Orals: Tue, 5 May, 10:45–12:25 | Room L2
The drift associated with the motion of inviscid, irrotational water waves was first derived by Stokes in the mid 19th century, and is today called Stokes drift. In deep water this takes the form us=a2kωe2kz0, where a is the wave amplitude, k the wavenumber, ω the radian frequency and z0 the initial particle depth. This formally second-order quantity is derived from linear theory, and is implemented in a wide variety of wave models to calculate the motion of marine contaminants and other passive tracers.
Adhering to linear wave theory, superposition allows for the immediate generalisation of the Stokes drift from a single wave to a wave spectrum. However, once more than one Fourier mode is included in the lowest order solution, nonlinear effects occurring at second and third order - chief among them the appearance of bound modes - should be considered when calculating Stokes drift.
We introduce a new, analytical correction to the Stokes drift
us= ∑j aj2ωjkje2kjz0+∑ki>kjωiai2aj2(ki-kj)2(ωi-ωj)-1e2(ki-kj)z0
under assumptions of unidirectional waves and deep water for analytical simplicity - and test this using direct numerical integration of particle paths [1]. Velocity fields for numerical work up to third order are obtained from the reduced Hamiltonian formulation of the water-wave problem due to Zakharov [2], and allow for the inclusion or exclusion of bound harmonics, amplitude evolution and dispersion correction to distinguish among competing effects. In particular, on the typical scale of particle motion the amplitude evolution can be neglected, allowing us to use an algebraic expression for the velocity field in terms of the (initial) Fourier amplitude spectrum [1]. Such an approach has also been successfully employed for deterministic forecasts of the ocean surface [3].
To summarise: we show how higher order contributions to the Stokes drift have an effect throughout the water column. At the surface this is connected to the critical role of high frequencies in the Stokes drift, where dispersion corrections are most influential, as well as contributions from sum-harmonic terms. At greater depths difference harmonics can come to dominate the flow-field and therefore the Stokes drift, as previously demonstrated for wave groups. All of this points to a need to reconsider the common formulation stemming from linear wave theory.
References:
[1] R. Stuhlmeier, Wave-induced drift in third-order deep-water theory, arXiv:2507.15688 (2025).
[2] R. Stuhlmeier, An introduction to the Zakharov equation for modelling deep water waves, D. Henry (ed.) Nonlinear Dispersive Waves (Springer Lecture Notes in Mathematical Fluid Mechanics), Springer (2024), pp. 99-131.
[3] M. Galvagno, D. Eeltink, and R. Stuhlmeier, Spatial deterministic wave forecasting for nonlinear sea-states, Physics of Fluids, (2021) 33 102116
How to cite: Stuhlmeier, R.: On the higher-order wave-induced drift in deep water, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4780, https://doi.org/10.5194/egusphere-egu26-4780, 2026.
Semi-analytical studies have demonstrated that water compressibility, seabed elasticity, and gravitational potential modify tsunami phase speed and can explain systematic arrival-time deviations observed in farfield measurements [1]. However, operational and research tsunami models remain based on incompressible formulations, preventing explicit simulation of acoustic modes and limiting investigation of gravity–acoustic coupling in large-scale free-surface flows.
We present the derivation and numerical implementation of a compressible set of water-wave evolution equations compatible with the widely used finite-volume tsunami modelling frameworks. Starting from the compressible Euler equations, the formulation retains weak compressibility and acoustic propagation while preserving the long-wave structure required for basin scale simulations. Particular attention is given to the pressure closure, dispersion relation, and numerical consistency with existing solvers.
The equations are being implemented within an open-source solver and validated against analytical limits and controlled numerical benchmarks. Preliminary results demonstrate stable coexistence of surface-gravity and acoustic modes, recovery of expected dispersion behaviour, and improved consistency of wavefront propagation speed relative to incompressible formulations. Synthetic impulsive source experiments of landslides illustrate the generation and radiation of coupled hydroacoustic–surface wave fields and their sensitivity to compressibility effects.
The proposed framework provides a physically consistent pathway for extending dispersion based corrections into fully time-dependent numerical models, which enables systematic investigation of gravity–acoustic coupling, compressibility effects, and wave–acoustic energy partitioning in long-wave ocean dynamics. The formulation also establishes a foundation for coupling numerical wave physics with hydroacoustic observations in future integrated modelling studies.
Reference
[1] A. Abdolali, U. Kadri, & J. Kirby, 2019. Effect of Water Compressibility, Sea-floor Elasticity, and Field Gravitational Potential on Tsunami Phase Speed. Scientific Reports, 9 (1), 1-8.
