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Daniel R Cayan - One of the best experts on this subject based on the ideXlab platform.

  • potential effects of global warming on the sacramento san joaquin watershed and the san francisco estuary
    Geophysical Research Letters, 2002
    Co-Authors: Noah Knowles, Daniel R Cayan
    Abstract:

    [1] California's primary hydrologic system, the San Francisco estuary and its upstream watershed, is vulnerable to the regional hydrologic consequences of projected global climate change. Projected temperature anomalies from a global climate model are used to drive a combined model of watershed hydrology and Estuarine Dynamics. By 2090, a projected temperature increase of 2.1°C results in a loss of about half of the average April snowpack storage, with greatest losses in the northern headwaters. Consequently, spring runoff is reduced by 5.6 km3 (∼20% of historical annual runoff), with associated increases in winter flood peaks. The smaller spring flows yield spring/summer salinity increases of up to 9 psu, with larger increases in wet years.

Amoudry, Laurent O. - One of the best experts on this subject based on the ideXlab platform.

  • Unravelling interactions between asymmetric tidal turbulence, residual circulation and salinity Dynamics in short, periodically weakly stratified estuaries
    'American Meteorological Society', 2021
    Co-Authors: Wei Xiaoyan, Schuttelaars, Henk M., Williams, Megan E., Brown, Jennifer M., Thorne, Peter D., Amoudry, Laurent O.
    Abstract:

    Asymmetric tidal turbulence (ATT) strongly influences Estuarine health and functioning. However, its impact on the three-dimensional Estuarine Dynamics and the feedback of water motion and salinity distribution on ATT remain poorly understood, especially for short estuaries (Estuarine length ≪ tidal wavelength). This study systematically investigates the above-mentioned interactions in a short estuary for the first time, considering periodically weakly stratified conditions. This is done by developing a three-dimensional semi-analytical model (combining perturbation method with finite element method) that allows a dissection of the contributions of different processes to ATT, Estuarine circulation, and salt transport. The generation of ATT is dominated by (i) strain-induced periodic stratification and (ii) asymmetric bottom shear generated turbulence, and their contributions to ATT are different both in amplitude and phase. The magnitude of the residual circulation related to ATT and the eddy viscosity-shear covariance (ESCO) is about half of that of the gravitational circulation (GC) and shows a ‘reversed’ pattern as compared to GC. ATT generated by (i) contributes to an ESCO circulation with a spatial structure similar to GC. This circulation reduces the longitudinal salinity gradients and thus weakens GC. Contrastingly, the ESCO circulation due to (ii) shows patterns opposite to GC and acts to enhance GC. Concerning the salinity Dynamics at steady state, GC and tidal pumping are equally important to salt import, whereas ESCO circulation yields a significant seaward salt transport. These findings highlight the importance of identifying the sources of ATT to understand its impact on Estuarine circulation and salt distribution

  • Unraveling interactions between asymmetric tidal turbulence, residual circulation, and salinity Dynamics in short, periodically weakly stratified estuaries
    'American Meteorological Society', 2021
    Co-Authors: Wei Xiaoyan, Williams, Megan E., Brown, Jennifer M., Thorne, Peter D., Schuttelaars H.m., Amoudry, Laurent O.
    Abstract:

