Spatial and Temporal Variability of the M2 Internal Tide Generation and Propagation on the Oregon Shelf

2011 ◽  
Vol 41 (11) ◽  
pp. 2037-2062 ◽  
Author(s):  
J. J. Osborne ◽  
A. L. Kurapov ◽  
G. D. Egbert ◽  
P. M. Kosro
Keyword(s):  
Spatial Variability ◽  
Hot Spot ◽  
Time Windows ◽  
Internal Tide ◽  
Tidal Energy ◽  
Horizontal Resolution ◽  
Ocean Modeling ◽  
Spatial And Temporal Variability ◽  
Affect Intensity ◽  
Regional Ocean Modeling System

Abstract A 1-km-horizontal-resolution model based on the Regional Ocean Modeling System is implemented along the Oregon coast to study average characteristics and intermittency of the M2 internal tide during summer upwelling. Wind-driven and tidally driven flows are simulated in combination, using realistic bathymetry, atmospheric forcing, and boundary conditions. The study period is April through August 2002, when mooring velocities are available for comparison. Modeled subtidal and tidal variability on the shelf are in good quantitative agreement with moored velocity time series observations. Depth-integrated baroclinic tidal energy flux (EF), its divergence, and topographic energy conversion (TEC) from the barotropic to baroclinic tide are computed from high-pass-filtered, harmonically analyzed model results in a series of 16-day time windows. Model results reveal several “hot spots” of intensive TEC on the slope. At these locations, TEC is well balanced by EF divergence. Changes in background stratification and currents associated with wind-driven upwelling and downwelling do not appreciably affect TEC hot spot locations but may affect intensity of internal tide generation at those locations. Relatively little internal tide is generated on the shelf. Areas of supercritical slope near the shelf break partially reflect baroclinic tidal energy to deeper water, contributing to spatial variability in seasonally averaged on-shelf EF. Despite significant temporal and spatial variability in the internal tide, the alongshore-integrated flux of internal tide energy onto the Oregon shelf, where it is dissipated, does not vary much with time. Approximately 65% of the M2 baroclinic tidal energy generated on the slope is dissipated there, and the rest is radiated toward the shelf and interior ocean in roughly equal proportions. An experiment with smoother bathymetry reveals that slope-integrated TEC is more sensitive to bathymetric roughness than on-shelf EF.

Combined Effects of Wind-Driven Upwelling and Internal Tide on the Continental Shelf

2010 ◽  
Vol 40 (4) ◽  
pp. 737-756 ◽  
Author(s):  
A. L. Kurapov ◽  
J. S. Allen ◽  
G. D. Egbert
Keyword(s):  
Continental Shelf ◽  
Internal Tide ◽  
Tidal Energy ◽  
Horizontal Velocity ◽  
Internal Tides ◽  
Ocean Modeling ◽  
Vertical Shear ◽  
Momentum Balance ◽  
Surface Boundary ◽  
Regional Ocean Modeling System

Abstract Internal tides on the continental shelf can be intermittent as a result of changing hydrographic conditions associated with wind-driven upwelling. In turn, the internal tide can affect transports associated with upwelling. To study these processes, simulations in an idealized, alongshore uniform setup are performed utilizing the hydrostatic Regional Ocean Modeling System (ROMS) with conditions corresponding, as closely as possible, to the central Oregon shelf. “Wind only” (WO), “tide only” (TO), and “tide and wind” (TW) solutions are compared, utilizing cases with constant upwelling-favorable wind stress as well as with time-variable observed stress. The tide is forced by applying cross-shore barotropic flow at the offshore boundary with intensity sufficient to generate an internal tide with horizontal velocity amplitudes near 0.15 m s−1, corresponding to observed levels. The internal tide affects the subinertial circulation, mostly through the changes in the bottom boundary layer variability, resulting in a larger bottom stress and a weaker depth-averaged alongshore current in the TW case compared to WO. The spatial variability of the cross-shore and vertical volume transport is also affected. Divergence in the Reynolds stress associated with the baroclinic tidal flow contributes to the tidally averaged cross-shore momentum balance. Internal waves cause high-frequency variability in the turbulent kinetic energy in both the bottom and surface boundary layers, causing periodic restratification of the inner shelf in the area of the upwelling front. Increased vertical shear in the horizontal velocity resulting from the superposition of the upwelling jet and the internal tide results in intermittent patches of intensified turbulence in the mid–water column. Variability in stratification associated with upwelling can affect not only the propagation of the internal tide on the shelf, but also the barotropic-to-baroclinic energy conversion on the continental slope, in this case changing the classification of the slope from nearly critical to supercritical such that less barotropic tidal energy is converted to baroclinic and a larger fraction of the baroclinic energy is radiated into the open ocean.