How to cite: Kadri, U., Hunt, M., Abolali, A., Kim, J., Omira, R., and Ramalho, R. S.: Compressible water-wave evolution equations for coupled gravity–acoustic modelling of long ocean waves, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21071, https://doi.org/10.5194/egusphere-egu26-21071, 2026.
The nearshore region provides the link between the land and the ocean. Waves play a crucial part in many nearshore processes including sediment transport, coastal erosion, dispersion of pollutants, rip currents, and many more. It is also the region where most people interact with the ocean. Nevertheless, the nearshore is not well presented in operational wave forecasts.
Here we test the merit of resolving the nearshore region in a regional WAVEWATCH III ® setup. We test this for two contrasting wave climates: the swell-dominated west coast of British Columbia with tidal ranges up to 4m, and the fetch-limited, non-tidal western Baltic Sea with storm surges reaching +-1.5m. Both models are on unstructured grids, and we test the feasibility of zoomed-in regions of very high grid resolution. The effect of currents and water level are evaluated as additional forcing fields.
The models are validated against in-situ wave buoy observations including an array that tracks the wave evolution along two 2km shoaling paths. Gradual wave height reductions of >25% per km are observed, but little change in the spectral shape or directional characteristics.
These observations are challenging to replicate in the model. We find that the inclusion of currents and water level yield the strongest improvement on significant wave heights and directional spreading, whereas increased grid resolution is beneficial for resolving small-scale bathymetric features.
How to cite: Gemmrich, J., Brooks, B., and Holtermann, P.: Modelling and monitoring waves in the nearshore region, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8446, https://doi.org/10.5194/egusphere-egu26-8446, 2026.
Global information about ocean wind waves is crucial for understanding their role in the climate system, validating model outputs, and assessing risks for shipping and marine structures. Recent advances in marine radar technologies have enabled accurate, high-resolution measurements of surface wind waves and their spectral characteristics. Making these measurements available in real-time opens a wide new range of products for many user communities. Here we introduce SeaVision, a ship-based monitoring system that, once integrated into a standard shipborne X-band radar, considerably improves real-time observational networks along major shipping routes. SeaVision automatically measures significant wave height, peak period and directional wave spectra at temporal resolutions down to seconds. First developed for research purposes in 2020, SeaVision passed an extensive period of validation using Spotter wave buoys and satellite data. Validation onboard research vessels was conducted for a wide range of latitudes, from the Arctic to Antarctica. SeaVision is fully operational, cost‑effective, and capable of transmitting wave parameters continuously via satellite. Further developments of SeaVision allow for retrieving near surface wind speed, surface currents and ice parameters with the same resolution. Extensive installations of SeaVision (as well as similar systems) onboard commercial and research vessels allow for establishing a near-global observational network (as a part of GCOS and GOOS) largely exceeding capabilities of the present VOS network which over the last few decades are experiencing a dramatic decline and is also regionally complementing satellite missions. SeaVision will enhance coverage of the so far inadequately sampled global oceans.
How to cite: Gulev, S., Ezhova, E., Natalia, T., Gavrikov, A., Sharmar, V., Trofimov, B., Bargman, S., Koltermann, P., Grigorieva, V., and Suslov, A.: Real-time open ocean wind waves from navigation radars for a truly global wind wave operational observing system, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7925, https://doi.org/10.5194/egusphere-egu26-7925, 2026.
Extreme wave events are recurring meteorological and oceanographic hazards that have a significant impact on coastal regions, leading to infrastructure damage, beach erosion, and adverse effects on fisheries and port operations, resulting in substantial economic losses in Chile. In recent decades, both the frequency and intensity of extreme wave events have increased, and this trend is projected to continue due to climate change, making Chile's extensive coastline particularly vulnerable. In this context, having access to accurate and high-resolution coastal wave forecasting is crucial for coastal users and stakeholders involved in assessing and managing the risks associated with extreme wave events. Here, we present a high-resolution coastal wave forecasting system, which is validated using in situ measurements in Valparaíso Bay. Additionally, an impact-based extreme wave intensity scale has been developed to improve risk communication, support the issuance of official early warnings, and enhance emergency response. A five-category scale, derived from a qualitative analysis of historical impacts on beaches and coastal infrastructure, is fully integrated into the forecasting system. Video cameras have been installed to provide real-time broadcasts of the coastline, facilitating continuous monitoring of wave conditions and their impacts during extreme wave events. Furthermore, the information is disseminated through a dedicated public website and various social media platforms to effectively communicate warnings and promote preventive actions. Key national public institutions responsible for issuing warnings and managing emergencies participate in the information flow, thereby strengthening risk governance and public decision-making, and increasing confidence in the reliability of the coastal wave intensity forecasts.
