Orals: Wed, 6 May, 14:00–17:55 | Room L2
The marine dynamic model at EcoScience, named FlexSem, model has recently been extended with a set of numerical developments designed to enhance accuracy and stability in realistic marine applications. A new spatial discretization of higher order has been implemented for the horizontal advection of tracers. The method reduces numerical diffusion and improves the representation of sharp gradients, thereby capturing thermocline and pycnocline structures with greater fidelity. In the momentum equations, the surface wind stress parameterization has been revised to include an explicit wind-speed dependency in the drag coefficient formulation. This modification provides a more consistent link between atmospheric forcing and ocean surface response. Furthermore, the agent-based model module has been extended with a diffusive operator, allowing for the simulation of subgrid-scale dispersion in Lagrangian particle tracking. These improvements have been tested across several recent model setups, demonstrating clear benefits to both hydrodynamic and tracer simulations. The enhanced FlexSem system offers a robust and flexible platform for addressing complex marine processes with greater precision.
How to cite: Ishimwe, A., Larsen, J., and Maar, M.: Enhancing Marine Modelling Accuracy: Recent Developments in the FLEXSEM System, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-428, https://doi.org/10.5194/egusphere-egu26-428, 2026.
Hydrodynamic processes in river mouths represent a complex interplay of fluvial discharge, tidal influence, and saline intrusion. Standard marine flow and discharge measurement techniques face significant limitations in estuarine zones, particularly near river mouths, due to complex bidirectional flow patterns and the influence of tidal and saline forces. The peculiar characteristic of the microtidal regime in the northern Adriatic Sea makes the understanding of the hydrodynamic processes at the river mouth extremely complex. Moreover, the Isonzo basin climate condition varies from alpine to sub-Mediterranean. Thus, can introduce large variations in the flow rate of the river (related to precipitation), amplifying an already pronounced intra- and inter-annual variability due to the torrential regime and prolongated drought season.
In this work, we focus on the monitoring system of the Isonzo Current meter, an ADCP (Acoustic Doppler Current Profiler) station fixed at a depth of 13 meters from the river surface, located 7 km far from the Delta Inlet in the Northern Adriatic Sea. The station, operative since 2005, acquires and transmits data every 10 minutes. Continuous measurements of river flow velocity, flow direction, temperature and calculation of the flow rate, have enabled the identification of two distinct river flow regimes: 1) normal condition of low freshwater discharge related to high rising tide and/or drought period, and 2) exceptional high discharge related to freshwater flood events.
In normal and drought conditions we observe that the river water column present an average direction upstream related to: a) marine water intruding the river, b) variation of the river high coinciding to the diurnal tidal modulation, c) discharge fluctional related to the maximum and minim tide, d) stratified water column in the central portion with thin mixing layer at the bottom and surface of the river section, and e) a high temperature (related to the marine water temperature) at the riverbed.
In opposition, during flood events, the flow direction becomes homogeneous in the entire water column, discharging downstream and pushing the tidal force outside the river. The onset of a flood event records a sharp thermal drop, indicating the replacement of the marine water by freshwater throughout the channel and the flow rates can exceed 2500 m³/s.
The presence of a semi-stationary salt wedge intrusion in the river was identified and wide. However, it is not clear how the tide and the river runoff interact in the water mass exchanges, or what are the water mixed or stratified condition in different hydrodynamic regime.
These results are essential for understanding estuarine dynamics, particularly in a climate context marked by increasingly frequent extreme events.
How to cite: Lanzoni, A., Corbo, A., Ferri, L., Arena, F., Mansutti, P., Bubbi, A., Chiaruttini, L., Gustin, S., Schinaia, F., and Brunetti, F.: Preliminary Analysis of Sea Intrusion in the Isonzo river delta Inlet (North-East Italy), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5135, https://doi.org/10.5194/egusphere-egu26-5135, 2026.
Predicting the trajectories of surface drifters is vital for understanding upper-ocean circulation, material transport, and marine hazard response, yet this task remains challenging under multi-forced environmental conditions. Surface motion arises from the nonlinear interaction among winds, tides, mesoscale currents, and surface waves—processes that remain difficult to represent accurately in conventional numerical models.
This study develops a hybrid machine-learning and physics-based framework that integrates multi-source oceanic model outputs (HYCOM, TPXO, SCHISM) with atmospheric and wave forcings from ERA5 to predict surface-drifter trajectories. Within this framework, the eXtreme Gradient Boosting (XGBoost) algorithm predicts surface-drifter velocity components, which are time-integrated to reconstruct trajectories. Model skill is evaluated against drifter observations, and SHapley Additive exPlanations (SHAP) analysis is used to identify dominant environmental drivers controlling surface transport.
Applied to the marginal seas around the Korean Peninsula, the hybrid model reduced 24-hour trajectory root-mean-square error (RMSE) by approximately 38 % and increased the normalized cumulative Lagrangian separation (NCLS) skill score by 54 % relative to SCHISM-based simulations. SHAP interpretation revealed systematic regional contrasts—tidal dominance, mixed forcing, and eddy-driven variability. These findings demonstrate that physics-informed and explainable AI can effectively bridge deterministic modelling with data-driven learning, providing a robust foundation for the emerging Intelligent Ocean forecasting framework.
How to cite: Kim, H., Kim, J.-C., Choi, J.-Y., Kim, D.-Y., and Kim, C.-K.: A Hybrid AI–Physics Framework for Surface Drifter Trajectory Prediction around the Korean Peninsula, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3209, https://doi.org/10.5194/egusphere-egu26-3209, 2026.
Arctic coastlines underlain by ice-rich permafrost are retreating at accelerating rates due to the compounding effects of rising air and ocean temperatures, longer ice-free seasons, and increasing storm activity. Unlike temperate coasts, erosion of unconsolidated, ice-rich permafrost bluffs is governed by a thermomechanical process in which wave-driven heat transfer induces thawing, and hydrodynamic forcing removes the sediment matrix. Despite its significance for coastal hazard prediction, infrastructure resilience, and climate feedback, this coupled process remains poorly represented in existing models, largely because of limited experimental data, logistical challenges associated with long-term field monitoring, and analytical formulations that rely on simplified or weakly constrained parameterizations, particularly for convective heat transfer at the turbulent water-permafrost interface. Here, we present thermalFOAM, a physics-based numerical framework implemented in OpenFOAM, for simulating the ablative erosion of permafrost bluffs under wave forcing. The solver resolves transient heat conduction with phase change through an enthalpy-porosity formulation, incorporates temperature-dependent thermophysical properties, and drives dynamic mesh evolution through a calibrated erosion law. A key innovation is a wave-aware Robin boundary condition that enables spatially and temporally varying thermal forcing based on instantaneous water surface elevation, allowing the model to capture intermittent wetting that governs heat transfer in the swash and surf zones. Validation against laboratory datasets demonstrated that thermalFOAM successfully reproduced the observed niche geometries and retreat rates across the tested parameter space. This integrated framework bridges laboratory-scale process understanding and field-scale prediction, offering an open-source tool for assessing Arctic coastal dynamics under future climate scenarios.
How to cite: Omonigbehin, O., Stolle, J., Francus, P., Kurylyk, B., and Guimond, J.: thermalFOAM: A numerical model for coastal permafrost erosion validated using physical experiments, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5944, https://doi.org/10.5194/egusphere-egu26-5944, 2026.
Modelling oceanic processes in shallow coastal domains presents challenges that are not encountered in open-ocean oceanography, due to strong land-sea interactions and non-linear physical processes. The Horizon Europe FOCCUS project (Forecasting and Observing the Open-to-Coastal Ocean for Copernicus Users) addresses some of these challenges by strengthening the (open) ocean–to–coastal ocean interface through enhanced in-situ and satellite observations, improved hydrological and land-ocean products, and advanced coupling between oceanic and coastal models, whilst exploring data assimilation and machine learning techniques. These developments are demonstrated across twelve coastal applications located in all European oceans.
In this contribution, we present one of these coastal applications based on the Dutch Continental Shelf Model (DSCM), a Delft3D-Flexible Mesh implementation covering the north-western European shelf with a focus on the southern North Sea. The model utilises an unstructured grid to resolve hydrodynamics and sediment transport, and explicitly represents offshore wind farm infrastructure, treating turbines as large, rigid obstacles that interact with the flow. Hydrodynamics, sediment transport and water quality are fully online-coupled and linked to aquaculture modules to assess productivity and yield potential for mussel and seaweed cultivation at offshore wind sites.
Within FOCCUS, the existing framework is improved in three ways: I) through the addition of thermobaric effects to the equation of state, II ) by using enhanced hydrological model results as river inputs and III) by using gap-filled satellite observations as an initial sediment field. The enhanced coupled framework is applied to investigate interactions between offshore wind farms, aquaculture activities, and their combined impacts on water quality in the Southern North Sea. This application demonstrates how unstructured-grid, observation-informed coastal models can support integrated blue economy assessments and reduce uncertainty in operational and strategic decision-making for shallow coastal seas.
FOCCUS is funded by the European Union (Grant Agreement No. 101133911). Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Health and Digital Executive Agency (HaDEA). Neither the European Union nor the granting authority can be held responsible for them.
How to cite: Beyaard, L., Pathak, D., Mészáros, L., and El Serafy, G.: Advancing Ocean Modelling in the Open-to-Coastal Ocean: An Online-Coupled Coastal Application to Assess Multi-use in the Southern North Sea, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9112, https://doi.org/10.5194/egusphere-egu26-9112, 2026.
Accurate wave prediction is crucial for coastal disaster management and maritime safety. Traditional numerical wave models, such as SWAN and WAVEWATCH III, provide physically reliable results but are computationally intensive and time-consuming. However, data-driven deep learning models offer fast prediction capabilities and have therefore received widespread attention in recent years. This study investigates regional wave prediction at Kyauk Phyu in the Bay of Bengal, an important coastal area undergoing ongoing port and infrastructure construction. Moreover, there are a limited number of wave buoys in the Bay of Bengal, which makes data collection difficult.
In this study, the impact of hyperparameter optimization, input feature representation, and physically meaningful variables on the regional wave prediction is evaluated using a CNN-LSTM model. Hourly meteorological and wave data from ERA5 (2020–2023), and water depth information from GEBCO are employed in this study. The model’s hyperparameters are tuned using Bayesian optimization, and the result demonstrates that hyperparameter tuning plays a crucial role in spatiotemporal wave prediction. Subsequently, the performance of univariate and multivariate models is evaluated over different lead times of 1, 6, 12, 18, and 24 hours. The results show that the univariate model performs better for short-term predictions (1–6 hours), while the multivariate model incorporating wind stress and water depth achieves higher accuracy for long-term predictions (12–24 hours). This indicates that introducing more physical factors over a longer forecast period can enhance forecasting capabilities.
