The state of knowledge about the study of the hydrophysical processes and ecosystems of large lakes and the White Sea are considered. The data are presented that are needed for obtaining new knowledge necessary to create basic numerical models for predicting ecosystem changes with calibration and verification of numerical models. The advantages of setting up specialized surveys at research polygons in the lakes and the White Sea are demonstrated compared to organizing such experiments in the ocean. Both the traditional approaches to modeling physical-chemical-biological processes, and innovative developments for describing aquatic ecosystems where knowledge is lacking are represented, e.g. for the ice-covered winter conditions using so-called finite automata method. Ecosystem change estimates are suggested, to be applied for sustainable management and conservation of the resources of waterbodies. Information about the application of the cognitive approach in describing the socio-ecological-economic processes in the waterbody-catchment system is provided. The necessity of creating multipurpose polygons to create advanced technologies in the field of hydrology, oceanology, meteorology and climatology, and improvement of the monitoring system is substantiated. It is argued that the resources and capacities of various organizations need to be united to arrange integrated experiments and build models for dealing with the tasks of the rational management of internal waters.

This paper presents new results obtained during combined processing of the current and the conditional density measurements in three cruises in July, October and November 2016 in Northern part of Black sea. Current velocity profiles were measured using a Lowered Acoustic Doppler Current Profiler. The spatial distributions of current are presented. The specific features of the vertical distribution of kinetic energy averaged for all stations in the sea active layer are discussed. It is shown that the decrease of kinetic energy with depth occurs most rapidly in the layers of seasonal and permanent pycnoclines. It is established that there is an almost linear relation between kinetic energy and conditional density. The seasonal variability of average kinetic energy occurs to depth of isopycnic with the value of conditional density is 16.7 kg/m3 . The profiles of the squared vertical shear of current velocity isopycnically averaged from ensemble of stations are given. In the main pycnocline layer, in the vicinity of the buoyancy frequency maximum, the maximum of squared shear is noted for each expedition. The profiles of vertical turbulent diffusion coefficient in layers of permanent picnocline derived from fine-scale data using G89 parameterization are discussed. According to date of three cruises the increasing of vertical exchange processes with depth growing is observed. The highest value of the coefficient diapycnal exchange occured in the summer season.

The paper represents findings based on observational data obtained in shallow Lake Vendyurskoe during early-spring under-ice convection development. The use of highly-precise temperature sensors allowed to quantitatively describe dynamics of the convectively-mixed layer and to estimate its integral parameters. Currents within convectively-mixed layer were registered with Acoustic Doppler Current Profilers. Despite relatively low (mm/s) current velocities, convectivelymixed layer dynamics is presented by the wide spectrum of pulsations typical for the developed turbulent regime. Main attention is paid to the study of low-frequency fluctuations, i. e. large-scale convectively-mixed layer structure. The use of hodographs and progressive vector diagrams allowed revealing a system of convective cells functioning as coherent structures. Observed irregularity of pulsations in the low-frequency part of spectrum does not contradict to the existence of quasi-deterministic cells. Dynamics of such pulsations can be considered as an example of the chaos onset in lowdimensional systems. The cell recognition procedure was based on fitting the experimental progressive vector diagrams to the set of diagrams calculated for the case of idealized cell models. Estimation of the cell parameters is performed in frames of the developed procedure of their identification.

A problem on assessing tidal changes in regional climates of limited marine systems using the Kara Sea as an example is solved. The basin for solving this problem is the three-dimensional finite-elements hydrostatic model QUODDY-4. Applying this model, we carried out two numerical experiments. In one of them the external forcing is prescribed as total (wind + thermohaline + tidal), in the second it shows up as combined total (wind + thermohaline). It is established that the fields of seawater temperature and salinity at the depth of the pycnocline base and sea surface level correlate well with observations: the correlations between them are 0.681, 0.493 and 0.678 respectively. If the tidal changes in the above climate variables are determined as differences between these variables for total and combined forcings, we concluded that tidal changes in temperature and sea surface level turn out to be commensurable with the merely variables, and the tidal changes in salinity is an order of magnitude less than this variable. In other words, the tidal changes in seawater temperature and sea surface level contribute significantly to the formation of these variables, while the tidal changes in salinity is measurable.

The paper describes monthly and intra-seasonal dynamics of the major fronts in the River Plums and the Marginal Ice Arctic frontal zones in the Kara Sea in the warm period from July to September 2007 and 2011. Quantitative characteristics of these frontal zones are estimated. The sea surface temperature fields and the gradients calculated from them from the product GHRSST OSTIA Sea Surface Temperature and Sea Ice Analysis are used as the initial data. It is established that the frontal zones break up into separate contrast spots in the gradient field, and to separate them into the entire sea, aggregation of data over gradients and temperatures is required, which required the development of a separate technique. The complex structure of the frontal zones and the considerable spatio-temporal variability of the position of their main fronts are shown. Two main frontal zones are identified in the water area of the sea: the River Plums associated with the influence of the rivers Ob and Yenisei and the Marginal Ice Arctic front, connected with the melting of Arctic ice. In the conditions of the modern climate, a significant dynamics of the River Plums front variation and a relatively stable position of the Marginal Ice Arctic front are established. It is shown that the intra-seasonal dynamics in the Marginal Ice Arctic front increases to a peak in September and the River Plums front peaks in August. In other months, the seasonal dynamics is expressed in the meandering of the position of the Marginal Ice Arctic front and the River Plums front. It is revealed that in 2007 and 2011, with a minimum ice cover, the average temperature gradient inside the River Plums frontal zone was 0.029 °C/km, with a width of about 137 km, and in the Marginal Ice Arctic front — 0.027 °C/km with a width of almost 104 km.