How to cite: Aguirre, C., Correa, S., Molina, M., and Bahamondez, S.: Impact‑based extreme‑wave intensity scale for high‑resolution coastal forecasting, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19619, https://doi.org/10.5194/egusphere-egu26-19619, 2026.
Extreme swell events along the Peruvian coast pose recurrent risks to coastal communities, infrastructure, and maritime activities. These events originate far offshore, with their sources varying seasonally: during the austral winter they primarily develop in the South Pacific, while in summer they are typically generated in the western North Pacific. This study investigates the atmospheric circulation patterns associated with extreme wave events along the Peruvian coast generated in both hemispheres, with particular emphasis on the characteristics of the upper-level jet. Furthermore, the potential influence of climate change on the intensity of these events is assessed using an analogue-based methodology.
Events classified by the Peruvian Directorate of Hydrography and Navigation as very strong were selected for those originating in the Southern Hemisphere (SH), whereas strong events were selected for those originating in the Northern Hemisphere (NH). This difference is because events originating further away experience greater dissipation and therefore tend to be weaker. Using ERA5 reanalysis data, a composite analysis of atmospheric circulation revealed characteristic patterns in each hemisphere. SH events were associated with a dipolar cyclonic–anticyclonic pattern, producing strong pressure gradients, intense southwesterly surface winds, and an almost barotropic vertical structure. In contrast, events originating in the western North Pacific were linked to a deep cyclonic system, also exhibiting a barotropic structure. Complementing these results, analysis of the upper-level jet across multiple parameters indicates a more intense and latitudinally confined jet, generally exhibiting a positive tilt in both hemispheres. However, a key hemispheric difference emerges: in the SH, these features correspond to the polar front jet, whereas in the NH they reflect a strengthening of the subtropical jet.
Finally, to assess the anthropogenic influence on 10-m wind intensity between past and present periods, a flow-analogue approach was applied. In the SH, atmospheric circulation similar to those observed during the events is associated with stronger winds in the recent period. This intensification appears to be partly driven by the positive trend in the Southern Annular Mode, linked to anthropogenic ozone depletion and greenhouse gas forcing. In contrast, for events originating in the NH, the anthropogenic signal is less evident due to the pronounced interannual and interdecadal variability of the North Pacific, resulting in analogue-based reconstructions that show wind intensification in some events and weakening in others. Overall, these results highlight the distinct atmospheric dynamics governing swell generation in each hemisphere and provide insights that may inform early-warning systems, coastal risk assessments, and long-term adaptation strategies for Peru.
Acknowledgments: This work was supported by the SAFETE project, which has received funding from the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement No 847635 (UNA4CAREER).
How to cite: Agurto Barragan, G., Collazo, S., and García-Herrera, R.: Atmospheric and Climate Drivers of Extreme Swells Along the Peruvian Coast, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1676, https://doi.org/10.5194/egusphere-egu26-1676, 2026.
Exchanges of momentum and energy across the sea surface microlayer (SML) are controlled by turbulent dynamics within the first millimeters above/below the wavy water surface. Wind-generated waves, ubiquitous at the ocean surface, strongly influence turbulent processes in the air and water near the surface, especially as the waves grow and (microscale) break. Surface-active substances, commonly found in coastal waters, are known to dampen waves over a wide range of scales. However, the influence of these surfactants on the coupled air-water flow dynamics and associated fluxes remains unclear. Indeed, some of the phenomena involved take place at a sub-millimeter scale, which makes it challenging to investigate the complex mechanisms at stake.
A combination of two experimental techniques (PIV, particle image velocimetry, and LIF, Laser Induced Fluorescence) with a high resolution (33 µm/pixel for the PIV and 55 µm/pixel for the LIF) were used to determine flow motions on both sides of the SML. The complex set-up was installed at a fetch of 15.5m at the 24-m long, 1-m wide, 1-5m high wind wave tank of the University of Hamburg (Germany) which is specially designed for studies with surfactants (Oleyl Alcohol, OLA in this work). Here, we focus on conditions with a reference windspeed of 4.5m/s measured by an ultrasonic anemometer at 64 cm above the water surface.
The wide field of view (51cm) enables us to capture the evolution in time and space of turbulent shear stress above and below individual wind waves. As the waves move through the field of view, steepen and microbreak, high magnitude turbulent shear is produced in the airflow past the wave-crest and can sometimes spread over several wavelengths when intense air-flow separation events occur. A quadrant analysis shows that negative momentum flux (Q1 and Q3) events are usually encountered before wave-crests whereas positive momentum fluxes (Q2 and Q4) events are produced past them on average. In the water, positive turbulent shear stress mainly shows up below the windward side of the waves, while negative turbulent shear is present below their leeward sides. An estimation of the viscous and turbulent energy dissipation integrated over the first centimeter underneath the water surface shows that the production of bound capillary waves enhances the energy dissipation, which becomes more intense as the capillary train grows up.
