Nearshore Circulation

This contribution presents the results of a study on the shoreline variability of a natural perched urban beach (Ammoudara, N. Crete, Greece). Shoreline variability was monitored in high spatio-temporal resolution using time series of coastal video images and a novel, fully automated 2-D shoreline detection algorithm. Ten-month video monitoring showed that cross-shore shoreline change was, in some areas, up to 8 m with adjacent sections of the shoreline showing contrasting patterns of beach loss or gain. Variability increased in spring/early summer and stabilized until the end of the summer when partial beach recovery commenced. Correlation of the patterns of beach change with wave forcing (as recorded at an offshore wave buoy) is not straightforward; the only discernible association was that particularly energetic waves from the northern sector can trigger changes in the patterns of shoreline variability and that increased variability might be sustained by increases in offshore wave steepness. It was also found that the fronting beachrock reef exerts significant geological control on beach hydrodynamics. Hydrodynamic modelling and observations during an energetic event showed that the reef can filter wave energy in a highly differential manner, depending on its local architecture. In some areas, the reef allows only low-energy waves to impinge on the shoreline, whereas elsewhere penetration of higher waves is facilitated by the low elevation and limited width of the reef or by the presence of an inlet. Wave/reef interaction can also generate complex circulation patterns, including rip currents that appeared to be also constrained by the reef architecture.

This contribution presents the results of a study on the shoreline variability of a natural perched urban beach (Ammoudara, N. Crete, Greece). Shoreline variability was monitored in high spatio-temporal resolution using time series of coastal video images and a novel, fully automated 2-D shoreline detection algorithm. Ten-month video monitoring showed that cross-shore shoreline change was, in some areas, up to 8 m with adjacent sections of the shoreline showing contrasting patterns of beach loss or gain. Variability increased in spring/early summer and stabilized until the end of the summer when partial beach recovery commenced. Correlation of the patterns of beach change with wave forcing (as recorded at an offshore wave buoy) is not straightforward; the only discernible association was that particularly energetic waves from the northern sector can trigger changes in the patterns of shoreline variability and that increased variability might be sustained by increases in offshore wave steepness. It was also found that the fronting beachrock reef exerts significant geological control on beach hydrodynamics. Hydrodynamic modelling and observations during an energetic event showed that the reef can filter wave energy in a highly differential manner, depending on its local architecture. In some areas, the reef allows only low-energy waves to impinge on the shoreline, whereas elsewhere penetration of higher waves is facilitated by the low elevation and limited width of the reef or by the presence of an inlet. Wave/reef interaction can also generate complex circulation patterns, including rip currents that appeared to be also constrained by the reef architecture.

Mean alongshore currents observed on two barred beaches are compared with predictions based on the one-dimensional, time-and depth-averaged alongshore momentum balance between forcing (by breaking waves, wind, and 10-100 km scale alongshore surface slopes), bottom stress, and lateral mixing. The observations span 500 hours at Egmond, Netherlands, and 1000 hours at Duck, North Carolina, and include a wide range of conditions with maximum mean currents of 1.4 m/s. Including rollers in the wave forcing results in improved predictions of the observed alongshore-current structure by shifting the predicted velocity maxima shoreward and increasing the velocity in the bar trough compared with model predictions without rollers. For these data, wave forcing balances the bottom stress within the surfzone, with the other terms of secondary importance. The good agreement between observations and predictions implies that the one-dimensional assumption holds for the range of conditions examined, despite the presence of small alongshore bathymetric nonuniformities. With stronger bathymetric variations the model skill deteriorates, particularly in the bar trough, consistent with earlier modeling and laboratory studies. 1. Introduction Models of the alongshore current in the nearshore often are based on the one-dimensional (l-D), depth-integrated, and time-averaged alongshore momentum balance between wind, wave, and tidal forcing, bottom stress, and lateral mixing [Longuet-Higgins, 1970; Thornton and Guza, 1986, among many others]. Breaking waves are the most important forcing mechanism in the surfzone, although wind [Whirford and Thornton, 1993' Feddersen et al., 1998] and tidal [Houwman and Hoekstra, 1998] forcing can contribute significantly. Predictions of 1-D models, in which alongshore variations in waves and bathymetry are neglected, compare favorably with observations on (near) planar beaches [e.o Thornton and Guza, 1986]. However, on barred beaches, predictions [e.g., Church and Thornton, 1993] of a strong, narrow current jet on the seaward side of the bar crest and near-zero flow in the bar trough differ from the observed broadly distributed (in the cross-shore) current, with max-1WL]Delft Hydraulics, Marine and Coastal Management, Delft, Netherlands.

