High-resolution Hydrodynamic Model Research Articles

Nonthermal Signatures of Radiative Supernova Remnants

The end of supernova remnant (SNR) evolution is characterized by a so-called “radiative” stage, in which efficient cooling of the hot bubble inside the forward shock slows expansion, leading to eventual shock breakup. Understanding SNR evolution at this stage is vital for predicting feedback in galaxies, since SNRs are expected to deposit their energy and momentum into the interstellar medium at the ends of their lives. A key prediction of SNR evolutionary models is the formation at the onset of the radiative stage of a cold, dense shell behind the forward shock. However, searches for these shells via their neutral hydrogen emission have had limited success. We instead introduce an independent observational signal of shell formation arising from the interaction between nonthermal particles accelerated by the SNR forward shock (cosmic rays) and the dense shell. Using a semi-analytic model of particle acceleration based on state-of-the-art simulations coupled with a high-resolution hydrodynamic model of SNR evolution, we predict the nonthermal emission that arises from this interaction. We demonstrate that the onset of the radiative stage leads to nonthermal signatures from radio to gamma rays, including radio and gamma-ray brightening by nearly 2 orders of magnitude. Such a signature may be detectable with current instruments, and will be resolvable with the next generation of gamma-ray telescopes (namely, the Cherenkov Telescope Array).

Assessing Tidal Models in the Ryukyu Islands Region Using the ENOPF Method

Abstract Satellite remote sensing can monitor sea level changes at temporal and spatial scales, plays an important role in the study of tides, and is widely used in numerical tidal models. However, these tidal models are usually computationally expensive. The equidistant nodes orthogonal polynomial fitting (ENOPF) method may overcome that drawback. This study evaluates the accuracy of the ENOPF method in fitting the major tidal constituents in the region near the Ryukyu Islands, where the water depth on either side of the islands varies significantly. The results show that the ENOPF method can accurately fit the major tidal constituents in the presence of complex topography. Furthermore, this approach can also be used to generate reasonable cotidal charts and provide valuable tidal information for hydrodynamic model simulations in the East China Sea. For the high-resolution hydrodynamic model of the East China Sea in particular, reasonable open boundary conditions can be provided by the ENOPF method.

Effects of low salinity water inflow on eelgrass and cultured bivalves in subarctic lagoons: Analysis using hydrodynamic model

Brackish water areas are affected by river inflows and changes in tidal level, resulting in large fluctuations in salinity. Prolonged exposure to low salinity water can have adverse effects on the growth of marine plants and animals. Characteristics of lagoons such as catchment area, bottom topography, and seawater exchange rate with the open ocean vary widely and the horizontal and vertical gradients of salinity and spatio-temporal variability are also diverse. In this study, we evaluated the impact of low salinity water inflows due to heavy rainfall on seagrass and cultured bivalves in two lagoons (Akkeshi-ko Lagoon and Notoro-ko Lagoon), which are located in the subarctic region of Japan and have contrasting geomorphological characteristics. Continuous observations of the physical environment were conducted by installing measurement equipment near the seafloor, and we ran ten year replicate calculations using a three-dimensional high-resolution hydrodynamic model. Simulation results were used to assess the risk of low salinity associated with heavy rainfall to eelgrass and bivalves (oyster, scallop, and clam). The model analysis showed that the magnitude and frequency of exposure to low salinity water varied greatly between and within lagoons. Akkeshi-ko Lagoon, which has a relatively large catchment area and shallow basin, was sometimes exposed to extremely low salinities, which could lead to the mortality of oysters during heavy rains once every few years. In contrast, salinity decline in Notoro-ko Lagoon is negligible even in years with heavy rainfall due to the high volume of water within the lagoon and small catchment area. With projections that the intensity of heavy rainfall will increase due to climate change, this study was able to evaluate the impact of changes in river flow on coastal ecosystems and aquaculture, and we discussed adaptation measures that may be necessary in the future.

