OS2.2 | Oceanography at coastal scales. modelling, coupling, observations and applications
EDI
Oceanography at coastal scales. modelling, coupling, observations and applications
Convener: Agustín Sánchez-Arcilla | Co-conveners: Sandro Carniel, Joanna Staneva, Manuel Espino Infantes, Davide Bonaldo
Orals
| Tue, 25 Apr, 10:45–12:30 (CEST), 14:00–18:00 (CEST)
 
Room 1.61/62
Posters on site
| Attendance Tue, 25 Apr, 08:30–10:15 (CEST)
 
Hall X5
Posters virtual
| Attendance Tue, 25 Apr, 08:30–10:15 (CEST)
 
vHall CR/OS
Orals |
Tue, 10:45
Tue, 08:30
Tue, 08:30
Coastal oceanographic processes present important differences with deep water oceanography, resulting in higher prediction errors, where bottom topography in shallow domains exerts a strong control on wave/current/turbulence fields. These fields are modified by many additional factors that include stratification, land boundary conditions and interactions with coastal infrastructure. The strong non-linear interactions (breaking waves, nearshore circulation), the choice of numerical strategy (nested meshes, finite-elements) or the modulations in restricted domains (suspended sediment clouds, vegetation filtering) may also play a critical role in the predictive quality. Coastal observations (in-situ and remote) are therefore necessary to drive and calibrate numerical models, where the advent of new satellite capabilities (e.g. Sentinel resolution and sensors) and new modelling advances (e.g. couplings or unstructured grids) together with enhanced Coastal Observatories, are leading to a qualitative advance of coastal oceanography. Coastal issues become more relevant in a framework of changing climate, since transitional areas are more strongly impacted by climate (e.g. changing domains due to sea-level rise) and therefore more in need of new approaches that include Natural based Solutions.
Because of these reasons, it is timely to discuss recent advances in: a) coastal coupled hydro-morpho-eco modelling at different scales; b) aggregation of in-situ/satellite/numerical data from different sources; c) knowledge-based coastal applications, including the assessment of Nature-based interventions; d) uncertainties in coastal decision-making, framed by an ethical approach and supported by quantitative information. Building upon these challenges, we invite presentations on coastal modelling and coupling, local assimilation, boundary effects or operational coastal predictions with/out interactions with Nature based or traditional interventions. Contributions exploring the potential and currently open issues of non-linear response functions, support from artificial intelligence and big data or uncertainty assessments for coastal applications are also welcome. These and related coastal topics should conform a fruitful session for discussing applications of coastal science to conventional and nature-based interventions under climate change. Please state if you would be interested in submitting your presentation to a peer reviewed special issue in Ocean Science.

Orals: Tue, 25 Apr | Room 1.61/62

Chairperson: Sandro Carniel
10:45–10:50
10:50–11:00
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EGU23-6352
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OS2.2
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On-site presentation
Ernesto Napolitano, Roberto Iacono, Adriana Carillo, Maria Vittoria Struglia, Massimiliano Palma, and Gianmaria Sannino

In recent years, much work has been devoted to the characterization of the long-term variability of the circulation in the North Ionian Sea, which in the last three decades has been dominated by the so-called Bimodal Oscillation (BIOS). Here we further investigate this topic, both in the context of present climate and in a future scenario, analyzing the results of simulations made with the MED16 model. MED16 is a new, tide-including implementation of the MITgcm oceanic model, which covers the Mediterranean-Black Sea system with a horizontal resolution of 1/16° that is further increased at the Gibraltar and Turkish Straits. Three simulations have been performed: a hindcast run (1980-2010), used to validate the model; a historical run (1980-2005), which provides initial conditions for the scenario simulation; and a future climate (2006-2100) simulation, using atmospheric forcing under the Rcp8.5 emission scenario.

The hindcast run shows a variability of the surface circulation that is in good agreement with the observations, and indicates that during the period 1980–2010 the surface variability in the north Ionian is poorly correlated to that of the wind stress curl. The inversions of the circulation (switch from cyclonic to anticyclonic) that have been observed, and are well reproduced by the model, are apparently controlled by the Eastern Mediterranean Transient phenomenon: the huge volume of dense water produced by the Aegean Sea is the only forcing that may explain the strong anticyclonic surface circulation during the period 1993-1998. After that a prolonged cyclonic phase sets in, which weakens only during the 2004-2006 period.

On the other hand, the climatic projection over the next century shows a prevalence of the cyclonic circulation, well correlated to the prevalent positive wind stress curl, and  three clear inversions in which both the wind stress curl and the anomalies of dense water of Adriatic and Aegean origin appear to play a role. The simulation shows that the variability in the region is also affected by the strengthening and weakening of the cyclonic cell itself, which can modulate the ingression of the Atlantic Ionian Stream from the Sicily Strait and its path. This indicates that the multidecadal variability of the north Ionian circulation can play an important role in the control of the transport of the surface salinity in the Eastern Mediterranean Sea, even in extreme climatic conditions.

How to cite: Napolitano, E., Iacono, R., Carillo, A., Struglia, M. V., Palma, M., and Sannino, G.: Present and future long-term variability of the north Ionian surface circulation, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6352, https://doi.org/10.5194/egusphere-egu23-6352, 2023.

11:00–11:10
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EGU23-59
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OS2.2
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On-site presentation
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Sung Yong Kim and Eun Ae Lee

Upcoming satellite missions will observe the sea surface height (SSH) fields at a very high spatial resolution, which has generated an urgent need to understand better how well geostrophy can represent the ocean current field at finer scales, particularly in coastal regions characterized by complex flow geometry. We conduct statistical and spectral analyses of high-resolution surface currents and SSHs off the Oregon coast to examine the relative contribution of geostrophy and ageostrophy in coastal ocean currents. We analyze forward numerical simulations based primarily on a regional ocean model (ROMS) and use regional observations of high-frequency radar (HFR)-derived surface currents and altimeter-derived geostrophic currents and a subset of global domain numerical simulations (MITgcm) as secondary resources. Regional submesoscale ageostrophic currents account for up to 50% of the total variance and are primarily associated with near-inertial currents and internal tides. Geostrophy becomes dominant at time scales longer than 3 to 10 days and at spatial scales longer than 50 km, and is dependent on the depth and distance from the coast in the cross-shore direction. Ageostrophy dominates in the near-inertial and super-inertial frequency bands, which correspond to near-inertial motions (Coriolis force dominates) and high-frequency internal waves/tides (pressure gradient dominates), respectively. Because of ageostrophy, it may not be possible to estimate submesoscale currents from SSHs obtained from upcoming satellite missions using the geostrophic relationship. Thus, other concurrent high-resolution in-situ observations such as HFR-derived surface currents, together with data assimilation techniques, should be used for constructive data integration to resolve submesoscale currents.

How to cite: Kim, S. Y. and Lee, E. A.: A diagnosis of surface currents and sea surface heights in a coastal region, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-59, https://doi.org/10.5194/egusphere-egu23-59, 2023.

11:10–11:20
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EGU23-6004
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OS2.2
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ECS
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On-site presentation
Bo-Kyung Kim and Jin Hwan Hwang

An Oceanic Regional Circulation Model (ORCM) is generally constructed by downscaling the large-scale information of an Oceanic Global Circulation Model (OGCM) through a nesting technique. Since the OGCM has relatively low resolution and so only has large-scale information, ORCM can only be built with large-scale information. Even if the ORCM is run with only large-scale information, small-scale fluctuations can be developed by “stimulating sources” such as the self-interaction of large-scale motions. However, it is not sufficient to generate small-scale fluctuations by itself in a short time, and if other stimulating sources, such as islands, coastlines, and strong advection, are absent, errors can occur (Van Tuyl and Errico, 1989; Pham and Hwang, 2020). Pham and Hwang (2020) suggested a method to introduce artificial small-scale fluctuations for boundary conditions that can reduce errors and generate small-scale features in a short period. This method was applied to the ocean of 330 km  220 km with a resolution of 1 km  1 km, and the accuracy of the applied model was higher than that of the original model. In this study, this small-scale addition method is developed to be applied to the coast smaller than the ocean, and the generated small-scale fluctuations are added in the vertical direction as well.

To construct the artificial small-scale fluctuations, we first need to analyze the regional energy spectrum. A high-resolution ORCM model is built using the OGCM data and used as reference data. The regional energy spectrum is defined in the high-resolution ORCM results, and small signals below a certain wavelength are removed with a low-pass filter using the Discrete Cosine Transform to mimic the low-resolution OGCM data. We then assume that energies cascade monotonically from the large scale. After the energy spectrum is extended from the larger scales to the smaller scales, this spectrum is transformed to realistic values using the Inverse Discrete Cosine Transform. The realistic values with small-scale features are added to the original values with large-scale features, which apply to all vertical layers. When this small-scale addition method is applied to the coast where the strong advection is present, the method does not significantly improve the accuracy, unlike when applied to the ocean. Therefore, in coastal areas where strong advection exists, another method is needed to increase accuracy in a short time.

 

References

Pham, V. S., & Hwang, J. H. (2020). Effects and recovery of small-scale fluctuations in one-way nesting for regional ocean modeling. Ocean Modelling145, 101524.

Van Tuyl, A. H., & Errico, R. M. (1989). Scale interaction and predictability in a mesoscale model. Monthly weather review117(3), 495-517.

 

Acknowledgement

This work was supported by the project entitled “Development of living shoreline technology based on blue carbon science toward climate change adaptation [grant number 20220526]” funded by the Ministry of Oceans and Fisheries (MOF), South Korea.

How to cite: Kim, B.-K. and Hwang, J. H.: A Study on One-way Nesting Technique for Oceanic Regional Circulation Modeling through Small-scale Information Restoration, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6004, https://doi.org/10.5194/egusphere-egu23-6004, 2023.

11:20–11:30
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EGU23-6387
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OS2.2
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On-site presentation
Mirko Orlic, Gordana Beg Paklar, Tomislav Dzoic, Petra Lucic Jelic, Iva Medugorac, Hrvoje Mihanovic, Stipe Muslim, Miroslava Pasaric, Zoran Pasaric, Antonio Stanesic, and Martina Tudor

An experiment has been carried out in the Adriatic Sea, in the framework of the Middle Adriatic Upwelling and Downwelling (MAUD) project. The CTD and ADCP data were collected by the yo-yo and shipborne measurements performed during the cruises whereas the temperature, pressure and dissolved oxygen time series were recorded by the probes deployed at the sea bottom. Additionally, the SST satellite data and the meteorological time series originating from permanent coastal stations were considered. Moreover, the high-resolution, 2-km meteorological (ALADIN) and 2.5-km oceanographic (ROMS) models were used to reproduce and interpret the experimental findings. Analysis of the data has concentrated on the end of May 2017, when a dense water dome was documented by the CTD measurements in the area between the island of Blitvenica (close to the east coast) and the island of Jabuka (in the open sea). Its center was observed at a distance of about 20 km from the coast. The dome left its mark on the sea surface, with the temperature above its center being slightly lower than in the surrounding areas as documented by both in situ and remotely-sensed data. The vmADCP measurements suggested that the surface circulation around the dome was cyclonic. At the time, a decrease of temperature close to the east coast was documented by the bottom probes and satellite images. The meteorological data and modeling results showed that the northern winds prevailed during the May 2017 experiment, suggesting that the open-sea and coastal upwelling occurred at the same time. In order to verify the interpretation, several schematized numerical experiments were conducted. The modelled wind fields were first decomposed into the curl and curl-free components, using the Helmholtz-Hodge decomposition. The components were then used to impose the forcing on the Adriatic model, assuming flat bottom and realistic bathymetry. Schematized simulations revealed that the wind curl was responsible for the offshore rising of pycnocline through Ekman pumping and therefore for the open-sea upwelling. On the other hand, in simulations with the curl-free wind component the pycnocline rose only close to the east coast and thus the coastal upwelling was reproduced.

How to cite: Orlic, M., Beg Paklar, G., Dzoic, T., Lucic Jelic, P., Medugorac, I., Mihanovic, H., Muslim, S., Pasaric, M., Pasaric, Z., Stanesic, A., and Tudor, M.: Open-sea and coastal upwelling in the Adriatic Sea, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6387, https://doi.org/10.5194/egusphere-egu23-6387, 2023.