The coupled ocean-atmosphere-wave-sediment transport modeling system (COAWST) enables simulations that integrate oceanic, atmospheric, wave and morphological processes in the coastal ocean. Within the modeling system, the three-dimensional ocean circulation module (ROMS) is coupled with the wave generation and propagation model (SWAN) to allow full integration of the effect of waves on circulation and vice versa. The existing wave-current coupling component utilizes a depth dependent radiation stress approach. In here we present a new approach that uses the vortex force formalism. The formulation adopted and the various parameterizations used in the model as well as their numerical implementation are presented in detail. The performance of the new system is examined through the presentation of four test cases. These include obliquely incident waves on a synthetic planar beach and a natural barred beach (DUCK' 94); normal incident waves on a nearshore barred morphology with rip channels; and wave-induced mean flows outside the surf zone at the Martha's Vineyard Coastal Observatory (MVCO). Model results from the planar beach case show good agreement with depth-averaged analytical solutions and with theoretical flow structures. Simulation results for the DUCK' 94 experiment agree closely with measured profiles of cross-shore and longshore velocity data from Garcez-Faria et al. (1998, 2000). Diagnostic simulations showed that the nonlinear processes of wave roller generation and wave-induced mixing are important for the accurate simulation of surf zone flows. It is further recommended that a more realistic approach for determining the contribution of wave rollers and breaking induced turbulent mixing can be formulated using nondimensional parameters which are functions of local wave parameters and the beach slope. Dominant terms in the cross-shore momentum balance are found to be the quasi-static pressure gradient and breaking acceleration. In the alongshore direction, bottom stress, breaking acceleration, horizontal advection and horizontal vortex forces dominate the momentum balance. The simulation results for the bar / rip channel morphology case clearly show the ability of the modeling system to reproduce horizontal and vertical circulation patterns similar to those found in laboratory studies and to numerical simulations using the radiation stress representation. The vortex force term is found to be more important at locations where strong flow vorticity interacts with the wave-induced Stokes flow field. Outside the surf zone, the three-dimensional model

Although macrobenthic assemblages are considered as major players in many ecosystems around the world, the ecology of Caspian Sea macrobenthos is currently understudied. This study describes the species composition and quantitative distribution of macrobenthos in the southern Caspian Sea and relates the distribution to seasonal changes at three depths (1, 5 and 10 meters) on the Boojagh Marine National Park (BMNP) coast in the southern Caspian Sea between the summers of 2015 and 2016. To investigate the distribution of macrobenthos in BMNP, the data of 450 samples were analyzed. In this study sixteen species were identified: Cerastoderma glaucum, Mytilaster lineatus, Pyrgula grimmi, Anisus kolesnikovi, Stenogammarus carausui, Paraniphargoides motasi, Onisimus caspius, Pterocuma pectinatum, Pterocuma sowinskyi, Pseudocuma (Stenocuma) gracile, Nais sp., Hypania invalida, Manayunkia caspica, Streblospio gynobranchiata, Hediste diversicolor, Amphibalanus improvisus. Among them, the non-...

En este artículo se realiza un estudio numérico para explicar el comportamiento de la pluma estuarina del río Atrato. Se presentan los resultados obtenidos en la calibración del modelo ELCOM, la cual fue realizada con datos de campo recolectados en tres campañas oceanográficas. Se realizaron una serie de experimentos numéricos para analizar la respuesta del sistema a diferentes condiciones climáticas y oceánicas. Dicho análisis ayudó en la descripción de los patrones de circulación en el golfo de Urabá. Se encontró que el río Atrato forma una pluma estuarina estable, que esta principalmente dominada por la acción del viento. La marea mostró ser importante solo a lo largo del ciclo diurno. La descarga de los ríos también mostró que tiene importancias especialmente en la formación de una pluma boyante.

The inner shelf, the transition zone between the surfzone and the midshelf, is a dynamically complex region with the evolution of circulation and stratification driven by multiple physical processes. Cross-shelf exchange through the inner shelf has important implications for coastal water quality, ecological connectivity, and lateral movement of sediment and heat. The Inner-Shelf Dynamics Experiment (ISDE) was an intensive, coordinated, multi-institution field experiment from September–October 2017, conducted from the midshelf, through the inner shelf, and into the surfzone near Point Sal, California. Satellite, airborne, shore- and ship-based remote sensing, in-water moorings and ship-based sampling, and numerical ocean circulation models forced by winds, waves, and tides were used to investigate the dynamics governing the circulation and transport in the inner shelf and the role of coastline variability on regional circulation dynamics. Here, the following physical processes are h...

