High Frequency Internal Waves Research Articles

Dynamical oceanographic processes impact on reef manta ray behaviour: Extreme Indian Ocean Dipole influence on local internal wave dynamics at a remote tropical atoll

Physical oceanographic observations were made with subsurface, taut-line moorings at Egmont Island, a tropical atoll within the Chagos Archipelago in the central Indian Ocean, to elucidate the dynamics of near-bed cold-water intrusions implicated in driving local aggregations of reef manta rays (Mobula alfredi). Manta have been previously shown to aggregate within ‘Manta Alley’, a lipped gully at 65 m depth along the north coast, at times when the surface to bottom temperature difference was highest. We here identify the dynamical processes driving these temperature differences and shaping the foraging landscape at Egmont, and equivalent small-scale atolls, improving our understanding of manta behavior at hotspots where they are most vulnerable to exploitation.The thermal regime within Manta Alley is shown to be governed at several spatiotemporal scales. The extreme 2019 Indian Ocean Dipole event drove a depression of the 26 °C isotherm to a depth of 115 m precluding the observation of cooling within the alley. As the thermocline shoaled with the change in phase of the IOD, near bed cold water flushing was seen with tidal periodicity within the gully. The internal tide is accompanied by high frequency internal waves with periods of O (5 min) which are shown to promote mixing through shear instability, evidenced by subcritical Richardson numbers, with surface-seabed temperature differences ∼4 °C observed throughout a tidal period.Our results highlight a level of heterogeneity in oceanographic dynamics at sub-atoll spatial scales within an environment in which these processes are rarely resolved. Whilst the physical mechanisms through which these dynamics drive foraging within the resident manta population remain unclear, the generation of turbulence by high frequency internal wave events as shown here may influence zooplankton distributions, improving feeding efficiency at discrete locations within atolls. Our results thus highlight the need to account for fine scale changes in oceanographic conditions when attempting to explain habitat utilization by mobile species.

Predicting Ocean Temperature in High-Frequency Internal Wave Area with Physics-Guided Deep Learning: A Case Study from the South China Sea

Higher-accuracy long-term ocean temperature prediction plays a critical role in ocean-related research fields and climate forecasting (e.g., oceanic internal waves and mesoscale eddies). The essential component of traditional physics-based numerical models for ocean temperature prediction is solving partial differential equations (PDEs), which has immense challenges in terms of parameterization, initial values, and boundary conditions setting. Moreover, the existing machine learning models for ocean temperature prediction have “black box” problems, and the influence of external dynamic factors is not considered. Moreover, it is hard to judge whether the model satisfies certain physical laws. In this paper, we propose a physics-guided spatio-temporal data analysis model based on the widely used ConvLSTM model to achieve long-term ocean temperature prediction and adopt two schemes to train the model in vector output and multiple parallel input and multi-step output. Meanwhile, considering the spatio-temporal correlation, physical information such as oceanic stable stratification is introduced to guide the model training. We evaluate our proposed approach on several popular deep learning models in different timesteps and data volumes in the northern coast of the South China Sea, where the frequent occurrence of internal waves leads to an intensity trend of a local transformation of sea temperature. The results show higher prediction accuracy compared with the traditional LSTM, and ConvLSTM models, and the introduction of physical laws can improve data utilization while enhancing the physical consistency of the model.

Energy Transfer From PSI‐Generated M1 Subharmonic Waves to High‐Frequency Internal Waves

AbstractInternal tides (ITs) represent one of the major energy sources available for small‐scale mixing in the ocean. Here, the energy pathway associated with ITs is examined based on measurements obtained at the East China Sea shelf slope. We reveal that after the occurrence of parametric subharmonic instability (PSI), energy can be further transferred from the PSI‐generated subharmonic waves to high‐frequency internal waves (HFIWs) through nonlinear interactions between them. This interprets the observed similar varying trends of magnitude between internal waves at near‐inertial and high‐frequency bands. Bispectrum and bicoherence estimates confirm that the M1 subharmonic wave interacts with a pair of HFIW which have larger vertical scales and a broad range of frequencies. The averaged net value of the energy transfer rate reaches 2 10−7 W kg−1, which has implications for a further significant role of this energy pathway on the spatial distribution of ocean mixing.