11:30–11:40
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EGU23-12514
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OS2.2
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Virtual presentation
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Vassilis Kolovoyiannis, Aikaterini Anna Mazioti, Evaggelia Krasakopoulou, Vassilis Zervakis, Eleni Anthi Tragou, Ioannis Mamoutos, Emmanouil Potiris, Stamatis Petalas, Christos Chatzilaou, Kyriaki Mosiou, Harilaos Kontoyiannis, Vasiliki Paraskevopoulou, and Alexandros Athiniotis

The coastal marine ecosystem of Saronikos Gulf, a busy Eastern Mediterranean embayment directly impacted by the greater metropolitan area of Greece’s capital, Athens, is examined through a series of state-of-the-art numerical models that address the hydrodynamics (Delft3D-FLOW), the wave regime (SWAN), the biogeochemistry, and pollution related to species of heavy metals and polyaromatic hydrocarbons (Delft3D-WAQ).

The study so far has focused on calibrating model components and on reproducing the seasonal thermohaline conditions, known circulation patterns and the variability of biogeochemical constituents (chlorophyll-a, nutrients, dissolved and particulate matter) and pollutant concentrations, focusing on the vicinity of inner Saronikos.

The annual cycle ‘Nov 2009 - Oct 2010’ is simulated, forced with atmospheric data from the ERA5 database. Three sets of open boundary conditions data are tested (Mediterranean Sea Physics Reanalysis dataset by Copernicus and two implementations of the ROMS model covering the Aegean and the Eastern Mediterranean respectively), constituting three classes of numerical experiments aiming to optimize model performance. Freshwater discharges from waste treatment facilities and rivers are considered, the latter drawn from the Swedish Meteorological and Hydrological Institute (platform ‘Hypeweb’).

Emphasis has been placed in compiling available information on point sources of pollution from the numerous human activities in the vicinity of the study area. These data are used as forcing in the modelling process.

A comprehensive dataset of field measurements collected monthly by the Hellenic Centre for Marine Research from a network of ten stations, as well as satellite derived SST data, are used for model validation.

This work is carried out within the context of the EMERGE Horizon 2020 project, that develops methodologies to evaluate, control and mitigate the environmental impacts of shipping emissions. For the scope of the project, next steps currently undertaken include the simulation of the Saronikos Gulf status for the year 2018 considering pollutant mass fluxes (a) from shipping emissions as calculated by the Ship Traffic Emission Assessment Model (STEAM) and (b) from atmospheric depositions as calculated from atmospheric modelling, both components from data provided by consortium partners.

 

How to cite: Kolovoyiannis, V., Mazioti, A. A., Krasakopoulou, E., Zervakis, V., Tragou, E. A., Mamoutos, I., Potiris, E., Petalas, S., Chatzilaou, C., Mosiou, K., Kontoyiannis, H., Paraskevopoulou, V., and Athiniotis, A.: Implementation of a modelling system for the investigation of the Saronikos Gulf marine ecosystem (Eastern Mediterranean), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12514, https://doi.org/10.5194/egusphere-egu23-12514, 2023.

11:40–11:50
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EGU23-16918
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OS2.2
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Virtual presentation
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Florian Kokoszka, Baptiste Le Roux, Daniele Iudicone, Fabio Conversano, and Maurizio Ribera D'Alcalà

We analyze 20 years (2001–2020) of temperature and salinity profiles at the LTER–MC coastal station in the Gulf of Naples, Mediterranean Sea. Surface and bottom layers show weak increases of temperature (+0.01°C ± 0.01°C /year and +0.03°C ± 0.02°C /year, 2005–2019); water-columns budgets (heat, freshwater) show pseudo-periodic oscillations every 3 to 5 years, and weak linear trends. Seasonal minimum of salinity occurs 2 months later than the runoff peak, pointing to the importance of horizontal circulation in regulating the inshore–offshore exchanges and the residence time of freshwater. Inter-annual variations of the mixed layer depth (MLD) indicate a shallowing (-1.27m ± 0.38m /year during winter) and a shortened time span of the fully mixed water-column. A visible decadal shift in the external forcings suggests an influence of winterly wind stress in 2010–2019, that prevailed over dominant buoyancy fluxes in 2001–2009. Changes are visible in the large-scale indices of the North Atlantic and Western Mediterranean Oscillations and highlight the role of wind direction, offshore or inshore oriented, in disrupting the stratification driven by freshwater runoff. A Random Forest Regression confirms that role and quantifies the MLD's drivers importance. This allows for a reliable prediction of the stratification using external variables independent from the in-situ observations.

How to cite: Kokoszka, F., Le Roux, B., Iudicone, D., Conversano, F., and Ribera D'Alcalà, M.: Long-term variability of the coastal ocean stratification in the Gulf of Naples:Two decades of monitoring the marine ecosystem at the LTER-MC site, between land and open Mediterranean sea, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16918, https://doi.org/10.5194/egusphere-egu23-16918, 2023.

11:50–12:00
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EGU23-3950
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OS2.2
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ECS
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On-site presentation
Ali Reza Payandeh, Libe Libe Washburn, Brian Emery, and Carter Ohlmann

Submesoscale eddies form an important component of the circulation of the Southern California Bight (SCB), greatly impacting ecological processes. Despite their acknowledged significance in influencing ocean physics and biology, submesoscale eddies have been exceptionally hard to observe because of the technical challenges posed by both field and remote platforms. Here using a decade of high-frequency radar (HFR) surface current data we address this challenge for the SCB. Over the ten years of data, our research has mapped out the spatial distribution of submesoscale eddies and provided their seasonal and inter-annual variations. Between 2012 and 2021, a total of 235229 eddies were detected, averaging 452 eddies per week. Of these, 56% were cyclonic and 44% were anticyclonic. The contribution is roughly equal if eddies through their life spans are counted as one occurrence. This is because cyclonic eddies lived longer. The spatial distribution of eddies exhibited strong topographically related heterogeneity. Spatially coherent eddies, which reoccurred in certain locations over time, formed hotspots of eddy activity, largely in association with headlands. However, there were hotspots that did not seem to be associated with any typographic feature. Eddy temporal variations were examined at seasonal and interannual scales. On seasonal scales, eddies were found to be more numerous in the summer and early fall than in the spring. In August, the number of eddies was the highest, with 55% more observed eddies than in April, the least active month. The strong equatorward flow in the springtime seems to be linked with the reduced eddy activity at this time, likely due to the flow's suppressing effect on vortices and instabilities. At interannual scales, the eddy activity substantially increased in association with the 2014-2015 Blob event and the 2015-2016 El Niño. Observed eddies rose by 38% in 2014 compared to 2013 and remained high in 2015 and 2016. The results of this study are useful for the validation of numerical modeling studies in the SCB and could be of interest to the biological community to evaluate links between ecosystems and submesoscale activity along the highly productive coasts of the SCB.

How to cite: Payandeh, A. R., Libe Washburn, L., Emery, B., and Ohlmann, C.: Submesoscale Eddies in the Southern California Bight Derived from a Decade of High Frequency Radar Observations, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3950, https://doi.org/10.5194/egusphere-egu23-3950, 2023.

12:00–12:10
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EGU23-13065
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OS2.2
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Virtual presentation
Vassilis Zervakis, Evangelia Krasakopoulou, Elina Tragou, Vassilis Kolovoyiannis, Ioannis Mamoutos, Manos Potiris, Ioannis Androulidakis, Korina Mosiou, Maria Ignatia Kalatzi, Aikaterini Anna Mazioti, Christos Chatzilaou, Rafailia Filitsa Kougioumtzoglou, and Stamatios Petalas

The North Aegean Sea is a sub-basin of the Mediterranean which exhibits a range of oceanic processes at various scales. Due to the inflow of very light, mesotrophic Black-Sea waters it is the most productive region of the seas around the Hellenic Peninsula, although the regular seasonal coastal upwelling along its eastern shores does not contribute to its productivity. Despite the continuous buoyancy import by the Black Sea, the North Aegean hosts the densest waters of the Eastern Mediterranean. Finally, three semi-enclosed bays located in two islands of the North Aegean exhibit an alternating behavior as sources or sinks of buoyancy for the basin, while their productivity and natural beauty support a range of coastal activities. For the above reasons, the University of the Aegean has invested over several years in the development of a coastal oceanographic observatory (AEGIS), covering both the open North Aegean Sea and the three main bays of the islands of Lesvos and Lemnos. The Observatory consists of a numerical modeling component and an observational component.

The modeling component of the observatory consists of four coastal circulation models (for the three bays and the island of Lesvos) nested within a larger domain circulation model covering the whole Aegean Sea north of 37º N. Data assimilation, employing both satellite (sea-surface temperature and sea-level) and field data (employing mostly ARGO float observations) is used in the model of the extended domain (an implementation/configuration of the ROMS system), while the observations obtained in the coastal regions are currently used for coastal models’ (DELFT-3D FLOW and ROMS) validation. In addition to the above circulation models, SWAN is used to simulate the surface waves and DELFT-3D WAQ is being implemented to simulate the biochemical functioning at the various model domains.

The observational component at small geographical scales (in the Bays) comprise of continuous meteorological and oceanographic observations through an oceanographic mooring in the middle of the Bay of Kalloni, sea-level observations at the Bays of Kalloni and Gera, and High-Frequency radar observations of sea-surface currents and waves in a region east of Lemnos island, aiming to monitor the Black Sea outflow into the Aegean. The above continuous measurements are supplemented by periodic hydrographic and biogeochemical measurements in the three Bays, to validate the models and calibrate the in-situ continuous data. A recent addition to the AEGIS’s observational arsenal is an ocean glider aimed to capture the variability of the open North Aegean sea.

The AEGIS Observatory provides the necessary background to support strategic planning of human interventions at regional and local scales, such as Marine Spatial Planning or the construction of river dams affecting sensitive coastal basins. The implementation of the Coastal Laboratory has been supported by several projects, the most recent being the project “Coastal Environment Observatory and Risk Management in Island Regions AEGIS+” (MIS 5047038), implemented within the Operational Programme “Competitiveness, Enterpreneurship and Innovation” (NSRF 2014-2020), cofinanced by the Hellenic Government (Ministry of Development and Investments) and the European Union (European Regional Development Fund).

How to cite: Zervakis, V., Krasakopoulou, E., Tragou, E., Kolovoyiannis, V., Mamoutos, I., Potiris, M., Androulidakis, I., Mosiou, K., Kalatzi, M. I., Mazioti, A. A., Chatzilaou, C., Kougioumtzoglou, R. F., and Petalas, S.: Development of a Coastal Oceanographic Observatory for the North Aegean Sea: The AEGIS projects, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13065, https://doi.org/10.5194/egusphere-egu23-13065, 2023.

12:10–12:20
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EGU23-15804
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OS2.2
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ECS
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On-site presentation
Lisa Deyle, Dr. Jens Meyerjürgens, and Dr. Thomas Badewien

A data set detected by a high-resolution Lagrangian surface drifter is presented for the North Sea from 2017-2021. The North Sea is a marginal sea and is considered a shallow water shelf for most of its area, making its oceanographic dynamics quite different from those in the deep ocean. In contrast, it is less dominated by baroclinic dynamics but is strongly driven by tides, which results in a significant difference in the circulation patterns of particle motions. Numerous Lagrangian drifter observations have been deployed to gain a better understanding of the current behavior at the sea surface. Compared to Eulerian approaches and remote sensing methods, such as high-frequency radars and satellite altimeters, the Lagrangian measurement method can resolve fine current structures at spatial and temporal scales while covering a large region. In addition, Lagrangian methods are variable in space and time, allowing analysis of fine submesoscale fluid dynamics, such as divergence and eddy dynamics, by using clusters of drifters.

The methods suitable for calculating surface and tidal currents using drifter position data are presented. Thus, using the large amount of data collected from 2017 to 2021, this study provides a high-resolution mean surface current map and gridded representation of tidal dynamcis in the North Sea. Significant differences between the shallow water shelf and the deep area of the North Sea become apparent. While tidal currents dominate the shallow coastal areas, deep areas such as the Skagerrak register a high mean residual circulation driven by high density gradients. Comparison with other measured data proves that the chosen methods to calculate the currents are reliable. This presents the potential for Lagrangian measurements by surface drifters and the capability of the already detected data set, as it can be used for further analysis and to advance and calibrate numerical models.

How to cite: Deyle, L., Meyerjürgens, Dr. J., and Badewien, Dr. T.: Gridded Lagrangian surface drifter observations in the North Sea: An overview on high resolution tidal dynamics and surface currents, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15804, https://doi.org/10.5194/egusphere-egu23-15804, 2023.

12:20–12:30
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EGU23-1363
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OS2.2
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On-site presentation
Sandra-Esther Brunnabend, Lars Axell, Maximo Garcia-Jove, and Lars Arneborg

The Orust-Tjörn fjord system is located on the west coast of Sweden and consists of several fjords with many small islands. The fjord system has more than one connection to the open water, enabling a generally counterclockwise circulation through the fjords. It is home to nature reservoirs, different industries on land and aquaculture farms. It is threatened for example by hypoxic areas, invasive species, water pollution and algae blooms with the water quality strongly been influenced by the water exchange in the fjord system. Therefore it is important to understand the circulation, the state and the exchange of w­ater between the fjords system and the open water outside the fjord.

