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The Hunga‐Tonga volcano eruption on 15 January 2022 generated tsunami waves that impacted both the Pacific and Atlantic coasts of the Americas. A unique feature of this event was the dual tsunami generation mechanism, which led to motions with long (several days) ringing and slow energy decay. The first ocean waves to reach the coast were "atmospheric tsunamis" generated by atmospheric Lamb waves that propagated with the speed of sound (∼314 m/s) and circled the globe in both directions several times before being fully attenuated. The second type of ocean waves were classical "oceanic tsunami" waves forced directly by the volcanic eruption and which propagated across the Pacific at roughly 2/3 the speed of the atmospheric waves. This study focuses on time series of the Hunga‐Tonga event recorded by tide gauges, microbarographs and Deep‐ocean Assessment and Reporting of Tsunamis on and off the Pacific coasts of North and Central America and in the Gulf of Mexico. Atmospheric tsunami waves only were recorded in the Gulf of Mexico, where the sea level response to the second, westward (shoreward) propagating atmospheric wave was stronger than to the first, eastward (seaward) propagating wave. Along the Pacific coast, the atmospheric tsunami waves were approximately 3–4 times smaller than the oceanic tsunami waves, which at several Mexican stations exceeded 2 m in height. The broad frequency range of 0.2–0.25 to 30 cph spanned by the oceanic tsunami in the Pacific indicates that the "effective" source area for the oceanic waves was more extensive than initially proposed. Plain Language Summary: The eruption of the Hunga‐Tonga volcano in January 2022 generated two types of tsunami waves: ordinary "oceanic" tsunami waves forced by the eruption itself and "atmospheric" tsunami waves forced by propagating pressure waves in the atmosphere. The oceanic tsunamis radiated outward into the Pacific while the atmospheric waves propagated around the globe several times in both the eastward and westward directions. Measurements by tide gauges, microbarographs and open‐ocean Deep‐ocean Assessment and Reporting of Tsunamis stations on and off the Pacific coasts of North and Central America and the Gulf of Mexico show that both types of waves were recorded on the Pacific coast but that only the atmospherically generated waves were recorded in the Atlantic Ocean and adjoining Gulf of Mexico. The atmospheric tsunamis were 3–4 times smaller than the oceanic tsunamis, which at Port San Luis and several Mexican locations, including Manzanillo and Ensenada, were higher than 2 m. The broad frequency content of the oceanic waves indicates that their source region had an "effective" area that greatly exceeded that directly spanned by the volcanic eruption. Key Points: The Tonga volcanic event generated two types of tsunami waves: "oceanic" by the eruption and "atmospheric" by atmospheric Lamb wavesThe open‐ocean and coastal records enabled us to separate the two types of tsunami waves and determine their physical propertiesThe waves span a wide frequency range, indicating that the "effective" source region greatly exceeded that covered by the eruption [ABSTRACT FROM AUTHOR]

This study presents the observation and evaluation of a meteotsunami in the Indian Ocean triggered by the Hunga‐Tonga volcanic eruption. The event was detected through tide gauges and bottom‐pressure recordings across the Indian Ocean, with an amplitude of 10–15 cm, lasting for a few days. A numerical model was used to understand the ocean's response to meteotsunami and evaluate the dynamics behind it. The model results show that the sea‐level oscillations result from the ocean waves generated by a propagating Lamb wave. In addition to interaction with bathymetry, refracted and reflected waves also determine the sea‐level variability. Our analysis shows that bathymetric slope plays a vital role in near‐shore processes. The spectral and spatial characteristics of the meteotsunami were reminiscent of seismic tsunamis. Our research on this rare event elucidates the unresolved issues and eventually leads to designing a blueprint for future observation and modeling of meteotsunamis and seismic tsunamis. Plain Language Summary: This study evaluates the observation of a rare meteotsunami event that occurred in the Indian Ocean. An atmospheric pressure wave generated by the eruption of the Hunga‐Tonga volcano in the Pacific Ocean caused the meteotsunami. The signatures of this event were captured by tide gauges installed along the coast and pressure recorders moored at the ocean floor. We demonstrate using a numerical model that fast‐moving atmospheric pressure waves, Lamb waves, caused the sea‐level oscillations. Interactions with bathymetry further influenced sea‐level variability in the basin, reflected waves, and refracted waves. The vulnerable areas showed a striking resemblance to the area impacted by the tsunami that hit the Indian Ocean in 2004. This research eventually helps to identify and incorporate observational and modeling issues associated with seismic tsunamis and meteotsunami. Key Points: We present the first comprehensive evaluation of meteotsunami in the Indian Ocean using observation and modelingA forced wave to free wave transformation happens on the continental slope, and the bathymetry slope is crucial to near‐shore processesThe meteotsunami exhibits a spectral and spatial similarity to seismic tsunamis that previously occurred in the Indian Ocean [ABSTRACT FROM AUTHOR]