Observation of internal tides, nonlinear internal waves and mixing in the Lombok Strait, Indonesia

Lombok Strait is one of the main exit passages of the Indonesian throughflow (ITF), connecting the interior Indonesian seas with the Indian Ocean. Satellite images have shown that this strait is also the most remarkable zone of the Indonesian seas for the generation of internal tides, which frequently evolve into internal solitary waves (ISWs). Here we present the first comprehensive high-frequency observations of the internal tide in the strait. The observations were carried out at a fixed position around 8 km from the western coast of Lombok Island at a depth of ~300 m. We confirmed the appearance of the non-linear internal tide with an amplitude of ~90 m at a fairly close distance (~30 km) from its generation site in the Nusa Penida Sills (NPS), with a dominant M2 tidal frequency. High-frequency internal waves associated with vertical velocities reaching 20 cm s-1 were observed within the internal tidal trough. We estimated the turbulent kinetic energy dissipation rate using Thorpe and Ellison scales and found a mean dissipation rate of the order of ~ [10-6-10-7] m2 s-3, with enhanced values in the thermocline layer, possibly driven by shear instabilities. We underlined that the use of the Ellison scale is a promising alternative for indirectly estimating the dissipation rate from high-resolution time-series data sets.

Dynamics of the Diurnal Warm Layer: Surface Jet, High-Frequency Internal Waves, and Mixing

AbstractEvolution of a thermally stratified diurnal warm layer (DWL), including the formation and decay of a daytime surface-layer jet, high-frequency internal waves, and mixing were examined from observations collected during July 2016, near 93.75°W, 28°N, on the outer Louisiana–Texas continental shelf in the Gulf of Mexico, when the ocean surface was experiencing a weak sea breeze (<5 m s−1) and strong solar insolation. While winds and surface waves were weak, the DWL was formed with stratification strengthening and stability frequency reaching 14 cycles per hour at 2-m depth, while inhibiting turbulence below the DWL. A surface-intensified jet developed during afternoon hours. The jet, oriented to the right of the wind stress with a speed of about 10 cm s−1 at 2 m, veered and decreased with depth. The magnitude of the diurnal jet was correlated with the heat content anomaly in the DWL. Internal waves with periods ranging from 5 min to 4 h were observed in the upper 4 m. Temperature fluctuations were ~ ±0.2°C, and the corresponding vertical displacements varied from 0.5 to 1 m. These fluctuations appeared during afternoon hours when the Richardson number dropped below the critical value of 0.25 followed by energetic mixing. The daytime jet and the high-frequency fluctuations disappeared a few hours after sunset. Internal waves were likely excited by Kelvin–Helmholtz instabilities and by surface wave and internal wave interactions. Mixing resulting from the dissipation of daytime internal waves is an important factor in regulating sea surface temperature in the DWL.

Cascade of Internal Wave Energy Catalyzed by Eddy‐Topography Interactions in the Deep South China Sea

AbstractThe intensity of deep‐ocean mixing critically shapes the global overturning circulation, but the energy cascade participating in the elevated mixing above rough topography remains poorly understood. Using 350‐day moored observations, the energy cascade triggered by eddy‐topography interactions is for the first time revealed in the deep South China Sea. The deep‐ocean observations show bottom‐intensified near‐inertial wave (NIW) pulses during periods of eddy occurrences. Eddy‐induced NIWs appear to catalyze nonlinear wave‐wave interactions, which further cascade energies from NIWs and internal tides to higher‐frequency internal waves (HFIWs) above fk1 frequency. Corresponding to the HFIW enhancement, the kinetic energy spectrum at 3–9 cycles per day increases by 2–9 times, and the spectral slope becomes ~ −1 rather than ~ −2, as predicted by the Garrett‐Munk oceanic internal wave spectrum. A cascade of internal waves above rough topography potentially promotes extracting energy from eddies and tides and dissipating this energy to mix deep waters.

