Orals: Mon, 28 Apr | Room L3
The focus of this study is the North Adriatic dense Water (NAddW), which forms in the Adriatic Sea during extreme winter cooling under hurricane-strength bora winds. NAddW plays a critical role in driving the thermohaline circulation, ventilating the deep layers, and influencing the biogeochemical properties of the Adriatic. Modeling the properties of this water mass at the climate scale presents significant challenges due to the complex coastal geomorphology of the Adriatic basin, which is inadequately represented by existing climate models. To address these challenges, the Adriatic Sea and Coast (AdriSC) kilometre-scale atmosphere-ocean climate model was used. This model consists of the Weather Research and Forecasting (WRF) model, with resolution of up to 3 km, and the Regional Ocean Modelling System (ROMS), with resolution of up to 1 km.
The 1-km results of a 31-year AdriSC simulation (1987–2017) were used to analyze the main phases of NAddW dynamics: generation, spreading, and accumulation. Regarding generation, NAddW densities are higher on the shallow northern Adriatic shelf compared to the deeper Kvarner Bay, driven by a median bottom temperature difference of 2°C. Notably, about one-third of the dense water is generated within the Kvarner Bay. In terms of spreading, NAddW mass transport peaks between February and May across most of the Adriatic, except along the western side of the Otranto Strait. Analyses of accumulation sites revealed that the bottom layer of the Kvarner Bay renews annually, whereas renewal occurs every 1–3 years in the Jabuka Pit and every 5–10 years in the deep Southern Adriatic Pit. Lastly, NAddW cascading and accumulation is more pronounced during basin-wide high-salinity conditions driven by circulation changes in the northern Ionian Sea. This three-decade kilometre-scale assessment provides a long-term overview of the Adriatic bottom thermohaline properties, aligning well with existing literature, which predominantly relies on observational studies.
How to cite: Pranić, P., Denamiel, C., and Vilibić, I.: A multi-decadal assessment of Adriatic dense water dynamics at kilometer-scale, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-703, https://doi.org/10.5194/egusphere-egu25-703, 2025.
The Arctic Ocean is predicted to freshen by 30-50% by 2100, with coastal areas receiving significant freshwater from melting glaciers and permafrost. This influx of freshwater, along with increased sediment and carbon inputs, is altering the water chemistry along Greenland’s coasts, potentially impacting food webs. In this study, we examine how sediment-rich, glacial meltwater affects the microbial food web in a high Arctic fjord. We differentiate the effects of freshening alone (using Milli-Q water) from those combined with land-derived compounds (glacial meltwater). Seawater was enriched with 13C-HCO3- and diluted with 16% freshwater using either glacial meltwater or Milli-Q water. We monitored the response of natural microbial producers to both treatments over 14 days by measuring bacterial and algal biomass and production, as well as phospholipid-derived fatty acids (PLFAs) and their δ13C signature. Our results indicate that glacial runoff enriches the marine environment with silicon, and likely nitrogen and carbon, that significantly influence microbial production. Specifically, glacial runoff and a modest 16% freshening boost bacterial production and biomass, but not algal (primary) production. Overall, our study demonstrates that glacial runoff increases bacterial coastal production, potentially impacting the entire ecosystem and highlighting the significant influence of terrigenous freshwater inputs on coastal environments.
How to cite: Puts, I. C., Mostovaya, A., Henson, H., allais, L., Thyrring, J., and Holding, J.: Effects of glacial meltwater on the coastal microbial food web: an experiment, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-887, https://doi.org/10.5194/egusphere-egu25-887, 2025.
The 2024 Atlantic hurricane season was active with 5 landfalling hurricanes in the USA: Beryl, Debby, Francine, and major hurricanes Helene and Milton. In the framework of the National Oceanographic Partnership Program “Hurricane Coastal Impacts” project, we forecasted the wave conditions, water levels, flooding, beach and dune erosion, and infra-structural impacts on building and bridges due to the combination of rainfall-induced flooding, surge, waves and tides for all these hurricanes. To this end, we developed and implemented an operational system of coupled numerical models such as SFINCS - which is used innovatively as a surge model and as an overland flood model -, a new fast wave model Hurrywave, the morphodynamical model Xbeach and the damage model FIAT, all developed at Deltares. The models are driven by operational US Navy COAMPS-TC and NOAA GFS forecasts.
The presentation will show the model forecast results, validated against in-situ and remote-sensed observations obtained by project partners. The presentation will demonstrate the relative importance of typo-bathy (vertical) accuracy and the presence of vegetation.
The system also predicts the uncertainty bands in the forecasts and their evolution over time as the hurricane nears landfall. The system is transferrable to other data-rich and data-poor coasts, such as Mozambique of which an example will be shown.
The information that the system provides gives insight to coastal authorities to make decision on anticipatory actions and emergency response. The results of this work are of interest to geomorphological scientists, DRR experts and coastal authorities.
How to cite: Van Dongeren, A., De Goede, R., Van Ormondt, M., Athanasiou, P., and Quataert, E.: Forecasting hurricane impacts on US coasts, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2869, https://doi.org/10.5194/egusphere-egu25-2869, 2025.
The Arctic Ocean is experiencing rapid changes driven by climate change, with decreasing sea ice and glacial meltwater altering biogeochemical conditions. These transformations are expected to enhance primary productivity, but the availability of nitrogen—a key nutrient often limiting growth—remains a critical factor. While dinitrogen (N₂) fixation, mediated by diazotrophs, is well-studied in tropical and subtropical oceans, its role in Arctic waters has only recently gained attention. This study addresses gaps in our understanding of N₂ fixation rates, diazotrophic communities, and their environmental drivers in Arctic coastal waters, focusing on fjords and seas influenced by glacial meltwater.
Using isotope labeling, genetic analyses, and biogeochemical profiling, we observed N₂ fixation rates ranging from 0.16 to 2.71 nmol N L⁻¹ d⁻¹, substantially higher than those reported in many oceanic regions. UCYN-A dominated the diazotrophic community. Our findings revealed peak N₂ fixation rates co-occurring with maximum chlorophyll a concentrations and primary production rates near the Vaigat Strait, a region strongly influenced by glacier meltwater. We propose that glacial melting and nutrient influx in the Vaigat Strait enhanced primary productivity, creating a niche for diazotrophs to thrive, with the potential to sustain and extend such blooms.
These results highlight the previously underappreciated significance of N₂ fixation in Arctic coastal waters and its potential response to ongoing climate-driven changes, including the melting of polar ice. By shedding light on the physical and biogeochemical processes shaping nitrogen availability and primary productivity in Greenland’s fjords and coastal seas, this study contributes to understanding the region’s evolving ecosystem dynamics.
How to cite: Schlangen, I., Leon-Palmero, E., Moser, A., Xu, P., Laursen, E., and Löscher, C. R.: Nitrogen Fixation in Arctic Coastal Waters (Qeqertarsuaq, West Greenland): Influence of Glacial Melt on Diazotrophs, Nutrient Availability, and Seasonal Blooms, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5854, https://doi.org/10.5194/egusphere-egu25-5854, 2025.
Tidal models are employed in various applications, including the prediction of coastal hazards and environmental impact assessments. This study presents an innovative approach to assimilating high-resolution bathymetric data and calibrating a two-dimensional tidal model. The bathymetric data with a resolution of few tens of centimeters allows for the identification of bottom features, particularly sand dunes. The orientation of sedimentary structures, such as sand dunes, reveals the direction of the residual current. The acquired data is integrated into a tidal model for the Saint-Marcouf region, a microtidal area in the English Channel, known for its sand dunes aligned in varying directions. Following this integration, the Telemac2D model is calibrated using parameters such as bottom friction in different spatial zones and turbulent viscosity. The 3DVar data assimilation algorithm is employed to incorporate the observed residual current direction and calibrate the model. This process is accomplished by coupling the ADAO (a data assimilation and optimization module) with Telemac2D. The data assimilation begins with a twin experiment in the initial phase, utilizing synthetic data of the spatial distribution of the residual current direction. This study will demonstrate the benefits of using high-resolution bathymetric data to obtain information from sedimentary structures, to enhance the performance of hydrodynamic models through data assimilation.
How to cite: Sebastian, A., Thiebot, J., Gregoire, G., and Poizot, E.: Integrating High-Resolution Bathymetric Data for Enhanced Calibration of Tidal Models: A Case Study of the Saint-Marcouf Region, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6324, https://doi.org/10.5194/egusphere-egu25-6324, 2025.
The decline of summer sea ice in the Arctic Ocean is one of the most pronounced indicators of climate change. Reduced sea ice extent influences sea-air gas exchange. The Arctic Ocean is important in the global carbon cycle as it currently contributes 5% to 14% of global oceanic carbon uptake. Understanding how sea ice melt impacts the ocean's ability to act as a carbon sink is therefore crucial. In this study, we focus on Young Sound-Tyrolerfjord in Northeast Greenland to examine the interactions between the atmosphere, sea ice, and ocean during the transition from melt onset to melt pond drainage. High-frequency measurements of partial pressure of CO2 (pCO2) and seawater physical properties were taken 2.5 m below the sea ice. Our results reveal that pCO2 in the seawater were undersaturated (252-355 μatm) compared to the atmosphere (401 μatm), suggesting that the seawater has the potential to take up atmospheric CO2 as the sea ice breaks up. The undersaturation in pCO2 was attributed to the mixing of under-ice seawater with low pCO2 meltwater from snow and sea ice. Additionally, the drainage of meltwater from surface melt ponds, which had been in contact with the atmosphere, into the under-ice seawater caused small but clear fluctuations in pCO2. This represents a connection between the atmosphere and under-ice seawater through meter-thick sea ice during the summer thaw. Our study demonstrates that snow and sea ice melt reduce pCO2 in under-ice seawater, enhancing its potential for atmospheric CO2 uptake during sea ice breakup.
How to cite: Verdugo, J., Ruiz-Castillo, E., Rysgaard, S., Boone, W., Papakyriakou, T., Geilfus, N.-X., and Sørensen, L. L.: Snow and sea ice melt preset pCO2 undersaturation in Arctic waters, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7527, https://doi.org/10.5194/egusphere-egu25-7527, 2025.
The Mar Menor is the largest hypersaline coastal lagoon in Europe, located in the semi-desertic south-east of the Iberian peninsula. This lagoon provides a variety of ecosystem services and resources to the community but, although it has been traditionally considered oligotrophic, in recent decades it has suffered drastic changes and degradation caused by human activities, including agriculture, mining and tourism. In the early 1990s, the lagoon began to receive high inputs of nutrients and organic matter due to changes in agricultural practices in the watershed. Due to the complexity, heterogeneity, and particular homeostatic mechanism of the system, eutrophication symptoms were not evident until the summer of 2015 and early 2016. Although the system recovered quickly after the first eutrophication crisis, several hypoxic events have happened since (in 2019 and 2021) causing massive death of fishes and moluscs.
