Regime of Low-Frequency Wave Motion in the Coastal Zone of the Northwestern Caspian Sea

Regime characteristics of infragravitational and wind-induced waves for the northwestern Caspian Sea are given. The role of infragravitational waves in the dynamics of the northern Caspian coastal zone is determined based on empiric regional relationships, used to improve the conventional methods, and wind wave calculations.     

A Nonlinear Model of Level Variations in the Caspian Sea

A new thermophysical mechanism of the Caspian Sea level variations is proposed. The mechanism incorporates the effect exerted on the dynamics of the water budget of the Caspian Sea by the nonlinear dependence of the evaporation rate on the moistening of the basin.     

Assessment of the Effect of Hydrometeorological Factors on the Regime of Syamozero Level Variations at Drainage Amelioration

Materials of the many-year stationary observations and investigations were used to assess the effect of the forest and agricultural amelioration on the regime of water level variations in Syamozero Lake. It was shown that under the conditions of Karelia, the drainage of up to 10% of the catchment area leads to an insignificant decrease in the annual, seasonal, and maximal spring-and-summer values of the lake level and a slight change in its minimal summer-and-autumn values. Multiple-factor equations, reliable enough for the prediction of the regime of the lake level, have been developed.     

Monitoring Sea Level in the Coastal Zone with Satellite Altimetry and Tide Gauges

We examine the issue of sustained measurements of sea level in the coastal zone, first by summarizing the long-term observations from tide gauges, then showing how those are now complemented by improved satellite altimetry products in the coastal ocean. We present some of the progresses in coastal altimetry, both from dedicated reprocessing of the radar waveforms and from the development of improved corrections for the atmospheric effects. This trend towards better altimetric data at the coast comes also from technological innovations such as Ka-band altimetry and SAR altimetry, and we discuss the advantages deriving from the AltiKa Ka-band altimeter and the SIRAL altimeter on CryoSat-2 that can be operated in SAR mode. A case study along the UK coast demonstrates the good agreement between coastal altimetry and tide gauge observations, with root mean square differences as low as 4 cm at many stations, allowing the characterization of the annual cycle of sea level along the UK coasts. Finally, we examine the evolution of the sea level trend from the open to the coastal ocean along the western coast of Africa, comparing standard and coastally improved products. Different products give different sea level trend profiles, so the recommendation is that additional efforts are needed to study sea level trends in the coastal zone from past and present satellite altimeters. Further improvements are expected from more refined processing and screening of data, but in particular from the constant improvements in the geophysical corrections.     

Different-Scale Variations in the Abundance and Species Diversity of Metazoan Microzooplankton in the Coastal Zone of the Black Sea

Water Resources - The short-term, seasonal, and interannual variations in the abundance and species composition of the Black Sea metazoan microzooplankton have been analyzed at the open coastal...     

Dependence of Groundwater Flow Direction on Variations in Its Salinity

The direction of motion of groundwater with a varying salinity is shown to depend on the spatial position of equal-salinity surfaces (planes), along the slopes of which groundwater motion takes place. The equations required for the solution of such problems are given. The procedure is exemplified by estimating the direction of groundwater motion in the western part of the Moscow Artesian Basin.     

Natural Tritium as an Indicator of Changes in the Vertical Structure of Caspian Sea Water Mass with Sea Level Variations

Analysis of changes in the vertical distribution of tritium in the Caspian Sea water mass in 1994–1996 led to a conclusion that the sea level fall that started in 1996 was accompanied by a rearrangement of the water mass steady hydrological structure characteristic of the high sea-level stand.__________Translated from Vodnye Resursy, Vol. 32, No. 4, 2005, pp. 406–409.Original Russian Text Copyright © 2005 by Brezgunov, Ferronskii.     

Probabilistic Regularities in Setup Variations in the Level of a Large Inland Water Body: Case Study of the Caspian Sea

The results of probabilistic analysis of data on setup level variations collected during long-term observations at all gages along the Caspian Sea coast are discussed. A procedure for evaluating low-probability sea level extremes is proposed. Estimates are given for the probabilities of outstanding setups in the Caspian Sea and the Sea of Azov.     

Seasonal Variations of Water Quality in the Vostok Bay,Peter the Great Gulf,the Sea of Japan

Water Resources - Studies of 2015 were used to characterize water in Vostok Bay (Peter the Great Gulf, the Sea of Japan) in terms of phosphate concentration, biochemical oxygen demand, and pH. The...     

