Coastal Flow Research Articles

Comparison of methods measuring electrical conductivity in coastal aquifers

Coastal aquifers, the transition zone between freshwater and saltwater, show large salinity contrasts in the subsurface. Salinity is a key parameter to understand coastal groundwater flow dynamics and consequently also geochemical and microbial processes. For mapping porewater salinity, a variety of methods exists, mainly using electrical conductivity as a proxy. We investigate methods including hydrological/geochemical (well sampling, fluid logger) as well as geophysical method (direct push, geoelectrics) utilising measurements near the high-water line of a high-energy beach at the North Sea island of Spiekeroog. We compare the methods, discuss their benefits and limitations and assess their spatial and temporal resolution. One key to enable a comparison is the estimation of formation factors transforming bulk conductivity measured by geophysical tools in to fluid conductivities obtained from direct measurements. We derive depth-dependent formation factors derived from time-series measurements of fluid loggers and a vertical electrode installation. Using these formation factors, the vertical electrode chain proves to provide reliable salinities at high spatial and temporal dimension. Direct-push profiling data provide the highest vertical resolution. However, a careful calibration is needed to allow for salinity quantification. On the other hand, electrical resistivity tomography (ERT) exhibits the lowest spatial resolution, but can image two-dimensional salinity distributions. We found ERT to fit very well to all other methods, but the data analysis should be aimed at salinities instead of bulk conductivities, i.e. including formation factors and temperature models into the inversion process.

Turbulent models of shallow-water equations-based smoothed particle hydrodynamics

The depth-averaged models such as those based on the shallow water equations (SWEs) are commonly used to simulate the large-scale flows with engineering importance. The smoothed particle hydrodynamics (SPH) approach has been documented to solve the SWEs due to its mesh-free superiority in treating the free surfaces and wet-dry boundaries. However, nearly all SWE-SPH models were developed without a turbulent model, which seriously limited the model applications where the flows are complex and where the turbulent parameters are explicitly needed. For the first time, this paper includes a depth-averaged turbulent k̂-ε̂ model in the SWE-SPH solver, making the model more capable of treating the turbulent flows in the practical field. For comparison purpose, a sub-particle-scale turbulent model widely adopted in three-dimensional (3D) SPH was also included in the present SWE-SPH scheme. To evaluate the performance of the two proposed turbulent SWE-SPH models, various open channel flows of increasing complexity were simulated, and the SPH computations were compared with the reported data in the literature. Through the analysis of results for a rough riverbed, L-shaped and sudden expansion channels, it is demonstrated that the present turbulent SWE-SPH models are equipped with good robustness and accuracy in capturing the shallow water turbulent dynamics, with the potential to be used in practical river and coastal flows. In summary, there are two distinct novelties in the proposed work. First, the mesh-free numerical modeling technique SPH is used to solve the shallow water equations, which enable the model to work in large engineering field through simple and effective tracking of free surfaces and wet-dry boundaries. Second, the proposed research expands the shallow water SPH modeling technique by including robust turbulence simulation capacity. The newly developed model can address more challenging engineering scenarios such as the sediment and pollutant transports when the flow turbulence plays an important role and where the turbulent parameters are explicitly required in the relevant transport equations.

Investigation of Coastal Winds and Turbulence Characteristics Using Doppler Lidar

AbstractSea ports play a major role in the transport of goods worldwide, and knowledge of wind characteristics in these areas is vital to maintaining safety. However, coastal wind flow can be highly complex and turbulent, necessitating additional analysis. A Doppler lidar providing continuous wind profiles is deployed in the Port of Genoa, Italy, to characterize the mean wind velocity and turbulence properties within the coastal surface layer (40–250 m above ground level). Weather conditions, reanalysis data, and transient wind profiles are combined to analyze wind field characteristics on a day which experienced a thunderstorm. We also utilize a method to identify and categorize sources of turbulence through analysis of lidar derived quantities such as wind shear, turbulent kinetic energy, and vertical skewness. Seasonal variations in the wind properties are investigated by selecting data from June (summer) and December (winter). Differences are found in dominant wind direction and the associated frequency of convective mixing, with onshore winds most common in summer and offshore winds in winter. The measured lidar velocity is also compared against Monin–Obukhov similarity theory predictions, showing satisfactory agreement at low heights but struggling to reproduce observations of the stable atmospheric conditions present during winter.