In order to better understand and predict the functioning of the Mar Menor, and to provide the necessary tools for risk management, a comprehensive modelling effort has been launched in the framework of the BELICH project. This project, funded by the Framework of Priority Actions for the Recovery of the Mar Menor (MAPMM), aims to both enhance our understanding of the physical and biological processes occuring in the lagoon and to provide short term forecasts to support decission making under extreme events.
The modelling system consists in three modules to represent hydrodynamical, biogeochmical and land hydrology processes. The hydrodynamical module is based on the Symphonie model and uses a very high resolution configuration with curvilinear coordinates to simulate the evolution of circulation, temperature, salinity and sea level. This module feeds ECO3M-S, a biogeochemical model of intermediate complexity which includes several types of phytoplankton with flexible stoichiometry, several groups of zooplankton and bacteria. Finally, the inland waters contribution in terms surface and underground water and nutrient supply is simulated with the WaterpyBal and HEC-HMS models.
After a careful calibration and validation procedure, this system is being used to characterize the evolution of the lagoon under mean conditions and during extreme events potentially leading to ecological crises. Also, the system is being run in a pre-operational mode to produce 3-days forecasts and to produce key indicators that can support stakeholder actions. In the presentation, the main results of the system will be presented and its potential usefulness for decission support will be discused.
How to cite: Jordà, G., Loyola, E., Flores, L., Duhaut, T., Lemieux, B., Marsaleix, P., Estournel, C., Ulses, C., Álvarez, E., and Vallina, S.: Hydrodynamical and biogeochemical modelling of the highly vulnerable Mar Menor coastal lagoon, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8132, https://doi.org/10.5194/egusphere-egu25-8132, 2025.
The topo-bathymetry conditions in the coastal areas lead to nonlinear wave transformations and inhomogeneous wave fields that can not be readily described by offshore wave spectra. These nonlinear wave transformations also pose limitations on phase-averaged modelling approaches that are often used for offshore wave forecasting. For example, wave diffractions around islands and coastal structures can not be sufficiently represented with spectra wave models. Phase-resolving models are required for a more realistic representation of the nonlinear wave transformations in complex coastal topo-bathymetry conditions. However, this endeavour often requires increased computational cost compared to the phase-averaging modelling approach. If a certain area of interest is at the focus, for example, a harbour or an especially vulnerable beach, then a site-specific machine learning (ML) algorithm can be used to develop an offshore-to-coast wave correlation that enables fast coastal wave predictions after the nonlinear wave transformations. As the in-situ data are often scarce, the phase-resolving models can be used to represent the nonlinear coastal waves and produce a large set of synthetic data to train the machine learning algorithms. A trained machine learning model using the phase-resolving numerical data can then predict coastal waves given any offshore condition. The offshore conditions themselves can also be predicted with a machine-learning algorithm based on the hindcast data. In this study, a coastal site in Norway is set at the focus. The hindcast data from the open-access database NORA3 provided by the Norwegian Meteorological Institute are used as inputs for numerical simulations of various sea states. With these inputs, the nonlinear wave transformations are represented with the phase-resolving models within the open-source hydrodynamic framework REEF3D. The simulated post-transformation coastal waves are used to train a feedforward neural network (FNN). The trained algorithm can then give near-instant predictions on the coastal wave properties with any given offshore condition. The offshore hindcast time histories in NORA3 are also used to train a long-term short-term memory (LSTM) ML model to predict future events in 3 months. With the predicted offshore waves using NORA3-LSTM, the FNN algorithm trained with REEF3D simulation data can provide coastal wave forecasting for future events. The hybrid approach of phase-resolving models and machine learning utilizing the NORA3-LSTM-REEF3D-FNN combination demonstrates the possibility of fast nonlinear post-transformation coastal wave forecast at key coastal sites characterized by complex topo-bathymetry conditions.
How to cite: Wang, W. W., Christakos, K., and Bihs, H.: Nonlinear coastal wave prediction with a hybrid approach using phase-resolving models and machine learning, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9071, https://doi.org/10.5194/egusphere-egu25-9071, 2025.
This study examines the projected changes in wave heights under the RCP8.5 climate scenario in the Northeast Atlantic (NEA) and along the west coast of Ireland, with a specific focus on the wave climate in Galway Bay. An analogue method was employed to generate surrogate data to downscale wind data from MPI-ESM, using high-resolution ERA5 data as a reference. The surrogate wind data were used to drive the WAM-SWAN model setup for simulating waves in the NEA. This statistical approach provided computationally efficient and reliable wind inputs for wave modelling while effectively capturing the temporal and spatial variability of present and future wind patterns.
Results from the SWAN model simulations reveal distinct spatial and seasonal variability in wave heights, with an intensification of wave activity in the northwest and reductions in the southern and eastern regions of the NEA. While mean significant wave heights are projected to decrease around Ireland, regional variability highlights the complex interactions between large-scale wind patterns and localized wave dynamics. Seasonal analyses indicate significant increases in wave heights during winter and summer, with the largest decreases observed in spring. Localized responses at buoy sites M3 and M4 underscore the spatial heterogeneity of future wave climate changes, with M3 experiencing more energetic conditions and M4 showing increased calm states.
To assess the impacts of waves on coastal processes near Galway Bay, 1D surf zone model was developed. The model was driven by wave conditions derived from SWAN. The primary goal of the 1D model is to study future wave height changes under different sea level rise scenarios. By integrating insights from present conditions with predictions for the future, this study aims to provide valuable information to support decision-making for both short- and long-term coastal management.
How to cite: Kalayil Uthaman, A., Dabrowski, T., McCarthy, G., and Düsterhus, A.: Future Wave Climate and Coastal Impacts: Projections for the Northeast Atlantic and the Galway Bay., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9156, https://doi.org/10.5194/egusphere-egu25-9156, 2025.
Ocean mixing plays a critical role in distributing heat and biogeochemical tracers, yet its representation in ocean circulation models remains fraught with challenges. Especially in coastal domains - where topographic interactions, tidal currents, and nearshore processes put models under extreme tests - diapycnal mixing is poorly constrained and highly sensitive to parameter choices, with spurious effects from advection numerics further complicating results. In this study, we explore the benefits of introducing argon saturation as an additional tracer to circulation models, leveraging its oversaturation state as a diagnostic indicator for diabatic/diapycnal mixing. The approach sucessfully ranks the impact of horizontal resolution against numerical effects associated with the choice of advection schemes in a suite of regional model setups in the North Atlantic off Mauritania. By providing a quantitative method to compare diffusivities in model configurations, our framework may help to develop more robust coastal models.
How to cite: Dietze, H. and Löptien, U.: Diagnosing Effective Mixing in Ocean Models, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9288, https://doi.org/10.5194/egusphere-egu25-9288, 2025.
The west Greenland shelf is a dynamic marine environment influenced by various physicochemical and biological processes. We captured a high-resolution, large-scale snapshot of various water column parameters across the west Greenland shelf and Davis Strait between 64°N and 71°N during July 2021. This study provides an overview of the main factors affecting the distribution of macronutrients (NOx = nitrate + nitrite, silicate, phosphate), carbonate system parameters (alkalinity (AT), dissolved inorganic carbon (CT)), and dissolved trace elements (dV, dFe, dMn, dCo, dNi, dCu, dCd, and dPb) during late summer. The key drivers include major ocean currents, melting sea ice, and terrestrial freshwater runoff, each uniquely contributing to the cycling and spatial distribution of chemical constituents.
Major ocean currents, such as the southward-moving Baffin Island Current (BIC) and the northward-moving West Greenland Current (WGC), shape the chemical composition of shelf waters by introducing water masses with distinct chemical signatures. The northward-moving West Greenland Shelf Water (WGSW) was characterized as warm (2.68°C), fresh (33.57), and highly productive, with overall low nutrient concentrations. In contrast, the southward-moving Arctic water (AW) was cold (0.38°C) and fresh (33.48), with high nutrient contents due to lower biological activity. The inflow of Pacific-origin waters through the Canadian Archipelago (CAA) to Baffin Bay was responsible for elevated dFe, dMn, dCo, dNi, and dCu concentrations.
The progressive melting and retreat of sea ice altered both the biological productivity and the chemical composition of surface waters in southern Baffin Bay. The east-to-west direction of sea ice retreat created a nutrient gradient, with low nutrient levels in the highly productive shelf waters to the east and high nutrient levels in areas with prolonged ice cover to the west. This process also affected the carbonate system, leading to changes in pH and aragonite saturation states, which are critical for the health of marine organisms. Furthermore, we observed sea ice meltwater as a source of dFe, dCo, dNi, dCu, and dCd to Baffin Bay surface waters. This additional source of bioactive trace elements could maintain and prolong ice-edge blooms.
Terrestrial freshwater runoff from the Greenland Ice Sheet (GIS), particularly in Disko Bay and at the mouth of the Nassuttooq Fjord, replenished macronutrients in the photic zone, stimulating primary production (PP) and creating significant CO2 sinks. However, in areas along the coastline where PP was limited by low nutrient concentrations, surface waters became more susceptible to acidification via input of poorly buffered glacial freshwater.
This work provides a summarized overview of the complex interplay between the chemical composition of the west Greenland shelf and major ocean currents, melting sea ice, and terrestrial freshwater runoff from the GIS. Understanding these key drivers is essential for forecasting future changes of the marine chemistry and biology of the west Greenland shelf, especially in the context of ongoing climate change within this high-latitude region.
How to cite: Schmidt, C. E., Zimmermann, T., Koziorowska-Makuch, K., Pröfrock, D., and Thomas, H.: Chemical Distribution Patterns across the west Greenland Shelf: The Roles of Ocean Currents, Sea Ice Melt, and Freshwater Runoff, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10679, https://doi.org/10.5194/egusphere-egu25-10679, 2025.
Sediments accumulating in Greenlandic fjords, situated between the ice sheet and the ocean, offer an excellent opportunity for investigating the environmental response to past climate variability and associated organic carbon sequestration processes.
Our study focuses on a multiproxy approach of an almost undisturbed sedimentary record from Narsaq Sound in southern Greenland. A ~30-cm long multicore was collected on top of a ~11-m long gravity core during the MSM111 expedition in September 2022. Radiocarbon dating indicates a maximum age of approximately 12,000 years and a relatively constant sedimentation rate of ~1 m/kyr.
A suite of whole-core analytical techniques was applied, including magnetic susceptibility measurements, X-ray fluorescence, and computer tomography scanning. Sediment samples were taken at intervals of 5–10 cm from the gravity core and at 1 cm intervals from the multicore. These samples were analyzed for total organic carbon, total nitrogen, stable isotopes of organic carbon and nitrogen, biomarkers (e.g., IP25), and organic carbon lability. Additionally, the elemental composition and dissolved organic carbon content of sediment pore-waters were assessed.
