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, V_west, based on daily GHRSST data (0.01°×0.01°). The results reveal that V_west 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, V_west=11.99 cm s⁻¹) and during November 2022, La Niña event (V_west=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.

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.

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.