V. G. Bondur

Studies of hydrophysical processes during monitoring of the anthropogenic impact on coastal basins using the example of Mamala Bay of Oahu Island in Hawaii

This paper presents the main results of processing the data obtained in the study of hydrophysical processes during multidisciplinary monitoring of the anthropogenic impact on the coastal basin of Mamala Bay (Oahu Island, Hawaii). The results of the hydrophysical measurements carried out in August–September of 2002–2004 using stationary moorings and dropped and towed ship sensors were analyzed as the initial data. On the basis of these measurements, spatiotemporal, statistical, and spectral characteristics of different hydrophysical parameters of the marine envrionement in the basin of Mamala Bay were calculated, including three-dimensional components of the velocity vectors, the spectra of different components of velocities, the spectra of temperature fluctuations, and the characteristics of internal waves. The variability of the temperature fields and the correlation of the tidal phenomena with the temperature measurements and fluctuations caused by internal waves were analyzed. The materials and methods of the oceanographic studies and the results of the analysis of the meteorological and hydrological conditions are presented. The results obtained are used for a multidisciplinary analysis of the satellite and sea truth data.

Surface manifestations of internal waves investigated by a subsurface buoyant Jet: 1. The mechanism of internal-wave generation

In a large test reservoir with artificial temperature stratification at the Institute of Applied Physics, Russian Academy of Sciences, we have performed a major laboratory simulation of the nonstationary dynamics of buoyant turbulent jets generated by wastewater flows from underwater collector diffusers. The interaction of buoyant jets with the pycnocline leads to an active generation of internal waves. An analysis of the dependence of wave amplitude on the control parameter proportional to the rate of liquid flow from the collector diffuser has indicated that this dependence is adequately described by a function that is characteristic for the presence in the Hopf bifurcation system, which occurs for a soft actuation mode of self-oscillations of the globally instable mode. To check the conditions for the actuation of the globally instable mode, we have performed an auxiliary experiment in a small reservoir with a salt stratification formulated similar to the experiment in the big reservoir. Using the particle image velocimetry (PIV) method, we have measured the velocity field in the buoyant jet and constructed the profiles of transverse velocity in several sections. When the jet approaches the pycnocline, a counterflow is generated at the edges. A stability analysis for the resulting profiles of flow velocities performed by the method of normal modes has revealed that, for the jet portions with counterflow, the condition of absolute instability by the Briggs criterion for axisymmetric jet oscillations is satisfied, which testifies to the fact that the globally instable mode is actuated. The estimates for oscillation frequencies of the globally instable mode are well consistent quantitatively with the measured spectrum of jet oscillations.

Mathematical modeling of turbulent jets of deep-water sewage discharge into coastal basins

The basic properties of the dynamic model of a turbulent jet formed by a deep-water sewage discharge into the stratified environment of coastal regions are considered. The model developed was used to estimate the parameters of a floating-up jet of deep wastewater discharge from Sand Island into the basin of Mamala Bay (Hawaii) depending on the season and discharge operation mode. The estimates of the float-up depths of the jet and the initial dilution of the jet were estimated on the basis of model calculations using experimental data on the vertical profiles of the water temperature and salinity under the actual conditions of stratification in the study region. It is shown that the further propagation of the wastewater jet depends on tidal events and internal waves generated by tides. The appearance of turbulent jets at the sea surface was recorded. The model estimates of the parameters of the wastewater discharge were compared with the results of experimental measurements. Good agreement was found, which indicates that the physical mechanisms of the propagation of turbulent jets in a stratified medium are adequately described by the model.

Surface manifestations of internal waves investigated by a subsurface buoyant jet: 3. Surface manifestations of internal waves

In a large test reservoir at the Institute of Applied Physics, Russian Academy of Sciences, a series of experiments were performed to investigate the surface manifestations of internal waves radiated by a subsurface buoyant jet. The field of currents on the water surface of the reservoir was studied through the distribution of temperature with shallow thermocline. Using Particle Tracking Velocimetry (PTV), the velocity field of surface currents was measured. A theoretical model was developed to calculate the rates of disturbances on the surface. A comparison with experimental data indicated that the calculated data of the surface rate value are overestimated. This discrepancy was explained by the presence of a film of surface-active substances (SASs) with experimentally obtained parameters. Using scale modeling coefficients, we estimated the parameters of internal waves radiated by the subsurface wastewater system and the values of their surface manifestations in field conditions. We estimated the hydrodynamic contrasts in the field of surface waves, which can be caused by these inhomogeneous currents on the surface. For a wind velocity of 5 m/s, the magnitude of the contrast in the field of short waves can reach up to 10–25%, which is detected with confidence by remote-sensing methods.

