This session invites multi- and inter-disciplinary contributions focusing on coastal processes, their dynamic interactions, and their role in exchanges across coastal interfaces (e.g. land-sea, air-sea, river-sea, …) under a changing climate and changing human activities. We welcome observational, modelling and theoretical studies reporting on processes linked to coastal hydrodynamics, coastal biogeochemistry, coastal ecology, or coastal sediment dynamics and geomorphology. Studies may span the wide range of spatial and temporal scales characteristic of existing and projected change in coastal seascapes and landscapes from the inner shelf shoreward to beaches and dunes, estuaries, intertidal flats, saltmarshes and coastal wetlands. We encourage the submission of holistic Earth system studies that explore the role of the coastal zone for coastal seas’ dynamics including exchanges across coastal under the impact of climate change and human activities. We also encourage studies that focus on impacts of coastal management or coastal adaptation approaches on coastal processes and dynamics, spanning engineered, hybrid, and nature-based options related to changing activities such as coastal protection, tourism, shipping, fisheries and aquaculture, and the expansion of renewable energies and other coastal infrastructure.
Orals: Thu, 7 May, 08:30–12:25 | Room L3
The demand for marine aggregates, particularly sand, is rapidly increasing due to population growth and the need for climate change adaptation. While sand extraction supports many essential industries, it also generates substantial environmental impacts, including habitat degradation and coastal erosion, underscoring the need for effective regulatory frameworks. Previous studies suggest that nearshore sand mining can contribute to coastal erosion; however, the impacts of sand mining pits at different water depths remain poorly quantified and are often addressed only qualitatively.
This study investigates the influence of water depth on sand pit morphodynamics and the long-term evolution of mining pits. Bathymetric datasets acquired between 2017 and 2024 from the Korea Hydrographic and Oceanographic Agency (KHOA) were analyzed for multiple sand mining pits located within the 25–65 m isobaths. Results show that pit recovery rates varied following three years of intensive mining. Linear regression between water depth and mean depth change revealed a weak but consistent negative relationship (R² = 0.40), indicating reduced sediment deposition with increasing depth, likely due to decreasing bed shear stress and sediment mobility.
These findings suggest that sand mining at greater depths may reduce morphological impacts on surrounding seabed areas, highlighting water depth as a critical factor in site selection and pit design. Because wave-induced bed shear stress is stronger in shallower waters, this study provides quantitative evidence to support depth-based guidelines for sustainable sand mining and informs future policy development.
How to cite: Lee, G., Abdul-Kareem, R., Chang, J., Harris, C., and Lee, J.: Morphodynamic evolution of depth-dependent sand mining pits and implications for sustainable sand mining, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16377, https://doi.org/10.5194/egusphere-egu26-16377, 2026.
Tropical coastal shelf ecosystems are shaped by strong seasonal atmospheric forcing and intense human exploitation. However, the links between physical oceanographic variability and fisheries dynamics remain poorly understood, particularly in data-limited regions. In the Philippine seas, seasonal changes in wind forcing and upper-ocean conditions influence stratification, mixing, and productivity, with potential consequences for demersal fish communities exploited by bottom trawl fisheries. This study investigates how seasonal oceanographic variability relates to patterns in catch and catch per unit effort (CPUE) of an otter trawl fishery in the Visayan Sea, central Philippines. Fisheries-dependent observations, including depth-stratified CPUE and species composition are integrated with environmental parameters derived from atmospheric reanalysis and gridded ocean datasets. Seasonal atmospheric forcing is characterized using surface wind fields, while ocean surface and upper-layer conditions are described using sea surface temperature (SST), temperature anomalies, and productivity proxies. To match the temporal resolution of the fisheries data, analyses focus on contrasts between the wet and dry seasons. Seasonal differences in catch patterns and community composition are examined in relation to environmental variability. Life-history traits are used as an interpretative framework to explore whether seasonal environmental regimes and trawling pressure may differentially affect species with contrasting growth and reproductive strategies. By combining atmospheric forcing, shelf-scale oceanographic processes, and fisheries obervations, this study highlights the role of physical-biological coupling in mediating the impacts of climate variability and human activities on demersal fisheries. The findings aim to contribute to a process-based understanding of coastal fisheries dynamics in tropical shelf systems and demonstrate the value of interdisciplinary approaches for studying coupled ocean-human systems.
How to cite: Morales, C. J., Cruz, R., and Babaran, R.: Seasonal atmospheric forcing and shelf-scale oceanographic variability shapes demersal trawl fisheries in the Visayan Sea, Philippines, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12131, https://doi.org/10.5194/egusphere-egu26-12131, 2026.
Understanding the dynamic drivers of the marine carbon cycle is essential for predicting how human activities shape ocean-atmosphere CO2 fluxes in a changing climate. Bottom trawling disturbs natural carbon flows through sediment resuspension. However, the impacts of bottom trawling-induced resuspension on air-sea CO2-exchange remain uncertain due to the complexity of the underlying processes involved. To address this, we used a 3D coupled physical-biogeochemical model SCHISM-ECOSMO-CO2, including a carbonate chemistry module, to investigate the impacts of bottom trawling-induced resuspension on the North Sea's carbon cycle. We estimate the impacts for the period 2000-2005 using two model simulations: one accounting only for natural resuspension and another incorporating a parameterization for bottom trawling-induced resuspension. For the latter, we integrate detailed fishing activity data, including vessel position, size, fishing gear type, and engine power to generate daily forcings for trawling-induced resuspension. The results show that bottom trawling causes small, spatio-temporally varying changes in particulate organic carbon (POC), dissolved inorganic carbon (DIC), and air–sea CO2 fluxes, driven by the interplay of remineralization, productivity, and material transport. In the North Sea, CO2 outgassing increases in shallow, mixed regions, while deeper, stratified areas experience enhanced CO2 uptake. At the basin scale, these opposing effects balance through carbon fixation and respiration, resulting in a small net increase (~0.0013 molCm-2yr-1) in oceanic CO2 uptake. These results indicate that shifts in biological carbon pathways, rather than physical disturbance alone, dominate the ecosystem response to bottom trawling.
Keywords: Carbonate, Air-sea flux, North Sea, bottom trawling, remineralization.
How to cite: Tiwari, P., Porz, L., Daewel, U., Liu, F., Kossack, J., Demir, K., Zhang, W., and Schrum, C.: Bottom Trawling Effects on Air–Sea CO₂ Exchange: A Modeling Study of the North Sea, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9635, https://doi.org/10.5194/egusphere-egu26-9635, 2026.
Upwelling and downwelling are common phenomena in the Baltic Sea, significantly altering the thermal balance and water mass properties, with consequences on biological activity and biogeochemical cycling. While upwelling has been extensively studied using remote sensing and modelling, downwelling remains comparatively poorly documented, partly due to the challenges of direct measurements. Improving understanding of downwelling events is crucial for assessing their impact on biological processes and particle dynamics. This study presents novel in-situ observations of coastal downwelling events in the southern coast of Finland using two benthic landers, complemented by ocean reanalysis dataset.
A 41-day deployment (August–September 2024) and 70-day deployment (August-October 2025) were conducted where a benthic lander recorded flow velocity and particle concentration throughout the bottom meter of the water column, along with salinity, temperature, and oxygen and chlorophyll concentrations. Data was collected at high temporal resolution, with instruments recording every 6 hours or more frequently.
Under typical conditions, we measured a weak downward flow and low horizontal velocities (mean 2 cm s-1), with 20µL L-1particle concentrations. Chlorophyll concentrations were low (<0.08 RFU), and oxygen concentration remained stable at approximately 190 μmol L-1. In contrast, distinct downwelling events were observed in September 2024 and September 2025, which were characterized by increased downward flow velocities and particle concentrations, accompanied by concurrent increases in temperature, chlorophyll, and oxygen in the benthic layer. These signals indicate episodic advection of surface-influenced water masses to the seafloor.
We identified 85 downwelling events in this region since 1993 using the Baltic Sea Physical Reanalysis product from CMEMS, with an apparent increase in event duration and maximum bottom temperature over time. During 2016-2020, 46% of these events meet criteria commonly used to define marine heatwaves. Although the area is typically classified as an upwelling region, our results demonstrate that downwelling events are also frequent and may play an important role in benthic environmental variability and the influx of warmer, nutrient-rich surface water to the seafloor may enhance oxygen consumption and greenhouse gas production. These findings highlight the need to account for downwelling processes when assessing future ecosystem responses in the context of climate change, where changes in wind forcing may modify upwelling and downwelling frequency and intensity, with cascading ecological consequences.
How to cite: Poizat, M., Virtasalo, J., Asmala, E., Lemke, J., Spilling, K., Wasiljeff, J., Attard, K. M., and Koho, K.: Beyond upwelling : frequent coastal downwelling events and their benthic impact in the southern coast of Finland (Baltic Sea), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2518, https://doi.org/10.5194/egusphere-egu26-2518, 2026.
Coastal areas are dynamic environments shaped by the interplay of waves, sediment supply, and human activities, making them highly sensitive to environmental change. One of the most vulnerable coastal systems are deltas, where dam construction along river courses has significantly reduced sediment delivery to delta fronts, and coastal infrastructures have altered natural dynamics. This study investigates the multi-decadal shoreline evolution of three large wave-dominated deltas along the Catalan coast (NW Mediterranean Sea) from 1984 to 2025: Tordera, Llobregat, and Ebro.
In this study, we used the CoastSat toolkit to analyze historical Landsat 5, 7, 8, and 9 (at 15 m resolution) together with Sentinel-2 imagery (at 10 m resolution) to extract shoreline positions. This multi-sensor approach enables the detection of long-term shoreline trends while also capturing seasonal and event-driven variations.
Our work highlights differential patterns of shoreline change across the adjacent deltas beaches. The results reveal the timing and magnitude of seasonal erosion and accretion processes, providing insight into short-term dynamics that are not evident in annual assessments. This integrated dataset demonstrates the value of combining multi-sensor satellite data with automated shoreline extraction tools for continuous monitoring of coastal evolution. Our findings contribute to the understanding of deltaic responses to wave climate, sediment supply, and human impacts, offering a robust framework for future coastal management and risk assessment strategies in Mediterranean wave-dominated delta systems.
This work has received funding from EBRO-CLIM research project PID2024-155310OB-I00 financed by MICIU/AEI/10.13039/501100011033/FEDER, UE.
How to cite: Calvillo, B., Pavo-Fernández, E., Peñas-Torramilans, R., Gracia, V., and Grifoll, M.: Satellite-Based Analysis of Shoreline Evolution along Wave-Dominated Deltas of the Catalan Coast (1984–2025): From Annual to Monthly Temporal Scales, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9412, https://doi.org/10.5194/egusphere-egu26-9412, 2026.
The central west coast of India presents a dynamic coastal environment where geomorphic evolution is governed by a complex interplay of monsoonal forcing, sea-level fluctuations, and human interventions. This study unravels the morphodynamic behavior of embayed beaches across seasonal, decadal, and millennial timescales using an integrated approach that combines field observations, satellite-based shoreline analysis, and paleo-geomorphic reconstructions. Twenty-seven embayed beaches were systematically classified using an embayment morphometric parameter (γe) derived from the embayment area (Ae) and indentation (a), enabling their categorization into open, semi-exposed, and sheltered systems. Field measurements from sixteen representative beaches revealed a pronounced seasonal rhythm driven by the southwest monsoon. Between February 2023 and September 2024, beach profiles and sediment texture analyses indicated distinct monsoon-induced erosion–accretion cycles. Coarser and better-sorted sediments (mean 0.6–4.84 Φ) accompanied high-energy wave conditions and volumetric losses averaging –32.16 m³/m, while post-monsoon periods favoured the deposition of finer, poorly sorted sediments (0.8–4.1 Φ) and volumetric gains averaging +28.61 m³/m. These observations suggest that even morphodynamically semi-isolated embayments respond synchronously to regional wave energy fluctuations, reflecting a delicate balance between hydrodynamic forcing and sediment supply.Extending the temporal perspective, multi-decadal shoreline analyses (1990–2023) derived from remote sensing data revealed spatially variable responses to climatic and anthropogenic drivers. Correlation with rising sea levels, increasing cyclone frequency, and intensifying wave power suggests that regional climate change has accelerated erosion processes. Additionally, the construction of breakwaters and jetties has disrupted longshore sediment transport, intensifying localized shoreline instability.