The Sources of Uncertainty in Forecasting Caspian Sea Level and Estimating the Inundation Risk of Coastal Areas

Stochastic variations in the climate and hydrological regime, both natural and anthropogenic, are the main cause of uncertainty in long-term hydrological forecasts and hence increase the estimated risk of economic activity in the coastal zone of internal seas. Some sources of uncertainty, which appear during the hydrological analysis, are considered with the purpose to assess this risk. Digital relief models were used to determine the morphological characteristics (as functions of the sea level) and assess their contribution to variations in the level regime. To take into account the sample uncertainty in the parameter estimates of stochastic models of the “impellent” processes, it is proposed to use the existing methodology of probabilistic-deterministic prediction of water level variations in a closed water body in combination with the Bayesian approach.     

Effect of a Freshwater Layer Overlying Salt Water on the Regime of Replacement in Confined Coastal Aquifers

A mathematical model of fresh groundwater flow from a semi-infinite confined aquifer into a sea (pool, trench, and the like) filled with salt water and having a freshwater layer above its horizon. To study this problem a mixed boundary-value problem of the theory of analytical functions is formulated and solved with the use of the Polubarinova-Kochina method. The obtained exact analytical relationships and numerical calculations are used to perform a detailed hydrodynamic analysis of the effect of the freshwater layer and other physical parameters of the model on the character and the extent of displacement.     

Simulating Salinity Variations in the Gulf of Taganrog at Storm Surges

Water Resources - Observation data on salinity variations in the Gulf of Taganrog during storm surges are analyzed; a mathematical model of the transport of salt water masses is described in...     

Modeling Coastal Salinity in Quasi 2D and 3D Using a DUALEM‐421 and Inversion Software

Rising sea levels, owing to climate change, are a threat to fresh water coastal aquifers. This is because saline intrusions are caused by increases and intensification of medium‐large scale influences including sea level rise, wave climate, tidal cycles, and shifts in beach morphology. Methods are therefore required to understand the dynamics of these interactions. While traditional borehole and galvanic contact resistivity (GCR) techniques have been successful they are time‐consuming. Alternatively, frequency‐domain electromagnetic (FEM) induction is potentially useful as physical contact with the ground is not required. A DUALEM‐421 and EM4Soil inversion software package are used to develop a quasi two‐ (2D) and quasi three‐dimensional (3D) electromagnetic conductivity images (EMCI) across Long Reef Beach located north of Sydney Harbour, New South Wales, Australia. The quasi 2D models discern: the dry sand (<10 mS/m) associated with the incipient dune; sand with fresh water (10 to 20 mS/m); mixing of fresh and saline water (20 to 500 mS/m), and; saline sand of varying moisture (more than 500 mS/m). The quasi 3D EMCIs generated for low and high tides suggest that daily tidal cycles do not have a significant effect on local groundwater salinity. Instead, the saline intrusion is most likely influenced by medium‐large scale drivers including local wave climate and morphology along this wave‐dominated beach. Further research is required to elucidate the influence of spring‐neap tidal cycles, contrasting beach morphological states and sea level rise.     

Spatial and Temporal Variations in the Formation of the Kamennaya Steppe Water Regime

The processes of water regime formation in the catchment areas of deans in the Kamennaya Steppe are studied based on the data of many-year field experiments. Certain regular variations are recognized in the characteristics of the Kamennaya Steppe hydrological and ecological condition and their correlation with anthropogenic and climatic factors is established.     

Regularities in the Formation of Groundwater Level Regime in Moscow Region

The need to study and take into account regularities in the formation of groundwater regime and runoff, especially in the context of current climate changes, is demonstrated. Typical plots of groundwater level regime, the dependence of the amplitudes of their variations and the major statistical parameters on the depth to groundwater, and histograms of the occurrence time of extreme positions of its level are shown. Long-term trends in precipitation and groundwater levels are established and their statistical significance is estimated. The presence of cyclicity in groundwater level regime is analyzed.__________Translated from Vodnye Resursy, Vol. 32, No. 4, 2005, pp. 399–405.Original Russian Text Copyright © 2005 by Yakimova.     

Effect of Sea‐Level Rise on Salt Water Intrusion near a Coastal Well Field in Southeastern Florida

A variable‐density groundwater flow and dispersive solute transport model was developed for the shallow coastal aquifer system near a municipal supply well field in southeastern Florida. The model was calibrated for a 105‐year period (1900 to 2005). An analysis with the model suggests that well‐field withdrawals were the dominant cause of salt water intrusion near the well field, and that historical sea‐level rise, which is similar to lower‐bound projections of future sea‐level rise, exacerbated the extent of salt water intrusion. Average 2005 hydrologic conditions were used for 100‐year sensitivity simulations aimed at quantifying the effect of projected rises in sea level on fresh coastal groundwater resources near the well field. Use of average 2005 hydrologic conditions and a constant sea level result in total dissolved solids (TDS) concentration of the well field exceeding drinking water standards after 70 years. When sea‐level rise is included in the simulations, drinking water standards are exceeded 10 to 21 years earlier, depending on the specified rate of sea‐level rise.     