Cross-Shore Deformation of a Surfzone-Released Dye Plume by an Internal Tide on the Inner Shelf

AbstractAn inner-shelf (IS) dye plume that formed following a 3.84-h early morning surfzone (SZ) dye release off of Imperial Beach, California, is analyzed with in situ and aerial remotely sensed observations. Midmorning, 5 h after release start, the IS plume extended 800 m offshore (or ≈8Lsz, where Lsz is the surfzone width) and was surface intensified. Over the next ≈2 h, the IS plume deformed (narrowed) cross-shore with the offshore front progressing onshore at ≈5 cm s−1, deepened by up to 3 m, and elongated alongshore at ≈4.5 cm s−1 km−1 (at ≈2.5Lsz). Coincident with IS plume deformation and deepening, IS isotherms also deepened, with relatively stable IS plume joint dye and temperature statistics. Offshore tracer transport and subsequent IS plume deformation and deepening likely resulted from two phases of the diurnal internal tide (DIT). During and after deformation, the IS plume did not reenter the warm surfzone, which potentially acted as a thermal barrier. High-frequency internal waves (HF IWs) propagated through the IS plume at ≈9 cm s−1 and dissipated onshore of 4Lsz. Surface HF IW signal was elevated in the plume elongation region, suggesting a linkage between plume elongation and either the DIT or HF IW. This IS plume evolution differs from previous SZ tracer releases, highlighting the effects of release timing relative to the solar cycle or the internal tide.

Fission of Shoaling Internal Waves on the Northeastern Shelf of the South China Sea

AbstractUsing high‐resolution full‐water column velocity data at a site of 60‐m depth on the northeastern shelf of the South China Sea, we observed high‐frequency internal waves (HIWs) occurring continuously on the continental shelf during the 15‐hr observation on 13‐14 July 2011. This phenomenon is in contrast to the regular occurrence of internal solitary waves (ISWs) that are generally phase‐locked to the tides. We hypothesize that the continuously occurring HIWs are generated from shoaling ISWs via fission. Analysis of the Moderate Resolution Imaging Spectroradiometer (MODIS) true‐color images supports this hypothesis. The mechanism of ISW fission is then investigated using an analytical model as well as a two‐layer weakly nonlinear numerical model based on the regularized long‐wave (RLW) equation. The results are also compared with those from a fully nonlinear continuously stratified numerical model. Simulation results are generally consistent with the field measurements, explaining the observations of the continuous occurrence of HIWs. Sensitivity experiments are conducted to investigate the role and effects of the initial wave amplitude, pycnocline depth and thickness, bathymetry, and viscosity on ISW fission. Although all these factors impact the properties of the shoaling ISWs, both the two‐layer and continuously stratified models suggest that fission mainly occurs near the critical point region, highlighting the importance of pycnocline depth. However, simulations using the two‐layer model suggest that fission occurs after ISWs pass through critical points, whereas the fission location predicted by the continuously stratified model is generally offshore of critical points. This points to the deficiency of the two‐layer model in simulating small‐amplitude short trailing waves, large‐amplitude ISWs, wave breaking, and higher‐mode waves.

Small Mountainous Rivers Generate High-Frequency Internal Waves in Coastal Ocean

High-frequency internal waves propagating offshore in small river plumes are regularly observed at satellite imagery in many world regions. In this work we describe a mechanism of generation of these internal waves by discharges of small and rapid rivers inflowing to coastal sea. Friction between river runoff at high velocity and the subjacent sea of one order of magnitude lower velocity causes abrupt deceleration of a freshened flow and increase of its depth, i.e., a hydraulic jump is formed. Transition from supercritical to subcritical flow conditions induces generation of high-frequency internal waves that propagate off a river mouth at a stratified layer between a buoyant river plume and subjacent ambient sea and influence turbulence and mixing at this layer. Basing on in situ and satellite data we estimated wavelengths, phase speeds, and frequencies of internal waves generated in small river plumes located off the northeastern coast of the Black Sea. This process is typical for many other world mountainous regions where numerous and closely spaced small and rapid rivers inflow to sea during high discharge periods and can strongly influence, first, structure and dynamics of river plumes and, second, physical, biological, and geochemical processes in adjacent coastal areas.

Enhanced mixing by patchy turbulence in the northern South China Sea

Enhanced mixing induced by patchy turbulence in the pycnocline was investigated from the turbulent microstructure profiling in the northern South China Sea, where internal waves are active in the pycnocline. Totally 397 turbulence patches have been identified in March 2014 and August to September 2016 for the statistical analyses. The patch Thorpe scale LTp was found to be larger than the patch Ozmidov scales LOp, i.e., LTp=5.56LOp, indicating that the patchy turbulence is mainly driven by the convection. The mean time scale of turbulent patches is 1.4 × 103 s for conversion from potential energy to turbulent dissipation. The mean mixing efficiency of Γ= 0.23 occurs in the patches, approximately twice as large as Γ= 0.12 in the pycnocline. Hence, the patchy turbulence in the pycnocline enhances the intensity of turbulent mixing and increases the mixing efficiency. Turbulent patches in the pycnocline occur mostly near the critical slope at the shelf break or over the sill in the northern SCS. The investigation of the Eulerian strain and available potential energy of turbulent patches indicates that convection induced by high frequency internal waves should be a major mechanism for the formation of turbulent patches.