Performance evaluation during Cyclone Mocha shows that the model effectively captures high-energy wave events. An ablation method is applied to assess the contribution of additional features to wave-prediction performance. The results indicate that water depth is the most critical factor influencing wave-prediction accuracy, while the wind-stress variable results in only a slight change in prediction performance across all lead times.
How to cite: Thet, P., Tao, A., Fan, J., Thein, S. S., Soe, M. M., Wu, C., Xie, S., Thu, S. M. M., and Paing, M. T.: Wave Height Prediction Using Wind and Local Bathymetry with a CNN-LSTM model: A Case Study at Kyauk Phyu, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9349, https://doi.org/10.5194/egusphere-egu26-9349, 2026.
Tracking meanders of the Agulhas Current and their associated cyclonic eddies is essential for understanding episodic upwelling along the southeast coast of South Africa, particularly near Port Alfred where the inshore jet interacts strongly with the shelf. We developed a new temperature-gradient-based current-core tracker, the Port Alfred Current Tracker (PACT) and applied it alongside a sea surface height-derived tracker (an adapted version of Location of the Agulhas Current Core and Edges, LACCE) and the PY-Eddy-Tracker algorithm to detect meander events and associated cyclonic activity using 22 years of high-resolution CROCO output (WOES36). Using these methods, we detected 2.3 large meander events per year from PACT, 1.7 events per year from adapted LACCE, 0.6 events per year from eddy amplitude, 1 event per year from eddy area, and 1.3 events from eddy radius. Upon inspection of the link between Agulhas Current meanders and upwelling in the Port Alfred region, long-term analysis showed that most upwelling events occur in the absence of a meander and it is weakly correlated with meander or cyclonic eddy activity. Nonetheless, individual case studies reveal that long-lived meanders or cyclonic eddies can locally enhance upwelling. These results indicate that Agulhas Current meanders arise from a combination of coherent eddies and shifts in the core jet but upwelling at Port Alfred is primarily driven by strong, smooth current flow rather than meander-induced variability. Combining current-core and eddy-tracking diagnostics provides a more complete understanding of both meandering and upwelling dynamics along the southeast African margin.
How to cite: Taukoor, S., Samuelsen, A., Ansorge, I., Penven, P., Mashifane, T., and Abiodun, B.: Monitoring Agulhas Current Meanders using Current and Eddy Tracking Algorithms, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3676, https://doi.org/10.5194/egusphere-egu26-3676, 2026.
Climate change, along with sea-level rise and shifting hydrodynamics, threatens coastal systems such as the Wadden Sea. At the same time, nature-based solutions (NbS) have gained prominence in coastal protection, recognizing the buffering role of vegetation such as seagrass. This study evaluates hypothetical seagrass meadow extension scenarios as NbS, assessing their potential to mitigate coastal hazards under present and future climate conditions. Time-slice simulations for the years 1997 and 2090 were conducted using the unstructured-grid SCHISM modeling framework, which couples hydrodynamics, wave action, sediment dynamics, and a vegetation module representing first-order seagrass effects on flow and turbulence. Pairwise simulations under the RCP8.5 scenario with and without vegetation were conducted to quantify attenuation of currents, wave energy, bottom stress, and sediment concentrations. Results show that despite a ~20% decline in relative attenuation efficiency under sea-level rise, seagrass meadows retain substantial damping capacity. Wave heights were reduced by 30% in shallow areas, with even greater absolute reductions in deeper zones of enhanced wave activity. Bottom stress attenuation frequently exceeded 60%, accompanied by lower near-bed sediment concentrations.
Although limited to hydrodynamic effects and time-slice simulations without morphodynamics, this study highlights the continued importance of seagrass in coastal protection and the need to integrate ecological components into climate adaptation strategies.
How to cite: Jacob, B., Pein, J., and Staneva, J.: Evaluation of seagrass as a nature-based solution for coastal protection in the German Wadden Sea under end of the century sea level rise projections, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5079, https://doi.org/10.5194/egusphere-egu26-5079, 2026.
Marine Animal Forests (MAFs) are underwater habitats formed by sessile benthic organisms, whose three-dimensional structure favors the presence of other species resulting in high biodiversity (Rossi et al., 2017). Marine Animal Forests have been severely impacted by recent marine heat waves and industrial fishing activity in the Mediterranean Sea. Conservation planning targeting MAFs requires the definition of a minimal forest unit. In the present study, we aim to define the minimal functional unit of a mesophotic gorgonian forest based on its ability to modify the current flow within the canopy. The effect of canopy density on the mean flow and on the generated turbulence is investigated experimentally in a 26 m open-channel flume. Multi-plane flow measurements within physical model canopies are taken using the telecentric 2D-2C PIV (Particle Image Velocimetry) method. The model canopies consist of 3D-printed scaled surrogates imitating white gorgonians (Eunicella singularis) with a simplified geometry. The four canopies tested here have frontal density λf = [0.033, 0.078, 0.136, 0.235]. Model canopies are tested at two different flow conditions with global Reynolds number Reg = 58*103 and Reg = 85*103, and local Reynolds number in the range of Rel = [64 - 287] and Rel = [132 - 592], respectively, where the local Reynolds number is based upon the model stem diameter. The incident flow is a uniform fully developed turbulent flow over rough bed, generated above a 15.86m array of solid cubes, as those used by Chagot et al. (2020), before reaching the model gorgonian canopy. Double-averaged (in time and in space) flow statistics are used here in order to account for the spatial heterogeneity inside the canopy, and to quantify all components of shear stress, i.e. turbulent and dispersive stress. The flow structure and the bed shear stress within and above the canopy are measured and compared to classical turbulent boundary layer models in and over vegetated canopies for different canopy densities. The presence of a shear layer close to the top of the canopy, defined by the measured deflected height, allows us to attempt to model the mean flow using the mixing-layer analogy for vegetated flows as a function of canopy density.
1. Rossi, S., Bramanti, L., Gori, A., & Orejas, C. (Eds.). (2017). Marine Animal Forests: The Ecology of Benthic Biodiversity Hotspots. Springer International Publishing. https://doi.org/10.1007/978-3-319-21012-4
2. Chagot, L., Moulin, F. Y., & Eiff, O. (2020). Towards converged statistics in three-dimensional canopy-dominated flows. Experiments in Fluids, 61(2), 24. https://doi.org/10.1007/s00348-019-2857-4
3. Nikora, V., McEwan, I., McLean, S., Coleman, S., Pokrajac, D., & Walters, R. (2007). Double-Averaging Concept for Rough-Bed Open-Channel and Overland Flows: Theoretical Background. Journal of Hydraulic Engineering, 133(8), 873–883. https://doi.org/10.1061/(ASCE)0733-9429(2007)133:8(873)
How to cite: Vonta, L., Y. Moulin, F., and Bramanti, L.: Hydrodynamics inside Marine Animal Forests: Investigating the mean flow and turbulence using laboratory scale models and PIV measurements , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6884, https://doi.org/10.5194/egusphere-egu26-6884, 2026.
Oysters protect the seabed from erosion and enable a rich habitat for other species. Direct human actions and climate change, however, have contributed to a decline in the population of Ostrea edulis, an indigenous species commonly known as the flat oyster. The species, which thrived just 150 years ago, is now classified as threatened, and nature-based solutions are being implemented to restore the population to its native environment. A viable nature-based approach is to make use of the material often employed to protect the foundations of large marine offshore structures, enabling the development of oyster reefs on these submerged structural elements.
Flat oyster reefs are characterised by sharp edges and highly varying roughness, which create complex flow patterns and alter oyster feeding efficiency. To understand the operational and optimal conditions for oyster reef stability and growth, an experimental study of flow turbulence on top and around oyster reefs is carried out.
A rigid ultra-rough bed representing oyster reefs over a scour-protection armour layer is installed in a wave flume, and tested under waves, current, and combined wave-current forcing conditions. Wave height time-series and high‑resolution vertical velocity profiles are collected using synchronised wave gauges and an acoustic doppler velocity profiler. The effects of regular wave forcing and steady flows on the near‐bed roughness are then measured.
Maximum bed shear stress, turbulent kinetic energy (TKE), hydraulic roughness and wave friction factors vary depending on the shape of the armor layer rocks and oyster reef elements, which lead to different frictional energy dissipations. To improve turbulence and bed shear stress estimates, near‑bed velocity fluctuations and vertical velocity profiles are measured. Results include phase‑resolved horizontal velocity profiles, Reynolds shear stresses, and TKE computed from resolved velocity fluctuations. They indicate that roughness increases near‑bed turbulence intensity and TKE production during wave crest passage. The bed shear stress exhibits phase dependence, and stress peaks occur slightly after maximum orbital velocities.
Future work will combine experiments with numerical simulations to refine bed shear stress and TKE parameterisations, and extend the analysis to more complex shapes and oyster cluster configurations.
Acknowledgements: this research is conducted within the project entitled REEFCOVERY funded by the Flemish Government VLAIO and supported by The Blue Cluster under project with reference number HBC.2023.0394.
How to cite: Santinelli, G., Stratigaki, V., Shabani, B., and Troch, P.: Turbulence and bed shear stress over oyster-bed roughness, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9918, https://doi.org/10.5194/egusphere-egu26-9918, 2026.
We present a coupled modelling approach that integrates a three-dimensional large-eddy simulation (LES) hydrodynamic model with a Lagrangian agent-based representation of methane bubble dynamics in the water column. The fluid flow is resolved using Oceananigans, a non-hydrostatic, finite-volume ocean model that solves the Boussinesq equations on structured grids. Conceptually influenced by MITgcm, Oceananigans was developed from scratch by the Climate Modelling Alliance as an open-source model using the Julia programming language, and is particularly suited for high-resolution simulations of stratified and buoyancy-driven flows.
Methane bubbles are represented as discrete Lagrangian agents, whose trajectories and state variables evolve in response to the resolved flow field. The bubble dynamics model based on the multicomponent single-bubble model of McGinnis et al. (2006), which describes buoyant ascent and dissolution while accounting for pressure-dependent expansion and the diffusive exchange of methane along with four other dissolved gases. By coupling the bubble model with a three-dimensional LES hydrodynamic model, the framework describes how the resolved velocity field, temperature, and density stratification influence bubble rise and diffusive gas exchange across the bubble–water interface.
