Tidal Circulation Research Articles

Chloride Diffusion Analysis of Concrete Members Considering Depth-Dependent Diffusion Coefficients and Effect of Reinforcement Presence

AbstractThis paper presents the results of an experimental investigation on chloride diffusion in plain concretes and reinforced concretes. Concretes were exposed to chloride environment simulated by a self-designed tidal circulation device for 35, 70, and 100 days. Chloride concentrations (Cl−) in powder samples which were milled layer-by-layer from plain concretes and drilled along the direction of rebar from reinforced concretes were measured. Cl− at the apex of the rebar were compared to that at the corresponding depth in plain concretes to study the blocking effect of rebar. Meanwhile, diffusion coefficients (Dx) at different depths were determined by applying Fick’s second law to study the depth-dependent characteristic of Cl− diffusion. The results show that along the direction of penetration, Dx decreases first and then increases; rebar does change the distribution of Cl−, and the larger the diameter, the greater the effect. The effect of rebar is not only embodied in the physical obstruction but ...

Near-Channel Velocities in the Presence of a Dredge-Spoil Island

AbstractA vessel-mounted acoustic Doppler current profiler study focusing on channel-scale flow patterns in Galveston Bay near the Houston Shipping Channel and the artificial (dredge spoil) Mid-Bay Island is described. Winds of 5–7 m/s at 215–230° from N were present during data collection, which was conducted both in the deep channel (15 m) and along the shallow (3 m) open water near the channel. For both peak ebb and flood conditions, the tidal circulation forces flow in a direction opposing the wind, which appears to be due to a large-scale flow divergence forced by Mid-Bay Island. The strongest wind-opposing currents were measured closest to the island. During peak flood flow, the shape of the along-channel velocity profile for the open water upwind of the channel at Mid-Bay Island indicated uniform flow, and the salinity profile indicated a well-mixed water column. The near-island along-channel velocity profile showed a near-linear trend and the salinity profile indicated a stratified water column, s...

Retraction: Brown, S. and Jachec, S. (2012). “Projected Impacts of Post-Breach Tidal Circulation Within Pleasant Bay, MA Via Numerical Simulations.” J. Waterway, Port, Coastal, Ocean Eng. , 10.1061/(ASCE)WW.1943-5460.0000184 (Sep. 20, 2012)

Retraction: Brown, S. and Jachec, S. (2012). “Projected Impacts of Post-Breach Tidal Circulation Within Pleasant Bay, MA Via Numerical Simulations.” <i>J. Waterway, Port, Coastal, Ocean Eng.</i> , 10.1061/(ASCE)WW.1943-5460.0000184 (Sep. 20, 2012)

Rifting processes and ice-flow modulation observed on Mertz Glacier, East Antarctica

AbstractWe investigated the evolution of two major rifts cutting across Mertz Glacier Tongue, East Antarctica, using a combination of satellite images and 60 day sets of GPS data from two stations deployed either side of the western rift in 2007. The eastern rift began to open in the early 1990s, and the western rift initiated in 2002 in conjunction with the collision of a large iceberg with the tongue. Velocity time series derived from the 2007 GPS data exhibited strong variations at tidal periods modulated by sea-surface height and sea-surface slope and reproduced here with a conceptually simple model. We found that opening of the western rift in 2002 leads to a dramatic change in behavior of the tongue as the large range in velocity (700–2400 m a−1) observed in 2000 was largely reduced (1075–1225 m a−1) in 2007. Opening of the western rift decoupled the glacier from the transverse loading on the tongue driven by east–west tidal circulation. This loading previously induced time-varying lateral drag, which caused the large velocity range. Our results suggest changes in the mechanical behavior of an ice tongue impact the dynamics of the outlet glacier system and should be considered in longer-term mass-balance evaluations.