Spatio-temporal connectivity and dispersal seasonal patterns in the Adriatic Sea using a retention clock approach

Hydrodynamic features play a key role in determining the dispersal and connectivity of fish populations, especially in highly energetic areas determined by currents, river flow, and meteorologically induced fluctuations. Understanding how species interact with these physical processes is essential for managing vulnerable populations and identifying areas that require effective conservation efforts. This study examines the hydrodynamics that regulate connectivity in the Adriatic Sea, a shallow and semi-enclosed basin that is widely recognized as one of the most important areas in the Mediterranean Sea for protection. A high-resolution hydrodynamic model coupled with a lagrangian tracking module serves as the numerical tool. Lagrangian particles, representing eggs and larvae with typical biological characteristics of generic marine organisms inhabiting the region, are released throughout the basin at different times during a test year to identify the most likely pathways of individual dispersal. The temporal component of connectivity is highlighted using a previously developed retention clock matrix over different larval durations. Seasonality is a critical factor in dispersal, with greater variability and reduced efficiency in winter compared to summer. The potential implications of the results for improved assessment and management of high value marine species in the basin are discussed.

Sea level and temperature extremes in a regulated Lagoon of Venice

Increasing sea levels and water temperatures have been detected at several coastal locations worldwide with severe consequences on the communities and ecosystems. Coastal lagoons are particularly vulnerable to such changes due to their low land elevation and limited connections with the open sea. Here the recent and future climatic changes in the Lagoon of Venice (Italy) are investigated using in-situ observations and high-resolution hydrodynamic modeling. Trend analysis was applied to observed time series of meteorological and oceanographic climate essential variables to identify significant long-term changes in mean and extreme values. The mean relative sea level rose at a rate of 4.9 mm per year in Venice due to the combined action of eustacy and subsidence while air and sea temperatures increased on average by 1.8 and 1.1°C in 30 years, respectively. These rates, as well as climate projections, were used following a pseudo-global-warming approach to investigate the near future (up to 2050) evolution of the lagoon's dynamics focusing on sea level and temperature extremes. The lagoon will amplify the temperature changes expected for the Adriatic Sea, especially in the shallow tidal flats where the intensity of the marine heat waves will be more than four times larger than that in the open sea. Moreover, the model allowed us to perform “what-if” scenarios to explore to which extent the flood protection MoSE barriers will modify the lagoon's dynamics. According to the simulations, the number of floods and therefore of the MoSE closure strongly increases with sea level rise. In the most severe scenario, MoSE will have to close for more than 20% of the time in October, November, and December resulting in the reduction of water exchange with the open sea and exacerbation of marine cold spells. Some considerations on the implications of the expected changes on the lagoon's ecology are proposed.

Tidal current energy resources assessment in Zhoushan Archipelago, China

ABSTRACT Zhoushan Archipelago, the largest archipelago in China, harbors a significant tidal stream resource due to robust tidal currents coursing through numerous channels between its islands. Nevertheless, the tidal energy resource in the Zhoushan Archipelago has not been systematically characterized considering both topography and energy flow density. This study presents a modeling study aimed at characterizing the tidal energy resource in the whole Zhejiang coast, including Zhoushan Archipelago, employing a high-resolution tidal hydrodynamic model, i.e. MIKE 21. Through a comparison of the model output with observed data from two tidal stations and three current stations, the accuracy of the numerical model was confirmed. The study identified areas with robust currents and suitable water depths, both essential factors for the advancement of tidal current energy. The findings showed that many channels in Zhoushan Archipelago and Wenzhou Bay in Zhejiang experience the highest tidal power density, reaching nearly 5500 W/m2. Furthermore, the study estimated the theoretical tidal current energy production for the whole area, highlighting Loutou channel, Cezi channel, Taohuagang, and the channel between Xiushan island and Daishan island as regions with high potential.