This coupled LES–agent-based approach allows simulation of methane transport from bottom sources through the water column in coastal zones and can be used to study methane bubble dynamics and estimate methane fluxes under variable environmental conditions.
How to cite: Sokolov, A., Gustafsson, E., and Stranne, C.: Coupled large-eddy simulation and Lagrangian agent-based modelling of methane bubble dynamics in water column, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11023, https://doi.org/10.5194/egusphere-egu26-11023, 2026.
Monitoring coastal dynamics is essential for sustainable management, disaster risk reduction, and the protection of both ecosystems and human communities. To achieve this, satellite data are essential. However, coastal regions present unique challenges due to their smaller spatial scales, higher variability, and complex features such as estuaries and lagoons. Recent and upcoming satellite missions are advancing coastal monitoring with enhanced spatial and temporal resolutions (e.g., Sentinel-1 and -2, SWOT) and improved radar techniques (e.g., SAR, FFSAR).
The ESA-funded “COASTal Dynamics – COASTDyn” project aims to identify major gaps in scientific knowledge and available satellite-derived data products for coastal regions, and to conduct dedicated research activities to reduce these gaps and improve our understanding of the complex processes occurring at the land-sea interface.
In this presentation, the project’s activities and preliminary results will be shared. During the first phase of COASTDyn, an innovative set of Earth Observation-based methods and products will be developed by leveraging a large set of synergistic observations from space, as well as in-situ measurements, available along the land-ocean boundary. Progress on the development of various products will be presented, including: a coastal Mean Dynamic Topography in the Lofoten region; a novel approach for deriving sea-surface currents from SAR satellite observations based on a fully observation-driven method applied to the Lofoten region; an improved sea-level mapping incorporating SWOT swath data along the European Atlantic façade; and, finally, preliminary tidal research for the Wadden Sea based on a Bayesian inference method that combines SWOT with Sentinel-6 FFSAR observations.
How to cite: Verbrugge, N., Jousset, S., Ballarotta, M., Moiseev, A., Hart-Davis, M., and Gassot, O.: Innovative EO-Based Approaches for Coastal Dynamics from the ESA COASTDyn project , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11691, https://doi.org/10.5194/egusphere-egu26-11691, 2026.
Coastal regions are increasingly at risk of flooding and erosion from sea-level rise, extreme storm events, and anthropogenic activities. Wave runup, which can contribute over 50% to extreme total water levels at the shoreline, is a critical driver of both flooding and morphological change. Consequently, accurate prediction of wave runup is essential for assessing coastal risk and enhancing the resilience of coastal infrastructure, especially during high tides and storm events. However, directly measuring wave runup under storm conditions is challenging due to its highly dynamic nature. To address this, shore-based video systems provide a practical, non-intrusive solution for continuous, wide-view monitoring of shoreline movement.
This research focuses on storm-induced wave runup along the dissipative, gently sloping beach of Villers-sur-Mer in northwest France, integrating a phase-resolving numerical model (SWASH) with high-resolution shore-based video observations. The study assesses the contributions of infragravity waves and sea-swell components to shoreline excursions and total water levels during energetic conditions, providing critical insights for flood risk assessments and coastal resilience strategies. Villers-sur-Mer is characterized by a macrotidal, highly dissipative system, notable for its complex nearshore bathymetry, strong wave-tide interactions, a gentle intertidal slope (~1%), and a substantial tidal range (approximately 3–10 m). Since 2019, a video monitoring system has been collecting 10-minute timestacks at a frequency of 2 Hz, capturing shoreline position and runup variability, providing a robust dataset for model validation under macrotidal conditions. The SWASH model was configured in two-dimensional, non-hydrostatic mode at high spatial resolution, using an October 2019 LiDAR-derived topo-bathymetric surface, forced with conditions from Storm Ciara (February 2020), one of the most energetic storms to impact the French coastline.
Model results show spatial variability in water levels, with relatively weak offshore gradients that intensify toward the inner surf zone where bathymetric slopes and curvature are greater. Along the representative transect, the wave energy spectra reveal a persistent sea–swell peak that diminishes shoreward, reflecting the strong dissipation characteristics of the surf zone. The video timestacks show quasi-periodic shoreline excursions, indicative of low-frequency modulation of runup during energetic conditions; runup maxima align with the arrival of distinct swash fronts. More gently sloping, highly dissipative sections display predominantly infragravity-driven shoreline motion, with smaller excursion amplitudes under comparable offshore forcing.
Overall, the integrated framework provides process-based insights into storm-driven runup on macrotidal, dissipative coasts, supporting improved site-specific hazard mapping, flood risk assessment, and early-warning applications. By resolving the joint roles of infragravity and sea–swell motions in controlling runup and shoreline excursions during severe storms, the study advances process-informed coastal resilience planning and design for dissipative beach environments.
How to cite: Abdulsalam, M. B., Turki, E. I., Solano, C. L., Barcelo, Á. D. G., Lopez, M., Brandle de Motta, J. C., and Reveillon, J.: Integrated Numerical Modeling and Video Observations of Storm-Driven Wave Runup on a Dissipative Macrotidal Beach, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11827, https://doi.org/10.5194/egusphere-egu26-11827, 2026.
Technological progress and increasing human activity are driving higher production levels, resulting in more waste being released into the environment, and in particular in the seas and oceans. The growing need to understand the transport and distribution mechanisms of marine debris has led to the development of various investigation methods, with extensive monitoring (both in situ and through remote sensing), laboratory experiments, and numerical modeling. Through the use of physical equations, real environmental data, and appropriate computational algorithms, numerical modeling in particular can bridge the gap between discrete experimental data and the complexity of the phenomenon, allowing its behavior to be described and predicted under more general conditions. The existing literature has primarily focused on oceanic dispersion models suitable for deep water and offshore investigations, while few studies address the coastal areas, due to the complexity introduced by the highly dynamic, nonlinear nearshore behavior, characterized by wave breaking and currents that difficult to capture with classic grid- or mesh-based numerical methods, such as finite difference methods (FDM), finite volume methods (FVM), and finite element methods (FEM). Recently, there has been growing interest in mesh-free methods, particularly SPH (Smoothed Particle Hydrodynamics). Discretizing the fluid with a set of particles that are free to move with respect to each other, SPH can implicitly and automatically handle a continuously evolving free surface, moving interfaces, large deformations and fragmentations. This method can be used to model several important aspects of the coastal dynamics involved in plastic waste dispersion, such as breaking waves and fluid/structure interaction (FSI), as shown by recent studies on the subject.
We present here our preliminary results in the development and application of an SPH model based on GPUSPH (https://gpusph.org) to simulate the transport, beaching and dispersion of plastic waste in coastal areas. Based on data from laboratory experiments conducted at the University of Messina (Italy), we analyze several SPH formulations to identify those most suitable for the case study. The choice is guided by a compromise between numerical accuracy, consistency with the experimental data, and computational performance. The preferred formulation is then used to investigate some aspects of plastic transport related to waste mass, shape and their interaction with wave motion. We observe a good match between SPH simulations and lab experiments in macroscopic parameters such as the surface velocity profile, wave height and plastic waste arrival times, supporting the choice of this method for the investigation of nearshore plastic transport.
This research work has been funded by the PRIN project “PLAstic Transport due to waves and currents ON Emerged and submerged beaches” (PLATONE) CUP: D53D23004590006.
How to cite: Cristofaro, R., Bilotta, G., Cappello, A., Faraci, C., Ganci, G., Iuppa, C., and Musumeci, R.: Investigating plastic waste transport in coastalareas with Smoothed Particle Hydrodynamics, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12334, https://doi.org/10.5194/egusphere-egu26-12334, 2026.
This study examines the distribution, transport pathways, and potential source regions of floating marine macro-litter (FMML) in Romanian waters of the western Black Sea, combining ship-based observations with Lagrangian backtracking simulations. Visual surveys were conducted during an oceanographic cruise in July 2024 along eight transects spanning nearshore and offshore waters between the Danube Delta and the Northwestern Shelf.
The observations revealed a pronounced spatial contrast in FMML densities across nearshore and offshore domains. Transects located closer to the coast exhibited relatively low concentrations (80–649 items km-2), whereas offshore transects beyond the Northwestern Shelf showed exceptionally high densities, exceeding 9000 items km-2. Offshore counts were dominated by elongated white plastic strips, a debris type not previously reported as prevalent in this sector of the Black Sea.
To explore transport pathways and potential source regions, Lagrangian backtracking simulations were performed using the LOCATE model, a multiscale framework for floating marine litter transport, forced by high-resolution surface currents from the NEMO ocean circulation model. The simulations indicated two distinct transport regimes. Trajectories associated with nearshore observations remained largely confined to the northwestern sector of the basin and were consistent with circulation patterns influenced by major riverine systems, while offshore debris consistently traced back toward the Crimean Peninsula. Complementary analysis of mesoscale circulation using satellite-derived altimetry and the Q parameter identified a persistent cyclonic gyre near 32° E–44° N, acting as a retention zone that favors offshore accumulation of floating debris.
By integrating in situ observations, Lagrangian modeling, and circulation diagnostics, this study documents offshore FMML hotspots in Romanian waters and highlights the role of mesoscale circulation and coastal–offshore connectivity in shaping the distribution of floating debris. These findings underscore the transboundary nature of floating marine litter in the Black Sea and emphasize the need for coordinated, basin-scale management strategies that account for remote source regions and offshore retention processes.
This work received financial support from the TRAP project (EsTRAtegias participativas para la gestión de la contaminación por Plástico del litoral transfronterizo) (EFA147/03), funded by the POCTEFA Program / Interreg VI-A 2021–2027.
How to cite: Castro-Rosero, L. M., Hernandez, I., Liste, M., Alsina, J. M., Espino, M., Pojar, I., and Vasiliu, D.: Nearshore and offshore distribution of floating marine macro-litter in Romanian waters inferred from observations and Lagrangian backtracking, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12515, https://doi.org/10.5194/egusphere-egu26-12515, 2026.