Elaboración de mallas computacionales para la implementación del Modelo ADCIRC (Advance Three Dimensional Circulation Model) en el Archipiélago de Galápagos

El estudio de las variables oceanográficas físicas es un tema de gran interés para entender otros procesos relevantes como los qímicos, biológicos, transferencia de calor, entre otros. En el Archipiélago de Galápagos en particular, el conocimiento de estos procesos es la clave para entender su biodiversidad y equilibrio, única en el mundo. De los fenómenos más básicos que controlan todo el régimen físico, las olas de viento y la circulación inducida por las mareas pueden explicar una parte importante de otros procesos secundarios fundamentales como los de transporte (e.g., larvas, plancton, peces, sedimentos, químicos, calor, entre otros), que tienen a su vez un efecto directo sobre los ecosistemas. En el presente artículo, se presenta la documentación algunos de los desarrollos preliminares para la implementación del modelo ADIRC (Advanced Three Dimensional Circulation Model). Un aspecto importante es el diseño y elaboración de las mallas computacionales, compuesto de un grupo de pasos de pre-procesamiento que requiere homogeneización de datos de batimetría y mallas de cálculo para garantizar la adecuada representación de los procesos físicos y evitar inestabilidad numérica en operaciones posteriores. Varios algoritmos han sido desarrollados con este propósito y son presentados aquí. Con estos avances, se realizó una implementación preliminar de ADCIRC para evaluar la funcionalidad de las mallas.

Influence of the Indonesian Throughflow on the upwelling off the east coast of South Java

A wave–tide–circulation coupled model is used to simulate upwelling off the south coast of Java, Indonesia. The results show that the vertical velocity off East Java is stronger than other parts in this area. The strongest vertical velocity is located approximately at 80 m depth. The annual averaged values of upwelling are 2.3 × 10−6 and 1.06 × 10−5 m/s for south of West Java and south of East Java, respectively. The vertical velocity from the model shows that upwelling off West Java has seasonal variability, while it is quite steady and strong off East Java. Additional numerical experiments show that the wind is not the dominant factor for the steady upwelling off the southern part of East Java. It is then hypothesized that the Indonesian Throughflow (ITF) may be responsible for the upwelling. To test this hypothesis, two scenarios are implemented, both of which block the outflow of the ITF. Sensitive study shows that the ITF plays a key role in the formation of East Java upwelling. The effect of the ITF can account for about 55 %–65 % of the upwelling.

The relative importance of the wind-driven and tidal circulations in Malacca Strait

The Malacca Strait is traditionally treated as a typical tidally-driven channel with the wind-driven and other components considered negligible. However, the strait is frequently affected by intense tropical weather events distorting the background monsoon winds. The variable winds can create large wind-stress curl at the surface level. To answer the question of how significant the wind-driven circulation is to the total circulation, numerical simulations are carried out by isolating or superimposing the different driving mechanisms. Comparison of the time series at selected points reveals that the winds significantly affect the tidal currents in different ways in the northern and southern strait. In the northern wide strait, the tidal current is enhanced while in the southern narrow channel it is weakened. Experiments with uniform water depth confirm that the weakening is mainly due to the interaction among tidal current, wind-driven current and bathymetry in the southern strait. Spectral analysis of the currents in the whole MS quantifies that the wind-driven current energy is more significant in the northern channel than in the southern one. Furthermore, winds with high intensity and large wind-stress curl can produce an eddy as large as the northern channel width which significantly distorts the tidal circulation especially during the neap tide. Vorticity analysis shows that the eddy in the northern Malacca Strait is purely wind-driven. Our study highlights that the wind stress, which has been ignored in previous studies in this region, is an important driver of the circulation in the Malacca Strait even when tidal forcing is strong.

Tidal dynamics of the Terminos Lagoon, Mexico: observations and 3D numerical modelling

The tidal circulation patterns in the Terminos Lagoon were studied based on the analysis of 1 year of measurements and numerical simulations using a baroclinic 3D hydrodynamic model, the MARS3D. A gauging network was installed consisting of six self-recording pressure–temperature sensors, a tide gauge station and two current profilers, with pressure and temperature sensors moored in the main lagoon inlets. Model simulations were validated against current and sea level observations and were used to analyse the circulation patterns caused by the tidal forcing. The numerical model was forced with eight harmonic components, four diurnal (K 1, O 1, P 1, Q 1) and four semi-diurnal (M 2, S 2, N 2, K 2), extracted from the TPX0.7 database. The tidal patterns in the study area vary from mixed, mainly diurnal in the two main inlets of the lagoon, to diurnal in its interior. The tidal residual circulation inside the lagoon is dominated by a cyclonic gyre. The results indicate a net flux from the southwest Ciudad del Carmen inlet (CdC) towards the northeast Puerto Real inlet (PtR) along the southern side of the lagoon and the opposite in the northern side. The results indicate two areas of strong currents in the vicinity of the inlets and weak currents inside the lagoon. The area of strong currents in the vicinity of the CdC inlet is larger than that observed in the PtR inlet. Nevertheless, the current analysis indicates that the highest current speeds, which can reach a magnitude of 1.9 m s−1, occurred in PtR. A further analysis of the tide distortion in the inlets revealed that both passages are ebb dominated.