Not much knowledge of the circulation inside the fjords and the drivers of the water exchange between the fjords and the open water exists. The reasons are that observations are spatially sparse and the resolution of regional ocean circulation models are generally too coarse to resolve this complex fjord system with its shallow and narrow straits between the different fjords. Therefore, we developed a setup of a coastal ocean circulation model with a horizontal resolution of 50 m to study the drivers of water exchange of the Orust-Tjörn fjord system. Within a sensitivity study a set of simulations are performed using (a) temporally constant wind forcing, (b) temporally and spatially constant sea level at the open boundaries (c) no tides, and (d) constant offshore density, i.e. temporally and spatially constant temperature and salinity profiles at the open boundaries. The simulation period is September 2016 – February 2017, which includes a high saline water inflow in October 2016.

Model results compare well with observations from moored high-frequency velocity, temperature and salinity instruments as well as regular monitoring data. Results show for example that the density difference between the southern and northern entrance of the Orust-Tjörn fjord system highly influences the water exchange between the fjords and open water. This is because with constant offshore density applied, near surface velocities of the Baltic current as well as the circulation above sill level within the fjord system weakens. The timing and strength of the high-saline inflow event is most sensitive to the cases of constant winds and constant offshore densities. In general, we will present a detailed analysis of the main drivers of water exchange above sill level.

How to cite: Brunnabend, S.-E., Axell, L., Garcia-Jove, M., and Arneborg, L.: What drives the water exchange above sill level in the Orust-Tjörn fjord system?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1363, https://doi.org/10.5194/egusphere-egu23-1363, 2023.

Lunch break
Chairperson: Manuel Espino Infantes
14:00–14:05
14:05–14:15
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EGU23-7107
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OS2.2
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ECS
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On-site presentation
Xavier Sánchez-Artús, Vicente Gracia, Manuel Espino, María Liste, Marc Mestres, and Agustín Sánchez-Arcilla

Celia storm was an intense event that hit the NW Mediterranean Spanish coast during March 2022. During those dates a study was conducted where 2 instrumented platforms were installed, together with the gathering of high-resolution topobathymetric information at the Sant Sebastià and Sant Miquel beaches (Barcelona). The information taken from this campaign helped to calibrate and validate separately the hydrodynamics of the models XBeach and COAWST. A nesting strategy was done between these models in order to improve the validation of XBeach hydrodynamics. The approach is designed for a pass from a pre-operational to an operational framework in the future.

The aim of the study is to integrate both models within a reasonable computational time and good accuracy which will help to forecast possible flooding and erosion hazards and consequently create an Early Warning System in the area. The full strategy comprises atmospheric and hydrodynamic forcings from CMEMS into COAWST that feed the hydrodynamic conditions of XBeach. The simulations were done using the MPI modules of the models to reduce the computational expense and the post-processing using Python/Matlab.

Results from the validation of the models will be presented as well as the inundation and the erosion derived from the storm impact at the area. Also, some methodologies that could be applied for validate both outputs will be discussed.

Funding: This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 101037097 (REST-COAST project).

Acknowledgments: The first author has the support of the Secretariat for Universities and Research of the Ministry of Business and Knowledge of the Government of Catalonia and the European Social Fund.

How to cite: Sánchez-Artús, X., Gracia, V., Espino, M., Liste, M., Mestres, M., and Sánchez-Arcilla, A.: COAWST-XBeach nesting strategy validation for the Celia storm at the Barceloneta beach, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7107, https://doi.org/10.5194/egusphere-egu23-7107, 2023.

14:15–14:25
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EGU23-280
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OS2.2
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ECS
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On-site presentation
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Thanh Huyen Tran, Duy Thai To, and Alexei Sentchev

The middle southern coasts of Vietnam (11-15ºN) are featured by a large upwelling in summer which is governed by various physical processes i.e. regional circulations, monsoonal wind, and tidal rectification. Through the HF radar measurements acquired during April-May, 2019, a transition period of the Asian monsoon, three prominent patterns of local circulation have been revealed: a northern current intrusion as a result of South China Sea Western Boundary Currents (SCSWBC); a strong southeast jet occurring at ~30km from the coast; and a seaward current appearing for several days. In order to acquire a better understanding of the regional hydrodynamics, a 3D circulation model SYMPHONIE was run covering the measurement periods of HF radar and AWAC. Sea surface current (SSC) time series obtained from HF radar and AWAC were found to be strongly correlated (R=0.58, RMSE=0.10, MAE=0.07 for u- and R=0.72, RMSE=0.13, MAE=0.11 for v-components) (Fig 1). Three subdomains (nearshore, middle-range and far-range) have been identified within the radar coverage region for detailed analysis and comparison with the model. The comparison revealed that during the first 20 days, when the SE wind prevailed, the model does not seem to capture well the variability of SSC (Fig 2). However, when the wind changed to S-SW direction, the model results show a good agreement with HF radar measurements. Besides, an eddy forming near the coast on April 16 has been well represented by both model and HF radar (Fig 3). The uncertainty of modeled velocity fields can result from the uncertainty in forcing fields. Thus, the next step of our research will be to optimize the forcing field (i.e., wind) using HF radar data with an expectation to achieve better model results of SSC variability.

 

Figure 1 Comparison of SSC time series from  HF radar (black solid line) and AWAC (red asterisk points)

Figure 2 Space averaged U- and V-velocity components of SSC from SYMPHONIE model (dash line) and HF radar measurements (solid line) in three subdomains: nearshore (a, d); middle range (b, e) ; and far range (c, f). Wind vector during the measurement period (g).

Figure 3 An eddy in SYMPHONIE model simulation (left)  and HF radar measurements (right) on  April 16, 2019. Color scale represents curl of surface velocity superimposed by SSC vectors. Isobaths are shown by black lines.

How to cite: Tran, T. H., To, D. T., and Sentchev, A.: Coastal dynamics in middle-south Vietnam during a transition period of Asian monsoon, characterized by HF radar measurements and numerical modeling, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-280, https://doi.org/10.5194/egusphere-egu23-280, 2023.

14:25–14:35
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EGU23-9173
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OS2.2
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ECS
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On-site presentation
Jannik Kuehn, Stéphane Abadie, and Volker Roeber

High-resolution wave forecasts are of critical importance for coastal safety, hazard prevention, and energy transition. Examples that benefit from detailed information of coastal sea states range from the adaptation of coastal protection to beach goer and marine safety and even include the growing market of marine renewable energy. While regional and global wave forecasts exist, local high-resolution details are often not accessible due to the associated computational cost.

In our work we use a neural network to apply a so-called super-resolution approach that can turn wave forecasts computed over coarse grids into substantially higher resolution at very low computation cost and with only little loss of overall quality. The idea is to train the neural network with pairs of coarse and fine-grid computations, so that later on wave computations over coarse grids can be converted into a higher resolution. While the amount of saved computation time varies with the level of resolution between coarse and fine grid, the super-resolution approach can be more than 50-times faster than a direct high-resolution computation and still provide good accuracy.

Here we will present a case study on a 44-year hindcast of the French Basque coast, with which we trained and tested multiple networks. We will comment on the dependency of model performance on the amount of training data and the difficulties of an unstructured grid, compared to a structured one. More specifically, structured grids can be handled as regular images, which makes the adaptation of classical and powerful convolutional neural networks to the problem relatively easy. The application to irregular grids, however, is not trivial and requires different approaches like graph neural networks or multi-layer perceptrons.  Lastly, we will compare the performance of a surrogate model, that is, a neural network that simply replaces completely a spectral wave model like SWAN, with our super-resolution approach, that uses coarse wave model computations as an input. We argue that both approaches are complementary and have their advantages and disadvantages in specific settings. 

How to cite: Kuehn, J., Abadie, S., and Roeber, V.: Neural-network-based super-resolution on unstructured meshes of coastal spectral wave computations, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9173, https://doi.org/10.5194/egusphere-egu23-9173, 2023.

14:35–14:45
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EGU23-6088
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OS2.2
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ECS
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On-site presentation
Grégoire Thoumyre, Erwin Bergsma, Rafael Almar, Alain Giros, Solange Lemai-Chenevier, Stéphanie Artigues, and Thierry Garlan

        Coastal areas host 53% of the world's population increasingly subject to risks related to climate change. In order to understand and prevent these risks, the prediction of coastal hydrodynamic and morphological evolution is essential. Bathymetry is a key geophysical variable in  A key parameter to improve numerical coastal hydrodynamics models is the bathymetry. High resolution satellites now allow to observe coastal areas at a regional to global scale in a most cost-efficient way rather than local traditional echo sounding bathymetry measurements. We present S2Shores (Satellite to Shores), a new state-of-the-art python library developed to estimate wave field characteristics such as wavelength, period, direction, celerity to derive bathymetry from satellites. The core code is optimized to process optical satellite imagery, moreover the library is built in an object-oriented structure allowing efficient and agile manipulation of the modules developed from input and output handling to post-precessing.  S2Shores is optimized, using parallel computing with Dask python library, to compute large spatial scale, or time series evolution bathymetry as well on HPC cluster as on local computer. For example a bathymetry of 4400 km² of ocean, around the French Gironde estuary, can be computed in 90 sec (using 30 cores and 9.5 Go memory usage) with a 500 meters output grid resolution. We present a work in progress new python library for bathymetry estimation that will be open to the public to use and propose collaborative improvements.

How to cite: Thoumyre, G., Bergsma, E., Almar, R., Giros, A., Lemai-Chenevier, S., Artigues, S., and Garlan, T.: A new python tool for coastal bathymetry estimation : S2Shores, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6088, https://doi.org/10.5194/egusphere-egu23-6088, 2023.

14:45–14:55
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EGU23-10962
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OS2.2
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Virtual presentation
Yuezhang Xia, Shaohua Wang, Zhiguo He, and Hengye Gu

The rheological properties of natural mud are closely related to nautical depth estimation, wave propagation, and morphology evolution of muddy coast. In this study, the rheological properties of the natural mud collected from Luxi Island and Zhoushan Island in China were investigated. Shear stresses in steady state or oscillatory state were imposed on mud samples directly to obtain the yielding process under tidal currents or waves. The results showed that both apparent viscosity and complex viscosity experienced two sharp declines with increasing shear stress, indicating a two-step yielding nature of natural mud. Two yield stresses, namely, static yield stress and fluidic yield stress correspond to the yielding processes of elasticity and viscosity breakdown, respectively. The static yield stress in the oscillatory shear stress tests was lower than that in the steady shear stress tests, and the fluidic yield stress of natural mud in oscillatory shear stress tests was higher than that in the steady shear stress tests. The above phenomenon was explained by the viscoelastic-oscillation theory. Furthermore, the experimental results indicated that the initial storage modulus had a closer connection to both yield stresses in comparison with mud density. This study not only provided a guideline for having a better understanding of the two-step yielding process of natural mud, but will also provide scientific support for the assessment of fluid-mud formation, sediment transport and morphology evolution, the interaction between waves or tidal currents and muddy seabed, and protection of seafloor infrastructures.

How to cite: Xia, Y., Wang, S., He, Z., and Gu, H.: The yielding process of the natural mud under current and wave shear stress, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10962, https://doi.org/10.5194/egusphere-egu23-10962, 2023.

14:55–15:05
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EGU23-1486
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OS2.2
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ECS
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Virtual presentation
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Ivan Hernandez, Leidy Maricela Castro Rosero, Manuel Espino Infantes, and Jose María Alsina Torrent

Transport mechanisms of floating marine litter (FML) in coastal zones are poorly understood. Tracking FML dispersion with numerical models is complex due to the geometry, hydrodynamic processes and the influence of coastal processes, the latter being especially challenging to incorporate. Within the TRACE (Tools for a better management in coastal environments to accelerate tRAansition to Circular plastic Economy) project, however, the LOCATE tool was developed to simulate the motion and accumulation of plastic particles in coastal areas, using nested grids of varying spatial scales and resolutions (2.5 km, 350 m and 70 m) to account for coastal processes. LOCATE couples Eulerian hydrodynamic data with a Lagrangian particle solver, thus requiring configuration and optimization. Regional Eulerian hydrodynamic data are obtained from Copernicus Marine Environment Monitoring Service (CMEMS) products whereas coastal hydrodynamic simulations use the open-source Coupled Regional Modeling System (COAWST) system. The Lagrangian solver uses the open-source OceanParcels (Probably a Really Efficient Lagrangian Simulator) model (van Sebille, et al., 2020). As proof of concept, the model was applied to the Barcelona coastline where breakwaters can behave as marine litter traps and concentrations are comparable to some other heavily polluted areas such as the Atlantic and Pacific gyres (Sánchez-Vidal, et al, 2021).

