This study investigates the integration of seawater temperature data acquired through in-situ and remote sensing methods, aiming to enhance the accuracy of hydrodynamic models. Our focus is on a shallow bay influenced by semidiurnal tides, where continuous thermal discharges from a coastal power plant significantly impact the local temperature field. The investigation addresses the model's uncertainty in capturing the variability of thermal effluents, particularly regarding the input descriptions for the discharge rate (Q) and excess temperature (ΔT) added to the ambient waters. These parameters display seasonal variations that reflect the energy consumption trends of the local population, introducing complexity into seawater temperature modeling. We aim to assess the effectiveness of using different data types in two key application areas: (A) generating better initial conditions through data assimilation with the Ensemble Kalman Filter (EnKF) technique, and (B) automating the calibration of the model parameters for the description of the thermal discharge. To explore these applications, we conduct a twin experiment that replicates the bay's real-world conditions, allowing for a comprehensive evaluation of the impact of integrating temperature data of varying resolutions on the assimilation and calibration processes. Our goal is to determine the most effective spatiotemporal scales for these applications, and to provide recommendations for modeling approaches in similar tidal environments.

How to cite: Alsulaiman, N., Van Reeuwijk, M., and Piggott, M.: Applications of Data Assimilation and Parameter Calibration with Multi-Resolution Measurements of Seawater Temperature for Hydrodynamic Modeling of Shallow, Tidal Environments, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4085, https://doi.org/10.5194/egusphere-egu24-4085, 2024.

How to cite: Calo, L. G., Bennis, A.-C., Boutet, M., and Dias, F.: Τοwards a unified mοdelling οf wave-current-turbulence interactiοns in three dimensiοns: applicatiοn tο Alderney Race (France) and Gregοry Sound (Ιreland) , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9107, https://doi.org/10.5194/egusphere-egu24-9107, 2024.

Coastal regions are dynamic environments influenced by various atmospheric and oceanic processes. Understanding the complex interplay of these forces is crucial for coastal management, navigation, and impact assessments. This becomes especially crucial when investigating climatological scale dynamics.

In this study, two state-of-the-art third-generation wave models, WAM-Cycle 6 (Wave Action Model) and SWAN 41.45 (Simulating Waves Nearshore – Version 41.45) are utilized for numerical wave projection. The methodology involves nested modeling approach by configuring SWAN within WAM to simulate waves at finer resolution near the Irish coast. This setup involves WAM operating on a coarser grid (1.0 degree), an intermediate WAM grid with a resolution of 0.5 degree, and SWAN running on a finer grid (0.025 degree). Wind forcing (10 m wind speed) from climate reanalysis produced by ECMWF (ERA5) is used to drive the wave model. A comparison with wave buoys at different locations around Ireland showed that models agreed on the significant wave height with bias and RMSE differing at most 0.6m.

Statistical techniques are utilized to connect the Max Planck Institute Earth System Model to ERA5 wind data, which is employed as forcing for the wave models to predict waves on climatological scales. The current model setup not only focuses on the present wave conditions but extends to provide future predictions and projections utilizing input data from climate models. By combining the insights from the present with the predictions and projections for the future, the current study aims to provide valuable information for decision-makers in the near and long-term future.

How to cite: Kalayil Uthaman, A., Dabrowski, T., McCarthy, G., Brune, S., and Düsterhus, A.: Wave Climate Analysis near the Irish Coast: SWAN-WAM Modeling from Present to the Future., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9111, https://doi.org/10.5194/egusphere-egu24-9111, 2024.

The response of a coastal ocean model, simulating a typical Eastern Boundary system, to downwelling-favorable winds with and without the presence of a submarine canyon is studied. Three contrasting bathymetric configurations, considering different slopes and depth shelves, are evaluated. Experiments without a submarine canyon represent the well-known downwelling circulation and cross-shore structure with a downwelling front and the development of frontal instabilities generating density anomalies from the bottom up to 50 meters. The presence of the submarine canyon drives important changes in cross-shore flows, with opposing velocities on either side of the canyon. Onshore (offshore) and downward (upward) velocities develop in the upstream side of the canyon in the time-dependent and advective phases. Instabilities developed and are modified principally downstream of the canyon. Overall, the net impact of the canyon is to enhance offshore and downward transport into the canyon. However, particle tracking experiments reveal that particles can become trapped inside the canyon in an anticyclonic circulation when the particles pass the canyon over the continental slope. This particles stay inside the canyon up to 15 days.

