A half-year long time series of the bottom layer velocity measured in situ in the Hoburg Channel displayed seven-day oscillations of the saltwater flow. The flow was characterized by alterations of surges with the increase of northward velocity to approximately 0.2–0.3 m/s and blockages when the northward velocity vanishes or becomes small negative. The measured time series of the northward velocity component was surprisingly highly correlated with the simulation by NEMO reanalysis at the correlation coefficient of 0.82 and the 95 % confidence limits of 0.76–0.86. The seven-day oscillations were accompanied by almost synchronous oscillations of the southeast component of the wind vector. It can be considered convincing evidence that the seven-day oscillations in the saltwater flow were caused by wind forcing.

The available bathymetry data of the Issyk-Kul Lake from different sources are analyzed and corrected for mutual consistency and deviation from the GPS coordinates on the shoreline. As a result, a gridded bathymetry of the Lake with 360×360 m bin size suitable for use in numerical circulation models is compiled and made available on the Internet for free download.

Achievements in development of the technique of operational measurements of the water structure in the bottom layer, based on vertical profiling of the water column using standard multiparameter probes operated with an armored cable in a free fall mode from surface to bottom are presented. Instead of cable winches, simpler devices operating on the principle of longline houler have been proposed. Full-scale tests have shown that the new universal Underway CTD system is not inferior to its counterparts and has prospects for further development.

The article describes the advanced design of Tilt Current Meter (TCM), developed in the Shirshov Institute of Oceanology. This type of meters is used in recent years mainly in Western countries due to low cost, ease of manufacture and the possibility of replication. In most designs the device is a physical pendulum in the form of a long floating cylinder attached to a stationary platform and deviating from the vertical in the action of hydrodynamic force. The tilt is recalculated to the flow rate by the accelerometer signals. The main drawback of the existing samples is the presence of contaminating signals in measurements due to transverse auto – oscillations of the cylinder in a stable flow in the formation of vortices wake. In the advanced design the watertight container with the electronics block and the additional element of buoyancy are placed in an external rigid shroud. The shroud is made of cylindrical plastic pipe with a wall perforation area of 55%, this measure effectively prevents the appearance of transverse oscillations in a wide range of Reynolds numbers. For the developed design the simple calculation ratios allowing to carry out estimation of a measuring range and sensitivity of the meter on the basis of its geometrical and mass parameters are given. The improved design of the ISTT is primarily intended for the measurement of weak bottom currents, although it is possible to regulate the sensitivity for measurements in the surf zone. The range of measured bottom current velocities is 3–56 cm/s with a maximum relative error of 25% for small velocities and 3–5% for maximum velocities.

Измерения, выполненные в окрестности Слупского порога с помощью привязного свободно-падающего микроструктурного зонда, выявили наличие пятна с высоким уровнем скорости диссипации турбулентности непосредственно за порогом с восточной стороны в придонном слое, заполненном распространяющейся на восток соленой водой. Предложен метод, позволяющий количественно оценить роль топографического препятствия наподобие Слупского порога в перемешивании/трансформации затоковой воды по данным микроструктурных измерений. Для этого сначала по вертикальным профилям удельной скорости диссипации кинетической энергии турбулентности и потенциальной плотности рассчитывается скорость вовлечения воды пониженной солености из вышележащего слоя в придонный турбулентный слой соленой воды. Затем, полагая, что в придонном течении соленой воды критическое значение числа Фруда достигается непосредственно над порогом, оценивается расход течения. Наконец, из баланса между адвекцией и турбулентным вовлечением можно получить оценку изменения солености распространяющейся на восток соленой воды из-за интенсификации перемешивания в области порога. Получено, что локальное усиление турбулентного перемешивания в районе Слупского порога ответственно примерно за 5 % уменьшения солености затоковых вод на пути от Арконского бассейна до Готландской впадины.

В работе представлены результаты подспутниковых экспедиционных работ, проведенных в летние периоды 2015-2016 гг.в акватории Юго-Восточной Балтики в районе Самбийского полуострова.Выполнен анализ и численное моделирование траекторий двух дрифтеров, выпущенных в море во время подспутниковых экспериментов.Показано, что характер дрейфа лагранжевых буев может существенно отличаться из года в год, что во многом объясняется ветровыми условиями и степенью активности вихревой динамики в регионе.Проведено численное моделирование распространения лагранжевых дрифтеров на основе численной Принстонской модели океана (POM), адаптированной к району Юго-Восточной Балтики, со встроенным блоком расчета траекторий лагранжевых частиц.В большинстве случаев получено близкое соответствие траекторий распространения модельных лагранжевых частиц и дрифтеров.Определены районы и метеоусловия, при которых дрифтеры совершают в основном адвективное перемещение, при этом ИК (инерционные колебания) не оказывают на них существенного влияния.Также описаны условия, при которых в динамике преобладают ИК, которые «захватывают» частицы, и под их воздействием они описываю замкнутые петли с диаметром ~2-6 км