Variability in estuarine habitat use of a threatened species in the northern Gulf of Mexico: implications for coastal restoration

Coastal restoration projects often require sediment resources borrowed from estuarine or marine ecosystems. A generalized additive modeling (GAM) framework was used to characterize fish-habitat relationships and predict spatiotemporal and ontogenetic shifts of Gulf sturgeon distribution within an impacted estuary in the northern Gulf of Mexico, Lake Pontchartrain. Habitat use and movement of Gulf sturgeon (n = 103) was monitored using an array of acoustic receivers (n = 81) from 2016 to 2019. Telemetry data was paired with environmental conditions hindcast from a high-resolution hydrodynamic model to develop GAMs for three life stages of Gulf sturgeon: juvenile, sub-adult, and adult. Model results demonstrated clear spatial, temporal, and ontogenetic shifts in habitat use for Gulf sturgeon in the Lake Pontchartrain estuary. The importance of spatial and temporal variables in the final models of all life stages suggests that distribution of Gulf sturgeon within the estuary is more likely driven by biology (prey distribution) rather than environment. Interestingly, dependence of Gulf sturgeon on the estuary for overwintering habitat declined with ontogeny. The northeastern shoreline of Lake Pontchartrain was identified as potential nursery habitat for overwintering juvenile sturgeon from the Pearl River, while eastern portions of the estuary and associated channels provide critical staging habitat and corridors of connectivity for migrating sub-adult and adult sturgeon. Given the clear need to prioritize conservation of Gulf sturgeon while restoring coastal marshes, findings from this study provide needed information to shape future coastal restoration and inform the siting and timing of future dredging operations in Lake Pontchartrain.

Lagoon hydrodynamics of pearl farming atolls: the case of Raroia, Takapoto, Apataki and Takaroa (French Polynesia)

Abstract. Between 2018 and 2022, four pearl farming Tuamotu atolls of French Polynesia were monitored with autonomous oceanographic instruments to measure the hydrodynamics of atoll lagoons and the ocean–lagoon water exchanges. These surveys were conducted within the framework of the ANR-funded MANA (Management of Atolls) project and its extensions to additional sites. The overarching goal was to improve knowledge on the processes influencing the spat collection of the pearl oyster Pinctada margaritifera, the oyster species used to produce black pearls. These data sets are also critical for the calibration and validation of 3D high spatial resolution hydrodynamic models used to study oyster larval dispersal within lagoons. The observational strategies focused on the characterization of ocean–lagoon exchanges through passes and hoa (i.e., shallow reef flats), lagoon circulation, incident waves breaking on the forereef, water elevation inside the lagoon as well as spatial temperature variability. Chronologically, the investigated atolls were first Raroia Atoll with 9 months of measurements between May 2018 and March 2019 during which the MALIS1 and MALIS2 cruises on-board the R/V ALIS took place. It was followed by a 4 month deployment in Takapoto Atoll (November 2021 to March 2022). In late April 2022, Apataki Atoll was instrumented until end of July, followed by Takaroa measurements between July and October 2022. Apataki (Leg2) and Takaroa Atoll were conjointly instrumented during the MALIS 3 oceanographic cruise. Altogether, those multi-atoll data bring a worldwide unique oceanographic atoll data set that is useful for addressing local pearl farming questions but potentially beneficial for other fundamental and applied investigations. Each data set was post-processed, quality controlled and converted into NetCDF format. Files are available in open source into dedicated repositories in the SEANOE marine data platform. Links (DOI) of individual data sets are provided in Table 2.