The load-bearing capacity is a pivotal consideration in the design of offshore renewable energy structures. This paper aims to address the technical challenges associated with the additional wave loads caused by the integrated devices in a hybrid system for the multi-purpose utilization of coastal renewable energy. A self-protected hybrid wind-wave energy system is proposed, in which an oscillating water column (OWC) device is attached at a monopile foundation of an offshore wind turbine. In the meantime, the OWC is connected by a submerged horizontal perforated plate at its exterior shell, which is expected to minimize the wave loads on the system. The hydrodynamic performance of the system is investigated. A novel approach is developed to model the wave interaction with the hybrid system. This efficient approach removes the necessity of decomposing the wave-scattering field into diffraction and pressure-dependent radiation components. Detailed numerical computation is then conducted for both regular and irregular sea states. Various hydrodynamic properties related to the system, such as wave energy harvesting, wave force/moment, and free-surface elevation, have been evaluated. Numerical results manifest the feasibility of imposing a negligible effect on the high wave energy harvesting while reducing the high wave loads by manipulating the submerged horizontal perforated plate. The impact of the perforated plate on the dominant wave energy harvesting in the long-period region is found to be trivial. In contrast, it can affect the high bending moment in the short-period region, which causes a reduction of greater than 15%. [ABSTRACT FROM AUTHOR]

We investigate the oceanic and ionospheric response in New Caledonia‐New Zealand and Chile‐Argentina to the 15 January 2022 Hunga‐Tonga volcanic eruption. For the first time, we highlight a reversed response in the oceans and in the ionosphere in terms of the amplitudes. The sea‐surface fluctuations due to the passage of the atmospheric Lamb wave (i.e., air‐sea wave) were not remarkable while the related ionospheric perturbation was considerable. Reversely, the eruption‐induced tsunami ("regular" tsunami) caused major variations in sea‐surface heights (∼1 m near the volcano and ∼2 m along the Chilean coastline), whereas the associated ionospheric perturbation was quite small. The observed large‐amplitude ionospheric response due to Lamb waves propagation is difficult to explain, and the coupling between the Lamb wave and the ionosphere is not well‐understood yet. For the first time, we estimate the delay between the Lamb waves and their signatures in the ionosphere to be ∼12–20 min. Plain Language Summary: The eruption of Hunga‐Tonga volcano produced a variety of atmospheric and tsunami waves recorded all over the world. We study the impacts of the eruption together on the oceans and in the ionosphere in New Caledonia‐New Zealand (near the volcano) and Chile‐Argentina (far from the volcano). At the sea surface, we observe two phenomena causing sea‐height variations. The first is a small tsunami (air‐sea wave) created by the Lamb wave: the high‐pressure atmospheric wave triggered by the eruption. The second is the tsunami induced by the eruption itself. Spectacularly, at 300 km altitude, in the ionosphere, we observe perturbations in the electron content caused by the Lamb wave and by the regular tsunami. We are the first to report on the reversed amplitude of the two phenomena in the oceans and in the ionosphere. The sea‐surface perturbation caused by the Lamb wave was not significant, while ionospheric perturbation was considerable. In contrast, the regular tsunami wave produced major variations. For the first time, we estimate the time delay between the Lamb wave and its signature in the ionosphere. Key Points: Joint study of oceanic and ionospheric response in New Caledonia‐New Zealand and Chile‐Argentina to the 15 January 2022 volcanic eruptionNear‐surface propagating Lamb wave caused a small tsunami in the ocean (air‐sea wave) and unusually strong disturbances in the ionosphereInversely, the eruption‐generated tsunami showed significant wave heights in the ocean and much smaller response in the ionosphere [ABSTRACT FROM AUTHOR]