How to cite: Saldías, G., Figueroa, P., and Allen, S.: The influence of a submarine canyon on the wind-driven downwelling circulation over the continental shelf, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12829, https://doi.org/10.5194/egusphere-egu24-12829, 2024.

Slow and long-term variations of sea surface temperature anomalies have been interpreted as a red-noise response of the ocean surface mixed layer to fast and random atmospheric perturbations. How fast the atmospheric noise is damped depends on the mixed layer depth.

In this contribution we provide first evidence that lakes are integrators of noisy atmospheric variability just like oceans are. Based on a stochastic approach inspired by the stochastic climate models theory by the 2021 Nobel Physics laureate Hasselmann, we determine estimates of surface mixed layer depth from satellite measurements of Lake Surface Water Temperature (LSWT). The proposed approach is showcased for Lake Garda, Italy. We demonstrate that LSWT anomalies have a red noise spectrum resulting from the integration of higher frequency atmospheric forcing. By connecting the decorrelation time scale of LSWT anomalies to net heat fluxes, we obtain a spatially varying estimate of mixed layer depth. The basin-scale variability of our estimate is consistent with in-situ measurements and connects to the dominant modes of LSWT and chlorophyll-a concentrations obtained via empirical orthogonal functions. We thus show that (i) remotely-sensed quantities also carry information on the relevant spatial and temporal scales of mixed-layer processes and (ii) there is a limit to the persistence, hence the predictability, of the anomalies of LSWT, which poses a physical constraint to temporal gap-filling procedures.

The lessons learnt from ocean modelling is that such first-order picture necessarily overlooks finer scale dynamics, e.g. the effect of intense currents advecting water temperature vertically and horizontally, seasonal modulations and higher order modes of variability, which can be well described by more complex deterministic models. For such a reason, applications to spatial scales different than single points or small portions of the ocean are not common in marine literature. That kind of dynamics also affect lakes surface mixed layer, where spatial and temporal scales of thermal inertia shrink. Our study demonstrates that such a stochastic approach, rather classical in ocean literature, can be applied to the entire surface of enclosed basin and provides useful insights on the thermal and ecological heterogeneity beneath surface.

How to cite: Amadori, M., Bresciani, M., Giardino, C., and Dijkstra, H. A.: Lakes act as slow integrators of atmospheric disturbance like oceans: Evidence from a deep perialpline lake, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17790, https://doi.org/10.5194/egusphere-egu24-17790, 2024.

The inference of coastal ocean dynamics from consecutive remote sensing images plays a central role in a diverse range of domains such as marine conservation, spatial planning, as well as flood risk. We present a methodology for systematically identifying spatially overlapping image pairs in coastal regions from the PlanetScope archive, with minute-scale time lags and the potential for velocity field inference using classical algorithms. This ability is demonstrated through the novel estimation of submesoscale eddies from PlanetScope image pairs across a range of contexts. These include sea ice floes in the Siberian Sea of Okhotsk, a cyanobacterial bloom in the Baltic Sea, and suspended sediment in the Port of Al-Fao located in the Arabian Gulf. Additionally, comparison of the latter with coinciding velocity fields from a Delft3D model shows good quantitative agreement in regions with high suspended sediment concentration. We successfully develop a workflow pipeline for identifying and processing image pairs from these opportunistic overlaps, unlocking a new large-scale data source of coastal ocean surface velocities to be used alongside modelling frameworks. 

How to cite: Tlhomole, J., Piggott, M., and Hughes, G.: Measuring Marine Hydrodynamics from Space Using Planet Satellite Imagery , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19224, https://doi.org/10.5194/egusphere-egu24-19224, 2024.