Testing passive dispersal as the key mechanism for lionfish invasion in the Mediterranean Sea using Lagrangian particle tracking

The expansion of lionfish Pterois miles across the Mediterranean Sea since its introduction via the Suez Canal has been rapid, but the mechanisms by which the expansion occurred have not been fully tested. By using a series of Lagrangian particle tracking simulations and high-resolution hydrodynamic models, we tested the hypothesis that passive dispersal of larvae could explain the east to west expansion of lionfish. By sequentially modelling the annual dispersal of larvae, from the first observation in Lebanon in 2012 and then modelling dispersal of larval from the simulated settlement sites, we showed that passive dispersal driven by ocean currents largely explained the observed expansion of lionfish until 2020. The spread of lionfish was likely restricted by environmental conditions when the population reached the central Mediterranean and the particle tracking simulations diverged from observations. The results emphasize the potential contribution of computational models in understanding the dispersal of non-indigenous and range expanding species in response to changing environmental conditions, identifying high risk areas, and guiding targeted surveillance, early detection, and informing management strategies for such species. Given that many non-indigenous species in the Mediterranean are introduced through a consistent pathway (the Suez Canal), the incorporation of interdisciplinary approaches and high-resolution biophysical models can provide fundamental knowledge for management action prioritization.

Comprehensive characterization of Marine Heatwaves in a coastal Northern Humboldt Current System regional model over recent decades

In this study, a high-resolution hydrodynamic model simulation was used to analyze the three-dimensional characteristics of marine heatwaves (MHWs) in the coastal region of the Northern Humboldt Current System (NHCS) over the period 2000–2019. Three distinct vertical layers were identified. The near-surface layer, extending down to 75 m depth, is identified as the region where both the maximum MHW intensity and cumulative intensity are found, predominantly concentrated along the thermocline depth. The intermediate layer, spanning from 75 to 125 m depth, exhibited the longest MHW durations and the lowest MHW frequencies. MHWs in this layer tend to be of moderate intensity and are often associated with ENSO variability. In contrast, the deep layer, from 125 to 250 m depth, was characterized by short-lived MHWs of low intensity. These MHWs exert a lesser thermal impact on the region. To understand the drivers of MHWs, a composite analysis was performed. The results highlighted the significant role exerted by wind-driven anomalies in the life cycle of MHWs. It was found that the combined effect of a sluggish coastal upwelling circulation and suppressed oceanic heat loss, as a result of weakened winds, preceded the MHW formation. Conversely, the strengthening of winds, which enhanced net heat loss, primarily driven by latent heat flux anomalies, and an enhancement of the cooling effect due to the recovery of the coastal upwelling circulation, are key processes in ending a typical MHW event in the coastal region. These findings expand our understanding of the MHWs and their associated potential drivers and help to reveal which regions are most susceptible to extreme climate events in one of the most productive marine ecosystems worldwide.

Hydrography of Northern Thermaikos Gulf based on an integrated observational-modeling approach

The Northern Thermaikos Gulf is a semi-enclosed coastal region of the Aegean Sea, characterized by anthropogenic and natural stresses such as intense industrial and agricultural activities, urban outflows, and several river discharges facing severe pollution events. The main motivation of this study is to investigate the prevailing oceanographic conditions of Northern Thermaikos Gulf, which are associated with the quality of the semi-enclosed basin's water masses. The hydrography and the hydrodynamic circulation patterns are revisited, based on the findings of a multi-platform observational study, conducted during a recent annual cycle, from June 2021 until May 2022. The observational findings are supported by a three-dimensional high-resolution hydrodynamic model (Deltf3D-Thermaikos) with updated freshwater input from all important land sources. The physical connectivity between the sub-basins of Thermaikos, the renewal of its northern coastal areas and the seawater quality are strongly related to the variability of wind-induced circulation. Northerly and southerly winds affect the spreading of the nutrient-rich riverine waters, discharged at the west coast of the gulf. The prevailing northerly winds contribute to the southward removal of the polluted sea surface and riverine waters, enhancing the cyclonic circulation around the gulf, allowing the inflow of clearer Aegean Sea Waters along the eastern coasts of the gulf. Northerlies also promote a connectivity pathway between the environmentally stressed Thessaloniki Bay (urban seafront) and the commonly less polluted southeastern coasts of the central basin. Southerlies mainly confine riverine waters in the western and northern coastal regions, weaken the renewal ability of the enclosed basins, and impose the formation of anticyclonic, mesoscale, circulation eddies in the outer and central areas.