Spatiotemporal variations in the grain size distribution in the water column and sediments from the Yellow River Delta to distal areas under coastal currents

The differentiation of sediment grain size from large river deltas to distal areas in a coastal flow system and its evolution are vital because they greatly contribute to matter transport, pollution accumulation, and carbon cycling on the inner shelf. Here, the Yellow River sedimentary system in the adjacent seas is studied, including the proximal delta of the Yellow River and the distal mud patch. The grain size distributions of the suspended particulate matter (SPM), surface sediments, and core sediments in the Shandong Peninsula Coastal Current (SPCC) system were integrated and analyzed. The results show that apparent variations in the grain size distribution exist in the SPM and sediments in the SPCC system. The grain size distribution of the SPM near the proximal delta of the Yellow River is multimodal and variable with water depth, whereas that in the distal mud area is typically unimodal. The coarse-grained endmember of suspended sediments is restricted in the proximal area by ocean fronts under fair weather conditions in both summer and winter and is only transported to the distal mud area under strengthened coastal currents in winter. In contrast, fine-grained endmembers can be transported far away under tidal currents and coastal currents year-round. The temporal grain size variation near the proximal delta is also significantly affected by historical shifts in the Yellow River mouth, while the strength of coastal currents associated with the East Asian Winter Monsoon (EAWM) controls the grain size distribution in the distal mud area. The roles of river behaviors, ocean fronts, tides, and winds are all highlighted in the control of grain size differentiation. These results potentially have significance for understanding sediment dynamics and mass transport processes in similar coastal current systems involving large rivers worldwide.

Sequencing seabed morphology through bathymetric profiling on Brebes coastal area

Abstract The sedimentation process encompasses both morpho-dynamic and hydrodynamic aspects, but hydrodynamic-related sedimentation studies have received greater attention. Our data mining shows that total publication on the hydrodynamic aspect 2% greater than the morphodynamic aspect, indicating a bias towards this aspect in sedimentation research. Morphosedimentary studies offer an alternative approach to conducting sedimentation research with a focus on the morpho-dynamic aspect. Brebes Regency, located on the north coast of Central Java, experiences significant accretion, making it an ideal location for this study. The overarching objective of this research is to analyze bed load flow patterns within the nearshore zone of Brebes Regency, Central Java, Indonesia, by considering morphosedimentary features. To achieve this, we utilized bathymetry data from sources such as GEBCO and National DEM Data (BATNAS), alongside field validation. Initial desk analysis revealed a depression in the western part of the Brebes coastal area, characterized by a depth of 15 meters, situated within the middle of the upper slope morphosedimentary region. To validate this finding, we overlaid the data with BATNAS. Subsequent analysis indicated that the depression had flattened out over time. Instead, the final results indicate that bed load flows originate in the west bay of the Brebes coastal area and flow northeastward.

Quantifying the role of submesoscale Lagrangian transport features in the concentration of phytoplankton in a coastal system