When surfactants are present, a reduction of sweeps and ejections (Q2 and Q4) past the dampened wave crests is notable and can be associated with the reduced occurrence and intensity of air-flow separation events. In the water, the removal of most capillary waves leads to a reduction in energy dissipation, as well as in the (phase) averaged turbulent kinetic energy below crests.
How to cite: Tondu, C., Buckley, M., Gade, M., and Marcelo Morales Meabe, J.: Laboratory study of turbulent momentum and energy fluxes above/below microscale breaking wind waves, and influence of surfactants, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14205, https://doi.org/10.5194/egusphere-egu26-14205, 2026.
Results from a suite of simulations with a version of the Norwegian Earth-System Model which includes an ocean surface-waves (OSW) component, WW3, are presented.
OSW are forced by surface winds in the control integration and may be additionally coupled to atmosphere, ocean and sea-ice components through several parametrisations dependent on wave-supported stress, wave significant height, Stokes drift, and wave radiant stress.
Significant effects on the simulated model climatology are found for each of such additional couplings.
However, for the processes considered, the effects of two-way coupling between atmosphere and OSWs, or between sea-ice and OSWs, are highly dependent on the model background climatology -- and therefore also on model systematic biases.
By contrast, additional mixing caused by Langmuir turbulence systematically causes the ocean mixed layer to deepen, with a robust impact on sea-surface temperatures (SSTs), viz mid-latitude cooling in the summer hemisphere, and mid-latitude warming in the winter hemisphere.
Replacing the dynamic OSW model, WW3, with an analytical scheme predicated on a local equilibrium sea-state (Li et al., 2017) to drive Langmuir mixing gives similar results, with a slight exaggeration of the deepening especially in the tropics likely due to missing wind-wave misalignment in the analytical formulation.
How to cite: Ali, A., Bentsen, M., Breivik, Ø., Carrasco, A., Debernard, J. B., Ellevold, T., Michel, C., and Toniazzo, T.: Including dynamic ocean surface waves in NorESM climate simulations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12764, https://doi.org/10.5194/egusphere-egu26-12764, 2026.
Accurate prediction of surface waves under tropical cyclones requires realistic representation of storm-induced ocean currents, which can strongly modulate wave growth and propagation. This study synthesizes results from a coupled modeling investigation and an observational analysis using drifting buoys deployed in four Gulf of Mexico hurricanes: Ian (2022), Idalia (2023), Helene (2024), and Milton (2024). The modeling system consists of the WAVEWATCH III wave model coupled to the Modular Ocean Model 6. The ocean model uses a mixing scheme that explicitly includes wave-induced Langmuir turbulence enhancement, resulting in reduced surface Eulerian currents that are more consistent with observations. The surface current introduced in the wave model combines the Eulerian current and the enhancement of the dominant wave group velocity arising from nonlinear interactions with coexisting waves. Idealized experiments show that omitting surface currents leads to systematic overestimation of maximum significant wave height by up to ~9%, with similar sensitivity to the specification of the upper-ocean mixing scheme. In real storms, drifter-based validation confirms that neglecting storm-induced currents results in consistent overestimation of significant wave height and peak period, particularly in regions of strong currents. These current-induced reductions in wave energy occur primarily because dominant wave packets propagate more rapidly and spend less time under intense winds. The effect is strongest in deep water but remains substantial in intermediate depths (20–70 m), where most observations were collected. Together, these results provide compelling evidence that storm-driven currents frequently reduce wave heights and periods under tropical cyclones. Incorporating realistic surface‐current effects into operational models is therefore essential for improving wave forecasts in tropical cyclones and enhancing coastal hazard assessments.
How to cite: Ginis, I., Papandreou, A., and Hara, T.: Wave Reduction by Storm-Driven Ocean Currents in Tropical Cyclones: Coupled Modeling and Drifting Buoy Observations , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4294, https://doi.org/10.5194/egusphere-egu26-4294, 2026.