Connectivity-based approach to guide conservation and restoration of seagrass Posidonia oceanica in the NW Mediterranean

Marine population connectivity involves organism movement and interactions in oceanic and coastal settings. It is essential for biodiversity by aiding genetic diversity, species distribution, and recovery from disturbances. It guides resource management strategies like fisheries and conservation planning, ensuring marine ecosystem sustainability. Seagrass meadows play a pivotal role within coastal ecosystems, contributing to essential ecological, physical, and economic functions. Despite the presence of protective policies, a continuous decline of seagrass meadows has been observed in recent years due to the impact of human activities and climate change. In the Balearic Islands of the Mediterranean Sea, these pressures are further intensified by tourism, underlining the pressing requirement to prioritize areas for protection and restoration while considering the connectivity between habitat patches. In this study, the dispersal of Posidonia oceanica, the most widespread seagrass species in the Mediterranean Sea, from semi-enclosed bays and nearshore locations within the Balearic Islands archipelago, is investigated using a high-resolution hydrodynamic model and an individual-based model. The simulations were subjected to analysis through a graph-theoretic approach, revealing significant variations in dispersal probabilities across different years. Notably, Alcudia Bay emerged as a prominent sink, while critical links were identified between Menorca and Mallorca, as well as between Mallorca and Ibiza. This study underscores the value of dispersal modelling and network analysis in conservation planning for foundational species, particularly within a regional, integrated framework of conservation management.

Tracking the source of wild mussel spat for aquaculture using shell microchemistry and biophysical models

The spatial and temporal uncertainty in availability and distribution of wild mussel seed is a major obstacle to sustainable production in mussel aquaculture globally. An improved understanding of patterns of dispersal of wild mussel spat could help to resolve this uncertainty to progress the management of wild spat resources and increase mussel seed supply. In this study, the natal locations and patterns of dispersal for recently settled green-lipped mussels, Perna canaliculus, at an offshore mussel farm in northern New Zealand were estimated using a combination of analysis of shell microchemistry of arriving spat and biophysical modelling. The shell microchemistry from mussel spat settling on the offshore mussel farm were compared with those from mussels cultured in situ at 22 surrounding sites (∼2–6 km apart) arranged around the Bay of Plenty, New Zealand, over two consecutive months. Six elemental signatures (Li, Co, Ni, Ba, La and U) were the primary drivers for correctly reassigning shells back to their individually generated sites with an overall 57.4% of Leave-one-out cross-validated (LOOCV) cases correctly assigned, ranging from a low of 10% for one coastal site (near Hikuwai Beach) and up to 78% for an offshore mussel spat collection site (near mussel farm). The microchemistry signatures were subsequently employed to backtrack ∼160 spat arriving on the mussel farm to two main natal sites (i.e., 7.5 and 8.0 km away) near Ōhiwa Harbour and known to have wild mussel reefs, which accounted for 85% of the mussels arriving on the mussel farm. Forward and backward simulations of movements of mussel spat using high resolution (i.e., 1 km) hydrodynamic particle tracking models indicated that most spat arriving on the mussel farm during the sampling period originated from the same stretch of coast identified by the shell microchemistry. The concordance of results from the two methods of determining natal sources provide mutual validation of the results and highlight the importance of managing coastal populations of wild mussels that are under increasing pressure from human activities, especially where they provide a critical seed source for aquaculture.

