Wetlands are dynamic ecosystems where land and water environments intersect, playing a vital role in maintaining ecological balance. These areas are critical for the conservation of biodiversity and regulation of water regime. The Kızılırmak Delta, is recognized as a wetland complex consisting of rivers, lakes, swamps, coastal, and marine regions is recognized as one of the "Strictly Protected Areas" and listed on the UNESCO “World Heritage Tentative List” due to the presence of wetlands and its significance as a crucial bird migration route. 

The Holocene evolution of the Kızılırmak Delta (Northern Türkiye) is controlled by accumulation and alongshore transportation of sediment flux by the largest river of Anatolia draining to the Black Sea. The distinct successive beach ridges (~2 km length) formed along the eastern part of the delta (north and east) form the geomorphological boundaries of the wetland systems. The formation of these beach ridges reflects the variations of sediment influx, alongshore transport, and coastal dynamics. Optically Stimulated Luminescence (OSL) dating revealed that the formation of the beach-ridge system initiated during the last millennium.

Since the mid-20th century, a dense network of drainage canals (~1400 km) have been constructed to drain the delta for agricultural purposes. The successive construction of large-scale dams along the river have caused interconnected issues, such as decrease of sediment flux and negative balance underground water table of the delta. 

In this regard, we have conducted an analysis of wetland changes over the past 10 years, during which climate change and anthropogenic impacts have been heavily observed. Sentinel-2 imagery (#92) and meteorological data (daily) were used to classify, map and understand the spatiotemporal hydrological dynamics of the wetlands and anthropogenic control. The present study aims to contribute to the analysis of the geomorphological development and evolution of the delta and its recent hydrological dynamics.

How to cite: Salman, I. and Erturaç, M. K.: Monitoring the natural and anthropogenic environmental changes in the Kızılırmak Delta using remote sensing methods over the last 10 years, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1070, https://doi.org/10.5194/egusphere-egu25-1070, 2025.

Prestige reclamation is defined as coastal reclamation carried out for the purpose of high-end real estate development and luxury recreation. The planiforms of these reclamations are often highly complex ideograms, showcasing the investor’s wealthand maximising the number of waterfront properties. Over time, increasingly elaborate designs are being built, leading to ever more complex coasts of which the wider impact to the coast is poorly understood. 

As these constructions are becoming more common, we raise a series of critical questions on the ecological, societal and environmental status of these highly anthropomorphised coasts. In this presentation we highlight ten key global prestige reclamation sites; showcasing trends in design, diversity of symbolic representation and resource demands, to demonstrate common themes found widely across the existing prestige reclamations. Time series analysis of reclamation shows both the construction timeframes, but also the large gap in time between construction and further development, questioning the drivers for development. This presentation aims to spark conversations on these unique coastlines, and bring further attention and global collaboration to collectively study their impact on the wider coastal environment. 

How to cite: Sengupta, D., Townsend, D., Brown, S., Haigh, I. D., and Townend, I.: Claiming Prestige: Shaping the Future of Artificial Coastal Development", EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1123, https://doi.org/10.5194/egusphere-egu25-1123, 2025.

The large radial sand ridge (RSR) system located in the southern Yellow Sea near the Jiangsu coast, China, is highly impacted by tropical cyclones (TCs). However, the temporal and spatial variations of sediment dynamics and associated morphodynamics in this region under the influence of TCs have been little explored due to the difficulty of implementing direct observation during these extreme events. Taking typhoon Lekima in August 2019 (No. 1909) as an example, this study simulated and comprehensively investigated the dynamic processes in the RSR area under the impacts of TCs based on the Finite Volume Coastal Ocean Model (FVCOM). During the passage of Lekima, the spatial patterns of residual flow (RF), sediment flux (SF) and morphology changes in the RSR area were totally different from that during the pre- and post-Lekima periods, especially in the offshore areas (the seaward edge of sand ridges). This is because TC Lekima can generate strong wind-driven currents and waves, increasing the bottom stress and influencing the sediment transport. Due to the shallow water depth of RSRs, wave height decreased significantly towards the coast, and tidal effects gradually dominated the nearshore sedimentary dynamic processes instead of wave effects. Furthermore, the effects of TCs with different tracks and intensities were discussed in this study, and we found that TCs passing the west/east side of the study domain can induce opposite directions of sediment transport and lead to the spatial asymmetry of geomorphological evolution. This research can contribute to an improved understanding of sedimentary dynamic processes during extreme events and indicates the importance of exploring sediment dynamics response to TCs with different characteristics for reducing TC-induced coastal risks in future climate change scenarios.

How to cite: Yang, G.: Impact of tropical cyclones on the hydrodynamics and sediment dynamics of the radial sand ridge system in the southern Yellow Sea, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1614, https://doi.org/10.5194/egusphere-egu25-1614, 2025.