An understanding of the hydroelastic response of a flexible circular plate to water waves is relevant to many problems in ocean engineering ranging from offshore wave energy converters and solar wind devices to very large floating structures such as floating airports and ice sheets. This paper describes results from physical model tests undertaken in the COAST laboratory at the University of Plymouth. Response amplitude operators (RAOs) of a floating flexible circular disk are determined for incident monochromatic and irregular wave trains, the latter defined by JONSWAP spectra. Free-surface displacements are measured using wave gauges, and the plate motion recorded using a QUALISYS® motion tracking system. Different basin depths and plate thicknesses are considered in order to quantify the effects of water depth and flexural plate rigidity on the overall dynamic behaviour of the circular disk. We present synchronous and subharmonic nonlinear responses for monochromatic waves, and displacement spectra for irregular waves. The measured wave hydrodynamics and disk hydroelastic responses match theoretical predictions based on linear potential flow theory. [Display omitted] • Experimental data on floating flexible disk dynamics in water waves. • Potential flow theory provides close match to experimental data. • 2nd & 3rd harmonic responses in regular waves are identified. [ABSTRACT FROM AUTHOR]

The 2022 eruption of the Hunga Tonga-Hunga Ha'apai volcano excited an atmospheric Lamb wave, which induced a fast-traveling tsunami. This tsunami was driven by the pressure-forced wave traveling at the speed of the Lamb wave and, thus, was much faster than conventional tsunamis. This was the first case in which ocean bottom monitoring systems widely observed an air pressure-induced tsunami. We found that the pressure-forced waves split and generated ocean gravity waves after passing the Japan Trench based on the S-net data. Our simulations show that changes in water depth can amplify or decrease the pressure-forced wave. Simultaneously, an ocean gravity wave is generated due to the conservation of water volume. Because the ocean gravity wave was slower than the pressure-forced wave near Japan, it was separated from, and traveled behind, the pressure-forced wave. We explained the wave separation phenomenon and reproduced the waveforms of different splitting stages observed by the stations near the Japan Trench. [ABSTRACT FROM AUTHOR]

Worldwide tsunamis driven by atmospheric waves—or planetary meteotsunami waves—are extremely rare events. They mostly occur during supervolcano explosions or asteroid impacts capable to generate atmospheric acoustic-gravity waves including the Lamb waves that can circle the globe multiple times. Recently, such ocean waves have been globally recorded after the Hunga Tonga–Hunga Ha'apai volcano eruption on 15 January 2022, but did not pose any serious danger to the coastal communities. However, this study highlights that the mostly ignored destructive potential of planetary meteotsunami waves can be compared to the well-studied tsunami hazards. In practice, several process-oriented numerical experiments are designed to force a global ocean model with the realistic atmospheric response to the Hunga Tonga–Hunga Ha'apai event rescaled in speed and amplitude. These simulations demonstrate that the meteotsunami surges can be higher than 1 m (and up to 10 m) along more than 7% of the world coastlines. Planetary meteotsunami waves thus have the potential to cause serious coastal damages and even human casualties during volcanic explosions or asteroid impacts either releasing intense acoustic energy or producing internal atmospheric gravity waves triggering the deep-ocean Proudman resonance at a speed of ∼212 m s−1. Based on records of catastrophic events in Earth's history, both scenarios are found to be realistic, and consequently, the global meteotsunami hazards should now be properly assessed to prepare for the next big volcanic eruption or asteroid impact even occurring inland. [ABSTRACT FROM AUTHOR]

On 15 January 2022, the Tonga-Hunga submarine volcano erupted in the southwest Pacific Ocean and created strong tsunami waves that had a dual generation mechanism: "direct" (caused by the explosion) and "atmospheric" (induced by propagating atmospheric Lamb waves). Trans-oceanic waves spread across the ocean and were clearly recorded in marginal seas of the northwestern Pacific, including the Sea of Japan. The two distinct types of incoming waves produced a variety of effects in the sea as determined by the wave origin, propagation features and local topographic properties. Statistical and spectral properties of the tsunami waves recorded in the Sea of Japan and vicinity, including the adjacent part of the northwestern Pacific, are the main subject of the present study. The Sea of Japan is a semi-isolated basin connected to the Pacific Ocean through several straits. The features of these straits (widths, depths, and geometry) significantly affected the arriving waves, strongly modifying their statistical characteristics and spectral content. As discussed in detail in this paper, the two types of incoming tsunami waves are consequently transformed in substantially different ways. [ABSTRACT FROM AUTHOR]

