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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]

This study presents an approach to better characterize the P‐wave and S‐wave velocity structure of the seafloor sediment layer using ocean bottom seismometers. The presence of low‐velocity seafloor sediment layers influences the observed seismic record at the seafloor over a broad frequency range, such that detailed knowledge of this sediment structure is essential to predict its effect on teleseismic records. We use the radial component of teleseismic P waves and autocorrelation functions of the radial, vertical, and pressure components of teleseismic P and S waves to obtain sediment layer models using the Markov chain Monte Carlo approach with parallel tempering. Synthetic tests show that the body waves constrain the P‐ and S‐wave impedances and travel times and the P‐ to S‐wave velocity ratio of the sediment layers. The proposed method resolves thin layers at a high resolution, including the uppermost thin (∼50 m to a few hundred meters) low S‐wave velocity layer. Real data applications at sites across the Pacific Ocean that are coincident with previous in situ studies demonstrate the effectiveness of this method in characterizing the seafloor sediment unit. The sediment models characterized by this new approach will allow us to more accurately predict and correct the effects of sediment layers in generating P‐ and S‐wave reverberations. Plain Language Summary: Ocean bottom seismometers are powerful tools for investigating the detailed structure of the oceanic mantle. However, most ocean bottom seismometers are placed above the low‐velocity water‐saturated sediment layer, such that their seismic records are inevitably affected by this seafloor sediment layer. Detailed constraints on the structure of the seafloor sediment layer allow us to accurately predict its effects on the observed seismic records. The seafloor sediment layer may consist of multiple discontinuities and vary regionally. This study proposes a new approach for characterizing the seismic properties of the seafloor sediment layer using teleseismic body waves recorded at ocean bottom seismometers. Synthetic tests show that the method can resolve thin sublayers within the sediment layer, such as a very thin low shear‐wave velocity layer and sharp seismic velocity jumps. Real data applications show that the sediment models obtained using this approach are in good agreement with those obtained from direct measurements and previous body‐wave analyses. Our proposed method will enable more detailed prediction and correction of the influence of the sediment layer on ocean bottom seismometer records, thereby providing more accurate constraints on deeper Earth structures. Key Points: The seismic properties of the seafloor sediment layer are characterized using ocean bottom seismometer teleseismic body‐wave recordsThe P‐ and S‐wave impedances and travel times and the VP/VS values of each sublayer within the sediment layer are resolvedIn situ seafloor sediment structure constraints will enable accurate correction and prediction of shallow structure effects [ABSTRACT FROM AUTHOR]

We show large "shields" can significantly reduce horizontal component noise levels for ocean bottom seismometers by shielding the seismic sensors from shaking due to ocean currents. However, at short period (<1 s) some noise from vibration or rocking of the shield under current can partly couple through the ground causing peaks in the noise spectra. Deformation of the seafloor under ocean wave loading ("compliance") raises noise levels at long period (>5 s) for both vertical and horizontal components at shallow water sites. Pressure gauge data is now routinely used to predict and remove this source of noise on vertical component data. We have developed horizontal pressure gradient (HPG) gauges to measure and remove this source of noise from horizontal component data. The combination of HPG data and shielding enables low noise long period seismic observations at otherwise very noisy shallow seafloor sites. Plain Language Summary: There is a compelling need to install seismometers on the shallow seafloor to measure underlying Earth structure and to better understand tsunami and seismic hazard, particularly hazard associated with subduction zone earthquakes. Measurements on the shallow seafloor are invariably very noisy due to strong seafloor currents and the deformation of the seafloor under ocean wave loading. We show large metal covers can substantially shield the sensors from the effects of current, thus removing much of this noise. Ocean wave loading noise can be measured and predicted and removed by measuring the ocean wave loading using collocated sensors that measure seafloor pressure and horizontal gradients of pressure at the seafloor making the detection of small amplitude seismic signals more possible. Key Points: Heavy shields can eliminate current induced tilt noise at long period on seafloor seismometers but may raise noise levels at short periodOcean waves raise long period noise levels on the horizontal component seismic data as the seafloor deforms under wave loadingData from horizontal pressure gradient sensors can be used to remove up to 25 dB of wave loading noise from the seismic data [ABSTRACT FROM AUTHOR]