Coastal farmland is becoming increasingly exposed to flooding due to climate change. Inundation can lead to groundwater and soil degradation through saltwater intrusion. Much of the research investigating saltwater intrusion is focused along the marine coast; however, as storm intensity and sea levels rise, transitional coastal areas not previously susceptible to salinization may be at risk. Flood-derived sediment deposits may provide an overlooked salinity source in estuarine and upriver areas, even where floodwater salinity is relatively low. This study was conducted to evaluate the impact of subaerial flood deposits on underlying soil and porewater. A parcel of agricultural land in an estuarine floodplain in Nova Scotia, Canada, was selected to assess the subsurface response to repeated, low-salinity flooding. The site experienced inundation by fortnightly tidal floodwater following a managed dike realignment, resulting in dynamic surficial alteration. A three-year field campaign, including soil and water monitoring, geophysical surveying, and drone-based LiDAR surveying, was conducted to monitor changes to the site geomorphology and water and sediment chemistry. A one-dimensional numerical solute transport and vertical water flow model informed by field data was applied to investigate the hypothesis that saline sediment deposits can drive downward saltwater intrusion in areas experiencing brackish or low-salinity flooding. Results revealed that the soil concentrations exceeded that of the brackish floodwater by up to 50 times, with the highest salinization occurring preferentially in areas experiencing persistent deposition. Model results showed that soil salinization may persist for decades longer than the duration of flooding; however, removing these deposits through erosion resulted in soil and groundwater recovery. This study highlights the potential importance of flood-derived sediments for exacerbating saltwater intrusion in riparian areas along estuaries, which were not previously thought to be at risk of saline flooding.

How to cite: Tackley, H., Kurylyk, B., Lake, C., van Proosdij, D., and Jamieson, R.: Sediment deposition in riparian zones exacerbates saltwater intrusion, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2593, https://doi.org/10.5194/egusphere-egu25-2593, 2025.

Fjords are strongly affected by climate change and direct anthropogenic impacts. Their location at the land-ocean interface makes them particularly vulnerable to a wide range of stressors. Rapid changes, such as increasing water temperatures, changes in oxygen conditions, increased run-off from land and decreasing sea ice in the Arctic will inevitably have profound effects on marine biodiversity and productivity. However, so far, our knowledge on the impact of these changes on marine communities remains limited, despite their important roles in food webs and nutrient cycling. To understand ongoing and future changes in fjord ecosystems and the resilience of marine communities, it is essential to assess their response to past changes in environmental conditions. To date, such studies are limited to lineages with a fossil record, leaving an incomplete picture of the remaining diversity. To address this issue, in the project PASTIME we are now applying sedimentary ancient DNA as a new tool for reconstructing past changes in entire marine communities in relation with past environmental changes. We focus on marine sediment cores from Arctic and western Norwegian fjords and assess environmental and biodiversity changes over the last centuries. Our work extends the timescales far beyond traditional observational data and allows assessing the impact of various environmental factors (e.g. temperature, freshwater inflow, sea ice, oxygen) under in-situ conditions to elucidate key drivers of change. In addition, the high sedimentation rates in fjords allow for high temporal resolution sampling and thus for tracing the rate of ecosystem change. Here, we will present preliminary data on one sediment core collected in Kongsfjorden, Svalbard, and one core from Masfjorden, Western Norway. Both cores cover the last three centuries with a high vertical resolution and show marine community responses to past environmental changes.

How to cite: Husum, K., Saetersdal, I., Lacka, M., Risebrobakken, B., Haflidason, H., Dunthorn, M., Cordier, T., Larsen, A., Varpe, Ø., de Schepper, S., and Weiner, A.: Assessing the impact of past environmental change on fjord biodiversity using sedimentary ancient DNA, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4284, https://doi.org/10.5194/egusphere-egu25-4284, 2025.

Offshore freshened groundwater (OFG) is well-documented in the shelf sediments of Canterbury Bight (New Zealand), with an estimated maximum volume of 213 km³, extending up to 60 km offshore from the coast. However, the evolution and emplacement dynamics of the OFG system remains poorly constrained. To advance the current state of understanding OFG systems, this study seeks to utilize the previously underutilized IODP geochemical and geological data from the Canterbury Bight to constrain the timing and emplacement mechanisms of the OFG system. Specifically, the main objectives of this paleo-hydrogeochemical transport-reaction modelling study are: (1) to identify key factors/processes influencing groundwater salinization and flushing in the continental shelf; (2) to improve understanding of the influences of OFG on subseafloor biogeochemical processes by transport-reaction modelling; (3) to explore the interactions between paleo-groundwater system and seawater; and (4) to propose a conceptual mode for shelf groundwater system evolution in relation to glacial/interglacial processes.

Preliminary results suggest that present-day recharge does not fully account for the OFG, particularly in the outer shelf, which is the fossil groundwater emplaced during the lowstands since the late Pleistocene. The intensified sulphate depletion observed in freshening sections is attributed to enhanced anaerobic oxidation of dissolved organic matter brought by the OFG. Modern salinity conditions are not in equilibrium with present-day sea level conditions, as the OFG is gradually being salinized through downward solute transport from overlying seawater. Submarine groundwater discharge and OFG volume are interconnected components of the offshore paleo-groundwater system, both closely tied to sea-level fluctuations. The findings from this study are expected to enhance our understanding of the Canterbury Bight’s offshore groundwater system and provide broader insights into OFG formation and evolution under changing climatic and sea-level conditions worldwide.

How to cite: Sheng, C., Micallef, A., Schmidt, M., Müller, T., and Hensen, C.: Unravelling groundwater salinization and flushing in the Canterbury Bight during glacial-interglacial cycles: Insights from paleo-hydrogeochemical modeling, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4809, https://doi.org/10.5194/egusphere-egu25-4809, 2025.