The target scattering characteristics in microwave band are necessary to be researched for Orbital‐Angular‐Momentum (OAM) wave‐based radar applications. A theoretical description of electromagnetic (EM) scattering from a typical target by OAM waves is proposed in this paper. First, OAM waves are decomposed into plane waves in the spectral domain with different elevation and azimuth angles. Then, the scattering form of each decomposed plane wave is determined through coordinate system transformation and physical optics approximation. Formulas and numerical results are presented for OAM‐based radar scattering cross section of a perfect electric conductor and dielectric plate and a cylinder. Unlike the conventional results of EM plane wave scattering, the scattering properties of OAM waves from plate and cylinder are analysed with particular emphasis on OAM mode influence. The results provide insights into OAM wave‐matter interactions and may find important applications in wave propagation and OAM wave‐based radar detection and imaging. [ABSTRACT FROM AUTHOR]

The 2022 volcanic eruption in Tonga caused an unusually large tsunami around the Pacific. It travels with a faster apparent velocity and has larger amplitudes at long distances than what would be expected from a conventional tsunami from the volcanic source. This tsunami was generated by the moving atmospheric Lamb wave and traveled at the speed of the Lamb wave (0.31 km/s). Japanese data showed the amplitude of this first tsunami becomes small when approaching the coast, due to the weaker air‐sea coupling at the shallow depth. This wave split when passing the continental slope, and traveled at the speed of the ocean gravity wave. Therefore, the tsunami observed at the coast is delayed by thousands of seconds from the passage of the Lamb wave. Tsunamis generated by this atmospheric mechanism have not been previously observed by modern digital recording systems and should be considered in the tsunami warning systems. Plain Language Summary: A tsunami is usually generated by the sudden changes of the water heights, and caused by offshore earthquakes, coastal landslides, and submarine volcanic eruptions. The generated vertical displacement of the water propagates as a very long wave, and the tsunami waves become compressed with increased heights as they approach the coast. The 2022 volcanic eruption in Tonga caused an unusually large tsunami, which cannot be explained by conventional sources. The speed and amplitude are very different from theoretical values: the speed is about 0.31 km/s, whereas the average tsunami speed in the Pacific is 0.2 km/s. These data suggest that the tsunami from the Tonga eruption was excited by a pulse of atmospheric pressure as it traveled from the volcano. This source of the tsunami in the atmosphere needs to be considered for the tsunami warning system in the future. Key Points: Lamb wave produced by the volcanic eruption excites the sea surface as it travels across the Pacific and generates a tsunami pulseThe effect of the air‐sea coupling becomes weaker as the Lamb wave approaches the coastThe tsunami wave splits when passing the continental slope of Japan causing more complex waves [ABSTRACT FROM AUTHOR]

The paper presents the results of processing recordings of abnormal signals, which originated during the eruption of Hunga Tonga-Hunga Haʻapai volcano, and were registered by a laser nanobarograph and two laser strainmeters; there were three meters of sea-level variations, located in the Sea of Japan, and twelve meters of sea-level variations, located in the Pacific Ocean. Acoustic-gravity Lamb waves, generated in the atmosphere, caused disturbances of similar periods in the Earth's crust, which were registered by laser strainmeters. Atmospheric impulse and Lamb waves during their propagation over the Pacific Ocean and the Sea of Japan initiated meteorological tsunamis in their waters, at periods corresponding to the seiches (Eigen oscillations) of registration stations' location areas. In the records of all sea wave recorders, we did not find signs of a classical tsunami origination, and in the records of laser strainmeters, we did not find signals corresponding to seabed displacements at the point of the volcano explosion that led to the formation of a classical tsunami. [ABSTRACT FROM AUTHOR]