Scattering of internal tide energy to super-tidal frequencies in global HYCOM 

2021 ◽  
Author(s):  
Miguel Solano ◽  
Maarten Buijsman
Keyword(s):  
Internal Tide ◽  
Tidal Energy ◽  
Horizontal Resolution ◽  
Internal Tides ◽  
Numerical Dispersion ◽  
Global Ocean ◽  
Wave Interactions ◽  
Continental Shelves ◽  
Lee Wave ◽  
Ocean Models

<p>Energy decay in realistically forced global ocean models has been mostly studied in the diurnal and semi-diurnal tidal bands and it is unclear how much of the tidal energy in these bands is scattered to higher frequencies. Global ocean models and satellite altimetry have shown that low-mode internal tides can propagate thousands of kilometers from their generation sites before being dissipated in the ocean interior but their pathway to dissipation is obscured due to lee-wave breaking at generation, wave-wave interactions, topographic scattering, shearing instabilities and shoaling on continental shelves. Internal tides from some generation sites, such as the Amazon shelf and the Nicobar and Andaman island chain, have large amounts of energy resulting in a steepening of the internal waves into solitary wave trains due to non-hydrostatic dispersion. In HYCOM, a hydrostatic model, this process is partially simulated by numerical dispersion. However, it is yet unknown how the dissipation of internal tides is affected by the numerical dispersion in hydrostatic models. In this study we use the method of vertical modes and rotary spectra to quantify the scattering of internal tides to higher-frequencies and analyze the dissipation processes in global HYCOM simulations with 4-km horizontal resolution.</p>

scholarly journals The Hybrid Kelvin–Edge Wave and Its Role in Tidal Dynamics

2010 ◽  
Vol 40 (12) ◽  
pp. 2757-2767 ◽  
Author(s):  
Ziming Ke ◽  
Alexander E. Yankovsky
Keyword(s):  
Group Velocity ◽  
Wave Energy ◽  
Numerical Experiments ◽  
Tidal Energy ◽  
Ocean Modeling ◽  
Edge Wave ◽  
Kelvin Wave ◽  
Regional Ocean Modeling System ◽  
Offshore Wave ◽  
Zero Group

Abstract A full set of long waves trapped in the coastal ocean over a variable topography includes a zero (fundamental) mode propagating with the coast on its right (left) in the Northern (Southern) Hemisphere. This zero mode resembles a Kelvin wave at lower frequencies and an edge wave (Stokes mode) at higher frequencies. At the intermediate frequencies this mode becomes a hybrid Kelvin–edge wave (HKEW), as both rotational effects and the variable depth become important. Furthermore, the group velocity of this hybrid mode becomes very small or even zero depending on shelf width. It is found that in midlatitudes a zero group velocity occurs at semidiurnal (tidal) frequencies over wide (∼300 km), gently sloping shelves. This notion motivated numerical experiments using the Regional Ocean Modeling System in which the incident HKEW with a semidiurnal period propagates over a wide shelf and encounters a narrowing shelf so that the group velocity becomes zero at some alongshore location. The numerical experiments have demonstrated that the wave energy increases upstream of this location as a result of the energy flux convergence while farther downstream the wave amplitude is substantially reduced. Instead of propagating alongshore, the wave energy radiates offshore in the form of Poincaré modes. Thus, it is concluded that the shelf areas where the group velocity of the HKEW becomes zero are characterized by an increased tidal amplitude and (consequently) high tidal energy dissipation, and by offshore wave energy radiation. This behavior is qualitatively consistent with the dynamics of semidiurnal tides on wide shelves narrowing in the direction of tidal wave propagation, including the Patagonia shelf and the South China Sea.

scholarly journals Spatial and temporal variability in nutrients and carbon uptake during 2004 and 2005 in the eastern equatorial Pacific Ocean

