Orals: Wed, 30 Apr | Room 1.34
We calculate the changes in magnitude and frequency of extreme sea levels along the global coastline by 2100. Our extreme sea level in each location is a combination of sea surface height associated with storm surge and wave (100-year return period, the 95th percentile), high tide (the 95th percentile) and a low probability sea level rise scenario (the 95th percentile). We apply a probabilistic approach with focus on low- probability high- impact events, commonly used for assessments of the economic impact of coastal floods, coastal defence design, and population exposure, among others. We demonstrate that changes in magnitude of extreme sea levels are not uniformed along the global coastline, however, most of locations will experience an increase in magnitude of extreme sea levels in warming climate. By 2030-2040 the present-day 100-year return period for extreme sea levels would be experienced at least once a year in tropical areas. This 100-fold increase in frequency will take place on all global coastlines by 2100.
How to cite: Jevrejeva, S.: Changes in magnitude and frequency of extreme sea levels along the global coastline by 2100, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4092, https://doi.org/10.5194/egusphere-egu25-4092, 2025.
As part of the first international polar year (1882-1883), two scientific bases were established in the southern hemisphere by France and Germany. The French settled at the southern tip of South America seventy km northwest of Cape Horn at Orange Bay and the German expedition two thousand km away in the south Atlantic in the South Georgia Islands (Royal Bay). This contrasts with the effort put in the northern hemisphere, where 12 stations were installed during this first international polar year. The Cape Horn mission was organized by the French Science Academy and 140 men were send to the south to set up the scientific base and to carry out meteorological and magnetic operations over the course of a year. During this period, sea level measurements were carried out using a tide pole at the arrival of the expedition and then a floating tide gauge. The 300 original tidal charts (marigrams) of the floating gauge have not yet been found, but about 15000 half-hourly sea level measurements from the tables of the scientific report have been digitized. We have also digitized the barometric pressure records. The recording was almost continuous from September 12, 1882 to August 31, 1883. This newly recovered dataset is one of the few records of the southern hemisphere's sub-polar regions to cover almost a full year in the 19th century. In particular, this recording enables precise analysis of the tides in this part of the world. In the presentation we will assess the quality of the records and discuss the evolution of the tide in this region.
How to cite: Testut, L., Agnew, D., Woodworth, P., Khan, J., and Yeasmin, N.: Analysis of a newly recovered historical sea level and air pressure dataset in Cap Horn (1882-1883) , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3418, https://doi.org/10.5194/egusphere-egu25-3418, 2025.
Storm surges are causing widespread devastation, directly impacting coastal communities through injuries and fatalities, infrastructure damage, and the displacement of residents. Projections of future storm surges are vital for assessing these risks, especially under climate change that causes both the intensity and frequency of these extreme events to increase. The temporal and spatial resolution of global climate model simulations do not resolve the critical characteristics of the events: storm surge peaks such as daily maximum storm surge occur on the scale of hours, while global climate model simulations are often only available at daily time scales. The coarse resolution data include some information about the daily maximum water levels but does not exactly determine the maximum storm surge peaks. Instead, a range of daily maximum storm surge peaks are realistic under the same coarse conditions.
Hydrodynamic and data-driven models often derive storm surge time series deterministically capturing the average outcome, but do not represent the range of outcomes given coarse-scale predictors. Probabilistic models can address this by generating ensembles of outcomes, each consistent with coarse-scale predictors. For future projections, where no observed storm surge exists for comparison, it can be beneficial to use individual ensemble members to provide more realistic storm surge scenarios.
We implement a multivariate probabilistic model using normalizing flows to simulate time series ensembles of daily maximum storm surges, driven by climate data aggregated to daily means. We train and evaluate the model using ERA5 climate reanalysis data and storm surge time series from the hydrodynamic Global Tide and Surge Model in the time period 1979-2018 across five representative regions worldwide. Our findings indicate that individual ensemble members replicate key statistical features of storm surges more effectively than the ensemble means, given the limited temporal and spatial resolution of the predictors. The multivariate model effectively preserves spatial correlations within each individual ensemble member, making it a spatially realistic realization of storm surge.
Probabilistic storm surge time series conditioned on coarse atmospheric predictors open up new possibilities beyond traditional hydrodynamic modeling. Its performance in settings with limited predictor resolution make it an effective tool for computing storm surge projections consistent with climate model outputs.