Observational data from 2017 from the Llobregat and Besòs rivers, two known sources of FML around Barcelona, were used to run simulations to determine how LOCATE can predict litter accumulation zones when compared to beach cleanup data. Both rivers are the major rivers around the Barcelona coastline and have been hypothesised to be an important source of plastic in the region. A beaching module that detects, quantifies, stores location and time, and removes particles that have crossed the land-water boundary was developed that uses a vector-resolution coastline, and as such is independent from the limiting spatial resolution of the nested grids at coastal scales. The coastline was divided into 16 zones, as well as five water boundary zones on the perimeter of the study area (40.88°N to 41.81°N, 1.38°E to 3°E). 

Simulations of particles released at hourly intervals were carried out between February and October 2017, with 552,400 released in total. Results show overall beaching rates of 91.5%, higher than other larger scale studies. The most impacted areas were around the release sites and adjacent beaches to the south, showing a NE to SW transport; the Llobregat river mouth being the most affected with over 200 particles km-1 day-1. A non-dimensional beaching bias index was used to identify areas that have a greater partiality to receive particles from a release point, such as areas south of the Llobregat river. Residence time at sea was highly variable with very short times recorded for the Besòs river mouth and adjacent areas (< 1 hour). Preliminary results will be presented to determine possible factors contributing towards high beaching rates and litter accumulation in zones. The ultimate aim of the present system and model is to demonstrate its exportability and adaptability to other coastal regions.

How to cite: Hernandez, I., Castro Rosero, L. M., Espino Infantes, M., and Alsina Torrent, J. M.: Numerical simulation and analysis of floating marine litter dispersion and accumulation in coastal regions around Barcelona city, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1486, https://doi.org/10.5194/egusphere-egu23-1486, 2023.

15:05–15:15
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EGU23-830
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OS2.2
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On-site presentation
Berna Ayat, Burak Aydogan, Yana Saprykina, and Margarita Shtremel

Changes in wave heights during the propagation toward the coastline are influenced by many environmental factors. Under the complex effect of environmental processes, wave heights change due to energy dissipation, and the waves break under certain conditions. Due to the importance of predicting the wave heights in coastal areas, improving the prediction performance of spectral wave models by incorporating better physical descriptions of wave growth and dissipation attracts the interest of researchers. In this study, we aimed to quantify the sensitivity of wave height predictions to changing growth and dissipation parameterizations in a spectral wave model SWAN Cycle III Version 41.31A. Spectral wave model SWAN is used to hindcast the significant wave heights measured between the dates October 17 and November 10, 2018, at Shkorpilovtsi in the western Black Sea. Model runs are executed on an unstructured mesh-based spectral model of the Black Sea. The model is forced by ERA5 wind fields provided by European Centre for Medium-Range Weather Forecast. ST6 physics package is considered in this study for sensitivity analysis. The performance improvement in the prediction of Black Sea wave heights provided by the default parameterization of ST6 physics in comparison to default model parameterizations of Komen, Janssen, Westhuysen is shown previously. Further investigation on the sensitivity of modeled wave heights to ST6 parametrization is conducted in this study. Chosen ST6 growth and decay parametrizations needs to be coupled with swell dissipation terms. SWAN model presents Ardhuin and Zieger swell dissipation models. Coupling with the swell models provided ten model runs in total which are to be compared with the in-situ measurements by using error metrics including correlation coefficient, root mean square error (rmse), and bias. Sensitivity analysis based on given model runs are performed to identify the contribution of each parameter to resultant wave heights. Sensitivity analysis indicated an 8-30% of underestimation in the highest waves for the study area.

 

Acknowledgments: This research is supported by The Scientific and Technological Research Council of Turkey (TÜBİTAK) under grant number 119N400 and RFBR 20-55-46005.

 Keywords: Spectral wave modeling, wave hindcasting, sensitivity analysis

 

How to cite: Ayat, B., Aydogan, B., Saprykina, Y., and Shtremel, M.: Sensitivity of wave predictions to growth and dissipation parameterizations, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-830, https://doi.org/10.5194/egusphere-egu23-830, 2023.

15:15–15:25
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EGU23-13607
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OS2.2
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ECS
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On-site presentation
Circulation in the vicinity of a submerged stream groyne under mesotidal impact (East Frisian Islands, Southern North Sea)
(withdrawn)
Michelle Albinus
15:25–15:35
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EGU23-1657
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OS2.2
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ECS
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On-site presentation
Rain Männikus, Tarmo Soomere, and Ülo Suursaar

Wave parameters set the base for the design of coastal structures. For this purpose, commonly modelled wave properties are employed. This approach is usually adequate in the open ocean conditions where variations in the wave properties are normally quite limited. The situation is different in the nearshore areas of basins of complicated shape where wave properties can be highly variable. Unfortunately, in many cases, long and sufficiently detailed wave measurements for model validation are not available. The use of default settings of wave models means that possible errors remain unknown. This approach could lead to overdimensioned structures or to structural failures. We address the magnitude of possible errors in such conditions by comparing the output of simple wave models (such as a fetch-based SMB model, the SWAN model forced with one-point homogenous wind, etc.) and a sophisticated multi-nested SWAN wave model forced with ERA-5 winds with recent wave measurements in various nearshore locations in the eastern Baltic Sea. We use records of different length over more than 10 years. While in some locations simple models or models forced with homogenous wind lead to acceptable results, in most areas more sophisticated models are needed to adequately replicate wave properties. The outcome of our analysis provides several site-specific hints for practical coastal engineering.

How to cite: Männikus, R., Soomere, T., and Suursaar, Ü.: How do simple wave models perform compared with sophisticated models and measurements in the eastern Baltic Sea?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1657, https://doi.org/10.5194/egusphere-egu23-1657, 2023.

15:35–15:45
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EGU23-4870
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OS2.2
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ECS
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On-site presentation
|
Ahmad Bayhaqi, Jeseon Yoo, Donghwi Son, Min-Seon Bang, and Sung-Hwan Park

Ocean Wave conditions play a crucial role in the coastal region, influencing coastal communities and human activities. In this study, a 42-year data with the period of 1980-2021 from ERA-5 Reanalysis has been employed to investigate the various temporal scale of significant wave height (Hs) variability in the surrounding seas of Korean Peninsula. The signal decomposition of long-term data has been done using Empirical Mode Decomposition (EMD). In the seasonal scale, the highest (lowest) Hs occurs in the winter (summer) season with the averaged value of 1.1 (0.4) meter. These variations were related to monsoonal winds, with the stronger winds during winter season leading to the higher Hs. Year-to-year variation displays the contribution of ENSO events; the appearance of El Nino could significantly reduce the Hs by weakening the magnitude of winter monsoon in which are statistically found in the East Sea and East China Sea. The long-term changes of Hs in the region show a clear trend in which summer (winter) season have increased (decreased) trend, owing to the enhanced typhoon activities and weakened winter monsoon respectively.

How to cite: Bayhaqi, A., Yoo, J., Son, D., Bang, M.-S., and Park, S.-H.: Variability of wave heights in marginal seas around Korea analyzed using ERA5 Reanalysis data, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4870, https://doi.org/10.5194/egusphere-egu23-4870, 2023.

Coffee break
Chairperson: Davide Bonaldo
16:15–16:20
16:20–16:30
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EGU23-10898
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OS2.2
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Virtual presentation
Li Li, Yihan Ren, Xiao Hua Wang, and Yuezhang Xia

The hydrodynamics and sediment characteristics of muddy estuaries and coasts during typhoons are closely related to geomorphic evolution, ecological environment, and economic development of coastal zones. Taking the macro-tidal turbid Hangzhou Bay (HZB) as an example, the sediment characteristics and the effects of wave-current interactions on sediment dynamics during Typhoon Mitag were studied using a well-calibrated numerical model. The model considers tides-wave-sediment interactions and the reconstructed typhoon wind field. The net sediment fluxes were controlled by residual currents and SSC. The waves and winds dominated the sediment resuspension. The combined interactions of currents and waves led to high SSC during the typhoon. In calm conditions, the impact of wave-current interactions was small except for the combined bottom stresses. The combined bottom stress was the primary wave-current interaction changing the sediment resuspension and increasing SSC, especially in shallow waters or during storms. The advection term, which played an essential role in reducing the SSC in HZB, mainly affected the SSC by enlarging the velocity. The wave dissipation term enhanced the vertical mixing, which involved the vertical exchange of suspended sediment and the currents. In the shallow waters of the southern bay, the wave dissipation term mostly led to the decrease of bottom stresses, the increase of currents, and the decrease of SSC, while the rise of SSC in the deep waters. The effects of the form drag, wave radiation stress, and refraction terms on suspended sediment dynamics were relatively small. The findings provide the theoretical foundations for the study of dynamics geomorphology in macro-tidal estuaries.

How to cite: Li, L., Ren, Y., Wang, X. H., and Xia, Y.: Sediment dynamics in Hangzhou Bay during Typhoon Mitag, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10898, https://doi.org/10.5194/egusphere-egu23-10898, 2023.

16:30–16:40
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EGU23-13657
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OS2.2
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ECS
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On-site presentation
Matteo Lorenzo, Paolo Pezzutto, Filippo De Lillo, Francesco Michele Ventrella, Francesco De Vita, Piero Ruol, Federico Bosia, and Miguel Onorato

In a framework of changing climate, it is important to find alternative solutions for coastal protection. Indeed, the pressure of anthropogenic origin, combined with natural forcings, has contributed both to a worsening of the environmental quality of coastal areas, and to the triggering of erosion dynamics, with retreat of the sandy coast.

Tethered floating breakwaters, built as a regular lattice of reversed pendula, can provide an alternative solution for beach management. With respect to rubble mound breakwaters, this type of structures has small impact on water circulation, and, in the presence of rising sea levels, it is much more adaptable than an artificial reef. Depending on their efficiency, the cost-effectiveness of beach protection using tethered floats is favorable compared to the current hard-engineering strategies.

For this purpose, inspired by the concept of metamaterial wave control, a floating device has been tested in a wave flume with a two-dimensional periodic configuration. Metamaterials are engineered structures designed to interact with waves and manipulate their propagation properties. The device is built as an array of tethered submerged cylinders, with their axes parallel to the wave crests. The idea is to investigate the conditions which lead to the formation of bandgaps, which is the key factor for mitigating the incoming energy of the surface gravity waves.

Experimental results demonstrated the feasibility of the concept, and that wave attenuation can be significant, even using a limited number of cylinders. The analysis of the results, have allowed us to assess that two leading mechanisms, dissipation and reflection, contribute to wave attenuation. If the cylinders are fully immersed, dissipation induces a broad bandgap around a resonance frequency that depends on the characteristics of the single pendulum. Instead, wave scattering (reflection) is relevant around frequencies that can be predicted using the generalized Bragg condition and the second harmonic generation, where the most significant bandgaps in attenuation can be observed. The second harmonic generation effect is a typical non-linear phenomenon, linked to the geometrical configuration of the device. In our tests, this behavior can be observed even for very small amplitude incident waves.

In conclusion, these results show the possibility to tune the position of the attenuation bands in the wave spectrum by modifying system parameters, to make possible the implementation of an efficient wave absorber for coastal protection.

How to cite: Lorenzo, M., Pezzutto, P., De Lillo, F., Ventrella, F. M., De Vita, F., Ruol, P., Bosia, F., and Onorato, M.: An experimental study on a tethered floating metamaterial breakwater to attenuate surface gravity waves in a shallow water environment, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13657, https://doi.org/10.5194/egusphere-egu23-13657, 2023.

16:40–16:50
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EGU23-6519
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OS2.2
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On-site presentation
Michela De Dominicis, Judith Wolf, Rosanna van Hespen, Peng Zheng, and Zhan Hu

Coastal vegetation can reduce extreme water levels during storm events, but the controlling factors and processes in complex estuary or delta systems are still unclear. This limits an effective implementation of nature-based coastal defences in delta mega-cities in low-lying coastal areas.

To explore the effects of vegetation on storm surge dynamics and currents, we used a Finite Volume Community Ocean Model implementation for the South China Sea and the Pearl River Delta. We numerically modelled how mangroves can offer coastal protection to the large coastal cities located in the delta, such as Guangzhou and Shenzhen, during strong typhoons, like Hato (2017).

Additionally, we analyzed how the effectiveness of mangroves changes under different sea level rise scenarios.

Water level attenuation by mangroves is effective during extreme water level conditions and differences in mangrove forests' properties drive their coastal protection function. The local (within-wetland) attenuation of extreme water levels is more effective with wide vegetation patches and higher vegetation drag. Narrower vegetation patches can still provide non-local (upstream) water level attenuation if located in the upper estuary channels, but their design needs to avoid amplification of water levels in other delta areas.