En el presente estudio, se determinó la Línea de Más Alta Marea para el área comprendida entre las poblaciones de Candelillas de la Mar y Salahondita, ubicada sobre el Litoral Pacífico Colombiano (LPC), Pacífico Sudeste. Se efectuó un análisis armónico a las series de tiempo de nivel del mar medidas in situ, y a las que se generaron a partir de modelamiento numérico (considerando la escasa información disponible del nivel de mar en esta área). La marea meteorológica fue simulada empleando técnicas estadísticas de Montecarlo; considerando la naturaleza estocástica de esta variable. El comportamiento descrito por las series medidas in situ y modeladas, se analizó a partir del Test de normalidad (test de Kolmogorov-Smirnov y Shapiro-Wilk). Posteriormente, estas fueron correlacionadas por medio del método de correlación de Spearman, donde los cambios en la morfología de la costa y la ausencia de información batimétrica de algunas áreas, condicionó el comportamiento de los coeficientes o...

Up-current-rotated, shoreface-connected ridges are found in various coastal areas around the world. An often-quoted conjecture is that these ridges form during storm conditions through free instabilities in the erodible bed. Under these conditions both waves and currents are expected to play a significant role in the hydrodynamics. Although some existing models have included the effects of waves parametrically in their bottom friction terms and sediment equations, the dynamical effects of wave–current interaction have not been explored. In this paper we begin to rectify this by considering the effects of wave–current interaction on the bed-form instabilities of a simple model. This raises the possibility of unsteady alongshore flows and questions about the roles of wave parameters and boundary conditions, which we address here. We show that the flow is stable under the wave forcing; however the waves do affect the bed-form instability. The main dynamical effect of the waves is in al...

In this article we estimate the rate of intra-annual and annual longshore sediment transport, inflenced by waves in the delta formed by the mouth of the Turbo river, located on the eastern margin of the Gulf of Urabá, specifially Punta Yarumal, from three equations proposed by various authors. The article contains an overview of the area of interest, a summary of the chosen methodology to develop this study, and fially, once the estimated longshore transport rates are calculated, the results, discussion and conclusions are presented.

This Special Issue assembles pioneering research on nearshore ecosystems distributed among all world oceans, from waters spanning the Artic and Antarctic (Figure 1). These works are organized according to the major themes of biodiversity, biogeography, and species distribution, bridged by the subjects of species discovery, species loss, and habitat change. Embedded topics relevant to the present day direct and indirect societal impacts on marine nearshore biodiversity include fishery management, coral reef biodiversity, and extinction. The use of innovative molecular tools to address taxonomic questions and biodiversity distinguishes this collection from any published before the relatively recent development of the field of metagenomics. Likewise, the advantages of global databases founded within the last 15 years, like the citizen science platform iNaturalist, are demonstrated with their application in reporting species richness in difficult environments that challenge observations. In summary, this Special Issue presents an informed overview of current and pressing topics in marine nearshore biodiversity.

Se presenta una metodologia para simular numericamente el crecimiento de una barra de sedimentacion en un estuario, generada por la conscruccion de una isla artificial. Se tiene en cuenta el regimen impermanente producido por la marea y el caracter fino del sedimento. Dado el disimil entre las escalas temporales hidrodinamicas y de evolucion morfologica, se plantea una tecnica en la cual se determinan y ensayan escertarios de marea medio anuales. Luego de cada actualizacion de la morfologia se vuelven a calcular las condiciones hidrodinamicas, hasta llegar al estado final de equilibrio. Se utilizan un modelo hidrodinamico y uno sedimentologico de tipo bidimensional, previamente desarrollados. Tambien se incluye el efecto de las olas. La metodologia se aplica a las islas artificiales diseinadas para proteger las pilas del puente principal del proyecto de conexion fisica Buenos Aires-Colonia, sobre el Rio de la Plata.

A beach sedimentation problem is presented. This problem involves assessing the impact and importance of land-based sediment sources (erosion from gullies during intense rainfall, and directly from cliffs by wave action) on morphodynamic changes at a beach. The site motivating the study is La Barrosa beach, Spain. The location is described and a discussion of possible approaches presented. A schematized representation of a gully and beach is used. A hybrid approach is adopted, in which sediment deposition by runoff (and to a lesser extent cliff erosion) is modelled using wave-resolving hydrodynamic models. It is found that significant amounts of sediment can be supplied by gully runoff during storms. For small runoffs the swash can be involved in determining the region of deposition within the gully area, with longer period motions favouring increased sediment deposition at gully sides. Simulations also show that swash motions can erode gully sides, and the presence of a cross-shore jet associated with the swash and gullies can also impact on sediment movement. Longer term, wave-averaged morphodynamic modelling (without a swash zone) indicates that runoff deposits subsequently diffuse laterally, whether under normal or oblique incidence. These simulations also reveal the possibility of underlying crescentic bar-shedding dynamics that may pertain during changes of wave conditions.