Topographic change, its dynamic mechanism, and the long-term evolution of a coastal sand dune in northwestern Taiwan was discussed through the monitoring of the seasonal and interannual topographic changes and sedimentological studies. The strong northeast monsoon in winter often blows up the dry sand on the back beach, and transports the sand landward  along the coast. The sedimentary structure analysis of the foredunes also shows that different types of parallel and cross laminations are dominant at different dune locations.

In summer, the foredune is susceptible to the influence of typhoon waves and storm surges, and often erodes the fore slope to form dune scarp. However, in the following winter, the scarp can gradually return to the dune slope through the accumulation of the dune ramp and the slope slumping. Overall, the foredune ridge has been moving inland toward southeast over the decades. Several sites of sand encroachment onto the windbreak forests are identified. The artificial sand fences on the fore slope make the surrounding sand surface piled up, and the fore slope becomes steeper that more likely to cause large-scale slumping.

The results of the ground penetrating radar survey showed that the surface sediments of the foredunes were about 5-10 meters thick, showing low-angle parallel bedding. Below the existing dune sediments, the distribution of the strata under the dunes (i.e. algal reef layer, old dune sediments, and salt marsh mud) can be observed. Vibration sediment core samples also show that there is an algal reef platform below the beach and dune deposits in this area, which is exposed at the lower fore beach and could extend at least few hundred meters to the inland side. The sea level at the time of the formation of the algal reef platform (about 3,000-4,000 years ago) may have been higher, and the secondary sand dunes on the current inland side may be the foredunes at that time.

How to cite: Lin, T.-Y., Lu, S.-P., and Liou, J.-M.: Morphodynamics and Evolution of a Coastal Sand Dune in Northwestern Taiwan, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5126, https://doi.org/10.5194/egusphere-egu25-5126, 2025.

Lagoon coasts are regarded as among the most vulnerable ecosystems to the effects of climate change, serving as conduits for interconnectivity between terrestrial, marine, and atmospheric systems. The stability of lagoons is contingent upon several factors, including the influence of storm waves, ocean currents, sediment supply, and sea level changes. To date, however, little research has been conducted on the processes shaping the evolution of Arctic coastal lagoon systems (Smith et al., 2020). The present study utilises a comprehensive array of remote sensing data sources, encompassing aerial photographs from the 1930s, orthophotographs from 1936–1938, and satellite imagery from 2021, to identify lagoon formation and systematically classify their typology.

The construction of a database comprising over 430 lagoons revealed that at least 98 of these were formed after 1936, with eight disappearing within a century. Since the end of the last ice age (LIA), at least 98 new lagoons have been formed, resulting in the current Svalbard coastal environment comprising 434 lagoons spanning 147 km². A new lagoon type currently rapidly forming across the archipelago, is the moraine-controlled paraglacial lagoon. These lagoons form as a consequence of glacial retreat and subsequent inundation of the area between moraines and glacier ice-cliffs by the sea. The majority of observed lagoons are characterised by resistant barriers capable of withstanding strong storms. In general, the factors controlling the stability of Svalbard lagoons remain poorly understood. This is partly due to the fact that permafrost has not yet been thoroughly studied in the area and partly due to the fact that the distribution of sub-lagoon permafrost is not yet fully understood.

Keywords: lagoon systems, moraine-controlled paraglacial lagoons, coastal change,
glacier retreat, Svalbard, Arctic.

Funding: This research was funded in whole by the National Science Centre in Poland (project: Arctic storm impacts recorded in beach-ridges and lake archives: scenarios for less icy future “ASPIRE” – UMO-2020/37/B/ST10/03074)

How to cite: Owczarek, Z. and Strzelecki, M.: Post-Little Ice Age evolution of Svalbard's lagoon systems – types, changes, and responses to storms, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6108, https://doi.org/10.5194/egusphere-egu25-6108, 2025.

The Bohai Sea, a semi-enclosed inland sea located in China, has experienced a notable decline in bottom water oxygen levels over the past decade. This phenomenon is linked to the inadequate replenishment of oxygen, which is constrained by the formation of summer thermoclines that impede water renewal. The impact of global climate change on oceanic thermoclines has been pronounced. This research employs a sophisticated three-dimensional hydrothermal model in conjunction with a vertical water age model to investigate the formation and spatiotemporal characteristics of thermoclines in the Bohai Sea, as well as their response to climate change, including shifts in wind patterns and air temperature. Water age is conceptualized as the duration since a water parcel last contacted the free surface. Findings indicate that the bottom water age in the Bohai Sea remains less than 2 days in spring, suggesting that the cold bottom waters are not remnants from the winter season. The intensified surface heat flux during summer points to a thermal lag as the underlying mechanism for thermocline formation, with bottom waters warming at a slower rate than surface waters. The study reveals marked spatial heterogeneity and seasonal fluctuations in the thermocline’s distribution within the Bohai Sea. Over time, the thermoclines have exhibited a vertical descent towards the seafloor and a horizontal shift from the continental slope towards the central basin. Regarding the impacts of climate change, a trigonometric function fitting method was utilized to discern a trend of increasing wind speeds and temperatures in the Bohai Sea over the past forty years. The temperature rise leads to a downward shift of the thermocline and an intensification of its strength. Moreover, enhanced wind speeds facilitate greater vertical mixing of water masses, culminating in a weakening of the strength of the thermocline.