In this study, we propose a mechanical analysis for estimating the internal pressure of a finitely deformed spherical compartment from Lamb wave measurements. The proposed analysis produces a dispersion relation associating Lamb wave speed with pressure using limited material parameters (only a strain stiffening term). The analysis was validated on ultrasound bladder vibrometry (UBV) experiments collected from 9 ex vivo porcine bladders before and after formalin cross-linking. Estimated pressures were compared with pressures measured directly by a pressure transducer. The proposed analysis proved broadly effective at estimating pressure from UBV based Lamb wave without calibration as demonstrated by the observed concordance between estimated and measured pressures (Lin’s CCC = 0.82 (0.66-0.91). Theoretical limitations and potential refinements to improve the accuracy and generality of the approach are discussed. [ABSTRACT FROM AUTHOR]

In this work, a newly developed Smoothed Particle Hydrodynamics (SPH) algorithm for nonlinear elasticity is combined with an incompressible SPH fluid solver to investigate the dynamics of a floating plate under impacts of regular water waves with a high steepness. Two scenarios of the plate's rigidity are investigated. The simulation results show that deformations of the stiffer plate mainly occur in a simple bending mode with small amplitudes, and the plate is almost submerged by a strong fluid flow over its surface. In the other scenario, the plate deforms more complexly with much higher deformation amplitudes but experiences a much weaker overwash. The more flexible plate is less resistant to wave motions and converts more wave energy into elastic deformations, and therefore, the overwash is less severe. A strong overflow exerts a pressure force onto the plate that alters the plate's dynamics and adds a viscous (damping) effect on the plate's elastic vibrations, especially in high-frequency modes. A rigorous examination of the numerical convergence and validation using the linear thin plate theory is also carried out. The new SPH algorithm for nonlinear elasticity shows its stability and reliability in evaluating finite and large elastic deformations. Therefore, it is promising for simulating elastic structures in fluid–structure interaction problems. [ABSTRACT FROM AUTHOR]

On 15 January 2022, around 4:30 UTC the eruption of the Hunga‐Tonga volcano, in the South Pacific Ocean, generated a violent underwater explosion. In addition to tsunami waves that affected the Pacific coasts, the eruption created atmospheric pressure disturbances that spread out in the form of Lamb waves. The associated atmospheric pressure oscillations were detected in high‐frequency in‐situ observations all over the globe. Here we take advantage of the similarities in the propagation and characteristics between atmospheric Lamb waves and long ocean waves and we use a 2DH ocean numerical model to simulate the phenomenon. We compare the outputs of the numerical simulation with in‐situ atmospheric pressure records and with remote satellite observations. The signal in the model matches the observed atmospheric pressure perturbations and reveals an excellent agreement in the wave arrival time between model and observations at hundreds of locations at different distances from the origin. Plain Language Summary: The underwater explosion of the Hunga‐Tonga volcano in the South Pacific Ocean generated atmospheric pressure disturbances, known as Lamb waves, that propagated and surrounded the globe several times. In this study, we exploit the similarities between atmospheric Lamb waves and long waves in the ocean (e.g., tsunamis) to simulate their propagation using an ocean numerical model. The comparison of our results with remote satellite data and in‐situ atmospheric pressure records reveals that our model correctly reproduces the propagation of the atmospheric disturbances generated by the volcano explosion. Key Points: The underwater Hunga‐Tonga volcano exploded generating Lamb waves that traveled around the Earth several timesWe simulate these waves using a hydrostatic shallow water equation oceanic modelThe results closely follow the observations of atmospheric pressure perturbations [ABSTRACT FROM AUTHOR]

A recent study observed the existence of a salient bias toward the symmetric part of the tropical wavenumber–frequency spectrum. Examination of the tropical brightness temperature (BT) spectrum in this note shows that its parity difference, i.e., the difference between its symmetric and antisymmetric components, is concentrated in regions of the wavenumber–frequency plane corresponding to the spectral bands suggested by Wheeler and Kiladis. In terms of the difference between the spectral power in the symmetric and antisymmetric components, the spectral bands corresponding to Kelvin waves, Madden–Julian oscillation, and Rossby waves explain about 31%, 21%, and 13% of the symmetric bias, respectively, while the combined contribution of all the other bands is negligible. The "background" spectrum after filtering out all the spectral bands explains the remaining 35% of the symmetric bias. As these spectral bands were originally designed for filtering convectively coupled equatorial waves, the findings of this note may help estimate the contributions of different wave features to the symmetric bias in the tropical BT spectrum. In addition, these findings may also help better understand the processes responsible for generating the tropical background spectrum. [ABSTRACT FROM AUTHOR]