Numerical simulation based on the Princeton Ocean Model (POM) was performed for a region of the Southeast Baltic in order to compare data on the spatial distribution of velocity and bottom sediments. Special attention was focused on the influence of western and northeastern winds, which generate intense quasi-geostrophic currents can may cause very high velocities in the near bottom layer, which results in the elution of bottom sediments and transport of their fine fractions. An abrupt change in wind velocity intensifies the effect of elution due to generation of inertial internal waves that penetrate into the bottom layer. The spatial distributions of the velocity in the surface and near bottom layers are compared with data on bottom sediments. It turned out that areas with the highest velocities that formed under the effect of western and northeastern winds in most cases coincide with areas where bottom sediments are represented by coarse-grain fractions of gravel and sands.

The influence of wind and hydrodynamic processes on the spreading of turbid waters from the Vistula Lagoon into the Baltic Sea was studied. Our research is based on joint analyses of remote sensing data and those from concurrent in situ measurements of the three-dimensional structure of the outflow. A strong difference in the water optical properties of the Baltic Sea and the Vistula Lagoon caused by an intense summer bloom of cyanobacteria allowed studies of the evolution and transformation of the outflow in mid-July-early August 2014 using Ocean Color satellite data. Our in situ measurements revealed that waters from the Vistula Lagoon were exclusively present in the upper water layer. The study was conducted under various wind and, therefore, under different upwelling/downwelling conditions, thereby determining different patterns of wind-driven currents, which enabled us to assess their impact on the propagation of the lagoon outflow. One of these patterns was reaching to the south, along the Vistula Spit, and another one reaching to the north, along the Sambia Peninsula. We show that the main spreading direction of the plume strongly coincides with that of wind-driven currents. However, if vortical structures are present in the Bay of Gdansk, they also affect the plume transformation, and that should be taken into account when the propagation of water pollution is forecasted.

The influence of wind and hydrodynamic processes on spreading of turbid waters from the Vistula Lagoon into the Baltic Sea was studied. The research was based on joint analysis of remote sensing data, simultaneous subsatellite measurements and numerical modeling. The sharp difference in water optical properties of the Baltic Sea and the Vistula Lagoon, affected by intense summer bloom of cyanobacteria, made it possible to study the evolution and transformation of the outflow in July-early August 2014 using visible satellite data. Forced by coastal jet streams, the outflow spread throughout the Bay of Gdansk, dramatically affected by the circulation processes in the bay. A three-dimensional structure of the outflow was analyzed. In-situ measurements revealed the presence of the Vistula waters exclusively at the upper water layer. A numerical simulation of suspended matter spreading over the Bay of Gdansk was performed using a modified Princeton Ocean Model (POM).

The peculiarities of the space-time structures of the currents in the sea appearing after wind forcings that cause upwelling and downwelling are investigated. Numerical modeling using the Princeton Ocean Model (POM) and data analysis were performed for the local area of the Southeastern Baltic adjacent to the Kaliningrad Region (Russia). The geostrophic and ageostrophic velocity components were distinguished to determine the peculiar features of different types of currents. We suggest considering the collinearity coefficient: the scalar product of the geostrophic and ageostrophic velocity vectors. We also considered the local vorticity and turbulent viscosity. Their difference during the upwelling and downwelling was noted. The data of the current velocity simulations and the ADCP measurements at the location of the D-6 oil platform (the Kravtsov oil field) were compared. The modeling adequately reproduces the most energetic geostrophic jet currents and their space-time characteristics.

A data set of closely spaced CTD profiling performed aboard Russian and Polish research vessels during 1993–2009 and numerical modeling are applied to study the variability in the asymmetric transverse structure of salinity/density in the Słupsk Furrow (SF) overflow of the Baltic Sea. The numerical simulations show that, on the one hand, the overflow may be dynamically treated within the SF as a subcritical, eddy‐producing gravity current in a wide channel, and on the other, at the sill displays some features peculiar to frictionally controlled rotating flows. Comparison between the field measurements and the simulation results indicates that the variability of the cross‐channel density structure is caused mainly by meandering of the gravity current and mesoscale eddies – mostly above‐halocline cyclones and intrahalocline anticyclones. The meanders and eddies are found to be strongly affected by the bottom topography and wind‐forcing.

Closely spaced CTD transects across the Słupsk Furrow displayed a ‘downward- bending’ of salinity contours below the salinity interface on the southern flank due to a transverse circulation in the saline water overflow. Numerical simulation of a gravity current in an idealized channel with geometry, dimensions and initial density stratification all much the same as in the Słupsk Furrow was applied to verify whether the downward-bending could be transformed into an inverted density stratification. Some arguments in favour of the possibility of convective overturning due to the differential transverse advection beneath the gravity current, brought on by the numerical simulations, are discussed.