Abstract Food resources in the ocean are often found in low densities, and need to be concentrated for efficient consumption. This is done in part by oceanographic features transporting and locally concentrating plankton, creating a highly patchy resource. Lagrangian approaches applied to ocean dynamics can identify these transport features, linking Lagrangian transport and spatial ecology. However, little is known about how Lagrangian approaches perform in ageostrophic coastal flows. This study evaluates two Lagrangian Coherent Structure metrics against the distribution of phytoplankton; Finite Time Lyapunov Exponents (FTLE) and Relative Particle Density (RPD). FTLE and RPD are applied to High Frequency Radar (HFR) observed surface currents within a biological hotspot, Palmer Deep Canyon Antarctica. FTLE and RPD identify different transport patterns, with RPD mapping single particle trajectories and FTLE tracking relative motion of paired particles. Simultaneous measurements of circulation and phytoplankton were gathered through the integration of vessel and autonomous glider surveys within the HFR footprint. Results show FTLE better defined phytoplankton patches compared to RPD, with the strongest associations occurring in stratified conditions, suggesting that phytoplankton congregate along FTLE ridges in coastal flows. This quantified relationship between circulation and phytoplankton patches emphasizes the role of transport in the maintenance of coastal food webs.

Spatiotemporal variation, composition, and implications for transport flux of nitrogen in Leizhou Peninsula coastal water, China

Nitrogen, as the main bioactive element, plays an important role in biological productivity, ecosystem function, and biogeochemical processes in marine environment. In this study, seawater samples collected from China’s Leizhou Peninsula coastal water (LZPCW) during dry, normal, and wet seasons in 2018 were explored to reveal the spatiotemporal variation, composition, and transport flux of dissolved inorganic nitrogen (DIN) linked to hydrographic condition. DIN concentration and speciation showed significantly seasonal variation (P < 0.01), and the concentration of DIN species was significantly higher in dry season than other seasons. The annual mean DIN concentration was 8.01 ± 5.79 μmol L−1. In addition, the N–NO2−, N–NO3− and N–NH4+ were significantly different in the DIN bulk in different seasons. The largest fraction of DIN was N–NO3−, followed by N–NH4+, the lowest was N–NO2−, comprising up to 67.92 ± 23.20%, 23.90 ± 23.19% and 8.18 ± 8.19%, respectively. Besides, the Beibu Gulf was subjected to 7.28 × 1010 mol DIN annual flux through the Qiongzhou Strait. The annual transport fluxes of N–NO2−, N–NO3−, and N–NH4+ accounted for 6.43%, 77.20% and 16.36%, respectively. The DIN concentration and coastal water flow led to the largest DIN flux transport in dry season. This study revealed that the coastal ocean currents, river plumes and human activities jointly drove the dynamic variations of N species in LZPCW. It provides a baseline data for studying the spatiotemporal effects of hydrographic condition on nitrogen distribution and transport flux in the LZPCW, which is implications for understanding nutrients dynamics and coastal water quality management in future.

The study of coastal flows based on lattice Boltzmann method: application Oualidia lagoon

The study of coastal flows based on lattice Boltzmann method: application Oualidia lagoon

Toward high-fidelity Numerical Wave Tank development: Scale resolving Partially-Averaged Navier–Stokes simulations of dam-break flow

Numerical Wave Tanks (NWTs) based on Navier–Stokes equations are emerging as valuable tools for simulating various ocean and coastal engineering flows. By capturing essential hydrodynamic non-linearities, including turbulent processes, these Navier–Stokes based NWTs can potentially provide high-accuracy data to complement traditional experimental wave basins for design and development applications. Many NWT approaches currently use the RANS (Reynolds Averaged Navier–Stokes) method. For many coastal resiliency and wave-energy converter applications, a higher fidelity turbulence treatment may be needed. In this work, we explore the applicability of the scale-resolving Partially-Averaged Navier–Stokes (PANS) technique for NWT computation. The PANS model is employed to study the dam-break benchmark case which is an important benchmark case for seawall and wave energy converter hydrodynamics analysis. Computations using RANS are also provided as a reference for accuracy and computational effort. The objectives are to: (i) investigate the effect of enhancing turbulence scale resolution on the pressure field, wave elevation and three-dimensional effects within the tank; and (ii) examine the influence of initial kinetic energy and grid resolution on the results. It is shown that, the early transient behavior is reasonably insensitive to scale resolution or initial turbulence level. Indeed, RANS and PANS of different scale resolutions yield similar results in the early stages as the flow physics is dominated by quasi-linear flow processes. The differences between RANS and PANS appear at later times. The so-called second pressure peak, standing wave amplitude and three-dimensional effects are better captured with increasing scale resolution for the same grid resolution. Overall, the results indicate that PANS is a viable model for NWT applications, with more detail being captured at a similar computational cost compared to RANS.