An Oceanic Ultra-Violet Catastrophe, Wave-Particle Duality and a Strongly Nonlinear Concept for Geophysical Turbulence

There is no theoretical underpinning that successfully explains how turbulent mixing is fed by wave breaking associated with nonlinear wave-wave interactions in the background oceanic internal wavefield. We address this conundrum using one-dimensional ray tracing simulations to investigate interactions between high frequency internal waves and inertial oscillations in the extreme scale separated limit known as “Induced Diffusion”. Here, estimates of phase locking are used to define a resonant process (a resonant well) and a non-resonant process that results in stochastic jumps. The small amplitude limit consists of jumps that are small compared to the scale of the resonant well. The ray tracing simulations are used to estimate the first and second moments of a wave packet’s vertical wavenumber as it evolves from an initial condition. These moments are compared with predictions obtained from the diffusive approximation to a self-consistent kinetic equation derived in the ‘Direct Interaction Approximation’. Results indicate that the first and second moments of the two systems evolve in a nearly identical manner when the inertial field has amplitudes an order of magnitude smaller than oceanic values. At realistic (oceanic) amplitudes, though, the second moment estimated from the ray tracing simulations is inhibited. The transition is explained by the stochastic jumps obtaining the characteristic size of the resonant well. We interpret this transition as an adiabatic ‘saturation’ process which changes the nominal background wavefield from supporting no mixing to the point where that background wavefield defines the normalization for oceanic mixing models.

Nonlinear internal wave penetration via parametric subharmonic instability

We present the results of a laboratory experimental study of an internal wave field generated by harmonic, spatially periodic boundary forcing from above of a density stratification comprising a strongly stratified, thin upper layer sitting atop a weakly stratified, deep lower layer. In linear regimes, the energy flux associated with relatively high frequency internal waves excited in the upper layer is prevented from entering the lower layer by virtue of evanescent decay of the wave field. In the experiments, however, we find that the development of parametric subharmonic instability in the upper layer transfers energy from the forced primary wave into a pair of subharmonic daughter waves, each capable of penetrating the weakly stratified lower layer. We find that around 10% of the primary wave energy flux penetrates into the lower layer via this nonlinear wave-wave interaction for the regime we study.

Energy of marine currents in the Strait of Gibraltar and its potential as a renewable energy resource

Abstract A non-hydrostatic hydrodynamic model of the Strait of Gibraltar with high spatial and temporal resolution has been used to assess suitable areas for energy extraction from marine currents. The model shows great spatial variability of the available energy flux, ranging from 200 W m −2 to more than 1800 W m −2 . In addition to the mean energy flux, other properties and characteristics of the flow such as permanence and direction of the currents, vertical shear or occurrence of unwanted high frequency internal waves have been merged into an index that is used in this work as a proxy for the suitability of a given place to install a power plant. This index highlights two zones gathering the required conditions: the subsurface layer of the eastern half of the strait and the near-bottom layer of Espartel sill at the westernmost gateway of the strait.

ACOUSTIC TRAVEL-TIME PERTURBATIONS DUE TO SHALLOW-WATER INTERNAL WAVES IN THE YELLOW SEA

Internal waves in shallow-water cause variations in sound speed profiles and lead to acoustic travel-time perturbations. In summer 2007, a combined acoustics/physical oceanography experiment was performed to study both the acoustical properties and the ocean dynamics of the Yellow Sea. The internal waves were recorded by the thermistor arrays. The receiving hydrophone array is enabled to monitor the acoustic travel-time fluctuations over the internal wave activities. It is shown that the activity of high frequency internal waves (having 3–6 min period) dominated the travel time perturbation. In this paper, we compare the data of high frequency internal wave with acoustic travel-time perturbation data and analyze the correlation between them. A simple relation between the modal travel-time perturbation and the displacement of the thermocline is developed which might be useful for monitoring purposes.