2012 ◽  
Vol 9 (11) ◽  
pp. 4369-4383 ◽  
Author(s):  
A. P. Palacz ◽  
F. Chai
Keyword(s):  
Temporal Variability ◽  
Remote Sensing Data ◽  
Zooplankton Biomass ◽  
Equatorial Pacific ◽  
Ocean Modeling ◽  
Spatial And Temporal Variability ◽  
Equatorial Pacific Ocean ◽  
Regional Ocean Modeling System ◽  
Eastern Equatorial Pacific ◽  
Physical Interactions

Abstract. The eastern equatorial Pacific plays a~great role in the global carbon budget due to its enhanced biological productivity linked to the equatorial upwelling. However, as confirmed by the Equatorial Biocomplexity cruises in 2004 and 2005, nutrient upwelling supply varies strongly, partly due to the tropical instability waves (TIWs). The aim of this study was to examine patterns of spatial and temporal variability in the biological uptake of NO3, Si(OH)4 and carbon in this region, and to evaluate the role of biological and physical interactions controlling this variability over seasonal and intraseasonal time scales. Here, high resolution Pacific ROMS–CoSiNE (Regional Ocean Modeling System–Carbon, Silicon, Nitrogen Ecosystem) model results were evaluated with in situ and remote sensing data. The results of model–data comparison revealed a good agreement in domain-average hydrographic and biological rate estimates, and patterns of spatio-temporal variability in primary productivity. We confirmed that TIWs have the potential to enhance phytoplankton biomass through an increased supply of nutrients and elevated local and instantaneous phytoplankton nutrient uptake as opposed to only advecting biomass. Furthermore, we concluded that initial biological conditions (e.g., zooplankton biomass) may play an important additional constraint on biological responses, in particular of large phytoplankton such as diatoms, to TIW-induced perturbations in the physical and biogeochemical fields and fluxes. In order to fully resolve the complexity of biological and physical interactions in the eastern equatorial Pacific, we recommended improving CoSiNE and other models by introducing more phytoplankton groups, variable Redfield and carbon to chlorophyll ratios, as well as resolving the Fe–Si co-limitation of phytoplankton growth.

scholarly journals Properties and evolution of a submesoscale cyclonic spiral

2021 ◽  
Author(s):  
Reiner Onken ◽  
Burkard Baschek
Keyword(s):  
Extreme Values ◽  
Euphotic Zone ◽  
Horizontal Resolution ◽  
Surface Flow ◽  
Ocean Modeling ◽  
Vortex Center ◽  
Regional Ocean Modeling System ◽  
Near Surface ◽  
Surface Drifters ◽  
Radial Outflow

Abstract. The evolution of a submesoscale cyclonic spiral of 1 km in diameter is simulated with ROMS (Regional Ocean Modeling System) using 33.3 m horizontal resolution in a triple-nested configuration. The generation of the spiral starts from a dense filament that is rolled into a vortex and detaches from the filament. During spin-up, extreme values are attained by various quantities, that are organized in single-arm and multi-arm spirals. The spin-down starts when the cyclone separates from the filament. At the same time, the horizontal speed develops a dipole-like pattern and isotachs form closed contours around the vortex center. The amplitudes of most quantities decrease significantly, but the instantaneous vertical velocity w exhibits high-frequency oscillations and more pronounced extremes than during spin-up. The oscillations are due to vortex Rossby waves (VRWs), that circle the eddy counterclockwise and generate multi-arm spirals with alternating signs by means of azimuthal vorticity advection. Experiments with virtual surface drifters and isopycnal floats indicate downwelling everywhere near the surface. The downwelling is most intense in the center of the spiral at all depth levels, leading to a radial outflow in the thermocline and weak upwelling at the periphery. This overturning circulation is driven by convergent near-surface flow and associated subduction of isopycnals. While the downwelling in the center may support the export of particulate organic carbon from the mixed layer into the main thermocline, the upwelling at the periphery effectuates an upward isopycnal transport of nutrients, enhancing the growth of phytoplankton in the euphotic zone.

scholarly journals Very high-resolution modelling of submesoscale turbulent patterns and processes in the Baltic Sea