Integration of empirical and modelled data unravels spatiotemporal distribution and connectivity patterns of Fuegian sprat early life stages

The distribution patterns of fish early life stages are critical to recruitment success and closely related to major oceanographic circulation patterns. We explored the spatiotemporal distribution of early life stages of Fuegian sprat Sprattus fuegensis, a key trophic species in the Southwestern Atlantic Ocean (SWAO), in a complex oceanographic setting. Samples were collected during austral spring, summer, and autumn, from 2014 to 2017, across areas with distinct biophysical properties between Tierra del Fuego (TDF) and the marine protected area ‘Namuncurá’ at Burdwood Bank (BB) (ca. 54°S). Results revealed significant seasonal fluctuations in abundance, distribution, and ontogenetic composition across habitats. High egg and early larval abundances at Isla de los Estados (IE) suggest it is an additional spawning ground to those previously identified at TDF and BB. However, only the latter appear to be suitable nursery areas. Particle-tracking simulations based on egg abundance and spawning dates were conducted for the first time using results from a high-resolution hydrodynamic model. Particle transport provides evidence of connectivity between IE and neighbouring areas—enhanced when horizontal diffusivity is incorporated into the model—but not between TDF and BB. Simulated distributions closely resembled empirical patterns from this and other studies, allowing the integration of empirical and modelled data to schematize the species’ dispersal pathways in the study area. These results offer new insights into distribution and connectivity patterns among spawning grounds and highlight the potential use of hydrodynamic models for future assessments of Fuegian sprat and other planktonic species’ dispersal and recruitment in the SWAO.

Modeling the Impact of Hydraulic Reconnection on Estuary Hydrodynamics

Highlight: Evaluation of a high-resolution 2D hydrodynamic model showed that restoring flow connections in a developed subtropical estuary would increase the tidal range and reduce the average surface water elevations in the surrounding canals.

Modes of Operation and Forcing in Oil Spill Modeling: State-of-Art, Deficiencies and Challenges

Oil spills may have devastating effects on marine ecosystems, public health, the economy, and coastal communities. As a consequence, scientific literature contains various up-to-date, advanced oil spill predictive models, capable of simulating the trajectory and evolution of an oil slick generated by the accidental release from ships, hydrocarbon production, or other activities. To predict in near real time oil spill transport and fate with increased reliability, these models are usually coupled operationally to synoptic meteorological, hydrodynamic, and wave models. The present study reviews the available different met-ocean forcings that have been used in oil-spill modeling, simulating hypothetical or real oil spill scenarios, worldwide. Seven state-of-the-art oil-spill models are critically examined in terms of the met-ocean data used as forcing inputs in the simulation of twenty-three case studies. The results illustrate that most oil spill models are coupled to different resolution, forecasting meteorological and hydrodynamic models, posing, however, limited consideration in the forecasted wave field (expressed as the significant wave height, the wave period, and the Stokes drift) that may affect oil transport, especially at the coastal areas. Moreover, the majority of oil spill models lack any linkage to the background biogeochemical conditions; hence, limited consideration is given to processes such as oil biodegradation, photo-oxidation, and sedimentation. Future advancements in oil-spill modeling should be directed towards the full operational coupling with high-resolution atmospheric, hydrodynamic, wave, and biogeochemical models, improving our understanding of the relative impact of each physical and oil weathering process.

High-resolution hydrodynamics of coral reefs and tracing of pollutants from hotel areas along the west coast of Unguja Island, Zanzibar

A rapid increase in population size along with expansion in hotel investment have been identified as key drivers of marine pollution in Zanzibar coastal waters. A validated high-resolution hydrodynamic tracer model was used to estimate the dispersal and impact range of pollutants from the main hotel areas along the western coastline of Unguja Island. The model showed the highest impact of pollutants from land during the northeast monsoon season due to the weakening of the main current. Marine protected areas with short distances to hotel areas and weak tidal currents were more likely to be impacted by pollutants from land than the more remote areas with higher flushing in agreement with water quality and seagrass health measurements. Cumulative effects of pollutants instead of single sources are important to consider for integrated wastewater treatment plans and management strategies to reduce pollution for the protection of biodiversity and guide future monitoring.