To place these short-term observations within a broader evolutionary context, paleo-shoreline reconstruction was carried out using geomorphic proxies such as paleo beach ridges, wave-cut terraces, and topographic and hydrographic sinuosity indices derived from high-resolution SRTM DEMs. The reconstruction reveals that around ~12-10ka BP, when sea level stood 80 m below mean sea level, the shoreline coincided with the present-day ~80 m bathymetric flat, advancing ~+4m landward during mid-Holocene (~6-5 ka BP) transgressive phases. Exploring paleoshorelines is critical as it unveils the imprint of post-glacial sea-level rise and tectonic adjustments, providing the millennial-scale context necessary to interpret modern coastal behavior and anticipate future shoreline trajectories under accelerating climate change also these ancient shoreline and beach-ridge formations are important to society and the economy as they can host valuable heavy mineral deposits and serve as reservoirs for groundwater.
Together, these insights portray a continuous narrative of coastal evolution from monsoon-driven sediment oscillations to decadal shoreline shifts and millennial transgressions highlighting the dynamic and interconnected nature of embayed beach systems along the central west coast of India. This multi-temporal framework enhances our understanding of coastal resilience and supports informed management of monsoon-dominated, morphologically sensitive coasts.
How to cite: Mishra, P. K., Murali R, M., and Dwivedi, D.: Decadal to Millennial Evolution of coastline along the Central West Coast of India: Integrating Field Observations, Remote Sensing, and Paleo shoreline Proxies , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-463, https://doi.org/10.5194/egusphere-egu26-463, 2026.
Serving as significant coastal ecosystems, mangroves and coastlines offer wide range of services and contribute majorly to the socio-economic persistence to the communities. Coastal zones of the Bhitarkanika region (encompasses Bhitarkanika mangrove), in the eastern coastal state of India, exhibit pronounced geomorphic instability driven by hydrodynamic forcing, sediment disequilibrium, and expanding anthropogenic activities. This study formulates an integrated geospatial framework combining Digital Shoreline Analysis System (DSAS), Coastal Vulnerability Index (CVI), and Binary Logistic Regression (BLR) to quantify shoreline dynamics and assess multi-hazard coastal vulnerability. Multi-temporal shorelines derived from Landsat-8 (2013) and Sentinel-2 (2016, 2019, 2022, and 2025) datasets, corrected for tidal variability and validated using Google Earth. The results revealed a predominantly erosional trend, with 87.80% of transect undergoing shoreline retreat and a mean erosion rate of –11.57 m yr⁻¹. Field observations corroborate approximately 174 m of sediment deposition in accretion zones and ~189 m of land loss across rapidly eroding around the mangrove tract. The CVI was developed using elevation, slope, land use land cover (LULC), proximity to shoreline, river, and road, wherein the parameter weights were computed through Principal Component Analysis (PCA), correlation, entropy weighting, and an Ensemble Weighted Model (EWM). The CVI-based outputs indicate that ~47% of the coastline falls within high to very high vulnerability zone, primarily influenced by low-lying terrain, fluvio-marine interactions, and intense human activities. The BLR-based model demonstrates strong predictive performance (accuracy> 85%) and statistically validates the CVI-based output (>75% spatial agreement). The BLR and ensemble-based approaches represents a robust, multi-criteria framework for coastal vulnerability assessment and critical high-risk zonation. The findings provide reliable spatial intelligence to support shoreline management, mangrove restoration strategies, and climate-resilience planning in the Bhitarkanika coastal system.
How to cite: Mukherjee, S., Tripathi, L., Veer, V., Das, P., and Naskar, S.: Geospatial Intelligence for Modelling Shoreline Dynamics in a Mangrove-encompassed Bhitarkanika region, Odisha, India, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-799, https://doi.org/10.5194/egusphere-egu26-799, 2026.
Coastal systems evolve through a wide variety of physical, ecological and human processes, operating over multiple timescales. One coastal type of interest is an unmanaged, soft-cliffed coast, where hydrodynamic, erosive and avalanching processes interact to create a dynamic and often rapidly receding coast. Anthropogenic sea level rise is expected to accelerate recession and cause cliff submergence, a transition in coastal typology, impacting local communities, habitats and infrastructure.
In this presentation, we explore the long-term (centuries and longer) geomorphological behaviour of a soft-cliffed coast forced by relative sea level rise. We describe continuous erosive processes by a generalised set of time-averaged hydrodynamic and erosion governing equations, driving smooth deformation of coastal morphology. This description is general enough to encompass many existing hydrodynamic and erosion models, meaning that results derived in this work hold for a large family of model parameters and parametrisations.
A key physical process on soft-cliffed coasts is collapsing of the cliff face. The timescale of collapsing is shorter than the time-averaged hydrodynamic and erosion timescales and can be treated as an instantaneous process. This jump in state means that the mathematical framework of non-smooth (or hybrid) dynamical systems must be used to explore the evolution of these coasts.
We identify two geomorphological states toward which the system converges: a repeatedly collapsing receding cliff system, approached when sea level is static, and a transgressing rocky platform without a cliff, approached for high rates of sea level rise. Our analysis focuses on the transitions between these attracting states over anthropogenic sea level rise scenarios. We find that cliff submergence can be characterised as a “tipping point” behaviour, reframing changes in coastal type as potentially irreversible impacts of anthropogenic climate change. This is an underexplored geomorphological phenomenon and may help us interpret the history of the Earth’s coastal systems, as well as explore future scenarios. The description of time-averaged hydrodynamic and erosion processes is general, strengthening the statement that the tipping point behaviour discussed is a realistic phenomenon, rather than a mechanism only seen for specific model parametrisations.
This work also impacts the modelling of human-coastal coupled systems, since some management decisions, e.g. beach nourishments and the erection of coastal defences may be treated as instantaneous processes, and the framework of non-smooth dynamical systems is one avenue towards understanding long-term system behaviour.
How to cite: Appleton, M., Briganti, R., and Dodd, N.: Exploring climate change induced geomorphological tipping points on soft-cliffed coasts, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5583, https://doi.org/10.5194/egusphere-egu26-5583, 2026.
A large proportion of the world’s population lives near the coast; as a result, extensive anthropogenic modification, including historic coastal landfills, has affected large swathes of the global coastline. The acceleration of climate change is poised to increase erosion and inundation that already disturb these sites and mobilise stored solid waste into the marine environment. Before 1974, UK landfill operators had no legal requirement to keep records, and thus the composition and condition of the solid waste at risk of release is unknown. Field sampling campaigns of historic coastal landfills in the United Kingdom have identified hazardous heavy metals, asbestos and plastics, alongside inert geomaterials such as rubble, glass and ceramics being released into the marine environment
A gap remains in our understanding of this hazard, as it is unclear how geomorphological and hydrodynamic processes affect the spatial pattern of solid waste. This creates a need to map, classify and quantify the release of solid waste and its subsequent environmental impact. Three landfills in England have been selected for a mapping and monitoring campaign: East Tilbury, Essex; Shoebury East Beach, Essex; and Spittle Lane, Dorset. These sites are located near areas of high population density or on urban estuaries with a range of industrial developments.
Through the synthesis of existing sediment and grain-size mapping techniques, geomorphic mapping approaches and concepts from citizen science litter surveys, a new framework has been developed to characterise and quantify solid waste physical characteristics. This approach has been extended, using images taken via a phone and UAV, to develop a model to automate the detection and classification of solid waste in coastal settings. These different mapping approaches have been developed through repeat field visits, which have resulted in the creation of different solid waste datasets at different spatial scales with different levels of information.
Different spatial patterns of waste are explored, identifying hotspots of waste accumulation, their geomorphic behaviour and impact, as well as the effectiveness of the automated mapping approach. The refined anthropogenic geomaterial classification scheme will be able to be applied to a wider range of sites around the UK coast, alongside the development of automated mapping approaches, which will allow stakeholders to track the release of solid waste and their impacts.
How to cite: Newman, B., Grieve, S., and Spencer, K.: Automated and manual mapping of solid waste characteristics on the foreshore of historical coastal landfill sites., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8211, https://doi.org/10.5194/egusphere-egu26-8211, 2026.
Defining literacy is essential because it establishes a baseline for education, enables robust assessment and measurement of progress, supports policy and accountability, makes domain-specific differences explicit, and can improve equity by enabling better-designed interventions to promote learning. UNESCO notes that, beyond its conventional concept as a set of reading, writing and counting skills, literacy is now understood as a means of identification, understanding, interpretation, creation, and communication in an increasingly digital, text-mediated, information-rich and fast-changing world. Consequently, multiple domain literacies have emerged, including science, health, media, digital and financial literacy, and more recently AI literacy. While ocean literacy has gained significant traction in the last decade, for the coast an early coastal literacy framework was proposed in 2010 by CoastNet (UK charity that has since closed), but it was primarily oriented towards integrated coastal zone management. The objective of this work is thus to define coastal literacy and what it comprises.
To develop a definition tailored to coastal contexts, related literacy constructs were reviewed, particularly ocean literacy, climate literacy and risk literacy. Across frameworks, literacy is commonly articulated through dimensions (for example, knowledge, awareness and attitudes) and, in some cases, through explicit principles. The Ocean Literacy Framework is a prominent example, currently comprising seven principles and 45 concepts, and defines ocean literacy as understanding the ocean’s influence on humanity and humanity’s influence on the ocean. Although coasts form part of the broader ocean system, coastal environments have distinct characteristics: they concentrate human activities, involve frequent and direct human–environment interactions, and are often exposed to hazards. Coasts also exist at the interface of multiple Earth system spheres, linking the ocean, land and atmosphere. The framework of coastal literacy was developed building on the literature review and on a two-day focus group using structured brainstorming methodologies. The proposed framework comprises seven principles: (P1) Each coast is unique and has value on its own; (P2) Coasts consist of many different and connected parts; (P3) Coasts are dynamic, changing from seconds to millennia; (P4) Human activities impact the coast, and coasts continually affect humans; (P5) Coasts are inherently hazardous environments that can place people and infrastructure at risk; (P6) Climate change is affecting coastal ecosystems and challenging future coastal use; and (P7) We share responsibility for looking after the coasts for present and future generations. A key contribution of these principles is how they frame human–coast relationships. They recognise the intrinsic coastal value independent of human use or resource exploitation (P1), position humans as part of coastal systems (P2, P4), explicitly foreground coastal risk (P5), and treat shared responsibility as a component of literacy (P7). They also embed sustainability by emphasising the need to safeguard future generations, including in the context of climate change (P6). Further work is needed to elaborate the concepts underpinning each principle and to refine the framework through additional validation; however, the principles presented here provide a structured foundation for defining and operationalising coastal literacy.
How to cite: Matias, A., Dann, L., Carrasco, A. R., Van Dongeren, A., Masselink, G., Ferreira, Ó., Loureiro, C., and Madiedo, A.: A principles-based framework to define coastal literacy, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20593, https://doi.org/10.5194/egusphere-egu26-20593, 2026.
