates, tending to validate both the measurements and the procedure. Although this method involves a constraint of the form of a known or inferred stress at some point in the water column, it has the potential for wide application, especially if point measurements of TKE dissipation rates are available. Close

• 4. [Article] Impacts of Columbia River Discharge on Salmonid Habitat: 2. Changes in Shallow-Water Habitat

  This is the second part of an investigation that analyzes human alteration of shallow-water habitat (SWH) available to juvenile salmonids in the tidal Lower Columbia River. Part 2 develops a one-dimensional, ...

  Citation × Citation Citation Abstract Copy Title: Impacts of Columbia River Discharge on Salmonid Habitat: 2. Changes in Shallow-Water Habitat Author: Jay, David A., Kukulka, Tobias Year: 2003 This is the second part of an investigation that analyzes human alteration of shallow-water habitat (SWH) available to juvenile salmonids in the tidal Lower Columbia River. Part 2 develops a one-dimensional, subtidal river stage model that explains ~90% of the stage variance in the tidal river. This model and the tidal model developed in part 1 (Kukulka and Jay, 2003) uncouple the nonlinear interaction of river tides and river stage by referring both to external forcing by river discharge, ocean tides, and atmospheric pressure. Applying the two models, daily high-water levels were predicted for a reach from rkm-50 to rkm-90 during 1974 to 1998, the period of contemporary management. Predicted water levels were related to the bathymetry and topography to determine the changes in shallow-water habitat area (SWHA) caused by flood control dikes and altered flow management. Model results suggest that diking and a >40% reduction of peak flows have reduced SWHA by ~62% during the crucial spring freshet period during which juvenile salmon use of SWHA is maximal. Taken individually, diking and flow cycle alteration reduced spring freshet SWHA by 52% and 29%, respectively. SWHA has been both displaced to lower elevations and modified in its character because tidal range has increased. Our models of these processes are economical for the very long simulations (seasons to centuries) needed to understand historic changes and climate impacts on SWH. Through analysis of the nonlinear processes controlling surface elevation in a tidal river, we have identified some of the mechanisms that link freshwater discharge to SWH and salmonid survival. Title: Impacts of Columbia River Discharge on Salmonid Habitat: 2. Changes in Shallow-Water Habitat Author: Jay, David A., Kukulka, Tobias Year: 2003 This is the second part of an investigation that analyzes human alteration of shallow-water habitat (SWH) available to juvenile salmonids in the tidal Lower Columbia River. Part 2 develops a one-dimensional, subtidal river stage model that explains ~90% of the stage variance in the tidal river. This model and the tidal model developed in part 1 (Kukulka and Jay, 2003) uncouple the nonlinear interaction of river tides and river stage by referring both to external forcing by river discharge, ocean tides, and atmospheric pressure. Applying the two models, daily high-water levels were predicted for a reach from rkm-50 to rkm-90 during 1974 to 1998, the period of contemporary management. Predicted water levels were related to the bathymetry and topography to determine the changes in shallow-water habitat area (SWHA) caused by flood control dikes and altered flow management. Model results suggest that diking and a >40% reduction of peak flows have reduced SWHA by ~62% during the crucial spring freshet period during which juvenile salmon use of SWHA is maximal. Taken individually, diking and flow cycle alteration reduced spring freshet SWHA by 52% and 29%, respectively. SWHA has been both displaced to lower elevations and modified in its character because tidal range has increased. Our models of these processes are economical for the very long simulations (seasons to centuries) needed to understand historic changes and climate impacts on SWH. Through analysis of the nonlinear processes controlling surface elevation in a tidal river, we have identified some of the mechanisms that link freshwater discharge to SWH and salmonid survival. Close

• 5. [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

• 6. [Article] River-Tide Dynamics: Exploration of Nonstationary and Nonlinear Tidal Behavior in the Yangtze River Estuary

  River-tide dynamics remain poorly understood, in part because conventional harmonic analysis (HA) does not cope effectively with nonstationary signals. To explore nonstationary behavior of river tides ...

