scholarly journals Enhanced internal tidal mixing in the Philippine Sea mesoscale environment

2021 ◽  
Author(s):  
Jia You ◽  
Zhenhua Xu ◽  
Qun Li ◽  
Robin Robertson ◽  
Peiwen Zhang ◽  
...  
Keyword(s):  
Internal Tides ◽  
Tidal Mixing ◽  
Spatial Inhomogeneity ◽  
Inertial Waves ◽  
Diapycnal Mixing ◽  
Mixing Properties ◽  
Philippine Sea ◽  
Source Data ◽  
Wind Mixing ◽  
Mesoscale Processes

Abstract. Turbulent mixing in the ocean interior is mainly contributed by internal wave breaking; however, the mixing properties and the modulation effects of mesoscale environmental factors are not well-known. Here, the spatially inhomogeneous and seasonally variable diapycnal diffusivities in the upper Philippine Sea were estimated from ARGO float data using a strain-based finescale parameterization. Based on a coordinated analysis of multi-source data, we found that the driving processes for diapycnal diffusivities mainly included the near-inertial waves and internal tides. Mesoscale features were important in intensifying the mixing and modulating its spatial pattern. One interesting finding was that, besides near-inertial waves, internal tides also contributed significant diapycnal mixing for the upper Philippine Sea. The seasonal cycles of diapycnal diffusivities and their contributors differed zonally. In the mid-latitudes, wind-mixing dominated and was strongest in winter and weakest in summer. In contrast, tidal-mixing was more predominant in the lower-latitudes and had no apparent seasonal variability. Furthermore, we provide evidence that the mesoscale environment in the Philippine Sea played a significant role in regulating the intensity and shaping the spatial inhomogeneity of the internal tidal mixing. The magnitudes of internal tidal mixing was greatly elevated in regions of energetic mesoscale processes. The anticyclonic mesoscale features were found to enhance diapycnal mixing more significantly than did cyclonic ones.

scholarly journals Enhanced internal tidal mixing in the Philippine Sea mesoscale environment

2021 ◽  
Vol 28 (2) ◽  
pp. 271-284
Author(s):  
Jia You ◽  
Zhenhua Xu ◽  
Qun Li ◽  
Robin Robertson ◽  
Peiwen Zhang ◽  
...  
Keyword(s):  
Internal Tides ◽  
Tidal Mixing ◽  
Spatial Inhomogeneity ◽  
Inertial Waves ◽  
Diapycnal Mixing ◽  
Mixing Properties ◽  
Philippine Sea ◽  
Source Data ◽  
Wind Mixing ◽  
Mesoscale Processes

Abstract. Turbulent mixing in the ocean interior is mainly attributed to internal wave breaking; however, the mixing properties and the modulation effects of mesoscale environmental factors are not well known. Here, the spatially inhomogeneous and seasonally variable diapycnal diffusivities in the upper Philippine Sea were estimated from Argo float data using a strain-based, fine-scale parameterization. Based on a coordinated analysis of multi-source data, we found that the driving processes for diapycnal diffusivities mainly included the near-inertial waves and internal tides. Mesoscale features were important in intensifying the mixing and modulating of its spatial pattern. An interesting finding was that, besides near-inertial waves, internal tides also contributed significant diapycnal mixing in the upper Philippine Sea. The seasonal cycles of diapycnal diffusivities and their contributors differed zonally. In the midlatitudes, wind mixing dominated and was strongest in winter and weakest in summer. In contrast, tidal mixing was more predominant in the lower latitudes and had no apparent seasonal variability. Furthermore, we provide evidence that the mesoscale environment in the Philippine Sea played a significant role in regulating the intensity and shaping the spatial inhomogeneity of the internal tidal mixing. The magnitudes of internal tidal mixing were greatly elevated in regions of energetic mesoscale processes. Anticyclonic mesoscale features were found to enhance diapycnal mixing more significantly than cyclonic ones.

Enhanced internal tidal mixing in the Philippine Sea mesoscale environment

2021 ◽  
Author(s):  
Jia You ◽  
Zhenhua Xu ◽  
Qun Li ◽  
Peiwen Zhang
Keyword(s):  
Internal Tides ◽  
Tidal Mixing ◽  
Spatial Inhomogeneity ◽  
Inertial Waves ◽  
Diapycnal Mixing ◽  
Mixing Properties ◽  
Philippine Sea ◽  
Source Data ◽  
Wind Mixing ◽  
Mesoscale Processes