    Asymmetric tidal turbulence (ATT) strongly influences Estuarine health and functioning. However, its impact on the three-dimensional Estuarine Dynamics and the feedback of water motion and salinity distribution on ATT remain poorly understood, especially for short estuaries (Estuarine length ≪ tidal wavelength). This study systematically investigates the abovementioned interactions in a short estuary for the first time, considering periodically weakly stratified conditions. This is done by developing a three-dimensional semi-analytical model (combining perturbation method with finite element method) that allows a dissection of the contributions of different processes to ATT, Estuarine circulation, and salt transport. The generation of ATT is dominated by (i) strain-induced periodic stratification and (ii) asymmetric bottomshear-generated turbulence, and their contributions to ATT are different both in amplitude and phase. The magnitude of the residual circulation related to ATT and the eddy viscosity–shear covariance (ESCO) is about half of that of the gravitational circulation (GC) and shows a ‘‘reversed’’ pattern as compared to GC. ATT generated by strain-induced periodic stratification contributes to an ESCO circulation with a spatial structure similar to GC. This circulation reduces the longitudinal salinity gradients and thus weakens GC. Contrastingly, the ESCO circulation due to asymmetric bottom-sheargenerated turbulence shows patterns opposite to GC and acts to enhance GC. Concerning the salinity Dynamics at steady state, GC and tidal pumping are equally important to salt import, whereas ESCO circulation yields a significant seaward salt transport. These findings highlight the importance of identifying the sources of ATT to understand its impact on Estuarine circulation and salt distribution.Mathematical Physic

Hoang Olivia - One of the best experts on this subject based on the ideXlab platform.

  • Longitudinal versus Lateral Estuarine Dynamics and Their Role in Tidal Stratification Patterns in Lower South San Francisco Bay
    eScholarship University of California, 2019
    Co-Authors: Hoang Olivia
    Abstract:

    The Dynamics of shoal‐channel estuaries require consideration of lateral gradients and transport, which can create significant intratidal variability in stratification and circulation. When the shoal‐channel system is strongly coupled by tidal exchange with mudflats, marshes or other habitats, the gradients driving intratidal stratification variations are expected to intensify. To examine this dynamic, hydrodynamic data was collected from January 27, 2017 ‐ February 10, 2017 in Lower South San Francisco Bay, a small subembayment fringed by extensive shallow vegetated habitats. During this deployment, salinity variations were captured through instrumentation of 6 stations (arrayed longitudinally and laterally) allowing for mechanisms of stratification creation and destruction to be calculated directly and compared with observed time variability of stratification at the central station. We present observation‐based calculations of longitudinal straining, longitudinal advection, lateral straining, and lateral advection. The time dependence of stratification was observed directly and calculated by summing measured longitudinal and lateral mechanisms.We found that the stratification Dynamics switch between being longitudinally dominated during the middle of ebb and flood tides to being laterally dominated during the tidal transitions. This variability is driven by the interplay between tidally‐variable lateral density gradients and turbulent mixing. Relatively constant along‐estuary density gradients are differentially advected during flood and ebb tides, resulting in maximal lateral density gradients around tidal transitions. Simultaneous decrease in turbulent mixing at slack tides allows lateral density‐driven exchange to stratify the estuary channel at the slack after flood. At the end of ebb, barotropic forcing drives negatively buoyant shoal waters towards the channel. Plain Language Summary San Francisco Bay sits within a highly urbanized area. The dense population creates large wastewater effluent resulting in high nutrient levels. Scientists wonder why there have not been annual phytoplankton blooms like observed in other estuaries with lower nutrient levels. Some have hypothesized it is due to high turbidity levels and tidal breakdown of stratification creating nonideal environments for phytoplankton growth. However, decadal‐trends show that the estuary is becoming less turbid, and with changes in climate patterns, there is potential for persistent stratification.We observed development of stratification over the ebb tide and destratification in two distinct events as the tide reverses over the flood tide. At the reversal of the tides, water in the shoals exchange with the water in the channel creating a pulse of salty water to the channel at the ebb to flood transition and a pulse of fresh water at the flood to the ebb transition. Destratification occurs in the early flood tide due to a pulse of saline water received from the shoals then due to the advection of less stratified water being pulled to the center channel of the estuary. Finally, stratification is destroyed completely due to longitudinal straining and turbulent mixing

  • Longitudinal Versus Lateral Estuarine Dynamics and Their Role in Tidal Stratification Patterns in Lower South San Francisco Bay
    'American Geophysical Union (AGU)', 2019
    Co-Authors: Hoang Olivia, Stacey Mark, Senn David, Holleman Rusty, Macvean Lissa
    Abstract:

    The Dynamics of shoal‐channel estuaries require consideration of lateral gradients and transport, which can create significant intratidal variability in stratification and circulation. When the shoal‐channel system is strongly coupled by tidal exchange with mudflats, marshes, or other habitats, the gradients driving intratidal stratification variations are expected to intensify. To examine this dynamic, hydrodynamic data were collected from 27 January 2017 to 10 February 2017 in Lower South San Francisco Bay, a small subembayment fringed by extensive shallow vegetated habitats. During this deployment, salinity variations were captured through instrumentation of six stations (arrayed longitudinally and laterally) allowing for mechanisms of stratification creation and destruction to be calculated directly and compared with observed time variability of stratification at the central station. We present observation‐based calculations of longitudinal straining, longitudinal advection, lateral straining, and lateral advection. The time dependence of stratification was observed directly and calculated by summing measured longitudinal and lateral mechanisms. We found that the stratification Dynamics switch between being longitudinally dominated during the middle of ebb and flood tides to being laterally dominated during the tidal transitions. This variability is driven by the interplay between tidally variable lateral density gradients and turbulent mixing. Relatively constant along‐estuary density gradients are differentially advected during flood and ebb tides, resulting in maximal lateral density gradients around tidal transitions. Simultaneous decrease in turbulent mixing at slack tides allows lateral density‐driven exchange to stratify the estuary channel at the slack after flood. At the end of ebb, barotropic forcing drives negatively buoyant shoal waters toward the channel.Plain Language SummarySan Francisco Bay sits within a highly urbanized area. The dense population creates large wastewater effluent resulting in high nutrient levels. Scientists wonder why there have not been annual phytoplankton blooms like those observed in other estuaries with lower nutrient levels. Some have hypothesized it is due to high turbidity levels and tidal breakdown of stratification creating nonideal environments for phytoplankton growth. However, decadal trends show that the estuary is becoming less turbid, and with changes in climate patterns, there is potential for persistent stratification. We observed development of stratification over the ebb tide and destratification in two distinct events as the tide reverses over the flood tide. At the reversal of the tides, water in the shoals exchange with the water in the channel creating a pulse of salty water to the channel at the ebb to flood transition and a pulse of fresh water at the flood to the ebb transition. Destratification occurs in the early flood tide due to a pulse of saline water received from the shoals then due to the advection of less stratified water being pulled to the center channel of the estuary. Finally, stratification is destroyed completely due to longitudinal straining and turbulent mixing.Key PointsVertical stratification in shoal‐channel estuary is characterized by strong intratidal variabilityLateral circulation is a key driver of intratidal stratification Dynamics at tide transitionsTiming and magnitude of longitudinal straining, advection, lateral straining, and advection set intratidal vertical stratification DynamicsPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/151865/1/jgrc23594_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/151865/2/jgrc23594.pd

Parker Maccready - One of the best experts on this subject based on the ideXlab platform.

  • the Estuarine circulation
    Annual Review of Fluid Mechanics, 2014
    Co-Authors: Rockwell W Geyer, Parker Maccready
    Abstract:

    Recent research in estuaries challenges the long-standing paradigm of the gravitationally driven Estuarine circulation. In estuaries with relatively strong tidal forcing and modest buoyancy forcing, the tidal variation in stratification leads to a tidal straining circulation driven by tidal variation in vertical mixing, with a magnitude that may significantly exceed the gravitational circulation. For weakly stratified estuaries, vertical and lateral advection are also important contributors to the tidally driven residual circulation. The apparent contradiction with the conventional paradigm is resolved when the Estuarine parameter space is mapped with respect to a mixing parameter M that is based on the ratio of the tidal timescale to the vertical mixing timescale. Estuaries with high M values exhibit strong tidal nonlinearity, and those with small M values show conventional Estuarine Dynamics. Estuaries with intermediate mixing rates show marked transitions between these regimes at timescales of the spri...