High-frequency internal wave motions at the ANTARES site in the deep Western Mediterranean

High-frequency internal wave motions of periods down to 20 min have been observed in a yearlong record from the deep Western Mediterranean, mainly in vertical currents. The observations were made using the ANTARES neutrino telescope infrastructure. One line of the telescope is instrumented with environmental monitoring devices, and in particular with an Acoustic Doppler Current Profiler that was used to measure currents around 2,200 m. Such high-frequency internal waves are commonly observed much closer to the sea surface where the vertical density stratification is more stable than in the deep sea. In this paper, they are supported by the relatively large stratification following newly formed dense water. During the severe winters of 2005 and 2006, deep dense-water formation occurred in the Ligurian subbasin. Its collapse and spread over the sea floor across the basin remained detectable for at least 3 years as deduced from the present yearlong current record, which is from 2008. The observed high-frequency internal waves match the occasional density stratification observed in ∼1-m-thin layers using previous shipborne conductivity-temperature-depth measurements. Such layers and waves are relatively unusual in the deep Mediterranean, where commonly several hundreds-of-meters-thick near-homogeneous layers dominate. Such thick near-homogeneous layers provide about a half-decade narrow internal wave band around the inertial frequency (f). In contrast, the presently observed vertical currents occasionally show a "small-scale" internal wave band that is on average 1.5 decades wide, associated with thin-layer stratification. In spite of its relatively large width, this band still shows variance peaking near f rather than near the large-scale buoyancy frequency N (= 2.3-4.5f) and this variance is found to increase with increasing N.

Quantifying the effect of wind on internal wave resonance in Lake Villarrica, Chile

Lake Villarrica, located in south central Chile, has a maximum depth of 167 m and a maximum fetch of about 20 km. The lake is monomictic, with a seasonal thermocline located at a depth of approximately 20 m. Field data show the presence of basin-scale internal waves that are forced by daily winds and affected by Coriolis acceleration. A modal linear and non-linear analysis of internal waves has been used, assuming a two-layer system. The numerical simulations show good agreement with the internal wave field observations. The obtained modes were used to study the energy dissipation within the system, which is necessary to control the amplitude growth. Field data and numerical simulations identify (1) the occurrence of a horizontal mode 1 Kelvin wave, with a period of about a day that coincides with the frequency of daily winds, suggesting that this mode of the Kelvin waves is in a resonant state (subject to damping and controlled by frictional effects in the field) and (2) the presence of higher-frequency internal waves, which are excited by non-linear interactions between basin-scale internal waves. The non-linear simulation indicates that only 10 % of the dissipation rate of the Kelvin wave is because of bottom friction, while the rest 90 % represents the energy that is radiated from the Kelvin wave to other modes. Also, this study shows that modes with periods between 5 and 8 h are excited by non-linear interactions between the fundamental Kelvin wave and horizontal Poincare-type waves. A laboratory study of the resonant interaction between a periodic forcing and the internal wave field response has also been performed, confirming the resonance for the horizontal mode 1 Kelvin wave.

Observations of High-Frequency Internal Waves in the Southern Taiwan Strait

ABSTRACT Bai, X.; Liu, Z.; Li, X.; Chen, Z.; Hu, J.; Sun, Z.; and Zhu, J., 2013. Observations of high-frequency internal waves in the southern Taiwan Strait. Based on in situ hydrographic measurements at a station at about 60 m depth near the local shelf break in July 2011 and a satellite image of the sea-surface roughness, we present the evidence of existence and characteristics of high-frequency internal waves (HIWs) in the southern Taiwan Strait. Variations of the thermohaline structure at the observational site were revealed by repeating conductivity-temperature-depth (CTD) profiling measurements of every 2 hours, while fluctuations of the isothermals due to the passage of HIWs were recorded by continuous CTD measurements with a probe positioned approximately in the middle of the pycnocline. A fast sampling frequency of 8 Hz allows the structure of the HIWs to be captured in great detail. The waves were depression waves, with a period of about 6.2 min and an amplitude of about 25 m. The propagation sp...