<p>Turbulent mixing in the ocean interior is mainly contributed by internal wave breaking; however, the mixing properties and the modulation effects of mesoscale environmental factors are not well-known. Here, the spatially inhomogeneous and seasonally variable diapycnal diffusivities in the upper Philippine Sea were estimated from ARGO float data using a strain-based finescale parameterization. Based on a coordinated analysis of multi-source data, we found that the driving processes for diapycnal diffusivities mainly included the near-inertial waves and internal tides. Mesoscale features were important in intensifying the mixing and modulating its spatial pattern. One interesting finding was that, besides near-inertial waves, internal tides also contributed significant diapycnal mixing for the upper Philippine Sea. The seasonal cycles of diapycnal diffusivities and their contributors differed zonally. In the mid-latitudes, wind-mixing dominated and was strongest in winter and weakest in summer. In contrast, tidal-mixing was more predominant in the lower-latitudes and had no apparent seasonal variability. Furthermore, we provide evidence that the mesoscale environment in the Philippine Sea played a significant role in regulating the intensity and shaping the spatial inhomogeneity of the internal tidal mixing. The magnitudes of internal tidal mixing was greatly elevated in regions of energetic mesoscale processes. The anticyclonic mesoscale features were found to enhance diapycnal mixing more significantly than did cyclonic ones.</p>

scholarly journals A parameterization of local and remote tidal mixing

2020 ◽  
Author(s):  
Casimir de Lavergne ◽  
Clément Vic ◽  
Gurvan Madec ◽  
Fabien Roquet ◽  
Amy Waterhouse ◽  
...  
Keyword(s):  
Vertical Mixing ◽  
Three Dimensional ◽  
Internal Tide ◽  
Ocean Model ◽  
Internal Tides ◽  
Tidal Mixing ◽  
Global Ocean ◽  
Energy Conserving ◽  
Energy Constrained ◽  
Lagrangian Tracking

<p>Vertical mixing is often regarded as the Achilles’ heel of ocean models. In particular, few models include a comprehensive and energy-constrained parameterization of mixing by internal ocean tides. Here, we present an energy-conserving mixing scheme which accounts for the local breaking of high-mode internal tides and the distant dissipation of low-mode internal tides. The scheme relies on four static two-dimensional maps of internal tide dissipation, constructed using mode-by-mode Lagrangian tracking of energy beams from sources to sinks. Each map is associated with a distinct dissipative process and a corresponding vertical structure. Applied to an observational climatology of stratification, the scheme produces a global three-dimensional map of dissipation which compares well with available microstructure observations and with upper-ocean finestructure mixing estimates. Implemented in the NEMO global ocean model, the scheme improves the representation of deep water-mass transformation and obviates the need for a constant background diffusivity.</p>

scholarly journals Long‐Range Radiation and Interference Pattern of Multisource M 2 Internal Tides in the Philippine Sea

2018 ◽  
Vol 123 (8) ◽  
pp. 5091-5112 ◽  
Author(s):  
Yang Wang ◽  
Zhenhua Xu ◽  
Baoshu Yin ◽  
Yijun Hou ◽  
Hang Chang
Keyword(s):  
Long Range ◽  
Interference Pattern ◽  
Internal Tides ◽  
Philippine Sea

scholarly journals A Simple Parameterization of Turbulent Tidal Mixing near Supercritical Topography

2010 ◽  
Vol 40 (9) ◽  
pp. 2059-2074 ◽  
Author(s):  
Jody M. Klymak ◽  
Sonya Legg ◽  
Robert Pinkel
Keyword(s):  
Internal Wave ◽  
Water Column ◽  
Numerical Models ◽  
Tidal Flow ◽  
Internal Tides ◽  
Tidal Mixing ◽  
Knife Edge ◽  
Wave Interactions ◽  
Tidal Dissipation ◽  
Midocean Ridges

Abstract A simple parameterization for tidal dissipation near supercritical topography, designed to be applied at deep midocean ridges, is presented. In this parameterization, radiation of internal tides is quantified using a linear knife-edge model. Vertical internal wave modes that have nonrotating phase speeds slower than the tidal advection speed are assumed to dissipate locally, primarily because of hydraulic effects near the ridge crest. Evidence for high modes being dissipated is given in idealized numerical models of tidal flow over a Gaussian ridge. These idealized models also give guidance for where in the water column the predicted dissipation should be placed. The dissipation recipe holds if the Coriolis frequency f is varied, as long as hN/W ≫ f, where N is the stratification, h is the topographic height, and W is a width scale. This parameterization is not applicable to shallower topography, which has significantly more dissipation because near-critical processes dominate the observed turbulence. The parameterization compares well against simulations of tidal dissipation at the Kauai ridge but predicts less dissipation than estimated from observations of the full Hawaiian ridge, perhaps because of unparameterized wave–wave interactions.

Internal-Wave-Driven Mixing: Global Geography and Budgets

2017 ◽  
Vol 47 (6) ◽  
pp. 1325-1345 ◽  
Author(s):  
Eric Kunze
Keyword(s):  
Internal Wave ◽  
Internal Tide ◽  
Internal Tides ◽  
Tidal Mixing ◽  
Linear Wave ◽  
Power Sources ◽  
The North ◽  
Dissipation Rates ◽  
Thickness Variability ◽  
Significant Pathway