How to cite: Treu, S., Tiggeloven, T., Hermans, T. H. J., Couasnon, A., Grumbach, C., Mengel, M., Sauer, I., and Frieler, K.: Probabilistic predictions of storm surge from coarse scale climate data based on normalizing flows, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13240, https://doi.org/10.5194/egusphere-egu25-13240, 2025.
Storm surges pose a significant risk to coastal areas, including the German Bight, where strong northwesterly winds lead to extreme water levels. We present a simple and efficient storm surge model for the German Bight using multiple linear regression with 10 m effective wind as the only predictor. We train and evaluate the model using historical skew surge data from 1959 to 2022, applying regularization techniques to improve prediction accuracy while maintaining the model’s simplicity. The final storm surge model consists of only five terms - the effective wind at various locations with different time lags within the North Sea region and an intercept. A performance assessment based on cross-validation yields a correlation of 0.88, matching the performance of much more complex models despite the simplicity of our approach. The model provides robust predictions for both moderate and extreme storm surges. Moreover, the model’s simplicity makes it particularly suitable for routinely estimating storm surges in climate simulations, even if the climate models provide a very limited number of output variables. Hence, the presented statistical storm surge model provides a valuable tool for evaluating storm surge risks under changing climate conditions. We apply the storm surge model to a multi-model ensemble of CMIP6 global climate simulations to explore the impact of anthropogenic climate change on storm surges in the German Bight. A particular focus is on potential changes in storm surge intensity.
How to cite: Schaffer, L., Boesch, A., Baehr, J., and Kruschke, T.: Development of a wind-based storm surge model for the German Bight and its application, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7995, https://doi.org/10.5194/egusphere-egu25-7995, 2025.
Estuaries and tidal rivers are highly dynamic transitional zones where marine and riverine processes interact, creating complex hydrodynamic environments. These regions are influenced by natural phenomena such as tidal oscillations, storm surges, and river flow, as well as human activities like water management, hydropower operations, flood protection, and navigation. Effective management of these environments relies on understanding and predicting their hydrodynamic behavior, particularly under extreme conditions such as flooding or abrupt water level changes.
This study examines the microtidal Neretva River estuary in Croatia to investigate the interactions between tides, storm surges, and river discharge, and their impacts on water level variability. A modified non-stationary harmonic analysis, based on the NS_Tide model, was developed specifically for microtidal conditions. This model incorporates storm surge and river discharge, improving the predictive accuracy of water levels along the estuary, from tide-dominated downstream sections to discharge-influenced upstream areas. The new version of NS_Tide also allows for a more detailed decomposition of total water levels and tide-surge-river interactions.
The results reveal that river discharge is the primary factor influencing water levels at most stations, while the impact of storm surge decreases upstream. Tide-river interactions were observed throughout the study area, whereas tide-surge interactions had minimal effects. The analysis showed that high-frequency discharge fluctuations caused by hydropower operations amplify the S1 tidal constituent in upstream river sections. These fluctuations also modulate the amplitudes of other tidal constituents in estuarine and tidal river regions, highlighting the complex influence of human activities on tidal dynamics.
The proposed non-stationary harmonic model proved highly effective for the microtidal Neretva River, capturing the complex interactions between tidal and non-tidal forces under various conditions. Its adaptability to local conditions suggests it could also be applied to mesotidal and macrotidal systems, offering a practical tool for managing estuaries and tidal rivers across diverse environments.
How to cite: Krvavica, N., Gržić, M. M., Innocenti, S., and Matte, P.: Interactions of Tides, Storm Surge, and River Flow in the Microtidal Neretva River Estuary, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8431, https://doi.org/10.5194/egusphere-egu25-8431, 2025.
On 17 November 2024, Super Typhoon Man-yi (local name: Pepito) hit the northern part of the Philippines with maximum sustained winds of 195 km/h and lowest central pressure of 920 hPa. Man-yi was the third typhoon to make landfall in the Philippines for that month. Man-yi first passed through the island province of Catanduanes before proceeding north and making landfall at Dipaculao in Aurora province. High-risk storm surge warnings were issued in the country with an estimated height of 2.1 to 3.0 meters at the coast of Aurora for a 48-hour lead time forecast. Although extensive documentation on the damages and affected families was done by government agencies, there were no official storm surge measurements known to be reported. Thus, there is a need to investigate the empirical gap on storm surge levels that occurred in Dipaculao and correlate them with the observed damage to structures. A field survey was conducted at Dipaculao and was able to measure storm surge heights of up to 5.52 meters. A drone was deployed to assess the structural and non-structural damage due to severe wind and storm surge in the area. The field survey observations were supplemented with a numerical simulation of the wind field from Man-yi using the Weather Research and Forecasting (WRF) model. Detailed observations of the damages to a hotel around 20 meters from the coast were documented, and lessons learned from the event are discussed.