2019 ◽  
Author(s):  
Reiner Onken ◽  
Burkard Baschek ◽  
Ingrid M. Angel-Benavides
Keyword(s):  
Baltic Sea ◽  
Horizontal Resolution ◽  
Ocean Modeling ◽  
Regional Ocean Modeling System ◽  
The Baltic Sea ◽  
Operational Model ◽  
The Baltic ◽  
Patterns And Processes ◽  
Comparison Of The Results ◽  
Good Agreement

Abstract. In order to simulate submesoscale turbulent patterns and processes (STPPs) and to analyse their properties and dynamics, the Regional Ocean Modeling System (ROMS) is applied to a subregion of the Baltic Sea around the island of Bornholm. The modeled STPPs provide an aid for the interpretation of observations that were taken during the Expedition Clockwork Ocean in the same region in June 2016. To create a realistic mesoscale and submesoscale environment, ROMS with 500-m horizontal resolution is one-way nested into an existing operational model. The comparison of the results with satellite images shows good agreement. STPPs with horizontal scales

scholarly journals Numerical and Analytical Estimates of M2 Tidal Conversion at Steep Oceanic Ridges

2006 ◽  
Vol 36 (6) ◽  
pp. 1072-1084 ◽  
Author(s):  
Emanuele Di Lorenzo ◽  
William R. Young ◽  
Stefan Llewellyn Smith
Keyword(s):  
Internal Tide ◽  
Ocean Model ◽  
Internal Tides ◽  
Ocean Modeling ◽  
Numerical Calculations ◽  
Density Gradients ◽  
Regional Ocean Modeling System ◽  
Supercritical Regime ◽  
Vertical Coordinate ◽  
Topographic Slope

Abstract Numerical calculations of the rate at which energy is converted from the external to internal tides at steep oceanic ridges are compared with estimates from analytic theories. The numerical calculations are performed using a hydrostatic primitive equation ocean model that uses a generalized s-coordinate system as the vertical coordinate. The model [Regional Ocean Modeling System (ROMS)] estimates of conversion compare well with inviscid and nondiffusive theory in the sub- and supercritical regimes and are insensitive to the strength of viscosity and diffusivity. In the supercritical regime, the nondissipative analytic solution is singular all along the internal tide beams. Because of dissipation the ROMS solutions are nonsingular, although the density gradients are strongly enhanced along the beams. The agreement between model and theory indicates that the prominent singularities in the inviscid solution do not compromise the estimates of tidal conversion and that the linearization used in deriving the analytical estimates is valid. As the model beams radiate from the generation site the density gradients are further reduced and up to 20% of the energy is lost by model dissipation (vertical viscosity and diffusion) within 200 km of the ridge. As a result of the analysis of the numerical calculations the authors also report on the sensitivity of tidal conversion to topographic misrepresentation errors. These errors are associated with inadequate resolution of the topographic features and with the smoothing required to run the ocean model. In regions of steep topographic slope (i.e., the Hawaiian Ridge) these errors, if not properly accounted for, may lead to an underestimate of the true conversion rate up to 50%.

scholarly journals The Seasonality of Convective Events in the Labrador Sea

2014 ◽  
Vol 27 (17) ◽  
pp. 6456-6471 ◽  
Author(s):  
Hao Luo ◽  
Annalisa Bracco ◽  
Fan Zhang
Keyword(s):  
Large Scale ◽  
Current System ◽  
Horizontal Resolution ◽  
Surface Heat ◽  
Heat Fluxes ◽  
Ocean Modeling ◽  
Labrador Sea ◽  
Boundary Current ◽  
Regional Ocean Modeling System ◽  
Surface Heat Fluxes

Abstract Modeling deep convection is a key challenge for climate science. Here two simulations of the Labrador Sea circulation obtained with the Regional Ocean Modeling System (ROMS) run at a horizontal resolution of 7.5 km are used to characterize the response of convection to atmospheric forcing and its seasonal variability over the period 1980–2009. The integrations compare well with the sparse observations available. The modeled convection varies in three key aspects over the 30 years considered. First, its magnitude changes greatly at decadal scales. This aspect is supported by the in situ observations. Second, the initiation and peak of convection (i.e., initiation and maximum) shift by 2–3 weeks between strong and weak convective years. Third, the duration of convection varies by approximately one month between strong and weak years. The last two changes are associated with the variability of the time-integrated surface heat fluxes over the Labrador Sea during winter and spring, while the first results from changes in both atmospheric heat fluxes and oceanic conditions through the lateral inflow of warm Irminger Water from the boundary current system to the basin interior. Changes in surface heat fluxes over the convective region are linked to large-scale modes of variability, the North Atlantic Oscillation and Arctic Oscillation. Implications for modeling the climate variability of the Labrador basin are discussed.