Although macrobenthic assemblages are considered as major players in many ecosystems around the world, the ecology of Caspian Sea macrobenthos is currently understudied. This study describes the species composition and quantitative distribution of macrobenthos in the southern Caspian Sea and relates the distribution to seasonal changes at three depths (1, 5 and 10 meters) on the Boojagh Marine National Park (BMNP) coast in the southern Caspian Sea between the summers of 2015 and 2016. To investigate the distribution of macrobenthos in BMNP, the data of 450 samples were analyzed. In this study sixteen species were identified: Cerastoderma glaucum, Mytilaster lineatus, Pyrgula grimmi, Anisus kolesnikovi, Stenogammarus carausui, Paraniphargoides motasi, Onisimus caspius, Pterocuma pectinatum, Pterocuma sowinskyi, Pseudocuma (Stenocuma) gracile, Nais sp., Hypania invalida, Manayunkia caspica, Streblospio gynobranchiata, Hediste diversicolor, Amphibalanus improvisus. Among them, the non-...

La variabilidad del nivel medio del mar puede estar asociada a varios factores tales como calentamiento global, sismos, marea astronómica, presión atmosférica, viento y oleaje. La transformación del oleaje en aguas someras genera cambios en el nivel medio del mar que se conoce como sobreelevación por oleaje. Los cambios en el nivel medio del mar están relacionados al esfuerzo de radiación del oleaje el cual se define como el flujo de momento asociado al movimiento orbital de las partículas de agua. Cuando el oleaje se propaga en aguas someras la longitud disminuye y la altura aumenta. Estos cambios generan gradientes del esfuerzo de radiación los cuales inducen la transferencia de momento del oleaje al movimiento de la columna de agua. Al disminuir la longitud y aumentar la altura del oleaje, aumenta su inclinación rompiendo en la zona de rompiente, disminuyendo el nivel medio del mar. En la zona de espuma el nivel medio del mar tiende a aumentar hasta alcanzar un máximo en la zona de lavado.

This paper presents the numerical study to explain the driving forces that affect the oceanographic dynamics in the Gulf of Uraba, Colombia. The steps followed for the calibration of a mathematical model known as ELCOM are showed. Several numerical experiments were conducted to analyze the model sensitivity to numerical and physical driving forces. This analysis helps us to describe the circulation patterns in the Gulf of Uraba. Field data showed that the Gulf water is stratified, explained by the discharge of the Atrato River. The wind direction is very important to explain the Atrato river plume dynamics. The simulated circulation patterns were analyzed in two typical climatic seasons in the zone. Norwesterly and southwesterly winds were studied and the model showed that if winds are mainly southwesterlies the plume leaves the Gulf by its northeastern boundary; on the other hand, northwesterly winds are able to invert the plume direction, and it is confined to the south region of the Gulf. Other driving forces (tides, Earth's rotation, among others) show particularly important effects for some local zones.

The problem of sandbar migration on the storm timescale is revisited with a 3D waveresolving hydro-sedimentary model. The model accurately simulates the successive offshore and onshore bar migration observed in a large-scale flume experiment (LIP11D) in response to wave forcing representing storm and post-storm (recovery) conditions. The diagnosis of sand transport and the analysis of a composite asymmetric wave cycle reveal the migration mechanisms in each phase. In all cases, sediment resuspension is dominated by breakinginduced turbulence, while net sediment transport and bed profile evolution are primarily the result of undertow distribution across the sandbar, rather than a trade-off between onshore and offshore fluxes. In the erosion phase, a strong undertow carries the mobilized sediment seaward of the bar crest. In the accretion phase, the sandbar becomes the breaking point to more moderate waves and the undertow is limited to the lee-side of the bar, causing an counterflow ...

Emergent vegetation, covering floodplains and wetlands, has an important role in fluvial ecosystems being able to control the fluxes of sediment, nutrients and contaminants. Proper understanding of flow resistance processes is crucial on the development of reliable tools for designing non-erodible channels. The main objective of this study is the quantification of the forces, per unit bed area, acting on the stems and the respective coefficient. Particular goals include a characterization and quantification of the flow within vegetated areas susceptible to be simulated by dense arrays of vertical emergent stems and a discussion of the dependence of the drag coefficient on parameters that characterize this kind of flows. To achieve the goals, experimental tests simulating rigid and emergent vegetation condition with varying and constant density of stems were performed. The data acquisition consisted mainly in 2D instantaneous velocities maps measured with a Particle Image Velocimetry system (PIV) and the data treatment was performed with the Double-Averaging methodology (DAM). The flow characterization shows an important contribution of form-induced stresses, namely longitudinal and shear stresses which are of the order of magnitude of Reynolds stresses. Hence, in general, these stresses should not be neglected within the balance for the flow resistance. The results show that the drag force seems uncorrelated with the density of stems but impacted by the longitudinal variation of this. For the range of investigated Rep and m, CD seems uncorrelated with Rep. CD is larger for lower relative flow depths, revealing the influence of the channel.

BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access titles in the biological, ecological, and environmental sciences published by nonprofit societies, associations, museums, institutions, and presses.

Up-current-rotated, shoreface-connected ridges are found in various coastal areas around the world. An often-quoted conjecture is that these ridges form during storm conditions through free instabilities in the erodible bed. Under these conditions both waves and currents are expected to play a significant role in the hydrodynamics. Although some existing models have included the effects of waves parametrically in their bottom friction terms and sediment equations, the dynamical effects of wave–current interaction have not been explored. In this paper we begin to rectify this by considering the effects of wave–current interaction on the bed-form instabilities of a simple model. This raises the possibility of unsteady alongshore flows and questions about the roles of wave parameters and boundary conditions, which we address here. We show that the flow is stable under the wave forcing; however the waves do affect the bed-form instability. The main dynamical effect of the waves is in al...

Hydrodynamics applied to the management and conservation of marine and coastal ecosystems: Gorgona Island, Colombian Pacific Ocean. Playa Palmeras (Gorgona National Park) is one of the most important sites for sea turtle nesting in South and Central America. Because of the morphological processes affecting the beach, the turtle nests are increasingly exposed to the impact of waves and tides, threatening conservation. A study was made to determine the hydrodynamical processes of the zone adjacent to Playa Palmeras, which affects directly the morphodynamical behavior of the beach and thus the preservation of the nests. Field measurements and numerical modeling were used to obtain the general circulation patterns and thermohaline structure behavior in the area in order to determine the spatial and temporal variability of waves and its effects on the beach. A marked seasonality was found, both in the waves and the currents, influenced mainly by the meridional displacement of the iTCZ (inter-Tropical Convergence Zone) and an interannual variability of the waves, associated with ENSO (El Niño Southern Oscillation). The flooding levels of the beach were determined and flooding probability maps were made, where safer sites to locate the turtle nests could be identified. These maps serve the officials responsible of monitoring the turtles as a tool to take decisions on moving the nests, since they have flood risk information for any point on the beach. The results show that the middle zone north of the beach is the one with the lowest risk of flooding, therefore the most appropriate zone to relocate nests that are in high risk areas.

Introducción: Para Costa Rica, los estudios realizados en el Pacífico Tropical Este o PTE son importantes ya que se relacionan con el Corredor Marino del Pacífico Este Tropical, el cual es un esfuerzo de conservación multinacional. El presente estudio describe los parámetros físicos de temperatura del mar y salinidad del océano de las masas de agua que rodean a la Isla del Coco y su entorno, el PTE, a través del análisis de perfiles de CTD obtenidos durante campañas hidrográficas realizadas entre el año 2008 y el 2012; y comparar los resultados de los datos in-situ con los del reanálisis del modelo HYCOM-NCODA. Métodos: Se compilaron los resultados de 8 diferentes campañas científicas a la Isla del Coco de abril de 2008, marzo de 2009, abril de 2010, julio de 2011 y marzo de 2012. También se analizan las campañas de octubre de 2010 y marzo de 2011 en donde se realizó un transecto latitudinal y un transecto longitudinal en las aguas del Pacífico Tropical Este de Costa Rica. En julio ...

The study of ion regulation and osmotic pressure in Caspian Sea aggressive Ctenophore species, plentifully species were amassed by bangnet and motorboat on Noor Coast and Gorgan Gulf. After separation water and ctenophore samples were transferred to choromotography and osmometery laboratories for Ion and Osmotic analysis until were defined that Mnemiopsis leidyi is Osmoconformer or Osmoregultor. The present study of ion regulation and osmotic pressure in Mnemiopsis leidyi in Southern Caspian Sea showed that this species lives in salinities of 12.5-16 ppt, body fluid osmolalities were 237-312 mOsm/lit over the habitat range of 278-354 mOsm/lit. Determinations of Na+, K+ , Mg++, Ca++, So4-- and Cl- ions concentrations in the body fluid of Mnemiopsis leidyi were carried out. Comparative studies between body fluid and sea water revealed that the concectrations of Na+, Mg++, Ca++, So4--and Cl- ions were high significant (P<0.05) in sea water, except the K+ ion concentration.