How to cite: Valdez, J. J., Gomez, M. E., Abagat, J. G., Agar, J., Leal, E. C., and Luz, A. J.: Rapid Field Survey Damage Assessment of the 2024 Typhoon Man-yi in Aurora, Philippines, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13406, https://doi.org/10.5194/egusphere-egu25-13406, 2025.
This study presents MIOST 2024 (MIOST24), a new global atlas of the sea surface height (SSH) signature of coherent internal tides derived from a single time inversion of 28-year (1993-2020) along-tracks altimetry dataset. The single inversion using a conjugate gradient algorithm, simultaneously resolves the contributions of internal tides and mesoscale eddy variability, unlike other methods which rely on separate mesoscale estimates. Compared to the MIOST 2022 version (MIOST22) by Ubelmann et al., 2022, MIOST24 is based on mode 1 and mode 2 internal tides wavelengths calculated from the vertical stratification profiles of the GLORYS12v1 climatology (1993-2020). MIOST24 atlases are available for the four major tidal components M2, K1, S2, 01. For these waves, the amplitudes and phases of coherent internal tides from MIOST24 are compared with existing atlases MIOST22 and HRET (by Zaron 2019). Additionally, the ability of the different atlases (MIOST24, MIOST22 and HRET) to remove the internal tide signal from altimetry data is evaluated over an independent period from 2021 to 2023.
How to cite: Michel Lionel, T., Loren, C., Clément, U., Simon, B., and Gerald, D.: New global sea surface height internal tide atlas MIOST-IT 24, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17753, https://doi.org/10.5194/egusphere-egu25-17753, 2025.
During the summer of 2002 (a typical summer stratification scenario), internal waves were observed on the South Brazil Bight (SBB), concomitant to Atlantic Central Water uplifting and internal tidal dynamics, with the M2 frequency contributing nearly 10 % of the energy spectrum. Using 1 km horizontal resolution Regional Ocean Modeling System (ROMS) simulations, we examine internal tide generation and interaction within the SBB, identifying significant spatial variability, with offshore energy hotspots influenced by the supercritical topography, topographic features, and the Brazil Current, culminating in 8.70 % of all converted energy generated 5.204 GW in the slope at only 1.64 % of the area. These features extend the residence time of Mode 1 M2 internal tide 5 days longer than the theory predicts, enhancing nonlinear interactions to the level where the wave-wave interactions matter equally as the wave-mean flow interactions, transferring energy to higher frequencies and sustaining baroclinic energy in shallower waters, where stratification breaks down rapidly. Approximately 16.18 % of barotropic-to-baroclinic M2 energy cascades to higher harmonics, while 63.73 % is reflected. Scattered energy supports weakly incoherent internal waves at depths shallower than 200 m, driving a nearly closed energy budget in the model. The Internal Tide enhances up to 21 % of the vertical mixing diffusivity mostly at the bottom and enhances lower temperature advection and the thermal diffusivity coefficient while reducing the vertical potential temperature gradient mostly at the surface and subsurface. Future work will explore the role of wind-driven internal waves and their interactions with the Brazil Current in enhancing mixing, with a focus on topographic conversion hotspots and remote internal wave reflections.
How to cite: Dialectaquiz, A., Dottori, M., and Mazzini, P.: Energy Cascade and Dynamics of Internal Waves on a Subtropical Continental Shelf: Part 1 - Internal Tides, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-93, https://doi.org/10.5194/egusphere-egu25-93, 2025.
The ocean tides are a key driver of a range of Earth system processes. Tidal energy drives vertical mixing with consequences for ocean circulation, climate, and biological production, and the tidal stream transport sediments, pollutants, and other matter through the ocean. Tides have also been proposed to be one component influencing key evolution and extinction events, including initiating the radiation of terrestrial vertebrates. Over the past decade it has become clear that the key controller of tidal energetics on long time scales is tectonics because the size of the ocean basins controls the resonant properties of the tides. Consequently, having accurate reconstructions and paleoDEMs (Digital Elevation Models, i.e., topography) would lead to accurate deep-time tides. Here, we propose that paleoecology can be used to constrain the paleoDEMs, and thereby improve deep-time tidal models results: if a fossil is from a coastal setting, we know where the coastline should be in the reconstructions. We use extensive literature reviews of fossil cnidarian medusae (“jellyfish”) and ichnites (footprints), with focus on those from dinosaurs, to constrain Cambrian and Jurassic paleoDEMs. The early results are encouraging, and in many cases estimates of tidal current speeds can be obtained as well from grainsize estimates of the sediments in the rocks.