The Greenland Ice Sheet is melting rapidly, increasing freshwater runoff to the coastal ocean around Greenland. Through this pathway, allochthonous material, including nutrients, sediments, and organic carbon, is transported to coastal waters. The impacts of these inputs on coastal carbon cycling are poorly resolved, and accelerating climate change prompts closer examination of the character and fate of allochthonous material reaching Arctic coasts. In this study, we have taken a closer look at quantity, quality, and transformation of organic matter (OM) in surface waters of an oligotrophic high Arctic fjord influenced by glacial and proglacial runoff. We examined dissolved, suspended, and sinking OM by combining in situ observations along a river-to-sea gradient with experiments quantifying bioavailable carbon fractions, production of transparent exopolymer particles (TEPs), and OM flocculation. We found that dissolved organic carbon (DOC) concentrations in glacial and proglacial river waters were comparatively low (<30 µM), suggesting that these inputs should dilute DOC concentrations in the fjord. At the same time, riverine DOC was at least two times more bioavailable than marine DOC. Non-conservative DOC mixing along the river-to-sea gradients further indicated additional DOC supply, which we hypothesize is due to desorption from inorganic particles.
Much of the riverine particulate OM (POM) was observed to sediment out within the first few kilometers upon entering the fjord, with salt-induced flocculation and, to some extent, TEPs formation contributing to efficient aggregation and sinking. The sinking POM flux included a distinct contribution from chlorophyll-containing particles, indicating that freshwater inputs enhance downward export of phytoplankton biomass. The coexistence of this export with low but steady chlorophyll standing stocks in the water column implies concurrent primary production that persists even under turbid low-light conditions.
Overall, our results highlight the complexity of coastal carbon cycling in a changing Arctic and demonstrate that glacial river plumes act as reaction zones for rapid and multidirectional transformations of OM. By resolving interactions among freshwater inputs, particle dynamics, and multiple OM pools along river-to-sea gradients, this study advances understanding of how increasing land-ocean connectivity reshapes carbon cycling and ecosystem functioning in the coastal Arctic.
How to cite: Mostovaya, A., Holding, J., and Lund Paulsen, M.: The fate of ice sheet-derived organic matter in an oligotrophic Greenland fjord, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20198, https://doi.org/10.5194/egusphere-egu26-20198, 2026.
Estuaries and similar coastal areas are among the most vulnerable ecosystems worldwide, facing environmental degradation due to anthropogenic pressures that demand a comprehensive evaluation of their historical trajectories. The study integrates benthic foraminifera, trace metals (Zn, Pb, Cd, and Hg), and short-lived radionuclides (210Pb and 137Cs) to reconstruct the environmental evolution of the heavily polluted Suances Estuary (N Spain). The investigation focuses on the estuary’s response to the cessation in 2003 of historical mining activities of one of Europe’s largest carbonate-hosted Pb-Zn ore bodies, the Reocín metalliferous deposit. A total of twenty-two surface sediment samples and a short sediment core (47 cm in length) were analyzed. Core samples revealed elevated concentrations of Zn (>10,000 mg kg⁻¹), Pb (max. 2700 mg kg⁻¹), Cd (35.3 mg kg⁻¹), and Hg (41 mg kg⁻¹), exceeding both local baselines and sediment quality guidelines. While a downward trend in surface metal concentrations was observed between 2003 and 2022, the documented spatial heterogeneity suggests ongoing sediment redistribution. Foraminiferal standing crops remain extremely low (1–510 living individuals per 80 cm³), indicating continued ecological stress. Although the Reocín mine was closed more than two decades ago and industrial discharges have been reduced, pollution likely remains as a significant obstacle to environmental recovery. Additionally, the sedimentary record reveals the evidence of an accidental failure in waste storage facilities occurred in 1960, which released substantial volumes of mine tailings into the basin, including the estuary. These events, further comprising the reliability of sediment dating methods based on 210Pb, reinforce the importance of a multidisciplinary approach in studying historically contaminated estuaries.
How to cite: Gardoki, J., Irabien, M. J., Cearreta, A., Gómez-Arozamena, J., García-Artola, A., and Serrano-García, H.: Legacy pollution from historical mining in the Suances Estuary (N Spain): Challenges for ecological recovery, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1595, https://doi.org/10.5194/egusphere-egu26-1595, 2026.
Coastal zones are dynamic interfaces where land, ocean, and atmosphere interact across multiple spatial and temporal scales. These environments are increasingly exposed to climate-driven extremes that can disrupt physical processes and threaten ecosystem functioning and human activities. Among these extremes, marine heatwaves have emerged as a major stressor in coastal areas. Currently, their manifestation and drivers within estuarine systems, particularly those influenced by coastal upwelling, remain poorly understood. This study investigates the occurrence, characteristics, and drivers of estuarine marine heatwaves (EMHWs) in the Ría de Arousa (NW Iberian Peninsula), a highly productive estuary within the North Atlantic upwelling system and supporting intensive aquaculture and fisheries activities.
The analysis performed is based on high-frequency in situ water temperature observations within the estuary, combined with satellite-derived sea surface temperature, atmospheric reanalysis products, wind-based upwelling indicators spanning multiple years, and numerical modelling. EMHWs are identified using a percentile-based threshold methodology that accounts for strong seasonal variability, allowing a consistent comparison between thermal extremes within the estuary, the adjacent continental shelf, and the open ocean.
A total of 38 EMHW events are detected during the study period, exhibiting marked interannual and seasonal variability in frequency, duration, and intensity. EMHWs occur throughout the year but exhibit a marked seasonal signal, with the highest cumulative intensities recorded in autumn. October emerges as the month with the most intense events, coinciding with reduced upwelling activity, highlighting the role of coastal hydrodynamics in modulating estuarine thermal extremes. Elevated frequencies are also observed in December and February. The preferential occurrence of intense EMHWs during late autumn and winter has important ecological implications, as these periods coincide with key stages of the reproductive cycles of many species of ecological and commercial interest. Prolonged exposure to anomalously high temperatures during these sensitive phases may compromise reproductive success, population resilience, and the ecosystem services provided by estuarine systems.
Statistical analyses show that EMHW variability is primarily driven by sea surface temperature anomalies on the continental shelf and in the adjacent open ocean, explaining up to ~20 % of the observed variance. The influence of coastal upwelling on EMHW development is found to be weak. While upwelling-favourable winds can locally reduce thermal extremes, their buffering capacity appears limited under sustained oceanic warming.
In a context of climate change and given the socio-economic importance of shellfisheries in the region, numerical modelling is required to assess the future evolution and impacts of thermal extremes in estuarine systems. Downscaled regional climate projections under SSP2-4.5 and SSP5-8.5 scenarios project a substantial increase in the frequency and intensity of extreme thermal events and associated bottom water temperature anomalies. Thermal exposure analyses suggest species-specific vulnerability within the shellfishery sector, with Venerupis corrugata and Cerastoderma edule likely to experience critical thermal stress.
The results highlight growing climate risks for biodiversity, aquaculture, and fisheries, and emphasize the need to account for cross-scale coastal interactions when developing adaptation and management strategies in productive coastal zones.
How to cite: Des, M., Castro-Olivares, A., deCastro, M., and Gómez-Gesteira, M.: Estuarine marine heatwaves in an upwelling system: coastal drivers, seasonal dynamics, and implications for ecosystem services, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19678, https://doi.org/10.5194/egusphere-egu26-19678, 2026.
Saltmarshes and seagrass meadows are highly productive coastal ecosystems that provide essential ecosystem services, such as carbon cycle regulation, sediment stabilization, and protection against extreme events. Unfortunately, these valuable systems are increasingly threatened by the effects of climate change, particularly due to the accelerating rise in sea level. Their resilience largely depends on their capacity to sustain positive substrate accretion through particulate matter retention and biomass production, especially within belowground compartments, thereby enabling compensation for sea-level rise. However, plant production remains poorly constrained, due to methodological challenges associated with its quantification and the heterogeneous environmental conditions that characterize them.
To help bridge this knowledge gap, this study estimated annual above- and belowground biomass production in two intertidal saltmarsh areas representative of Cadiz bay (Spain): Puerto Real (PT) and Santibañez (ST). Sampling locations were selected in homogeneous vegetation patches, with 14 sites established in PT and 11 in ST to encompass existing spatial variability. Aboveground production was assessed using circular exclusion structures of 25 cm in diameter, from which the initial aboveground vegetation was removed and biomass regrowth was quantified after 12 months. Belowground production was quantified using a modified ingrowth core method, which involved inserting partially open, mesh-wrapped cylinders, filled with root-free sediment. The cores were retrieved after 12 months under natural conditions to quantify root colonization. In the case of seagrass meadows, above- and belowground production was estimated exclusively from plant crowns, considered as the functional structural unit.
Results revealed clear differences between the studied vegetation types. In seagrass meadows, annual production averaged approximately 25 gPS·m⁻²·yr⁻¹ for aboveground biomass and 42 gPS·m⁻²·yr⁻¹ for belowground biomass. In contrast, saltmarsh communities showed markedly higher values, reaching 310 gDW·m⁻²·yr⁻¹ and 475 gDW·m⁻²·yr⁻¹, respectively. These findings highlight the predominant role of belowground compartments in the production balance of both ecosystems, where roots and rhizomes directly contribute to sediment stabilization. The spatial variability observed among sampling points suggests the influence of environmental and biological factors, such as dominant species or relative elevation, whose assessment will allow for a better understanding of the mechanisms driving resilience to sea-level rise.
Overall, the combined methodological approach provides a robust and transferable framework for quantifying productivity in intertidal ecosystems and constitutes a solid basis for upscaling biomass production from local measurements to larger spatial scales. By integrating field-derived production rates with spatial information on vegetation distribution, this approach enables ecosystem-scale assessments of productivity, carbon accumulation and sediment dynamics. The dominance of belowground production underscores its fundamental role in maintaining surface elevation and enhancing resilience to sea-level rise, offering key insights to support conservation and management strategies under climate change.
How to cite: Rodríguez-Rojo, C. N., Peralta, G., Zarandona, P., and Curcio, A. C.: Above- and belowground biomass production in intertidal vegetated ecosystems of Cadiz Bay (Spain): implications for resilience to sea-level rise, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4969, https://doi.org/10.5194/egusphere-egu26-4969, 2026.
Microphytobenthos (MPB) are microalgae that form biofilms on sediment surfaces and play a key role in coastal ecosystems by supporting food webs, regulating carbon (CO2) fluxes, and stabilizing mudflats.
Some species are known to migrate vertically within the sediment as a protective strategy. During daytime low tides, MPB migrates to the surface to perform photosynthesis (S), whereas during other periods, MPB moves deeper (“buried” state, B) for nutrients and protection from grazers. The transitional state of the biofilm between B and S depends on the migration speed, which is estimated to range between 0.11 and 0.45 µm.s-1 [1]. When in B, the biofilm cannot be detected through optical remote sensing methods, and has a reduced photosynthetic rate.
It is known that extreme air temperature events will become more frequent in the coming years due to climate change. The aim of this study is to demonstrate, under controlled conditions, that an extreme air temperature event affects the up and down migration of the biofilm, and therefore the services it provides and its detectability.