  Citation × Citation Citation Abstract Copy Title: River-Tide Dynamics: Exploration of Nonstationary and Nonlinear Tidal Behavior in the Yangtze River Estuary Author: Guo, Leicheng, van der Wegen, Mick, Jay, David A., Matte, Pascal, Wang, Zheng Bing, Roelvink, Dano, He, Qing Year: 2015 River-tide dynamics remain poorly understood, in part because conventional harmonic analysis (HA) does not cope effectively with nonstationary signals. To explore nonstationary behavior of river tides and the modulation effects of river discharge, this work analyzes tidal signals in the Yangtze River estuary using both HA in a nonstationary mode and continuous wavelet transforms (CWT). The Yangtze is an excellent natural laboratory to analyze river tides because of its high and variable flow, its length, and the fact that there are do dams or reflecting barriers within the tidal part of the system. Analysis of tidal frequencies by CWT and analysis of subtidal water level and tidal ranges reveal a broad range of subtidal variations over fortnightly, monthly, semiannual, and annual frequencies driven by subtidal variations in friction and by variable river discharges. We employ HA in a nonstationary mode (NSHA) by segregating data within defined flow ranges into separate analyses. NSHA quantifies the decay of the principal tides and the modulation of M4 tide with increasing river discharges. M4 amplitudes decrease far upriver (landward portion of the estuary) and conversely increase close to the ocean as river discharge increases. The fortnightly frequencies reach an amplitude maximum upriver of that for over tide frequencies, due to the longer wavelength of the fortnightly constituents. These methods and findings should be applicable to large tidal rivers globally and have broad implications regarding management of navigation channels and ecosystems in tidal rivers. Title: River-Tide Dynamics: Exploration of Nonstationary and Nonlinear Tidal Behavior in the Yangtze River Estuary Author: Guo, Leicheng, van der Wegen, Mick, Jay, David A., Matte, Pascal, Wang, Zheng Bing, Roelvink, Dano, He, Qing Year: 2015 River-tide dynamics remain poorly understood, in part because conventional harmonic analysis (HA) does not cope effectively with nonstationary signals. To explore nonstationary behavior of river tides and the modulation effects of river discharge, this work analyzes tidal signals in the Yangtze River estuary using both HA in a nonstationary mode and continuous wavelet transforms (CWT). The Yangtze is an excellent natural laboratory to analyze river tides because of its high and variable flow, its length, and the fact that there are do dams or reflecting barriers within the tidal part of the system. Analysis of tidal frequencies by CWT and analysis of subtidal water level and tidal ranges reveal a broad range of subtidal variations over fortnightly, monthly, semiannual, and annual frequencies driven by subtidal variations in friction and by variable river discharges. We employ HA in a nonstationary mode (NSHA) by segregating data within defined flow ranges into separate analyses. NSHA quantifies the decay of the principal tides and the modulation of M4 tide with increasing river discharges. M4 amplitudes decrease far upriver (landward portion of the estuary) and conversely increase close to the ocean as river discharge increases. The fortnightly frequencies reach an amplitude maximum upriver of that for over tide frequencies, due to the longer wavelength of the fortnightly constituents. These methods and findings should be applicable to large tidal rivers globally and have broad implications regarding management of navigation channels and ecosystems in tidal rivers. Close

• 7. [Article] Estimation of Columbia River Virgin Flow: 1879 to 1928

  The Columbia River has historically been a major source of economic activity for the Pacific Northwest, and is one of the more heavily modified rivers in the United States today. Understanding human and ...