How to cite: Green, M., Byrne, H., and Hartley, M.: Squishy in the sloshy: paleoecology as a proxy for tides?, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17513, https://doi.org/10.5194/egusphere-egu25-17513, 2025.
Posters on site: Wed, 30 Apr, 10:45–12:30 | Hall X4
The Permanent Service for Mean Sea Level (PSMSL) is the internationally recognised global sea level data bank for long term sea level change information from tide gauges, responsible for the collection, publication, analysis and interpretation of sea level data. The PSMSL was founded 90 years ago, and today operates from the Liverpool site of the UK’s National Oceanography Centre.
The PSMSL’s main product, a dataset of monthly and annual means from over 2000 locations worldwide aggregated from over 200 suppliers, is a cornerstone in our understanding of changes in sea level over the two centuries. For our highest quality Revised Local Reference (RLR) dataset, we ensure the data can all be referred to a fixed point on land, ensuring a consistent vertical reference frame is used throughout the record. Also, we provide vertical land movement information from permanent GNSS installations near each tide gauge, allowing users to compare our data to measurements from satellites and GNSS-IR data through our GNSS-IR data portal.
Here we present the PSMSL mean sea level dataset, ellipsoidal ties, and GNSS-IR, along with an overview of the dataset's status over the past few years. We also discuss ongoing efforts to improve the dataset and the quality of metadata we supply, and attempts to ensure they meet FAIR data practices (Findable, Accessible, Interoperable and Reusable).
How to cite: Kim, C., Matthews, A., and Bradshaw, E.: The Permanent Service for Mean Sea Level’s (PSMSL) global mean sea level dataset , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11494, https://doi.org/10.5194/egusphere-egu25-11494, 2025.
The coupling between ocean and seismic waves – often referred to as (oceanic) microseism – is a well-established concept since the 1950’s. Ocean and seismic waves are correlating not only on seasonal to annual, but also on daily timescales, in particular during extreme weather events. The most prominent microseism signals have periods below ten seconds and originate from interfering water waves. They are called secondary microseism and can be related to marine storm activity. While some secondary microseism may arrive from far-away coastal regions, a strong contribution also results from nearby coastal wave activity. This paper shows that measurements of microseism from our recently expended seismic network in northern Germany are well suited to monitor wave propagation processes in coastal areas during extreme weather events like the October 2023 storm surge. We utilize three component seismic data from seven stations along the German Baltic Sea coastline and infrasound data from the local array Kühlungsborn (IKUDE) to investigate secondary microseism and atmospheric pressure variations during the storm surge. Spectral investigations over time show distinct local differences in secondary microseism of the Baltic Sea at three different near coastal sites which correlate with half the peak wave period in each respective area. Infrasound measurements reveal additional noise sources, such as nearby wind parks, anthropogenic sources or microbaroms in the North Atlantic and probably the North Sea which are transferred through the atmosphere and absent in seismic data and vice versa. Therefore, sources of our seismic measurements during the October 2023 storm surge are related rather to ocean generated microseism, transferred through the solid Earth than to atmospheric pressure sources. As amplitudes related to secondary microseism of the Baltic Sea decrease with increasing distance of the station to the coast, this allows for an estimation of a sensitivity range along the Baltic Sea coastline. For seismic monitoring of coastal areas, seismic stations are needed to be within 25−30 km distance to the coastline to precisely detect locally generated microseism.
How to cite: Wiesenberg, L., Weidle, C., Krämer, K., Pilger, C., Winter, C., and Meier, T.: Seismic monitoring of the October 2023 storm surge along the coast of the Baltic Sea, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8535, https://doi.org/10.5194/egusphere-egu25-8535, 2025.