Preliminary results show that sedimentological features such as IRD and bioturbation, as well as the elemental composition of the Narsaq record, reveal major changes related to the position of nearby glaciers and main climatic changes during the Holocene. Moreover, we found that the rather unusual element Niobium, derived from the surrounding drainage area, appears as a promising indicator of terrigenous sediment supply and past environmental change. Besides a clear change from predominantly terrestrial to more marine organic carbon during the transition from deglaciation to the thermal maximum era, the organic carbon is predominantly marine in origin during the entire Holocene.
Our first results show that the investigated sediment cores from southern Greenland provide an excellent sedimentological and geochemical record reflecting past glacial activity and the impact of large scale climatic variability on local environmental changes since the last deglaciation.
How to cite: Faust, J. C., Zhang, Y., de Vernal, A., Janßen, A., Mukherjee, S., von Dobeneck, T., Jäger, N., Jackson, R., Smeaton, C., Detlef, H., Seidenkrantz, M.-S., Andresen, C., Müller, J., Pereira, R., Titschack, J., and Kucera, M.: Fjord sediments in southern Greenland reveal Holocene glacial activity and organic carbon sequestration dynamics, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11442, https://doi.org/10.5194/egusphere-egu25-11442, 2025.
Communities globally are experiencing an increase in high tide flood (HTF) frequency. The present-day impact of HTF for communities is expansive and recurrent, ranging from disrupted activities for infrastructure, inundated stormwater and wastewater systems, and increased public health hazards. Accurate estimates of the probability density functions (PDFs), especially for extreme water levels, are essential for quantifying risks of coastal flooding. In this work, we decompose still water levels measured at 148 tide gauge stations along the United States’ coasts and evaluate the characteristics of the nontidal residual (NTR) distributions. We compare the distribution of high-pass filtered water levels (hourly anomalies) to PDFs of a first-order autoregressive (AR1) process resulting in a Gaussian (normal) distribution and a non-Gaussian (skewed and heavy tailed) ‘Stochastically Generated Skewed’ (SGS) distribution that includes correlated additive and multiplicative noise (CAM noise). We find that the overall error computed between the PDFs and the observed anomalies is reduced at most stations when using the non-Gaussian PDF compared to the AR1 for both the bulk of the distribution and extreme values. We also show that the non-Gaussian SGS distribution is more robust at capturing extreme values in the case of sparse observations, compared to other distributions (kernel density) and extreme value analysis methods (i.e., Generalized Extreme Value and Generalized Pareto Distribution). Our non-Gaussian PDF allows us to diagnose how the shape of the distribution may evolve with climate change. Findings from this work will be implemented in the National Oceanic and Atmospheric Administration’s HTF monthly predictions and used to evaluate changes in forecast skill. This work has relevance for high tide flooding forecasts along the coast and inundation mitigation strategies, as well as estimating PDFs for other physical variables that exhibit heavy-tailed skewed distributions.
How to cite: Hovenga, P., Newman, M., Albers, J., Dusek, G., Sweet, W., Xu, T., Callahan, J., and Shin, S.-I.: Assessing the Characteristics of Nontidal Residual Water Level Distributions for High Tide Flooding Predictions and Projections, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13607, https://doi.org/10.5194/egusphere-egu25-13607, 2025.
This study investigates the potential of glacial flour (fine-grained debris) as a nutrient source. Weathered glacial debris is a key source of essential macro- and micronutrients (N, P, Si and Fe) to subglacial environments and downstream aquatic systems – including freshwater lakes, rivers, and fjords – via glacial runoff. To further understand nutrient cycling in these environments, we conducted a two-year incubation experiment using glacial sediments collected from a glacial outlet near Ilulissat, Greenland. The experiment examined the distribution of nutrients between dissolved phases in pore water, overlying water, and particulate forms bound to sediment surfaces. After incubation, 200 µM Si, 0.7 µM NH₄ and 0.1 µM P were measured in the pore water, showing that saturated subglacial sediments with long rock:water contact times are a source of available dissolved nutrients, despite the absence of freshwater influx. We also assessed the impact of sediment crushing on nutrient release. A 10-minute, high-energy crush and subsequent extraction with ultra-pure water led to a 9-fold increase in Fe, a 47-fold increase in Si and a more than 600 times increase in P in solution. These findings underscore the importance of glacial sediments as a source of Si, P, N and Fe to subglacial ecosystems.
How to cite: Köhler, K., Gill Olivas, B., Skidmore, M., Anesio, A., and Tranter, M.: Glacial flour: Investigating the nutrient potential of Greenland's subglacial sediments, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15336, https://doi.org/10.5194/egusphere-egu25-15336, 2025.
Coupled hydrodynamic models are widely used to predict storm surges and the extent of inundation along coastal regions for improved coastal management and vulnerability assessment. Land use and land cover (LULC) are important in storm surges and related coastal inundation as they impact the water flow velocity. The interaction between storm surges and land use and land cover (LULC) distribution along the coast is essential in assessing the extent of coastal inundation and substantially affects coastal resilience and vulnerability. In the present study, the LULC distribution along the coast has been incorporated in a coupled hydrodynamic model (ADCIRC+SWAN) to assess the impact of the super cyclonic storm Amphan, which devastated the Sundarbans area of the West Bengal coast. Significant changes in the extent of coastal inundation have been noticed by considering land cover changes. In addition to land cover changes, numerical experiments have been conducted by including climate change projections to enhance the cyclonic wind velocity by 7%, which is in line with IPCC reports. Analysis indicates that changing LULC and increased wind intensity significantly contribute to a 30% increase in coastal flooding. The research shows the necessity for efficient land management and conservation initiatives to improve coastal resilience in climate shifts.
How to cite: Vyshnavi, Y. and Satyanarayana, A.: Impact of Land cover changes on a Tropical Cyclone-Induced Storm surge and Extent of Inundation over the east coast of India using a Coupled Hydrodynamic Model, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15964, https://doi.org/10.5194/egusphere-egu25-15964, 2025.
The rapidly melting Arctic glaciers deliver substantial amounts of allochthonous material to the coastal ocean, altering the environment in which biogeochemical processes are taking place. Perturbed aquatic carbon cycling is a particularly troubling outcome of the intensified glacial runoff, with increasing heterotrophy and outgassing of CO2 among the chief concerns. As the key factors influencing the activity of heterotrophic microbes, the quantity and quality of Arctic coastal organic carbon warrant closer examination. To address the relevant aspects, we investigated the molecular composition of dissolved organic matter (DOM) in the glacial rivers and surface coastal waters of the high Arctic fjord (Young Sound, NE Greenland), where glacial runoff contributes to low primary productivity and increasing heterotrophy. Using ultra-high performance liquid chromatography quadrupole time-of-flight mass spectrometry with electrospray ionization (UHPLC-ESI-qTOF-MS), we conducted a non-targeted analysis of solid-phase extracted DOM. We expected molecular signatures of DOM to differ substantially between the two investigated rivers (Tyroler and Zackenberg River), which contrast in length, glacial water source, and drainage basin characteristics. While unique compounds were indeed observed in each river, considerable overlap in molecular DOM signatures was also detected, and a large proportion of aliphatic formulas was found at each site. Comparisons between riverine, river plume, and the outer fjord samples indicated a rapid loss of the riverine signature, likely due to the combined effects of dilution and swift biological consumption of the glacially derived DOM in the inner fjord. Although further research is needed to better understand the mechanisms and ecosystem implications of carbon utilization in high Arctic fjords, our study offers useful insights into the molecular signatures and fates of glacially derived carbon in these systems.
How to cite: Mostovaya, A., Dyrholm Thomsen, L., Glasius, M., and Holding, J.: Molecular signatures of dissolved organic matter in the surface waters of a glacially influenced Arctic fjord (Young Sound, NE Greenland), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16441, https://doi.org/10.5194/egusphere-egu25-16441, 2025.
Upwelling events along the northern shelf edge of the Great Barrier Reef (GBR) are key drivers of ecosystem health and resilience. Understanding the timing, frequency, and drivers of these upwelling events are critical for predicting ecosystem responses to climate change and improving marine management best practices. This study utilises a 12 year dataset from a coupled hydrodynamical-optical-biogeochemical ocean model (eReefs, 4 km resolution) to examine the spatial and temporal variability of upwelling events along the far northern GBR. We focus on the seasonal and interannual variability of upwelling, its relationship to surface chlorophyll concentrations, and the physical processes driving these events. We find that upwelling events are most likely to reach the surface during the Australian summer when the mixed layer is shallower and conditions are conducive to vertical mixing. Significant interannual variability appears to be linked to broader atmospheric-oceanic drivers, such as the El Niño Southern Oscillation. At the shorter time scale, we show that monsoonal wind bursts strongly influence the strength and frequency of upwelling events, with an additional modulation by the spring-neap tidal cycle.
How to cite: Maggiorano, A., Langlais, C., Mongin, M., and Choukroun, S.: Drivers of upwelling events and biological responses in the far Northern Great Barrier Reef region., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18071, https://doi.org/10.5194/egusphere-egu25-18071, 2025.
Digital Twins of the Ocean aim to make information on the state of the ocean readily and interactively available to scientists as well as citizens, policy makers and other stakeholders. Many practical applications require – in particular – information on coastal regions. However, typical digital twins do not provide sufficient detail near the coast, because the model resolution is too coarse and these models lack processes that become relevant in shallow areas, e.g., sediment transport. We bridge this gap between the data provided by Digital Twins of the Ocean and the information needed for coastal applications by creating a Digital Twin of the Coast. The digital twin presented in this talk is a framework for regional downscaling of data from existing large-scale digital twins in combination with in-situ observations. Our Digital Twin of the Coast is based on a numerical coastal ocean model with refined mesh resolution along the coastline and in estuaries. This high resolution, which is further enhanced by subgrid technology, allows the fine tidal channels as well as coastal structures like dams and operational flood barriers to be represented in the model. The hydrodynamic model is coupled with a spectral wave model and includes transports of different sediment classes. We have implemented the digital twin for the Wadden Sea located in the south-eastern North Sea on the European continental shelf. The Wadden Sea is the world’s largest tidal flat system, stretching along the coasts of the Netherlands, Germany and Denmark. To protect its unique ecosystem and great biodiversity, the Wadden Sea has been declared a UNESCO World Heritage Site. The dense network of tide gauges in the Wadden Sea allows a reliable calibration of our numerical model. Our Digital Twin of the Coast is the first public database of consistent high-resolution data for the trilateral Wadden Sea. Thanks to the fast and intuitive web interface of our digital twin, the model data provided enable a wide range of coastal applications and support sustainable management. Applications currently implemented with our digital twin include ecological habitat calculator, sediment management, cable route planning and marine renewable energy.