A flexible z-layers approach for the accurate representation of free surface flows in a coastal ocean model (SHYFEM v. 7_5_71)

Abstract. We propose a discrete multilayer shallow water model based on z-layers, which, thanks to the insertion and removal of surface layers, can deal with an arbitrarily large tidal oscillation independently of the vertical resolution. The algorithm is based on a classical two-step procedure used in numerical simulations with moving boundaries (grid movement followed by a grid topology change, that is, the insertion/removal of surface layers), which avoids the appearance of surface layers with very small or negative thickness. With ad hoc treatment of advection terms at nonconformal edges that may appear owing to insertion/removal operations, mass conservation and the compatibility of the tracer equation with the continuity equation are preserved at a discrete level. This algorithm called z-surface-adaptive, can be reduced, as a particular case when all layers are moving, to the z-star coordinate. With idealized and realistic numerical experiments, we compare the z-surface-adaptive against z-star and we show that it can be used to simulate coastal flows effectively.

Interaction among local flows, UHI, coastal winds, and complex terrain: Effect on urban-scale temperature and building energy consumption during heatwaves

Extreme heat aggravates thermal stress and electricity shortage in urban areas. This study investigates the (circulating) winds in Hong Kong during a heatwave. Unprecedentedly, the collective effect of coastal winds, complex terrain, and local flows on urban temperatures and air-conditioning load intensity (ACLI) is examined using the mesoscale Weather Research and Forecasting (WRF) model. Three representative wind patterns, including urban-accelerated channel wind, channel-wind-induced heat advection, and urban-mountain-stagnated sea-breeze, are analyzed. Our results show that the mountain blockage in foothill areas would increase 2-m temperatures (T2) and ACLI by 1 °C to 2 °C and 5 W/m2, respectively. ACLI in compact high-rise areas (LCZ 1) is most sensitive to extreme heat. Moreover, the urban heat island (UHI) downstream is crucial that would accelerate channel flows by 1.66 m/sec (50.26 %). On the other hand, terrain-induced channel winds augment heat advection, increasing downstream T2 (0.7 °C) and ACLI (2.62 W/m2). UHI-induced local flows interact with hilly slopes, stagnating the sea breeze on mountain leeward side. Subsequently, the winds would be slowed down by 0.81 m/sec while the temperature T2 would be increased by 0.9 °C in downstream urban areas. Eventually, the daytime ACLI could be raised as much as 6.41 W/m2.

A fully Eulerian two-layer model for the simulation of oil spills spreading over coastal flows

Nowadays, the vast majority of coastal oil spill simulation models are based on Lagrangian methods focused on particle tracking algorithms to represent the oil slick fate. In this work, a fully Eulerian numerical model for the simulation of such environmentally significant disaster is implemented by means of a two-dimensional two-layer shallow water model. A very thin oil layer over a thicker water layer is considered in order to neglect the pressure term that the oil layer exerts over the water. Friction terms between layers are responsible for the layers coupling so that the oil layer flows over a moving water volume. To complete this dynamic model, the temperature transport and evolution under heat exchange for the oil upper layer is considered and the weathering process of evaporation is included. The numerical solution adopted is based on a finite volume upwind scheme with a Roe solver for both oil and water layers. Special care has been taken on the numerical treatment of the two-layer wet-dry boundaries (oil–water–land) and friction terms, since the objective of the model is to compute the oil slick front advancing near the coast.