A storm surge driven by meteorological phenomena such as low atmospheric pressure and strong winds is an abnormal rise in sea level that can result in disasters, including coastal flooding, damage to coastal structures, ecosystem destruction, and beach deformation. This phenomenon arises from complex interactions between the atmosphere, ocean, and topography, making it essential to reconstruct and analyze past storm surge events to assess their impacts and identify vulnerable areas. Therefore, this study produced storm surge hindcast for the Northwest Pacific region, covering 115-150°E, 20-52°N, from 1979 to 2023. The dataset was generated using pressure and wind fields from ERA5 as external forcing conditions for the Delft3D-FM model. It features a spatial resolution of approximately 40 km in the open sea and 800 m in coastal areas, with a temporal resolution of 1 hour. The topographic data for modeling comprised GEBCO2023 for the open sea and the latest nautical chart data for Korea’s coastal regions. The accuracy of the data was evaluated for short-term events (individual typhoons) and long-term trends (multi-year statistical values), using observational data from 45 tide gauge stations along the Korean coast as the evaluation standard. The root mean squared error (RMSE), correlation coefficient (R), and variance ratio (VR) were employed as evaluation metrics. The analysis of data accuracy for short-term events revealed that it varied depending on topographical features, such as water depth, and the specific characteristics of the typhoon. Long-term trends were evaluated for the annual average, as well as the 99-percentile and maximum values, both representing extreme events. The analysis confirmed that storm surges should be analyzed using the concept of extreme values rather than average values. It was also identified that both short-term events and long-term trends tended to be underestimated by the model compared to the observations. This is likely due to the inability of ERA5, used as the external forcing condition, to accurately simulate extreme weather conditions such as typhoons. So, in the future, it is considered necessary to conduct storm surge hindcast simulations by applying high-resolution meteorological reanalysis data (e.g., JRA-55) for pressure and wind fields as external forcing conditions in the same numerical modeling environment.
How to cite: Yang, J.-A. and Kim, C.: A storm surge hindcast for the Northwest Pacific Ocean from 1979 to 2023, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18912, https://doi.org/10.5194/egusphere-egu25-18912, 2025.
Storm surge barriers provide flood protection to many major coastal cities in estuaries around the world. Maintenance of these assets is critical to ensure they remain reliable and continue to comply with protection standards. To ensure safe working conditions, there are often critical thresholds of environmental conditions, beyond which maintenance work cannot be carried out. However, as storm surge barriers age and with climate change effects such as sea-level rise and changes in storminess, periods when environmental conditions exceed set thresholds will occur more frequently, thus making it more challenging to carrying out the required work in available maintenance windows. Probabilistic models using ensemble forecasts of upcoming water levels determine the likelihood of conditions exceeding the threshold and so can inform on decision making regarding maintenance. Here we evaluate a probabilistic model currently in operational use by Rijkswaterstaat, the Dutch Ministry of Infrastructure and Water Management, to guide maintenance decisions at the Maeslant barrier in the Netherlands. Sixteen years of historic highwater level forecasts from a combination of European Centre for Medium-Range Weather Forecasts and Dutch Continental Shelf Model v5 are used with observations from the Hoek van Holland tide gauge to evaluate and sensitivity test the probabilistic model. Binary classification is used to assess the performance of the probabilistic model. Findings show that the model is conservative with 33.1% of outcomes resulting in a False Alarm. Changing the baseline parameters of critical probability and water level threshold impacts the balance between False Alarm and Miss outcomes. Increasing the critical probability reduces the number of False Alarms but increases the Miss situations, emphasising the trade-off between acceptable risk and time available to carry out maintenance work. This study highlights the delicate balance between model parameter selection and the associated risk with respect to the maintenance of storm surge barriers.
How to cite: Trace-Kleeberg, S., Saman, K., Vos, R., Huibregtse, E., Haigh, I. D., Walraven, M., Zijderveld, A., and Gourvenec, S.: Assessing a probabilistic model for guiding storm surge barrier maintenance , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5748, https://doi.org/10.5194/egusphere-egu25-5748, 2025.
Discharging excess water from regulated water systems in low-lying coastal areas will likely become more difficult due to sea level rise. The functionality of existing discharge sluices will decrease as the discharge window shortens. Additionally, high sea water levels can cause a decrease in the pump capacity of pumping stations, as they would operate far from the optimal operating point. This reduction in discharge capacity may lead to an increase in flood risk in water systems, requiring new or expansions of existing pump-sluice stations.
An accurate representation of high sea water levels due to tides and storm surges is essential to correctly determine the required pump-sluice capacity and operational head for new pump-sluice stations. To asses the effect of storm tides on a water system we are mainly interested in persistent periods of high water levels, their temporal evolution and their distribution. Storm tide models can provide the time series of high sea water levels and the associated statistics required for the pump-sluice design process. Most available models can be sorted in to three types of approaches: long measurement time series, generation of stochastic events, physics-based or stochastic-based long synthetic time series.