Combined statistical and hydrodynamic modelling of compound flooding in coastal areas - Methodology and application

This paper presents a robust cost-effective framework for assessment of coastal-fluvial flooding due to compound action of multivariate dependent drivers. The methodology is an 8-step process that links statistical and hydrodynamic models to determine probabilities of multiple-driver flood events and associated hazards. The method involves individual and combined extreme value analysis, assessment of dependencies and interactions between flood drivers, multivariate joint probability determination accounting for dependencies, high-resolution hydrodynamic modelling of flood scenarios derived from multivariate statistical analysis, and ultimately mapping of inundation.Using Cork City, on the south coast of Ireland, as a study case, the research shows that the interactions and dependencies between tides, surges and river flows affect flood severity when they occur jointly. Tide-surge interactions have a damping effect on the total water level, while dependence between the surge residual and river flow amplifies the risk of flooding. The multivariate joint exceedance probability occurrence of high discharges and water levels represents a more realistic representation of the spatially variable water surface profiles then the combined univariate marginal scenarios. Multivariate analysis allows also considering multiple combinations of joint probability solutions along RP iso-curves. The results show that the quantification of compound flood impacts must be performed along the entire RP probability curve. This is because the physical/hydrological impacts of multiple-driver same-RP flood events can be very different leading to substantially different characteristics of flooding. The multi-scale nested flood model (MSN_Flood) was used to simulate flood wave propagation over urban floodplains for an ensemble of statistically derived flood scenarios. The hydrodynamic runs provide inundation maps that can be used to draw inferences about flood mechanisms and impacts.

Atmospheric–ocean coupling drives prevailing and synchronic dispersal patterns of marine species with long pelagic durations

Dispersal shapes population connectivity and plays a critical role in marine metacommunities. Prominent species for coastal socioecological systems, such as jellyfish and spiny lobsters, feature long pelagic dispersal phases (LPDPs), which have long been overlooked. Here, we use a cross-scale approach combining field surveys of these species with a high-resolution hydrodynamic model to decipher the underlying mechanisms of LPDP patterns in northwestern Mediterranean shores. We identified basin-scale prevailing dispersal routes and synchronic year-to-year patterns tightly linked to prominent circulation features typical of marginal seas and semienclosed basins, with an outstanding role of a retentive source area replenishing shores and potentially acting as a pelagic nursery area. We show how the atmospheric forcing of the ocean, a marked hydrological driver of the Mediterranean Sea, modulates dispersal routes and sources of LPDP at interannual scales. These findings represent a crucial advance in our understanding of the functioning of metapopulations of species with LPDP in marginal seas and may contribute to the effective management of coastal ecosystem services in the face of climate change.

Seasonal to interannual variability of the tide in the Amazon estuary

The Amazon River exports the largest volume of fresh water to the ocean worldwide. Although previous studies have revealed the spatiotemporal tidal variability of the estuary, its hydrodynamics is still poorly understood. Here we evaluate the seasonal and interannual variability of the tide from Óbidos (800 km upstream) to the Atlantic Ocean and show how it is affected by the hydrological regime of the Amazon River. A high-resolution 2D hydrodynamic model was applied in this region at the scale of the whole estuary. The tide model is validated using data from 14 water level stations and shows an average complex error of 16 cm in the low flow season and 23 cm in the high flow season. The semi-diurnal tide is highly variable at seasonal timescales, and the seasonality of the discharge affects the tidal amplitude, the geographic extent of tidal influence, the tidal wave celerity, and the tidal flow reversal. Notably, the tidal influence on water level remains detectable up to Óbidos during the low flow season while during the high flow season it extends from the ocean to only 300 km downstream of Óbidos. On the other hand, the upstream limit of the domain where the tide induces a periodic flow reversal is different from the limit of tidal influence on the water level. The upstream limit of this flow reversal is shifted by 170 km (from 500 km to 670 km downstream of Óbidos) along the year due to the seasonality of the discharge. At interannual scale, anomalous hydrological discharges affect the tidal amplitude by up to 30% in the central reach of the estuary. Our findings open unprecedented opportunities to understand biogeochemical and geomorphological processes, help navigation, and assess flooding hazards.