How to cite: De Dominicis, M., Wolf, J., van Hespen, R., Zheng, P., and Hu, Z.: Effectiveness of mangroves as nature-based coastal defences in the Pearl River Delta, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6519, https://doi.org/10.5194/egusphere-egu23-6519, 2023.

16:50–17:00
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EGU23-16529
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OS2.2
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ECS
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On-site presentation
Massimiliano Marino, Rosaria Ester Musumeci, Luca Cavallaro, and Enrico Foti

The South-East of Sicily is characterized by a complex system of coastal lagoons. The site, is considered of great naturalistic value, as it hosts a rich biodiversity and represents an important stop for bird species that migrates through the Northern European-African route. According to recent studies, the site is subject to an ever-increasing climate related coastal erosion and flooding risk, with an estimated potential land loss of 6.2 km2 by 2100 (Antonioli et al. 2020). In the present work, the effectiveness of a dune revegetation is investigated, in order to understand the role played by environmental restoration in reducing coastal risk. A SWAN+XBeach (Booji et al. 1996; Roelvink et al., 2009) numerical modeling chain is developed, aimed to simulating the hydraulic and transport processes that characterize a coastal area, in order to evaluate the effectiveness of the dune revegetation intervention. Results show a reduction of coastal flooding risk due to extreme wave events as an effect of the extended vegetated dune strip. Presence of the vegetation drastically improve coastal protection to the city area. Specifically, a reduction up to 42% of the flooded city area is observed. 

References 

Antonioli, F., Defalco, G., Moretti, L., Anzidei, M., Bonaldo, D., Carniel, S., ... & Schicchitano, G. (2019). Relative sea level rise and potential flooding risk for 2100 on 15 coastal plains of the Mediterranean Sea. In Geophysical Research Abstracts (Vol. 21). 

Booij, N., Holthuijsen, L.H. and R.C. Ris, 1996, The SWAN wave model for shallow water, Proc. 25th Int. Conf. Coastal Engng., Orlando, USA, Vol. 1, pp. 668-676. 

Roelvink, D., Reniers, A., van Dongeren, A., van Thiel de Vries, J., McCall, R., & Lescinski, J. , 2009. Modelling storm impacts on beaches, dunes and barrier islands. Coastal Engineering, 56(11-12), 1133-1152. doi:10.1016/j.coastaleng.2009.08.006 

How to cite: Marino, M., Musumeci, R. E., Cavallaro, L., and Foti, E.: Coastal restoration measures to mitigate coastal flooding in a context of climate change: the case of the South-East of Sicily, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16529, https://doi.org/10.5194/egusphere-egu23-16529, 2023.

17:00–17:10
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EGU23-3309
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OS2.2
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On-site presentation
Wenyan Zhang, Peter Arlinghaus, Lucas Porz, and Corinna Schrum

Morphological change of coastal and shelf seas is controlled jointly by physical, biological and anthropogenic processes and their interactions. While physical and anthropogenic drivers are normally regarded to exert a primary control on morphodynamics, the role of biota, especially benthos, in guiding long-term and large-scale evolution of coastal landscape/seascape is often overlooked and has received less attention. It was not until recent decades that research has revealed the importance of benthos in coastal protection. Further, as an indispensable part of the ecosystem, benthos not only consists of a significant part of organic carbon, but also plays a vital role in mediating carbon and nutrient fluxes across the sediment-water interface. The interaction between benthos and its ambient environment is twofold and dynamic. On one hand, coastal morphology, oceanographic forcing (e.g. tides, waves) and carbon/nutrient availability exert a first-order control on the type of habitats, as well as abundance and trait expression of benthos. On the other hand, benthos actively modifies its habitats and beyond to attain an optimized fitness for living conditions. Understanding such dynamic interactions is essential in management of coasts and shelf seas against present and future climatic threats and for sustainable use of coastal resources.

In this talk, we demonstrate the quantitative importance of fluid-sediment-benthos interactions in (1) guiding morphological development of a tidal embayment in the Wadden Sea and (2) carbon cycling in the great North Sea as exemplary case studies. We applied a novel 3-Dimensional physics-ecosystem coupled numerical model to resolve dynamic interactions among fluid forcing, organic carbon, sediment and benthos. Specifically, we aim to address two different but interrelated questions:

  • How important are fluid-sediment-benthos interactions in coastal morphological development? and
  • To what extent can such interactions affect carbon sequestration at a regional scale?

How to cite: Zhang, W., Arlinghaus, P., Porz, L., and Schrum, C.: Hydro-eco-morphodynamics and carbon cycling at coastal scales and beyond, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3309, https://doi.org/10.5194/egusphere-egu23-3309, 2023.

17:10–17:20
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EGU23-9577
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OS2.2
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ECS
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On-site presentation
Emily Summers, Jiabi Du, Kyeong Park, Karl Kaiser, and Jodi Ryder

Plastics have become ubiquitous in the modern consumer economy. Unchecked production, failure to implement efficient recycling practices, and poorly defined global policy regarding production and disposal has led to a prevalent plastic problem. Over the past decade, microplastic pollution has emerged as a forefront concern of plastic in the global environment. As marine microplastic pollution becomes a predominant area of interest, it is important to understand microplastic sources, delivery pathways, and ultimate fate. Estuaries are key zones to monitor for microplastic pollution, due to their close proximity to source areas, and their natural ability to filter pollutants. The Galveston Bay watershed is located near the densely populated Houston, TX metro area and manufactures potentially half of the United States’ pre-production plastics. Using a Lagrangian particle-tracking method coupled with a validated 3D hydrodynamic model, we examined the transport behavior of microplastics, as well as export ability of the Galveston Bay estuary. Accounting for the variability of type and density of microplastics, multiple settling velocities were simulated to examine their effect on behavior. Four release sites were chosen near highly populated river connections. We found that settling velocity has significant impact on both local exposure time and retention time. Neutrally buoyant particles were flushed quickly out of the bay, while heavier particles migrated westward and spent far more time in the bay overall. Release location influenced percent of particles retained in bay, with a higher percent of particles still present from northern release locations than southern release locations after two years of simulation. The use of modelling studies to provide successful estimation of microplastic transport pathways and export efficiency of Galveston Bay will help contribute to a more robust understanding of microplastic behavior within estuarine environments.

 

How to cite: Summers, E., Du, J., Park, K., Kaiser, K., and Ryder, J.: Modelling transport pathways of varying microplastics in an estuarine environment, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9577, https://doi.org/10.5194/egusphere-egu23-9577, 2023.

17:20–17:30
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EGU23-13650
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OS2.2
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ECS
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On-site presentation
Diego Pereiro, Oleg Belyaev Korolev, Martha Bonnet Dunbar, Gabriel Navarro, Caroline Cusack, Tomasz Dabrowski, Glenn Nolan, and Inger Graves

This work presents the steps towards the design and implementation of a marine observatory providing current and forecasted oceanic conditions relevant to the aquaculture sector, with particular focus on “Extreme Marine Events” such as marine heat waves, deoxygenation and storm surges. Examples of successful implementation of these guidelines in the framework of the EuroSea project are presented for two aquaculture sites: Deenish Island in Ireland and El Campello in Spain. In-situ measurements, remote-sensing observations and model forecasts are jointly provided to the end users. The process starts with the interaction with the stakeholders to understand their main needs and concerns, and is followed by the design of the software architecture that carries out the data acquisition, post-processing and visualization in an open-access web platform. User feedback is of paramount importance during the whole process to ensure that the services being offered in the end actually match the needs of the aquaculture sector.

How to cite: Pereiro, D., Belyaev Korolev, O., Bonnet Dunbar, M., Navarro, G., Cusack, C., Dabrowski, T., Nolan, G., and Graves, I.: An Observational and Warning System for the Aquaculture Sector in European Waters, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13650, https://doi.org/10.5194/egusphere-egu23-13650, 2023.

17:30–17:40
|
EGU23-14414
|
OS2.2
|
ECS
|
On-site presentation
Salvatore Causio, Simone Bonamano, Ivan Federico, Viviana Piermattei, Daniele Piazzolla, Sergio Scanu, Alice Madonia, Giovanni De Cillis, Eric Jansen, Giovanni Coppini, and Marco Marcelli

Complex processes involved in the river delta areas are not fully solved with a traditional structured-mesh model. A seamless unstructured-grid approach could serve as support to advance in the reproduction and understanding of the dynamics processes across different scales. In this work, a river-coastal-ocean continuum modeling representation has been developed for the Tiber River delta, including the surrounding coastaland open-ocean zones of the Lazio coast (Tyrrhenian Sea, Italy). This area has been selected because it includes important naturalistic sites but also a new commercial, fishery and leisure harbor whose the realization is scheduled for 2023. By using temperature and salinity profiles from near-river CTD data, we demonstrate that this representation simulates the coastal dynamic processes in the Tiber delta zone better than the classic coastal-ocean representation, minimizing calibration and sensitivity experiments. In this work, a large effort has been dedicated to the acquisition of new observations (CTD, drifters, currents radar, bathymetric survey) carried out over different spatial (open-ocean, coastal and near- and along-river) and temporal scales. Validation demonstrated that the model has good accuracy, also in reproducing the salt wedge intrusion along river. Furthermore, currents investigation suggested the existence of an anticyclonic gyre in proximity of the river mouth of the northern branch, mainly induced by river discharge and coastal morphology. These promising results in simulating cross-scale processes in a seamless fashion, will be included in the near future in an operational system for coastal forecasting.

How to cite: Causio, S., Bonamano, S., Federico, I., Piermattei, V., Piazzolla, D., Scanu, S., Madonia, A., De Cillis, G., Jansen, E., Coppini, G., and Marcelli, M.: River-coastal-ocean continuum modelling and assessment of nearshore dynamics, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14414, https://doi.org/10.5194/egusphere-egu23-14414, 2023.

17:40–17:50
|
EGU23-15601
|
OS2.2
|
On-site presentation
Antonio Guarnieri, Silvia Merlino, Marina Locritani, Damiano Delrosso, Marco Biancucci, and Marco Paterni

It is well established that rivers are amongst the most important carriers of the plastic pollution found in the oceans. However, the main processes contributing to plastic and debris fate through riparian systems is still poorly known and understood. The Marine Litter Drifter project from the Arno River aims at using modern consumer software and hardware technologies to track the trajectories and evolution at sea of real Anthropogenic Marine Debris (AMD) from rivers, with a specific focus on the Arno River, in Italy. Innovative and low cost “Marine Litter Trackers” (MLT) were designed, assembled and used in this framework as they are reliable, robust, self-powered and they present almost no maintenance costs. Furthermore, they can be built not only by those trained in the field but also by those with no specific expertise, including high school students, simply by following the instructions.

Several dispersion experiments were successfully conducted using different types of trackers in different seasons and weather conditions. The maximum distance tracked was 2845 km for a period of 94 days. The activity at sea was integrated by lagrangian numerical models supporting the planning of the deployments and the recovery of the drifters. The models, in turn could benefit from the observed tracking data for calibration and validation and serve as tools to study and interpret the processes driving macro plastic displacement at sea. In this presentation we describe this activity and we discuss the dynamics of marine litter (ML) dispersion in the Tyrrhenian Sea on the basis of these integrated monitoring tools, as well as the potential of open-source approaches including the “citizen-science” perspective for both improving Big Data collection and educating/awareness-raising on AMD issues.

How to cite: Guarnieri, A., Merlino, S., Locritani, M., Delrosso, D., Biancucci, M., and Paterni, M.: Marine litter tracking system: a case study with open-source technology and a citizen science-based approach, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15601, https://doi.org/10.5194/egusphere-egu23-15601, 2023.

17:50–18:00
|
EGU23-15910
|
OS2.2
|
ECS
|
On-site presentation
|
Aaron Furnish, Peter Robins, Simon Neil, David Cooper, and Huw Lewis

The interconnected nature of land and marine processes has led to the development of fully coupled climate models combining atmospheric, terrestrial, riverine and oceans dynamics, such as the UKC3 UK national climate model created by the Met Office. Although highly resolved at the order of ~1.5 km, UKC3 may not capture estuarine and intertidal processes accurately, such as surge propagation and interactions with river flows. Using hyper resolution (<20 m) unstructured grids, a Delft-3D Flexible Mesh Suite model has been created to identify the importance of resolving these features for impact studies such as coastal flood risk. To further improve on the resolution of previous models, 15-minute river discharge was included as well as wetting and drying for coastal zones. Using a case study of the eastern Irish Sea, which is hyper-tidal and includes eight estuaries and a significant intertidal zone, the Delft model has been compared against UKC3 for simulations of the 2013-2014 extreme winter storm season. Analysis of the UKCP18 climate scenarios will be implemented to the new Delft model to investigate for future climate change variations.