This study investigates wave-driven Langmuir turbulence (LT) in an idealized, depth-varying coastal channel representative of an estuarine bay or tidal river. In the open ocean, LT is a key turbulent process in the surface boundary layer, controlling the transport and mixing of momentum and density. LT arises from wave-current interactions that generate wind-aligned vortices, often visible as surface windrows of aggregated buoyant material such as plankton, bubbles, oil, and microplastics. To examine how LT influences the wind-, tide-, and density-driven circulation in a coastal channel, we develop a turbulence-resolving large eddy simulation (LES) framework with terrain-following coordinates representing a deeper central channel flanked by shallower margins. LT is generated through the Craik-Leibovich (CL) vortex force, which incorporates Stokes drift from wind-driven surface gravity waves. The simulations show that LT substantially enhances turbulent mixing, reducing vertical stratification and shear. Faster tidal currents in the deeper channel differentially advect salt, producing tidally varying lateral salinity gradients. These gradients generate baroclinically driven lateral and vertical tidal currents, whose development is both accelerated and intensified by LT. Conversely, vertical stratification and vertical shear of lateral currents can inhibit LT. Additionally, lateral shear of along‑channel currents associated with the channel bathymetry produces channel‑wide pairs of vertical vorticity that are tilted by Stokes‑drift shear, forming strong and persistent lateral circulations. Overall, the results reveal complex two‑way interactions between LT and the mean circulation, demonstrating that LT significantly modifies both tidally resolved and tidally averaged channel dynamics.
How to cite: Kukulka, T., Thoman, T., and Sullivan, P.: Langmuir turbulence in a depth-varying coastal channel: Insights from large eddy simulations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3198, https://doi.org/10.5194/egusphere-egu26-3198, 2026.
Posters on site: Mon, 4 May, 14:00–15:45 | Hall X5
A comprehensive analysis of direct wind stress estimation is performed from a field campaign measurements carried out in the Gulf of Mexico. Air-sea interaction spar buoys were deployed and operated at three locations in order to study ocean-atmosphere interactions under a variety of meteorological conditions. Variability of atmosphere and ocean conditions is a very important issue that provide us with the best analysis of the influence of wave direction in the relative direction of wind stress upon the mean wind direction. Results of relatively simple cases with only one wave system show a gradual direction change of wind stress very much associated with the relative wave direction with respect to wind, specially under low to moderate wind conditions. These type of conditions are always more frequent in the ocean generally. When the calculation of the wind stress is performed in a reference frame aligned with wave propagation direction, a clearer evidence of the wave coherent stress component is observed. Main results of this work are obtained in such a coordinate system aligned with the waves claiming the paramount importance of the wave-coherent stress. The effect of multiple wave systems in the wind stress is addressed taken considering special conditions when atmospheric fronts were present in the region. The ultimate goal is to provide a proper parametrization of the momentum transfer to be used in the next generation of numerical models.
How to cite: Ocampo-Torres, F. J.: The influence of waves in wind stress direction as from the analysis of buoy direct measurements., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22146, https://doi.org/10.5194/egusphere-egu26-22146, 2026.
Air-sea heat flux intensifies during cold airs and other strong weather events. However, due to the lack of long-term observations during such cold air processes, the quantitative enhancement of air-sea heat flux and its underlying mechanisms remain poorly understood. To address this issue, based on a tower-based platform in the southern Bohai Sea, a high-frequency turbulence measurement system was implemented to conduct a two-year air-sea flux measurement, collecting air-sea heat flux data covering 20 cold air outbreak events. This study quantitatively analyzes and reveals the pronounced variations in air-sea sensible heat flux of SHF and latent heat flux of LHF during cold air events, as well as the distinct roles of wind speed, air-sea temperature difference and specific humidity difference. The enhancement of SHFand LHF is further quantified. Our results show that the significant increases in wind speed and air-sea temperature difference are the primary drivers of the enhanced heat flux. Although LHF exhibits higher magnitude than SHF during cold air processes, LHF is predominantly controlled by increased wind speed, whereas SHF is mainly influenced by both wind speed and the air-sea temperature difference, with its enhancement being substantially greater than that of LHF. Compared to calm weather conditions, SHF and LHF under cold air conditions increased by an average of 12.8 and 1.6 times, respectively, while the total heat flux increased by 2.6 times on average. The increasement of heat flux can exceed 10 times during cold waves, even can reach the magnitude comparable to that observed during tropical cyclones.
How to cite: Wu, S. and Qiao, F.: Enhanced Air-Sea Heat Flux during Cold Air Events: Observations and Mechanism Analysis, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22828, https://doi.org/10.5194/egusphere-egu26-22828, 2026.
The interaction between wind and water waves is a complex process at the interface of two turbulent fluids. In this context, lakes provide conditions of intermediate complexity between the open ocean and wave tank experiments, allowing the investigation of fetch-limited wave responses under both directional and turbulent wind regimes, and in the absence of swells.
We developed an experimental setup installed on the LéXPLORE research platform on Lake Geneva (Switzerland) [1] to record the spatial and temporal variations of the water surface elevation using a pair of stereo cameras, as well as in situ wind profiles obtained with ultrasonic anemometers. To reconstruct the surface elevation and generate local directional spectra, we employ the optimised WASS algorithm [2], which has already proven effective during oceanic expeditions. The motion of the platform is tracked using an inertial measurement unit, which also helps refine wind-speed estimates. Moreover, the wave data are compared with in situ measurements acquired by buoys.