It has long been recognized that specific ambient seismic noise is generated within the ocean. Therefore, ocean bottom seismometers have advantages to reveal the noise characteristics directly in the deep sea. We use the seismic recordings around Tristan da Cunha collected by 20 OBSs and two island stations to investigate the ambient noise sources in the middle of the South Atlantic. We analyzed the power spectral density, ambient noise cross‐correlations, and correlations with wave heights model. While primary microseisms (∼10–20 s) in this region are deficient, the secondary microseisms are strong and dominate the ambient noise at periods of ∼1–10 s, with the peak broadening to shorter periods (1–3 s). The secondary microseisms are strongly correlated with the local wave heights, especially at shorter periods (∼1–3 s), suggesting that the microseisms are affected mostly by local wave interactions. We observed clear Empirical Green's functions at periods of ∼3–10 s, indicating the existence of distant sources of secondary microseisms. Results of asymmetry analysis of cross‐correlations suggest the prominent direction of the distant source should be located to the Southwest and show barely seasonal variations. The correlations with wave heights indicate a possible source region in the southeast Pacific Ocean. Therefore, besides the dominating local wave‐wave interactions, the secondary microseisms around Tristan region are affected simultaneously by persistent distant sources from the deep basin in the Southeast Pacific Ocean, which might be related to the intense wave‐wave interactions caused by the blocking effect of the Drake Passage on ocean currents and waves. Plain Language Summary: Ambient seismic noises are the ubiquitous and low‐amplitude background signals recorded by the seismic stations worldwide. Microseisms are the strongest parts of ambient noise, which are generated within the oceans by wave interactions. Previous studies of ambient noise or microseisms had been carried out in many regions, but no study had focused yet on the South Atlantic Ocean due to the lack of seismological data. In this study, we computed the probabilistic power spectral densities to analyze the spectral characteristics of oceanic ambient noise around Tristan region in the middle of the South Atlantic Ocean. We observe that the microseisms have strong correlations with the local wave heights, indicating that local wave interactions are dominant sources here. The analysis of ambient noise cross‐correlations shows there are distant sources for this region obscured by dominant local sources. Based on asymmetry analysis of the ambient noise cross‐correlations, we estimate the direction of the major distant sources. Combined with the correlation analysis with global wave heights model, we identify the predominant distant sources, which are located in the Southeast Pacific Ocean and related to the blocking effect of the Drake Passage on ocean currents and wave systems. Key Points: We analyzed the spectral characteristics of oceanic ambient noise around Tristan da Cunha island in the South Atlantic OceanThe secondary microseisms in the middle South Atlantic are affected by both nearby and distant sources, but local sources are much strongerWe identified the predominant distant source region of secondary microseisms in this region, which is in the southeastern Pacific Ocean [ABSTRACT FROM AUTHOR]

In this paper, a new extended (3 + 1)‐dimensional generalized Kadomtsev–Petviashvili (KP)–Boussinesq equation, with two additional terms utt$$ {u}_{tt} $$ and uxz$$ {u}_{xz} $$, is proposed and investigated. This new equation models both left and right going waves like the Boussinesq equation and describes the transmission of tsunami waves at the bottom of the ocean and nonlinear ion‐acoustic waves in the magnetized dusty plasm. We have constructed one set of breathers and first order periodic waves from the two‐soliton solution. Moreover, the four‐soliton solution consists of two sets of breathers, second order periodic waves, and a hybrid of breathers and periodic line waves. Then, we introduce two kinds of "long wave" limits to obtain the rational and semi‐rational solutions for N=2,3,4$$ N=2,3,4 $$. Under specific parametric constraints, the obtained rational and semi‐rational solutions are nonsingular. The rational solution can be classified as first order line rogue wave, single breather, second order line rogue wave, double breather, a hybrid of breather and line rogue wave, a hybrid of breather, and single soliton. The semi‐rational solution can be classified as the first and second order kink‐shaped rogue wave, a hybrid of breather and one (two) soliton(s), a hybrid of a set of breathers, and a single soliton (breather). In addition, we give Theorem 2.1 for the higher order rational solutions. [ABSTRACT FROM AUTHOR]

An efficient mathematical model is presented for predicting the transfer of ocean waves to ice shelf flexure along two‐dimensional transects. The model incorporates varying ice shelf thickness and seabed bathymetry profiles, and is able to predict responses of large ice shelves over a broad frequency spectrum. The model is used to generate displacement and strain transfer functions for the Ross Ice Shelf (RIS) using geometries from the Bedmap2 data set. The transfer functions are validated against recent observations and used to study the influence of geometrical variations on strain transfer close to the shelf front. Predictions of RIS strain in response to example irregular incident swell and infragravity waves are generated over a wide region, and show similar maximum strains but contrasting spatial strain patterns. The model and results provide a basis for studying destabilizing impacts of ocean waves on the RIS. Plain Language Summary: The outer margins of Antarctic ice shelves bend and flex rhythmically in response to ocean waves, which imposes potentially damaging stresses and strains on the shelves. We model the flexural response of the world's largest ice shelf, the Ross Ice Shelf (RIS), to ocean waves. We incorporate reflection of incident waves from the open ocean by the shelf front, and realistic ice shelf and seabed geometries. We validate the model using recent groundbreaking observations, and show that the RIS experiences large strains in response to a broad range of ocean waves, from swell generated by storms over the ocean to infragravity waves generated at distant coastlines. The predictions will underpin improved understanding of RIS stability, and, thus, contribute toward more accurate projections of global sea level rise. Key Points: Model predictions of Ross Ice Shelf flexure in response to ocean waves, incorporating real shelf thickness and seabed profilesModel validated against observations, and swell and infragravity waves found to generate maximum flexural strains of similar magnitudePredictions will empower studies of ocean wave influence on crevasse expansion, rift propagation, and iceberg calving [ABSTRACT FROM AUTHOR]