How to cite: Reinert, M., Lepper, R., and Kösters, F.: Coastal Digital Twin of the World’s Largest Tidal Flat System, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19359, https://doi.org/10.5194/egusphere-egu25-19359, 2025.
Suspended particulate matter (SPM) is a key component of coastal ecosystems, influencing light availability, primary production, and nutrient transport. This study investigates the driving mechanisms behind the seasonal and interannual variability of SPM concentrations measured at two long-term monitoring stations in the Sylt-Rømø Bight, a sandy tidally dominated basin in the Wadden Sea. Combining Sylt Roads long-term observations from 2000–2019 and numerical simulations with the coastal hydrodynamic model FESOM-C with its Lagrangian particle tracking module, we analyse the interplay of wind and tidal forcing, and biological processes in shaping SPM dynamics.
Preliminary analysis of the observational dataset reveals a pronounced seasonal cycle, with a peak in winter ~30 mg/l and a sharp decline in summer ~6.5 mg/l across both stations. These variations are associated with stronger wind events in winter and higher biological activity (reflected by chlorophyll-a concentrations) during spring and summer, indicative of phytoplankton-driven flocculation processes. The data further highlight distinct patterns: the shallower station exhibits an almost immediate response to wind events within 24 h, while at the deeper station, SPM reaches peak concentrations with a delay of ~120 h, consistent with the influence of tidally induced transport in addition to sustained wind-driven mixing. Complementary results from Lagrangian modelling effectively capture these delayed responses at deeper stations and further illustrate the tide-driven transport pathways of resuspended material within the basin.
The findings of this ongoing work provide new insights into coastal physical-biological coupling and the the relative roles of the considered processes in driving SPM variability in tidally dominated systems.
How to cite: Konyssova, G., Sidorenko, V., Rubinetti, S., Androsov, A., Wiltshire, K. H., and van Beusekom, J.: Observational and Modeling Study of Driving Mechanisms Behind SPM Variability in a Tidal System, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19586, https://doi.org/10.5194/egusphere-egu25-19586, 2025.
Between October and November 2023, the Isonzo/Soča River catchment area experienced exceptionally intense rainfall. The strong precipitations acting on the hydrographic basin at the end of October and beginning of November led to exceptional increases in the Isonzo/Soča runoff into the Gulf of Trieste (GoT) (October 27 and November 3). It was observed that in the days before a precipitation event, a southerly wind with a strength of more than 3 m/s almost always affected the area. Concurrently, rising sea levels and coastal flooding were observed. The event is of particular significance as it was also accompanied by strong coastal storm and waves that caused severe damage to the coast.
The aim of this study is to investigate how the exceptional Isonzo outflow, together with the wind patterns associated with the meteorological event, influenced the ocean currents in the surrounding coastal region. To this end, the mechanisms and processes regulating the interaction between river discharges and ocean currents in the Gulf of Trieste were analysed through an integrated analysis combining hydrometric, meteorological and current data.
The prevailing winds in the GoT come from the north-eastern (Bora wind) and southern sectors (Sirocco and Libeccio winds). During Bora events, the usual cyclonic circulation is accentuated and the surface currents normally leave the GoT, while during strong southerly wind events the circulation becomes anticyclonic and the surface currents enter the GoT. In the case with a significant river outflow in combination with southerly winds the circulation is anticyclonic in the central part of the gulf and cyclonic in the northern part.
HFR sea surface current data confirmed that wind-induced Ekman transport appears to dominate the surface current dynamics in the GoT. Nevertheless, exceptionally intense outflows from the Isonzo, triggered by heavy precipitation and accompanied by southerly winds, can overlay the effects of wind-driven transport, leading to the dominance of river-induced circulation patterns in the GoT.
How to cite: Lombardo, D., Flora, S., Giordano, F., Ingrassia, E., Menna, M., Querin, S., and Ursella, L.: Influence of wind stress and the Isonzo/Soča River outflow on surface currents in the Gulf of Trieste, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19656, https://doi.org/10.5194/egusphere-egu25-19656, 2025.
Posters on site: Mon, 28 Apr, 14:00–15:45 | Hall X4
The Amazon River Plume (ARP) is a dynamic feature of the Amazon Shelf (AS), shaped by a combination of natural forces: density-driven currents, tides, and wind variability. To better understand its movement and modulation, we combined the robust Eulerian modelling (ROMS) and the effective Lagrangean framework (Opendrift) in a series of numerical experiments to examine how main forces determine the plume's structure and transport.
The ARP originates from the Amazon River’s immense discharge, forming a buoyant plume that spreads towards the open ocean. Without other influences, the ARP drifts northeast, following the river mouth's orientation. When tidal forces are introduced, the oscillatory motions enhance cross-shelf variability, pushing the plume further into the ocean. Tidal mixing, linked to the resonance of the M2 tidal harmonic, spreads the plume northwards, reaching nearly 2ºN. However, the freshest waters remain confined to the shallow AS, held in place by tidal effects.
Wind shear, though expected to drive more effective advection, mainly shifts parts of the plume northwest along the mid-shelf, adding coastal variability. Yet, in shallower areas, tidal forces dominate, maintaining their role as the primary control. While wind shear influences the plume’s shape, it is not the key driver of its northward movement.
The primary force modulating the ARP appears to be density-driven currents, generated by salinity and temperature gradients. When acting alone, these currents push the plume decisively into the Northern Hemisphere, reaching beyond 3ºN on the mid-shelf. At the shelf break, where the ocean deepens and the coastline's influence diminishes, the plume’s freshwater can spread further offshore.
When all forces act together—winds, tides, and currents—a complex balance emerges. Tides anchor the ARP to the shelf, preventing the freshest waters (salinity < 30) from escaping the AS. At the same time, currents and wind shear drive the plume northwest, extending its reach to around 4ºN.
This balance of forces highlights the dynamic nature of the Amazon River Plume. In an equatorial region where geostrophic balance is minimal, the vast discharge of the Amazon is shaped by regional forces, defining the behavior of one of the world’s largest river-ocean systems.
How to cite: Nascimento, R., Dottori, M., and Dialectaquiz, A.: Modulation of Amazon River Plume: numerical studies, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-582, https://doi.org/10.5194/egusphere-egu25-582, 2025.
The coastal ocean circulation is primarily driven by the surface currents observed due to winds and buoyancy forcing at different temporal and spatial scales. Studying these coastal ocean processes in precise requires a system that can depict the ocean currents with higher temporal and spatial resolutions. In this regard, observations from a pair of long-range HFRs, operational at the Tamil Nadu coast have been considered from (2010-2021) to understand the structure and temporal variations of East India Coastal currents (EICC) during the Post-monsoon (Oct-Nov-Dec) season. Robust comparison has been performed in two stages: first, the HFR datasets are compared with the Drifting Buoys datasets, and second, the same are compared with the satellite-derived surface currents. In both cases, the comparison of the HFR surface currents fields with other datasets depicts a higher correlation (> 0.84) and lower errors (< 0.15 ms-1) for both the zonal and meridional components. The lateral displacement of EICC-jet with time (meandering) is defined using a new coordinate frame (known as Jet-coordinate frame) firmly aligned with EICC without impacting the key variables (core-width, core intensity, core-speed, and surface transport). In the Jet coordinate frame (JCF), core-speed (CS) has a median value of (~0.6 m.s-1) over 1500 m isobath depicting a narrower and more intense core as compared to cartesian coordinate system (CCF). Meandering accounts for ~52% of eddy kinetic energy (EKE) computed in the fixed cartesian frame. As the EICC menders onshore during (Oct), shelf temperature and along-stream velocity varies linearly with jet movement and make the thermal gradient stronger whereas during (Nov-Dec) the shelf gets cooler by (~1.45 °C) with a significant increase of along-flow wind stress (~0.015 N/m2). Temperature and velocity fluctuations at 70 (100 m) isobath are predominantly influenced by wind (EICC onshore meander), with the strongest response when downwelling favorable winds and EICC meandering acts constructively.
Keywords: Tamil-Nadu, High-Frequency Radar, Jet-Coordinate, Meandering, East India Coastal Currents (EICC)
How to cite: Kumar, A. and Mandal, S.: On the Sub-mesoscale and Mesoscale variability of the Coastal Currents along the western Bay of Bengal (BoB), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-632, https://doi.org/10.5194/egusphere-egu25-632, 2025.
The Luzon Strait serves as an entrance of the seawater from the Pacific Ocean to the South China Sea (SCS). When the oligotrophic Kuroshio intrusion into the Luzon Strait encounters with the sea surface chlorophyll-a (SChl-a) discharged from the river estuary in the northern Luzon Island, this patch of SChl-a may be transported by the Kuroshio water from the coastal region westward to the northern SCS. During the strong 2015–2016 El Niño event, the Kuroshio intruded into the SCS through the Luzon Strait on 25 and 26 December 2015. Simultaneously, a patch of SChl-a was directed from the northern coast of Luzon Island to the northern SCS along the rotational trajectory of a series of oceanic mesoscale eddies, ultimately resulting in its diffusion. However, measurements from geostrophic currents from satellite altimeter data cannot accurately depict the current fields near the coasts, where the targeted SChl-a patch generated, due to the shallow topography of the Babuyan Channel and complicated Babuyan Islands acting as barriers. The Maximum Cross-Correlation (MCC) method is thereby applied to address this issue by capturing the moving pattern of the target SChl-a patch from the concurrent sea surface temperature (SST) from satellite observations (MODIS-Aqua Level 3) and analysis data (GHRSST Level 4), as well as SChl-a images from satellite observations (MODIS-Aqua Level 3) and merged datasets (OC-CCI and GlobColour). This study investigated the average magnitude of MCC-derived westward current vectors in the Babuyan Channel (18.25°N–18.75°N, 121°E–122°E) after the Kuroshio intrusion occurred in a looping path, Vwest, based on daily GHRSST data (0.01°×0.01°). The results reveal that Vwest reached 18.84 cm s−1 during December 2015, which is 57.1% and 14.3% faster than other winters in November 2012 (a neutral year, Vwest=11.99 cm s−1) and during November 2022, La Niña event (Vwest=16.48 cm s−1), respectively. Consequently, the stronger Kuroshio intrusion increases the westward currents in the Babuyan Channel and may further influence the ecosystem in the SCS, which are modulated by various phases of El Niño–Southern Oscillation (ENSO).
How to cite: Tseng, Y.-H. and Ho, C.-R.: Chlorophyll-a along the northern coastal of Luzon Island affected by the Kuroshio in 2015–2016 winter, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3963, https://doi.org/10.5194/egusphere-egu25-3963, 2025.
Coastal regions are areas of great socioeconomic and ecological value. Within them, deltas are particularly vulnerable, as they experience intense anthropogenic pressures and the effects of climate change, which are even more pronounced in the Mediterranean Sea. These environments face an increasing risk of coastal flooding, wetland loss, shoreline retreat, and infrastructure deterioration.