The LéXPLORE platform is ideally located for our study, as it simplifies the physical analysis and interpretation of the measurements. It lies far enough from the coast to ignore boundary effects, in deep water where bathymetry influences on wave propagation can be neglected, and at long fetch (for south-westerly winds) where wind forcing is maximised.
We will present the experimental setup and preliminary results on the reconstruction of directional spectra under different wind regimes during an experimental campaign in Spring 2026.
[1] Wüest et al., WIREs Water 8, e1544 (2021)
[2] Bergamasco et al., Computers and Geosciences 107, 28 (2017)
How to cite: Kunz, B., Brunetti, M., Babanin, A., and Kasparian, J.: Experimental setup and first measurements of wind-wave interaction from the LéXPLORE platform on Lake Geneva, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6877, https://doi.org/10.5194/egusphere-egu26-6877, 2026.
Accurate forecasting of ocean and climate can provide actionable information for decision-making and ocean governance, which is essential for transferring ocean science to sustainable development. However, huge common biases of ocean, typhoon and climate models hinder our forecasting ability. The programme of “Ocean to climate Seamless Forecasting system (OSF), approved by the UN Ocean Decade in 2022, aims to provide a solution. This presentation will introduce the OSF Programme and what it has achieved.
With huge heat content, ocean controls the evolution of TC and climate. In this regard, ocean is the key to improve forecasting ability. A key breakthrough of OSF is quantifying the dominant role of surface waves in upper-ocean mixing and air-sea fluxes, processes previously omitted in large-scale models. By integrating wave-induced physics into models, OSF has achieved fundamental improvements, reducing summer sea surface temperature bias in ocean models by ~80%, decreasing typhoon intensity forecast error by ~40%, and cutting climate model SST bias by ~60%. OSF further translates science into actions through its global network, innovative low-cost buoy observations, and operational systems such as OCEANUS and COAST, delivering actionable forecasts and tools for disaster risk reduction, ecosystem protection, and coastal resilience.
How to cite: Wang, S. and Qiao, F.: Towards Seamless Ocean-Climate Forecasting: Surface Wave Dynamics and the UN Ocean Decade OSF Programme, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22826, https://doi.org/10.5194/egusphere-egu26-22826, 2026.
A wave-ice interaction coupled model that resolves both ice-induced wave attenuation and wave-induced ice breakage was implemented within the Finite-Volume Community Ocean Model (FVCOM) framework and applied to the Bohai Sea, one of the lowest-latitude seasonally ice-covered seas in the Northern Hemisphere. Multi-source observations were used to validate the simulated wave and sea ice variables. We investigate wave–ice interactions under different ice conditions (mild, normal and severe ice years) and assess coupling effects by comparing a fully coupled (two-way) configuration with an uncoupled configuration and a one-way coupled configuration that accounts only for ice-induced wave attenuation. The presence of sea ice reduces wave energy and alters wave propagation. In turn, wave-driven processes exert complex influences on sea ice, potentially mediated by wave–current interactions, and wave activity can enhance melting along the ice fringe, highlighting the importance of explicitly representing two-way wave–ice interactions for accurately simulating ice-cover dynamics in the Bohai Sea.
How to cite: Qiu, S., Lettmann, K. A., Fujisaki-Manome, A., Wang, J., and Chen, X.: Fully Coupled Interactions between Sea Ice and Waves in the Bohai Sea under Different Ice Conditions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4487, https://doi.org/10.5194/egusphere-egu26-4487, 2026.
Since their inception in the 1990s, the third-generation spectral models, used both for the operational wave forecast and for research, reached significant advances in their performance. This success, however, depends on the criteria for this performance and on the aims of the model usage. In the presentation, we will discuss what is missing and what applications require attention, revision or further development of model physics.
We will argue that the main problems, as far as the traditional aim of spectral models is concerned – the wave forecast, is with predicting swell, wave-current interactions and directional spectra of wind-generated waves. Swell is poorly predicted in terms of the wave height, but arrival time is its particular problem - swell can be up to 20 hours early or late by comparison to its forecast. We will demonstrate that partially this can be connected to the issue of wave-current interactions.
The problem of directional wave spectra connects us to a new role of wave models – providing the air-sea fluxes into coupled models for large-scale environments such as Atmospheric Boundary Layer, including spray production, tropical cyclone intensity, for modelling the upper ocean, including ocean mixing, air-sea gras transfer, biogeochemistry, for marginal ice zone, among other application, for climate. In the presentation, we will discuss the new criteria for model performances and avenues of reaching the new aims for spectral models in these new applications.