AbstractInternal-wave-driven dissipation rates ε and diapycnal diffusivities K are inferred globally using a finescale parameterization based on vertical strain applied to ~30 000 hydrographic casts. Global dissipations are 2.0 ± 0.6 TW, consistent with internal wave power sources of 2.1 ± 0.7 TW from tides and wind. Vertically integrated dissipation rates vary by three to four orders of magnitude with elevated values over abrupt topography in the western Indian and Pacific as well as midocean slow spreading ridges, consistent with internal tide sources. But dependence on bottom forcing is much weaker than linear wave generation theory, pointing to horizontal dispersion by internal waves and relatively little local dissipation when forcing is strong. Stratified turbulent bottom boundary layer thickness variability is not consistent with OGCM parameterizations of tidal mixing. Average diffusivities K = (0.3–0.4) × 10−4 m2 s−1 depend only weakly on depth, indicating that ε = KN2/γ scales as N2 such that the bulk of the dissipation is in the pycnocline and less than 0.08-TW dissipation below 2000-m depth. Average diffusivities K approach 10−4 m2 s−1 in the bottom 500 meters above bottom (mab) in height above bottom coordinates with a 2000-m e-folding scale. Average dissipation rates ε are 10−9 W kg−1 within 500 mab then diminish to background deep values of 0.15 × 10−9 W kg−1 by 1000 mab. No incontrovertible support is found for high dissipation rates in Antarctic Circumpolar Currents or parametric subharmonic instability being a significant pathway to elevated dissipation rates for semidiurnal or diurnal internal tides equatorward of 28° and 14° latitudes, respectively, although elevated K is found about 30° latitude in the North and South Pacific.

scholarly journals S2P3-R (v1.0): a framework for efficient regional modelling of physical and biological structures and processes in shelf seas

2015 ◽  
Vol 8 (10) ◽  
pp. 3163-3178 ◽  
Author(s):  
R. Marsh ◽  
A. E. Hickman ◽  
J. Sharples
Keyword(s):  
Internal Tides ◽  
Tidal Mixing ◽  
Regional Modelling ◽  
Biological Phenomena ◽  
Horizontal Variation ◽  
Shelf Seas ◽  
Shelf Sea ◽  
Practical Tool ◽  
Regional Adaptation ◽  
Eddy Fluxes

Abstract. An established one-dimensional (1-D) model of Shelf Sea Physics and Primary Production (S2P3) is adapted for flexible use in selected regional settings over selected periods of time. This Regional adaptation of S2P3, the S2P3-R framework (v1.0), can be efficiently used to investigate physical and biological phenomena in shelf seas that are strongly controlled by vertical processes. These include spring blooms that follow the onset of stratification, tidal mixing fronts that seasonally develop at boundaries between mixed and stratified water, and sub-surface chlorophyll maxima that persist throughout summer. While not representing 3-D processes, S2P3-R reveals the horizontal variation of the key 1-D (vertical) processes. S2P3-R should therefore only be used in regions where horizontal processes – including mean flows, eddy fluxes and internal tides – are known to exert a weak influence in comparison with vertical processes. In such cases, S2P3-R may be used as a highly versatile research tool, alongside more complex and computationally expensive models. In undergraduate oceanography modules and research projects, the model serves as an effective practical tool for linking theory and field observations. Three different regional configurations of S2P3-R are described, illustrating a range of diagnostics, evaluated where practical with observations. The model can be forced with daily meteorological variables for any selected year in the reanalysis era (1948 onwards). Example simulations illustrate the considerable extent of synoptic-to-interannual variability in the physics and biology of shelf seas. In discussion, the present limitations of S2P3-R are emphasised, and future developments are outlined.

scholarly journals Focusing of internal tides by near‐inertial waves

2017 ◽  
Vol 44 (5) ◽  
pp. 2398-2406 ◽  
Author(s):  
Y. Cuypers ◽  
P. Bouruet‐Aubertot ◽  
J. Vialard ◽  
M. J. McPhaden
Keyword(s):  
Internal Tides ◽  
Inertial Waves

scholarly journals The Impact of Subtidal Circulation on Internal Tide Generation and Propagation in the Philippine Sea

2014 ◽  
Vol 44 (5) ◽  
pp. 1386-1405 ◽  
Author(s):  
Colette G. Kerry ◽  
Brian S. Powell ◽  
Glenn S. Carter
Keyword(s):  
Energy Levels ◽  
Internal Tide ◽  
Equation Model ◽  
Luzon Strait ◽  
Internal Tides ◽  
Philippine Sea ◽  
Subtidal Circulation ◽  
Tide Propagation ◽  
Mariana Arc ◽  
The Impact

Abstract This study examines the effects of the subtidal circulation on the generation and propagation of the M2 internal tide in the Philippine Sea using a primitive equation model. Barotropic to baroclinic conversion at the Luzon Strait is found to vary due to the background circulation changes over the generation site and the changing influence of remotely generated internal tides from the Mariana Arc. The varying effect of remotely generated waves results from both changing generation energy levels at the Mariana Arc and variability in the propagation of the internal tides across the Philippine Sea. The magnitude and direction of the depth-integrated baroclinic energy fluxes vary temporally, due to a combination of changing generation, propagation, and dissipation. Spatial patterns of internal tide propagation near the Luzon Strait are influenced by the locations of mesoscale eddies to the east and west of the strait. The results provide insight into the mechanisms of variability of the baroclinic tides and highlight the importance of considering both the remotely generated internal tides and the subtidal dynamics to estimate internal tide energetics.

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