In this study different storm tide models were used to assess the functionality of our pump-sluice station design. A comparison shows that the application of different methods leads to very different results in our pump design. Given that all models are plausible, this introduces an important source of uncertainty, which has to be taken into account in the design phase to prevent over- and under-designing.
How to cite: Van Gijzen, L. and Bakker, A.: Sensitivity of pump design to the method to assess the influence of persistent periods of extreme sea water levels, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16303, https://doi.org/10.5194/egusphere-egu25-16303, 2025.
Traditionally, the ocean is treated as an incompressible fluid to simplify wave modeling. However, ocean compressibility—dictated by its density and bulk modulus—significantly impacts wave dynamics, particularly for long-period surface waves (>30 s) and compressional waves within the water column. Similarly, Earth's transition from rigid to elastic behavior under surface loads further influences wave propagation by altering phase speed and waveforms. These effects manifest as arrival time discrepancies and waveform modulation, as observed in tsunami and long-wave dynamics (Allgeyer & Cummins, 2014; Abdolali et al., 2017, 2019).
This study explores the combined effects of ocean compressibility, Earth elasticity, and background density on wave characteristics across a wide frequency range, including infra-gravity (IG), storm surge, tidal waves, and compressional acoustic waves. Building on prior work, a dispersion relationship is derived, accounting for dynamic ocean compression under gravity interacting with a finite, multi-layered elastic Earth. By analyzing phase speed, group velocity, travel times, and pressure profiles, this research advances understanding of wave dynamics and offers a robust framework for improved modeling of tides and storm surges, coastal flooding, tsunamis, and acoustic wave propagation.
Abdolali, A., & Kirby, J. T. (2017), Role of compressibility on tsunami propagation. Journal of Geophysical Research: Oceans, 122, 9780–9794.
Abdolali, A., Kadri, U. & Kirby, J.T. (2019), Effect of Water Compressibility, Sea-floor Elasticity, and Field Gravitational Potential on Tsunami Phase Speed. Scientific Reports, 9, 16874
Allgeyer, S., & Cummins, P. (2014). Numerical tsunami simulation including elastic loading and seawater density stratification. Geophysical Research Letters, 41(7), 2368-2375.
How to cite: Abdolali, A. and Kadri, U.: Impact of Ocean Compressibility, Earth Elasticity, and Background Density on Surface Gravity and Compressional Wave Dynamics, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11260, https://doi.org/10.5194/egusphere-egu25-11260, 2025.
Coastal flooding is a major risk factor for human activities located at the coast. Between the different flooding types that can occur, coastal flooding by overflowing is the one that causes the more devastating effects, because it involves the largest volumes of water. This type of flooding occurs when the mean sea water level exceeds that of coastal defenses. The sea water level at the coast is the result of tide-surge interactions (if the wave setup is neglected), which will also experience the effects of climate change and sea level rise in the coming years.
The numerical modelling is a fundamental tool to understand the phenomena involved, study the coastal hazard and prevent the risk. In this work, whose final aim is to study tide-surge interactions at the global scale, we first focus on the numerical simulation of the dissipative mechanisms, which play a central role in tide propagation.
Indeed, numerical dissipation is added to the physical one in numerical simulations impacting the quality of the results, especially at the coast. In this context, we present a tool for the understanding of physical and numerical dissipative processes and their impacts on the tide propagation. In a barotropic framework, which is suitable to simulate the tide (and later the surge) at the global scale, we solve the non linear shallow water equations using the Uhaina model [1, 2]. It uses an arbitrary high-order discontinuous Galerkin (DG) finite elements method, which provides great parallel scaling properties (HPC). The model works on spherical geometry and includes the bathymetry, the bottom friction, the Coriolis force and the meteorological forcing (wind and atmospherical pressure). Furthermore, the model uses an artificial viscosity mechanism based on the shock capuring theory to stabilize the simulations.
In this work we improve the existing model to account for tidal effects. They include the tide generating potential, the self-attraction and loading term and the internal tide dissipation. As a first step, we show the validation of our global barotropic tidal simulations against the FES2014 model, propagating the M2 constituent of the tide by means of an unstructured mesh discretization of the globe. We then investigate global energetic and dissipative diagnosis, at different DG orders and mesh resolutions, to quantify and localize the spurious energy dissipation induced by the scheme in order to highlight the physical one (generated by bottom friction and internal tide dissipation).