The specific features of the upwelling in the southeastern Baltic have been studied by comparing the field observations and numerical simulations. The upwelling registered in October 2005 (when a gale caused by a northeastern wind with a velocity of 15 m/s continued for about three days after a period of relatively calm weather during which the thermohaline structure was in the state close to the summer one) has been considered in detail. The gale caused a decrease in the temperature by approximately 4°C in the along-shore belt with a width of about 8 km in the region with depths of about 25 m located at a distance of approximately 8 km from the shore. The changes in the thermohaline structure that originated as a result of this gale were simulated using a 3D numerical model based on the Princeton Ocean Model (POM). This made it possible not only to consider the variability of the thermohaline fields at the observation region but also to study a rather wide region and to consider the field of velocity in addition to the fields of temperature and salinity. Subsequently, the numerical model made it possible to estimate the upwelling effect during cooling of the upper layer, which was more intense than the effect of turbulent mixing by an order of magnitude. It was confirmed that the specific features of the upwelling spatial structure depend on the geographic position of the upwelling observation region and on the velocity and duration of the wind that causes the upwelling.

We present an analysis of meteorological and hydrophysical variability in the vicinity of Black sea North-East coast with the use of satellite sea level anomaly (SLA), sea surface temperature (SST) databases, in-situ temperature measurements and meteorological station standard measurements. In addition to satellite data calibration, particular goal was to examine meteorological forcing on SLA and SST fields in order to study ocean-atmosphere interactions through descriptive elements of coastal weather system. Despite the present study revealed several typical properties of the Gelendzhik coastal "weather machine", there are essential opportunities for further combined meteorological and hydrophysical processes examination on the basis of satellite and in-situ measurements.

Sequences of high resolution transects of temperature, salinity, and oxygen concentration measured from the Arkona Basin through the Bornholm Deep and the Slupsk Furrow to the Gulf of Gdansk in the summer of 2006 are discussed. The measurements were made using U-tow CTD probe with an oxygen sensor. The measurements revealed peculiar features in the distributions of thermohaline and oxygen fields. The data allow us to describe one of the possible scenarios of water interaction in different basins during warm season in the stagnation period. This scenario is characterized by the lack of any noticeable mass exchange between different basins. At the same time, evidences of previous intrusions are notable in the Bornholm Basin. The hypothesis is put forward that intrusions of saline warm water from the Arkona Basin are locked by the waters from the intermediate layer. A significant decrease in oxygen concentration between the two basins in the eastward direction at the same isopycnal surface is also noted.

The flows of brackish waters in the upper layer and saline waters in the lower layer meet above the Slupsk Sill, which makes this one of the most significant features of the Baltic Sea, controlling as it does the ventilation of the deep basins in its central region. Earlier high-resolution measurements using towed scanning probes conducted here for more than ten years had revealed the complexity and variability of the water dynamics in this area. Mapping surveys repeated in quick succession are needed to study the water exchange in such an area. A survey of this kind was attempted in October 2003 during the 57th cruise of the r/v ‘Professor Shtokman’. Three surveys were carried out in the areas of the Slupsk Sill, the eastern Bornholm Basin, and the western Slupsk Furrow by means of a scanning probe towed along closely-spaced transects. The water structure around the sill was different each time, despite the rather short time gaps between the surveys. As follows from the data analysis, during the first survey, the saline Bornholm waters flowed over the sill as an axially symmetrical jet and entrained the adjacent freshened cold waters of the intermediate layer. In ten days, this joint flow displaced to the southern flank of the sill and propagated

The ventilation of the Baltic Sea deep water is driven by either gale-forced barotropic or baroclinic salt water inflows. During the past two decades, the frequency of large barotropic inflows (mainly in winter) has decreased and the frequency of medium-intensity baroclinic inflows (observed in summer) has increased. As a result of entrainment of ambient oxygen-rich water, summer inflows are also important for the deep water ventilation. Recent process studies of salt water plumes suggest that the entrainment rates are generally smaller than those predicted by earlier entrainment models. In addition to the entrance area, the Slupsk Sill and the Slupsk Furrow are important locations for the transformation of water masses. Passing the Slupsk Furrow, both gravity-driven dense bottom flows and sub-surface cyclonic eddies, which are eroded laterally by thermohaline intrusions, ventilate the deep water of the eastern Gotland Basin. A recent study of the energy transfer from barotropic to baroclinic wave motion using a two-dimensional shallow water model suggests that about 30% of the energy needed below the halocline for deep water mixing is explained by the breaking of internal waves. In the deep water decade-long stagnation periods with decreasing oxygen and increasing hydrogen sulphide concentrations might be caused by anomalously large freshwater inflows and anomalously high mean zonal wind speeds. In different studies the typical response time scale of average salinity was estimated to be between approximately 20 and 30 years. The review summarizes recent research results and ends with a list of open questions and recommendations.