Infragravity gravity (IG) waves are low-frequency surface gravity waves with frequencies below wind-generated short waves, typically between 0.004 and 0.033 Hz, generated primarily as a result of non-linear energy transfer from short waves in the nearshore region. These long-period waves play an important role in the nearshore hydrodynamics, wave run-up and harbour sieches. Detailed numerical simulations using the fully non-linear Boussinesq wave model FUNWAVE-TVD are carried out in this study to understand the cross-shore variation of infragravity energy and the influence of the shoreline on the dissipation and reflection of IG waves. The IG wave energy increases in the shoaling zone and then continues increasing further shoreward and reaches a maximum value near the shoreline. At the shoreline, part of the IG wave is reflected seaward. Infragravity wave energy and reflection characteristics are quantified using spectral analysis of free surface elevations and energy flux estimates. The influence of shoreline configuration on IG wave dynamics is examined by comparing a natural beach profile with an armoured shoreline representing a vertical structure such as a seawall or dike. The presence of a hard coastal structure alters the reflection characteristics and energy distribution when compared to a gently sloping beach.
How to cite: Mary, A. and Sriram, V.: Numerical Investigation on the Influence of Shoreline on Infragravity Waves, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12840, https://doi.org/10.5194/egusphere-egu26-12840, 2026.
Riverine freshwater input is one of the most distinctive processes impacting the coastal ocean, from the physical to the ecosystem level, presenting multiple spatial and temporal variability scales. In situ measurements, satellite imagery, and numerical model solutions are used to study the spatio-temporal distribution of low salinity buoyant plumes off NW Iberia. The in situ observations were carried in the vicinity of the Mondego River estuary (central Portugal) from September 2024 to May 2025 using moored loggers deployed during the fishing operations of a coastal fishing vessel. The measurements from 26 deployments, corresponding to a total of 45 days of valid records of depth, temperature, salinity and turbidity show a strong semi-diurnal signal driven by tidal forcing, superimposed on a seasonal trend. Low salinity values (S < 34.5) were consistently recorded in the coastal zone following the largest precipitation and river discharge event, and the minimum salinity values recorded at low tide after this period were not directly related to the river flow. The observed patterns in high-resolution satellite images support the numerical model solutions and show that the signature of the less saline lens is observable due to suspended particles in the river water and, above all, sediment particles resulting from surface wave breaking, whose distribution serves as a tracer of the currents associated with the plume. The combined analysis of the observations, satellite data and the numerical model solutions showed that the plume's extension offshore and along the coast is primarily linked to the current system in the coastal zone, the local cumulative river discharge and transport of buoyant plumes from neighboring rivers. In particular, the results revealed a significant role of a recirculation cell downstream of Cape Mondego in the vicinity of the river mouth. This cell is associated with the separation of an intermittent equatorward coastal current north of the cape which, at times, also transports low-saline waters from upstream rivers, emphasizing the importance of a regional approach to be able to realistically model the riverine low salinity buoyant plumes off the NW Iberian shelf.
How to cite: Oliveira, P. and Stratoudakis, Y.: Riverine low salinity buoyant plumes off NW Iberia, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14891, https://doi.org/10.5194/egusphere-egu26-14891, 2026.
A field survey program was designed and a numerical hydrodynamic, wave, and sediment transport model was developed to investigate transport of dredged material placed in the nearshore area of an ocean dredged material disposal site (ODMDS) adjacent to the Coos Bay inlet, Oregon. The study focuses on the understanding of coastal hydrodynamic, wave, and sediment transport processes by deploying sediment tracer and simulating the release, movement, and pathways of the tracer under combined influence of wave, current, and wind conditions within and around the immediate vicinity of the inlet.
The measured data and the model results elucidate the magnitude and spatial patterns of ebb and flood currents and capture the tidal flushing of the estuarine system. The sediment mapping feature in the numerical model performs sediment tracer tracking and helps identify sediment transport pathways that corresponds to the specific wave, hydrodynamic, atmospheric, and environmental forcing conditions during the selected simulation period. Sediment tracer tracking by data sampling and model simulation indicates that the released sediment tracer in open ocean area moves towards the inlet entrance at the initial stage of the release. Although a small portion is settled down at the inlet navigation channel, most tracer becomes entrained in the tidal flow, is carried offshore by strong ebb currents, and deposited seaward of the navigation channel. Temporal variations of sediment tracer distributions show that wave and storm conditions drive tracer transport in the open coastal area, whereas sediment pathways are primarily controlled by tidal current inside the Coos Bay and at the inlet entrance. This sediment tracer transport around the inlet system was validated by distal samples collected along the mid-reach of ODMDS.
How to cite: Li, H., Beck, T., Moritz, H., Groth, K., Puckette, T., and Marsh, J.: Tracking sediment tracer in an Eulerian model, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22118, https://doi.org/10.5194/egusphere-egu26-22118, 2026.
Mesozooplankton regulate lower trophic levels through direct grazing and trophic cascades, with the balance varying across environmental gradients. Firstly, we conducted seasonal in-situ experiments in Daya Bay in 2015-2017 to quantify mesozooplankton clearance rates and cascading effects on phytoplankton. Results revealed strong seasonality, with cascades peaking in spring/summer and declining in autumn/winter. Size-selective feeding created divergent impacts: large phytoplankton experienced high grazing mortality but weak cascades, while small phytoplankton showed the reverse pattern. Trophic cascades operated through three mechanisms: offsetting direct grazing losses, restructuring phytoplankton communities via size-dependent effects, and reducing ciliate grazing pressure by 14.4±7.8% (while maintaining ~70% of natural ciliate grazing rates). Community composition was the primary driver: cladoceran dominance elevated feeding rates, whereas high omnivorous copepod abundance intensified cascades on small phytoplankton.
Building on these findings, we leveraged the thermal discharge from Daya Bay Nuclear Power Plant as a natural warming experiment to directly assess temperature effects. Specifically, we established four distinct temperature stations, ranging from the closest to the farthest from the power plant, to capture the temperature gradient and conducted seasonal in-situ mesozooplankton feeding experiments. Results showed that temperature increases simultaneously enhanced mesozooplankton feeding rates and trophic cascades, with disproportionately stronger effects during low-temperature seasons. In cooler conditions, direct grazing dominated, suppressing phytoplankton biomass. Conversely, under warmer conditions, trophic cascades became dominant, promoting small-sized phytoplankton growth. General Additive Model analysis confirmed that cascade variability was highly dependent on temperature, ciliate abundance, and predator-prey feeding interactions.
Our study clarifies how mesozooplankton feeding regulates planktonic communities across temperature gradients and underscores their role in ecosystem stability, providing critical insights for marine ecosystem management under climate change scenarios.
How to cite: Chen, M. and Liu, B.: The variability of trophic cascades on phytoplankton induced by mesozooplankton through in-situ feeding experiments under different temperatures, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2351, https://doi.org/10.5194/egusphere-egu26-2351, 2026.
We investigate the impact of offshore wind farms (OWFs) on the coastal atmosphere and ocean off western Iberia by comparing two five-year (2009–2013) dynamical downscaling simulations performed with the Weather Research and Forecasting (WRF) regional model. One simulation includes a wind farm parameterization (WFP) scheme, while the other does not, enabling a direct assessment of turbine-induced modifications to local wind patterns and ocean circulation associated with upwelling. Winds in this region are typically stronger in summer and predominantly from the north, and upwelling dominates along most of the region in the baseline scenario. Maximum reductions of approximately 12.5% in wind speed at 10 meters, averaged over the five-year period, were identified in the wind farm areas with the highest number of turbines, with wakes extending more than 125 km downwind and oriented southward. Summer exhibited the strongest wind reductions and longest wake extensions. Wind deficits were also evident aloft, with maxima between 100 and 150 m, encompassing the hub height, where the flow directly impacts the rotor. Near-surface wind wakes generate horizontal gradients in wind stress within the wind farm areas, producing zones of surface-water divergence and convergence and driving vertical ocean motions. Turbine-induced upwelling is expected to occur on the offshore side of the farms and downwelling on the onshore side, forming dipoles that can extend over 100 km and are predominantly oriented southward. Five zonal transects crossing the OWFs at different latitudes – approximately perpendicular to the dominant wind-wake direction – provide indications of these dipoles and interactions between dipoles from neighboring farms, forming double dipoles in some cases. Integration along these transects indicates that weakening of upwelling, resulting from the combined effects of Ekman pumping and coastal upwelling, is the most recurrent outcome throughout the year, particularly during summer. This reduction in upwelling is also expected to have an impact in nutrient concentrations and primary productivity in the studied regions. These projected results provide insights into the potential response of the coastal atmosphere–ocean system to wind energy extraction, highlighting the need to consider coupled interactions in OWF planning.
Keywords: Offshore Wind Farms; Western Iberian Margin; Wind Farm Wakes; Upwelling; Weather Research and Forecasting (WRF); Wind Farm Parameterization
How to cite: Fernandes, R., Machado, A., Tomé, R., and Peliz, Á.: Modelling the Impact of Offshore Wind Farms on the Coastal Atmosphere and Ocean off Western Iberia, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-332, https://doi.org/10.5194/egusphere-egu26-332, 2026.
Posters on site: Wed, 6 May, 08:30–10:15 | Hall X5
Malaysia’s coastal waters experience strong monsoonal forcing, with distinct Northeast (NE), Southwest (SW), and Intermonsoon periods that influence hydrodynamics, terrestrial runoff, and atmospheric inputs. Although the sea surface microlayer (SML) plays a critical role in air-sea exchange, it remains poorly characterised in monsoon-driven tropical environments, leaving important gaps in regional biogeochemical understanding. This study investigates the concentrations and enrichment of major surface-active substances (SASs), including surfactants, dissolved monosaccharides (MCHOs), polysaccharides (PCHOs), total dissolved carbohydrates (TDCHOs), and transparent exopolymer particles (TEPs), in coastal waters off Peninsular Malaysia. The SML and underlying water (ULW, 1 m) samples were collected using the glass plate technique during the SW monsoon (August to September 2023; May to July 2024), NE monsoon (November 2023), and Intermonsoon (October 2024), and SAS components were quantified using methylene blue, TPTZ, and Alcian Blue assays. Stations influenced by anthropogenic activity showed clear enrichment of surfactants and carbohydrate species (EF > 1), while TEPs were generally depleted (EF < 1). Strong SML and ULW correlations suggest upward transport from the water column as a dominant source of SASs in the SML. During the NE monsoon, both SML and ULW were fresher than during the SW monsoon, reflecting the influence of rainfall and terrestrial runoff, which contributed to elevated carbohydrate concentrations. Overall, SAS enrichment persisted under moderate wind speeds but weakened under higher wind conditions.