Therefore, it is essential to have high spatial and temporal resolution data for monitoring these areas. In this context, bathymetric information is crucial for marine environmental planning, navigation, fisheries management, and many other applications. However, both large- and small-scale bathymetric data are limited and expensive. In response to this limitation,cost-effective alternatives for bathymetric monitoring have been explored, with Satellite-Derived Bathymetry (SDB) emerging as a viable option to complement conventional techniques.
This research used a Do It Yourself (DIY) bathymetric sensor, specifically designed to obtain in situ data and extract Satellite-Derived Bathymetry (SDB) at the river mouth of the Ebro Delta (NW Mediterranean Sea), in order to analyze changes in the bathymetry between 2023 and 2025. For this purpose, four sampling campaigns were carried out at the mouth of the delta, combining the obtained data with images from the Sentinel-2A/B mission of the Copernicus Program. The Sentinel-2 images were processed using the ACOLITE processor to perform atmospheric and sunglint corrections. The objective of this research is to demonstrate the feasibility of using DIY technologies to obtain in situ bathymetric data in coastal areas, which can support the extraction of SDB. These technologies are especially useful for countries in the process of development and initiatives with open and collaborative science platforms (i.e. citizen science). Validating this methodology will contribute to providing access to bathymetric data essential for coastal zone management and mitigation of the future impacts of climate changes.
How to cite: Calvillo, B., Puigdefàbregas, J., Grifoll, M., Gracia, V., and Sanchez-Arcilla, A.: Do It Yourself Instrumentation for Extracting Satellite-Derived Bathymetry: The Case of the Ebro Delta, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4816, https://doi.org/10.5194/egusphere-egu25-4816, 2025.
Typhoons pose significant threats to harbors and coastal infrastructures through intense waves that can cause direct damage. Even typhoons located at a distance can generate swells that propagate into harbors, leading to harbor oscillations. Such oscillations cause moored ship motions with consequences for the operational downtime of dock operation. This study focuses on an offshore liquefied natural gas port in the southwestern Taiwan, Yongan Harbor, completed in 1990. Since its completion, the harbor has faced typhoon-generated swells, induced long-period wave oscillations and overtopping, thereby compromising dock operation safety. To mitigate this problem, additional breakwaters were constructed in 2005 to narrow the harbor entrance for better protection. However, instead of improving harbor tranquility, this modification unexpectedly prolonged wave oscillations and amplified wave amplitudes, as reported by longshoremen, though no field data available to confirm this phenomenon. To investigate the wave characteristics, a wave-resolving model is applied to simulate the spatial distribution of swells and infragravity waves before and after the harbor modifications. The model results indicated that waves concentrated energy along the breakwater walls and corners, intensifying harbor oscillations and affecting the safety and efficiency of port operations. Further simulations of typhoon-induced swells revealed that the primary oscillation periods within the harbor remained unchanged before and after the new constructions. However, the post-construction harbor configuration amplified the energy of these wave periods within the harbor. This amplification shows that while the harbor modifications aimed to enhance protection, they inadvertently intensified specific natural resonance periods, leading to increased oscillation durations. The findings highlight the importance of comprehensive wave hydrodynamics in harbor design and modification. It is crucial to consider not only the immediate protective benefits to narrow the harbor entrance but also their potential to alter wave patterns within the harbor. Future harbor designs should integrate advanced simulation models to predict and mitigate adverse oscillation effects, ensuring dock safety and operational efficiency.
How to cite: Su, S.-F. and Chen, I.-A.: Numerical modeling of harbor oscillations induced by typhoon-generated swell waves: a pre-post study of harbor modification, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4942, https://doi.org/10.5194/egusphere-egu25-4942, 2025.
Primary production in coastal bays and estuaries is shaped by various physical factors, including wind, tides, freshwater inflows, and light availability. Over short timeframes, these factors can affect other key variables, such as phytoplankton biomass and nutrient levels in the water. Research conducted in Fangar Bay—a small, shallow, microtidal bay in the northwest Mediterranean Sea—has highlighted spatial and temporal variations in phytoplankton biomass linked to different wind patterns. This bay is characterized by regular sea breezes and occasional episodes of intense northwesterly winds, which can mix the water column for varying durations.
To analyse both temporal and spatial variability, the Regional Ocean Modelling System (ROMS), integrated with a nitrogen-based NPZD (nutrient, phytoplankton, zooplankton, and detritus) model, was used to simulate eco-hydrodynamics in Fangar Bay. Four sampling points were selected to observe changes in phytoplankton concentration across the bay. During sea breeze events (wind speeds of 6 m·s⁻¹), vertical stratification dominates, leading to higher phytoplankton concentrations near the sea surface compared to the bottom. Conversely, during strong NW wind episodes (exceeding 10 m·s⁻¹), the water column becomes fully mixed, equalizing nutrient distribution and increasing phytoplankton biomass in deeper layers.
Additionally, the dispersion of freshwater plumes from irrigation channels significantly influences the spatial distribution of phytoplankton biomass within the bay. Numerical simulations confirm the role of freshwater plume dynamics in shaping the distribution of both phytoplankton and other water properties, aligning with observations from remote sensing. These findings offer valuable quantitative insights for developing more sustainable management strategies for such environmentally sensitive coastal areas.
The analysis of phytoplankton biomass dynamics in the Fangar Bay provides essential insights for implementing nature-based solutions (NBS) aimed at improving water quality. This knowledge enables the optimisation of freshwater discharge management and its interaction with prevailing winds, promoting natural processes such as water mixing and renewal. These strategies, inspired by the bay’s ecological cycles, can help reduce excessive phytoplankton growth and mitigate issues like eutrophication, contributing to the sustainability of the coastal ecosystem.
Keywords: phytoplankton biomass, ROMS-NPZD model, wind, biological parameters, chlorophyll-a, Fangar Bay.
Funding: This work has been funded by the I+D+i project ECO-BAYS (PID2020-115924RB-I00) financed by MCIN/AEI/10.13039/501100011033
Acknowledgements: We would like to thank the REST-COAST project (H2020-101037097-REST-COAST) European Union’s Horizon 2020 program. As a group, we would like to thank the Departament de Recerca i Universitats de la Generalitat de Catalunya (2021GR0060)
How to cite: Balsells F-Pedrera, M., Grifoll, M., Espino, M., Fernández-Tejedor, M., and Sánchez-Arcilla, A.: Analysis of primary biomass dynamics in a micro-tidal estuary: The case of Fangar Bay., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5600, https://doi.org/10.5194/egusphere-egu25-5600, 2025.
The Suez Canal holds a pivotal role in global navigation and supply chains by facilitating the movement of goods between the East and West. Around 50 vessels navigate the canal daily. However, a pressing concern threatens its operational stability: the escalating sediment deposition that necessitates frequent canal dredging. While these sediments originate from diverse sources like land erosion in the northern Sinai and tributaries to the canal, a significant portion could originate from the Nile Delta. This sediment influx results from heightened erosion in the Nile delta, a consequence of reduced Nile River discharge. Multiple factors contribute to this discharge reduction, including upstream damming activities, intensified water usage for agriculture, and population growth in the Nile Basin. The grounding of the Ever Given container ship in 2021 illustrated the consequences of a congested Suez Canal, potentially causing substantial delays and economic losses in global trade. This research project aims to comprehensively grasp the dynamics of sediment transfer from the Nile Delta to the Suez Canal, considering the potential effects of current and future Nile River damming. To fulfill this goal, an integrated framework will be established, bridging the gap between alterations in Nile River discharge, sediment origins in the Nile Delta, and their accumulation in the Suez Canal. This framework will facilitate the quantification of sediment proportions reaching the canal and the assessment of navigation risks posed by these sediments under existing conditions and future discharge scenarios.
How to cite: Versaen, A., Hanert, E., Heggy, E., and Lambrechts, J.: Multi-scale modelling of the water and sediment fluxes from the Nile Delta to the Suez Canal, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5825, https://doi.org/10.5194/egusphere-egu25-5825, 2025.
In the context of a warming world, annual bleaching events are becoming more likely and threaten coral reefs on a global scale, leading to a growing interest in identifying local-scale thermal refugia. However such shallow reef refugia are predicted to disappear in a +2.0 °C climate world. Yet, hope remains as Northern Red Sea (NRS) corals could act as a thermal refuge until the end of the century. While being virtually immune to climate change, these so-called ‘super-corals’ are not immune to anthropogenic stressors such as the NEOM mega-project. Here, we used the three-dimensional multi-scale ocean model SLIM3D coupled with a Lagrangian Particle Tracker model to simulate sediment dispersal originating from coastal development sites and assess the environmental impact of the NEOM project on NRS corals. We show that fine sediments (<32μm) have a high potential to impact the entire Gulf of Aqaba (GoA) and part of the NRS, as they can remain suspended in the water column for up to one month and can settle 200 km away from their release site. We identified the most exposed reefs located within 10 km of Sindalah and along 45 km of the Oxagon coastline. Furthermore, we highlight that all the most exposed reefs are located in the NRS; none are within the GoA. To our knowledge, this work is the first to quantitatively assess the environmental impact of the NEOM project on NRS and GoA shallow coral reefs. Based on our results, we expose the need for the implementation of mitigation measures to ensure sustainable coastal development. In a broader way, our model could provide further insights into marine pollution (e.g. desalination plants brines, hydrocarbon pollution) and mesophotic-shallow reef interaction.
How to cite: Van Eetvelt, M., Scherpereel, C., Lambrechts, J., and Hanert, E.: Preliminary assessment of the environmental impact of NEOM coastal developments on the Northern Red Sea coral reefs, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5952, https://doi.org/10.5194/egusphere-egu25-5952, 2025.
Understanding along-fjord flow and fjord-shelf exchange around Greenland is key to comprehend inland-freshwater export to Greenland Sea and shelf-water import into fjords. In Northeast Greenland processes driving fjord-shelf exchange remain poorly understood even though these processes are crucial for nutrient supply, and heat transport, among others. Here, we combined records of wind from meteorological towers and water currents from a moored ADCP to assess seasonal along-fjord flow and consequent fjord-shelf exchange in Young Sound Fjord. Results show seasonality in the direction of the wind. Northerly winds predominated in September-April and southeasterlies in June-July. May and August were transitional periods. In ice-free periods, variability in along-fjord transport mirrored wind direction and intensity. In-fjord winds drove in-fjord flow and winds in the opposite direction enhanced on-shelf transport. Most of the exports occurred in the top 10 m where velocities were an order of magnitude greater than below. Bottom in-fjord transport was partially attributed to a wind-driven compensatory flow. During ice-covered conditions, intense winds generated a coastal polynya coupling winds with currents in the water column. For the whole record on-shelf transport was on average an order of magnitude greater than in-fjord import of shelf water. δ18O shows Polar Water was imported in the lower part of the water column while inland freshwater was exported in the upper 10-15 m. This study highlights that, to comprehend freshening of Greenland Sea, winds in fjords and associated transport must be considered.