This study presents an analysis of the impacts of changes in bottom depth along the Guadalquivir Estuary on tidal dynamics. A realistic non-linear 1D numerical model, incorporating alterations in both breadth and bottom depth, was employed to investigate the associated effects.The 1D numerical model consists of a hydrodynamical model and a transport and dispersion module,which successfully reproduce the hydrodynamics of the saline intrusion from the continental shelf.The results show a significant amplification of the M2 tidal wave towards theheadof the Estuary,which seems to be caused bythe gradual bottom deepening caused by multiple dredging activities. The Estuary exhibits a pronounced tendency towards resonance, which is further enhanced by this deepening which reduces bottom friction and produces a smaller decrease in tidal wave amplitude as it propagates through the Estuary. The alterations in depth, particularly in breadth, along the Estuary play a crucial role in determining the magnitude of the resonant response of the M2 tidal wave.Modelsimulations demonstrate how changes in the geometric configuration of the channel, as well as the river waterwithdraw different agricultural activities, lead to significant alterations in the salt wedgedynamics. These changes in the tidal and associated salt exchange dynamics may also have a significant impact in thebiogeochemical exchanges between the river and the continental shelf, with potential harmful effect on the primary productionin the mouth of the estuary and adjacent coastal areas.

How to cite: Sirviente Alonso, S., Gomiz Pascual, J. J., Bolado Penagos, M., and Bruno Mejías, M.: Analysis of Antropogenic effects on the tidal dynamics and salt transport along the Guadalquivir river estuary., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-865, https://doi.org/10.5194/egusphere-egu24-865, 2024.

Physical, chemical, and biological processes in fjord ecosystems are inherently intertwined and their interactions cultivate environments ideal for primary production and ecological diversity. Yet, due to the vast range of space and time scales important in fjords, defining specific inter-process outcomes, such as conditions that trigger harmful algal blooms (HABs), has proven to be a challenging task. To identify repeatable inter-process patterns this study will focus on time scales over which plankton are known to depend on and vary, such as the change from day to night, or the diurnal cycle. Therefore, in December 2021, a field experiment was conducted in a fjord of northern Chilean Patagonia (41.6º S) to capture the interaction of physical, chemical, and biological processes for a complete diurnal cycle (24 h). The measurements collected included hydrographic, atmospheric, tidal, and nutrient data as well as phytoplankton and zooplankton samples to elucidate how specifically these processes interact. Results detected thin, near-surface phytoplankton and zooplankton layers during the daytime, located just below a layer of fresh water, acting as a barrier. During the night the thin layers were dissipated and dispersed. Predator-prey interactions were one of the factors contributing to phytoplankton dissipation at nighttime, due to the diel vertical migration of macrozooplankton species. The physical measurements showed reduced stratification and enhanced vertical mixing homogenizing the upper layers of the water column at night, which is thought to be enhanced by the presence of swimming macrozooplankton. Diatoms dominated the phytoplankton composition, but HABs species were observed, showing changes in abundance and species composition from day to nighttime. This study reinforces the need to carry out interdisciplinary experiments to understand how physical, biological, and chemical processes in fjords interact, to forecast and mitigate the effects of water quality issues such as harmful algal blooms.

How to cite: Pérez-Santos, I., A. Díaz, P., Ross, L., Riquelme-Bugueño, R., Lara, C., Barrera, F., Díaz-Astudillo, M., Muñoz, R., Ladaeta, M., Linford, P., Schwerter, C., Arenas-Uribe, S., Navarro, P., Guido Mancilla-Gutiérrez, G. M.-G., Jorquera, E., and Saldías, G. S.: Physical, biological, and chemical inter-processes in fjords., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6193, https://doi.org/10.5194/egusphere-egu24-6193, 2024.