How to cite: Mustaffa, N. I. H.: Monsoon-Driven Variability of Surface-Active Substances and Organic Matter in the Sea Surface Microlayer and Coastal Waters of Malaysia, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1222, https://doi.org/10.5194/egusphere-egu26-1222, 2026.
Shallow, restricted microtidal bays in deltaic environments pose a stringent test for coastal-scale modelling because hydrographic variability is controlled by freshwater discharges routed through channels, wind-driven exchange and sharp bathymetric gradients. The associated non-linear coupling between stratification, residual circulation and wave–current dynamics in shallow exchange corridors can limit predictability and lead to persistent, spatially structured errors in operational coastal simulations.
We assess hydrographic performance in Alfacs Bay (Ebro Delta, NW Mediterranean) using a high-resolution, nested COAWST configuration with two-way ROMS–SWAN coupling. Atmospheric forcing is provided by Spain’s National Meteorological Agency (AEMET). Model output is evaluated against a 2022 CTD dataset from seven fixed stations using rigorous space–time–depth collocation that preserves the vertical structure of temperature–salinity profiles. Performance is quantified using bias, RMSE and correlation, complemented by stratification diagnostics and regime-based analyses contrasting calm conditions with wind-driven events.
Across N = 2397 CTD–model collocations, temperature is reproduced with high fidelity (bias = +0.30 °C, RMSE = 1.32 °C, R = 0.99), indicating that seasonal-to-event-scale thermal variability is well captured. In contrast, salinity exhibits a systematic positive bias and low correlation (bias = +2.24 psu, RMSE = 2.69 psu, R = 0.30), consistent with an overly marine and weakly variable representation of inner-bay hydrography and degraded stratification dynamics. Guided by these error signatures, we conduct sensitivity experiments that vary freshwater discharge magnitude and its distribution across inflow pathways, and quantify the added impact of wave–current coupling on hydrography and exchange-relevant diagnostics during high-energy wind–wave events.
Overall, salinity/stratification emerges as the main skill-limiting component in this restricted shallow bay, motivating a process-oriented evaluation of freshwater routing, mixing and wave–current feedbacks to prioritise improvements in coupled coastal prediction.
Acknowledgements: This work has been funded by the contract 24263-COP-INNO USER 9000: COPERNICUS MARINE NATIONAL COLLABORATION PROGRAMME: EU COASTAL MONITORING DEMONSTRATORS. Lot no 1: FLORETHA: FLOoding and eRosion at the Ebro delta coasT and Harmful Algal bloom forecasting in its inner semi-enclosed bays.
How to cite: Liste, M., Mestres, M., García-León, M., Castrillo, L., López, T., G. Sotillo, M., Fernández, M., and Espino, M.: CTD-based assessment of salinity and stratification in a freshwater-fed microtidal bay using nested ROMS–SWAN simulations: Alfacs Bay (Ebro Delta, NW Mediterranean), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19614, https://doi.org/10.5194/egusphere-egu26-19614, 2026.
Establishment of common vertical datum in ocean models and tide gauges is vital for the model validation and follow up coastal applications of computed sea level and currents. One of challenges is to merge output of global ocean models, such as Copernicus NEMO-based ocean model GLORYS12 that uses a perfect sphere approximation of the Earth, with input of coastal models generally relying on measurements at regional or national tide gauge networks where Mean Sea Level (MSL) approximates local geoid. Coastal ocean waters around Peninsular Malaysia is one example of such a practice, where Malaysia and Singapore are having their own vertical datums generally based on measured MSL but with a few corrections catering for practical engineering.
The research focuses on benchmarking of NEMO global ocean model with tide gauge records around Peninsular Malaysia with a final goal to set regional coastal ocean model satisfying both data sets. In the paper two steps toward the goal are presented: firstly - development of a conversion method between NEMO-computed sea level variables and respective values measured at tide gauges; secondly, analysis of sea level climatology, variability and extremes using both data sets.
How to cite: Tkalich, P., Samsami, F., Qian, C., and Ma, P.: Benchmarking the NEMO Global Ocean Model Using Tide Gauge Records Around Peninsular Malaysia , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3258, https://doi.org/10.5194/egusphere-egu26-3258, 2026.
Eutrophication is a major stressor on Baltic coastal ecosystems, significantly impacting phytoplankton bloom dynamics and biogeochemical variability. Accurate characterization of chlorophyll a concentration is crucial for understanding the timing, intensity, and spatial structure of phytoplankton blooms. However, in the Baltic region, observational data is sparse, and biogeochemical models often underestimate bloom intensity and fail to accurately describe seasonal evolution, particularly along the coast.
In this study, we investigate the impact of chlorophyll-a data assimilation (DA) on the simulation of phytoplankton blooms in the Baltic Sea. Satellite ocean-colour products and in situ observations are assimilated into a coupled physical–biogeochemical model using a Local Singular Evolutive Interpolated Kalman (LSEIK) filter. Both chlorophyll-only and combined SST and chlorophyll assimilation experiments are performed to assess their influence on bloom dynamics across different sub-basins. DA substantially improves the representation of phytoplankton bloom timing and magnitude at the basin scale. Relative to satellite-derived chlorophyll-a, DA reduces RMSD from 1.7 to 1.3~1.4 mg m⁻³ in spring and from 2.2 to to approximately 1.4 mg m⁻³ in summer for the chlorophyll-only and combined SST+chlorophyll assimilation experiments, respectively. Overall, the RMSD are reduced by 33~40% in DA runs over the full simulation period, indicating a significant improvement in the characterization of algal bloom intensity and large-scale spatial consistency. Comparisons with in situ observations shows regionally variable changes in correlation, indicating large differences between in-situ and satellite observations, while consistently showing a reduction in RMSD and an improvement in mean-state representation.
These results demonstrate that LSEIK-based chlorophyll-a data assimilation effectively constrains large-scale phytoplankton bloom dynamics in the Baltic Sea, improving the realism and spatial coherence of simulated chlorophyll fields. The findings highlight both the advantages and limitations of satellite-driven assimilation for representing coastal phytoplankton variability and provide insights for future developments in marine biogeochemical data assimilation.
How to cite: Liu, Y., Ruvalcaba Baroni, I., edman, M., and axell, L.: Chlorophyll-a data assimilation using LSEIK improves coastal bloom representation in the Baltic Sea, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5256, https://doi.org/10.5194/egusphere-egu26-5256, 2026.
The Ebro River — one of the major Mediterranean rivers of the Iberian Peninsula — has undergone substantial hydrological alterations over the past century, driven by natural variability and intensified by anthropogenic interventions in the upstream catchment, including regulated flows and extensive agricultural water extraction. A key manifestation of these changes in the lower river reach is the persistent intrusion of a salt wedge, which under low-flow conditions can extend up to ~30 km inland from the river mouth. This study provides a century-scale assessment of salt-wedge dynamics in the Ebro River, combining historical observations, hydrological records, and numerical modelling from 1916 to 2025. A high-resolution hydrodynamic model was developed to simulate steady-state salt intrusion under a wide range of river discharge scenarios and the micro-tidal forcing characteristic of the river mouth. The model, validated against in-situ salinity and current measurements, accurately reproduces the formation, structure, and upstream migration of the salt wedge, and underscores the strong influence of riverbed bathymetry on penetration length.
Model results reveal a robust inverse relationship between river discharge and salt-wedge intrusion. In a long-term context, the analysis shows that both the frequency and the spatial extent of salt intrusion have increased by roughly 400% over the past century, primarily due to the progressive reduction of annual freshwater inputs. These findings advance understanding of the long-term evolution of estuarine salinization in Mediterranean rivers and highlight the need to integrate historical datasets, field observations, and scenario-based numerical modelling to support adaptive water-resource management and enhance coastal-zone resilience under ongoing climate and anthropogenic pressures.
How to cite: Grifoll, M., Calvillo, B., Peñas-Torramilans, R., Cuthbertson, A., and Berntsen, J.: Long-Term Evolution of Salt-Wedge Intrusion in the Ebro River Under Changing Hydrological Conditions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5299, https://doi.org/10.5194/egusphere-egu26-5299, 2026.
The Korea Hydrographic and Oceanographic Agency (KHOA) operates three Ocean Research Stations (ORSs) in the Yellow Sea and the East China Sea, leading the response to climate change by monitoring and analyzing the marine environment surrounding the Korean Peninsula. Starting with the Ieodo ORS in 2003, followed by Shinan Gageocho in 2009 and Ongjin Socheongcho in 2014, these stations function as interdisciplinary ocean-atmosphere observation platforms and contribute to a wide range of research fields, including marine climate change studies.
In particular, the Ieodo ORS, located southwest of Jeju Island, is a key observation site influenced by the northward-flowing Taiwan Warm Current, the southward Yellow Sea Cold Water, and low-salinity discharge from the Yangtze River. The station is also directly exposed to typhoons approaching the Korean Peninsula. Based on its geographically advantageous location for environmental observation, approximately 15 oceanic and atmospheric variables have been continuously observed at this site for over 20 years.
Key variables, including water temperature, salinity, and various meteorological parameters, are provided at 10-minute intervals following a rigorous two-stage quality control (QC) process. This system integrates automated four-step procedures—range, standard deviation, spike, and stuck-value tests—based on international OOI protocols, supplemented by manual expert verification of oceanographic conditions and maintenance records. High-quality datasets are subsequently registered on global platforms such as OceanSITES, SEANOE, and EMODnet.
The ORS network serves as a cornerstone for multidisciplinary research in physical oceanography, marine biogeochemistry, and atmospheric science. KHOA has utilized these stations to conduct specialized studies on ocean acidification and air-sea interactions in the Yellow and East China Seas. In this presentation, we examine the QC procedures, the status of international data registration, and representative research outcomes derived from the ORS observation network.
How to cite: Kim, H., Jeong, K.-Y., Ham, H., Lee, H.-Y., Gu, B.-H., Seo, G.-H., Lee, K., and Kim, B.-M.: Ocean Research Station (ORS) Network as a Core Platform for Climate Change Monitoring: Data Management and Application Studies, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8531, https://doi.org/10.5194/egusphere-egu26-8531, 2026.
In oceanography—whether physical, biochemical, or modelling—the availability of high-quality data is essential for studying the complex dynamics of marine systems. Today, a wide range of observational platforms is available to meet the growing demand for oceanographic data, including floats, drifters, gliders, moorings, buoys, and other monitoring systems. One of the key challenges lies in the development, deployment, and long-term maintenance of these infrastructures to ensure continuous data availability, as well as in the establishment of efficient data pipelines that allow experts to access information in a unified and straightforward manner.