How to cite: Ruiz-Castillo, E., Boone, W., Ponsoni, L., and Rysgaard, S.: Seasonal variability in the along-fjord flow in a Northeast Greenland fjord, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12708, https://doi.org/10.5194/egusphere-egu25-12708, 2025.
The Changjiang River discharges substantial freshwater into the East China Sea, forming the Changjiang Diluted Water (CDW), a low-salinity plume that influences regional hydrography, nutrient distribution, and marine ecosystems. CDW intrusions into Korean coastal waters can cause abrupt salinity and temperature changes, impacting fisheries and promoting harmful algal blooms. Climate change-driven variations in precipitation have altered CDW discharge patterns, increasing uncertainties in its behavior and impacts on marine environment. In this study, numerical simulations were used to assess CDW propagation and its influence on hydrographic properties of neighboring seas during the summer of 2024 using the MOHID (Modelo Hidrodinâmico) model. To investigate the influences of the CDW, we conducted two distinct numerical simulations. The first experiment was simulated with the original Chanjiang discharge, allowing CDW plume to enter the seas adjacent to the Changjiang River. In the second experiment, Changjiang outflows was capped at 30,000 m3/s, thereby limiting the freshwater flux from the CDW into the study area. As a result, on July, a significant impact of the CDW on both surface temperature and salinity in the study area. The temperature anomalies reached up to 2 ℃, while salinity decreased by as much as 4 psu. It indicates the strong influence of CDW on surface hydrography. The cross-sectional analysis revealed the influences of the CDW. A distinct halocline was observed due to the low-salinity plume in the upper 20 meters, and it might lead to surface warming while subsurface cooling due to suppressed vertical mixing. These results highlighted the considerable influence of the CDW on both horizontal and vertical hydrographic properties of the neighboring seas. Therefore, continued monitoring and numerical modelling approach to those low-salinity water plumes are essential to anticipate and mitigate potential ecological and economic impacts.
How to cite: Lee, D. and Choi, J.-Y.: A Study on the Impacts of the Changjiang Diluted Water (CDW) on Surface Warming in the East China Sea using the MOHID in Summer, 2024, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14523, https://doi.org/10.5194/egusphere-egu25-14523, 2025.
The tidal flats along the Korean west coast have experienced significant area changes due to both natural and anthropogenic factors, including ongoing development, erosion, land reclamation, and sea level rise. These tidal flats hold substantial ecological, economic, and environmental value, necessitating systematic management through monitoring area changes. Recently, tidal flat investigations have increasingly utilized satellite imagery, which allows for periodic and large-scale observations. This approach effectively addresses the accessibility limitations of traditional field surveys and the high costs associated with platforms like ships or aircraft. However, tidal flat regions pose challenges for satellite-based observations due to tidal variations, making it difficult to capture images at specific times such as lowest and highest tide. Furthermore, frequent cloud cover in coastal areas imposes significant constraints on acquiring input data for tidal flat mapping.
This study applied a machine learning based classification method to minimize the effects of cloud cover and tidal variations during the tidal flat mapping process. It utilized synthetic datasets derived from time-series imagery, incorporating indices such as the Normalized Difference Water Index (NDWI) and Enhanced Vegetation Index (EVI), along with brightness information from individual images. Using this approach, the study developed tidal flat area maps for the Korean west coast over a 40-year period from 1984 to 2024, using Landsat satellite series data in 5-year intervals. A case study was conducted to analyze area changes over time, and the accuracy of the generated tidal flat maps was validated against tidal flat area data provided by the Korea Hydrographic and Oceanographic Agency (KHOA).
The results demonstrated that the machine learning-based method produced reliable tidal flat maps, effectively mitigating the impacts of clouds and tidal conditions. Moreover, the approach successfully monitored long-term changes in tidal flat areas. This study provides essential scientific evidence for the systematic management and conservation of Korea tidal flats and is expected to contribute to the formulation of sustainable tidal flat management policies in the future.
How to cite: Lee, J., Kim, K., Lee, D., Kwak, G.-H., and Ryu, J.-H.: Long-Term Changes of Tidal Flat Areas in the Korean West Coast Using Time Series Satellite Imagery, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16135, https://doi.org/10.5194/egusphere-egu25-16135, 2025.
We present a novel modelling approach aimed at optimising sampling strategies for environmental DNA (eDNA) based ecosystem monitoring. We demonstrate this in a case study for the monitoring of an invasive mussel species in Auckland Harbour Bay. The chosen objective is to identify a set of ship-based sampling locations that provide the highest spatial coverage for a given number of samples collected by towing a filter through the water.
This objective is achieved by leveraging the high performance of the particle tracking model 'oceantracker', which simulates over a trillion (1e12) individual particles for this demonstration. We apply this particle tracking model - also known as a Lagrangian model - to an inverse problem by simulating a large number of potential mussel locations throughout the bay. The simulated mussels continuously shed cells containing their DNA into the surrounding waters, which drift with the currents and slowly decay, represented by a Poission process. By computing grid-based statistics on-the-fly, i.e. during runtime, we are able to reduce the unweildy amount of data generated by the trajectories of trillions of simulated particles to obtain a compact dataset containing eDNA counts and concentrations for each potential source location. This data set is then used in the optimisation problem to identify the sets of ideal sampling locations that exceed the detection threshold for the largest number of potential source locations, i.e. have the highest coverage.
As ship-based monitoring is an expensive task, we suggest that the use of a modelling framework such as the one demonstrated here could help to reduce this cost and provide an empirical solution to the selection of sampling locations.
How to cite: Steidle, L. and Vennell, R.: Optimisation of eDNA sampling strategies: A novel Lagrangian approach for identifying optimal sampling locations in marine environments, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20240, https://doi.org/10.5194/egusphere-egu25-20240, 2025.
Fangar Bay, a semi-open bay with micro-tidal dynamics, is located in the Ebro Delta (NW Mediterranean Sea). Over the past few decades, the bay, a key area for aquaculture and rice cultivation, has been increasingly influenced by human activities and climate change. To better understand this sensitive area, we investigated the bay's hydrodynamics and the impact of freshwater discharge. Using the TELEMAC 3D model, we preliminarily included the internal and external forces affecting the bay's hydrodynamics (i.e, meteorological forcing, river fluxes, regional hydrodynamics provided by CMEMS products). For coastal semi-enclosed waters with a depth of less than 4 m, the model achieved a relatively high-resolution grid (24 m) and completed the preliminary verification of temperature and salinity in the profile, as well as the initial verification of water flow speed and direction at the bay mouth and within the bay. Collaborative efforts with UPC/LIM and IRTA included Rhodamine experiments, which support the validation of the model using a numerical conservative tracer, the comparison results between model and Drone data also show acceptable goodness of fit This study combines field campaigns and numerical modeling to propose effective strategies for the governance and optimization of the bay activities. Also, it has been verified that high-resolution numerical models are an effective technical means for studying the hydrodynamics of complex and sensitive coastal waters.
How to cite: Chen, Y., Peñas-Torramilans, R., Fernández, M., Balsells F-Pedrera, M., Grifoll, M., and Espino, M.: Modelling Rhodamine dispersion experiments in Fangar bay case (NW Mediterranean sea), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12486, https://doi.org/10.5194/egusphere-egu25-12486, 2025.
The Tsushima Warm Current (TSWC), which flows through the Korea Strait (KS), is crucial in transporting nutrient-rich, warm, and saline water to the East/Japan Sea. Understanding the origins and variability of the TSWC is essential because of its significance in Northwestern marginal seas. Although previous studies have suggested that the Taiwan Strait (TS) partially originates from the TSWC, the seasonal and interannual variability in the material connectivity between the TS and KS remains poorly understood. In this study, we investigated this variability using a Lagrangian particle-tracking system and a three-dimensional numerical model. The model results showed that particles originating from TS passed through KS most frequently in August. Furthermore, particles traveling from the TS to KS exhibited distinct interannual variability. Composite analysis indicated that southerly winds increased sea surface height (SSH) in the southwestern East China Sea (ECS) shelf region via surface Ekman transport, weakening cross-shelf offshore currents and preventing particles from being transported offshore. Empirical Orthogonal Function (EOF) analysis indicated that the interannual variability of southerly winds over the ECS was associated with variations in SSH in the southwestern shelf region, thereby influencing material transport from the TS to the KS.
How to cite: Lee, S.-T., Kim, Y.-Y., Tak, Y.-J., Chae, S., and Cho, Y.-K.: Seasonal and interannual variations in material transport in the Korea Strait originating from the Taiwan Strait, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2628, https://doi.org/10.5194/egusphere-egu25-2628, 2025.
The relationship between significant wave height and wind speed has been extensively studied for a long time. Previous studies have indicated a relationship between these two variables. The relationship can be expressed as the significant wave height proportional to the square of the wind speed or through a scaling exponent. Taiwan is an island located in the Western Pacific. The northeast monsoon prevails in winter, while the southwest monsoon dominates in summer. The wind speed in the former is stronger than that in the latter. To gain insights into the marine conditions surrounding Taiwan, the Central Weather Administration of Taiwan has deployed several mooring buoys in some waters to collect wind and wave data. This study utilized data from these buoys to derive the most applicable wind-wave relationship for the waters surrounding Taiwan. The results show that under northeasterly winds, the significant wave height is related to the 0.81 power of wind speed in the northeastern waters of Taiwan, 0.95 power in the western waters, 1.29 power in the southwestern waters, and 0.94 power in the eastern waters. These exponents are notably lower than those of the quadratic law applicable to fully developed waves. Under north-northeast winds, the same relationship exists in the northeastern and southwestern waters, but not in the western and eastern waters. This may be attributed to the influence of coastal topography on wave generation and propagation dynamics. The analysis also found that only the northeast wind and north-northeast wind follow the power relationship, while other wind directions do not.
How to cite: Ho, C.-R., Cheng, K.-H., and Yang, Y.-C.: Power difference of the relationship formula between significant wave height and wind speed in Taiwan waters, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3959, https://doi.org/10.5194/egusphere-egu25-3959, 2025.
Coastal KOOS (MOHID), developed and operated by the Korea Institute of Ocean Science and Technology (KIOST), is an advanced three-dimensional ocean prediction system designed to simulate and forecast oceanic conditions along the coast of the Korean Peninsula. The system incorporates meteorological factors to predict key ocean parameters, including Sea Surface Temperature (SST). Despite its capability to reproduce SST relatively well, differences occur in certain aspects of predictions. Specifically, while the system can closely match observed SST, errors in the timing, intensity, and duration of cold water events persist. These errors are primarily attributed to differences in how the model represents the vertical distribution of water temperatures. In particular, the model may not fully account for the interaction between cooler waters at deeper layers and surface conditions, affecting the onset, strength, and longevity of cold water events.
