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

The mode-1 semidiurnal internal tides that emanate from multiple sources in the Sulu-Sulawesi Seas are investigated using multi-satellite altimeter data from 1993–2020. A practical plane-wave analysis method is used to separately extract multiple coherent internal tides, with the nontidal noise in the internal tide field further removed by a two-dimensional (2-D) spatial band-pass filter. The complex radiation pathways and interference patterns of the internal tides are revealed, showing a spatial contrast between the Sulu Sea and the Sulawesi Sea. The mode-1 semidiurnal internal tides in the Sulawesi Sea are effectively generated from both the Sulu and Sangihe Island chains, forming a spatially inhomogeneous interference pattern in the deep basin. A cylindrical internal tidal wave pattern from the Sibutu passage is confirmed for the first time, which modulates the interference pattern. The interference field can be reproduced by a line source model. A weak reflected internal tidal beam off the Sulawesi slope is revealed. In contrast, the Sulu Island chain is the sole energetic internal tide source in the Sulu Sea, thus featuring a relatively consistent wave and energy flux field in the basin. These energetic semidiurnal internal tidal beams contribute to the frequent occurrence of internal solitary waves (ISWs) in the study area. On the basis of the 28-year consistent satellite measurements, the northward semidiurnal tidal energy flux from the Sulu Island chain is 0.46 GW, about 25% of the southward energy flux. For M2, the altimetric estimated energy fluxes from the Sulu Island chain are about 80% of those from numerical simulations. The total semidiurnal tidal energy flux from the Sulu and Sangihe Island chains into the Sulawesi Sea is about 2.7 GW.

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Observations of low-frequency, long-range acoustic propagation in the Philippine Sea and comparisons with mode transport theory

The Journal of the Acoustical Society of America ◽

10.1121/10.0000587 ◽

2020 ◽

Vol 147 (2) ◽

pp. 877-897

Author(s):

Tarun K. Chandrayadula ◽

Sivaselvi Periyasamy ◽

John A. Colosi ◽

Peter F. Worcester ◽

Matthew A. Dzieciuch ◽

...

Keyword(s):

Long Range ◽

Transport Theory ◽

Low Frequency ◽

Acoustic Propagation ◽

Philippine Sea

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

Journal of Physical Oceanography ◽

10.1175/jpo-d-13-0142.1 ◽

2014 ◽

Vol 44 (5) ◽

pp. 1386-1405 ◽

Cited By ~ 26

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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Interference Pattern and Propagation of the M2 Internal Tide South of the Hawaiian Ridge

Journal of Physical Oceanography ◽

10.1175/2009jpo4256.1 ◽

2010 ◽

Vol 40 (2) ◽

pp. 311-325 ◽

Cited By ~ 67

Author(s):

Luc Rainville ◽

T. M. Shaun Johnston ◽

Glenn S. Carter ◽

Mark A. Merrifield ◽

Robert Pinkel ◽

...

Keyword(s):

Interference Pattern ◽

Satellite Altimetry ◽

Internal Tide ◽

Equation Model ◽

Internal Tides ◽

Multiple Sources ◽

Propagating Waves ◽

Generation Region ◽

Hawaiian Ridge ◽

Energy Flux Density

Abstract Most of the M2 internal tide energy generated at the Hawaiian Ridge radiates away in modes 1 and 2, but direct observation of these propagating waves is complicated by the complexity of the bathymetry at the generation region and by the presence of interference patterns. Observations from satellite altimetry, a tomographic array, and the R/P FLIP taken during the Farfield Program of the Hawaiian Ocean Mixing Experiment (HOME) are found to be in good agreement with the output of a high-resolution primitive equation model, simulating the generation and propagation of internal tides. The model shows that different modes are generated with different amplitudes along complex topography. Multiple sources produce internal tides that sum constructively and destructively as they propagate. The major generation sites can be identified using a simplified 2D idealized knife-edge ridge model. Four line sources located on the Hawaiian Ridge reproduce the interference pattern of sea surface height and energy flux density fields from the numerical model for modes 1 and 2. Waves from multiple sources and their interference pattern have to be taken into account to correctly interpret in situ observations and satellite altimetry.

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Enhanced internal tidal mixing in the Philippine Sea mesoscale environment

Nonlinear Processes in Geophysics ◽

10.5194/npg-28-271-2021 ◽

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.

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