The large presence of human infrastructure, protected natural environments, cultural heritage and major economic activities makes the coast one of the most vulnerable areas to climate change-related problems such as sea level rise and an increasing number of extreme events. Storm surges are the main cause of flooding and coastal erosion due to the combined effects of waves and currents that resuspend and transport sediments. In addition to the classic "gray" solutions, including engineered structures such as seawalls and groins, nature-based solutions have emerged in the last decade, based on the idea of finding solutions that are both effective and environmentally sustainable. It is well known that seagrass meadows can provide critical ecosystem services. Among them, coastal protection is one of the most important. The aim of this work is to investigate the effects of seagrass meadows on physical ocean variables relevant for sediment transport and sea level using a digital twin of the ocean. The seagrass is implemented in a three-dimensional unstructured grid ocean model (SHYFEM-MPI) as a form drag in the momentum equations, considering the flexibility of the plants. The implementation was verified with idealized test cases and three focus areas were selected along the Italian coast. The three areas are the Venice lagoon, the Emilia-Romagna coast (northern Adriatic Sea) and the Civitavecchia coast (Tyrrhenian Sea) and differ in morphology and seagrass species (Zostera marina, Posidonia oceanica). These areas are representative of a wide range of coastal environments. Interestingly, the results show different behavior depending on the geomorphology of the area. The lagoon environment, when exposed to extreme storm surge events, shows an alternating pattern of sea level variation with a reduction that can reach 5-10%, while in the other focus area the effect of seagrass on sea level is negligible. In all three areas, seagrass is very effective in reducing bottom current velocity by up to 50-60%, suggesting a possible important role against coastal erosion.

How to cite: Alessandri, J., Federico, I., Biocca, N., Causio, S., Bonamano, S., Piermattei, V., Mentaschi, L., Coppini, G., Marcelli, M., Valentini, A., and Pinardi, N.: Investigating Seagrass as a Nature-Based Solution for Coastal Protection: toward a Digital Twin Modelling Framework, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11402, https://doi.org/10.5194/egusphere-egu24-11402, 2024.

Low oxygen conditions increasingly threaten marine ecosystems by reducing habitat and biodiversity. Low oxygen also influences biogeochemical processes in water and sediment, greenhouse gas emissions, and contributes to toxic algae blooms by increased phosphorus recycling. As a result, this can have significant impact on regional economies, affecting thousands of jobs and billions of dollars. Deoxygenation of marine environments has been linked to human activities since the 1950s. Low-oxygen zones exist in the open ocean, over continental shelves, and in coastal seas, and are expected to expand especially in the coastal marine space in the future due to warming and increasing nutrient pollution.

Despite these on-going threats, current conservation measures do not effectively address the impacts of reduced oxygen or feature large time lags in implementation or projected outcomes.

While small-scale artificial oxygen injection (AO) has been used in lakes and marine aquaculture, larger-scale efforts are rare. The use of marine renewable energy for green hydrogen production presents a new, exciting opportunity for sea-based mitigation through anthropogenic oxygenation. The oxygen produced during hydrogen generation (e.g., 0.5 GW electrolyzer: ~210 t H₂ d^-1; ~1700 t O₂ d^-1) could be used to mitigate anoxia, restore benthic habitat, reduce phosphorus loading, and suppress algal blooms. Constant AO could also help combat increasing hypoxia caused by circulation shifts, decreased deep mixing in autumn and winter and climate change.

AO technologies that can scale up to marine applications are now common in USA reservoirs. The largest is 350 tonnes O₂/d. Although there is evident potential, AO for the marine environment has received little attention, likely due to the current cost of oxygen and/or lack of infrastructure and awareness. Here, we want to present the BOxHy project, funded by the BSAP fund; this innovative project focuses on preparing a pilot study site for AO in the Baltic Sea environment with the perspective of upscaling the technology and science to basin wide scales. Offshore wind farms are planned in the Baltic Sea as the decarbonization of energy systems is advancing. Cost-efficient green hydrogen production strengthens the bankability of the concept, combining CO₂ reductions through the hydrogen economy and a decrease in anoxia. Coupled to the production of offshore hydrogen, the injection of the electrolysis by-product oxygen is a novel innovative technique that could be adapted to other anoxia-prone coastal environments with similar environmental challenges after successful research and demonstration, closing major knowledge gaps and exploring the risks for unintended consequences.

With the BOxHy project we contribute to challenges 1 and 2 and 4 of the UN Decade of Ocean Science and Sustainable Development. Given the current threats to coastal marine ecosystems, exploring AO as a mitigation measure directly aligns with the principles of "prevention of harm” and the “precautionary approach” outlined in the “Declaration of Ethical Principles in Relation to Climate Change”.

How to cite: Handmann, P., Walve, J., Haide, S., Austin, D., and Bryant, L.: The BOxHy Project – Preparing a Pilot Site Study to Remediate Low Oxygen Conditions in Coastal Seas, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18024, https://doi.org/10.5194/egusphere-egu24-18024, 2024.