The mathematical modeling of oil spills on the sea surface has recently attracted considerable attention of researchers. Despite the fact that a number of approaches for modeling the main processes of oil transport and transformation on the sea surface are proposed in this area, many of them are not satisfactory and do not correspond to the data of observations and/or experiments. The reason for this is the complexity of these processes, which are complex. In the constructed models, a significant number of acting factors are simultaneously considered and a large number of selected constants are introduced in the expressions used, which leads to difficulties in the analysis (interpretation) of the results. In this regard, there is a need to consider independently the individual processes accompanying the transformation of the oil spill. This paper focuses on the process of oil spill spreading and the movement of its boundary. The approach is based on the solution of the system of partial differential equations (PDE) arising from the consideration of the balance of forces acting on the axisymmetric spot. The aim of the work is to construct a method of numerical solution capable of correctly describing the motion of the contact boundary of the spill. The originality of the proposed approach lies in the fact that, on the one hand, it offers boundary conditions specific to each Fay’s stage, and on the other hand, a method of characteristics is considered to numerical solution of the problem considered. It is shown that the resulting numerical solution is consistent with the Fay’s formulas.characteristics is considered to numerical solution of the problem considered. It is shown that the resulting numerical solution is consistent with the Fay’s formulas.

Based on the field observations obtained during the experimental work in August 2016 in the deep-water region of the Barents Sea below the critical latitude for the semi-diurnal tide, a statistical analysis of temporal temperature variability and light attenuation indicator at the boundaries of the jump layer was performed. The main features of the field of shortperiod internal waves are highlighted. The region is dominated by internal waves with a height of 1 to 2 m and a period of 10 to 20 minutes, which is approximately 45 % of the total number of observations. 40 % of registered waves have periods from 20 to 60 minutes. Explosives with a period of more than 20 min have a length of 500 m and more, and a phase velocity of 40—45 cm/s. Well-pronounced, consistent with the criteria of intense internal waves, a train system for the entire period of work was not observed. Statistically significant global time scales of vertical displacements of the thermocline equal to 20 and 40 min were identified. In the ebb phase, in the range of periods of internal waves of 25—50 min, a one-time mutual amplification of thermocline oscillations takes place according to the temperature and light attenuation index, which falls on the syzygy during the maximum period. It has been established that in the range of 20—60 min there is a synchronous relationship between temperature fluctuations and the attenuation coefficient of light with a coherence above 0.9. Such a high coherence value is a sufficient justification for the use of contact and remote optical measuring instruments for recording internal waves in the deep-water areas of the Barents Sea in the range of 20 to 60 minutes. Vibrations of a thermocline with periods of less than 20 min manifest themselves in the form of irregular coherent structures with phase instability, and therefore cannot serve as a reliable indicator of the field of short-period internal waves based on the results of optical observations only.

In the paper, the far fields of surface wave perturbations excited by an oscillating localized source rapidly moving in a heavy liquid of infinite depth are studied. It is shown that the excited fields are a sum of two wedge-like waves located insider the corresponding wave wedges. Each of the excited two waves is a complicated wave system of transverse and longitudinal perturbations. The properties of the dispersion curves are studied and the phase pictures describing the structure of wave surface perturbations are calculated. The characteristics of the excited wave fields are studied depending on the basic parameters of the wave generation such as the velocity of motion of the perturbation source and the frequency of its oscillations. Uniform asymptotic solutions are constructed in terms of the Airy function and its derivative, which permits describing the far fields of surface perturbations both outside and inside the corresponding wave wedges.

The principles of radar image creation, which directly show surface velocity field, are considered. The main variable determined radar images quality is velocity fluctuation sensitivity defined for given an surface area. Intensity images determined by intensity fluctuation sensitivity of are created at once. The creating concept and achievable features of images are different for stationary, airborne and spaceborne platforms, consequently, were seen progressively with estimation of attainable parameters. For shipborne radar of around survey with wideband signal and different-phase processing, velocity fluctuation sensitivity may be about ~10 cm/s on the symmetry area about ~30m with small range. Airborne ATISAR (interference synthetic aperture radar with along-track antenna base) is capable to provide the better velocity sensitivity on the small areas and significant range, that’s answer to many oceanology propositions. It notes that special algorithm is necessary for creating velocity images by the side-looking SAR without the azimuth shift of moving areas. Spaceborne ATISAR, with the same processing technology, needs the essential increase of antenna base dimension and radiation power – that’s attained in Germany space system Tandem TerraSAR-X. Applicability and development perspectives of given methods are also considered.

The paper in summary presents a description of the history of the emergence and development in Russia of ocean hydrophysics, one of the main parts of the multidisciplinary science — Oceanology. The beginning of hydrophysics in Russia was laid by the works of the great Russian scientist Mikhail Vasilyevich Lomonosov, who in the second half of the 18th century for the first time analyzed and described the main features of the hydrophysical regime of the Arctic Ocean. The first domestic instrumental observations on the temperature of ocean water at great depths were made by Ivan Fedorovich Krusenstern in 1803—1806 during his round-the-world voyage on the ship “Nadezhda”. An important event in the development of hydrophysics in the 20th century was the publication of the book by Yuli Mikhailovich Shokalsky “Oceanography” (1917) — the first national monograph, which gave a detailed idea of the state of hydrophysical knowledge at that time. In the framework of a systematic review of the major milestones in the subsequent formation and development of ocean hydrophysics, the names of the leading figures of Russian science, who created its foundations and their own scientific schools that have been active for many decades and have many world-class achievements in their work, are named in the paper.