Comprehensive modeling from watersheds to a bay and its validation with radar, drifters, and MVP methods

The validation of numerical simulations by adjusting parameters is essential to improve accuracy and reliability. Therefore, various measured data of flow characteristics are required to evaluate the reproducibility of the models for watershed, river channel, and coastal flows, particularly for estuaries, where complex physical phenomena occur owing to the diverse external forces and their interactions of land and ocean processes. This study coupled a hydrodynamic model with watershed, river current, tide, and wave models to reproduce freshwater flows, coastal currents, and overall circulations in a small bay where the river and bay meet, considering diverse external forcings from the land, ocean, and atmosphere. Comprehensive validations of simulations from the watershed to the open sea are presented. Data were collected by surveying using the Lagrangian and Eulerian ways to calibrate and validate the model results accurately and sampled at fixed points. The presented simulations are a well-validated example to reproduce the stages, discharges, and stratifications in the river channel and the waves, tides, surface currents, and circulation in the bay well, and the simulation results of this model were applied to investigate sediment transport in rivers and bays.

Cross-shelf transport off the northern Taiwan, East China Sea

Cross-shelf transport is an important material exchange process between the shelf seas and open seas. The distribution characteristics of phytoplankton, surface sediment particle size, minerals, etc., all indicate the possible existence of a cross-shelf transport conduit from the inner shelf to the outer shelf off northern Taiwan. This study confirmed cross-shelf transport off northern Taiwan based on remote sensing sea surface temperature (SST) data and heat flux data, which can be divided into two patterns: cold eddy and cold water tongue. Furthermore, combined with AVISO sea surface level data, CCMP wind field data, the dynamic formation factors of different morphological characteristics of cross-shelf transport are studied.Topographic changes mainly induce cross-shelf transport off northern Taiwan and occur at the curve of isobath to deep water. When there is a strong thermal front along the coast, cross-shelf transport is more likely to occur. Against the steady, strong northerly wind, the Zhe-Min coastal current's southward flow and Kuroshio's invasion strengthened the temperature front and facilitated cross-shelf transport. Typhoon strengthened cross-shelf transport over northern Taiwan after passing through the southern part of the study area. This research has important implications to find the channel and transporting pattern for material exchange between the East China Sea and the West Pacific, which will contribute to the study of ecological environmental protection and seabed muddy area formation.

Efficient representation of transient tidal overheight in a coastal groundwater flow model using a phase-averaged tidal boundary condition

Ocean tides cause water table overheight near the seaward boundary of coastal aquifers which can have a large impact on groundwater flows and saltwater intrusion. Despite this, regional-scale coastal groundwater flow models often neglect the effects of ocean tides or alternatively assume that the influences of ocean tides and sea level are constant over time. These simplifications are often required because simulation of the phase-resolved tidal signal at a coastal boundary is computationally demanding. Our objective was to derive a phase-averaged tidal boundary condition for application along gently sloping coastlines that enables simulation of real, complex tidal signals combined with sea-level changes due to meteorological effects. The boundary condition extends an existing analytical solution of tidal overheight by including an empirical correction function for conditions where the assumptions of the existing solution are violated. The correction function was developed by conducting a parametric study on an idealized two-dimensional cross-sectional coastal aquifer model and considering the effects of parameters including horizontal hydraulic conductivity, vertical anisotropy, specific yield, aquifer thickness, and beach slope. The performance of the new phase-averaged tidal boundary condition was assessed using a three-dimensional groundwater flow model of the island of Spiekeroog, Northwest Germany, which comprises complex coastal morphology with non-planar beach slopes. Simulations applying the new boundary condition were compared to simulations that adopted a phase-resolved tidal boundary condition and to observed groundwater levels. Accounting for time-varying changes in the tidal signal and sea level was found to be critical to simulate observed data and to adequately reproduce the transient tidal overheight simulated by the phase-resolved model. The performance of the new phase-averaged boundary condition in the regional-scale model varied depending on how the coastal morphology was represented in the boundary condition with local morphological features increasingly important for lower intertidal vertical infiltration capacity (low isotropic hydraulic conductivity or high vertical anisotropy) or specific yield. In conclusion, the new boundary condition presented overcomes current limitations in simulating transient tidal overheight in regional-scale groundwater models.