Seismic waves from earthquakes recorded on the seafloor are composed of complex multiple arrivals. Here, distributed acoustic sensing (DAS) observations along a cable located offshore the Sanriku Coast, Japan, show that the local earthquake wavefield is particularly rich in Scholte waves. We introduce a processing pipeline to extract these surface waves from DAS records. We then invert hundreds of dispersion curves along a section of the cable to form a shallow high‐resolution shear‐wave velocity model. Moreover, we focus on the possible generation mechanisms of Scholte waves through a series of 2D and 3D full‐wavefield numerical simulations. We show that water phase reverberations greatly contribute to the generation of Scholte waves on the ocean floor. This study demonstrates the potential of DAS to observe and better understand a poorly known marine wave phenomenon and image the offshore shallow seismic structure with an unprecedented spatial resolution. Plain Language Summary: Distributed acoustic sensing (DAS) is a measurement technique that has recently demonstrated its utility for marine geophysics. DAS offers the possibility to observe the seismic wave at a scale and an extent previously unattainable with traditional passive seismic surveys. Here, we use a linear DAS array located offshore the Sanriku Coast, Japan. We propose a processing pipeline to extract surface waves from local earthquake DAS records and obtain hundreds of measurements along the cable. These measurements are used to infer a high‐resolution model of the near‐shore subsurface. Supported by a series of numerical simulations, we suggest that acoustic reverberations in the water column greatly contribute to the generation of surface waves on the ocean floor. This study further demonstrates that DAS can be used to understand marine wave phenomena better and image offshore seismic structures. Key Points: Passive high‐resolution Vs imaging of shallow sedimentary layers with ocean‐bottom distributed acoustic sensing and low‐magnitude earthquakesGridded slant‐stack method to extract Scholte waves from local earthquake wavefieldsFull‐wavefield simulations suggest that water phase reverberations generate Scholte waves at the ocean floor [ABSTRACT FROM AUTHOR]

Observations of ocean surface waves at three sites along the northern coast of Alaska show a strong correlation with seasonal sea ice patterns. In the winter, ice cover is complete, and waves are absent. In the spring and early summer, sea ice retreats regionally, but landfast ice persists near the coast. The landfast ice completely attenuates waves formed farther offshore in the open water, causing up to a two‐month delay in the onset of waves near shore. In autumn, landfast ice begins to reform, though the wave attenuation is only partial due to lower ice thickness compared to spring. The annual cycle in the observations is reproduced by the ERA5 reanalysis product, but the product does not resolve landfast ice. The resulting ERA5 bias in coastal wave exposure can be corrected by applying a higher‐resolution ice mask, and this has a significant effect on the long‐term trends inferred from ERA5. Plain Language Summary: Ocean waves facilitate coastal erosion in the Arctic (and worldwide). Wave energy reaching Arctic coasts is controlled by seasonal sea ice, which includes landfast ice attached to the coastlines or sea floor, and mobile pack ice further seaward. Wave energy in the Arctic is increasing due to the loss of pack ice, and these effects are generally well‐represented in regional climate models. Landfast ice continues to form at the coast each year; when it lasts longer than pack ice, it provides protection against wave erosion. However, landfast ice is difficult to include in models which can lead them to overestimate the wave energy reaching the coasts. Using observations of waves from three coastal sites in Alaska, we demonstrate the importance of including landfast ice into regional models, and propose an effective method of combining public datasets to account for its effects on waves. These results can help the research community predict how much wave energy will be available for coastal erosion processes in the coming decades. Key Points: Year‐long observations show a seasonal cycle of wave exposure at three sites along the Arctic coast of northern AlaskaThe persistence of landfast ice in the late spring/early summer dramatically reduces the wave energy reaching the coastCoastal protection by landfast ice is not represented in global climate models, but it can be parameterized [ABSTRACT FROM AUTHOR]