This work presents the past, present, and future of the buoy infrastructure known as Mambo1, selected as one of the main data acquisition systems operating in the Gulf of Trieste. In particular, the main components of the buoy and its data chain are described. The Gulf of Trieste, located in the northern Adriatic Sea, represents a key site for oceanographic research, as the knowledge gained there forms the basis for understanding the complex regional sea dynamics. Furthermore, the infrastructures deployed in this area are part of the National Civil Protection meteo-marine monitoring network.
The Mambo1 buoy is owned by the National Institute of Oceanography and Applied Geophysics (OGS), based in Trieste. It was developed and deployed in 2000 off Miramare Castle (45°41′54″ N, 13°42′24″ E) and is part of the JERICO R I, as well as the ICOS and DANUBIUS projects. The buoy currently consists of a floating structure housing: (1) the hardware control interface, (2) the photovoltaic power supply, (3) a meteorological station, and (4) the data transmission system. The underwater section hosts several instruments, including: (5) three CTDs positioned at different depths from the surface to the seabed, along with sensors for pCO₂, pH, dissolved oxygen, photosynthetically active radiation (PAR), and turbidity, all acquiring data at hourly intervals.
The core of the data chain is the hardware control interface, which governs the entire system. Fully developed in-house at OGS, both in hardware and software, it acts as the central controller by managing instrument configuration and data acquisition through serial I/O ports, regulating the power supply, and processing and transmitting data in near real time via LTE broadband network. The data are sent to a dedicated cloud environment and subsequently processed and archived by the National Oceanographic Data Centre (NODC) at OGS headquarters. Starting from the raw data, the NODC performs additional steps, including acquisition management, integration with metadata, quality control assessment, and final storage in a database made accessible through the ERDDAP data server.
Planned future developments include the installation of an electronically automated winch to enable water-column profiling, as well as the integration of an Acoustic Doppler Current Profiler and a nutrient sensor.
Thanks to the complete Mambo1 data system and pipeline—from its initial deployment to the present day and with future expansions—a wide range of oceanographic data is freely available through the NODC database. While instrumentation and technology may evolve over time, the underlying concept and structure of the data chain remain consistent.
How to cite: Ferri, L., Brunetti, F., Corbo, A., Gustin, S., Lanzoni, A., Lorenzo, C., Schinaia, F., Mansutti, P., Arena, F., and Bubbi, A.: Mambo1 buoy data system: past, present and future of the Gulf of Trieste observatory, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18539, https://doi.org/10.5194/egusphere-egu26-18539, 2026.
The world’s oceans are vertically stratified into multiple layers based on density, which is a function of temperature and salinity. Fluid mixing occurs when these layers interact with each other and plays a central role in regulating ocean stratification. This mixing process is highly nonlinear in both space and time and is primarily driven by buoyancy. Exploring its detailed dynamics requires numerical models that simulate the combined effects of ocean surface forcing, wind stress, and turbulent mixing, together with in situ observations such as Conductivity–Temperature–Depth (CTD) profiles, moored instruments, and Argo float measurements. These observations and model outputs generate large, high-dimensional spatio-temporal datasets that are challenging to analyse using traditional approaches alone, motivating the use of data-driven and machine learning methods to efficiently extract dominant patterns and predictive information.
In this work, we explore data-driven reduced-order modelling approaches to analyse and predict ocean stratification in the Bay of Bengal using temperature and salinity fields obtained from the Copernicus Marine Environment Monitoring Service (CMEMS). We employ two methods: (i) Dynamic Mode Decomposition (DMD), which approximates the temporal evolution of the system using a linear operator and extracts physically interpretable spatio-temporal modes, and (ii) Neural Latent Dynamic Model (NLDM) based on an encoder–decoder architecture with nonlinear latent-state evolution. The neural model learns a low-dimensional representation of vertical profiles and propagates them forward in time using nonlinear latent dynamics, enabling a flexible approximation of complex temporal behaviour beyond linear assumptions.
The predictive performance of both approaches is evaluated using daily CMEMS temperature and salinity data for the year 2024, with models trained on 360 days and validated by forecasting the subsequent 6 days. Classical Dynamic Mode Decomposition exhibits forecast root-mean-square errors of approximately 1.01 °C for temperature and 0.31 psu for salinity over the 6-day horizon. In contrast, the neural latent dynamics model achieves substantially lower prediction errors, with corresponding RMSEs of 0.0366 °C and 0.0136 psu. This improvement arises from the ability of the neural latent dynamics framework to represent nonlinear temporal evolution in a reduced latent space, which cannot be captured by the linear evolution assumption inherent in classical DMD.
Keywords : Ocean Stratification, DMD, Ocean Vertical Mixing, Neural Latent Dynamic Model
How to cite: Jena, B. K., Sanyal, T., and Pal, N.: Comparison of Dynamic Mode Decomposition and Neural Latent Dynamic Model for Predicting Ocean Stratification in the Bay of Bengal, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16167, https://doi.org/10.5194/egusphere-egu26-16167, 2026.
Typhoon-generated swells pose substantial threats to the coastal environment along the eastern coast of Taiwan. Harbors constructed along this coastline are directly exposed to the Pacific Ocean and vulnerable to swell waves propagating into harbor entrances. These waves can excite long-period harbor oscillations, degrading harbor tranquility and operational safety. Hualien Harbor provides a representative case of an exposed harbor susceptible to long-period swell-induced resonance. In this study, a series of laboratory experiments was conducted in a wave basin to investigate the interaction between typhoon-generated swells and the harbor geometry of Hualien Harbor. A dense array of wave gauges was deployed throughout the harbor to measure spatial water-surface oscillations. To interpret the underlying physics and extend the analysis beyond the instrumented locations, a wave-resolving numerical model based on Boussinesq-type equations was applied to reproduce the experimental configuration. Special consideration was given to the wave-maker configuration to address the limitations imposed by the finite length of the wave generator. Based on the combined experimental–numerical results, the spatial amplification patterns and natural resonance modes of the harbor were examined, and their dependence on incident wave conditions, dispersive effects, and boundary reflections was evaluated. These results demonstrate how the interaction between incoming swell spectra and the intrinsic modal structure of the harbor governs the magnitude and spatial distribution of in-harbor oscillations. The results further reveal that localized amplification zones within the harbor basin act as hotspots for harbor oscillations. The findings thus establish a physical basis for designing wave-dissipating structures and modifying harbor geometry to mitigate long-period resonance in high-energy coastal environments.
How to cite: Su, S.-F., She, C.-H., Chen, I.-A., Wei, C.-H., Tsai, L.-H., and Weng, W.-K.: Harbor resonance under typhoon-generated swells in eastern Taiwan: numerical simulations and laboratory experiments, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7636, https://doi.org/10.5194/egusphere-egu26-7636, 2026.
Posters on site: Wed, 6 May, 10:45–12:30 | Hall X5
The European flat oyster (Ostrea edulis) was once a keystone species in the North Sea but is now functionally extinct offshore due to overharvesting and disease. Restoration efforts aim to reintroduce oysters at sites that combine suitable habitat conditions with hydrodynamic features that support larval retention, as natural recruitment sources are absent. The Frisian Front is a depositional zone recently partially closed to bottom trawling. It lies within the historic distribution range and appears to have suitable habitat conditions, according to existing habitat suitability models. Restoration efforts can only be effective if deployed oyster material remains in place. This study evaluates several sites on the Frisian Front, designated for oyster restoration in terms of larval retention, stability requirements of deployment material and local fine-scale habitat conditions.
Field work indicated that there were distinct differences between two sites, despite their relative proximity. One was relatively muddy, with a median grain size between 129 and 171 µm, a silt content between 17.1 and 31.6% and dominated by heart urchins (Echinocardium cordatum). The other site consisted of much coarser sand (median size range 208-406 µm) and much lower silt percentages of between 0.3 and 11.5 %, as well as lower abundance of macrobenthos species and shell material.
Metocean analyses indicated that both these sites were unsuitable for deployment of e.g. oyster spat on loose shell material as this would be dispersed quickly. A certain amount of weighting of deployment material (cages, gabions) is required.
Using a Lagrangian particle tracking approach coupled to a high-resolution hydrodynamic model, we simulated passive transport of virtual larvae released from both candidate sites during the main spawning period. Larvae were tracked for up to 20 days, reflecting the pelagic larval duration of O. edulis. Results indicate very low local retention and minimal connectivity between sites, with larvae consistently advected eastward. While both sites are located in areas of moderate habitat suitability, dispersal trajectories suggest that larvae may reach zones with higher suitability downstream, including fisheries exclusion areas and wind farm zones. These findings highlight that hydrodynamic retention and habitat quality must be jointly considered in offshore restoration planning. Achieving self-sustaining populations at the Frisian Front will likely require reinforcement strategies until upstream larval sources are established.
Although there is still much unknown about effective offshore restoration of reef-building species, combining research on different essential aspects will give the highest chance of success.
How to cite: Heye, S., Kleissen, F., Bos, O., Perdon, J., Gerritsma, I., Emmanouil, A., and van Duren, L.: Larval Dispersal and micro-siting for restoration of European Flat Oyster (Ostrea edulis) on the Frisian Front, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13134, https://doi.org/10.5194/egusphere-egu26-13134, 2026.
Hybrid two-dimensional (2D)/one-line shoreline models provide a more computationally efficient process for modelling shoreline change over both the micro (<10 years) and meso (10 - 100 years) timescales. An important aspect of this shoreline modelling approach is to ensure that the outputs are mesh independent (i.e., predictions are due to the underlying physics being solved, and not due to mesh resolution), which is achieved through identifying an optimal mesh discretisation for the area of interest. In this paper, we apply the MIKE 21 hybrid 2D/one-line model to examine the influence of mesh discretisation on the simulation of shoreline change in individual cross-shore coastal profiles at equal intervals alongshore, with focus on a sandy coastline along Absecon Island, New Jersey. Our findings suggest that while the optimal mesh discretisation varies based on the nature of the coastal environment under investigation, there are limitations in the applicability of hybrid models to managed shorelines. Based on these outcomes, the recommendation is that researchers would need to have more dynamic modelling capabilities to better discretise coastal environments for modelling shoreline positions, particularly since active coastal management affects model calibration and therefore reliability of model outputs. These results have important implications for optimising mesh generation to facilitate more robust applications of hybrid 2D/one-line shoreline models along sandy coastlines to better inform coastal risk management decisions.