 

It is shown that there are clear differences in sea level variability between the models as well as differences in the salinity, storm surge frequency and flood severity. This research will allow us to optimise mesh resolution to accurately model the coastal environment for flood risk.

How to cite: Furnish, A., Robins, P., Neil, S., Cooper, D., and Lewis, H.: Pathways to Realistic Impact Modelling in Estuarine Areas, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15910, https://doi.org/10.5194/egusphere-egu23-15910, 2023.

Posters on site: Tue, 25 Apr, 08:30–10:15 | Hall X5

Chairpersons: Davide Bonaldo, Manuel Espino Infantes, Sandro Carniel
X5.333
|
EGU23-692
|
OS2.2
|
ECS
|
solicited
Ping Zhang, Qingshu Yang, Huayang Cai, and A. J. F. Ton Hoitink

The morphodynamics of tidal channels can be considerably altered by intensive human activities, such as the land reclamation and channel dredging. Morphological alterations of Lingdingyang Bay (LDB) in the Pearl River Delta (RPD) have received great attention, while the changes in Shiziyang (SZY) tidal channel connecting LDB with Humen Outlet is less known. In this study, bathymetric maps of the Shiziyang tidal channel in the PRD at different periods were collected to investigate the geomorphologic pattern by means of a digital elevation model (DEM). It was shown that the water depth increased with the decreasing width convergence length, indicating intensified channel deepening and narrowing, while tidal channel bed was drastically cut down due to port construction and channel dredging in 1959, 1975 and 2004, respectively. Consequently, the SZY eroded at a rate of 0.164 m/yr during the study period, with a new pattern of eastward-erosion and westward-deposition. In addition, erosion in the downstream reach (0.271 m/yr) was significantly faster than that in the upstream reach (0.006 m/yr). The EOF results showed that the impact of natural factor, channel dredging and land reclamation on bathymetric changes accounted for 48.48%, 20.54% and 11.57%, respectively. Furthermore, the spring-neap variability of tidal wave celerity and tidal amplification in SZY both increased after human interventions and there is a clear transition pattern and stronger tidal hydrodynamics according to the results of 1D analytical hydrodynamics model. Based on the model results, the decadal evolution of SZY morphology can be well reproduced by the observing water levels. The results obtained from this study can be particularly helpful for quantifying the potential impacts due to human interventions, which is useful for setting future conservation planning strategies in estuarine zones.

How to cite: Zhang, P., Yang, Q., Cai, H., and Hoitink, A. J. F. T.: Pattern changes in tidal channel morphodynamics under human interventions: a case of Shiziyang tidal channel in the Pearl River Delta, China, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-692, https://doi.org/10.5194/egusphere-egu23-692, 2023.

X5.334
|
EGU23-3798
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OS2.2
|
ECS
|
solicited
Arnaud Le Pevedic, Florian Ganthy, and Aldo Sottolichio

Important loss of seagrasses occurred worldwide during the last decades, resulting in less effective ecosystem services, the decline of environmental conditions and jeopardizing the survival of coastal ecosystems. To reverse the trend, seagrass restoration actions are essential. Despite increasing efforts made over the last decade, restoration projects still face challenges to be efficient, one of them being the accurate identification of suitable sites for restoration. This key step is highly dependent on a prior good knowledge of the physical stressors and on their interaction with seagrasses, which can only be analysed by numerical modelling at the relevant space and time scales.

This work aims at developing a coupled bio-hydro-morphological model able to consider the growth of vegetation in order to devise a successful strategy for the restoration. The model is applied first to the case of Zostera meadows in a mesotidal coastal lagoon (Arcachon Bay, France).

In this work, a coupled hydro-morphological model was improved to account for the effects of vegetation on a wide variety of bio-physical processes. This new modelling platform comprises the 3D hydrodynamic model MARS3D able to consider the feedback between leaf bending and the flow structure. The interactions between flow and seagrasses are computed through the production and dissipation of turbulent kinetic energy and the loss of momentum resulting from the drag exerted on the vegetation. This hydrodynamic model is combined to the spectral wave model WAVEWATCH III, in which the effect of vegetation on wave energy dissipation was recently implemented.
The process-based sediment transport model MUSTANG, which computes the evolution of the suspended sediment concentration in the water column and the sediment characteristics of the seabed, also constitutes this platform. This model includes the effect of the foliage on sediment deposition and the effect of root systems in the formulation of the sediment erodibility.
Finally, a vegetation growth model for Zostera computes the evolution of vegetation characteristics (production, loss and mortality) based on the external forcing (light, temperatures, hydrodynamics and desiccation). The spatial evolution of the meadows is modelled through rhizome extension, scouring as well as seed production and germination.

In Arcachon Bay, Z.noltei and Z.marina meadows have declined by 45% and 84%, respectively, since 1989, and their recolonisation is mainly hindered by physical stressors. A first analysis performed with a simple flow model accounting for vegetation provided a map of the most suitable areas for restoration. This new bio-hydro-morphological model aims at improving and refining these recommendations by providing a full set of parameters ranging from hydrodynamic variables to light availability. Then, the vegetation growth model would enable the verification of model predictions by testing the chosen restoration action through the artificial addition of seeds in the model. Besides determining the best areas for restoration, this model also provides information regarding the magnitude of the restoration effort (eg. surface, number of seeds) required for the recovery of the meadows in a given area.

How to cite: Le Pevedic, A., Ganthy, F., and Sottolichio, A.: Improving the success rate of seagrass restoration projects: Development of a new bio-hydro-morphological modelling platform accounting for vegetation growth, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3798, https://doi.org/10.5194/egusphere-egu23-3798, 2023.

X5.335
|
EGU23-6195
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OS2.2
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solicited
Shih-Feng Su, Wei-Hsuan Wu, Deng-Hong Chen, and Wen-Kai Weng

        Low-lying and small-scale coral reef islands are considered extremely vulnerable to the impacts of strong storms. Wave erosion is expected to destabilize reef islands and reduce them uninhabitable on the coast. Reef island morphodynamics have found to be dominated by nearshore wave hydrodynamics on reef platforms. Due to interactions between incident waves and reef morphology, wave characteristics on reefs are highly dependent on reef size, shape and island position, especially for the scale between O(100m) and O(1000m). In this study, laboratory experiments and numerical modeling are used to investigate wave transformation on a reef platform with a complex morphology. A prototype 1:100 three-dimensional reef island and platform were constructed on a wave basin of 50-m in length, 50-m in width and 1.0-m in depth, and nine wave gauges installed on the reef platform to observe water surface elevation under high-energy wave events from three incident directions. A numerical model XBeach is employed to compute short-period waves, long-period infragravity waves, wave setup and currents. Parameters in the wave-breaking dissipation formulation are calibrated against experimental data. Due to a varying of reef slopes surround the reef platform, the optimal breaking parametric values would be disparity between one- and two-dimensional simulations. The ideal values are decided by the model performance in two-dimensional simulation for wave and current fields. Long-period infragravity waves interlaced through refraction and diffraction on the complex localized reef morphology are further examined if the multiple mechanisms can drive shoreline amplification of long waves. The wave characteristics would provide critical indicators for accurate assessments of island shoreline change and better resolve the coast vulnerability.

How to cite: Su, S.-F., Wu, W.-H., Chen, D.-H., and Weng, W.-K.: Laboratory experiments and numerical modeling of wave transformations on a complex reef platform, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6195, https://doi.org/10.5194/egusphere-egu23-6195, 2023.

X5.336
|
EGU23-6430
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OS2.2
|
ECS
|
solicited
Sarah Antonia Rautenbach, Carlos Mendes de Sousa, and Paulo Relvas

In the frame of the European Multidisciplinary Seafloor and water column Observatory (EMSO-ERIC) a vertical wave-powered profiler (Wirewalker), an acoustic-doppler current profiler (ADCP), and an EMSO Generic Instrument Module (EGIM) were deployed from the R/V Mário Ruivo, in collaboration with the Instituto Português do Mar e da Atmosfera (IPMA), at the edge of the continental slope, »20 km south of Cape St. Vincente, the SW tip of the Iberian Peninsula. The instruments operated for a period of four months during the summer 2022, from 150 m to near-surface, 150 m, and 200 m, respectively. A time series of high resolution (2 Hz) and high temporal density (5-6 profiles/hour) of vertical profiles of temperature, salinity, Chla, turbidity and dissolved oxygen was acquired, along with the vertical description of the horizontal velocity. During a five days period in June, an abrupt temperature and salinity increase was detected at depths between 20-140 m, appearing as a “blob” of a water mass from a different origin, resembling the signature of Mediterranean Outflow Water (MOW). Furthermore, a decrease in chlorophyll concentration was observed in this period, an indicator for MOW. Ahead, an increase in westward current from averaged 0.09 ms-1 to 0.39 ms-1 was observed, followed by a sudden change in direction towards the east at the time of the event, suggesting the appearance of a shallow eddy carrying MOW in its core. A vein of MOW, leaning the continental slope, was identified before at depth as shallow as 350 m in the region. However, the observation of MOW at such upper layers was never experienced.

Our findings suggest that a sub-mesoscale eddy detached from the shallow vein of MOW, shoaling upwards the continental slope, reaching  the upper 20-140 m layer. The rough topography, such as the Portimão Canyon, as well as the Ekman suction, characteristic of the enhanced upwelling center off Cape St. Vincent, are the major candidates to explain this feature, and must be further investigated. The moored observatory south of Cape St. Vincent offers great opportunities to acquire long-term and continuous water column data, able to capture sudden events such as the one described here, and provides valuable datasets for model validation.

How to cite: Rautenbach, S. A., Mendes de Sousa, C., and Relvas, P.: High resolution observations of the ocean upper layer south of Cape St.Vincent, western Gulf of Cadiz: What they reveal, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6430, https://doi.org/10.5194/egusphere-egu23-6430, 2023.

X5.337
|
EGU23-7138
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OS2.2
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ECS
|
solicited
|
Ta Wei Lin, Wen Kai Weng, and Bo Jun Wang

The main purpose of this research is to use the boundary element method to establish a three-dimensional numerical model to simulate the stability and wave resistance of the structure based on the application of floating breakwater with pneumatic chamber.
From the two-dimensional numerical model and experimental results, it is found that the pneumatic chamber under a floating body can make the floating body give a resistance force when waves are affected, and increase the ability of the floating body to resist waves.This research focuses on the difference in stability and anti-wave effects under this influence.
 Numerical simulation is based on small amplitude wave theory, constructing numerical model with three-dimensional boundary element method, discussing the Response Amplitude Operators (RAO) of the structure under the action of waves.

How to cite: Lin, T. W., Weng, W. K., and Wang, B. J.: Research on motion characteristics of floating breakwater with pneumatic chamber, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7138, https://doi.org/10.5194/egusphere-egu23-7138, 2023.

X5.338
|
EGU23-14970
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OS2.2
|
ECS
|
Yaiza Samper, Maria Liste, Marc Mestres, Jose Alsina, Manuel Espino, and Agustin Sánchez-Arcilla

In this paper, we use observations and numerical simulations to investigate the effect of meteorological parameters such as atmospheric pressure and wind on harbours water exchanges. Knowing these water exchanges is of vital importance to care for and improve the environmental health of the harbor water and its surrounding areas. This knowledge requires an analysis of different meteorological and hydrodynamic parameters from detailed and high definition studies. SAMOA (System of Meteorological and Oceanographic Support for Port Authorities) is a project developed by Puertos de Estado (PdE) in collaboration with several Spanish harbour authorities and Universities to provide enhanced meteorological and oceanographic information and services for harbour operations. In the framework of this project, the Maritime Engineering Laboratory (LIM/UPC) has developed a high-resolution numerical model for the forecasting ocean variables at coastal and harbour scales. The effectiveness of this model to reproduce the hydrodynamics in the ports is evaluated using meteo-oceanographic observations from different measurement campaigns during 2020 2021, and 2022 carried out in the ports. Firstly, this article analyses and validates the results of the SAMOA meteo-oceanographic prediction system in the ports of Huelva, Gijón and Cartagena (mesotidal and microtidal environments) and, secondly, based on the analysis of observations, it proposes the numerical analysis of different events with high renewal times. The data includes information on atmospheric pressure, wind, sea level and currents parameters. These variables are validated by visual matching of the time series of modelled data and observations, as well as by statistical analyses and correlations between model results and measurements. 

How to cite: Samper, Y., Liste, M., Mestres, M., Alsina, J., Espino, M., and Sánchez-Arcilla, A.: Influence of atmospheric forcings on water renewal in harbours., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14970, https://doi.org/10.5194/egusphere-egu23-14970, 2023.