Marine Litter Observed by Tidal Circulation at Phi Phi Islands, Andaman Sea

Background: Saphan Hin is well known park located in the southern east coast of Phuket. Marine litter, especially light and floatable litter such as plastic, is known to be the cause of death in marine animals. Therefore, prediction of light floatable marine litter will greatly help to understand behavior of marine litter transportation at Saphan Hin and leads to proper waste management in vulnerable areas.

Intra- and inter-seasonal variability of nutrients in a tropical monsoonal estuary (Zuari, India)

A study was conducted to understand the intra- and inter-seasonal variability of dissolved oxygen and nutrients in a tropical monsoon estuary (Zuari in Goa, India). We adopted a dual sampling approach with (a) daily or alternate day sampling at a fixed location in the mid-estuarine zone and (b) longitudinal transect sampling from freshwater end to mouth during spring and neap tides of each month for about a year. Multivariate statistical analyses of oxygen and nutrients were carried out to evaluate the hypotheses: (i) biogeochemical processes chiefly regulate their variability and (ii) anthropogenic inputs lead to material accumulation in the estuary. Multivariate statistical analyses helped identify the controlling factors of the oxygen and nutrient variability. Our results significantly revealed (i) physical forcings (freshwater discharge and tidal circulation, these also facilitate sedimentary releases) are more important than biogeochemical processes in determining oxygen and nutrient variability in the water column and (ii) the monsoon driven regular annual flushing makes the system resilient to human interference as the Zuari estuary returns to normalcy by postmonsoon every year. Our study identified the significance of subsurface discharges in transporting mining effluents from the river basin. Results also suggest that extrapolation of controlling factors of biogeochemical variables at a fixed location to the entire estuary is untenable since the relative dominance of forcings vary in time and space in the estuary.

Dynamics of dike effects on tidal circulation around Saemangeum, Korea

A series of dikes was built in Saemangeum located in southwestern Korea and reduced the tidal phase, the current, and the amplitude. Through two dimensional numerical modeling utilizing a finite volume model, we elucidate the mechanism how these dikes modify the tide. Before the dikes were built, the tide was refracted by the coast and the co-phase line was parallel to the coastline. The dikes removed the shallow coastal zone, resulting in faster wave propagation to reduce the phase. The southern leg is parallel to the co-phase line and more effective in blocking the tide than the northern leg that is oblique to the co-phase line. Greater reductions of the tidal phase and flow were found in front of the southern leg. Before the dike, over the site of the southern leg in the direction to the leg, the temporal changes of momentum, friction, and the pressure gradient balance. Upon the completion of the leg, the tidal current and the temporal changes of momentum and friction weakened. The pressure gradient, then, weakened, reducing the tidal amplitude. The northern dike built oblique to the tidal flow reduced only the component normal to the leg, and the Coriolis force did not affect significantly. To balance the Coriolis force, the pressure gradient and, subsequently, the tidal amplitude weaken by lesser amounts.

Modelling study of three-dimensional circulation and particle movement over the Sable Gully of Nova Scotia