How to cite: Wu, M. and Sun, J.: Spatiotemporal Distribution and Climate Change Sensitivity of Thermoclines in a Semi-Enclosed Sea, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7788, https://doi.org/10.5194/egusphere-egu25-7788, 2025.

To understand the evolution of the Qiongzhou Strait and ancient coastlines in the Beibu Gulf - Leiqiong area since the Cenozoic era, and to reveal its implications for regional land-sea pattern changes and global climate change. This article reconstructs the changes of ancient coastline and the evolution process of Qiongzhou Strait in the Beibu Gulf - Leiqiong area since the Cenozoic era based on borehole data. In the Paleogene, the Beibu Gulf formed a NEE trending disconnected fault basin and filled with river lake sedimentary facies. In the late Oligocene, seawater intermittently invaded the ancient Beibu Gulf lake and connected the isolated fault basin;In the Early-Middle Miocene（23.3~10.4 Ma）, the coastline in the northwest of the South China Sea rapidly retreated, and the ancient lake in the Beibu Gulf evolved into the ancient Qiongzhou Strait. In the Late Miocene to Pliocene （10.4~2.58 Ma）, the coastline continued to retreat, forming a wide ancient Qiongzhou Strait, Early Pleistocene regression and volcanic eruptions led to the shrinkage of the ancient Qiongzhou Strait；Frequent climate fluctuations during the late Early Pleistocene to late Pleistocebe controlled the continuous transformation of fjords and land. The significant regression during the last glacial maximum directly led to the transformation of the Beibu Gulf-Leiqiong area from sea to land; Since 15 ~ 12 ka BP, the coastline has rapidly retreated and briefly stopped between 12 and 11 ka BP, and the Beibu gulf has once again transitioned from land to sea, Afterwards, the sea level continued to rise, and the Qiongzhou Strait fully opened from west to east at 11 ka BP. By 6 ka BP, the sea level reached about 2 meters above the current sea level, forming the current sea land pattern. The results indicate that the Beibu Gulf - Leiqiong Area underwent four evolutionary stages in the Cenozoic, including the Paleogene Beibu Gulf ancient lake, the Neogene to Early Pleistocene ancient Qiongzhou Strait, the late early Pleistocene to late Pleistocene fjords, and the Holocene Qiongzhou Strait.

How to cite: Wang, C., Yang, X., and Hu, D.: Reconstruction of the Cenozoic Paleocoastline and Evolution of the Qiongzhou Strait, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7828, https://doi.org/10.5194/egusphere-egu25-7828, 2025.

Climate change is driving significant temperature increases in the Arctic region—over four times the global average—impacting fish populations that are highly sensitive to thermal variations. Elevated water temperatures enhance the metabolic oxygen demands of fish while simultaneously decreasing oxygen solubility in seawater. This dual effect may force fish to migrate to more favorable habitats or face higher mortality rates. While previous studies have primarily focused on the relationship between water temperature and fish catches, the influence of dissolved oxygen has remained understudied due to limited data availability. In this study, we utilized reconstructed ocean biogeochemical data from the Geophysical Fluid Dynamics Laboratory Earth System Model (GFDL-ESM2) covering the Arctic and Subarctic Exclusive Economic Zones (EEZs) from 1970 to 2017 to calculate a metabolic index that integrates both temperature and dissolved oxygen levels. Our findings demonstrate a strong correlation between the metabolic index and the catches of large demersal fish species. Permutation importance analysis revealed that dissolved oxygen often plays a more critical role than temperature in determining fish catches across numerous regions. Additionally, fish catches in subsurface areas with higher dissolved oxygen importance exhibited longer lead times in predictability, likely due to the prolonged persistence of biogeochemical conditions. Projecting into the future under various Shared Socioeconomic Pathway (SSP) scenarios up to 2100, our results consistently indicate a continued decline in fish catches across all scenarios. These outcomes highlight the urgent need to incorporate the physiological characteristics of fish into sustainable fisheries management practices to mitigate the adverse effects of changing ocean conditions in the Arctic and Subarctic regions.

How to cite: Kim, E., Park, J.-Y., and Lim, H.-G.: Projected Decline in Arctic and Subarctic Commercial Fish Catches: Insights from Reconstructed Ocean Biogeochemical Modeling, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7842, https://doi.org/10.5194/egusphere-egu25-7842, 2025.