X5.339
|
EGU23-8415
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OS2.2
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ECS
|
solicited
S. Hadi Shamsnia, Debora Bellafiore, Christian Ferrarin, and Marco Bajo

The Black Sea is one of the largest enclosed seas in the world. More than 160 million people live in its coastal areas and large rivers flow into it, as  the Danube, the Dniester, the Dnieper and the Don. The Danube river, located on the western coast, is the most important European waterway whose catchment area is shared by more than fifteen countries. Black sea coastal waters are also often characterized by high suspended sediment concentrations derived from coastal runoff and local sediment re-suspension from the river sources. Measuring coastal sediment transport in field situations is notoriously difficult and generally subject to great uncertainty, and model estimates are often used in practice. The specific objectives of the current study are to understand the present state of the western Black Sea, and to study current and wave dynamics with the assistance of state-of-the-art numerical models for simulating waves, currents, and their interactions with the sediment loads. We used the hydrodynamic model named SHYFEM, hard coupled with the Wavewatch III wave model for the current study, while the coupled Sedtrans05 model will be used in the future for sediment modeling. The numerical models are applied on an unstructured grid representing the western Black Sea and the Danube Delta through the use of triangular elements of different shapes and sizes.

The simulations of the coupled SHYFEM-WW3 were compared with the significant wave heights (Hs) measured by the Jason-3 and Sentinel-3. Despite some discrepancies, SHYFEM-WW3 provides good agreements with the altimeter data. The preliminary comparison done on the basin scale application show better performance of the model for the western area (Correlation coefficient = 0.89 in the western Black sea, while Correlation coefficient = 0.81 in the basin scale). Next steps will be dedicated to a coastal application on the western Black Sea coupling circulation, waves and sediment transport.

All of the modeling activities are developed within the framework and funded by the Horizon 2020 DOORS (Developing Optimal and Open Research support for the Black sea) project, (Grant no. 101000518) https://www.doorsblacksea.eu/.

How to cite: Shamsnia, S. H., Bellafiore, D., Ferrarin, C., and Bajo, M.: Numerical investigation of the coastal dynamics over the western Black sea, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8415, https://doi.org/10.5194/egusphere-egu23-8415, 2023.

X5.340
|
EGU23-9068
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OS2.2
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ECS
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solicited
|
Ashly Kalayil Uthaman, Tomasz Dabrowski, Gerard McCarthy, and André Düsterhus

Our coasts face huge challenges due to future sea level rise. A main reason for this are the changes in waves which are expected to become more powerful. As these changes will affect our coasts, the prediction of wave changes play an important role in coastal adaptation and in industries like offshore wind energy. Ireland's extended coastline and its vulnerability to extreme wave events make it crucial to understand wave climate and its changes around the Irish coast.

The DeWaPic project intends to create a model framework for predicting waves around Ireland on time scales of seasons to decades. For this a global wave model, WAM, will be forced by climate model data and then coupled to a regional wave model, SWAN. In a next step the output of this model chain will be used to force a SURF zone model, with the target to generate information on coastal wave heights and wave overtopping.

This contribution will present the development of a 1-D SURF zone model, covering the final stretch towards the coast. The model solves one dimensional Boussinesq equation using a two step Lax Wendroff TVD scheme. The depth integrated approach in the model reduces the computational complexity that occurs when the grid size becomes smaller. Surface elevation and depth averaged velocity is modelled using the continuity and momentum conservation equations. We show first experiments with this model and determine in sensitivity tests its applicability.

How to cite: Kalayil Uthaman, A., Dabrowski, T., McCarthy, G., and Düsterhus, A.: A 1-D model for predicting surf zone waves around the Irish Coast, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9068, https://doi.org/10.5194/egusphere-egu23-9068, 2023.

X5.341
|
EGU23-9307
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OS2.2
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solicited
Antonio Bonaduce, Nam Pham, Joanna Staneva, Sebastian Grayek, Roshin P. Raj, and Øyvind Breivik

The effect of wave-induced processing on steric sea-level is investigated through ocean-wave coupled simulations. The experiments are performed with a high-resolution configuration of the Geestacht COAstal model SysTem (GCOAST), implemented in the Northeast Atlantic, the North Sea and the Baltic Sea which are considered as connected basins. The GCOAST system accounts for wave-ocean interactions and the ocean circulation relies on the NEMO (Nucleus for European Modelling of the Ocean) ocean model, while ocean-wave simulations are performed using the spectral wind wave model WAM. The objective is to quantify the sea-state contribution to steric sea-level variability and trend over a 26-year period (1992-2017). The ability of wave-ocean coupled simulations to disclose the sea-state contributions to sea-level variability and surge is demonstrated. The contribution of the wave-induced processes (WIPs) to the sea surface dynamics (e.g. temperature and salinity), ocean mixing (mixed layer thickness), and on the modulation of air-sea fluxes (e.g. heat flux) clearly appear both during winter (10-20 %) and summer (10 %), which in turn affect the steric sea-level variability. Investigating the components of steric sea-level signal, the thermosteric sea-level shows larger amplitudes compared to the halosteric component. Significant contributions to the thermosteric sea-level variability (40 %) due to wave-induced processes are observed in the North Atlantic (in summer) and along the Norwegian Trench (in winter). WIPs influence the thermosteric sea-level trends in the North Atlantic up to the order of 1 mm yr-1, both during winter and summer, in the open ocean and at the shelf break, while smaller contributions are observed over the shelf areas of the North Sea.

How to cite: Bonaduce, A., Pham, N., Staneva, J., Grayek, S., Raj, R. P., and Breivik, Ø.: Sea state contribution to steric sea-level, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9307, https://doi.org/10.5194/egusphere-egu23-9307, 2023.

X5.342
|
EGU23-10388
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OS2.2
|
ECS
|
solicited
Young Shin Kwon, Hyoun-woo Kang, Dong Han Choi, Jae Hoon Noh, Yeonjung Lee, and Ok Hee Seo

The large marine ecosystems (LMEs) are described as regional units for the marine research, monitoring, and management. The Yellow Sea (YS), located between Korean Peninsula and continental North China, is known as one of the most important LMEs in the world due to its high biodiversity and complex food web dynamics. Yellow Sea Cold Water Mass (also called YSCWM) formed by the remnant of winter cold water (<~11 °C) in the central Yellow Sea remains throughout the summer, which is a striking hydrological phenomenon in the Yellow Sea and has important effects on the marine ecosystem. Against this background, we undertook a modelling study as a part of a research program of Korea Institute of Ocean Science and Technology (KIOST) to improve the understanding of the ecosystem structure and function and the physical-biological processes in the YS and to predict changes in the the fishery resources under future climate change scenarios. First of all, we applied the 1-dimensional marine ecosystem model (ERSEM-GOTM) to the station (35°N, 124°E) near the central YS affected by the YSCWM. Some inconsistencies between the model and the observations were founded: For examples, while primary production and bacteria carbon mass were overestimated in the model, the zooplankton carbon mass remaining high even after summer season were not represented, which shows clearly the need for model improvements to better capture the cycling of the YS biogeochemistry. Here we present the evaluation of the main aspects of the model behavior and discuss how we optimize the model performance for proper representation of the YS system.

How to cite: Kwon, Y. S., Kang, H., Choi, D. H., Noh, J. H., Lee, Y., and Seo, O. H.: Assessment of 1-dimensional marine ecosystem model in reproducing the seasonal patterns in the Yellow Sea Large Marine Ecosystem, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10388, https://doi.org/10.5194/egusphere-egu23-10388, 2023.

X5.343
|
EGU23-10802
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OS2.2
|
ECS
|
solicited
Deoksu Kim, Hojin Kim, and Jae-Il Kwon

Many studies have focused on detecting coastal upwelling off the southeastern coast of Korea. Frequent occurrences of coastal upwelling are attributed to the persistent southwesterly (alongshore) wind blowing in the boreal summer season by the East Asian summer monsoon, reducing the surface water temperature by more than 5oC. Not just coastal upwelling cause variations in hydrodynamics, but it also gives rise to the primary production augmentation by phytoplankton blooms due to the supply of nutrients and fishery industry damage owing to sudden changes in water temperature. Accordingly, optimal coastal upwelling detection plays a crucial role in helping the augmentation of primary production and preventing industrial damage. Even though upwelling indices for detection are suggested, it would be inadequate to represent coastal upwelling compared with in-situ water temperature off the southeastern coast of Korea. Thus, we suggest upwelling-driven cold-water detection based on time-series observation, especially for real-time applications. By removing seasonal trends, we can define that an anomaly in sea surface temperature has occurred when the water temperature is out of natural variability (> 1σ). Furthermore, the suitability of the cold-water index was evaluated through an analysis between the index and the prerequisite when upwelling occurred, such as alongshore wind stress, wind duration, and vertical stratification.

How to cite: Kim, D., Kim, H., and Kwon, J.-I.: Quantifying Coastal Upwelling Index in the Southeastern Coast of Korea, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10802, https://doi.org/10.5194/egusphere-egu23-10802, 2023.

X5.344
|
EGU23-10876
|
OS2.2
|
solicited
Dongha Kim, Seung-Woo Lee, Jin-Yong Jeong, and Sung-Chul Jang

The marine physical characteristics occurring around the underwater reef in waters more than 100 km away from the land were analyzed through computational fluid dynamics (CFD). A fixed jacket structure so-called Ieodo Ocean Research Station (I-ORS) for marine and atmospheric observations is installed on this underwater reef, and marine observation data have been continuously produced for 20 years. However, there is a concern that observation data may be affected by the underwater reef. We built a numerical modeling framework based on observational data and analyzed the results to find out how underwater reef affects I-ORS. As a result, it was confirmed that various marine physical characteristics (wake region, local upwelling region, suspended sediments, vortex shedding, etc.) appear around the underwater reef. Especially, particle analysis was performed considering the tidal cycle and density stratification to identify the mechanism of suspended sediments generation. Consequently, we were able to find a pattern for the diffusion of suspended sediments around the underwater reef and it is possible to understand various marine physical characteristics around the underwater reef.

How to cite: Kim, D., Lee, S.-W., Jeong, J.-Y., and Jang, S.-C.: A study on marine physical characteristics around an underwater reef using computational fluid dynamics, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10876, https://doi.org/10.5194/egusphere-egu23-10876, 2023.

X5.345
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EGU23-11643
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OS2.2
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ECS
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solicited
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Sara Sirviente, Marina Bolado-Penagos, Juan Jesús Gomiz-Pascual, and Miguel Bruno

Studies about the coastal circulation over the northern continental shelf of the Gulf of Cadiz, based on current velocity observations, were published on relatively recent dates (e.g., Relvas and Barton, 2002). Since then, a considerable number of articles have been written dealing with this subject up to the present date (e.g., Oliveira et al., 2022). One of the most studied features in these studies are the so-called Coastal Counter Currents (CCCs) in the coastal shelf. These features are located roughly between the 100 m isobath and the coastline, and they are directed toward west. Nevertheless, despite the considerable number of articles devoted to the analysis of this phenomenon, the actual along-coast extension and origin of these CCCs remain unclear.

In the present contribution different mechanisms that have been already proposed to explain the development of these CCCs are revised and discussed. For this purpose, an analysis based on surface currents derived from High Frequency Radar (HFR) and numerical model simulations has been carried out.  The most interesting finding is that the most intense CCCs events are initiated on the coastal margin of the westernmost side of the Strait of Gibraltar, and they are extended further west of Cape Santa Maria. Also, these intense and extensive CCCs are triggered by the joint action of local winds over the Gulf of Cadiz and additional remote effects. This study highlights the importance of different remote effects: (i) the wind forcing over the Alboran Sea and the easternmost side of the Strait of Gibraltar, and (ii) the sea level atmospheric pressure forcing over the Ligurian Sea. This mechanism has been demonstrated from both statistical analysis and numerical experiments which allow us to understand the coupling between the horizontal and transverse pressure gradients, causing a geostrophic adjustment of the current against the coast.

References.

De Oliveira- Junior, L., Relvas, P., Garel, E. Kinematics of surface currents at the northern margin of the Gulf of Cádiz. Ocean Science,18,1183-1202,2022.

Relvas, P., and Barton, E. D., Mesoscale patterns in the Cape São Vicente (Iberian Peninsula) upwelling region, J. Geophys. Res., 107( C10), 3164, doi:10.1029/2000JC000456, 2002.  

How to cite: Sirviente, S., Bolado-Penagos, M., Gomiz-Pascual, J. J., and Bruno, M.: Coastal circualtion over the Gulf of Cadiz continental shelf. Local vs remote effects., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11643, https://doi.org/10.5194/egusphere-egu23-11643, 2023.