Sediment containing biofilm was collected from the Loire estuary in France during two different seasons (in fall and spring), homogenized, and placed in two experimental intertidal chambers for one week, with tide, light, and temperature controlled. A one-day acclimation period simulating field conditions was applied in both chambers, after which two scenarios were implemented. One chamber served as a control, with air temperature following a sinusoidal pattern between the mean daily minimum and mean daily maximum temperatures for the 2000–2024 period, whereas a sudden extreme air temperature event was applied in the other chamber. The experiment was repeated three times for each season, using extreme air temperature events corresponding to (1) the maximum air temperature observed from hourly data, at the site, for the season, for the 2000–2024 period (29.2°C for October and 37.5°C for June), (2) the maximum observed air temperature plus a delta corresponding to an RCP4.5 scenario at long-term horizon (29.2+2.25°C for October and 37.5+1.96°C for June), and (3) the maximum observed air temperature plus a delta corresponding to an RCP8.5 scenario at long-term horizon (29.2+3.82°C for October and 37.5+3.46°C for June). Biofilm concentration in state S was measured every 30 seconds, using a non-destructive hyperspectral reflectance method. The normalized difference vegetation index (NDVI) was used as a proxy for biomass.
An increase in NDVI was assumed to indicate upward migration, while a decrease in NDVI indicated downward migration. The data were interpolated allowing comparison between the control and the treatment. For each day, the mean signed difference (MSD) between control and treatment was calculated. A positive MSD indicated stimulation of the biofilm by the treatment, while a negative MSD indicated inhibition. The initial hypothesis was that the treatment would stimulate the biofilm at the beginning of the event, followed by a progressive inhibition over the week. Results are discussed to confirm, or not, the hypothesis.
[1] Serôdio et al. (2023). Light niche construction: Motility of sediment-inhabiting diatoms determines the experienced light environment.
How to cite: Debly, A., Mecca, M., Oiry, S., Deloffre, J., Papaspyrou, S., Garcia-Robledo, E., Barillé, L., and Méléder, V.: Experimental evidence of how extreme air temperatures influence microphytobenthos up and down migration, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17412, https://doi.org/10.5194/egusphere-egu26-17412, 2026.
Tidal basins such as the Wadden Sea exhibit perpetual sediment dynamics and morphodynamics at scales ranging between that of bedforms and creeks to channels and tidal flats, to that of the entire basin and its transitions to neighbouring basins and the embankment on land. The Wadden Sea is the largest tidal wetland on the planet with globally important ecosystems. Tidal flats and salt marshes increase coastal flood safety by storm wave damping. The combination of accelerating sea-level rise, historic land loss and reclamation with ongoing economic activities, including mining, dredging and other disturbances, puts future ecosystem integrity and coastal flood defence at risk. The ability to adjust management in order to adapt to changes depends on scientific and societal understanding the dynamics of sediment (sand and mud) on a timescale of years to centuries. As such, a qualitative, comprehensive description is urgently needed of sediment dynamics and morphodynamics, around which all the needs and issues revolve and that experts/scientists in governmental institutions and consulting can use to inform policymakers and area managers.
Here we synthesize the available knowledge of patterns, dynamics and interactions between various forms on the basis of bathymetric data, aerial photography, background data and literature. This holistic systems synthesis is a co-creation with societal partners in the Netherlands, who also co-designed the project (https://wadsed.nl/) by specifying their knowledge questions, perspectives on long-term development and on governance of this system. As such, their intimate knowledge of the Dutch Wadden Sea is incorporated and seeming conflicts of perceived trends (drowning vs. infilling) were reframed as research questions by the academic scientists. We will present our new insights in sediment dynamics and morphodynamics, specifically focussing on sediment dynamics during storms, channel-bar interactions and tidal ‘divides’ which are conceptually bounding the individual tidal basins but turn out to be quite open for water and mud exchange. This culminates into a description of tidal basins as multi-scale complex open systems diagrams, with explicit recognition of what processes and boundary conditions are affected, and potentially manageable, by human interference.
How to cite: Kleinhans, M., Cleveringa, J., and van der Spek, A.: Shallow tidal system morphodynamics: a synthesis of forms and behaviours in the Wadden Sea for long-term management with understanding, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3104, https://doi.org/10.5194/egusphere-egu26-3104, 2026.
Coastal water bodies—lagoons, estuaries, and associated wetlands are dependent on and thus vulnerable to changes in both ocean and watershed dynamics. In semi-arid and Mediterranean climates, estuaries and coastal lagoons persist despite ephemeral riverine discharge (on seasonal or interannual timescales) and intermittent connection via tidal inlets to the ocean. The persistence of coastal surface water bodies in the absence of riverine or tidal inflow suggests subsurface flow as the main driver of coastal hydrology in these systems.
This work explores the coastal water bodies of three watersheds in Central Chile. The Huaquén watershed is a 151 km² coastal basin with an ephemeral river but perennial coastal wetland and lagoon. Except for immediately after large storms, the lagoon does not have a tidal connection to the ocean. The much larger Petorca (1989 km²) and La Ligua (1979 km²) watersheds drain into the Pacific Ocean through a shared estuary. The confluence of the two rivers is located 1 km upstream from the intermittently open inlet. These watersheds with origin in the Andean foothills, despite their large size, have very low riverine discharge due to climate, drought, and water-intensive agricultural development.
Here we present results spanning two years of in-situ measurements of water level in the Pichicuy lagoon at the outlet of the Huaquén watershed, and the Ligua–Petorca estuary and nearby groundwater wells, combined with satellite remote sensing of surface water bodies using 10m resolution Sentinel-2 data and longer-term monitoring of groundwater and surface water by the Chilean water agency.
Results highlight the dominance of groundwater exchange in the dynamics of coastal lagoons without an open tidal inlet. Measurements in the small Pichicuy lagoon show hydrology dominated by ocean-driven exchange via flow through the sandbar. This flow depends on the hydraulic gradient driven by wave setup and modulated by the tide, which is attenuated through the sandbar. In the much larger Ligua-Petorca watershed, little ocean influence is observed within the closed lagoon, but the surface area and water levels are shown to vary seasonally with watershed groundwater level fluctuations and on longer timescales with groundwater depletion by drought and water over-exploitation. This work highlights the importance in considering subsurface exchange flows between the ocean, coastal estuaries and lagoons, and the watershed, especially as climate change alters conditions in both the coastal ocean and in semi-arid and Mediterranean watersheds worldwide.
How to cite: Williams, M., Yovan, L., Gómez, R., Leray, S., and Vicuña, S.: Subsurface flow-driven hydrology of semi-arid coastal lagoons, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15212, https://doi.org/10.5194/egusphere-egu26-15212, 2026.
Coastal lagoons are highly dynamic transitional systems whose hydrographic properties are strongly modulated by atmospheric forcing, freshwater inputs, and exchanges with the open sea, reflecting coupled land–sea–atmosphere processes across coastal interfaces. Accurately simulating their temperature and salinity variability remains challenging, particularly under climate change scenarios, due to the high computational cost of process-based hydrodynamic models and the limited availability of long observational time series. Here, we present a data-driven modelling framework to reproduce and project monthly surface water temperature and salinity in the Venice Lagoon, one of the most complex and vulnerable coastal systems in the Mediterranean region, using a Convolutional Neural Network (CNN). The model is trained using irregular monthly observations collected between 2001 and 2004 at three representative stations (marine, intermediate, and riverine), combined with a minimal set of physically interpretable atmospheric and oceanographic predictors, including 2 m air temperature, precipitation, mean sea level, and offshore sea surface salinity. Despite the short training period, the CNN accurately reproduces the observed seasonal and interannual variability, achieving high skill scores (R² > 0.96 for temperature and R² > 0.85 for salinity at most stations). A sensitivity analysis reveals distinct dominant drivers across the lagoon, with oceanic forcing prevailing near the inlets and atmospheric–terrestrial controls becoming increasingly important in river-influenced areas. The validated model is subsequently employed to explore synthetic climate change scenarios corresponding to 1.5, 2, and 3 °C global warming levels relative to pre-industrial conditions. Results indicate a pronounced amplification of the seasonal cycle, with summer surface water temperature increases exceeding 6 °C and salinity increases above 4 PSU at the riverine station under the 3 °C scenario. These changes suggest substantial future alterations of lagoon hydrography, with potential implications for ecosystem functioning and resilience. Overall, this study demonstrates the potential of CNN-based approaches as computationally efficient tools for climate impact assessment in complex coastal environments, complementing traditional hydrodynamic models and enabling rapid scenario exploration.
How to cite: Bozzeda, F., Sigovini, M., and Lionello, P.: Climate-driven changes in Venice Lagoon hydrography under global warming scenarios, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19480, https://doi.org/10.5194/egusphere-egu26-19480, 2026.
Coastal wetland ecosystems (CWEs), including mangroves, saltmarshes, and seagrasses, deliver vital ecosystem services at the land-ocean interface, where microbial communities act as key agents of biogeochemical cycles by mediating energy flow and material transformation. Yet, a comprehensive understanding of their global-scale diversity, distribution, and functional attributes remains elusive. To elucidate these aspects, we analyzed 1,384 high-throughput sequencing samples to examine microbial diversity and assembly processes across these global habitats. Our results revealed significant differences in microbial diversity and function among these ecosystems (p < 0.001), with mangroves exhibiting the highest richness and diversity. The habitat-specific keystone taxa were Rhodothermia, Anaerolineaceae, and SBR1031 in mangroves, Flavobacteriaceae, Burkholderiales, and Woeseiaceae in saltmarshes, and Desulfosarcinaceae, Pseudomonadaceae, Firmicutes, and Bacillales in seagrasses through LEfSe and Random Forest model analysis. Co-occurrence network analysis revealed a robust structure comprising 1521 nodes and 64,463 edges, dominated by Gammaproteobacteria, Desulfobacteria, Bacteroidia, and Desulfobulbia. KEGG-based functional profiling showed that mangroves were distinguished by a high abundance of microbial functions related to nitrogen cycling and sulfate metabolism. Seagrasses showed a higher abundance of taxa involved in the methane metabolism and saltmarsh communities were dominated by functions related to aromatic hydrocarbon metabolism. Using iCAMP, we found that deterministic selection governed community assembly in saltmarshes (44.42%), whereas ecological drift was the major contributor in seagrass (63.1%) and mangrove (43.17%) ecosystems. This underscores the dependence of dominant assembly processes on local environmental contexts. Our findings establish a basis for elucidating the structure and function of microbial communities in CWEs, offering insights for future hypothesis-driven research and enhancing predictive capacity amid growing anthropogenic and climatic pressures.
How to cite: Wang, L. and Engel, A.: Comparative Analysis Unveils Distinct Functional Profiles and Assembly Mechanisms of Microbiomes in Global Coastal Wetland Ecosystems, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2542, https://doi.org/10.5194/egusphere-egu26-2542, 2026.
Recent studies indicate that typhoons can trigger intense organic matter degradation in coastal areas. Nevertheless, as coastal currents enhance primary production, the balance between organic matter addition and degradation remains unclear, which restricts a comprehensive understanding of the carbon cycle. This study investigated the biogeochemical processes of dissolved organic matter (DOM) in the northwestern South China Sea, which is affected by the coastal current along the western Guangdong coast, before and after the passage of Typhoon Wipha (2019), through measuring DOM-related parameters and applying the three-end-member mixing model. The results demonstrated that in the nearshore, DOM exhibited a significant net addition before the typhoon. This was mainly due to the strong coastal current that facilitated the primary productivity. After the typhoon, DOM levels in coastal waters increased significantly due to greater land-based input, stronger vertical mixing, and higher primary production. However, the net addition of DOM was lower than pre-typhoon, primarily because of enhanced DOM degradation. In the offshore area, the biological activities stimulated by the strong coastal current remained the primary cause of most DOM additions before the typhoon. Nevertheless, after the typhoon, DOM showed net removal, as degradation exceeded production supported by the coastal current, with removal rates of 7% to 17%. This indicates that typhoons accelerate the degradation of DOM in coastal regions, potentially reducing marine carbon storage enhanced by coastal currents, offering insights into how the coastal carbon cycle responds to environmental changes.