Wetlands serve as coastal protection structures via hydrological and biogeochemical processes (Junk et al., 2013), preventing soil erosion (Barcelona et al., 2018) and promoting sedimentation and soil stabilization (Montakhab et al., 2012).  Wetlands contribute to mitigate the impacts of peak flows caused by pluvial or fluvial floods or storm surges. The increase in global warming will affect coastal areas with an increase in sea level and erosive processes (Reed et al., 2018), and an increase in the frequency of hydrometeorological phenomena such as coastal flooding and maritime storms (Hoggart et al., 2014). Inland wetlands are also to be increasingly affected by pluvial and fluvial floods (Kundzewicz and Pinskwar, 2020). It is then necessary to add knowledge on the impacts of both the wetland inundation level and the vegetation water resistance on hydrodynamics and sedimentary patterns in front of a peak flow to know the wetland benefits in front of flooding events. In this study, particle ladden floods were reproduced by flume experiments were a peak flow (of water height H) flowed into a wetland with a water height h (where H > h) populated with two natural species (Juncus maritimus and Arthrocnemum fruticosum). The peak flow was found to pass through different regimes with different sedimentation patterns: peak flow adjustment; peak flow; drag-dominated peak flow; ending to the gravity current regimes. During the peak flow regime, low-inundated wetlands induced higher sedimentation rates for the coarse sediment fraction than for the fine sediment fraction, while high-inundated wetlands resulted in similar settling rates for both sediment fractions, coarse and fine. Because the coarse portion has already settled, at greater distances sedimentation rates corresponded to the fine fraction and dropped monotonically along the flume.  It was also found that the presence of vegetation enhanced the sedimentation rates compared to bare soil conditions.

This finding demonstrates how crucial vegetation is to protect the bed and prevent bed erosion in coastal regions when facing peak flows and how higher inundation levels reduces the harmful effect of the front pass by enhancing the sediment deposition.

References

Barcelona, A., Serra, T., Colomer, J., 2018. Fragmented canopies control the regimes of gravity currents development. J. Geophys. Res-Oceans, 123, https://doi.org/10.1002/2017JC01314

Hoggart, S.P.G., Hanley, M.E., Parker, D.J., Simmonds, D.J., Bilton, D.T.,  Filipova-Marinova, M., Franklin, E.L., Kotsev, I., Penning-Rowsel, E.C., Rundle, S.D., Trifonova, E., Vergiev, S., White, A.C., Thompson, R.C., 2014. The consequences of doing nothing: The effects of seawater flooding on coastal zones. Coast. Eng. 87, 169–182. https://doi.org/10.1016/j.coastaleng.2013.12.001

Junk, W.J., An, S., Finlayson, C.M., Gopal, B., Kveˇt, J., Mitchell, S.A., Mitsch, W.J., Robarts, R.D., 2013. Current state of knowledge regarding the world’s wetlands and their future under global climate change: a synthesis. Aquat. Sci. 75, 151–167. https://doi.org/10.1007/s00027-012-0278-z.

Kundzewicz, Z.W., Pinskwar, I., 2022. Are Pluvial and Fluvial Floods on the Rise? Water 2022, 14, 2612. https://doi.org/10.3390/ w14172612

Montakhab, A., Yusuf, B., Ghazali, A. H., Mohamed, T. A., 2012. Flow and sediment transport in vegetated waterways: a review. Rev. Environ. Sci. Bio. 11(3), 275-287. https://doi.org/10.1007/s11157-012-9266-y

How to cite: Soler, M., Colomer, J., Folkard, A., and Serra, T.: Inundation levels and vegetation:  keys to control peak flows in wetlands, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10042, https://doi.org/10.5194/egusphere-egu25-10042, 2025.

Climate change is transforming coastal ecosystems by altering key processes such as freshwater inputs, salinity, and stratification, which drive nutrient dynamics, primary productivity, and carbon cycling. This study explores the dynamics of chlorophyll concentration (as a proxy for local planktonic biomass) in the Gulf of Naples (GoN) within the Mediterranean Sea. Leveraging long-term monitoring data and machine learning, we identify the local drivers of chlorophyll concentrations as a combination of physical and biogeochemical conditions. Notably, salinity emerges as a key predictor of chlorophyll, emphasizing the critical role of freshwater inflows and mixed layer dynamics. We develop an empirical model to estimate salinity based on freshwater discharge and stratification, which proves robust even with simplified inputs. By combining these predictors with future climate projections (RCP4.5 and RCP8.5), we assess the potential impacts of changing precipitation and wind patterns on salinity and chlorophyll. Results suggest increasing salinity and declining chlorophyll concentrations, particularly in spring, while uncertainties persist for autumn trends. Crucially, changes occurring on land may have a greater impact than those at sea (e.g., temperature) on coastal ecosystems, particularly their microbiomes, which form the foundation of the main trophic webs. These findings highlight the importance of long-term monitoring and infrastructure development to enhance ecosystem management under future climate scenarios.

How to cite: Kokoszka, F., Lefebvre, C., Asdar, S., Buongiorno Nardelli, B., Mercogliano, P., Ribera d'Alcalá, M., Margiotta, F., and Iudicone, D.: Chlorophyll variability in a Coastal Ecosystem: Insights from Recent Decades and Future Projections, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11715, https://doi.org/10.5194/egusphere-egu25-11715, 2025.

Wind-induced currents are the major forces responsible for sediment resuspension and transport in micro-tidal bays. The hydrodynamics and sediment transport mechanisms were investigated in Onsan Bay, a heavily contaminated, micro-tidal area on the southeastern coast of Korea, designated as a “Special Management Coastal Zone” due to severe pollution. At two mooring stations (M1: central part of the bay; M2: entrance of the bay), in-situ measurements using acoustic Doppler current profilers (ADCPs) were conducted to examine the impact of wind-induced residual currents on the sediment flux over four weeks. During the mooring period, residual currents (ū) in both stations showed classical estuarine circulation characterized by seaward (landward) flows at the surface (bottom) layers. The suspended sediments at both stations were transported seaward (landward) at the surface (bottom) layer mainly through the residual currents (mean-flow flux F_mean: > 70% of the total flux). Under northerly winds, the bottom ū at M1 and M2 strengthened, with a higher increment at M1. This result implies that the intrusion of alongshore currents through the bottom layer strengthened under northerly winds. The landward F_mean at M1 (M2) was 1.4 (1.2) times higher under northerly winds than southerly winds, resulting in the quadruple “intensification” of net sediment flux. This observation was attributed to the enhanced landward water transport and the weak sediment resuspension by wind-induced residual currents. This suggests that the northerly winds might be a primary factor intensifying the landward sediment fluxes, potentially resulting in the increased sediment deposition into the bay. The findings provide insights into managing sedimentation in contaminated coastal bays and highlight the importance of wind effects on sediment transport in micro-tidal bays.