A sediment transport theory based on distortion-free-boundary nonhomogeneous fluid flows

Over the last 50 years several sediment transport models in coastal environments based on Shallow Water(SW) type models have been developed in the literature. The water flow over an abrupt moving topography quickly spatially variable becomes accelerated and strongly varied arising the turbulence (distortion). The acceleration and strong variation of the flow facilitate the transport of a large quantity of sediments present at the bottom while modifying it. The mathematical models based on SW type models widely used to describe the sediment transport phenomena do not account the distortion effects. Indeed, it is well-known that the SW models are derived from first order approximation of long wave theory. The acceleration and strong variation of the water flow near the bottom is due to the distortion of the horizontal velocity profile along the vertical direction. One can regard distortion as a combination of strain and rotation. The effect of the rotational component is to weaken the effect of the strain somewhat. In this work, we put in place a king theory of sediment transport derived from the second order approximation of long wave theory that can describe sediment transport processes in distortion-free-boundary nonhomogeneous fluid flows. The derived model accounts the distortion (fluctuation with great correlation lengths) that creates the turbulence. Moreover, the model differentiates the fluid velocity from sediment velocity (phase-lag) near the sediment bed. The proposed theory significantly reduces the modeling errors observed in several sediment transport models based on nonhomogeneous shallow water equations and has a great potential to increase the predictive power of sediment transport models in rivers, lakes, coastal flows, ocean basins and so on. The proposed theory improves several existing sediment transport theories recently developed in the literature and can be apply with some degree confidence.

LABORATARY STUDY OF THE VERTICAL RETREATING SAND WALL OBSERVED IN COASTAL FLOW SLIDES

Coastal flow slides have been reported around the world (Mastbergen et al., 2019; Nédélec et al., 2022), often at over-steepened banks subject to strong tidal flows, pose threat to coastal communities and infrastructure (Lulla, 2017). With sea level rise caused by climate change, these flow slides are expected to occur more frequently in more sites worldwide. Amity Point Beach, North Stradbroke Island (27o 23’ 35’’S, 153o26’23’’E), about 40 km from Brisbane, Australia, have experienced regular coastal flow slides for more than 40 years (Eberhardt, 1978). Together with observations at Amity Point beach field site, small-scale flow slides are simulated in laboratory by tilting metal box filled with sand and fluid.