This work is carried out within the framework of the LAGOON - LArge scale Global storm surge simulation Of OceaNs - project (partnership between the French reshearching institutes BRGM, INRIA and UPPA). The project will end up by investigate the impact of future climate on tide and storm surges interactions to produce a sea level database using the Uhaina model.
[1] Filippini, A., et al. (2024). An operational discontinuous galerkin shallow water model for coastal flood assessment. Ocean Modelling, 192:102447.
[2] Arpaia, L., et al. (2022). An efficient covariant frame for the spherical shallow water equations: Well balanced dg approximation and application to tsunami and storm surge. Ocean Modelling, 169:101915
How to cite: Pilorget, V., Filippini, A. G., Arpaia, L., and Ricchiuto, M.: Dissipation processes in global scale tide simulations using a high order discontinuous Galerkin model, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10414, https://doi.org/10.5194/egusphere-egu25-10414, 2025.
Global models of the ocean mass anomaly play an important role in processing space geodetic observations. Most importantly, high-frequency variability of the sea surface height (and the associated surface mass) can degrade altimetric and gravimetric observations, due to their observation characteristics. Therefore, background models are typically used to avoid aliasing of high-frequency signal content. Ocean dynamics is significantly driven by baroclinic dynamics, especially on long-time scales. However, barotropic ocean models have been successfully used to predict high-frequency (~sub-monthly) sea surface dynamics and mass variability (e.g., Carrère and Lyard, 2003; Schindelegger et al., 2018).
Here, we present simulations of non-tidal sea surface height dynamics with the barotropic ocean model TiME (Tidal model forced by ephemerides), which was originally designed to study ocean tides and adapted to simultaneous tidal and non-tidal forcing (Sulzbach et al., 2021). The model possesses several characteristics that are beneficial for global storm surge simulations : (i) a truly global domain ; (ii) the computation of the non-local effect of self-attraction and loading at each time step ; (iii) dissipation by parameterized baroclinic processes, i.e., topographic wave drag ; (iv) simultaneous forcing by the Tide-Generating potential as well as atmospheric pressure and wind stress. The model's versatility allows us to study the influence of the above-mentioned features on the accuracy of the prediction of non-tidal ocean mass variability. Among all considered effects, the influence of (ii) is especially pronounced, as it is sensitive to the spatial extent of the ocean mass anomaly, which can change significantly in time and space for non-tidal processes.
Multiple years of sea surface height data were computed and transformed to Stokes coefficients. Comparison of the results with geodetic observations (e.g., tide gauge data) shows consistent validation and significant improvements when considering tidal/non-tidal interactions, self-attraction and loading, and optimized mechanical energy dissipation by topographic wave drag.
How to cite: Sulzbach, R., Nocet-Binois, M., Hart-Davis, M., Lemoine, J.-M., and Gegout, P.: Global Prediction of non-tidal ocean mass variability induced by atmospheric forcing with a barotropic ocean tide model, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19526, https://doi.org/10.5194/egusphere-egu25-19526, 2025.
We have conducted absolute gravity (AG) measurements over several austral summer seasons at the Finnish Antarctic base Aboa, located in western Dronning Maud Land. The most recent measurements were made in January–February 2024. Aboa is situated on the slope of Basen nunatak, approximately 470 m above sea level, 20 km from the grounding line of the ice shelf, and 100 km from the open sea. Individual AG measurement campaigns lasted from 24 hours to two weeks, with optimal conditions for measurements - stable, laboratory-level environment and low microseismic noise.
The AG measurements revealed clear signals of ocean tidal loading, with effects reaching several microgals. To identify the most accurate representation of ocean tidal dynamics at the site, we calculated theoretical tidal loading using multiple ocean tide models, including both global and regional solutions. Due to the limited duration of the measurement campaigns, our analysis is restricted to diurnal and semidiurnal tidal components. By comparing the calculated tidal loading with the AG residuals, we aim to assess the performance of different models and refine our understanding of tidal dynamics at Aboa. Preliminary results highlight significant discrepancies between models and observations.
Tidal modeling in Antarctic regions presents unique challenges, including limited observations, uncertain sub-ice topography, and complex grounding line dynamics. Transitional zones, where the ice shelf's stiffness dampens the effects of water column changes, as well as density differences at the ice shelf base and surface, further complicate accurate tidal loading modeling.
Identifying the most accurate tidal model is important for improving the interpretation of gravity and other geodetic data, like GNSS time series, and isolating other geophysical signals, such as ice mass changes and related solid Earth deformations.