Internal tide structure and temporal variability on the reflective continental slope of southeastern Tasmania.

2020 ◽  
Author(s):  
Olavo B. Marques ◽  
Matthew H. Alford ◽  
Rob Pinkel ◽  
Jennifer A. MacKinnon ◽  
Jody M. Klymak ◽  
...  
Keyword(s):  
Continental Slope ◽  
Standing Wave ◽  
Temporal Variability ◽  
Internal Tide ◽  
Tidal Energy ◽  
Wave Pattern ◽  
Internal Tides ◽  
Small Scale ◽  
Spatial And Temporal Variability ◽  
Standing Wave Pattern

AbstractMode-1 internal tides can propagate far away from their generation sites, but how and where their energy is dissipated is not well understood. One example is the semidiurnal internal tide generated south of New Zealand, which propagates over a thousand kilometers before impinging on the continental slope of Tasmania. In-situ observations and model results from a recent process-study experiment are used to characterize the spatial and temporal variability of the internal tide on the southeastern Tasman slope, where previous studies have quantified large reflectivity. As expected, a standing wave pattern broadly explains the cross-slope and vertical structure of the observed internal tide. However, model and observations highlight several additional features of the internal tide on the continental slope. The standing wave pattern on the sloping bottom as well as small-scale bathymetric corrugations lead to bottom-enhanced tidal energy. Over the corrugations, larger tidal currents and isopycnal displacements are observed along the trough as opposed to the crest. Despite the long-range propagation of the internal tide, most of the variability in energy density on the slope is accounted by the spring-neap cycle. However, the timing of the semidiurnal spring tides is not consistent with a single remote wave and is instead explained by the complex interference between remote and local tides on the Tasman slope. These observations suggest that identifying the multiple waves in an interference pattern and their interaction with small-scale topography is an important step in modeling internal energy and dissipation.

scholarly journals The Effect of Atmospheric Forcing Resolution on Delivery of Ocean Heat to the Antarctic Floating Ice Shelves*,+

2015 ◽  
Vol 28 (15) ◽  
pp. 6067-6085 ◽  
Author(s):  
Michael S. Dinniman ◽  
John M. Klinck ◽  
Le-Sheng Bai ◽  
David H. Bromwich ◽  
Keith M. Hines ◽  
...  
Keyword(s):  
Horizontal Resolution ◽  
Ocean Modeling ◽  
Atmospheric Forcing ◽  
Regional Ocean Modeling System ◽  
Ice Shelf ◽  
Ice Shelves ◽  
Air Temperatures ◽  
Continental Shelves ◽  
Iceberg Calving ◽  
The Antarctic

Abstract Oceanic melting at the base of the floating Antarctic ice shelves is now thought to be a more significant cause of mass loss for the Antarctic ice sheet than iceberg calving. In this study, a 10-km horizontal-resolution circum-Antarctic ocean–sea ice–ice shelf model [based on the Regional Ocean Modeling System (ROMS)] is used to study the delivery of ocean heat to the base of the ice shelves. The atmospheric forcing comes from the ERA-Interim reanalysis (~80-km resolution) and from simulations using the polar-optimized Weather Research and Forecasting Model (30-km resolution), where the upper atmosphere was relaxed to the ERA-Interim reanalysis. The modeled total basal ice shelf melt is low compared to observational estimates but increases by 14% with the higher-resolution winds and just 3% with both the higher-resolution winds and atmospheric surface temperatures. The higher-resolution winds lead to more heat being delivered to the ice shelf cavities from the adjacent ocean and an increase in the efficiency of heat transfer between the water and the ice. The higher-resolution winds also lead to changes in the heat delivered from the open ocean to the continental shelves as well as changes in the heat lost to the atmosphere over the shelves, and the sign of these changes varies regionally. Addition of the higher-resolution temperatures to the winds results in lowering, primarily during summer, the wind-driven increase in heat advected into the ice shelf cavities due to colder summer air temperatures near the coast.

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