Observations of teleseismic earthquakes using broadband seismometers on the Ross Ice Shelf (RIS) must contend with environmental and structural processes that do not exist for land-sited seismometers. Important considerations are: (1) a broadband, multi-mode ambient wavefield excited by ocean gravity wave interactions with the ice shelf; (2) body wave reverberations produced by seismic impedance contrasts at the ice/water and water/seafloor interfaces and (3) decoupling of the solid Earth horizontal wavefield by the sub-shelf water column. We analyze seasonal and geographic variations in signal-to-noise ratios for teleseismic P-wave (0.5–2.0 s), S-wave (10–15 s) and surface wave (13–25 s) arrivals relative to the RIS noise field. We use ice and water layer reverberations generated by teleseismic P-waves to accurately estimate the sub-station thicknesses of these layers. We present observations consistent with the theoretically predicted transition of the water column from compressible to incompressible mechanics, relevant for vertically incident solid Earth waves with periods longer than 3 s. Finally, we observe symmetric-mode Lamb waves generated by teleseismic S-waves incident on the grounding zones. Despite their complexity, we conclude that teleseismic coda can be utilized for passive imaging of sub-shelf Earth structure, although longer deployments relative to conventional land-sited seismometers will be necessary to acquire adequate data. [ABSTRACT FROM AUTHOR]

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Tide gauge data indicated that ocean waves were generated by the eruption of the Hunga Tonga-Hunga Ha'apai volcano on January 15, 2022. These high-amplitude waves reached the Japanese coast earlier than expected for free ocean waves. These fluctuations in sea level were reasonably reproduced by an ocean model, with realistic bottom topography forced by sea-level pressure perturbations well reproduced by atmospheric general circulation models. While early arrival times are associated with atmospheric Lamb waves, the amplitude of the sea level changes cannot be fully explained by the resonance mechanism associated with sea-level pressure fluctuations of Lamb and Pekeris waves alone. Rather, resonance due to atmospheric waves in conjunction with the amplification effects caused by a steep continental slope is required in order to reproduce sea level fluctuations along the Japanese coast. In particular, the deep Northwest Pacific Basin to the east of Japan is important for strengthening the amplitude of the meteorological tsunami. • Sea level fluctuations due to the 2022 volcanic eruption in Tonga was reproduced. • Meteorological tsunamis were generated by Lamb and Pekeris waves. • Meteorological tsunamis by Pekeris waves are amplified due to Proudman resonance. • Meteorological tsunamis are amplified by entering the sharp continental slope. [ABSTRACT FROM AUTHOR]

This paper presents an arrangement of sub-surface fixed horizontal plates as an alternative to single long plates and conventional breakwaters. Through experimental tests in a wave flume, their capability as coastal protection elements was evaluated varying the number of plates and their spacing, as well as the roughness of their crowns by means of three different flexible covers. Due to the spatial arrangements, a Bragg reflection was achieved but it did not improve the plate performance. The results suggest that the plates work best when their spacing is far from this resonance condition. In general, the minimum spacing is recommended for maximizing wave energy dissipation. Wave transmission had lower values when increasing the number of plates. Energy redistribution was observed from low to high frequencies of the spectra due to non-linear interactions. Wave skewness was calculated but remained low in the sheltered area. Moreover, the flexible cover was useful for filtering the waves in the frequency range between 1.5 and 3.5 times the peak frequency of the spectrum, with a more complex role in the dissipation of energy of longer waves. • Bragg reflection was detected but does not significantly reduce wave transmission. • Plates work better for coastal protection when separated 25% of incident wavelength. • Wave energy transmission is inversely correlated with the number of plates. • A flexible medium cover effectively prevents the generation of high frequency waves. • The Interaction of incident waves with the plates does not increase wave skewness. [ABSTRACT FROM AUTHOR]