The Inner Bay of Puno is located on Lake Titicaca in southern Peru, 2.6 m in average depth, 16.0 km in surface area. The mouth of the bay, populated by native reed beds, joins the Outer Bay through the north and south channels. The bay is an example of the negative impact of humans, where they discharge poorly treated wastewater, producing an increase in algal biomass, eutrophication and anoxia. The objective was to estimate the direction and magnitude of the speed of the water current, on an hourly scale controlled by relevant physical processes, between January 23 and 30, 2019. We collected meteorological data, depth and temperature of the water. We performed computational experiments using the ELCOM lake model. The rst scenario considered the closed bay, and as a result presented counterclockwise rotational ow in the north and clockwise in the south, with a speed that varied between 0.5 and 4.0 cm/s. The second scenario considered the entry and exit of water through the north and...

Hydrodynamics applied to the management and conservation of marine and coastal ecosystems: Gorgona Island, Colombian Pacific Ocean. Playa Palmeras (Gorgona National Park) is one of the most important sites for sea turtle nesting in South and Central America. Because of the morphological processes affecting the beach, the turtle nests are increasingly exposed to the impact of waves and tides, threatening conservation. A study was made to determine the hydrodynamical processes of the zone adjacent to Playa Palmeras, which affects directly the morphodynamical behavior of the beach and thus the preservation of the nests. Field measurements and numerical modeling were used to obtain the general circulation patterns and thermohaline structure behavior in the area in order to determine the spatial and temporal variability of waves and its effects on the beach. A marked seasonality was found, both in the waves and the currents, influenced mainly by the meridional displacement of the iTCZ (inter-Tropical Convergence Zone) and an interannual variability of the waves, associated with ENSO (El Niño Southern Oscillation). The flooding levels of the beach were determined and flooding probability maps were made, where safer sites to locate the turtle nests could be identified. These maps serve the officials responsible of monitoring the turtles as a tool to take decisions on moving the nests, since they have flood risk information for any point on the beach. The results show that the middle zone north of the beach is the one with the lowest risk of flooding, therefore the most appropriate zone to relocate nests that are in high risk areas.

The Spatial and temporal variability of macrobenthos in the southern Caspian Sea (Chalus shore) were seasonally investigated from winter 2005 till fall 2006. Samples were taken with a Van Veen grab from depths of 7 and 20 meters along two transects, from Khate Hasht area (western part of coast) to Radio Darya area (eastern part of the coast). Totally, 5 classes of macrobenthos were identified in which the most abundant populations were Polychaeta 68.7% from abundance point of view. Density and biomass of macrobenthos in between seasons were significant (P< 0.05), as the maximum density and biomass of macrobenthos were during the summer and autumn (4251.8±1419 ind/m and 475±243.8 g/m), respectively while the minimum density and biomass were during the spring and winter (725.9±64.5 ind/m2 and 0.3±0.1 (ME±SE) g/m). A significant correlation (P< 0/05) between the density and biomass of macrobenthos with sand percentage and total organic matter (TOM) were found in different seasons...

Para determinar el clima de olas en aguas profundas frente a las costas del Peru, se empleo informacion instrumental de satelite y boyas, que sirvieron para calibrar los datos de olas del reanalisis numerico del Centro Nacional de Prediccion Ambiental (NCEP), que cuenta con informacion de 1979 a 2017. Las alturas de olas se calibraron mediante la aplicacion de un modelo exponencial descrito por Minguez et al. (2011), obteniendose valores de coe˝cientes de correlacion entre 0.7 a 0.9, el sesgo (BIAS) de -0.03 a 0.01 y el error medio cuadratico (RMSE) calculados mostraron entre 0.17 a 0.33, lo que indica una buena aproximacion entre ambas fuentes de informacion, por lo que se ha logrado obtener una informacion de oleaje en aguas profundas que puede ser empleado en analisis de los regimenes medios y extremales como punto de partida para estudios de ingenieria de costas, asi como para estudiar la in˛uencia de los fenomenos El Nino y La Nina sobre el patron de oleaje frente a la zona de ...

Wind- and current-driven flotsam, oil spills, pollutants, and nutrients, approaching the nearshore will frequently appear to slow down/park just beyond the break zone, where waves break. Moreover, the portion of these tracers that beach will do so only after a long time. Explaining why these tracers park and at what rate they reach the shore has important implications on a variety of different nearshore environmental issues, including the determination of what subscale processes are essential in computer models for the simulation of pollutant transport in the nearshore. Using a simple model we provide an explanation for the underlying mechanism responsible for the parking of tracers, not subject to inertial effects, the role played by the bottom topography, and the non-uniform dispersion which leads, in some circumstances, to the eventual landing of all or a portion of the tracers. We refer to the parking phenomenon in this environment as nearshore sticky waters.