How to cite: Eun, C. Y., Choi, S. M., Seo, J. Y., Ryu, J., and Ha, H. K.: Wind-induced residual current as a driver of sediment flux intensification in a shallow, micro-tidal bay, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15209, https://doi.org/10.5194/egusphere-egu25-15209, 2025.

Typhoons significantly influence sediment resuspension through the mixing induced by strong winds, which alters the local current patterns and sediment dynamics. An acoustic Doppler current profiler was moored in Yeosu Bay from August 19 to September 20, 2022, to investigate the effects of typhoon on sediment transport mechanisms. Before the typhoon, the mooring station exhibited a strong stratification of water column caused by freshwater inflow from the Seomjin River. On September 6, 2022, Typhoon Hinnamor passed through the study area, disrupting the semi-diurnal current regime and associated sediment transport. Under the influence of the typhoon, the residual current profile transitioned from a two-layered structure to a fully mixed structure. Strong winds (~16 m s^–1) affected the stability of bed sediments and stratification, resulting in significant differences in suspended sediment concentration (SSC) during spring tides before (S_I) and after (S_II) the typhoon. Despite similar current-induced bed shear stress, the SSC during the S_II period reached up to 350 mg l^–1, which was about four times higher than during the S_I period (87 mg l^–1). Near-bed sediment fluxes controlled by tidal pumping increased during the S_II period (54%) compared to the S_I period (29%) and transport landward. This suggests that suspended sediments advected from the Seomjin River due to the typhoon settled in Yeosu Bay, resulting in the bed stability decrease. Along with suspended sediments, the typhoon led to an input of terrestrial nutrients from the Seomjin River, which could affect the biological productivity of Yeosu Bay. The results from this study indicate that Typhoon-induced disturbances of coastal currents could significantly affect sediment resuspension and transport, highlighting the complex interactions between meteorological forcing and sedimentary processes in coastal environments.

How to cite: Kim, S. I., Choi, S. M., Jeong, S. W., Park, J.-H., Kim, P. J., and Ha, H. K.: Typhoon-induced sediment dynamics: Effects of extreme winds on resuspension and transport in Yeosu Bay, Korea, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15389, https://doi.org/10.5194/egusphere-egu25-15389, 2025.

Coastal areas are high dynamic environments which, especially considering the present climate conditions, are undergoing huge morphological changes mostly in terms of erosion. The retreat of coastal slopes, either progressive or sudden, is the result of the interaction between marine and terrestrial processes acting on specific litho-structural contexts.

The analyses of retreat style and relative rate can be lead combining field measurements and high-resolution remote sensing techniques. These approaches allow the quantification of erosion trend and the identification of the key factors driving the observed changes over time. The integration of multi-techniques measurement strengthens the evaluation of the interplay between terrestrial and marine processes and litho-structural factors, such as lithological variability, enabling a detailed understanding of how different coastal typologies respond to these processes.

Within the framework of the extended partnership RETURN (multi-Risk sciEnce for resilienT commUnities undeR a changiNg climate - Italy’s National Recovery and Resilience Plan), our study focuses on the evolution of a segment of the southern coast of the Lazio region (Italy). The study area is characterized by a soft-rocky cliff and shore platform system, partially emerged and partially submerged, where a high cliff retreat rate has been observed. To this end, multitemporal surveys were conducted using various remote sensing techniques, including optical photogrammetry via Unmanned Aerial Vehicle (UAVs), LiDAR surveys using UAV-mounted laser scanners, imagery captured with a MicaSense RedEdge-P multispectral camera equipped on a UAV, and portable laser scanner with Simultaneous Localization and Mapping (SLAM) technology (FJD TRION P1 model). Optical photogrammetry and LiDAR, both conducted via drones, enabled us to produce high-resolution 3D point clouds, orthophotos (<2 cm/pixel), and Digital Terrain Models (DTM, <5 cm/pixel). Through repeated surveys over two years, a multitemporal change detection analysis was conducted, revealing significant changes in response to storm events and providing rates of cliff retreat up to 1 m in localized sectors. SLAM technology allows to examine outcrop portion, less visible from UAV surveys, as the bottom of the rocky cliff. Here, the impact of storm waves was monitored, and the specific SLAM results were useful for unravelling the role of extreme event on the cliff retreating and associated rock-fall triggering along the cliff wall. The use of the multispectral sensor, particularly through the Green and Blue bands, provides useful data for better understanding the morphodynamics along the submerged portion of the shore platform. In particular, the submerged platform exhibits the same rock fracturing patterns observed in the emerged section and is composed of blocks that detach and partially slide into the sea, contributing to the retreating trend of the cliff and shore platform system.