Assessment of fine‐scale parameterizations of turbulent dissipation rates near mixing hotspots in the deep ocean

Shear‐based and/or strain‐based fine‐scale parameterizations of turbulent dissipation rates in the deep ocean become erroneous near topographic features where internal wave spectra deviate from Garrett‐Munk (GM). Although the Gregg‐Henyey‐Polzin (GHP) parameterization incorporates this spectral deviation, the applicability remains uncertain. We evaluate “α” and “β” representing the local internal wave energy in the high frequency (2f < ω < N) and low frequency (f < ω < 2f) bands, respectively, scaled by their corresponding values in GM using fine‐scale vertical shear and strain simultaneously measured near mixing hotspots. The local internal wave spectra are biased toward higher frequencies (α/β ≫ 1) over rough bathymetry where high frequency internal waves are generated, whereas they are biased toward lower frequencies (α/β≪ 1) at latitudes where high vertical wavenumber, near‐inertial shears are created byparametric subharmonic instabilities. Compared with the shear‐based and/or strain‐based parameterizations, GHP more accurately estimates turbulent dissipation rates by compensating for deviations from GM.

Spatial structure of thermocline and abyssal internal waves in the Sargasso Sea

Vertical and horizontal spatial structures are analyzed for the steady and internal wave velocity contributions in one hundred full-water-depth velocity profiles collected in the Sargasso Sea in water depths between 4500 and 5500m. Temporal decompositions into subinertial, near-inertial, and high-frequency velocity contributions are obtained from multiple, but brief time series at several locations. Horizontal spatial variability is evaluated from two simultaneous velocity profiles at separations ranging from 15m to 12.5km. The total internal wave field exhibits equipartition between east and north velocity components, a decrease in energy density at the smallest vertical wavenumbers, and an overall dependence for kinetic energy (KE) on vertical wavenumber as m−2.5. Most of the internal wave energy is in near-inertial motions and, of this, most occurs at Wentzel–Kramers–Brillouin (WKB) normalized vertical wavelengths of 150–800 stretched-m (i.e., sm) with a spectral peak at 500-sm wavelength (for No=3cph) and average surrounding the peak of 3c/skm (330sm). Near-inertial contributions exhibit a power law of m−3, while higher-frequency internal waves (ω>2f) a slope of m−2. There is strong vertical polarization (clockwise>anticlockwise) (CW>ACW) of the near-inertial contribution but little or none for higher-frequency motions. There is more WKB normalized near-inertial KE in the lower than in the upper half of the WKB-scaled water column while high-frequency internal waves have comparable upper and lower halves energies. The upper half shows a deficit compared to the Garrett and Munk model spectrum at vertical wavelengths shorter than 100sm. Time-mean shear is largest in the upper half, so critical-layer processes may play a role. The internal wave KE of simultaneous but spatially separated profiles has a zero-correlation scale of 15–20km, dominantly due to near-inertial waves. Thus, deep near-inertial motions exhibit wavelengths of 60–80km in contrast to longer scales reported in the surface mixed layer and upper pycnocline. The aspect ratio k/m (330sm/70km) corresponds to a wave frequency of 1.05f. The downward group velocity is 0.6mms−1, with a vertical energy flux for the near-inertial motions of 0.6mWm−2.

The island‐scale internal wave climate of Moorea, French Polynesia

Analysis of five‐year records of temperatures and currents collected at Moorea reveal strong internal wave activity at predominantly semi‐diurnal frequencies impacting reef slopes at depths ≥30 m around the entire island. Temperature changes of 1.5°C to 3°C are accompanied by surges of upward and onshore flow and vertical shear in onshore currents. Superimposed on annual temperature changes of approximately 3°C, internal wave activity is high from Oct–May and markedly lower from Jun–Sep. The offshore pycnocline is broadly distributed with continuous stratification to at least 500 m depth, and a subsurface fluorescence maximum above the strong nutricline at approximately 200 m. Minimum buoyancy periods range from 4.8 to 6 min, with the maximum density gradient occurring at 50 to 60 m depth in summer and deepening to approximately 150 to 200 m in winter. The bottom slope angle around all of Moorea is super‐critical relative to the vertical stratification angle suggesting that energy propagating into shallow water is only a portion of total incident internal wave energy. Vertical gradient Richardson numbers indicate dominance by density stability relative to current shear with relatively limited diapycnal mixing. Coherence and lagged cross‐correlation of semi‐diurnal temperature variation indicate complex patterns of inter‐site arrival of internal waves and no clear coherence or lagged correlation relationships among island sides. Semi‐diurnal and high frequency internal wave packets likely arrive on Moorea from a combination of local and distant sources and may have important impacts for nutrient and particle fluxes in deep reef environments.