We introduce a model for the dynamics of oil in suspension, appropriate for shallow waters, including the nearshore environment. This model is capable of oil mass conservation and does so by evolving the oil on the sea surface as well as the oil in the subsurface. The shallower portion of the continental shelf poses compounding unique modeling challenges. Many of these relate to the complex nature of advection and dispersion of oil in an environment in which wind, waves, as well as currents all play a role, as does the complex bathymetry and the nearshore geography. In this study we present an overview of the model as well as derive the most fundamental of processes, namely, the shallow water advectiion and dispersion processes. With regard to this basic transport, we superate several fundamental challenges associated with creating a transport model for oil and other buoyant pollutants, capable of capturing the dynamics at the large spatio-temporal scales demanded by environmental and hazard mitigation studies. Some of the strategies are related to dimension reduction and upscaling, and leave discussion of these to companion papers. Here we focus on wave-filtering, ensemble and depth-averaging. Integral to the model is the proposal of an ocean dynamics model that is consistent with the transport. This ocean

We use the vortex force formalism to analyze the effect of rip currents on their own wave forcing. The vortex force formalism allows us to decompose the wave forcing into the nonconservative flux of momentum due to wave breaking and the conservative vortex force. Following Yu and Slinn (2003), we consider rip currents initially generated by alongshore variation of wave breaking due to a perturbation of a barred bottom topography. This variation is reduced in magnitude by two current effects on waves: wave ray bending and the flux of wave energy by currents. We compute the change in wave energy caused by these two effects on their own and use this to show that their relative magnitude scales with the square of the ratio of the length to width of the rip current. Both effects increase the wave height over the channels of the longshore bar, which leads to more wave breaking and counterbalances its longshore variation due to bottom refraction. In comparison to wave breaking, the change in the vortex force is negligible. Next, we show how the reduction in wave breaking is similar to an enhanced bottom friction. We then analyze the dependence of this relationship on the breaking parameterization, angle of incidence of the waves, and bottom drag law.

Up-current-rotated, shoreface-connected ridges are found in various coastal areas around the world. An often-quoted conjecture is that these ridges form during storm conditions through free instabilities in the erodible bed. Under these conditions both waves and currents are expected to play a significant role in the hydrodynamics. Although some existing models have included the effects of waves parametrically in their bottom friction terms and sediment equations, the dynamical effects of wave–current interaction have not been explored. In this paper we begin to rectify this by considering the effects of wave–current interaction on the bed-form instabilities of a simple model. This raises the possibility of unsteady alongshore flows and questions about the roles of wave parameters and boundary conditions, which we address here. We show that the flow is stable under the wave forcing; however the waves do affect the bed-form instability. The main dynamical effect of the waves is in al...

Distribution of temperature and salinity during recent oceanographic campaigns in the Eastern Tropical Pacific of Costa Rica. Introduction: In Costa Rica, studies done in the Eastern Tropical Pacific or ETP are important because of their interaction/relationship with the Eastern Tropical Pacific Seascape, a known multinational conservation initiative. The present study describes the physical parameters of sea temperature and salinity around Cocos Island and its environment, the ETP, using CTD profiles. Methods: Data were

Palabras claves: Fenómenos macroclimáticos, ciclo anual, Precipitación, caudal, Cuantificación lineal, Transformada en onditas, percentiles. ... Resumen Se estudia la influencia de fenómenos climáticos de gran escala sobre la variabilidad temporal de la hidrología de Colombia a ...

This study concludes activities and researches during May-September, 2003. Zarrinkola and Marzoonabad Ab-bandans (Artificial Wetlands) have been selected for this work. There is one breeder group of Whiskered Tern (Chlidonias hybridus) (930 pairs) in Zarrinkola Abbandan, where as, two breeder groups (1390 pairs) were in Marzoonabad Ab-bandan. Clutch size was 1-4 eggs in Zarrinkola and Marzoonabad second breeder group, where as, in the first breeder group was 1-5 eggs. Brood size included 1-3 chicks. Breeding success in Zarrinkola, first and second breeder group was %57/08, %82/96 and %75/87, respectively. There is not any significant difference between clutch size and brood size with breeding success (p>0/05). There is significant difference (p<0/05) between the rates of losses among the Section 5: Caspian Sea, Ecology and Biology 266 reproductive phenology stages. Because of intense rainfall, the maximum loss was during the incubation time (egg stage).