How to cite: Lu, X.: Biogeochemistry of Dissolved Organic Matter in the Northwestern South China Sea under the Combined Influence of Coastal Currents and Typhoon Wipha, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3989, https://doi.org/10.5194/egusphere-egu26-3989, 2026.
The Eastern Boundary Upwelling Systems (EBUS) in the subtropical Atlantic and Pacific Oceans are regions where wind-induced coastal upwelling results in cold, nutrient-rich surface waters, leading to high productivity. Changes in these regions are of significant interest due to their importance to fisheries, economies, biological productivity, diversity, and the CO2 cycle. Here, we examine future trends in upwelling and surface CO2 fluxes across the four EBUS, simulated with different versions of the Earth System model MPI-ESM driven by different carbon emissions scenarios. Our objectives are to test the hypothesis of a more substantial intensification of upwelling in the EBUS regions located polewards and to investigate the impact of upwelling changes on CO2 surface fluxes.
Using several realisations and high and low-resolution simulations enables us to analyse the internal climate variability and the effect of horizontal resolution on upwelling trends. Our study shows that upwelling does not intensify in the poleward subregions of all four EBUS but instead decreases in all the equatorward subregions. In these simulations, upwelling intensifies in the poleward subregions of the Humboldt and Canary upwelling systems, whereas it decreases in all subregions of the Benguela and California upwelling systems. The model resolution is not relevant for the directions of simulated change in upwelling. The poleward expansion of the Hadley Cell and, thus, the poleward displacement of the subtropical highs drive the change. This high-pressure cell moves offshore in the South Atlantic, which might lead to the negative trends in South Benguela. However, the realism of this westward shift might be questionable, as Earth System models struggle to simulate the South Atlantic high at its observed position. The decrease‚ in California upwelling may be due to the offshore shift of the subtropical high over the North Pacific or the summertime contraction of the Hadley Cell over the North Pacific.
The CO2 flux from the atmosphere into the ocean shows a general increase in the oceanic CO2 sink under the high-emission scenario, but a decrease under the low-emission scenario. These changes are not consistent with trends in upwelling but rather with atmospheric CO2 concentrations. An exception is the North Canary subregion, which remains a CO2 source in all scenarios, even though upwelling intensifies there.
How to cite: Tim, N., Zorita, E., Hünicke, B., and Mathis, M.: 21st Century Upwelling and Air-Sea CO2 Flux Trends in the EBUS in CMIP6 MPI-ESM Realisations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17642, https://doi.org/10.5194/egusphere-egu26-17642, 2026.
The impacts of tidal energy development on the environment, ranging from species to habitats to oceanographic systems, remain uncertain, and gaps persist in current research. Most studies to date have focused on the impacts relating to collision, noise, displacement, and localised hydrodynamic changes that affect sedimentation transport and benthic species composition. There have been limited studies on the impacts of tidal energy on habitats, species distributions (especially mobile, pelagic species), and the wider ecosystem. There has also been no consideration of cumulative environmental impacts of energy extraction at multiple sites, and few studies have considered the comparative impacts of climate change.
Here, we simulate the tides in the Celtic Sea using the multi-scale unstructured mesh numerical model, Thetis. Spatially varying sea-level rise is applied to these models for the first time, using data from the AR6 IPCC assessment, to examine the impact of sea-level rise on tidal dynamics. Shared Socioeconomic Pathways (SSPs) 1.19 through to 5.85 at the 50% confidence interval for years 2050, 2100, and 2150 are used to predict sea-level rise under different scenarios.
Results show that tidal range (m) and maximum velocity (m/s) are likely to generally increase over time and with SSP scenario. Tidal range increases are particularly high in the Severn Estuary (up to 0.5 m increase) and, to a lesser extent, in the wider Celtic Sea (up to 0.1 m). Sea level-rise is expected to add between 0.28 and 2.01% to the maximum tidal range within the Celtic Sea. This is in addition to predicted sea-level rise. Conversely, when adding tidal energy arrays into current tidal model conditions, tidal range tends to decrease across the south of the domain area, with a small increase in tidal range between Northern Ireland and North-west Scotland, followed by a mix of small increases and decreases off the Scottish coast. Overall, the installation of tidal arrays is expected to decrease the maximum tidal range by 10%. This keeps pace with increasing relative sea-level rise, demonstrating that possible sea-level rise and tidal array installation may complement each other to offset predicted changes to tidal dynamics.
Under SSP scenarios, maximum velocity is predicted to increase between some islands off the coast of North-west Scotland, and between Morecambe Bay and the River Dee. These predicted changes may affect the efficiency of tidal energy development over time, as well as affect species distributions in localised environments where high levels of change are predicted.
Unsurprisingly, with the presence of tidal arrays, maximum speed is predicted to generally decrease across the Celtic Sea, with some small increases expected between islands off the North-west Scottish coast. When incorporating predicted sea-level rise, the level change is minimal, demonstrating that tidal arrays are more likely to have an impact on tidal velocity and that sea-level changes are unlikely to affect velocities enough to significantly reduce tidal energy efficiency. Further work is being considered on optimising tidal array installations to suitably offset predicted relative sea-level rise and maintain energy production levels.
How to cite: Mackay, Z., Hill, J., Angeloudis, A., and Stewart, B.: Can tidal energy extraction counteract sea-level rise impacts?, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11464, https://doi.org/10.5194/egusphere-egu26-11464, 2026.
Sustainable multi-use offshore infrastructure has been installed in the North Sea and Baltic Sea coastal regions as part of the OLAMUR initiative. Large offshore wind farm aggregations are being combined with low-trophic aquaculture to enhance fish and shellfish production. A key requirement of this initiative is to assess the impact of these wind farms on local wind and waves, ocean currents and turbulence, and the variability of nutrient and carbon uptake. In this work, we use a hydrostatic HIROMB-BOOS Model (HBM) setup to investigate the short-term (20 days) impact of Danish and North Sea wind farms on the regional ocean turbulence and stratification. While previous modeling studies have used unstructured grids to resolve monopile geometry, our approach employs a structured, submesoscale-resolving grid, and the turbine impact is being represented through a subgrid frictional drag increment to the prognostic equations of the k-omega turbulence closure model used in the HBM. We conduct short-duration simulations, both with and without wind farm forcing, for the summer and winter seasons. This enables an assessment of seasonality and the spatial reach of wind-farm-induced anomalies over a 20-day window. Our analysis focuses on four regions: Helgoland, the Southern North Sea, Kriegers Flak, and Anholt. We examine changes in the vertical structure using potential energy anomaly (PEA) and compare them with kinetic energy differences in both resolved and subgrid space. The tidally active Southern North Sea exhibits a strong increase in stratification during summer, with PEA anomalies ranging between 4% and 6% over multi-day periods, whereas Helgoland shows a smaller response (on the order of 1%). In contrast, the Danish coastal regions (Kriegers Flak and Anholt) display PEA values one to two orders of magnitude smaller (0.2 %) and more intermittent behavior, consistent with weaker tidal signals and stronger eddy-induced turbulence. We interpret the North Sea response as wind farm drag extracting energy from a tidally dominant regime, thereby reducing shear-driven flow and allowing stratification to persist. Far-field regions in the Skagerrak and Kattegat channels show strong anomalies at later stages in the simulation, which is attributed primarily to the background submesoscale turbulence caused by cross-flow exchange between North Sea and Baltic Sea waters.
How to cite: Mukherjee, S., Murawski, J., She, J., and Frisfelds, V.: Short-term impact of offshore wind farms on the regional ocean turbulence and stratification in the North Sea and Danish coastal waters, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12582, https://doi.org/10.5194/egusphere-egu26-12582, 2026.
With the ongoing energy transition towards renewable energy and away from nuclear power, offshore wind energy has become increasingly important and now represents a central pillar of German energy policy. Consequently, a growing number of offshore wind farms are being constructed in the North Sea. This development renders large marine areas unavailable for traditional activities such as fisheries and other former economic uses, while the water column in the immediate vicinity of the monopile foundations remains largely unused by other sectors. Monopiles interact with the local hydrodynamic environment by modifying wave propagation and attenuating wave energy, yet they do not adversely affect water quality, making these areas potentially suitable for co-use applications, such as offshore aquaculture. For lower-trophic aquaculture, essential nutrients are naturally supplied by the marine environment, and the demand for mussels and macroalgae as food resources is steadily increasing. However, aquaculture production in Germany has so far been dominated by onshore and near-coastal facilities, with offshore cultivation still being limited.
In this study, the socio-economic system (SES) formed by the co-location of an offshore wind farm and aquaculture is analysed using the Ostrom–McGinnis framework. The analysis focuses on the existing offshore wind farm Meerwind, located northeast of Helgoland, which enables the assessment of OWF impacts on the SES based on historical and observational data. This framework allows for the systematic evaluation of how public benefits can be optimised, in particular by enhancing the ecosystem services and socio-economic value generated by offshore aquaculture. By varying and analysing key conditions, such as the precise spatial placement of aquaculture installations, optimal configurations of the SES can be identified. The drivers and feedbacks influencing the SES are quantified using numerical simulations. For this purpose, the hydrodynamic model SCHISM is coupled with the biogeochemical model ECOSMO to simulate environmental conditions relevant for aquaculture growth and to explicitly model mussel production. This integrated modelling approach enables the estimation of public benefits under different SES configurations, thereby providing a quantitative basis for advising industry and policymakers on sustainable co-use strategies within offshore wind farms.
How to cite: Berg, M. D., Pein, J., Staneva, J., and Arnason, R.: Socio-Economic Assessment of Co-Located Offshore Wind and Aquaculture Systems, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20697, https://doi.org/10.5194/egusphere-egu26-20697, 2026.
Among various human activities in densely populated coastal areas, intense ferry traffic plays an essential role in coastal processes. Several studies of fast ferry traffic have shown that wake-induced mechanical sediment disturbance harms coastal environments in several ways. These include suppression of coastal vegetation, promotion of eutrophication through nutrient resuspension, sediment erosion, and enhanced coastal methane emissions. According to a recently published review on marine biodiversity loss, physical disturbance of the seabed is among the most common causes of biodiversity loss in Finnish coastal waters.
In our research, we aim to assess the rate of physical sediment disturbance caused by frequent ferry traffic near the Turku–Stockholm ferry lane in the Archipelago Sea, Finland. To capture evidence of nearshore disturbance, we use a prototype of an innovative online sediment trap. The online sediment trap is a prominent Finnish invention equipped with a computed tomography function. It performs tomographic scans of the trap tube interior, producing volumetric images of structures within it. This feature enables direct quantification of sediment flux induced by a single ferry passage, with measurements performed at an hourly timescale. These high-resolution monitoring data, combined with ferry passage data from the marine Automatic Identification System (AIS) and meteorological data, are analysed using statistical methods to uncover hidden patterns and drivers. The insights from our research are then interpreted in the context of sedimentological processes in the coastal environment to support sustainable maritime management and the protection of the fragile shallow and coastal environments of the Archipelago Sea.
How to cite: Pastukhova, V., Johansson, M., Gonzales Inca, C., Hietaharju, E., and Saarni, S.: High-frequency monitoring of ferry-induced sediment resuspension in coastal zones, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14010, https://doi.org/10.5194/egusphere-egu26-14010, 2026.