Forced ice-shelf oscillations modeling was undertaken employing a full 3D finite-difference model of an elastic ice shelf that was coupled to a treatment of under-shelf seawater flux. The seawater flux was described by the wave equation, which includes the pressure excitements in the shallow water layer under the ice shelf. Thus, ice-shelf flexure was produced by hydrostatic pressure oscillations in the below-shelf seawater. Numerical calculations were performed for an idealized rectangular crevasse-ridden ice-shelf geometry. The crevasses were modeled as rectangular notches into the ice shelf. In the numerical experiments, the ice-plate flexures were forced by harmonic-entering pressure oscillations having a range of periodicities 5–250 s. The dispersion spectra derived for a crevasse-ridden ice shelf revealed "band gaps"—frequency ranges where no eigenmodes exist. The results further showed that the impact of ocean waves on the ice plate is abated from the point of view of a decrease in the spectral average amplitude in the vicinity of the spectrum where the "band gaps" are observed. This impact depends on the depth of crevasse penetration to the ice. [ABSTRACT FROM AUTHOR]

Recognizing that cyclical flexural fluctuations in sea ice sheets stimulated by waves can potentially initiate and perpetuate cracks that may ultimately lead to the destruction of an ice cover, we discuss some winter observations collected beneath the fast ice cover of Mordvinova Bay in the south-east of Sakhalin Island during 2018–2019 when a large crack formed that subsequently detached the offshore sea ice from the inshore ice plate by a wide lead. Energy density spectra show the ramifications of surface-gravity waves from the open ocean—primarily at swell frequencies—penetrating far into the ice from offshore, together with comparatively long, resonant leaky wave modes that gradually dissipate as they propagate alongshore but present a diminishing standing wave envelope of antinodes perpendicular to the coast. By evaluating amplitudes over different ranges of period, three swell wave events are assessed to determine whether they alone could have induced enough bending in the sea ice plate to cause breakage, acknowledging that this would normally occur much closer to the peripheral ice edge where the stresses are largest or as the swells run ashore. The foreshortened seaward standing curvature profile of leaky wave antinodes is also considered as a prospective source of cracking. Whilst neither pathway is found conclusively to be independently responsible for breaking the ice in this case, it is conjectured that the combined influence of swell and leaky waves acting together could cause the observed crack to form. In this case, fracture would occur at a distance of less than about four or so kilometres from the shore, where the antinodal curvatures induced by the standing leaky modes are sufficient. Conceding that the unrelenting flexing of the ice plate by waves and swell could affect the longevity of the sea ice as well, fatigue-precipitated weakening is explored. By determining the value of the mechanical stress at which an ensuing rupture of the fast ice could happen, it is shown that ice destruction can eventuate approximately 17 h after the swell first arrives at the ice edge from the Sea of Okhotsk, appreciating that breakup will depend on prevailing and prior meteorological conditions, the form and state of the sea ice including any preexisting defects, and the specific periods of swell waves that infiltrate the Mordvinova Bay ice sheet. • Wave observations conducted using bottom-mounted pressure sensors in Mordvinova Bay on Sakhalin Island are discussed. • 2 s to 20 min waves were detected and analysed, with the main focus being swells and leaky modes up to about 7 min period • Whilst sometimes detected in open water bays, the authors believe leaky modes have not been reported under sea ice before. • Swells and leaky wave modes acting together is suggested as a novel mechanism by which shore fast ice can be fractured. [ABSTRACT FROM AUTHOR]

The need for renewable energy has gained importance with growing concerns about climate change. Wave energy has attracted considerable attention owing to its sustainability potential. Reflection, refraction, diffraction, and shoaling of waves occur when waves propagate through a submerged structure. These mechanics, when properly utilized, can be employed to focus waves to a specific location and also to increase wave heights, by which wave energy is usually represented, for planning and designing wave farms. Wave focusing induced by a submerged crescent-shaped plate for different wave conditions, incident wave directions, and submerged depths mainly considering the potential applications of absorber wave-energy converters within the wave farm was investigated experimentally and numerically. All experimental regular wave conditions were controlled to be nonbreaking, and the numerical results were obtained by a 3D model, implemented through the boundary element method based on Airy wave theory. The results show that wave focusing appears behind the plate along the direction of the incident waves, and the locations of focused waves tend to be farther away from the plate for shorter-period waves. The maximum measured wave height can be 3.44 times higher than the incident wave height. [ABSTRACT FROM AUTHOR]