To reduce numerical error and improve the accuracy of cold water zone predictions, the study concentrated on enhancing the simulation of the vertical distribution of water temperature. The main objective was to determine how modifications to the initial seawater temperature profile would impact predictions of cold water zones. The initial conditions were reconstructed using quality-checked observational data collected during a cold water event along the southeastern coast of the East Sea of Korea between August 18 and September 4, 2021. This concentrated observational data provided high-resolution information on the vertical distribution of water temperature, enabling the model better to represent the temperature distribution throughout the water column.
By reconstructing the initial vertical distribution of water temperature, the result enhances the accuracy of predicting not only SST but also the timing, intensity, and duration of cold water events. This improvement would offer a more accurate and reliable forecast for the occurrence and behavior of cold water zones. The anticipated benefits of improved cold water zone predictions include better management of marine resources, such as fisheries, which are highly sensitive to temperature changes. Additionally, this improvement could support informed decision-making for coastal infrastructure, such as climate monitoring and environmental protection, particularly in changing weather patterns and evolving oceanic conditions.
How to cite: Kwon, Y.-Y., Gu, B.-H., and Choi, J.-Y.: Effect of prediction accuracy using three-dimensional reconstructed initial seawater temperature based on observed profiling data., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14095, https://doi.org/10.5194/egusphere-egu25-14095, 2025.
The contamination of sediments with hazardous substances in the coastal waters of South Korea adversely affects the health of marine ecosystems, causing water quality deterioration, hypoxia, red tides, foul odors, and ecological toxicity. This necessitates rapid identification of pollution sources and their resolution. However, the diversity of pollutant types and sources across regions poses challenges to pollution mitigation and management. To address this, there is a need for technology capable of quantitatively evaluating the contributions of complex pollution sources, as well as a system that supports user-friendly data querying, filtering, and visualization. Such a system should also facilitate information and data sharing among users, fostering collaboration within organizations and with external partners.
In response, we developed an automated program for pollution source attribution, encompassing the entire process from data analysis algorithms to result visualization. The program integrates multiple source attribution methods, including the Chemical Mass Balance (CMB) model, Non-Negative Matrix Factorization (NMF) model, and Bayesian Isotope Mixture (BIM) model, to enhance the identification of pollution origins. To ensure accessibility and ease of use, the program was implemented using R Shiny, a web-based platform built on the R programming language.
The automated program accepts csv files as input to estimate pollution contributions and provides visualization of modeling results through graphs, matrices, and geospatial point contributions on maps. This approach enhances researchers' understanding and facilitates efficient utilization of the results.
How to cite: Park, Y.-G., Kim, T.-H., Lee, G.-S., Kim, B.-R., and Do, Y.-B.: Development of Pollution Contribution Estimation Algorithms and a Web-Based Automated Program, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14776, https://doi.org/10.5194/egusphere-egu25-14776, 2025.
This study evaluates the effectiveness of simulation accuracy based on the Korean Ocean Research Stations (KORS), and it suggests the optimal design of ocean observation networks using Observing System Simulation Experiments (OSSE) focused on the South Sea of Korea. The virtual observation points used in the OSSE were set based on the locations of operational mooring buoys managed by the Korea Hydrographic and Oceanographic Agency (KHOA), the Korea Meteorological Administration (KMA), and KORS. The numerical model of the study area was established to consider the Exclusive Economic Zone (EEZ) around the South Sea of Korea. Also, an unstructured grid ocean model was applied considering the irregular topographical characteristics of the South Sea. This simulation experiment used meteorological and external forcing from the Korea Operational Oceanographic System (KOOS), which is operated by the Korea Institute of Ocean Science and Technology (KIOST). The 'true state' for OSSE was assumed to be the Coastal KOOS, and data assimilation was applied to preset observation points and groups. A total of 38 OSSE experiments were conducted for the summer of 2022. Results indicate that buoys located south of Jeju Island significantly improved surface current velocity, temperature, and salinity simulations along the South Sea coast. However, the accuracy of the sea surface temperature (SST) was improved only when the differences between existing observations and the background state exceeded a critical value. By applying this, considering the bias of observation buoys in forecasting systems using satellite data can improve prediction accuracy. Improvements were observed in current and salinity about seasonal variability, but the effects on short-term variability, which is less in scale, were less pronounced than SST. Future studies aim to extend the OSSE study to underscore the importance of observation network design based on Sea of Korea and improve the prediction accuracy of corresponding real-time ocean forecasting systems.
How to cite: Gu, B.-H., Kim, N.-H., Choi, J.-Y., and Kwon, J.-I.: Study on Observing System Simulation Experiments (OSSE) for Ocean Forecasting Based on Observation Networks of Korea, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14825, https://doi.org/10.5194/egusphere-egu25-14825, 2025.
Internal waves (IWs) play a critical role in ocean mixing processes and in the redistribution of energy and momentum. These waves are typically generated by initial perturbations, such as wind forcing at the surface, tidal interactions, and seiches interacting with abrupt bathymetric changes. A numerical study has demonstrated that seiches in semi-enclosed water bodies, such as bays, can generate IWs through energy dissipation at the open boundary via baroclinic wave drag, suggesting that bays may serve as potential energy sources for the ocean.
In this study, we use the MITgcm numerical model to simulate a seiche event in an idealized semicircular bay, based on the dimensions of Sebastián Vizcaíno Bay in Baja California, Mexico. We examine three stratification scenarios to evaluate the generation mechanism of IWs and their sensitivity to stratification. The scenarios include a barotropic case, a two-layer stratification, a realistic stratification, and a linear stratification. To analyze the structure and evolution of IWs, we use vertical velocity (www) profiles obtained at various oceanic locations. Additionally, we calculate the energy transfer from the seiche to the ocean by comparing the evolution of kinetic and potential energy in the ocean with that of the seiche, and assess the seiche’s decay rate under the different stratification scenarios.
Preliminary results reveal that the generated IWs have a period matching the fundamental seiche period of 3.6 hours due to geometry of the bay. Coastal trapped waves originating from the bay were also identified. For scenarios with continuous stratification, the linear profile scenario exhibited a uniform distribution of internal waves throughout the depth, attributed to the dispersion relation and the constant Brunt-Väisälä frequency.
How to cite: Cruz Isidro, E. and Ramos Musalem, K.: Numerical study of internal waves generated by a seiche in a bay, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16857, https://doi.org/10.5194/egusphere-egu25-16857, 2025.
Coastal zones, as dynamic interfaces between land and sea, are critical for economic activities, ecological conservation, and human habitation. However, natural sediment systems are increasingly disrupted by artificial interventions and rising sea levels accelerated by climate change, leading to erosion and uncertainty in the stability of the coastal zone. Effective coastal management requires not only accurate monitoring but also large spatial scale and long-term temporal coverage of shoreline observations. While traditional in-situ and aerial survey methods provide high precision, they are labor-intensive and limited in scope. Optical satellite imagery emerges as a viable alternative, offering continuous, broad spatial coverage. Furthermore, advances in image processing with artificial intelligence enable shoreline extraction and long-term change analysis.
This study marks the initial step in utilizing optical satellite imagery for analyzing long-term shoreline changes along the Korean Peninsula, where artificial approaches such as gray structural coastal disaster prevention methods are mainly applied. Specifically, this study focused on the East Sea region of the Korean Peninsula, a high-risk area for coastal erosion, and examined approximately 40 years of shoreline changes using publicly available satellite data, including Sentinel-2 and Landsat series satellite images. First, an automatic satellite image download system was designed using the Google Earth Engine API, incorporating appropriate parameter settings for the region of interest and ensuring uniform data quality based on the characteristics of satellite imagery. Second, effective preprocessing techniques were applied to improve shoreline recognition from each satellite image. Third, the lower resolution of Landsat images relative to Sentinel-2 was enhanced through super-resolution generative adversarial network, enabling more precise identification of shoreline features. Fourth, the open-source software, CoastSat(Vos, 2019) was utilized to extract shorelines, and this study analyzed shoreline changes based on comprehensive coastal engineering knowledge. Finally, the feasibility of the proposed method was validated by analyzing the cross-sectional time series of the shoreline at the littoral cell of Wonpyeong-Chogok beach, an area where various coastal structures have been installed over the past decades to mitigate coastal retreat. These findings illustrated the shoreline responses and geomorphological changes resulting from the sequential construction of coastal structures.
This study underscores the potential of using elaborate image enhancement techniques, including contrast stretching, spatial registration and super-resolution, to analyze long-term shoreline dynamics with high accuracy. By applying these methods to satellite imagery spanning four decades, we provided insights into shoreline responses to sequential coastal structures. These findings contribute to supporting proactive coastal management in the face of growing uncertainties, emphasizing the importance of integrating advanced image processing and unsupervised learning for effective shoreline extraction and geomorphological analysis.
Reference
Vos, K., Splinter, K. D., Harley, M. D., Simmons, J. A., & Turner, I. L. (2019). CoastSat: A Google Earth Engine-enabled Python toolkit to extract shorelines from publicly available satellite imagery. Environmental Modelling & Software, 122, 104528.
How to cite: Yun, M., Mo, B. Y., Kim, J., Do, K., Yi, S., Park, D., Kim, I., and Chang, S.: Long-Term Shoreline Change Analysis using Optical Satellite Images of the east coast of the Korean Peninsula, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17752, https://doi.org/10.5194/egusphere-egu25-17752, 2025.
A numerical model is presented to evaluate coastal sediment transport. The model is embedded in the open-source software REEF3D. A main component to determine potential coastal erosion is the bed shear stress exerted on the sediments. The numerical model is validated for a cross-shore scenario against measurements of wave profiles and bed shear stresses induced by a solitary wave. In addition, a large-scale case of a coast located at the Baltic Sea in Estonia is investigated with regard to wave modelling and sediment transport potential.
The REEF3D framework offers a 3D hydrodynamic model with a water- and air-phase REEF3D::CFD as well as a surface and bottom following non-hydrostatic sigma-grid model REEF3D::NHFLOW. Both models are coupled with a morphological module. This investigation shows the applications of both approaches with regard to prediction of waves reaching the shoreline, where they deform, shoal or break depending on the bathymetry. The wave-induced flow at sloping beaches leads to morphological changes. Erosive and aggregative conditions are important to assess in order to identify problematic zones and ensure proper coastal management and engineering.
The validation of the model against solitary wave experiments demonstrates its capability to accurately predict the wave dynamics and resulting bed shear stresses, which are crucial for understanding sediment mobility. For the Baltic Sea case study, the model successfully simulates wave transformation and sediment transport potential under various hydrodynamic conditions, showcasing its versatility for real-world applications.