Coastal erosion along the southern Baltic Sea was analysed using airborne LiDAR surveys from 2011, 2012 and 2022 combined with a 12-year wave hindcast based on SWAN/ECMWF reanalysis and data provided by the Finnish Meteorological Institute (FMI). A coastal strip approximately 200 km wide, including cliffs or dunes, beaches and the shallow nearshore zone, was investigated to quantify volumetric changes and their relationship to storm-wave conditions.
Storm events were identified using two thresholds: significant wave height Hs ≥ 2 m and Hs ≥ 4 m with a minimum duration of 12 hours. Three offshore points located along the Polish coast were analysed to assess spatial variability in storm frequency, wave height and wave direction. The results indicate strong contrasts in storm exposure, with the central–eastern sector being the most affected and the western sector strongly sheltered.
LiDAR-based differencing revealed a pronounced west–east erosion gradient. Cliffed sectors exhibit deep but spatially limited erosion (class 1, >10 m A.S.L.), whereas low-lying barrier and deltaic coasts are dominated by widespread abrasion in the 1-5 m A.S.L. The total abrasion volume between 2011 and 2022 reached - 16.6 million m³.
To capture spatial variability, shoreline change rates were computed on a regular 1-km grid along the entire coastline, revealing alternating erosion and accumulation cells strongly controlled by coastal morphology and storm-wave exposure. In addition, erosion volumes were aggregated at the municipal level to estimate potential economic impacts related to the loss of land, tourist infrastructure, coastal protection assets and ecosystem services. The highest potential economic losses were identified in municipalities with cliffed coasts and densely developed tourist zones, whereas lower impacts characterize sparsely developed, low-lying barrier coasts.
The results demonstrate that storm-wave climate, coastal morphology and local socio-economic conditions jointly control the magnitude and spatial distribution of coastal erosion risk along the southern Baltic Sea.
How to cite: Terefenko, P., Giza, A., Śledziowski, J., Tanwari, K., Bugajny, N., Sicińska, A., and Wróblewski, K.: Storm-Driven Coastal Erosion and Shoreline Dynamics along the Southern Baltic Sea Coast: A LiDAR and Wave Hindcast Study, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13439, https://doi.org/10.5194/egusphere-egu26-13439, 2026.
During the early Holocene, rapid sea level rise led to the inundation of worldwide coastal areas, with the surrounding shallow landscapes being the most affected. The Carmel coast, located in the East Mediterranean, preserves a rich record of such a submerged landscape dotted by many archaeological sites, including the well-preserved Atlit-Yam village (Neolithic), which is currently buried and submerged at 8-11 m water depth. In order to reconstruct the geomorphological evolution of the submerged landscape, 23 sediment cores of variable length (ranging 60-240 cm) were drilled both inside and outside the known extent of the Atlit-Yam village. A detailed stratigraphy of the submerged landscape was generated based on the analysis of 18 out of 23 cores, framed by robust radiocarbon ages. The sedimentary sequences identified in the analyzed cores were defined by respective facies associations, and combined with physical (grain size, magnetic susceptibility), chemical (elemental geochemistry), and organic (total organic content) properties of the sediments. Our analysis reveals a non-uniform evolution of submerged coastal sediments, influenced by sediment supply, regional geomorphology, and human activity. Within a spatial stratigraphy, we found distinct anthropogenic units that underlines the intricate balance between humans and the Early Holocene changing environment (including sea level rise, depositional processes, and sediment dynamics). This study holds implications for future research in identifying and preserving potential archeological sites elsewhere and helps to shed light on the impact of climate change, sea level, and surface processes on coastal communities.
How to cite: Kataria, V., Waldmann, N., Ogloblin Ramirez, I., Shtienberg, G., Zukerman-Cooper, R., Taha, N., Grono, E., Runjajić, M., Galili, E., and Friesem, D. E.: Geomorphological dynamics at the coast: A sedimentary stratigraphy for Atlit-Yam, the earliest coastal village at the Eastern Mediterranean and its submerged landscape , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2269, https://doi.org/10.5194/egusphere-egu26-2269, 2026.
Coastal landforms are continuously reshaped by natural forcings such as typhoons, waves, tides, and sea-level rise, as well as by human interventions including coastal protection structures. Rapid morphological changes can lead to shoreline erosion, retreat, and infrastructure damage, highlighting the need to quantitatively assess both the effectiveness and unintended consequences of submerged breakwaters.
This study investigates short- and long-term morphological responses at Songdo Beach (Busan, South Korea), where a semi-enclosed nearshore zone has been formed by an east–west oriented submerged breakwater system. We integrated Real Time Kinematic (RTK) drone-based surveys with in situ hydrodynamic observations. High-resolution aerial surveys were conducted on six occasions, before and after the landfall of Typhoon Khanun (7 and 10–12 August 2023) and approximately two years later (20 August and 29 September 2025), enabling assessment of event-scale changes and subsequent recovery. In addition, an Acoustic Wave and Current Profiler (AWAC) was deployed inside the breakwater system from November 2023 to August 2024 (~10 months) to continuously measure wave height, wave period, current velocity, and current direction.
The observations indicate that mean current velocities inside the breakwater system were higher than those offshore, likely due to flow acceleration through breakwater gaps and around breakwater heads. After the typhoon, sediment loss was pronounced near the lateral beach sections close to the breakwater ends, whereas the central section in the lee of the breakwater showed net deposition. This spatial heterogeneity suggests that, while the submerged breakwater attenuates wave energy, it also redistributes nearshore currents, enhancing localized erosion–deposition patterns.
By integrating hydrodynamic measurements with high-resolution remote sensing, this study provides a quantitative assessment of how submerged breakwaters influence coastal dynamics and morphological evolution. The results emphasize that coastal protection design should consider not only erosion mitigation but also the risk of secondary erosion and long-term instability. Under increasing extreme wave events and expanding coastal development, these findings support more sustainable and adaptive coastal management strategies.
How to cite: Jeon, G.-S., Ju, H. H., and Lim, H. S.: Assessing the impacts of submerged breakwaters on coastal erosion at Songdo Beach, South Korea, using hydrodynamic observations and remote sensing, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22586, https://doi.org/10.5194/egusphere-egu26-22586, 2026.
There are >1,200 historic coastal landfill sites at risk from flooding or erosion in England. Many of these sites were created before detailed waste material logs were kept and prior to the introduction of impermeable liners, that prevent leachate and toxic gas release. Hydrological and hydrodynamic processes form critical pathways through which soluble and sediment-associated contaminants are released and dispersed in the environment, enhancing the risk they pose by increasing their distribution and biological uptake. Climate change will increase contaminant mobility and exposure as the frequency and magnitude of hydrological processes accelerates rates of host material erosion and mobility. This work contrasts contemporary contaminant profiles from three legacy coastal landfill sites in the UK and forecasts how these profiles might change under a range of future climate and intervention scenarios. The results will help decision-makers prioritise sites for protection, which is necessary given the estimated cost to defend or remove legacy landfills is projected to cost hundreds of millions to billions of euros.
How to cite: Ahmed, J., Wang, H., Eldridge, L. O. V., Newman, B. A., Spencer, K. L., Grieve, S. W. D., and MacDonald, J. M.: Forecasting pollutant mobility associated with coastal landfill sites under future climate change scenarios, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20030, https://doi.org/10.5194/egusphere-egu26-20030, 2026.
The ocean plays an important role in regulating CO2 in the earth system by buffering it as bicarbonate. However, this mechanism is unable to keep up with the rapid increase in atmospheric CO2 concentrations. One proposed approach to mitigating this issue is to enhance the ocean’s alkalinity. This is induced by enhanced weathering of alkaline rock feedstock. Many strategies of atmospheric CO2 removal are now being researched. However, the role of enhanced weathering in the beach-ocean interface has received comparably little attention. Our focus on coastal processes is based on their greater potential feasibility and the interaction between weathered rock, seawater, and the atmosphere. This study aims to simulate ocean alkalinity enhancement in a beach setting on a laboratory scale. This will be achieved using a custom-built overhead shaker to induce constant motion in a mixture of seawater and rock material. Via frequent monitoring and measurement of key components, such as ionic composition, the effect of rock weathering on sea water alkalinity is assessed. If expectations are met, mineralogical composition as well as grain size will influence the alkalinity enhancement potential. To quantify this, samples of basalt, andesite and glacial sediments will be compared at two grain sizes. The expectation is to see a larger alkalinity enhancement for smaller grain sizes due to larger surface area, and for basalt due to faster weathering rate. This study will evaluate the proposed option to reduce a future peak in atmospheric CO2 concentration and aims to increase the understanding of beach-ocean interfaces.
How to cite: Flinspach, G., Hierlemann, T., Leonhardt, J., Neumann, I., Quoß, S. M., Spano, L., and Suchau, C.: Simulate the Beach: The Influence of Rock Properties and Mineral Composition on Ocean Alkalinity, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13332, https://doi.org/10.5194/egusphere-egu26-13332, 2026.
Sand ripples, the smallest and most ubiquitous bedforms in coastal and seabed environments, enhance turbulence and sediment resuspension within the bottom boundary layer. Under natural wave forcing, ripples often develop three-dimensional (3D) features—such as terminations, bifurcations, and secondary crests—that reflect their complex adaptation to varying hydrodynamic conditions. To investigate the hydrodynamics over different ripple types, we conducted laboratory experiments in a U-shaped oscillatory tunnel at the Ecohydraulics and Ecomorphodynamics Laboratory, University of Illinois at Urbana-Champaign (USA). Two fixed 3D-printed ripple morphologies were studied: uniform ripples and ripples with superimposed secondary crests. Results demonstrate that the addition of secondary crests substantially modifies flow dynamics, both locally and across neighboring ripples. Compared to uniform ripples, secondary crests produce a thicker boundary layer and induce a notably higher shear velocity at the crest, indicating a greater potential for sediment transport and bedform evolution. These findings provide valuable insights into ripple morphodynamics and contribute to a better understanding of sediment processes in coastal and marine environments.
How to cite: Jin, C., Gong, Z., San Juan, J., Rafael, T., and Coco, G.: Laboratory experiments on the near-bed hydrodynamics over regular and irregular ripples., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8665, https://doi.org/10.5194/egusphere-egu26-8665, 2026.
Accurate nearshore wave measurements are essential for assessing coastal protection and the performance of nature-based solutions in vegetated environments. However, conventional approaches face major limitations in shallow and intertidal zones: wave buoys are ineffective where wave-seabed interactions dominate, while wave gauges require complex infrastructure and are vulnerable to damage. Although remote sensing techniques such as radar, cameras, and lidar have been explored, they remain costly and logistically demanding. Pressure sensors provide a robust and cost-effective alternative, but reconstructing surface wave elevation from bottom pressure measurements is challenging in shallow water due to pronounced nonlinear effects.
Linear pressure transfer methods systematically underestimate wave heights and fail to capture nonlinear extreme events, leading to errors in wave energy estimates and attenuation assessments. These limitations are particularly critical in vegetated coastal zones, where accurate wave characterization underpins evaluations of wave attenuation and coastal protection capacity.
This study implements and validates the nonlinear weakly dispersive pressure reconstruction method of Bonneton et al. (2018) for nearshore wave climate characterization. The method reconstructs surface elevation using first- and second-order time derivatives and frequency-domain filtering, providing improved performance under shallow-water conditions.
Pressure sensor arrays were deployed across seven coastal sites in Northern Ireland, spanning sheltered sea loughs to exposed embayments, with deployments capturing storm events with significant wave heights exceeding 0.5 m. Complementary wave tank experiments were conducted to validate hydrostatic, linear, and nonlinear reconstructions against wave gauge measurements over wave periods of 0.9-1.8 s and wave heights of 20-80 mm.
