Issues and progress in the prediction of ocean submesoscale features and internal waves

Duda, Timothy F.; Zhang, Weifeng G.; Helfrich, Karl R.; Newhall, Arthur E.; Lin, Ying‐Tsong; Lynch, James F.; Lermusiaux, Pierre F. J.; Haley, Patrick J.; Wilkin, John

doi:10.1109/oceans.2014.7003282

Cited by 13 publications

(11 citation statements)

References 40 publications

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“…Finite-amplitude nonlinear effects, which we neglect in this subsection, are important where internal tides produce strong currents (e.g., the South China Sea; Alford et al 2015) and/or small-scale variability (Zhang and Duda 2013;Duda et al 2014). Ignoring finiteamplitude nonlinear terms, the inviscid, hydrostatic, Boussinesq equations of motion are…”

Section: A Unforced and Linear Dynamicsmentioning

confidence: 99%

A Coupled-Mode Shallow-Water Model for Tidal Analysis: Internal Tide Reflection and Refraction by the Gulf Stream

Kelly

Lermusiaux

Duda

et al. 2016

Journal of Physical Oceanography

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A hydrostatic, coupled-mode, shallow-water model (CSW) is described and used to diagnose and simulate tidal dynamics in the greater Mid-Atlantic Bight region. The reduced-physics model incorporates realistic stratification and topography, internal tide forcing from a priori estimates of the surface tide, and advection terms that describe first-order interactions of internal tides with slowly varying mean flow and mean buoyancy fields and their respective shear. The model is validated via comparisons with semianalytic models and nonlinear primitive equation models in several idealized and realistic simulations that include internal tide interactions with topography and mean flows. Then, 24 simulations of internal tide generation and propagation in the greater Mid-Atlantic Bight region are used to diagnose significant internal tide interactions with the Gulf Stream. The simulations indicate that locally generated mode-one internal tides refract and/or reflect at the Gulf Stream. The redirected internal tides often reappear at the shelf break, where their onshore energy fluxes are intermittent (i.e., noncoherent with surface tide) because meanders in the Gulf Stream alter their precise location, phase, and amplitude. These results provide an explanation for anomalous onshore energy fluxes that were previously observed at the New Jersey shelf break and linked to the irregular generation of nonlinear internal waves.

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Section: A Unforced and Linear Dynamicsmentioning

confidence: 99%

A Coupled-Mode Shallow-Water Model for Tidal Analysis: Internal Tide Reflection and Refraction by the Gulf Stream

Kelly

Lermusiaux

Duda

et al. 2016

Journal of Physical Oceanography

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“…Temporal and spatial variability of stratification, complex bathymetry, the strength of inertial oscillations, geostrophic currents, and mesoscale eddies have all been shown to interact with internal tide generation and propagation and contribute to their unpredictability (e.g., Huang et al, ; Kerry et al, , ; Rainville & Pinkel, ; Zilberman et al, ; Zaron & Egbert, ). In addition, interference from multiple internal tide generation sites and horizontal plane propagation effects may also lead to unpredictability (e.g., Buijsman et al, ; Duda et al, ; Kurapov et al, ). In coastal regions, small‐scale bathymetric variations, stratification variability from wind‐driven processes, buoyancy input from riverine runoff, and shoaling remotely generated internal tides can modify local internal tide generation and propagation (e.g., Martini et al, ; Nash et al, ; Nash, Kelly, et al, ).…”

Section: Introductionmentioning

confidence: 99%

Coastal Semidiurnal Internal Tidal Incoherence in the Santa Maria Basin, California: Observations and Model Simulations

et al. 2019

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A series of five realistic, nested, hydrostatic numerical ocean model simulations are used to study semidiurnal internal tide generation and propagation from the continental slope, through the shelf break and to the midshelf adjacent to Point Sal, CA. The statistics of modeled temperature and horizontal velocity fluctuations are compared to midshelf observations (30‐ to 50‐m water depth). Time‐ and frequency‐domain methods are used to decompose internal tides into components that are coherent and incoherent with the barotropic tide, and the incoherence fraction is 0.5–0.7 at the midshelf locations in both the realistic model and observations. In contrast, the incoherence fraction is at the most 0.45 for a simulation with idealized stratification, and neither atmospheric forcing nor mesoscale currents. Negligible conversion from barotropic to baroclinic energy occurs at the local shelf break. Instead, the dominant internal tide energy sources are regions of small‐scale near‐critical to supercritical bathymetry on the Santa Lucia escarpment (1,000–3,000 m), 70–80 km from the continental shelf. Near the generation region, semidiurnal baroclinic energy is primarily coherent and rapidly decays adjacent to the shelf break. In the realistically forced model, incoherent energy is less than 10% in the generation region, with a steady increase in incoherence fraction from the continental slope to the midshelf. Backward ray tracing from the midshelf to the Santa Lucia escarpment identifies multiple energy pathways potentially leading to spatial interference. As internal tides shoal on the predominantly subcritical slope/shelf system, temporally variable stratification and Doppler shifting from mesoscale and submesoscale features appear equally important in leading to the loss of coherence.

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“…Understanding and working around these limits of modern DA models is at the forefront of predictive ocean acoustics, for example, in cataloging uncertainty (Lermusiaux et al 2010). Note that methods to infill DA-modeled areas with nonhydrostatic internal waves are currently being examined for accuracy (Duda et al 2014b). …”

Section: Deterministic Statistical and Analytic Feature Modelsmentioning

confidence: 99%

Modeling and Forecasting Ocean Acoustic Conditions

Duda¹

2017

j mar res

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Modeling acoustic conditions in an oceanic environment is a multiple-step process. The environmental conditions (features) in the area first must be measured or estimated; relevant features include seabed geometry, seabed composition, and four-dimensionally (4D) variable sound-speed and density variations related to evolving or wave motions. Often the dynamical wave modeling depends on first obtaining correct seabed and mean stratification conditions (for example, nonlinear internal wave modeling). Next, this information must be included in sound propagation modeling. A selection of the many methods and tools available for these tasks are described, with a focus on modeling sounds of 20 to 1000 Hz propagating through water-column features that are time-dependent and variable in three dimensions (i.e., 4D variable). An example of a 3D parabolic equation acoustic calculation shows how variability caused by evolving internal tidal waves affects sound propagation. Different propagation and scattering regimes are discussed, including the theoretically delineated weak scattering and strong scattering regimes, as well as the empirically examined regime found in nonlinear internal waves. The histories and the current state of our oceanographic knowledge (the input to acoustic modeling) and of our ability to effectively model complex acoustic conditions are discussed. Example acoustic simulation applications are also discussed; these are ocean acoustic tomography, coherence prediction, and signal-to-noise ratio prediction. Types of ocean models and acoustic models and how they are interfaced are also examined. These include deterministic, statistical analytic feature models.

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Issues and progress in the prediction of ocean submesoscale features and internal waves

Cited by 13 publications

References 40 publications

A Coupled-Mode Shallow-Water Model for Tidal Analysis: Internal Tide Reflection and Refraction by the Gulf Stream

A Coupled-Mode Shallow-Water Model for Tidal Analysis: Internal Tide Reflection and Refraction by the Gulf Stream

Coastal Semidiurnal Internal Tidal Incoherence in the Santa Maria Basin, California: Observations and Model Simulations

Modeling and Forecasting Ocean Acoustic Conditions

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