  Citation × Citation Citation Abstract Copy Title: Estimation of Columbia River Virgin Flow: 1879 to 1928 Author: Naik, Pradeep K., Jay, David A. Year: 2005 The Columbia River has historically been a major source of economic activity for the Pacific Northwest, and is one of the more heavily modified rivers in the United States today. Understanding human and climate-induced changes in its hydrologic properties is, therefore, a topic of considerable interest. Long streamflow records are essential to determining how runoff has changed over time. Daily streamflow records of the Columbia River at The Dalles dates back to June 1978. However, the observed daily flow does not alone provide enough information to understand or separate anthropogenic and climate effects. It is necessary also to have an estimate of virgin flow of the river to provide a historical perspective of water resources development, separate anthropogenic and climate effects, and compare present water use scenarios with those of the past decades. The United State Geological Survey (USGS) has calculated a monthly averaged adjusted river flow at The Dalles for 1879-1999 that accounts for the effects of flow regulation. The Bonneville Power Administration (BPA) has estimated the monthly averaged virgin (or naturalized) flow at The Dalles, i.e., the flow in the absence of both flow regulation and irrigation depletion for 1929-89. We have estimated the monthly virgin flow of the Columbia River at The Dalles from records of irrigated area for the missing years, i.e., for the period 1879-1928. In addition, a filtered version of the daily observed flows were combined with monthly virgin flow corrections to obtain estimates of daily virgin flows with realistic higher moments and spectral properties. Examination of the virgin flow record shows that climate change since late 19th century has caused a decrease of >7% in its annual average flow volume. The decrease in flow due to irrigation diversion during the same period is also ~7%. Broadly speaking, there are three periods of Columbia River flow management. Before 1900, mainstem dams were absent and flow diversions relatively small. Numerous dams were constructed between 1900 and 1970, and irrigation depletion increased 500%. Since about 1970, river flows have been managed on a system-wide basin, effecting significant interannual transfers of flows for the first time. Title: Estimation of Columbia River Virgin Flow: 1879 to 1928 Author: Naik, Pradeep K., Jay, David A. Year: 2005 The Columbia River has historically been a major source of economic activity for the Pacific Northwest, and is one of the more heavily modified rivers in the United States today. Understanding human and climate-induced changes in its hydrologic properties is, therefore, a topic of considerable interest. Long streamflow records are essential to determining how runoff has changed over time. Daily streamflow records of the Columbia River at The Dalles dates back to June 1978. However, the observed daily flow does not alone provide enough information to understand or separate anthropogenic and climate effects. It is necessary also to have an estimate of virgin flow of the river to provide a historical perspective of water resources development, separate anthropogenic and climate effects, and compare present water use scenarios with those of the past decades. The United State Geological Survey (USGS) has calculated a monthly averaged adjusted river flow at The Dalles for 1879-1999 that accounts for the effects of flow regulation. The Bonneville Power Administration (BPA) has estimated the monthly averaged virgin (or naturalized) flow at The Dalles, i.e., the flow in the absence of both flow regulation and irrigation depletion for 1929-89. We have estimated the monthly virgin flow of the Columbia River at The Dalles from records of irrigated area for the missing years, i.e., for the period 1879-1928. In addition, a filtered version of the daily observed flows were combined with monthly virgin flow corrections to obtain estimates of daily virgin flows with realistic higher moments and spectral properties. Examination of the virgin flow record shows that climate change since late 19th century has caused a decrease of >7% in its annual average flow volume. The decrease in flow due to irrigation diversion during the same period is also ~7%. Broadly speaking, there are three periods of Columbia River flow management. Before 1900, mainstem dams were absent and flow diversions relatively small. Numerous dams were constructed between 1900 and 1970, and irrigation depletion increased 500%. Since about 1970, river flows have been managed on a system-wide basin, effecting significant interannual transfers of flows for the first time. Close

• 8. [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

• 9. [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

• 10. [Article] Asymmetry of Tidal Plume Fronts in an Eastern Boundary Current Regime

  The Columbia River tidal plume or near-field is formed twice daily by the ebb outflow of the Columbia River. It is a part of a larger, anticyclonic plume bulge, which in turn is embedded in far-field plume ...