How to cite: Goseine, K. and Seenath, A.: On the importance of nearshore mesh discretisation for modelling the evolution of managed shorelines, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11456, https://doi.org/10.5194/egusphere-egu26-11456, 2026.
AI-based surrogate modelling techniques are increasingly used in geoscience, with notable success in weather and climate forecasting as well as in hydrology and urban water systems. Their application to coastal and regional ocean modelling, however, remains challenging due to high spatial resolution requirements, complex geometries, and strong local dynamics. At the same time, surrogate models offer substantial benefits through fast inference, achieving speed-ups of one to three orders of magnitude compared to numerical simulations, which is particularly valuable for operational coastal forecasting where rapid decision-making and ensemble-based uncertainty quantification are essential. Many existing surrogate approaches rely on grid-like data structures that are often incompatible with the unstructured meshes required in coastal applications, highlighting the need for flexible frameworks that can operate on such data while remaining suitable for integration into operational workflows.
To address this gap, this study compares two surrogate methodologies that have been specifically adapted to the requirements of coastal modelling: Reduced Order Models (ROMs) and Graph Neural Networks (GNNs). While ROMs provide high computational efficiency, they typically treat the simulation outputs used for model training as independent data points and thus neglect the spatial structure of the computational mesh. As a result, important geometric information that is often carefully encoded in unstructured coastal models is not explicitly exploited. In contrast, GNNs offer a more flexible modelling framework that explicitly incorporates the topology of the computational mesh, enabling a more accurate representation of complex geometries and local dynamics.
Both approaches are assessed on two representative coastal domains modeled using MIKE 21 Flow Model FM software. The first is a highly dynamic estuary system influenced by anthropogenic structures, including Hamburg’s port and a complex river bifurcation. The second is the Øresund Strait, a coastal transition zone connecting the North Sea and the Baltic Sea, characterized by strong tidal currents and complex bathymetry. The surrogates are trained on the simulation inputs and outputs of these models and assessed for their forecasting of current velocities and surface elevations across varying lead times. Beyond predictive accuracy, the study examines computational efficiency and implications for real-world applicability.
The results show that both surrogate types can reproduce up to 95% of the numerical model precision, but with substantial differences in computational efficiency. ROMs achieve orders-of-magnitude faster training times, whereas GNNs demonstrate improved robustness in geometrically complex settings. These findings highlight the trade-off between mesh-aware and mesh-unaware surrogate designs and underline the importance for application-specific choices in operational coastal forecasting.
How to cite: Schäfer, F., Petersen, F. H., and Mariegaard, J. S.: Graph Neural Networks versus Reduced-Order Models for Surrogate-Based Coastal Forecasting on Unstructured Meshes, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12542, https://doi.org/10.5194/egusphere-egu26-12542, 2026.
Understanding the morphodynamic behavior of tidal flats is essential for predicting their stability and ecological function under changing coastal conditions. This study focuses on Garolim Bay, a semi-enclosed macrotidal bay located on the west coast of South Korea, characterized by a wide tidal basin with a narrow entrance, forming a pot-shaped coastal geometry with minimal riverine input. The absence of significant terrestrial sediment sources provides an opportunity to isolate marine process-driven morphological evolution.
A fully coupled three-dimensional numerical model was employed to simulate tidal current, wave action, sediment transport, and morphological changes. For model forcing, a combination of global model outputs and local observational data (tidal, currents, wave, and in-situ suspended sediment concentration) was used. Observational datasets were also employed for validation to ensure model reliability. To construct the model topography, a hybrid approach was adopted. Bathymetric survey data were used to define the main tidal channels in both the inner and outer bay. For the extensive tidal flat areas, satellite imagery was employed to extract and integrate isobath lines, enabling the reconstruction of a high-resolution digital elevation model. This approach addressed the limitations of drone-based surveys, which were impractical due to the wide spatial extent of the tidal flats and the large tidal range (~8 m).
The simulation focused on the summer flood season, during which external forcings such as typhoons frequently affect hydrodynamic regimes. Results show that tidal currents dominate the sediment transport regime, while wave-induced shear stress plays a secondary. Morphological changes are spatially heterogeneous due to current convergence zones and limited sediment resupply. These findings suggest that Garolim Bay exhibits dynamic but internally constrained sediment redistribution patterns. These findings contribute to long-term modeling of intertidal evolution and offer valuable insights for assessing the preservation potential of tidal flats, their role as prospective blue carbon resources, and their morphodynamic response to future environmental changes such as sea-level rise.
How to cite: Kim, D. H., Lee, B., Kim, C. H., and Do, J. D.: Numerical Modeling of Tidal Flat Morphodynamics in a Semi-Enclosed Macrotidal Bay: A Case Study of Garolim Bay, Korea, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16013, https://doi.org/10.5194/egusphere-egu26-16013, 2026.
Seagrass is an important component of nature-based shore protection to reduce waves and currents, yet many coastal predictions still assume static vegetation or split growth drivers in separate models. We present a process-based model that integrates three canopy-level drivers in one framework: photosynthetically active radiation (PAR), temperature, and dissolved nutrients such as nitrogen and phosphorus. Algal competition is represented as epiphyte shading that filters canopy light. Model outputs are above- and below-ground biomass, shoot density, and allocation, controlled by a small, interpretable parameter set chosen for identifiability and fast calibration.
Method benchmarking reproduces temperate seasonal envelopes using settings consistent with Carr (2012) for seasonal dynamics and Kenov et al. (2013) for nutrient limitation, and calibrated against the Virginia Coast Reserve Long-Term Ecological Research datasets. Tropical applicability is assessed under Singapore conditions with continuous-flow mesocosms of Cymodoceae rotundata and Halodule uninervis across light and nutrient treatments; temporal trajectories of biomass and tissue nitrogen are compared to model predictions and cross-checked with literature percent cover and density where available.
For coastal-scale application, the module is coupled to Delft3D FM via Python BMI, where seagrass density and canopy traits are mapped to bed roughness and drag, and hydrodynamic fields are linked to biological components at each step. Analyses first defined a baseline seasonal pattern from light and temperature alone, then quantified additional changes when the limiting nutrient and epiphyte shading were active. This contrast yields operational threshold bands and identifies habitat types where control flips from light or temperature to nutrient limitation. The result is a screening-level workflow to test attenuation reliability, prioritise nutrient management versus physical light restoration, and support scenario design for hybrid nature-based solutions in tropical coasts.
How to cite: Tandadjaja, F. G., Tong, X., Huang, S., and Gin, K. Y.-H.: Light, Nutrient, Algae Thresholds For Tropical Seagrass: An Ecohydraulic Growth Model, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3223, https://doi.org/10.5194/egusphere-egu26-3223, 2026.
Estuaries are vital ecosystems with dense populations and developed economies. However, their complex hydrodynamics and intense human activities make it difficult to understand how the properties of the water vary spatiotemporally. As a typical zone of interaction between rivers and the ocean, the Yangtze Estuary suffers from severe hypoxia, and the spring-neap modulation of the properties of water masses remains unclear. Our research reveals significant spring-neap variability of Yangtze Estuary water masses with a distinct vertical bi-layered structure, contradicting traditional views that spring tide mixing enhances bottom DO. This study focuses on analyzing the coupled physical-biogeochemical mechanisms driving such variability, with a particular emphasis on tidal asymmetry and human activities.
Methodologically, we integrate long-term, high-frequency, in situ data (from a seabed cable system), satellite observations, and a high-resolution, coupled hydrodynamic-ecological model (SCHISM-CoSiNE). The model adopts unstructured grids of ≤1 km in key nearshore areas and optimized tidal parameterization in order to accurately capture the high-frequency spring-neap dynamics and biochemistry. Dynamical diagnoses and sensitivity experiments quantify the contributions of tidal asymmetry, advection, and human activities to water mass variations.
The key results demonstrate the distinct spring-neap variability of the water masses in the Yangtze Estuary with vertical structure: the salinity of the upper layer decreases by over 4 psu during spring tides. Reduced upper-layer salinity induces a shoreward pressure gradient that drives deep-ocean, high-salinity water towards the shore, increasing lower-layer salinity by up to 2 psu. Furthermore, satellite data confirm that there are corresponding variations in the concentrations of chlorophyll-a and particulate organic carbon in the sea surface. Interestingly, bottom dissolved oxygen (DO) levels decrease during spring tides, contrasting with traditional expectations. Dynamical diagnoses confirm that tidal current asymmetry (which modulates the ratio of freshwater to seawater) is the driving factor, and similar patterns are observed in the Mississippi River Estuary. Additionally, dams in the watershed alter variability hotspots by reducing sediment flux and causing tidal flat erosion. The coupled model effectively reproduces these characteristics, and improve the simulation accuracy of bottom DO and salinity.
This study advances the modelling of coastal systems by combining hydrology and ecology on a fine scale. Moreover, it establishes a scientific foundation for the ecological management of estuaries and provides guidance on assessing the impact of human activities on these ecosystems.
How to cite: Yan, C.: Response of Bottom Salinity and Dissolved Oxygen to Spring-Neap Tidal Cycles in the Yangtze Estuary: Observations and Coupled Modeling Analysis, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4375, https://doi.org/10.5194/egusphere-egu26-4375, 2026.
Seagrass meadows provide nature-based coastal protection by dissipating wave energy and thereby reducing flooding and coastal erosion. While wave attenuation by seagrass has been widely assessed under pure waves and waves with following currents, the role of opposing currents is less explored, despite its relevance for tidally forced nearshore environments. Here we report 160 flume experiments using an artificial Enhalus acoroides meadow, comprising 32 pure-wave cases, 64 wave with following current cases, and 64 wave with opposing current cases. Following currents generally weakened wave attenuation, whereas opposing currents systematically enhanced it. Relative to pure-wave conditions, wave attenuation under following currents could decrease to approximately 38%, while opposing currents increased attenuation by up to a factor of four. Velocity measurements further show that, for the sparse vegetation used in this study, in-canopy currents are non-negligible: the mean current velocity at the downstream meadow edge differs by less than 20% from that at the upstream edge, indicating efficient shear-layer penetration into the canopy. The current effect on wave attenuation can be explained by the competition between (i) current-induced blade reconfiguration that reduces effective plant height and frontal area (reducing drag), and (ii) current enhanced in-canopy velocities and current modified wave-energy advection that alter the mapping from time-domain dissipation to spatial decay, leading to reduced attenuation for following currents but increased attenuation for opposing currents. These results provide process-based constraints for parameterizing wave dissipation by flexible, sparse vegetation under wave–current coupling in coastal-scale models.