Wei Xiaoyan - One of the best experts on this subject based on the ideXlab platform.

  • Unravelling interactions between asymmetric tidal turbulence, residual circulation and salinity Dynamics in short, periodically weakly stratified estuaries
    'American Meteorological Society', 2021
    Co-Authors: Wei Xiaoyan, Schuttelaars, Henk M., Williams, Megan E., Brown, Jennifer M., Thorne, Peter D., Amoudry, Laurent O.
    Abstract:

    Asymmetric tidal turbulence (ATT) strongly influences Estuarine health and functioning. However, its impact on the three-dimensional Estuarine Dynamics and the feedback of water motion and salinity distribution on ATT remain poorly understood, especially for short estuaries (Estuarine length ≪ tidal wavelength). This study systematically investigates the above-mentioned interactions in a short estuary for the first time, considering periodically weakly stratified conditions. This is done by developing a three-dimensional semi-analytical model (combining perturbation method with finite element method) that allows a dissection of the contributions of different processes to ATT, Estuarine circulation, and salt transport. The generation of ATT is dominated by (i) strain-induced periodic stratification and (ii) asymmetric bottom shear generated turbulence, and their contributions to ATT are different both in amplitude and phase. The magnitude of the residual circulation related to ATT and the eddy viscosity-shear covariance (ESCO) is about half of that of the gravitational circulation (GC) and shows a ‘reversed’ pattern as compared to GC. ATT generated by (i) contributes to an ESCO circulation with a spatial structure similar to GC. This circulation reduces the longitudinal salinity gradients and thus weakens GC. Contrastingly, the ESCO circulation due to (ii) shows patterns opposite to GC and acts to enhance GC. Concerning the salinity Dynamics at steady state, GC and tidal pumping are equally important to salt import, whereas ESCO circulation yields a significant seaward salt transport. These findings highlight the importance of identifying the sources of ATT to understand its impact on Estuarine circulation and salt distribution

  • Unraveling interactions between asymmetric tidal turbulence, residual circulation, and salinity Dynamics in short, periodically weakly stratified estuaries
    'American Meteorological Society', 2021
    Co-Authors: Wei Xiaoyan, Williams, Megan E., Brown, Jennifer M., Thorne, Peter D., Schuttelaars H.m., Amoudry, Laurent O.
    Abstract:

    Asymmetric tidal turbulence (ATT) strongly influences Estuarine health and functioning. However, its impact on the three-dimensional Estuarine Dynamics and the feedback of water motion and salinity distribution on ATT remain poorly understood, especially for short estuaries (Estuarine length ≪ tidal wavelength). This study systematically investigates the abovementioned interactions in a short estuary for the first time, considering periodically weakly stratified conditions. This is done by developing a three-dimensional semi-analytical model (combining perturbation method with finite element method) that allows a dissection of the contributions of different processes to ATT, Estuarine circulation, and salt transport. The generation of ATT is dominated by (i) strain-induced periodic stratification and (ii) asymmetric bottomshear-generated turbulence, and their contributions to ATT are different both in amplitude and phase. The magnitude of the residual circulation related to ATT and the eddy viscosity–shear covariance (ESCO) is about half of that of the gravitational circulation (GC) and shows a ‘‘reversed’’ pattern as compared to GC. ATT generated by strain-induced periodic stratification contributes to an ESCO circulation with a spatial structure similar to GC. This circulation reduces the longitudinal salinity gradients and thus weakens GC. Contrastingly, the ESCO circulation due to asymmetric bottom-sheargenerated turbulence shows patterns opposite to GC and acts to enhance GC. Concerning the salinity Dynamics at steady state, GC and tidal pumping are equally important to salt import, whereas ESCO circulation yields a significant seaward salt transport. These findings highlight the importance of identifying the sources of ATT to understand its impact on Estuarine circulation and salt distribution.Mathematical Physic