The Sable Gully is a broad deep underwater canyon located to the east of Sable Island on the edge of the Scotian Shelf. Being the home of many marine species including the endangered Northern Bottlenose Whale, the Gully was designated as a marine protected area (MPA) in 2004. Better understanding of physical environmental conditions over this MPA is needed for sustainable ecosystem management. In this study, a multi-nested ocean circulation model and a particle tracking model are used to examine the three-dimensional (3D) circulation and movement of particles carried passively by the flow over the Sable Gully. The 3D circulation model is driven by tides, wind, and surface heat/freshwater fluxes. The model performance is assessed by comparing the results with the previous numerical tidal results and current meter observations made in the Gully. The simulated tidal circulation over the Gully and adjacent waters is relatively strong on shallow banks and relatively weak on the continental slope. Below the depth of the Gully rim ( ∼ 200 m), the tidal currents are constrained by the thalweg of the Gully and amplified toward the Gully head. The simulated subtidal circulation in the Gully has a complex spatial structure and significant seasonal variability. The simulated time-dependent 3D flow fields are then used in a particle tracking model to study the particle movements, downstream and upstream areas, and residence time of the Gully. Based on the movements of particles released at the depth of the Gully rim and tracked forward in time, the e-folding residence time is estimated to be about 7 and 13 days in February and August 2006, respectively. The Gully flanks are identified as high retention areas with the typical residence time of 10 and 20 days in February and August 2006, respectively. Tracking particles with and without tides reveals that tidal circulation reduces the value of residence time in the Gully, particularly along the Gully flanks.

Investigation of hydraulics transport time scales within the Arvand River estuary, Iran

Transport time scales are key parameters for understanding the hydrodynamic and biochemical processes within estuaries. In this study, the flushing and residence times within the Arvand River estuary have been estimated using a two-dimensional hydrodynamic model called CE-QUAL-W2. The model has been calibrated and verified by two different sets of field data and using the k-ε vertical eddy diffusivity scheme. Flushing time has been estimated using different methods such as the tidal prism and fraction of freshwater methods. Moreover, residence times have been investigated using pulse residence time, estuarine residence time and remnant function approaches. The results have shown that different methods yield different time scales, and freshwater inflow has the greatest impact upon estimation of residence time, whereas tidal circulation hardly contributes to residence time at all. It has also been shown that the neap-spring circulation and start phase of simulations have negligible effects on the Arvand's time scales. The investigation of bathymetry showed that two sills of the estuary tend to significantly increase residence time. Understanding the applicability of these time scales and their estimation approaches helps us to evaluate the water quality management of estuaries. Copyright © 2013 John Wiley & Sons, Ltd.

A numerical model analysis of the tidal flows in the Bay of Algeciras, Strait of Gibraltar

A numerical model has been applied to study the tidal flows of the Bay of Algeciras in the eastern part of the Strait of Gibraltar, focusing on the M2 semidiurnal constituent. The numerical model was satisfactorily validated against a comprehensive set of observations collected in the bay in the year 2011 and the model outputs were used for a detailed analysis of the local tidal circulation. The M2 net (vertically integrated) transport across the mouth of the bay has an amplitude of 2.7×10−3Sv, while that of the sea surface signal is of ~30cm and is in quadrature with this flow. However, the vertically integrated flow is the result of a pronounced baroclinic structure consisting of an upper (S<37.5) and lower (S>37.5) layers, whose associated transports are one order of magnitude higher. This reveals a noticeable internal tide that is characterized by an inward (to the head of the bay) propagation and a likely quarter-wave resonance. During the rising tide, Atlantic water from the strait comes in and produces the thickening of the upper (Atlantic) layer in the bay, while Mediterranean water of the lower layer is pushed out to join the Mediterranean water stream that is flowing to the west along the Strait of Gibraltar. During the falling tide, Atlantic water flows out of the bay and incorporates to the eastward flow in the strait. In this tidal phase, Mediterranean water flows into the bay. Therefore, Atlantic and Mediterranean waters accumulate in the bay during the rising and falling tide, respectively. This pattern is opposite to that observed in the strait, where the Mediterranean layer thickens during the rising tide and becomes thinner during the falling tide. This suggests that the internal tide in the bay is basically determined by the baroclinic forcing at its mouth imposed by the baroclinic tide of the Strait of Gibraltar.