Climate change will have far-reaching consequences on the environment, primary production, the economy, and society as a whole. Changes in hydrodynamic patterns pose a significant threat to low-lying coastal areas that often present high economic and biological value. The Ria de Vigo is part of the Rias Baixas, which are located in the NW of the Iberian Peninsula. This system, as well as the rest of the Galician coast, is an area of high primary production that is vulnerable to changes in hydrodynamics induced by climate change. These changes could have a detrimental effect on the system and the local communities as they strongly depend on the income brought by aquaculture, and therefore this study aims to understand how climate change will affect the thermohaline properties in the Ria de Vigo.

To better understand these impacts, a hydrodynamic model of the Rias Baixas was implemented to analyse the effect of climate change on the Ria de Vigo’s thermohaline properties. The methodology followed consisted of the application of the Delft3D three-dimensional numerical model in the Rias Baixas and the adjacent ocean with variables obtained from global and regional climate models, in future scenarios provided by CMIP6. This was done for the summer season and for two scenarios, the present-day and CMIP6’s SSP5-8.5 future scenario.

The results show that the water temperature in the Ria will increase in the future due to climate change, and it tended to be higher at the surface and lower at the bottom due to the intrusion of oceanic water from the Eastern North Atlantic Central Water (ENAWC). The salinity is expected to decrease and will be highest in the bottom layer near the connection with the ocean, and lowest in the surface layers and near the river, in the latter case, due to freshwater discharges. The density presented similar patterns, also decreasing in the future, and showing the expected stratification associated with the upwelling season.

How to cite: Ribeiro, C., Sousa, M. C., Ribeiro, A., Pereira, H., Álvarez, I., and Dias, J. M.:  Impact of Climate Change on the Thermohaline Properties in the Ria de Vigo (NW Iberian Peninsula) , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11975, https://doi.org/10.5194/egusphere-egu24-11975, 2024.

Coastal water quality in Hong Kong faces challenges from nutrient pollution, contaminant discharge, algal blooms, land-derived sedimentation, and climate change effects. To assess water quality in coastal regions, researchers have utilized varying in-situ monitoring data and remote sensing techniques to quantitatively estimate chlorophyll-a concentrations. Despite these efforts, there remains a lack of fine-scale characterization of the spatial and temporal patterns of chlorophyll-a in Hong Kong’s coastal waters, due to the limited resolutions and cloudy covers. Our study seeks to bridge this gap by fusing multisource satellite observations. Existing spatiotemporal image fusion models are primarily designed for land surface reflectance. In this study, we propose using Generative Adversarial Networks (GANs)-based deep learning techniques to improve the fusion of multisource satellite images specifically for watercolor remote sensing. A spatiotemporal fusion deep learning framework based on GANs has been developed to generate daily surface reflectance and temperature at 300 m spatial resolution using data from Sentinel-3 and Himawari-8 satellites. Furthermore, we have devised a random forest-based chlorophyll-a concentration estimation model  that employs the blended high-resolution data derived from multi-source satellite observations and extensive in-situ monitoring data obtained from 76 marine water quality monitoring stations administered by the Hong Kong Environmental Protection Department (HKEPD). These independent in-situ monitoring datasets also serve as valuable resources for evaluating the performance of satellite-derived chlorophyll-a concentrations. Consequently, we conducted a fine-scale mapping of chlorophyll-a distribution in Hong Kong's coastal waters to analyze spatiotemporal characterization of water quality. This approach holds promise for real-time, fine-scale water quality monitoring using high-frequency satellite observations in the future.

How to cite: Jiang, X. and Huang, B.: Fine-scale spatiotemporal characterization of chlorophyll-a in Hong Kong’s coastal waters through the fusion of multisource satellite imagery , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5192, https://doi.org/10.5194/egusphere-egu24-5192, 2024.