Eulerian and Lagrangian measurements of orbital velocities in waves approaching a beach are analyzed with the goal of understanding the relative influence of wave‐by‐wave variations in mean‐water level, wave height and incipient wave breaking on mass transport properties of waves in the surf zone. It is shown quantitatively that elevated local mean‐water level correlates positively with increased Lagrangian mass transport at the free surface. Eulerian ADV measurements in the fluid column suggest that the depth‐integrated wave‐by‐wave mass transport also correlates positively with the local mean‐water level, and is only weakly linked to wave height and wave‐breaking events. Plain Language Summary: A sea state is defined broadly by an average wave period and an average perceived (significant) wave height, but wave heights and periods of individual waves may differ significantly from these average values. The differences between individual waves are exacerbated as the waves approach the shore and interact with the bottom topography in shallow water. In particular, the mean‐water level may vary from wave to wave. In the present study, particle tracers are used in connection with stereo imaging to study particle trajectories in waves approaching a beach. Particle positions and trajectories are found using data analysis of individual camera frames. In addition, fluid velocities are measured directly using acoustic Doppler velocimetry. It is found that the most significant factor in the overall horizontal fluid velocity and net transport of particles by an individual wave toward the beach is not the wave height or period, but the local mean‐water level, that is how the average wave elevation in a single wave is situated with respect to the sea bed. Key Points: Measurements of Lagrangian and Eulerian velocities are combined with pressure sensor data to explore wave properties in the surf zoneWave‐by‐wave oscillations of mean‐water level exert a strong influence on mass transport in the fluid columnThe motion of Lagrangian tracers is well matched by dispersive long‐wave theory [ABSTRACT FROM AUTHOR]

With the role of surface winds in the generation of ocean waves, secondary microseisms induced by ocean wave‐wave interactions represent a unique interconnection between the solid Earth, the ocean and global atmospheric circulation patterns. In this study, temporal changes in the ocean generated seismic wavefield in Northeast Atlantic are monitored offshore West of Ireland using ocean bottom seismometers located on top of a thick sedimentary basin. Comparisons with numerical seismic simulations and ocean wave model hindcast data suggest those variations are correlated with changing patterns in ocean wave‐wave interactions closely linked to secondary microseism generation areas. Here we show how those changes, accentuated by the specific structure of the Irish offshore margin, reveal the signature of the North Atlantic Oscillation (NAO) in the Earth's background seismic wavefield. In the North Atlantic, secondary microseism sources likely fluctuate with the changing storm track in response to variations in the NAO. Plain Language Summary: Ocean waves continuously generate seismic waves at the seafloor that are observed all over the world. In this study, we show how such vibrations recorded at the seafloor offshore West of Ireland are sensitive to long term weather and climate fluctuations in the Northeast Atlantic. Combining ocean wave and seismic simulation models with observations, we show that the North Atlantic Oscillation (NAO) climate index is hidden in the seismic records. Key Points: Fluctuating secondary microseism sources in the Northeast Atlantic highlight the variability of the NAO climate index through timeAmbient seismic noise recorded at key locations on the seafloor exhibits detailed sensitivity to global atmospheric circulation patternsTemporal changes in the modal excitation of secondary microseism Rayleigh waves reveal changing patterns in local ocean wave‐wave interactions [ABSTRACT FROM AUTHOR]

The widely recognized global phenomenon of wave-seabed interactions and the resulting secondary stratification processes are complex and poorly understood. To better understand the mechanisms by which the differentiation between fine-grained and coarse-grained materials occurs and how new sedimentary sequences form, laboratory flume experiments were performed under varying wave conditions using natural silty sediment samples collected from the Yellow River Delta (China). Detailed observations led to the description of variations in the grain-size composition and texture of sediment under waves of progressively increasing height and the recognition of the typical, secondarily formed seabed stratification that forms during processes of increasing pore pressure and subsequent liquefaction. The development of a stratified seabed, which is characterized by a superficial fluid mud layer, a subsurface that alternates between coarse and fine sediment banding, and an internal liquefied layer from top to bottom, is closely related to wave-driven pore-water flow through the sediment. Localized fluidization and the onset of piping leads to progressive changes in the grain composition with initial particle dislocation, the development of macro-voids and micro-conduits and, finally, pipe formation. Internal liquefaction occurs in the presence of a critical value of excess pore pressure, during which most fine particles can be scoured by the pore-water flow along the sliding surface while the coarse sediment grains settle, leading to a more compact, homogeneous seabed. These elements are combined to produce the first model of wave-induced stratification initiation and evolution in an originally uniform silty seabed. In addition, the implications of this model for future studies are explored. [ABSTRACT FROM AUTHOR]