How to cite: Babanin, A.: Wave foecast models: what is missing? , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21550, https://doi.org/10.5194/egusphere-egu26-21550, 2026.
Describing intricate concurrent wave processes frequently proves challenging and unwieldy. Although the influence of reflection rates on the development of extreme nonlinear waves remains poorly understood, controversy has emerged over whether elevated reflection rates amplify nonlinearity in the upper tail of the wave height distribution. Aided by fully nonlinear simulations, we present a theoretical framework that isolates the effects of shoaling length, bottom slope magnitude, and reflection rates. Comparing the simulation results with the theory for steep and reflective slopes, it is noticed that the theoretical excess kurtosis stabilizes for steep slopes with a high reflection rate, and that the simulated kurtosis remains in the confidence interval of our new theory. We therefore conclude that the high reflection rate is the main reason for anomalous wave statistics becoming stable.
How to cite: Mendes, S., Zhang, J., and Benoit, M.: Effect of wave reflection on submerged plane slopes on the evolution of extreme wave fields, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2792, https://doi.org/10.5194/egusphere-egu26-2792, 2026.
Wind-driven gravity–capillary waves play a key role in air–sea interactions and in small-scale energy dissipation across the surface microlayer (SML). Despite decades of studies, the transition from smooth gravity–capillary waves to intermittent microscale breaking under weak wind forcing is still not well understood.
This study investigates gravity–capillary wave dynamics and micro-breaking in a 24 m long, 1 m wide wind–wave tank with a total height of 1.5 m and a mean water depth of 0.51 m. Measurements were performed using a newly developed Colour Imaging Slope Gauge (CISG), providing high-resolution spatio-temporal observations of surface slopes within a 33.2 cm × 26.8 cm field of view (FOV), at a spatial resolution of 0.024² cm² per pixel and a frame rate of 400 Hz. A total of 18 experiments were conducted over a range of low wind speeds (1.8 m s⁻¹– 4.0 m s⁻¹) with small increments. Wire-wave gauge measurements were used to support three-dimensional surface reconstructions.
Spectral, wavelet, and band-pass filtering techniques were applied to isolate capillary-scale features associated with micro-breaking. Particular attention was given to surface curvature as a geometric indicator of micro-breaking. The wide FOV enables direct tracking of isolated events and reveals a clear increase in capillary activity and micro-breaking occurrence with increasing wind forcing.
First results indicate a distinct transitional regime at wind speeds near 2.0 m s⁻¹, where the first clear capillary signatures associated with micro-breaking emerge in the frequency-wavenumber spectra. The CISG successfully captures the spatial onset of
these micro-breaking induced capillaries with wavelengths between 0.4 cm and 3 cm.
By applying wavelet and band-pass filtering, these features were isolated, allowing for the identification of the "birth" of micro-breaking induced capillaries within the FOV.
This work establishes a methodological framework for detecting micro-breaking and provides new insights into the surface conditions governing small-scale dissipation processes in wind-driven wave systems.
How to cite: Morales Meabe, J. M., Gade, M., Tondu, C., and Buckley, M.: Detection of Microscale Breaking in Wind-Driven Waves using a Colour Imaging Slope Gauge (CISG) , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10831, https://doi.org/10.5194/egusphere-egu26-10831, 2026.
Storm surges are phenomena caused by wind conditions of greater magnitude than usual, whether local or remote. The ocean-atmosphere interaction is important in the development of these events, since wind is the main factor that increases wave heights, leading to an increase in their energetic potential. For this reason, the study focuses on characterizing the meteorological conditions that triggered swells categorized as M3, M4 and M5 of the Escala de Impactos de Marejadas developed by the MarejadasUV (MUV) of the University of Valparaíso in the northern, central and southern areas of the country.
Three representative points were selected on the coasts of Chile: in the north (-23°S,72°W), in the center (-32°S,75°W) and in the south (-44°S,78°S). Datasets were extracted every 3 [hrs] for significant wave height, mean period, mean direction and wave energy spectra modeled with WaveWatch III forced with surface wind and sea ice area fraction from the ERA5 reanalysis. With these data, thresholds related to 2, 5 and 10 years of return period were obtained to categorize the events into M3, M4 and M5, respectively, that occurred between May and October from 1979 to 2022, obtaining 29 cases in the north, 28 in the center and 21 in the south.
The northern area was characterized by more remote swell events (24) than local (5). The latter have a similar configuration where the south winds (more commonly known as Surazo) developed swells of the three categories, with different wind magnitude. The remote events were generated by low pressure (LP) formed at different points of the study area mainly located below the 40°S in deep water. In the center area, there were a greater number of local events (8), which in addition to being formed by south winds were also formed by LPs developed near the study point and the shore. This last configuration being similar for the remote events (20), but the distance which they were developed was greater. In the southern area, there were more local events (17) than remote events (4), mainly formed by a LP that were formed nearly the study point.