Coastal regions are confronted with an escalating threat posed by the intensification of wave-induced erosion through rising sea levels and increased storm intensities, underscoring the critical need for innovative solutions to ensure effective coastal protection. Floating breakwaters as a possible optimal solution play a crucial role in land reclamation by facilitating the creation of recreational spaces, such as promenades, and enhancing aesthetical landscapes through tree plantations. Their significance lies in their ease of maintenance and the ability to be swiftly removed during stormy seasons, providing adaptable and sustainable solutions for coastal development. This study explores the potential of the Triply Periodic Minimal Surface (TPMS) floating porous breakwaters as an optimal approach, due to their intricate geometry and structural integrity which enhances the dissipation and dispersion of wave energy, to mitigate the impact of waves on vulnerable shorelines. TPMS structures offer a sustainable solution by being printable with re-use materials, promoting recycling, and aligning with the principles of a circular economy, thus contributing to eco-friendly coastal protection. Conducted in a controlled environment within a small-scale wave flume, our comprehensive laboratory-scale experiment focuses on assessing the performance of various TPMS structures under diverse conditions of wave and current generation. Systematically varying parameters, including TPMS architecture, unit cell size, relative density of porous structures, buoyancy depth (draft), and altering wave parameters and current rates, aims to elucidate the influence of these variables on the breakwater’s ability to dissipate, reflect, and transmit wave energy. The experiments involved exposure to various regular wave conditions generated by a plunger-type wavemaker, combined with different constant current rates to mimic realistic coastal scenarios. The controlled environment enables a nuanced understanding of how TPMS floating breakwaters respond to diverse wave dynamics, providing valuable insights into optimal design parameters. The performance evaluation is conducted using three widely known parameters: reflection coefficient (C_r), transmission coefficient (C_t), and dissipation coefficient (C_d) as they quantify the efficiency of wave energy absorption, transmission through the structure, and dissipation, providing key insights into the breakwater's ability to mitigate wave impact and protect coastal areas. To determine these parameters, wave separation analysis methods have been employed, including the method developed by Suh et al (2001), which considers the presence of simultaneous waves and currents, and the method developed by Zelt and Skjelbreia (1993), utilizing an arbitrary number of wave gauges. Anticipating that the outcomes of this study will contribute to the development of a novel coastal protection solution, we strive to strike a balance between environmental sustainability and effective wave attenuation. Furthermore, our research opens avenues for integrating optimal floating breakwaters with wave energy conversion systems, enhancing functionality and addressing both environmental and energy challenges associated with coastal protection.

How to cite: Hasanabadi, A., Stolle, J., Pham Van Bang, D., and Hammouti, A.: Coastal erosion mitigation by the use of an optimized 3D printed Triply Periodic Minimal Surface Floating Porous Breakwater, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10385, https://doi.org/10.5194/egusphere-egu24-10385, 2024.

Previous research indicates that the survival rate of Claviaster libycus following mass extinction events surpasses that of regular echinoids. This investigation seeks to assess the flow dynamics and scour patterns resulting from the distinctive distorted morphology of Claviaster libycus using numerical modeling. In addition, this study examines the localized scour that occurs around tsunami stones.

The numerical model employed in this investigation, Splash3D, has been adapted from the open-source code Truchas, originally developed by the National Laboratory of the United States. Splash3D is designed for solving the three-dimensional, incompressible Navier-Stokes equations. The Volume of Fluid Method (VOF) is utilized to characterize the kinematics of the water and sand surfaces.

As Claviaster libycus partially submerges in the sand, the rheological behavior of the bottom sand is characterized using the Discontinuous Bi-Viscous Model (DBM), derived from the conventional Bingham Model (BM). Unlike the BM model, the DBM model employs the yield strain rate instead of the yield stress to differentiate the plug from the liquefied zone. In the Plug zone, high viscosity signifies solid characteristics, with the plug-zone viscosity significantly surpassing that of the liquified zone. The liquified zones represent sand disturbed by local currents around irregular echinoids, while the plug zones depict undisturbed sand. The yield strain rate dictates the stiffness of the bottom sand, and the DBM model is employed to describe local scour around obstacles.

According to numerical simulations and experimental results, when the gonopore of Claviaster libycus is directed downstream, it can reduce the generation of horseshoe vortices. Therefore, compared to the gonopore pointing upstream, having the gonopore directed downstream can decrease the local scour around the sea urchin. Furthermore, in the event of a tsunami, intense local scouring occurs around large stones, leading to structural instability in the rock formations. Due to the tsunami's characteristic long wavelength, as the powerful water flow passes through, it eventually transports the large stones to the shoreline, forming what is known as tsunami stones. Detailed analysis results are presented at the conference.