How to cite: Guan, Y. and Qu, J.: Wave Attenuation by Sparse Seagrass Meadows with Non-negligible In-Canopy Flow Under Combined Wave–Current Conditions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4619, https://doi.org/10.5194/egusphere-egu26-4619, 2026.
The summertime upwelling system off the southern Vietnamese coast is a major oceanographic feature of the South China Sea, highly sensitive to climate variability on both regional and larger scales, and strongly influencing the sustainability of the local fishing-ground productivity. This upwelling system is divided into two coastal regions: the Southern Coastal Upwelling (SCU; south of 12.5°N) and the Northern Coastal Upwelling (NCU; north of 12.5°N), and one offshore region: the Offshore Upwelling (OU; east of 110°E). Based on the high-resolution three-dimensional HYCOM ocean reanalysis product, we investigate the characteristics of the upwelling system and identify the controlling factors in each region on the interannual timescale. The generalized Q-vector ω-equation is adopted to reconstruct vertical velocity, providing a direct means to quantify upwelling intensity and evaluate the primary dynamical processes responsible for driving vertical motion. The summertime vertical velocities under climatological conditions in the central areas of the SCU, NCU, and OU are estimated at 0.16 m d-1, −0.08 m d-1, and 0.003 m d-1, respectively, and can increase to 0.32 m d-1, 0.07 m d-1, and 0.08 m d-1 during strong upwelling events. Analysis of vertical velocity component provides a detailed explanation of the primary roles of the key controlling factors and incorporates the interaction between the two coastal currents along the Vietnamese coast, the combined effect of horizontal shear and density gradient in the overall dynamical mechanism of this upwelling system. Moreover, this framework quantifies the relative contributions of physical processes involved in generating vertical velocity in this region.
How to cite: Ngo, M.-H. and Hsin, Y.-C.: Mechanisms of Interannual Changes of the Summertime Upwelling System in Central South China Sea based on Generalized Q-Vector Omega Equation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5438, https://doi.org/10.5194/egusphere-egu26-5438, 2026.
In this work, a new physical approach has been implemented to generate various scenarios of extreme waves by coupling two computational models, Simulating WAve till Shore (SWASH) and DualSPHysics Models, with different computational costs. Both models have been largely used for investigating the hydrodynamics in nearshore and coastal zones. The SWASH model is deterministic wave model based on the nonlinear shallow water equations, with added non-hydrostatic effects is an effective model for propagating waves in extended areas, while the DualSPHysics model is a meshless Lagrangian model based on the smoothed particle hydrodynamics method, developed to study free-surface flows is useful to investigate analysis of the interaction between waves and coastal structures. The SWASH-SPH coupling technique utilizes experimental water surface elevation data as input to SWASH. The SWASH model employs a multi-layer approach to obtain velocity distributions over time, and at the coupling point, the resulting velocity data from SWASH is utilized for the coupling point. Waves in DualSPHysics are generated by a moving boundary (MB), whose displacement over time is reconstructed using velocities provided by SWASH. The numerical coupling of both models has been validated using experimental data, useful to extend its application to more complex systems and/or those not achievable through physical experiments. In addition, this approach opens up interesting prospects for advanced modeling and numerical simulations in a variety of environments, such as dam failure, waves breaking and sediment transport on beaches. The coupled SWASH-SPH model reproduces the propagation and breaking of extreme waves. SWASH captures wave transformation offshore, while SPH effectively resolves the complex dynamics in the breaking zone. Overall, the SWASH-SPH method successfully quantitatively reproduces the expected behavior in these test cases.
Keywords: Extreme Wave, Wave propagation, SWASH Model, DualSPHysics Model.
How to cite: Compaore, A., Abcha, N., Turki, E. I., Matar, R., and Lecoq, N.: Extreme wave propagation by coupling two computational models: SWASH Model and DualSPHysics Model, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9927, https://doi.org/10.5194/egusphere-egu26-9927, 2026.
Design and coastal management are based on site specific wave information. As measurements are scarce and short, modelling is used to produce wave data. Depending on the problem and funding, simple methods are frequently used instead of complicated wave models with space and time varying forcing. This approach is apparently sufficient in open ocean conditions where spatial variations in wave properties are normally limited. The situation is different in nearshore areas of complicated shapes, where wave properties can be highly variable. The use of default settings of wave models means that possible errors remain unknown, and employing data with substantial uncertainties could lead to structural failures or too expensive structures. We study the magnitude of possible errors by comparing the output of simple wave models (such as the stationary/non-stationary fetch-based SPM model or the SWAN model forced with one-point homogenous wind) and the sophisticated multi-nested SWAN wave model forced with ERA5 winds with wave measurements in various nearshore locations in the Gulf of Riga, eastern Baltic Sea. The modelled results are compared with records of different length spanning over more than fifteen years. It is shown that in many locations simple models or models forced with homogenous wind yield good results, while sophisticated models are dependent on site-specific tuning of parameters. Surprisingly, stationary models yield better results in selected locations. The outcomes of our analysis provide several site-specific hints for practical coastal engineering.
How to cite: Männikus, R., Soomere, T., Suursaar, Ü., and Hwa, C.: How do simple wave models perform compared with sophisticated models and measurements in the Gulf of Riga, eastern Baltic Sea?, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13505, https://doi.org/10.5194/egusphere-egu26-13505, 2026.
Posters virtual: Tue, 5 May, 14:00–18:00 | vPoster spot 1a
EGU26-3616 | ECS | Posters virtual | VPS20
Hybrid spectral downscaling and climate-driven variability of multimodal wave systems in the Gulf of PanamaTue, 05 May, 14:30–14:33 (CEST) vPoster spot 1a
The Gulf of Panama is a semi-enclosed tropical basin where coastal processes are driven by a multimodal wave climate with pronounced interannual-to-decadal variability (Vallarino-Castillo, 2026). Offshore wave conditions were characterized at three spectral locations near the Gulf entrance using GLOSWAC-5 spectral data (Portilla-Yandún and Bidlot, 2025), revealing dominant wave systems with distinct directional origins and seasonal variability. A persistent Southern Ocean swell dominates year-round from the south–southwest, while northerly wind-seas associated with the Panama Low-Level Jet prevail during the dry season (December–April). Their opposing directions lead to frequent crossing-sea conditions, particularly along the western Gulf entrance, where partial blocking by the Azuero Peninsula enhances directional spreading. In contrast, more exposed central-eastern locations exhibit consistently multimodal spectra, whereas sheltered eastern areas show reduced northerly wind-sea influence and narrower directional ranges. During the wet season (May–November), additional southerly swell components linked to subtropical trade winds and the Chocó Low-Level Jet reinforce low-frequency energy, while episodic North Pacific swell incursions further increase spectral complexity. Building on these offshore patterns, we analyze how wave systems transform as they propagate across the Gulf’s complex basin geometry.
To resolve coastal wave conditions efficiently, we applied a hybrid spectral downscaling framework across the Gulf. Remote swell was reconstructed using BinWaves (Cagigal et al., 2024), which disaggregates each offshore spectrum into frequency–direction bins and propagates them individually with SWAN, assuming linear wave superposition over the nearshore of the Gulf of Panama, such that nonlinear wave–wave interactions are neglected during propagation. Nearshore spectra are then reassembled using precomputed propagation coefficients that account for coastal geometry. Locally generated seas were reconstructed with HyXSeaSpec, which extracts dominant atmospheric modes via multivariate dimensionality reduction, projects SWAN spectra onto a reduced EOF/PCA space and learns the nonlinear mapping between atmospheric modes and spectral coefficients using radial basis functions (RBFs). During prediction, new wind fields are projected into the reduced space to recover full directional spectra through inverse transforms. The hybrid workflow generates a 3-hourly directional wave spectrum hindcast (1969–2023) that combines remote swell and locally generated wind-sea contributions throughout the basin.
The ongoing nearshore analysis uses the reconstructed spectra to identify dominant variability patterns and coherent wave regimes, assessing how energy is redistributed within the gulf and how nearshore conditions respond to seasonal and interannual atmospheric forcing.
References:
Vallarino-Castillo R, Antolínez JAA, Negro-Valdecantos V, Portilla-Yandún J (2026). “Beyond understanding the role of far-field climate in the Gulf of Panama coastal dynamics: an analysis of long-term and seasonal variability of wave systems”. Climate Dynamics. https://doi.org/10.1007/s00382-025-08007-w
Portilla-Yandún J, Bidlot J-R (2025). “A global ocean spectral wave climate based on ERA-5 data: GLOSWAC-5”. Journal of Geophysical Research: Oceans. https://doi.org/10.1029/2025JC022629
Cagigal, L., Méndez, F.J., Ricondo, A., Gutiérrez-Barceló, D. & Bosserelle, C. (2024). “BinWaves: An additive hybrid method to downscale directional wave spectra to near-shore areas” en Ocean Modelling. 84, 102346.
How to cite: Vallarino-Castillo, R., Bellido, G., Cagigal, L., Negro-Valdecantos, V., Portilla-Yandún, J., Méndez, F., and A. A. Antolínez, J.: Hybrid spectral downscaling and climate-driven variability of multimodal wave systems in the Gulf of Panama, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3616, https://doi.org/10.5194/egusphere-egu26-3616, 2026.
EGU26-8164 | Posters virtual | VPS20
Development of a Fine-Scale (1/648°) Nested Ocean Forecasting Model for the Tunisian ShelfTue, 05 May, 14:33–14:36 (CEST) vPoster spot 1a
The enhanced spatial resolution enables a more realistic simulation of key coastal processes, including tidal dynamics, shelf currents, and nearshore circulation features. Model performance is evaluated against available in situ observations and Copernicus Marine Environment Monitoring Service (CMEMS) model products, demonstrating a substantial improvement in the representation of coastal hydrodynamics compared to lower-resolution configurations.
The developed forecasting modeling framework provides a robust tool for investigating physical processes on the Tunisian shelf and offers a valuable foundation for coastal management, environmental monitoring, and hazard assessment (e.g., storm surges and coastal flooding).
How to cite: Bouzaiene, M. and Menna, M.: Development of a Fine-Scale (1/648°) Nested Ocean Forecasting Model for the Tunisian Shelf, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8164, https://doi.org/10.5194/egusphere-egu26-8164, 2026.