The spectral characteristics and kinematics of short-period internal waves on the Hawaiian shelf

Based on the results of analyzing the characteristics of currents and temperature measured in the water space of the Mamala Bay (the Island of Oahu, Hawaii), we investigate the main properties of the field of short-period internal waves, which is very complex. We focus on analyzing the spectral characteristics and orbit parameters for waves with a period of 20 minutes. The results of investigations reveal two types of short-period internal waves for this area: intense and fast waves propagating predominantly toward the ocean and weaker and slower waves propagating mainly toward the coast. Suppositions are made on how these waves form: the strong and fast waves are likely to be caused by the decay of locally generated internal tides near the shelf edge, while the weak and slow and very short waves seem to result from the specific interaction between the pycnocline and strong tidal currents over a steep slope.

Anomalous variation of the ocean’s inertial oscillations at the Hawaii shelf

The data of acoustic Doppler profilometers placed at the edge of the steep shelf of Oahu Island, Hawaii, are analyzed for the currents. The specific character of inertial oscillations is revealed in the region: strong elongation of inertial orbits, a large amount of anomalous (cyclonic) current rotation, and sharp weakening in the divergence layer of the background (low-frequency) oscillations, the strong variation of which results in significant deviations of the effective inertial frequency from its local geographical value. It is suggested that cyclonic rotation of the inertial currents is related to a strong decrease in the effective oscillation frequency of the oceanic waves on the shelf.

Geomechanical models and ionospheric variations related to strongest earthquakes and weak influence of atmospheric pressure gradients

In this work, we developed computer models for the study regions to analyze the influence of the atmospheric pressure on the stressed state of the Earth’s crust. The distributions of distortions in the Earth’s crust to a depth of 100 km determined at four levels were used as the basis of the model: layer 1 0–20 km; layer 2 20–40 km; layer 3 40–60 km; and layer 4 60– 100 km. The distortions were obtained from the quantitative analysis of the distributions of fractures and lineaments in the studied regions on the basis of the method for processing satellite images suggested in [4]. Three-dimensional models of the distortions in the Earth’s crust including tectonic faults of different ranks were developed using this method. Distortion of the medium is characterized by the inhomogeneity function g ( x s ) , which ranges from 0 to 1. The g ( x s ) function was approximated with splines. All mechanical parameters were specified as

Characteristics of inertial oscillations according to the experimental measurements of currents on the Russian shelf of the Black Sea

The analysis of inertial oscillations on the Gelendzhik shelf of the Black Sea is presented. Spectral characteristics of the current fields are studied based on the measurements taken by the acoustic Doppler current profiler. Strong variability of the inertial oscillation hodographs at variations in the background shear current and diverse forms of inertial oscillations measured at a fixed point at various values of the shear current are revealed. The relation between the passage of the multidirectional jets and the trains of inertial oscillations inside the jets in the studied region are established.

Surface manifestations of internal waves investigated by a subsurface buoyant jet: Part 2. Internal wave field

In a large test reservoir with artificial temperature stratification at the Institute of Applied Physics, Russian Academy of Sciences, a major simulation of internal wave actuation by buoyant turbulent jets generated by wastewater flows from underwater collector diffusers in conditions of temperature stratification with deep and shallow thermocline has been performed. Using a modification of the particle tracing velocimetry (PTV) method in the stratification mode with shallow thermocline, the velocities of currents generated by internal waves at the surface of the water area are measured. A theoretical model is developed describing the fields of internal waves in the presence of jet stream. Dispersion relations and structures of lower (first and second) modes of internal waves in the stratified basin for different rates of liquid outflow from the collector model are obtained. The experimentally measured field of isothermal shifts with respect to the system of characteristic modes of internal waves is decomposed. A mixed regime of internal wave actuation with the simultaneous existence of the first and second modes is observed. The characteristics of perturbations in the liquid column and on its surface are compared. This analysis allows us to prove that the velocity fields on the surface are indeed surface manifestations of internal waves.

Connection between variations of the stress-strain state of the Earth’s crust and seismic activity: The example of Southern California

A three-dimensional geomechanical model of Southern California, including mountain relief, fault tectonics, and characteristic internal borders, such as the roof of the consolidated crust and Moho surface, was created. The initial stress state of the model is determined by the gravitational force and horizontal tectonic movement, established on basis of GPS observations. Monitoring of variations in the stress state of the Earth’s crust and lithosphere, which are generated by seismic processes, has shown that the model enables us to predict an increase of seismic activity in a region and to mark the places in which average earthquakes can occur in the following two weeks.