How to cite: Wu, T.-R., Lin, P.-J., Lin, J.-P., Chuang, M.-H., Huang, Y.-X., and Chu, J.-J.: The Enigma of Claviaster libycus Survival Rate: Numerical Simulations Revealing its Superiority Post-Mass Extinction, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14844, https://doi.org/10.5194/egusphere-egu24-14844, 2024.

The Bedford Basin is a a 70 m deep, seasonally stratified and hypoxic semi-enclosed fjord on the West Atlantic coast (Nova Scotia, Canada). The basin is connected to the Atlantic Ocean (Scotian Shelf) via a narrow 20 m deep sill that restricts exchange and mixing of surface and bottom waters. Bedford Basin is located in an urban setting (Halifax) and receives considerable wastewater input. The Basin has benefitted from a weekly multidisiciplinary time-series of physical, chemical and microbiological data over several decades. Over the past decade, the intensity of hypoxia has increased due to warmer winters and reduced convective renewal of the deeper water. The presentation will highlight understanding of physical-microbiological-chemical interactions, and sediment-water exchanges, that affect the concentration and speciation of nitrogen and iodine species in relation to variable levels of oxygen. A focus will be on interannual and short-term variability in production of nitrous oxide and iodide in relation to variations in oxygen, microbial diversity and sediment-water exchange. The potential of coastal basins to act as living laboratories for  studying complex, redox-dependent processes through comprehensive, multidisciplinary, time-series study will be demonstrated. The closely related potential of urban fjords to act as testbeds for evaluation of emerging approaches to the mitigation of coastal hypoxia will be emphasized.

How to cite: Wallace, D., Shi, Q., LaRoche, J., Segura Guzman, M., Rakshit, S., Algar, C., Pascal, L., and Chaillou, G.: Use of an urban fjord as a living laboratory for understanding impacts of hypoxia on nitrous oxide production and iodine cycling, and for testing of mitigation strategies., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20248, https://doi.org/10.5194/egusphere-egu24-20248, 2024.

Marine debris can be classified as either land or marine origin, with more than 8 million tons of land-based debris entering the ocean globally each year. Land-based debris enters estuaries and coasts in large quantities through river systems, which may cause water pollution, damage to aquatic and coastal ecosystems, and marine safety accidents. We applied an integrated approach linking watersheds, rivers, estuaries and oceans to investigate the transport processes of land-based debris into an estuarine ecosystem, and assessed their risk to sensitive resources in South Korea, a country with a monsoonal climate.

Based on the time-series trash data collected at major dams, a model was developed to estimate the amount of land-based debris generated in the watershed. We found that land cover, hydrological characteristics, and socioeconomic factors of the watershed played an important role in the generation of land-based debris. Most of the land-based debris is vegetation wastes and plastics, which tends to be discharged through rivers during the monsoon season when rainfall intensity is high. A particle transport modeling was used to estimate the spread of land-based debris through rivers to the Geum-River estuarine system. The results showed a good agreement with the distribution of marine debris monitoring data. The Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST)-Habitat Risk Assessment model was used to assess marine debris risk to sensitive resources in the estuarine ecosystems. The spatially explicit results of risk assessment provide key information to support marine debris management policies at the national and regional levels.

Acknowledge: This research was a part of the project titled “Development of Smart Technology to Support the Collection and Management of Marine Debris” (grant number 20200594), funded by the Ministry of Ocean and Fisheries (Korea), supported by Korea Institute of Marine Science & Technology Promotion. Also, this research was a part of the project titled “Establishing a smart response platform for marine accidents” (grant number 20220463), funded by the Korea Coast Guard, supported by Korea Institute of Marine Science & Technology Promotion. The project was implemented by the Korea Environment Institute (project 2024-007(R), project 2024-008(R)).

How to cite: Kim, C.-K., kim, G. S., Kim, J., Hong, H., Bang, K.-Y., and Lee, S.-H.: Estimating the Distribution of Land-based Marine Debris and Risk Assessment to Sensitive Resources in an Estuarine Ecosystems with high river discharge in South Korea, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22314, https://doi.org/10.5194/egusphere-egu24-22314, 2024.