Impact of Large-Scale Reclamation on Hydrodynamics and Flushing in Victoria Harbour, Hong Kong

Kuang, C.P.; Huang, J.; Lee, J.H.W., and Gu, J. 2013. Impact of large-scale reclamation on hydrodynamics and flushing in Victoria Harbour, Hong Kong.A three-dimensional (3D) hydrodynamic model for the Pearl River Estuary based on Delft3D is established and calibrated to study the changes in tidal circulation and flushing in Victoria Harbour. The tidal circulation and flushing were simulated by this 3D model under the existing reclamation conditions, including Central Reclamation Phases I, II, and III (CRI, CRII, and CRIII), and Wan Chai Reclamation Phase I (WRI). The model is also applied to predict the hydrodynamic changes after the reclamation of proposed Wan Chai Development Phase II (WDII) to be constructed in 2017. Compared to the coastline in 1975 (before large-scale reclamation), the numerical results show that the following changes have taken place after the existing reclamation: (1) The peak flow at all cross sections along Victoria Harbour decreases by about 9–25%, with an average value of about 15% for the existing reclamation; (2) the peak velocity in the eastern harbour near Lei Yue Mun decreases after the existing reclamation because of the reduction of flow, but it increases in the central and western harbour due to the significant narrowing in harbour width; (3) flushing time in Victoria Harbour increases by about 25–40% in the wet season and increases by almost 15–30% in the dry season as a result of the changes of the flow discharge and tidal range. After the reclamation of WDII, the flushing rate and flow discharge in Victoria Harbour only change slightly compared with that under the existing reclamation condition. Another finding is that for the present coastline, the flushing time ranges about 1.5–2.5 days in the wet season and 5–7 days in the dry season.

Experiments of Chloride Ingression in Loaded Concrete Members under the Marine Environment

AbstractThis paper presents the results of an experimental investigation on the effect of load on chloride diffusion in concrete members in tidal zone and salt spray zone which were simulated by using a self-designed tidal circulation device and a salt spray chamber. The concrete members were loaded by using self anchoring at both ends. The load conditions were 0, 0.3, and 0.5 times of the member’s flexural strength (ff). Chloride concentration profiles in concretes were determined after 35, 70, 120, and 180 days of exposure, respectively. Regression analysis of the experimental data was carried out by applying Fick’s law of diffusion to determine the diffusion coefficient (Dc) and chloride concentration on the surface (Cs). The results show that chloride diffusion has a big difference between the two zones; diffusion coefficient (Dc) is time dependent and gradually reduces over time; loads have a certain impact on diffusion; and tensile stress promotes chloride diffusion whereas compressive stress inhibi...

Sub-hourly changes in biogeochemical properties in surface waters of Zuari estuary, Goa

Processes in natural waters are highly variable in time and space. Although changes are expected in short-time scales, how short one could get to measure reliably is subjective to sampling strategies and methodologies. Here, we show that sub-hourly changes in surface waters dissolved oxygen, nutrients, and pigments are measurable and significant in an estuarine system. Tidal circulation has been found to strongly influence the observed changes and has implications to material fluxes in and out of estuaries.

Baroclinic M2 tidal circulation in Algeciras Bay and its implications for the water exchange with the Strait of Gibraltar: Observational and 3-D model results

[1] The M2 tidal circulation in Algeciras Bay (Strait of Gibraltar) is analyzed using a 3-D, nonlinear, baroclinic, hydrodynamic model, in conjunction with observed data series. Results show the influence of the density stratification on the vertical structure of the M2 currents in Algeciras Bay, although its tidal dynamics shows major differences with respect to the Strait of Gibraltar. Whereas the M2 currents in the Strait present mainly barotropic behavior, the baroclinic effects prevail in Algeciras Bay. A notable finding is the presence of a tidal M2 counter-current system between the upper Atlantic and the lower Mediterranean water layers within the Bay, with amplitudes of up to 25 cm s−1. The interface between the two layers oscillates in antiphase relation with respect to the free-surface elevation, with amplitudes of almost 20 m. The presence of the submarine Algeciras Canyon was found to be determinant in the three-dimensional structure of tidal currents within the Bay, strengthening the baroclinic tidal regime of currents. This situation has quantitative consequences for the flow-exchange processes between Algeciras Bay and the outer Strait, with rates 20 times higher than those obtained when considering only the barotropic behavior, as well as inflow/outflow lateral recirculation volumes during half a tidal cycle that account for more than 20% of the net accumulated volume. This flow-exchange system was found to be affected by the nonlinear interaction processes between the first baroclinic period of resonance of Algeciras Bay and the M2 tide.