In conclusion, the categorization of these events depends on the wave climate. Most of the local events in the north and center were formed by winds from the south. The rest of the events are developed by LPs originated in different parts of the study area.
How to cite: Vasquez, M., Garreaud, R., and Aguirre, C.: Synoptic characterization of extreme wind-wave events in Chile, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14883, https://doi.org/10.5194/egusphere-egu26-14883, 2026.
We present a preliminary study on the one-way coupling between the spectral wave model Wavewatch III (WW3) and the hydrodynamic model SCHISM (Semi-implicit Cross-scale Hydroscience Integrated System Model) to investigate wave–current interactions in the Columbia River estuary (USA) and its adjacent coastal ocean. WW3 is implemented on an unstructured grid, enabling high-resolution representation of the spatially complex conditions at the estuary mouth and extending into the open ocean, and it is forced with time-varying currents and water levels from SCHISM simulations. Preliminary results are compared with buoy observations and satellite-derived sea surface heights from the Surface Water and Ocean Topography (SWOT) mission, exploring the potential of these data for model evaluation. The study combines model evaluation using satellite and buoy data with the coupling of wave and hydrodynamic models in an estuarine environment, while highlighting the relevance of unstructured grids for representing fine-scale coastal processes within a broader oceanic context.
How to cite: Fernández, L., Seaton, C., and Haller, M.: Wave–Hydrodynamic Modeling of the Columbia River Estuary Using One-Way Coupling Between SCHISM and WAVEWATCH III on Unstructured Grids, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15527, https://doi.org/10.5194/egusphere-egu26-15527, 2026.
Short wind-wave growth is central to estimating sea-surface drag and air-sea momentum transfer, as it increases surface roughness and facilitates directional wave breaking. Therefore, field observations that resolve the full wind-sea scale are essential for parameterizing air-sea fluxes and validating numerical weather prediction models.
In these efforts, we developed a measurement system with a polarimetric camera integrated into a UAV platform, leveraging RTK-enabled aircraft positioning and an inertial measurement unit for high-precision georeferencing. With varying altitudes, we resolve ocean waves ranging from centimeters to decameters, extending the polarimetric camera’s capabilities to those of wave buoys.
Field measurements were conducted from May to July 2025 on the coast of Rye, New Hampshire, under various conditions, including gusty winds, limited/unlimited fetch, and misaligned wind-swell and current. The observations yield 3D directional wave spectra, resolving wavelengths from 20 m to 6 cm and frequencies from 0.3 to 5 Hz. The directional spreading, current shear, and bimodal peaks are plotted against the mean current direction and wind speed, which were measured by a nearby buoy. With these measurements we aim to explore the dynamics of locally generated surface waves by linking the gravity capillary scales to larger wind-sea.
How to cite: Duvarci, G. and Laxague, N.: Observations of Locally Generated Wind Waves using a Novel Airborne Polarimeter, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16778, https://doi.org/10.5194/egusphere-egu26-16778, 2026.
Wind waves are inherently irregular and random, making the goal of finding a fully deterministic description practically impossible. However, knowing their probabilistic properties is crucial for engineering applications and for understanding ocean dynamics. To deepen this understanding and build more efficient wind-wave models, machine-learning approaches are likely to become increasingly valuable. Recent progress in physics-informed machine learning (PIML) has transformed fluid mechanics by combining data-driven approaches with physical fundamental equations, enabling more robust and generalizable models.
In our study, we apply PIML techniques to identify probabilistic characteristics of wind waves. Our research is based on learning probability distributions directly from data, which allows us to avoid restrictive assumptions or classical approximations.
We utilize field measurements collected in Skulte, Latvia, during August–September 2022. The dataset includes pressure time series and 3D velocity profiles, providing a detailed description of wave dynamics. Building upon existing PIML architectures, we developed a framework capable of inferring an accurate and efficient probabilistic model of wind waves. Preliminary results show promising agreement with theoretical expectations and previous studies.
The dataset was provided by Kevin Parnell and colleagues from Tallinn University of Technology (TalTech), together with the Latvian Institute of Aquatic Ecology. Our findings highlight the potential of PIML for improving probabilistic wave modelling and set the foundation for future applications in coastal engineering and environmental monitoring.
How to cite: Grzonka, L., Parnell, K., and Herman, A.: Data-Driven Study of the Probabilistic Characteristics of Wind Waves in Latvia, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21442, https://doi.org/10.5194/egusphere-egu26-21442, 2026.