Results show that nonlinear reconstruction yields wave heights up to 56% higher than linear methods under energetic conditions and agrees within 8.4% of wave gauge measurements. Field observations indicate wave energy dissipation upto 18.5% across vegetated transects. The approach enables robust quantification of wave attenuation and supports the evaluation of coastal nature-based solutions across vegetated shorelines.
References
Bishop, C. T., & Donelan, M. A. (1987). Measuring waves with pressure transducers. Coastal Engineering, 11(4), 309–328.
Bonneton, P., Lannes, D., Martins, K., & Michallet, H. (2018). A nonlinear weakly dispersive method for recovering the elevation of irrotational surface waves from pressure measurements. Coastal Engineering, 138, 1–8.
How to cite: Baghanian, S., Schmitt, P., Wilson, C., and Melor, A.: Enhanced Nearshore Wave Characterization Using Nonlinear Pressure Reconstruction: Applications to Wave Attenuation in Vegetated Coastal Zones, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21554, https://doi.org/10.5194/egusphere-egu26-21554, 2026.
Coastal estuaries are hotspots of biogeochemical cycling, biodiversity, and sediment cycling, yet the drivers of carbon cycle processes remain poorly constrained. This study elucidates how hydrological connectivity influences carbon biogeochemistry in the Indian Sundarban over two monsoonal cycles spanning pre-monsoon, monsoon, and post-monsoon seasons. A spatially extensive sampling strategy compared channels connected to perennial freshwater flow with channels isolated from feeding rivers. Linear mixed-effects modelling showed dissolved organic carbon (DOC) and particulate organic carbon (POC) varied significantly with both season and connectivity. DOC peaked pre-monsoon and POC during the monsoon, with higher concentrations in connected sites. Dissolved inorganic carbon (DIC) declined during the monsoon but showed no connectivity effect. Elevated DOC relative to conservative mixing was attributed to freshwater runoff or groundwater input. Isotope data indicated POC respiration dominated during pre- and post-monsoon, while DOC flocculation-controlled monsoon POC dynamics, particularly in connected sites. Carbonate dissolution regulated pre-monsoon DIC in general, while organic matter degradation dominated in the monsoon and post-monsoon periods. CO₂ efflux, measured across all sites (1.7–297.6 mmol C m⁻² d⁻¹), was consistently a source to the atmosphere and 2–4 times higher in connected channels, with higher turbulence driving maximum fluxes in upper reaches. Our findings demonstrate that hydrological connectivity fundamentally structures estuarine carbon cycling, lowering organic carbon concentrations and enhancing CO₂ fluxes. Thus, shifts in global coastal delta sediment dynamics and subsequent riverine impacts, may significantly change global deltaic carbon cycle processes.
How to cite: Bass, A., Tang, W., Henderson, A., Panizzo, V., Fielding, J., Chanda, A., Shil, S., Ghosh, T., Slaymark, C., and Large, A.: Fluvial Connectivity Impacts Carbon Biogeochemistry in a Tropical Mangrove Delta, Sundarban, India., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2562, https://doi.org/10.5194/egusphere-egu26-2562, 2026.
The Indian Sundarban Delta (ISD), occupying the southern sector of the Ganga–Brahmaputra–Meghna (GBM) delta along India’s eastern coast, represents one of the world’s most dynamic yet environmentally fragile deltaic systems. Over the past three decades, the ISD has undergone a pronounced morphodynamic transformation driven by the interplay of reduced sediment supply, sea-level rise, and intensified coastal processes. This study investigates the long-term linkage between suspended sediment dynamics and shoreline evolution from 1990 to 2024, integrating multi-temporal satellite observations, Digital Shoreline Analysis System (DSAS)-based metrics, and satellite-derived suspended sediment concentration (SSC).
Multi-decadal Landsat imagery was used to extract shorelines under comparable tidal conditions and estimate SSC using established semi-empirical models. Shoreline change parameters, including Net Shoreline Movement (NSM) and End Point Rate (EPR), were computed at 50-m intervals along approximately 2,980 km of coast, covering eight geomorphic zones. Results reveal extensive shoreline retreat and land loss, with the highest erosion recorded along the ocean-facing margins of the Hooghly River, where EPR exceeded –60 m/yr. Areal analysis shows widespread island fragmentation and loss of tidal flats, indicating ongoing morphological degradation.
The SSC assessment indicates strong seasonal variation, characterized by higher concentrations during the wet season (May–October) and significantly reduced levels in the dry months. Spatially, SSC within the Ganges–Brahmaputra estuarine complex shows a distinct decline seaward, with the highest turbidity typically found near the river mouth or bay head, depending on discharge magnitude and monsoonal intensity. In these high-turbidity zones, concentrations often exceed 150 mg L⁻¹, reflecting the influence of strong fluvial inputs during peak discharge periods.
A marked long-term decline in SSC, particularly across the outer estuarine zones of the Hooghly and Meghna rivers, reflects significant sediment starvation since the 1990s. This decline is attributed to upstream sediment trapping, altered hydrological regimes, and enhanced marine reworking. The reduced sediment supply has intensified shoreline retreat and disrupted the sediment–morphology balance, shifting the delta towards a net erosional state.
Overall, the study underscores a strong sediment–morphodynamic coupling in the Sundarban region, where the combined effects of sediment starvation, sea-level rise, and intensified hydrodynamic forces are reshaping the deltaic landscape. These findings highlight the urgent need for integrated sediment and coastal management approaches to preserve the ecological stability and livelihood security of this globally significant delta.
How to cite: Dwivedi, D., Murali R, M., Mishra, P. K., and Francis, S.: Exploring Sediment–Morphodynamic Coupling in the Evolving Indian Sundarban Delta, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-464, https://doi.org/10.5194/egusphere-egu26-464, 2026.
Coastal wetlands are vegetated landforms that offer a multitude of ecosystem services to society. The vulnerability of these ecosystems to relative sea-level rise (RSLR) is connected to the amount of suspended sediment available in the adjacent water bodies. Sediment is transported by numerous processes onto the wetland surface, where it can contribute to vertical accretion and counteract RSLR. Here, we used maps of total suspended solids (TSS) concentration from the NASA Airborne Visible InfraRed Imaging Spectrometer Next Generation (AVIRIS-NG), numerical modeling, aerial imagery, and field observations to infer the mechanisms controlling wetland dynamics within western Terrebonne Bay, a sinking lagoon in the Mississippi River Deltaic Plain. Specifically, we aimed to understand how wetlands respond when land sinks, using western Terrebonne Bay as a test case. This study revealed that subsidence can augment suspended sediment in the water column by increasing tidal prism and triggering channel erosion. Sediment resuspension can support accretion in the remaining wetland platforms, ultimately affecting their elevation. Understanding these feedback mechanisms has direct implications for forecasting and managing the impacts of RSLR on wetlands in lagoons and river deltas.
How to cite: Fagherazzi, S., Donatelli, C., and Fichot, C.: Mechanisms of wetland deterioration in a sinking deltaic lagoon, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6003, https://doi.org/10.5194/egusphere-egu26-6003, 2026.
Global river estuaries are increasingly subjected to the compounding pressures of anthropogenic sediment starvation and climate-induced intensified marine hydrodynamics. While morphological degradation is widely reported, systematic and quantitative insights into the timing and mechanisms of non-linear transitions in estuarine evolution remain limited. The Nakdong River Estuary (NRE) in South Korea, an intensively engineered estuarine system controlled by cascading upstream dams and an estuarine barrage, serves as a paradigmatic case study to deconstruct this mechanism. Drawing on a 60-year (1965-2024) archive of high-resolution bathymetric data and Geomorphological Information Entropy (GIE) analysis, this study quantitatively reveals the regime shift of this mega-estuary from a sediment sink to an erosional source.
Our results indicate that the system maintained a state of metastable equilibrium for decades (1985-2017), masking the cumulative stress of artificial regulation. However, this fragile balance shifted post-2017, initiating an estuary-wide morphological transition. In the seven years from 2017 to 2024 alone, the system recorded a net erosion volume of over 100 million m3, with the annual erosion rate increasing to four times the historical average. We attribute this shift to the synergistic drive of the “Hungry Water” effect and extreme hydro-meteorological events: chronic sediment cutoff due to upstream damming, and channelization altered the morphodynamical impact of extreme floods (e.g., in 2020), transforming them from depositional events into high-energy erosive agents that scoured the riverbed and subaqueous delta. Concurrently, the degradation of barrier islands reduced the natural shelter effect, facilitating the intrusion of wave energy into the inner estuary.
This study demonstrates that anthropogenically transformed estuaries may exhibit apparent stability for decades before undergoing a rapid state transition, suggesting that such period may represent a lag phase preceding significant morphodynamical disorder. The observed transformation of the NRE provides a critical reference for understanding the trajectory of coastal systems worldwide, indicating that rigid engineering control may reduce system resilience against climate shocks. We suggest that under current climate trends, passive conservation strategies may be insufficient; a shift towards holistic source-to-sink sediment restoration, aimed at rebalancing sediment supply with hydrodynamic energy, is essential to mitigate long-term degradation in these vital coastal interfaces.
How to cite: Liu, D., Byun, E., Choe, Y., Kim, H., and Jia, L.: Unraveling the Multi-Decadal Morphological Regime Shift under Synergistic Drivers of Climate and Human Activity in a Hydro-Engineered Estuary, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8708, https://doi.org/10.5194/egusphere-egu26-8708, 2026.
The topography and surface sediment distribution of open-coast tidal flats exhibit distinct spatiotemporal variability, commonly linked to seasonal changes in wave intensity. However, studies that consider factors beyond waves and tides, or that address long-term variability based on extended observations, remain scarce. To investigate the processes shaping this variability, an Empirical Orthogonal Function analysis was applied to surface sediment data collected from 2014 to 2025 from the intertidal flat on southwestern Ganghwa Island, west coast of Korea.
The results indicate that sediment distribution is primarily influenced by interannual, decadal, and seasonal variability associated with wave forcing, as well as by geomorphic and biophysical changes. Interannual variability is most pronounced in the middle to upper tidal flat, where years of stronger wave conditions are characterized by relative coarsening. This pattern suggests that wave influence is modulated by tidal stage at the time of wave occurrence. Decadal variability reflects longer-term morphological change of tidal channels and the expansion of oyster reefs, producing a coarsening and fining trend, respectively. Seasonal variability exhibits clear elevation-dependent behavior: the middle tidal flat tends to coarsen in winter and fine in summer, whereas the upper tidal flat shows the opposite tendency due to biofilm development and rainfall-induced sheet flow.
Overall, these findings indicate that sedimentary processes on channelized open-coast tidal flats are governed by geomorphic complexity that enables multiple forcings, such as waves, tides, biological processes, and rainfall-driven sediment transport to operate concurrently. Consequently, surface sediment grain size distributions exhibit complex spatiotemporal variability that cannot be adequately explained by wave forcing alone, underscoring the value of integrated, long-term observations for resolving sediment dynamics in such environments.
How to cite: Bang, S., Jo, J., Kim, D., Sohn, S., and Choi, K.: Seasonal, annual, and decadal changes in morphology and sedimentation of a channelized, open-coast macrotidal flat, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9229, https://doi.org/10.5194/egusphere-egu26-9229, 2026.