Deep chlorophyll maximum and plankton community response to oceanic bottom intrusions on the continental shelf in the South Brazilian Bight

The continental shelf of the South Brazilian Bight (Lat 23–28.5°S) is subject to bottom intrusions of the oceanic and nutrient-rich South Atlantic Central Waters (SACW) in summer, to compensate for the Ekman transport of surface waters offshore by northeasterly winds. In winter, shelf waters tend to overturn vertically due to tidal circulation and Ekman convergence of outer-shelf waters driven by southerly winds. From 9 November 2005 to 22 June 2006 the shelf off Santa Catarina State was surveyed to investigate hydrographic conditions and the seasonal dynamics of the plankton cross-shelf distribution and community structure. A strong wind-driven onshore bottom intrusion of the SACW with the formation of two independent deep chlorophyll maximum (DCM) layers on the shelf was clear. Chlorophyll concentrations ranged from 0.07 to 6.2mgm−3 and phytoplankton carbon biomass from 0.2 to 511µgCL−1, mostly as large centric diatoms and in spite of the numerical dominance of small pennates. The mid-shelf DCM was 12m thick between 38 and 50m (1–5% of irradiance) with mean chlorophyll concentrations up to 1.8mgm−3. The DCM on the outer shelf was formed between 60 and 70m depth (1–0.01% surface light) by small pennate diatoms and small phytoflagellates, with chlorophyll concentrations of 0.5–0.7mgm−3. Both DCMs were maintained independently from January to April 2006, and dispersed in June due to water column turnover during cold seasons. In the mid-shelf, the DCM was geographically extended towards the inner shelf and became thicker compared to pre- and post-intrusion periods. The freshwater species Aulacoseira granulata and large centric diatoms including the invasive Coscinodiscus wailesii were frequent along the shelf throughout the sampling period. Oncaea waldemari, Ctenocalanus vanus and Oithona plumifera usually dominated the zooplankton, which ranged from 23 to 7970 individualsm−3. Abundances were always higher on the inner shelf regardless of the season of the year. Abundance on the mid-shelf peaked following the onset of the intrusion of the nutrient-rich oceanic SACW in the lower euphotic zone and the enhancement of the DCM. A 6-step circulation model of diatoms coupled with shelf hydrodynamics is proposed as the main mechanism of retention of diatoms in the shelf system. The model suggests that diatoms resuspended in the nearshore are transported offshore by Ekman forces toward oligotrophic waters, where they sink faster due to poor nutrient conditions. Sinking cells find better nutrient conditions in the pycnocline/nutricline layers, become shade-adapted and increase their buoyancy, contributing to the formation of the DCM. Resting cells sinking out of the euphotic zone reach near-bottom layers or the sediments, from where they are carried back onshore by oceanic intrusions of the SACW. We suggest how this hydrodynamic circulation pattern of diatoms may take place in other subtropical shelf systems dominated by western boundary currents.

Spatial distribution of cephalopod paralarvae in San José Gulf (Northern Patagonia, Argentina): The role of tidal circulation in larval dispersal

The spatial distribution of cephalopod paralarvae was studied in waters of San José Gulf (SJG), a shallow basin connected to a larger gulf (San Matías, SMG) through a narrow mouth located on its northwestern margin. The gulf is characterized by a remarkable tidal circulation pattern providing contrasting hydrodynamic conditions between the western and eastern domains. Zooplankton net tows (n=104) and depth-temperature profiling (n=70) were conducted on a monthly basis at fixed stations forming a regular grid from October (mid spring) 2011 to March (late summer) 2012. Temperature-depth profiles showed that while the western domain seawater column remains well mixed by tidal currents during the whole period, stratification develops from November to March on the eastern domain. Positive zooplankton net tows were sporadic for early-life stages of Semirossia tenera (n=1) and Robsonella fontaniana (n=3), and more frequent for those of Doryteuthis sanpaulensis (n=9) and Illex argentinus (n=9). The latter were found almost exclusively in the western domain whereas those from D. sanpaulensis were mainly sampled in the eastern domain. Low abundance of I. argentinus paralarvae in the eastern domain suggests that buoyant egg masses of this squid are not released in SJG; instead they, or the hatching paralarvae emerging from them, could be sequentially advected from and expelled to SMG by tidal currents. On the other hand, the spatial distribution of D. sanpaulensis paralarvae suggests that those hatching on the shallow marginal bottoms of the eastern domain are retained in this region while those hatching at the western domain are flushed out to SMG by tidal currents.