X5.346
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EGU23-11878
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OS2.2
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solicited
Seung-Buhm Woo, Hye Min Lee, Jong Wook Kim, and Byung Il Yoon

Many estuaries have been damaged by material movements like marine debris, suspended sediment, and pollutants. Understanding the estuarine circulation system is necessary to solve such problems. The salt transport analysis provides hydrodynamic processes about material circulation in the estuary. In this study, to understand the mechanisms of salt transport, a three-dimensional hydrodynamic model was applied in the hyper-tidal estuary system, Yeomha Channel, Gyeonggi Bay. The simulation period of the model was a total of 245 days (January 20 to September 20, 2020), including the dry and wet seasons. The model results for the temporal variation of tide, current velocity, and salinity were validated by comparing them with the observed in-situ data. The salt transport (FS) was calculated in three cross-sections of the Yeomha Channel and was decomposed into three components (QfS0: advective salt transport; FE: steady shear dispersion; FT: tidal oscillatory salt transport). During the dry season with strong tidal forcing, the salt transport patterns were mainly dominated by QfS0. During the wet season with large river discharge, the salt transport patterns were determined by the balance between QfS0, FE, and FT. The long-period tidal constituents (MSf and Mm) were the main mechanisms causing QfS0 with the spring-neap variation during the dry season. The tidal trapping effect, caused by the phase difference of less than 90° between tidal current and salinity, generated landward FT in the dry and wet seasons. In addition, the high river discharge during the wet season decreased the phase difference between tidal current and salinity to less than 70°, resulting in a much strong landward FT. This study suggests that the long-period tidal constituents and tidal trapping effect are unique characteristics that contribute to material circulation in the hyper-tidal estuary.

How to cite: Woo, S.-B., Lee, H. M., Kim, J. W., and Yoon, B. I.: Mechanisms of salt transport by the advective and tidal oscillatory flux in the macro-tidal estuary, Gyeonggi Bay in South Korea, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11878, https://doi.org/10.5194/egusphere-egu23-11878, 2023.

X5.348
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EGU23-10552
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OS2.2
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ECS
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Kunal Madkaiker and Devendra Rao Ambarukhana

The Indian subcontinent divides the north Indian Ocean (IO) into Arabian Sea (AS) and the Bay of Bengal (BoB), with different thermohaline properties. Seasonal reversal of winds and equatorial remote forcing due to proximity to equator, influences circulation of these basins. In this study, we numerically modelled the physical characteristics of AS and BoB, using MITgcm with a high spatial resolution of 1/20° (~ 5 km) and 49 vertical levels in a z-coordinate system, on a climatological scale. Temperature, salinity and flow fields were validated with satellite and gridded ARGO datasets. Statistically we established that the model setup simulates the upper ocean features and subsurface circulation in these two basins well.

Then, we computed the alongshore volume, heat, and freshwater transport along the coastline of India and eastern Sri Lanka. We observed that the alongshore transport along the eastern coast is stronger with high seasonal variability due to the poleward flowing Western Boundary Current (WBC) and equatorward flowing East Indian Coastal Current (EICC). The west coast transport is influenced by intraseasonal oscillations. We computed the freshwater transport to be an order less than the volume transport. Seasonality of alongshore volume and freshwater transport contradicts each other on the western coast whereas they are in phase on the eastern coast. Then we computed the contribution of freshwater transport in total flow as a percentage of the total volume transport. In the BoB, this is maximum during JJAS season which is limited to the northeastern coast of India, followed by October-November season as it covers the entire east coast. We also observed a weak and narrow freshwater export pathway flowing across the Palk Strait into the Gulf of Mannar. The seasonality of transport and upper ocean salinity highly correlate to each other in this region.

Meridional heat transport (MHT) was also computed over AS and BoB. Analysis shows that MHT over AS is stronger than BoB. Both basins act as heat source during summer monsoon and heat sink during winter monsoon. Zonal transport correlates positively with zonal wind whereas meridional transport correlates negatively with meridional wind. Various factors such as wind reversal, Ekman transport and vertical thermal wind shear play a role. Net heat flux positively correlates with total heat transport along the eastern coast of India and southeastern AS. It can be attributed to coastal currents and equatorial forcing which help in advection of heat and thermal ventilation.

Understanding the effects of these exchanges on nutrient and carbon transport along the coastal waters via nearshore processes would be aided by further research into these interactions. The high-resolution climatological set-up lays the groundwork for additional research into the physical and biological processes occurring in the Indian coastal seas.

How to cite: Madkaiker, K. and Ambarukhana, D. R.: High-resolution numerical modelling of seasonal volume, heat, and freshwater transport along the Indian coast, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10552, https://doi.org/10.5194/egusphere-egu23-10552, 2023.

X5.349
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EGU23-12529
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OS2.2
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ECS
Moein Doost Mohammadi, Michele Bolla Pittaluga, Marcello Gatimu Magaldi, and Andrea Mazzino

A three-dimensional Regional Ocean Modelling System (ROMS) has been implemented to investigate hydrodynamic circulation patterns in the Northern Mozambique Channel and their role on turbidity current generation and sediment distribution in the submarine canyons. A high-resolution (~ 100m) bathymetry data of the Palma Bay and its offshore area was blended with a global gridded bathymetry (GEBCO) with 15 arc-seconds (~ 400m) resolution to cover the area of interest. Our main goal is to better understand deeper currents in the Mozambique Channel that are less well-established, and their ability to transport seabed sediment, by means of analysis of water structure according to T-S diagrams. There are debates on existence of some specific oceanographic features and unanswered questions regarding origins of the passing mesoscale eddies which dominate the circulation in the Mozambique Channel. Furthermore, we are also interested in knowing the effects of the presence of submarine canyons on adjacent canyons and their contribution to the circulation patterns and other physical processes in the area. Preliminary results highlight the importance of small-scale features for the circulation in area of interest.

How to cite: Doost Mohammadi, M., Bolla Pittaluga, M., Magaldi, M. G., and Mazzino, A.: Numerical simulation of ocean currents in the Northern Mozambique, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12529, https://doi.org/10.5194/egusphere-egu23-12529, 2023.

Posters virtual: Tue, 25 Apr, 08:30–10:15 | vHall CR/OS

Chairpersons: Davide Bonaldo, Sandro Carniel, Manuel Espino Infantes
vCO.8
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EGU23-4784
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OS2.2
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ECS
Peng Li and Shenliang Chen

Suspended particulate matter (SPM) is the primary component of coastal waters. The spatiotemporal dynamics of SPM has an important influence on water bio-optical properties, pollutant diffusion, landform evolution, and carbon, oxygen, and nutrient cycles. This study presents the spatial distribution of monthly average SPM concentrations from 2017 to 2020 in the abandoned Diaokouhe and Shenxiangou distributary mouths of the Yellow River Delta (YRD). The SPM concentrations were derived based on 161 Landsat-8 OLI and Sentinel-2A/B MSI satellite images. Accuracy assessment using the synchronous in-situ measurements (R2= 0.91, root mean square error (RMSE) = 38.79 mg/L, and relative percentage difference (RPD) = 23.45%) and cross comparison between SPM concentrations derived from the two sensors (R2= 0.97, RPD = 8.77%) showed convincing performances. Our results show that the monthly average SPM is characterized by significant seasonality, with a higher concentration and wider range in dry seasons compared to that in wet seasons. The spatial distributions of SPM are closely associated with coastal water depths. The SPM concentration in the Shenxiangou mouth is always lower than that of the shallower Diaokouhe mouth. The long-term seabed erosion provides a continuous supply of sediment. Wind-wave forces explain the seasonal variations of SPM by inducing the resuspension of bottom sediments. The residual currents control the transportation of SPM to the offshore and to the east. The artificial groins located between the two river mouths show obvious sediment trapping effects. Moreover, the interception capability of impermeable groins is considerably better than that of permeable groins.

How to cite: Li, P. and Chen, S.: Combining Landsat-8 and Sentinel-2 to investigate seasonal changes of suspended particulate matter off the abandoned distributary mouths of Yellow River Delta, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4784, https://doi.org/10.5194/egusphere-egu23-4784, 2023.

vCO.9
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EGU23-11282
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OS2.2
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ECS
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Pawan Tiwari, Ambarukhana Devendra Rao, Smita Pandey, and Vimlesh Pant

     India is frequently affected by coastal flooding due to storm surges that significantly effects human lives, coastal infrastructure, and marine ecosystem. Tropical cyclones (TCs) are the most severe storms especially over the Bay of Bengal (BoB) and the Arabian Sea (AS). The vulnerability from the TCs occurs in many ways, which include coastal inundation by extreme water levels, damage of coastal properties caused by strong cyclonic winds, additional flooding caused by cyclone-induced heavy precipitation. The destruction along the coast due to inundation enhances if the cyclone makes landfall near the estuaries, river deltas, or any adjoining rivers in the coastal area. Simulation of inland flooding requires accurate representation of topography and surface roughness over the flood plain. Incorporating Land Use/ Land Cover (LULC) data in numerical simulations help in introducing roughness which alter the cyclonic wind speed over land. This also enhances model capabilities to represent accurate wind during the cyclone period. In the present study, experiments are carried out to simulate extreme water elevations and associated coastal inundation for the recent TC, Yaas (2021) that occurred over the BoB using stand-alone ADCIRC (Advanced circulation) model coupled ADCIRC and SWAN (Simulating Wave Nearshore) model. High-resolution mesh is used to incorporate major river systems and water bodies. Various datasets like Airborne DEM, CARTOSAT-DEM, SRTM-DEM, MIKE-CMAP, and ETOPO-2 are used to prepare the model mesh. The results show that total inundation calculated by the coupled model is higher since the SWAN model gives an extra momentum flux to the ADCIRC model in the form of radiation stress gradient. This results generation of maximum water elevations in the coupled model. As the TC approaches over the land, wind intensity gets reduced due to the presence of different land covers, which have specific roughness lengths. The more the roughness length, higher will be the reduction in the wind speed. To observe modifications in the wind speed over the land and ocean, ERA-5 reanalysis data is used for the 1999 Orissa super cyclone, Hudhud (2014), Amphan (2020), and Nivaar (2020). The results show a reduction of 38.2%, 35.62%, 16.35%, and 29.58% in wind speed at the time of landfall over the land compared to that of over the ocean for the above cyclones respectively. Using standalone ADCIRC and coupled ADCIRC+SWAN model, the simulations are made for TC Vardah (2016) to study the impact of roughness length over the wind intensity based on LULC. The results suggest that there is a significant decrease in the wind intensity over land after modifying the roughness length.

How to cite: Tiwari, P., Rao, A. D., Pandey, S., and Pant, V.: Effect of roughness length using LULC on the wind intensity of tropical cyclones and its associated inundation, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11282, https://doi.org/10.5194/egusphere-egu23-11282, 2023.

vCO.10
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EGU23-7843
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OS2.2
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ECS
|
Simon Treillou and Patrick Marchesiello

The nearshore zone, including the surf zone and the inner shelf (up to about 20 m depth), is a particularly chaotic zone where processes with very different scales coexist and interact permanently. This very active region, which marks the transition from the continent to the sea, is of crucial importance in many aspects (beach erosion/accretion, dispersion of pollutants or larvae, users’ safety, etc.). Several studies have already looked at the transport of passive tracers in the nearshore zone, but they generally use depth-averaged models. As a result, little is known about the non-hydrostatic 3D processes governing the nearshore zone, while depth-averaged models struggle to accurately represent measured data. For example, they tend to underestimate transport in the surf zone and overestimate it on the inner shelf. Recently, 3D wave-resolving models with a free surface have been made available to researchers. One of these models, CROCO (Coastal and Regional Ocean Community model) is used here and allows the simulation of nearshore processes with a reduced number of unknown parameters. The model is applied to a large-scale dye release experiment in California (Imperial Beach, 2009), for which simulations with the depth-averaged funwaveC model have already been performed. The IB09 survey is ideal to study processes as the beach is almost alongshore uniform. Several diagnostics are performed, such as tracer mass balance or quantification of the exchange between the surf zone and the inner shelf. The diagnostics highlight the vertical shear and 3D instabilities at work in the nearshore zone and infer the ability of 3D wave-resolving models to adequately reproduce the available observations, particularly with respect to surf-shelf exchange. This work may in the future suggest feedback for better parameterization in coarser, simpler models for a more accurate depiction of coastal pollution fate and sediment transport.

How to cite: Treillou, S. and Marchesiello, P.: Impact of 3D non-hydrostatic dynamics on tracer transport in the nearshore region, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7843, https://doi.org/10.5194/egusphere-egu23-7843, 2023.