This work highlights the importance of numerical modelling in coastal engineering, offering insights into sediment dynamics and the impact of hydrodynamic forces on coastal morphology. By leveraging the open-source capabilities of REEF3D, the study provides a framework that can be adapted for diverse coastal environments. The integration of detailed hydrodynamic and morphological modules allows for the comprehensive analysis of sediment transport processes, enabling effective decision-making for coastal protection and sustainable management strategies.
How to cite: Ehlers, R., Männikus, R., Wang, W. W., and Bihs, H.: Wave-Induced Sediment Transport Analysis Using Hydro- and Morphodynamic Modelling in Coastal Environments, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17866, https://doi.org/10.5194/egusphere-egu25-17866, 2025.
Effective management of urban coastlines and port areas relies heavily on accurate prediction and understanding of local coastal processes, particularly in regions where nearshore morphology and bathymetry have a significant influence on ocean circulation and wave transformation. This work presents a state-of-the-art three-dimensional modelling tool designed to improve the prediction of ocean and wave conditions in the Barcelona coastal zone. The tool uses the Coupled Ocean-Atmosphere-Wave-Sediment Transport Modelling System (COAWST) [1], which uses the Model Coupling Toolkit to synchronise the Regional Ocean Modeling System (ROMS) with the Simulating Waves Nearshore (SWAN) model. By exchanging relevant predictor variables between the models, the system more accurately captures wave-current interactions, a key mechanism governing nearshore dynamics [2].
A nested grid strategy supports the model framework, with horizontal resolutions ranging from 350 m in the outer domain to 70 m and then 14 m in progressively refined subdomains covering the Port of Barcelona and adjacent beaches. This nesting approach enables fine-scale predictions of hydrodynamic and wave processes, including spatial variations in wave height, period and direction. Bathymetric inputs are derived from EMODnet [3] and improved with site-specific high-resolution datasets, while boundary conditions are driven by Copernicus Marine Service data [4].
Rigorous validation against in-situ observations - in particular during the severe storm Celia in March 2022 - demonstrates the system's ability to provide reliable predictions of coastal hydrodynamics. By integrating wave-current processes, the model provides valuable insights for day-to-day coastal operations, long-term resource management and assessment of climate-related hazards.
Planned future work includes the assimilation of improved ocean observations and the refinement of atmospheric forcing to improve model accuracy and predictive capability. Ultimately, these efforts will inform sustainable management strategies, promote the resilience of coastal communities and support the harmonious coexistence of human activities with marine and coastal ecosystems along the Barcelona coast. This research will provide key insights for policy makers and stakeholders, promoting the sustainable integration of human activities with marine ecosystems and increasing the resilience of Barcelona's coastal communities through accurate, predictive data.
Funding: This research is supported by funding from the European Union’s Horizon 2020 Research and Innovation Action, under Grant Agreement No. 101037097 for the REST-COAST project.
Acknowledgments: This research is supported by the ECCO_TS project, financed by the Spanish Ministerio de Ciencia, Innovación y Universidades (contract no. PID2023-152363OB-I00). As a group, we would like to thank the Departament de Recerca i Universitats de la Generalitat de Catalunya. Convocatòria d'ajuts a Grups de Recerca de Catalunya (SGR-Cat 2021) 2021SGR00600.
References:
[1] Warner, J.C., Armstrong, B., He, R., and Zambon, J.B. (2010). Development of a Coupled Ocean Atmosphere-Wave-Sediment Transport (COAWST) modeling system: Ocean Modeling, v. 35, no. 3, p. 230-244.
[2] Kumar, N., Warner, J.C., et al. (2011). Wave-current interaction in Willapa Bay. Journal of Geophysical Research. Retrieved from https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2011JC007387.
[3] EMODnet data base (https://www.emodnet-bathymetry.eu/).
[4] Copernicus data (https://marine.copernicus.eu/).
How to cite: Liste, M., Mestres, M., and Espino, M.: Enhanced Nearshore Forecasting in Barcelona, Spain: A Next-Generation, High-Resolution Wave-Current Modelling Tool., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18609, https://doi.org/10.5194/egusphere-egu25-18609, 2025.
The East/Japan Sea (EJS) is a semi-enclosed marginal sea in the Northwest Pacific Ocean, characterized by oceanographic features typically associated with large-scale systems, such as thermohaline circulation, submesoscale eddies, subpolar front, and intermediate water formation. Submesoscale eddies frequently form along the ESJ polar front, playing a crucial roles in large-scale processes, including turbulent ocean mixing, surface nutrient transport, and the support of chlorophyll blooms. Despite its significance, large portions of the EJS remain underobserved, leaving gaps in our understanding of its complex dynamics.
We present the establishment and evaluation of the high-resolution (1/48 ˚) East Sea regional model using MOM6, the latest version of the Modular Ocean Model (MOM) developed by GFDL to capture the submesoscale dynamics. The model was designed with a spatial resolution of approximately 2km (1/48 ˚) and employs a hybrid vertical coordinate system. High-resolution (1/24˚) Northwest Pacific Ocean reanalysis (KOOS-OPEM), which reliably reproduces the characteristics of the EJS, were used for the initial and open boundary conditions.
We investigated the variability in the separation latitude of the East Korea Warm Current (EKWC), a western boundary current in the EJS, under different wind forcing datasets. For this analysis, we used the ERA5 dataset from ECMWF, featuring a horizontal resolution of approximately 31 km and a temporal resolution of 1 hour, as well as the UM model data from the Korea Meteorological Administration, which offers a higher horizontal resolution of approximately 12 km and a temporal resolution of 6 hours. In addition, to validate submesoscale processes, the kinetic energy spectrum was then calculated via the Discrete Fourier Transform (DFT) and systematically evaluated.
This study provides significant insights into the submesoscale dynamics of the EJS and establishes a robust foundation for advancing regional ocean modeling efforts.
How to cite: Kim, H., Lee, E. Y., Lee, D. E., and Kim, Y. H.: Simulation and Validation of Submesoscale Dynamics in the East/Japan Sea Using MOM6, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18830, https://doi.org/10.5194/egusphere-egu25-18830, 2025.
Arctic fjord ecosystems are undergoing rapid changes due to climate warming, glacier retreat, and shifts in oceanography, with significant implications for biogeochemical cycling and biological productivity. As glaciers retreat and discharge increases, fjords are becoming fresher, and fjord morphology is changing, altering circulation, vertical structure, and the light environment. Traditionally, fjords with marine-terminating glaciers have been considered more productive due to nutrient renewal from subglacial discharge plumes. However, this relationship is more complex, as productivity depends not only on mixing mechanisms but also on nutrient concentrations, phytoplankton presence, and light availability. This study examines lipid concentrations and isotopic compositions across different Greenlandic fjord systems. These systems encompass diverse conditions, from eutrophic waters in West Greenland, influenced by nutrient-rich Atlantic inflows, to oligotrophic waters in East Greenland, shaped by polar waters and glacial melt. Our data revealed distinct regional differences linked to external forcings. West Greenland exhibits higher lipid concentrations and isotopic values, driven by marine phytoplankton and influenced by Arctic and North Atlantic currents. In contrast, East Greenland’s lipid profiles are shaped by polar waters, and sea ice algae with lower isotopic values linked to terrestrial runoff. These findings highlight the interconnectedness between fjord ecosystems and broader climatic and oceanic drivers, underscoring the importance of external boundary conditions in predicting the future of fjord productivity. The impact of climate warming and sea ice melting will be therefore spatially different and strongly dependent on the distinct oceanographic processes within the different regions. By linking fjord morphology and regional oceanography to productivity, this work highlights the need to integrate internal fjord dynamics with external boundary conditions to predict future ecosystem productivity in Arctic fjords.
How to cite: Allais, L., Holding, J., Mostovaya, A., Henson, H., and Puts, I.: Glacier type drive Greenland fjord productivity: a Lipid seascape perspective, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19254, https://doi.org/10.5194/egusphere-egu25-19254, 2025.
How to cite: Dideriksen, A. K. and the DISCO-2 team: DISCO-2: A student driven CubeSat mission for arctic research, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19558, https://doi.org/10.5194/egusphere-egu25-19558, 2025.
We are developing a new regional coupled ocean-atmosphere-wave model to study the air-sea interaction during intense meteo-marine events such as mesoscale cyclones and tropical-like cyclones. The coupled model is based on the following open-source community model components: (1) an ocean component with the SHYFEM finite element coastal ocean model, (2) a wave component with the unstructured WW3 spectral wave model, (3) an atmospheric component with the Weather Research and Forecasting model (WRF). The wave and the ocean components are hard-coupled and run on the same triangular grid. The resulting ocean-wave and atmosphere components are coupled through the Earth System Modelling Framework library (ESMF), an integrated coupling framework which leads to very clean, abstract and efficient coupled models. With this instrument we study the interaction of tropical cyclone-like vortices with the sea. We show with simplified experiments how this feedback affects the trajectories and the intensity of the vortex as well as the sea-surface temperature and the ocean circulations. We show our model scales well compared to the baseline (uncoupled) runs of the single components. It can be thus applied to large scale configurations with high resolution. We focus on the October 29, 2018 storm event called Vaja, a very severe storm that affected Northern Italy and the Adriatic Sea.
How to cite: Arpaia, L., Bajo, M., Ferrarin, C., and Umgiesser, G.: A regional coupled ocean-atmosphere-wave model (SHYFEM-WRF-WW3) for intense meteo-marine events in the Mediterranean Sea, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19199, https://doi.org/10.5194/egusphere-egu25-19199, 2025.
Interactions of sea surface waves and ocean circulation are traditionally modeled using simplified parameterizations, often based on global ocean data. More refined estimates of wave-ocean interactions on hydrodynamics can be achieved through coupled models with both wave and ocean components. When moving from implicit parameterizations to explicit formulations, reevaluation of the parameterizations governing momentum and energy transfer as well as vertical mixing and turbulence is inevitable. This is particularly important in coastal waters, where the scale of wave-ocean interactions differs from that of the open ocean.
We consider the impacts of surface waves in ocean mixing in fetch-limited regions using an offline coupled WAVEWATCH III–NEMO setup for the Baltic Sea. We find that an optimized sea surface roughness parameterization, based on WAVEWATCH III data, reduces sea surface roughness under high wind conditions compared to the default parameterization in the ocean model’s GLS turbulent closure scheme. When combined with wave-modified ocean-side stress, the optimized parameterization leads to improved predictions of mixed layer depth and sea surface height compared to a stand-alone ocean model.
How to cite: Tuomi, L., Haapaniemi, V., and Kanarik, H.: Parameterizing sea surface wave impacts on ocean mixing in fetch-limited regions , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12163, https://doi.org/10.5194/egusphere-egu25-12163, 2025.
