Oxana Kurkina

Structure of currents in the soliton of an internal wave

The characteristics of strongly nonlinear solitary internal waves (solitons), which are calculated by the nonlinear numerical model of the Massachusetts Institute of Technology (MITgcm), are studied. The model is verified and adopted on the basis of a laboratory experiment [6]. The field of the vertical and horizontal current in a wave is calculated. The formation of a reversible stream in the near-bottom layer is detected directly behind a soliton.

Kinematic parameters of internal waves of the second mode in the South China Sea

Spatial distributions of the main properties of the mode function and kinematic and non-linear parameters of internal waves of the second mode are derived for the South China Sea for typical summer conditions in July. The calculations are based on the Generalized Digital Environmental Model (GDEM) climatology of hydrological variables, from which the local stratification is evaluated. The focus is on the phase speed of long internal waves and the coefficients at the dispersive, quadratic and cubic terms of the weakly nonlinear Gardner model. Spatial distributions of these parameters, except for the coefficient at the cubic term, are qualitatively similar for waves of both modes. The dispersive term of Gardner’s equation and phase speed for internal waves of the second mode are about a quarter and half, respectively, of those for waves of the first mode. Similarly to the waves of the first mode, the coefficients at the quadratic and cubic terms of Gardner’s equation are practically independent of water depth. In contrast to the waves of the first mode, for waves of the second mode the quadratic term is mostly negative. The results can serve as a basis for expressing estimates of the expected parameters of internal waves for the South China Sea.

Numerical Modeling of the Internal Dispersive Shock Wave in the Ocean

Numerical modeling of dispersive shock waves called solibore in a stratified fluid is conducted. The theoretical model is based on extended version of the Korteweg-de Vries equation which takes into account the effects of cubic nonlinearity and Earth rotation. This model is now very popular in the physical oceanography. Initial conditions for simulations correspond to the real observed internal waves of shock-like shape in the Pechora Sea, the Arctic. It is shown that a sharp drop (like kink in the soliton theory) in the depth of the thermocline is conserved at a distance of one–three kilometers, and then it is transformed into dispersive shock waves (shock wave with undulations).

Exceedance frequency of appearance of extreme internal waves in the World Ocean

Statistical estimates of internal waves in different regions of the World Ocean are discussed. It is found that the observed exceedance probability of large-amplitude internal waves in most cases can be described by the Poisson law, which is one of the typical laws of extreme statistics. Detailed analysis of the statistical properties of internal waves in several regions of the World Ocean has been performed: tropical part of the Atlantic Ocean, northwestern shelf of Australia, the Mediterranean Sea near the Egyptian coast, and the Yellow Sea.

Numerical Modeling of Internal Wave Generation at High Latitudes

This contribution is focused on the semidiurnal internal tide in the Barents Sea generated north of the critical latitude (74.5° N). The study is based on the numerical modeling of internal wave generation and dynamics using of the Euler 2D equations for incompressible stratified fluid. The study site is located between Svalbard and the Franz-Victoria Trough. A Section 350 km long is chosen for the analysis in this basin. The bottom topography in the region is quite steep; four underwater hills with heights about 150–230 m over the background depth of about 350 m are located here. Calculations confirm the observation data in the vicinity of this region. Intense nonlinear internal waves with amplitudes up to 50 m and lengths of about 6–12 km are generated in this region of the Arctic.

Autonomous Mobile Robotic System for Coastal Monitoring and Forecasting Marine Natural Disasters

The paper presents the steps of creating an experimental prototype of an autonomous mobile robot for coastal monitoring and forecasting marine natural disasters. These systems of continuous coastal monitoring are the necessary link in predicting possibilities of developing the resources of the Russian shelf (areas of the Arctic and the Far East). One of the most difficult issues, associated with the creation of the described product, is to ensure the necessary level of mobility in inaccessible areas of coastal zones. This problem is solved by development of the chassis of modular design with the possibility to be reequipped with different types of movers (wheeled, tracked, rotary-screw), depending on operating conditions and the physical and mechanical characteristics of the ground surfaces. The presented robotic complex is also equipped with a set of measuring instruments (circular scanning radar, weather station, navigation system, lidars, video cameras), which allows to carry out comprehensive studies of any coastal zone and evaluate the risks and hazards for providing data for engineering simulation of hydraulic systems and structures. The results of experimental investigations of the coastal zone in the south-east of Sakhalin Island, using the developed experimental prototype of the autonomous mobile robot, are given.

Vertical structure of the velocity field induced by mode-I and mode-II solitary waves in a stratified fluid

Abstract.The structure of the velocity field induced by internal solitary waves of the first and second modes is determined. The contribution from second-order terms in asymptotic expansion into the horizontal velocity is estimated for the models of almost two- and three-layer fluid for solitons of positive and negative polarity. The influence of the nonlinear correction manifests itself firstly in the shape of the lines of zero horizontal velocity: they are curved and the shape depends on the soliton amplitude and polarity, while for the leading-order wave field they are horizontal. Also the wave field accounting for the nonlinear correction for mode I has smaller maximal absolute values of negative velocities (near-surface for the soliton of elevation, and near-bottom for the soliton of depression) and larger maximums of positive velocities. For solitary waves of negative polarity, which are the most typical for hydrological conditions in the ocean for low and middle latitudes, the situation is the opposite. The velocity field of the mode-II soliton in a smoothed two-layer fluid reaches its maximal absolute values in a middle layer instead of near-bottom and near-surface maximums for mode-I solitons.Graphical abstract