THE INFLUENCE OF THE ANTHROPOGENIC FACTOR ON THE BLACK SEA COAST WITHIN THE ODESSA REGION

Problem Statement &amp; Purpose. The city of Odessa is the center of a large industrial and port agglomeration on the northwestern coast of the Black Sea between Cape Karabush and Sanzheyskiy Cape. Until the foundation of the seaport and the city, the Black Sea shores and estuaries almost always existed in a natural state, except for local small areas located in temporary fishing, military, wandering sites. But from the end of the 18th century, the first buildings and transformations of natural slopes began, which began to significantly change the surrounding nature of the coast and coastal land, because «the history of the development of Odessa is the history of the fight against abrasion landslides». These and many other authors (A. M. Drannikov, G. M. Zub, E. E. Kitran, N. A. Khrennikov, I. Ya. Yatsko and others) testified about the general appearance, morphology and dynamics of natural coastal landslides in the period up to the end of the 40s of the XX century. It is the consequences ofanthropogenic influence and their consideration, analysis and current situation on the Odessa coast of the Black Sea that is the purpose of this work. Data &amp; Methods. The actual materials of this work were obtained by the authors over the course of decades in the area between Capes Lanzheron and Bugovo on the Odessa coast. Buildings to protect the coast from destruction were instrumentally studied. Two leading groups of coastal marine research were used as the main ones: route-expeditionary and stationary. Their office processing included the use of cartographic, graphical modeling, mathematical statistics, geographical comparison, water and sieve analysis, geomorphological leveling, etc. For comparisons, the materials of Yu. D. Shuisky, I. P. Zelinskiy, D. Ya. Bertman, A. R. Shuvalov, A. V. Kisselis. Results. The increase in anthropogenic pressure on the natural system of the Black Sea coast within the Odessa area forced us to carry out additional studies of the Odessa coastal defense complex. It is located between the Langeron Cape in the north and the southern flank of Bolshoy Fontan Cape, for about 12.5 km. The named complex changed the coast very much, there was a strong influence of anthropomorphogenesis. At the same time, designers and builders were guided by a more perfect natural scheme of sediment distribution in the sphere of action of the North-West along the coastal sediment flow. The artificial transformation of the Odessa coast has led to the emergence of several types of anthropogenic landforms instead of natural ones. Coastal protection and other structures are represented by surface, intra-slope and underwater, longitudinal and transverse, positive and negative, sedimentary, concrete, reinforced concrete, metal, high, low for various purposes, etc. They correspond to a special classification. The effectiveness of the introduction of hydraulic structures is ensured by their functionality. The main property is the ability to extinguish and disperse the energy of sea waves with a loss of 10 to 60%. The structures lead to the loading of the shear tongue, the diversion of groundwater, the prevention of abrasion of the subslopes from storm impact, and they have a recreational and ecological purpose. Wave action on artificial sandy beaches, on their significant vertical and horizontal deformations, is accompanied by sediment loss. Wave processing of sediments provides the development of an equilibrium profile that occurs in different stages: initial transformation of the shape, formation of sand sizes, very fast transformation during the first 1–3 years and slow changes during subsequent repair backfilling. At the same time, the range of deformations is large, very close to natural, despite the surrounding structures.

Application of Newton iteration to the numerical solution of variable-density groundwater flow in saturated-unsaturated coastal zones

When addressing the question of variable saturation and density groundwater flow in coastal zones, the highly nonlinear system of coupled water-salt equations may deserve more attention. The classical Picard scheme is associated with slow calculation speeds and low precision, which hardly meet the actual needs of users. Here, we developed a new numerical solution for coastal groundwater flow issues based on the Newton scheme and compared the advantages and disadvantages of different numerical methods by analyzing the cases of seawater intrusion. The simulation results indicated that the variable-density effect significantly extends the computation time of the model, but the Newton scheme still has the advantages of computational speed and better convergence compared with the Picard scheme, especially in conditions involving high-frequency and large-amplitude tidal fluctuations, steep aquifer slopes, and a coarse grid. Furthermore, the Newton-Picard method, based on the Newton and Picard schemes, improves the robustness of the Newton solution and optimizes the convergence of the Picard solution. This study has revealed the computational characteristics of the Newton scheme in addressing the issues of coastal variable saturation and density groundwater flow, providing new ideas and insights for numerical solutions to coastal groundwater flow problems.

ОЦЕНКА ВЛИЯНИЯ КЛИМАТИЧЕСКИХ ФАКТОРОВ НА МЕЖГОДОВУЮ ИЗМЕНЧИВОСТЬ ТЕМПЕРАТУРЫ И СОЛЕНОСТИ ВОДЫ В БАРЕНЦЕВОМ МОРЕ

Based on shipboard measurements taken in 1984-2017, the multiyear variations in the surface water temperature and salinity in the Barents Sea during the spring-summer period are investigated. A regression analysis has found increasing trends for both analyzed parameters, indicating warming processes in the Arctic regions. Application of linear and nonlinear models revealed significant influence of the global atmospheric circulation, the hydrological conditions at the Kola Meridian secular section, and the sea ice cover area on the long-term dynamics of surface temperature and salinity in the Barents Sea. The highest measured values were associated with a positive mode of the North Atlantic Oscillation indices, high water temperatures in the coastal flow of the Murmansk Current, and low sea ice concentrations. Results of the study can be used for further monitoring of the Barents Sea oceanography during the period of global climatic changes.