The integration of multi-techniques not only enabled the quantification of the retreat rates of the cliff under analysis, but also allowed their correlation with predisposing and triggering factors, providing the foundation for the comprehension of potential future evolution in a changing climate context.

How to cite: Piacentini, D., Torre, D., Iacobucci, G., and Troiani, F.: Multi-technique approach for the reconstruction of rocky coast evolution, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17297, https://doi.org/10.5194/egusphere-egu25-17297, 2025.

Increasing pressure on the coastal zone, driven by urbanization and related adoption of hard engineering protection structures, has frequently contributed to a gradual amplification of beach erosion. This is the case of Vale do Lobo beach (Algarve, Portugal), where sand retention caused by the Quarteira groin field and Vilamoura jetties led to soft cliff recession and reduction of the beach width downdrift (Teixeira, 2019). To mitigate these effects, an artificial beach nourishment program along with a monitoring plan have been implemented by the predecessor institution of the Portuguese Environment Agency since 1997 (Pinto & Teixeira, 2022), which involves systematic surveys of six beach profiles and has limited spatial scope and temporal resolution. These limitations could be overcome by satellite remote sensing (RS), which has been recognized as an alternative.

We aim to verify whether RS is suitable for measuring changes of beach width after beach nourishment operations, contributing to cost-effective monitoring with greater spatial and temporal coverage. The study was conducted along the Vale do Lobo coastline, focusing on the evolution of the average beach width from February 2000 to February 2024. During this period, the beach evolution was marked by a rapid increase in beach width following two beach nourishments and a gradual narrowing driven by a sediment deficit imposed by the updrift retention structures.

Images from the Landsat 5, 7, 8 and 9 satellites and Sentinel-2 Level 1C were obtained and classified, using the python toolkit CoastSat (Vos et al., 2019), which also made it possible to obtain the shorelines of the beach during the study period. The USGS DSAS (Himmelstoss et al., 2024) software was used to acquire beach width values, at the six profiles surveyed in the monitoring program. Although the relatively low spatial resolution of the images (30m and 10m), and the existing differences between the measured shoreline indicators (beach width at MSL and instantaneous water line in RS, which includes the effects of tide and swash signals), the relatively high temporal resolution of RS images allowed for the filtering of uncertainties. As a result, the time-averaged RS values were found to closely match those obtained from field monitoring. In response to the 2006 nourishment, the beach advanced 29m (33m for RS) followed by a gradual beach width reduction of 5.8m/yr (5.7m/yr for RS), while in the 2010 nourishment the beach advanced 29m (28m for RS) followed by a gradual reduction of 1.8m/yr (1.9m/yr for RS). The comparison between the data obtained showed congruence of field and RS results, proving evidence that remote sensing techniques and semi-automatic methods can be an asset for monitoring beach nourishment evolution. This work is supported by the Portuguese Fundação para a Ciência e Tecnologia, FCT, I.P./MCTES through national funds (PIDDAC): UID/50019/2025, UIDB/50019/2020 (https://doi.org/10.54499/UIDB/50019/2020) and LA/P/0068/2020 (https://doi.org/10.54499/LA/P/0068/2020). The work is a contribution to the CREST project, funded by FCT through Grant 2022.05392.PTDC (doi:10.54499/2022.05392.PTDC). Authors also recognize the support of national funds through FCT, under the project LA/P/0069/2020 (doi:10.54499/LA/P/0069/2020), granted to the Associate Laboratory ARNET, and UID/00350/2020 (doi:10.54499/UIDB/00350/2020) granted to CIMA.

How to cite: Neves Silva, M., Vaz, A., Taborda, R., Nobre Silva, A., Pinto, C. A., Santos, J., Teixeira, S., and Costas, S.: Monitoring beach nourishment evolution using satellite data: the case of Vale do Lobo (Portugal) , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17669, https://doi.org/10.5194/egusphere-egu25-17669, 2025.

Understanding the spatial and temporal variation of the shoreline position is key to both research and engineering projects contributing to an efficient management of the coast. Accelerated climate change and its related impacts can further destabilize coastal systems, highlighting the need for studies that quantify coastal evolution,  while discussing the application of satellite remote sensing datasets and GIS methods for coastline extraction, mapping, and analysis along regional coasts.

The Gulf of Cadiz is brimming with human intervention and as such has been the target of many studies. The focus of this work covers part of this region, extending from Olhos de Água (Portugal) to the mouth of the Guadalquivir River (Spain) (~180 km). The study area is characterized by a variety of coastal morphological features, including cliffs, beaches, foredunes and inlets. Regardless of its great diversity of landforms, sandy beaches still constitute the dominant coastal environment of this region. We aim to grasp a better understanding of the Cadiz Gulf coastal dynamics through the comparing two shoreline mapping methods and indicators, covering the time span between 2014-2024 for Portugal and 2016-2022 for the Spain coast.  The applied methods include 1) the manual digitation of Wet/Dry Line (WDL) and the Instantaneous Water Line (IWL) indicators within a GIS environment, and 2) the automatized extraction of the IWL using the CoastSat toolkit (Vos et al., 2019). The WDL Marks the darkest edge of the wet area of the beach, while the IWL is the line where the water meets the sand. The manually digitized shoreline was carried out in ArcGIS Pro 3.4.0 over the orthophotomaps obtained from “Direção Geral do Território” (Portugal) and “Instituto Geografico Nacional” (Spain) websites. CoastSat python toolkit (Vos et al., 2019) was used to extract shorelines from open-source satellite imagery (Landsat and Sentinel-2).