How to cite: Raja-Halli, A., Mäkinen, J., Nordman, M., and Näränen, J.: Evaluating ocean tide models using absolute gravity measurements at Aboa, Dronning Maud Land, Antarctica, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19712, https://doi.org/10.5194/egusphere-egu25-19712, 2025.
Tide-topography interactions are key drivers of tidal dynamics in the Cape Verde and Senegalo-Mauritania Upwelling regions. Three-dimensional internal tide (IT) simulations identify the Cape Verde Area (CVA) as the primary IT source in the Eastern Boundary Upwelling region off Northwestern Africa, generating approximately 1.87 GW of M2 IT from barotropic tides, with nearly 48% dissipating locally. The West Barlavento Islands serve as a critical energy source, characterized by outward-propagating nonlinear internal waves from the São Nicolau Strait. The distribution and geometry of Islands largely shape a partially standing wave within the Cape Verde Sea. Along the continental margins, distinct topographic features produce contrasting IT dynamics north and south of Dakar. Approximately 9 % (85.8 MW) of the remaining CVA energy propagates eastward into the Cape Verde Plateau (CVP), with 22.3 MW radiating into the North Dakar Area (NDA). Canyon-Seamount systems along the NDA slope contribute 75.4 MW, significantly enhancing onshore energy flux and dissipation over the NDA shelf. In the South Dakar Area (SDA), energy generated over the steeper continental slope radiates offshore by approximately 25% (16.6 MW) into the CVP deep basin, where it interacts with westward propagating IT from the CVA. Onshore shoaling IT with high potential energy flourishes on the SDA shelf. Seasonal stratification significantly influences the IT dynamics with elevated wave energy over the continental slope during winter. Wave-induced turbulent mixing plays a vital role in supporting ecosystems across the Cape Verde and Senegalo-Mauritania Upwelling regions.
How to cite: Huang, H., Brandt, P., Greatbatch, R., and Chen, X.: Three-Dimensional Numerical Simulations of Internal Tides in the Cape Verde and Senegalo-Mauritanian Upwelling Regions, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2080, https://doi.org/10.5194/egusphere-egu25-2080, 2025.
Volume Transport (VT) throughout various sections of South China Sea (SCS) is an important ocean characteristic, defining net flux of water masses, that may also involve heat, salt, as well as admixture transport of dissolved nutrients, suspended sediments and anthropogenic substances. Due to large scale of predominant coupled ocean/atmosphere climate phenomena (e.g., monsoon, ENSO, POD, IOD), variability of VT in the SCS basin is considered commonly at seasonal and/or interannual scales, using monthly or annual resolutions. This approach is justified for large VT rates of Luzon and Karimata Straits, both defining SCS throughflow (SCSTF) having long residence time. In contrast, Malacca and Singapore Straits (MSS) VT contribute just a small fraction of SCSFT, and additionally subjected to similar order local phenomena at daily or even hourly scales. At these scales the VT contribution also is in par with predominant astronomic tide in MSS, thus opening avenue for combination of the two otherwise independent phenomena. To develop the approach further, ocean model NEMO is run at mesoscale resolution for the past period 1990-2024, driven by global NEMO (ECMWF) model at the lateral boundaries and ERA atmospheric forcing at the ocean surface. Even though the research focuses on Singapore Strait, Malacca Strait is included due to dominant regional and local phenomena affecting both water bodies. In order to elucidate variability of submesoscale VT at different cross-sections of MSS, computed daily currents and sea levels are analysed in par with atmospheric forces with the goal to obtain trend, variability and extremes of VT in MSS at daily-to-interannual resolutions. New phenomenon (coined Singapore Strait Reflux, or simply Reflux) is discovered computationally and using data analysis – which is a temporal reversal of VT in Singapore Strait against dominant east-to-west direction. The Reflux episodes lasting from days to weeks may occur any time of a year due to coincidence and interplay of different scale phenomena, affecting MSS from north (Indian Ocean via Andaman Sea), from south (Riau Islands) and from the east (Anambas Archipelago in SCS). The research focuses on understanding of Reflux genesis and forecasting capabilities.
This project is funded by the Research, Innovation and Enterprise 2025 Coastal Protection and Flood Management Research Programme of Singapore. The authors also thank Low K.S., Sasmal K. for their support in the idea discussions.
How to cite: Tkalich, P., Wang, Z., and Ma, P.: Submesoscale variability of volume transport in Malacca and Singapore Straits, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2982, https://doi.org/10.5194/egusphere-egu25-2982, 2025.