  Citation × Citation Citation Abstract Copy Title: Asymmetry of Tidal Plume Fronts in an Eastern Boundary Current Regime Author: Jay, David A., Pan, Jiayi, Orton, Philip M., Horner-Devine, Alexander R. Year: 2006 The Columbia River tidal plume or near-field is formed twice daily by the ebb outflow of the Columbia River. It is a part of a larger, anticyclonic plume bulge, which in turn is embedded in far-field plume and coastal waters. Because of the mixing caused directly and indirectly by plume fronts, the interaction of the tidal plume and bulge with the California Current upwelling regime plays a vital role in coastal productivity on the Oregon and Washington shelves. The tidal plume is initially supercritical with respect to the internal Froude number on all stronger ebbs. It is separated from the plume bulge by a front, whose properties are very different under upwelling vs. downwelling conditions. Under summer upwelling conditions, this front is sharp and narrow (only 50-100 m wide on its upwind or northern side) and marks a transition from supercritical to subcritical flow for 6-12 hours after high water. This sharp front is a source of turbulent mixing, despite the strong stratification. Because the tidal plume may overlie newly upwelled waters, these fronts can mix nutrients into the plume, enhancing primary productivity. Symmetry would suggest that there should be a sharp front south of the estuary mouth under summer downwelling conditions. Instead, the downwelling tidal plume front is usually broad (up to several km) and diffuse on the upstream side. Less mixing occurs, and the water immediately below the plume consists of old plume and surface ocean waters, both low in nutrients. There is also a second up-welling-downwelling asymmetry. Supercritical upwelling plume fronts often generate solitons trains as they slow and transition to a subcritical state. These soliton trains contribute to vertical mixing in the plume bulge and have a non-zero Stokes drift so that they transport low-salinity water across the tidal plume into the plume bulge. Under downwelling conditions, soliton forma-tion is uncommon. Moreover, solition formation almost always begins on the south side of the plume so that the front "unzips" from south to north. This implies that a frontal transition from supercritical to subcritical conditions first occurs on the south side tidal plume, regardless of whether this is the upwind or downwind side of the plume. This contribution describes and analyzes these two asymmetries using vessel data, SAR images and a vorticity analysis. Internal Froude number and plume depth are key parameters in distinguishing the upwelling and downwelling situations, and the observed asymmetries can be explained in terms of potential vorticity conservation. The tidal outflow embeds relative vorticity in the emerging tidal plume water mass. This vorticity controls the transition of the tidal plume front to a subcritical state and the timing and location of internal wave generation by plume fronts. Title: Asymmetry of Tidal Plume Fronts in an Eastern Boundary Current Regime Author: Jay, David A., Pan, Jiayi, Orton, Philip M., Horner-Devine, Alexander R. Year: 2006 The Columbia River tidal plume or near-field is formed twice daily by the ebb outflow of the Columbia River. It is a part of a larger, anticyclonic plume bulge, which in turn is embedded in far-field plume and coastal waters. Because of the mixing caused directly and indirectly by plume fronts, the interaction of the tidal plume and bulge with the California Current upwelling regime plays a vital role in coastal productivity on the Oregon and Washington shelves. The tidal plume is initially supercritical with respect to the internal Froude number on all stronger ebbs. It is separated from the plume bulge by a front, whose properties are very different under upwelling vs. downwelling conditions. Under summer upwelling conditions, this front is sharp and narrow (only 50-100 m wide on its upwind or northern side) and marks a transition from supercritical to subcritical flow for 6-12 hours after high water. This sharp front is a source of turbulent mixing, despite the strong stratification. Because the tidal plume may overlie newly upwelled waters, these fronts can mix nutrients into the plume, enhancing primary productivity. Symmetry would suggest that there should be a sharp front south of the estuary mouth under summer downwelling conditions. Instead, the downwelling tidal plume front is usually broad (up to several km) and diffuse on the upstream side. Less mixing occurs, and the water immediately below the plume consists of old plume and surface ocean waters, both low in nutrients. There is also a second up-welling-downwelling asymmetry. Supercritical upwelling plume fronts often generate solitons trains as they slow and transition to a subcritical state. These soliton trains contribute to vertical mixing in the plume bulge and have a non-zero Stokes drift so that they transport low-salinity water across the tidal plume into the plume bulge. Under downwelling conditions, soliton forma-tion is uncommon. Moreover, solition formation almost always begins on the south side of the plume so that the front "unzips" from south to north. This implies that a frontal transition from supercritical to subcritical conditions first occurs on the south side tidal plume, regardless of whether this is the upwind or downwind side of the plume. This contribution describes and analyzes these two asymmetries using vessel data, SAR images and a vorticity analysis. Internal Froude number and plume depth are key parameters in distinguishing the upwelling and downwelling situations, and the observed asymmetries can be explained in terms of potential vorticity conservation. The tidal outflow embeds relative vorticity in the emerging tidal plume water mass. This vorticity controls the transition of the tidal plume front to a subcritical state and the timing and location of internal wave generation by plume fronts. Close