The inner shelf, the transition zone between the surfzone and the midshelf, is a dynamically complex region with the evolution of circulation and stratification driven by multiple physical processes. Cross-shelf exchange through the inner shelf has important implications for coastal water quality, ecological connectivity, and lateral movement of sediment and heat. The Inner-Shelf Dynamics Experiment (ISDE) was an intensive, coordinated, multi-institution field experiment from September–October 2017, conducted from the midshelf, through the inner shelf, and into the surfzone near Point Sal, California. Satellite, airborne, shore- and ship-based remote sensing, in-water moorings and ship-based sampling, and numerical ocean circulation models forced by winds, waves, and tides were used to investigate the dynamics governing the circulation and transport in the inner shelf and the role of coastline variability on regional circulation dynamics. Here, the following physical processes are h...

RESUMEN El objetivo de este artículo es la presentación del Sistema PORT 21 de previsión de oleaje y Oceanografía Operacional (OO) de aplicación en la Región Sudamericana. Para la comprensión integral del sistema se citan los modelos usados y se muestra en primer lugar la metodología adoptada para su integración en la implementación de PORT 21. Posteriormente se describen los casos estudiados para ilustrar el funcionamiento del sistema, incluyendo un caso de validación y calibración del sistema en el sur de Chile, para finalmente resumir los resultados hasta ahora obtenidos. Se presenta una revisión de las dependencias de datos de entrada que tiene el sistema describiéndose los diferentes modelos y fuentes de datos de viento y de oleaje existentes en el estado del arte, alguno de los cuales han sido seleccionados para el uso rutinario del sistema. En las conclusiones sobre los resultados obtenidos, se realiza un análisis crítico respecto de los objetivos alcanzados hasta la fecha y se describen las tareas a realizar en el futuro.

Resumen Se presenta el proceso de calibración y validación de un modelo hidrodinámico para simular las mareas, corrientes y condiciones de salinidad y temperatura en el área costera de la bahía de Santa Marta. Se desarrolla una metodología que incluye la implementación numérica del modelo y el desarrollo de mediciones de campo que se comparan con las simulaciones. Se estima el error entre las mediciones y las simulaciones para determinar cuantitativamente la confiabilidad del modelo.

ABSTRACT. Distribution of temperature and salinity during recent oceanographic campaigns in the Eastern Tropical Pacific of Costa Rica. Introduction: In Costa Rica, studies done in the Eastern Tropical
Pacific or ETP are important because of their interaction/relationship with the Eastern Tropical Pacific Seascape, a known multinational conservation initiative. The present study describes the physical parameters of sea temperature and salinity around Cocos Island and its environment, the ETP, using CTD profiles. Methods: Data were obtained in April 2008, March 2009, April 2010, July 2011 and March 2012 near this island. Latitudinal and longitudinal transects were also done during October 2010 and March 2011 in a broader Costa Rican ETP region. In July 2012, three latitudinal transects were done around Cocos Island. Records were obtained using a CTD, measuring conductivity, temperature and pressure, among other variables. Results: Tropical Surface Water was observed in the upper 50m, showing temperatures above 25°C and salinities below 33psu. Below the surface waters, Subsurface Subtropical Water was detected below a 60m depth, showing temperatures colder than 25°C and salinities around 35psu. The transition between these waters was around 50-60m in depth.
Temperature and salinity results were related with the atmosphere conditions observed, in which ETP variability was strongly influenced by the Inter Tropical Convergence Zone migration. Conclusions: This study
also showed that reanalysis data from the HYCOM-NCODA general circulation model are comparable and in a good agreement with the CTD profiles. Temperature and salinity HYCOM data also reproduced, in general terms, the main characteristics of CTD data, having some small differences in the deeper levels. This reanalysis data set could also be used to study the tropical ocean dynamics, in wider ETP regions and for different seasons.

A multi-scale asymptotic theory is derived for the evolution and interaction of currents and surface gravity waves in water of finite depth, under conditions typical of coastal shelf waters outside the surf zone. The theory provides a practical and useful model with which wave-current coupling may be explored without the necessity of resolving features of the flow on space and time scales of the primary gravity-wave oscillations. The essential nature of the dynamical interaction is currents modulating the slowly evolving phase of the wave field and waves providing both phase-averaged forcing of long infra-gravity waves and wave-averaged vortex and Bernoulli-head forces and hydrostatic static set-up for the low-frequency current and sea-level evolution equations. Analogous relations are derived for wave-averaged material tracers and density stratification that include advection by horizontal Stokes drift and by a vertical Stokes pseudo-velocity that is the incompressible companion to the horizontal Stokes velocity. Illustrative solutions are analysed for the special case of depth-independent currents and tracers associated with an incident surface wave field and a vortex with O(1) Rossby number above continental shelf topography.