Tidal-flat reclamation and coastal stabilization projects are widely implemented in the tide-dominated estuaries of eastern China, where intensive human intervention has profoundly altered sediment dynamics and morphological evolution. The Nanbei Lake reclamation area, located on the northern coast of Hangzhou Bay and the transitional reach of the Qiantang Estuary, China. This zone experiences strong semidiurnal tides, rapid current variations, and frequent typhoon impacts that shape highly dynamic geomorphic patterns. To mitigate erosion and promote siltation, a main embankment and seven rockfill groynes were constructed in 2007. However, long-term monitoring indicates that high crest elevations of the groynes have suppressed cross-shore water exchange, weakened tidal flushing, and promoted excessive sedimentation—patterns likely exacerbated by increasing storm-tide levels and evolving tidal asymmetry under climate change. To address these issues, this study evaluates a groyne-lowering scheme designed to enhance hydrodynamic connectivity while maintaining shoreline protection. A two-dimensional hydro–morphodynamic model (MIKE 21 FM) was developed using high-resolution bathymetry, tidal observations, and sediment data. The computational domain (~4000 km²) employs an unstructured mesh (minimum grid size 5 m) with 20 s time steps. Model calibration achieves strong agreement with measured tidal levels and velocities. The proposed scheme lowers the groyne crests by 0.2–2.5 m, increasing overtopping frequency during spring tides and enabling reactivation of intertidal exchange pathways. Model results reveal that groyne lowering significantly modifies the nearshore flow structure: bottom velocities increase by 0.005–0.050m/s, residual circulation strengthens between groynes, and previously stagnant zones behind the structures become reconnected. Morphodynamic responses over a spring–neap cycle indicate 0.2–0.4 m reduction in sedimentation near groyne heads, accompanied by mild accretion on the inner tidal flat, leading to a smoother, more gradually sloping intertidal profile. These changes reflect a shift toward a more dynamic and resilient morphodynamic state capable of better accommodating extreme water levels. This study highlights groyne lowering as an adaptive and nature-based intervention to counteract human-induced hydrodynamic restriction and climate-driven pressures. The findings contribute to improved understanding of eco-morphodynamic adjustment processes and offer guidance for sustainable coastal management in tide-dominated estuaries such as the Qiantang River delta.
How to cite: Zheng, Y., Li, X., Gong, M., and Shen, J.: Impact of groyne lowering on tidal-flat morphodynamics in a tide-dominated estuary, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2410, https://doi.org/10.5194/egusphere-egu26-2410, 2026.
As a critical interface between terrestrial and marine environments, bays experience significant land-sea interactions, with complex hydrodynamic processes playing a role in their water-exchange capacity. This study investigates how medium-sized rivers and the archipelago near the mouth of Yueqing Bay influence its water-exchange capacity. Half-exchange time, combined with a validated three-dimensional hydrodynamic model based on the Finite Volume Community Ocean Model, was used to assess the bay's water-exchange capacity. The results show that the half-exchange time in Yueqing Bay decreases from the bay head to the mouth, ranging from up to 30 days at the head to less than 1.5 days at the mouth, with an overall average of 8–9 days. Seasonal variations in river discharge, particularly from the Oujiang River, lead to changes in water-exchange capacity, with summer rates being 13.6% higher than those in winter. Additionally, a flood event increases water-exchange capacity near the mouth by 6.5%. The surrounding islands enhance tidal energy within the bay, resulting in an 11.6% increase in water-exchange capacity. This study provides valuable insights into the roles of river discharge and nearby islands in controlling water renewal processes, thereby enhancing understanding of the key mechanisms involved.
How to cite: Yan, Y., Gao, H., and Huang, J.: Water-exchange Capacity Induced by River Discharge and Bay Mouth Archipelago in a Macro-tidal Embayment, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2665, https://doi.org/10.5194/egusphere-egu26-2665, 2026.
Deltas worldwide suffer from very similar hazards such as elevation loss, fluvial sediment decline, river bed, bank and coastal erosion, flooding or drought, salt intrusion, biodiversity decline, hydrological regime shifts, leading in return to various socio-economic impacts. Yet, they are extremely complex and fundamental to the livelihood of more than half a billion people. They also often host mega-cities, thanks to their access to open seas and fertile soil for food production. Mekong Delta is not an exception. Specifically, in the past two decades it has been largely impacted by increased trends of salt intrusion. When studying salt intrusion in the Mekong Delta, we could identify a very wide range of drivers from all the way upstream in the basin to the coastal seas. Some of them are driven by climate change, and some by human intervention. Looking at the past trends and future projection when combining all the drivers of change, we see that anthropogenic drivers dominate those dynamics in the first half of the century while in the second half of the century perhaps climate change becomes the dominant driver of change.
The Mekong Delta is exemplar of the challenges many deltas face today worldwide. But, when studying them collectively, we can identify common drivers of biophysical change across a range of spatial and temporal scales. When mapping these drivers at various scales and linking them to their direct and indirect biophysical and societal impacts we can develop a more clear systems understanding as a very important step in the adaptation planning. Furthermore, this framework can help facilitating dialogue among various stakeholders, and simplify a more critical thinking for policy makers, public and technical sectors. This system understanding of a delta from its source to its sink, is a critical first step in effective and sustainable adaptation planning, while it often gets less resources associated than it deserves.
How to cite: Eslami Arab, S., Oude Essink, G., Nicholls, R. J., and Sharma, V.: Salt intrusion in the Mekong Delta and a systems perspective for climate adaptation in deltas worldwide, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17682, https://doi.org/10.5194/egusphere-egu26-17682, 2026.
Managed realignment is an effective solution in coastal management. This typically involves breaching existing coastal defences, allowing flooding of previously protected land and creation of intertidal habitat, and relocation of the line of actively maintained defences inland. In the UK, creation of intertidal habitat by managed realignment is recommended by strategic plans, yet the uptake of schemes is not keeping pace to meet self-selected targets. The underlying reasons for this slow uptake are complex, span multiple interacting disciplines and are not fully understood. A critical aspect relates to the long-term sustainability and success of the scheme. We explore here how the response of managed realignment to climate drivers leading to intended and unintended consequences intersect with community perceptions.
We focus on a case study in the UK (Hesketh Out Marsh in the Ribble Estuary) where we integrate community co-production with quantitative modelling and long-term environmental datasets. We bring together outcomes from co-creating a shared understanding of the managed realignment system with stakeholders and the local community, with results from downscaled hydrodynamic modelling of the Ribble estuary under present and future sea level, and with LiDAR and Sediment Erosion Table datasets for Hesketh Out Marsh.
Our results show that the managed realignment have both positive and negative influences on the overall social-ecological system. Hydrodynamic modelling results show significant spatial variability in the effect of the managed realignment scheme, which is amplified by sea level rise. In some areas, managed realignment is beneficial but in others it is not. The newly created saltmarsh is slowly accreting, which is beneficial against sea level rise and its long-term viability, but impairs drainage of its terrestrial hinterland. Workshops with local stakeholders revealed entrenched and conflictual perceptions of the process, goals, and effectiveness of the managed realignment scheme. Altogether, this demonstrates the complexity inherent to managed realignment social-ecological systems. Transdisciplinary approaches are critical to better incorporate this complexity into management approaches by enabling to bring together multiple voices and knowledges and to co-create a clearer, more complete shared understanding of the system.
How to cite: Amoudry, L., Payo Payo, M., Meschini, M., Apine, E., Becker, A., Garbutt, A., Brown, J., Dunning, R., Evans, C., Graves, A., Jude, S., Matsoukis, C., Plater, A., Robinson, L., and Welivita, I.: Response of saltmarsh recreation by managed realignment to climate and coastal community drivers, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13027, https://doi.org/10.5194/egusphere-egu26-13027, 2026.
Posters virtual: Tue, 5 May, 14:00–18:00 | vPoster spot 1a
EGU26-3596 | ECS | Posters virtual | VPS20
Coastal Features Segmentation and Assessing their dynamics Using Machine Learning: Random ForestTue, 05 May, 14:36–14:39 (CEST) vPoster spot 1a
Estuaries represent complex morphodynamic systems where interactions between tides, waves, and sediment processes control coastal stability and its ecological resilience. One such estuary, located along the bank of the Purna River in Navsari District, Gujarat, India, is currently experiencing severe erosion, with nearly two-thirds of the estuarine coastline affected. Understanding spatio-temporal evolution of key coastal features is essential, including tidal flats, salt marshes, mangrove cover, and anthropogenic infrastructures within the study region. In this study, the coastal features segmentation is performed using the Random Forest on derived Landsat satellite imagery spectral indices spanning 2005–2024. The results indicate that over the past two decades, mangrove cover has increased by more than twofold, particularly near the estuary mouth. In contrast, tidal flat areas exhibited significant spatial variability, while salt marshes showed a considerable decline.
Shoreline change analysis shows extensive coastal erosion with the Net Shoreline Movement (NSM) exceeding 150 m in certain stretches, while the End Point Rate (EPR) ranged from 1.5 to 17 m/year (mean: 9.5 m/year). The analysis further indicates significant accretion in the estuaryward region and pronounced erosion along the seaward coast near its mouth. Further the coupled tide-wave numerical modelling was carried to attribute the observed changes. Overall, the findings highlight the complex interplay between natural coastal processes and anthropogenic pressures in this dynamic estuarine coastal system and provide valuable baseline information for coastal zone management and conservation planning.
Keywords: Estuary Dynamics, Random Forest, Shoreline changes, Tide Modelling, Wave Modelling, Remote Sensing.
How to cite: Makhan, P. K., Goud Lakku, N. K., Behera, M. R., and Vijaya Kumar, S.: Coastal Features Segmentation and Assessing their dynamics Using Machine Learning: Random Forest, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3596, https://doi.org/10.5194/egusphere-egu26-3596, 2026.
EGU26-10444 | Posters virtual | VPS20
Influence of Offshore Wind Farm Monopiles on Multi-Scale Hydrodynamics and Sediment Transport in a Wave-Current EnvironmentTue, 05 May, 14:39–14:42 (CEST) vPoster spot 1a
The rapid expansion of offshore wind energy infrastructure represents a major anthropogenic modification of coastal and marginal seas, yet the physical interactions between monopile foundations, hydrodynamics, and sediment transport remain insufficiently quantified. This study investigates the impact of monopile foundations at the Meerwind offshore wind farm (German Bight, North Sea) on local and regional coastal dynamics. Using a high-resolution coupled wave-current-sediment transport model, we analyze hydrodynamic and sediment processes with mesh refinement of ~2 m near the structures to capture turbulent wake effects.
Our results demonstrate that monopile arrays act as significant sinks for wave energy: monthly mean significant wave heights (Hs) and mid-depth velocities decrease by ~5%, while turbulent kinetic energy increases by up to 70% near the foundations. Dominant westerly wind-driven waves modulate tidal asymmetry on the leeward (eastern) side of the piles, generating asymmetric turbulent wakes and altering bottom shear stress patterns.
Reduced wave-induced bottom stress enhances localized sediment deposition, increasing surface suspended sediment concentration (SSC) while reducing near-bottom loads. On a regional scale, wave attenuation leads to a ~1% decrease in depth-averaged SSC over a 20 km east of the piles. In consequence, the presence of the wind farm reduces the net inflowing sediment flux by ~25% within a 5 km radius during March 2020, linked to a ~2 cm attenuation of Hs.
These findings highlight how large-scale offshore energy infrastructure can reorganize sediment budgets and coastal morphodynamics under changing human activities, providing critical insights for the sustainable management of multi-use ocean spaces. Further work, including additional wind farms and extended simulation periods, is planned to substantiate these initial findings and better quantify cumulative impacts, particularly in light of ongoing erosion challenges in the Wadden Sea under sea-level rise.
How to cite: Hosseini, S. T., Pein, J., Staneva, J., Stanev, E., and Zhang, Y. J.: Influence of Offshore Wind Farm Monopiles on Multi-Scale Hydrodynamics and Sediment Transport in a Wave-Current Environment, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10444, https://doi.org/10.5194/egusphere-egu26-10444, 2026.