Impact of Sea-Level Rise on Sea Water Intrusion in Coastal Aquifers

Despite its purported importance, previous studies of the influence of sea-level rise on coastal aquifers have focused on specific sites, and a generalized systematic analysis of the general case of the sea water intrusion response to sea-level rise has not been reported. In this study, a simple conceptual framework is used to provide a first-order assessment of sea water intrusion changes in coastal unconfined aquifers in response to sea-level rise. Two conceptual models are tested: (1) flux-controlled systems, in which ground water discharge to the sea is persistent despite changes in sea level, and (2) head-controlled systems, whereby ground water abstractions or surface features maintain the head condition in the aquifer despite sea-level changes. The conceptualization assumes steady-state conditions, a sharp interface sea water-fresh water transition zone, homogeneous and isotropic aquifer properties, and constant recharge. In the case of constant flux conditions, the upper limit for sea water intrusion due to sea-level rise (up to 1.5 m is tested) is no greater than 50 m for typical values of recharge, hydraulic conductivity, and aquifer depth. This is in striking contrast to the constant head cases, in which the magnitude of salt water toe migration is on the order of hundreds of meters to several kilometers for the same sea-level rise. This study has highlighted the importance of inland boundary conditions on the sea-level rise impact. It identifies combinations of hydrogeologic parameters that control whether large or small salt water toe migration will occur for any given change in a hydrogeologic variable.     

Mechanisms controlling the air–sea flux in the North Sea

The mechanisms driving the air–sea exchange of carbon dioxide (CO₂) in the North Sea are investigated using the three-dimensional coupled physical–biogeochemical model ECOHAM (ECOlogical-model, HAMburg). We validate our simulations using field data for the years 2001–2002 and identify the controls of the air–sea CO₂ flux for two locations representative for the North Sea's biogeochemical provinces. In the seasonally stratified northern region, net CO₂ uptake is high () due to high net community production (NCP) in the surface water. Overflow production releasing semi-labile dissolved organic carbon needs to be considered for a realistic simulation of the low dissolved inorganic carbon (DIC) concentrations observed during summer. This biologically driven carbon drawdown outcompetes the temperature-driven rise in CO₂ partial pressure (pCO₂) during the productive season. In contrast, the permanently mixed southern region is a weak net CO₂ source (). NCP is generally low except for the spring bloom because remineralization parallels primary production. Here, the pCO₂ appears to be controlled by temperature.     

Seasonal variability of tides in the deep northern South China Sea

Tides are the major energy source for ocean mixing, regulating the variation of oceanic circulation and sediment transport in the deep sea. Here twenty months of high-resolution current profiles, which were observed via a mooring system at a water depth of 2100 m in the northern South China Sea(SCS), are used to investigate seasonal variability in deep-sea tides.Spectral analysis shows that tides in this region are dominated by diurnal tide, and both diurnal and semidiurnal tide are vertical mode-1 dominant. Baroclinic diurnal tidal current exhibits pronounced seasonal variability, showing its kinetic energy was the strongest in summer, and the maximum depth-averaged value was up to 86.7 cm~2 s~(-2), which was about 1.5 times of that in winter and twice that in spring and autumn. In contrast, baroclinic semidiurnal tide displays no evident seasonal variability. Such seasonal variability in baroclinic tide was mainly modulated by the barotropic forcing from the Luzon Strait. On the other hand,two anticyclonic eddies and one cyclonic eddy, which originated off southwestern Taiwan in winter, crossed the mooring system.The cyclonic eddy had weak impact on current velocity in the deep sea, but the two deep-reaching anticyclonic eddies enhanced the current velocity through the full-water column by inducing strong subinertial flows. Consequently, the kinetic energy of tides was strengthened and the incoherent variance of baroclinic diurnal tide increased in winter, which contributed ～85% of the variability in diurnal tide. Meanwhile, the velocity of baroclinic diurnal tide was reduced in winter, which was attributed to the weakened stratification induced by the passage of anticyclonic eddies in the deep sea. The seasonal variability of tides in the deep northern SCS can provide a dynamic mechanism for interpreting sediment transport processes in the deep sea on different time scales.