Overall, the Gulf of Cadiz has shown average end point rates (EPR) of 1.65 m/yr and 0.6 m/yr for the manually mapped WDL and IWL, respectively. The automated approach yielded a rate of 1.84 m/yr. All the methods show net shoreline accretion, with the results heavily influenced by the significant accretion observed in the downdrift  sector, Matalascañas to Guadalquívir. When all the sectors are analyzed individually it is possible better compare the methodologies, according to all indicators. Comparisons reveal that, in most cases, the automated shorelines align more closely with the manually identified WDL rather than the expected IWL. This discrepancy raises questions about the nature of the indicator detected by the automated tool. The findings suggest that the automated extraction may primarily capture the WDL, highlighting the need for further investigation into the physical significance of indicators identified by automated methods.

This work is supported by the Portuguese Fundação para a Ciência e Tecnologia, FCT, I.P./MCTES through national funds (PIDDAC): UID/50019/2025, UIDB/50019/2020 (https://doi.org/10.54499/UIDB/50019/2020) and LA/P/0068/2020 (https://doi.org/10.54499/LA/P/0068/2020). The work is a contribution to the CREST project, funded by FCT through Grant 2022.05392.PTDC (doi:10.54499/2022.05392.PTDC). Authors also recognize the support of national funds through FCT, under the project LA/P/0069/2020 (doi:10.54499/LA/P/0069/2020), granted to the Associate Laboratory ARNET, and UID/00350/2020 (doi:10.54499/UIDB/00350/2020) granted to CIMA.

How to cite: Vaz, A., Neves Silva, M., Valverde, F., Taborda, R., Nobre Silva, A., Santos, J., and Costas, S.: Shoreline evolution of the Gulf of Cadiz through manually digitized and automated extraction methods, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17681, https://doi.org/10.5194/egusphere-egu25-17681, 2025.

The Adriatic Sea, located in the northeastern Mediterranean basin, is well representative of processes and pressures that typically affect mid-latitude coastal seas.

The Adriatic Ensemble (AdriE), a multi-decadal, kilometre-scale ocean model, has recently been developed to describe ocean processes in the Adriatic Sea under a severe (RCP8.5) climate scenario extending to the end of this century. Addressing 3-D circulation and thermohaline dynamics within the Regional Ocean Modelling System (ROMS), AdriE consists of 6 climatic runs encompassing the period from 1987 to 2100 in a RCP8.5 scenario forced by the SMHI-RCA4 Regional Climate Model, driven by as many different General Climate Models made available within the EURO-CORDEX Initiative. In the present contribution we complement eulerian and lagrangian analysis techniques to investigate how climate change will affect the main hydrodynamic processes in this basin, with particular reference to key features for this area such as dense water production, pollutant transport, and ecological connectivity.

This work lays the foundation for a deeper interdisciplinary assessment of future scenarios in the region and the development of potential management strategies.

How to cite: Bonaldo, D., Bongiorni, L., Carniel, S., Colucci, R., Denamiel, C., Ghezzo, M., Pesce, A., Pranić, P., Raicich, F., Ricchi, A., Sangelantoni, L., Vilibić, I., and Vitelletti, M. L.: Circulation patterns in the Adriatic Sea under a severe climate change scenario: projections from the AdriE ensemble., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19510, https://doi.org/10.5194/egusphere-egu25-19510, 2025.

The N2 fixation and primary production rates were measured simultaneously using 15N2 and 13C incubation assays in the northern South China Sea influenced by the Kuroshio intrusion (KI) seasonally. The degree of KI (KI index, range from 0 to 1) was assessed by applying an isopycnal mixing model. The water column integrated N2 fixation and primary production for stations with KI index larger than 0.5 were 463 ± 260 μmol N·m−2·day−1 and 62 ± 19 mmol C·m−2·day−1, respectively, significantly higher than those for stations with KI index lower than 0.5 (50 ± 10 μmol N·m−2·day−1 and 28 ± 10 mmol C·m−2·day−1, respectively). Trichodesmium was the dominant diazotroph at stations with KI index larger than 0.5, with 2 orders of magnitude higher nifH gene abundance than that at stations with KI index lower than 0.5. However, the highest N2 fixation rates were found in waters with moderate KI index around 0.6, suggesting that frontal zone mixing might stimulate N2 fixation. Our results demonstrated that diazotrophs (mainly Trichodesmium) were tightly associated with the KI, which modulated the biogeographic distribution of N2 fixers. In summary, we found the transportation of Trichodesmium by KI, then, we quantified the fraction of KI and N2 fixation rates in the northern South China Sea. The results suggested that KI generated a new biogeographic regime which could significantly influence the carbon and nitrogen cycles far away from the main stream.

How to cite: Lu, Y.: Biogeography of N2 Fixation Influenced by the Kuroshio Intrusion in the South China Sea, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20220, https://doi.org/10.5194/egusphere-egu25-20220, 2025.