In this paper, sub-inertial waves propagating on the Kuril shelf and the oceanic trench are considered. Against the background of a historical review of the beginning of the study of topographic waves and the appearance of relevant terms, a description of the features of wave propagation and the derivation of the main dispersion equations are given. We show that all variants of the topographic solutions presented in the article are basically based on the same dispersion relation: this is the dispersion relation for Rossby topographic waves. Two separate classes of localized solutions have been constructed: one is for the shelf, and the second, in fact, is also for the shelf, but which is commonly called trench waves. We demonstrate that the transverse wave number for trench waves is not independent, as for shelf waves, but is a function of the longitudinal wave number. In other words, Rossby topographic waves are two–dimensional waves, while shelf waves are quasi-one-dimensional solutions. The analytical novelty of the work consists of the fact that we can make crosslinking of trench and shelf waves. This fact was not presented in previous articles on this topic.

In order to study sensitivity of seawater temperature and salinity in the no-ice Laptev Sea to their restoring times, appending in the boundary conditions for these variables at the free surface, the 3D finite-element hydrostatic model QUODDY-4 and the indirect means of describing internal tidal waves have been applied. The latter is based on the use of the corrected eddy diffusivity representing the sum of the same uncorrected diffusivity and the diapycnal diffusivity. The first of them characterizes the influence of non-tidal factors, computed using 2.5-level eddy closure scheme, the second, determined by the ratio of internal tidal waves induced baroclinic tidal energy dissipation to the buoyancy frequency in square, the influence of purely tidal factor. The estimate of this dissipation obtained from a solution of auxiliary problem on the internal tidal waves dynamics and energetics is attached. Seawater temperature and salinity in the subsurface and near-bottom layers of the Sea and also their vertical distributions along the 120E meridional transection obtained for the strong, moderate, and mixed restoring times are discussed. As a result, it is clarified that seawater temperature and salinity are weakly sensitive to changes in the restoring time. The saying follows from a comparison of model averaged (over a chosen period and by the Sea area) values of seawater temperature and salinity, and from their local vertical profiles, computed with regard to accepted estimates of the restoring time.

Based on satellite data, E. huxleyi bloom contouring, quantification of particulate inorganic carbon (PIC) production and increment of CO₂ partial pressure, (pCO₂) in surface water were performed. 18-year (2003–2021) time series of these variables are obtained for the Norwegian, Greenland and Barents seas. The bloom areas in the North Atlantic–Arctic water are the lowest in the Greenland Sea varying from 10×10³ km² to (20–40)×10³ km². In the Norwegian and Barents Seas they reach in some years (60–80)×10³ km² and (500–600)×10³ km², respectively. The total PIC content within E. huxleyi blooms rarely exceeds in the Greenland and Norwegian seas 12–14 kilotons and 40 kilotons, respectively. In the Barents Sea, in some years, it can be up to 550 kilotons. The highest level of pCO₂ within E. huxleyi blooms in surface waters in the Barents Sea was ~350 µatm. In the Norwegian Sea, pCO₂ in surface waters within the E. huxleyi bloom was also close to 350 µatm, but most often it remained about 250 µatm. In the Greenland Sea there were only four years of relatively enhanced pCO₂ (up to 250 µatm), otherwise remaining below the level of confident determination by our method. As E. huxleyi blooms are generally very extensive, occur throughout the entire World Oceans (and hence in sum occur all year around), this phenomenon has a potential to both decrease to some degree the role of the World Oceans as sinkers of atmospheric CO₂, and affect the carbonate counter pump.

The Suez Canal suffers from heavy maritime traffic, especially oil tankers, due to its strategic location between the Mediterranean and the Red Sea. As a result, it is prone to accidental oil spills, which might obstruct the maritime lane via the canal and severely harm the marine and coastal ecosystems. This study aims to forecast an oil spill trajectory and fate under the influence of different wind regimes using the General NOAA Operational Modeling Environment (GNOME) and the Automated Data Inquiry for Oil Spills (ADIOS2) models to define the potentially affected regions. Hence, four scenarios were simulated, assuming a spill of one thousand metric tons of Arabian light crude oil into the seawater about two kilometers from the Suez Canal’s southern entrance. The results highlight that wind direction and sea currents substantially affect the movement of oil spills. The trajectory maps show that the north-west wind forces the spilled oil to move toward the southeast direction, threatening the navigation lane through the Suez Canal and about 38 km of beaches south of the canal, which has several vital projects such as the Ayoun Mousse power plant and a lot of resorts. In the case of northern winds, the oil moved south in the center of the Gulf, which may allow response teams more time to clean up the spill. However, in the case of north-east winds, the oil drifted southwesterly and threatened the Green Island and western shores of the Gulf, which has many tourist villages. About a quarter of the oil evaporated, and more than two-thirds of the oil emulsified in all four scenarios. For the first time, this study has provided an understanding of oil spill forecasting and trajectory modeling for the Suez Canal’s southern entrance. Also, it can be considered a prediction tool for Egypt’s policymakers and Suez Canal Authority (SCA) to develop adequate and practical strategies to mitigate crude oil spill consequences.

Theoretical models of the statistical characteristics of the lidar echo signal have been developed to interpret the results of optical sounding of heavily eutrophicated water bodies. Formulas are obtained for calculating the statistically average value and coefficient of variation of the energy of the elastic backscattering signal coming from the near-surface layer of water with randomly inhomogeneous absorption and scattering coefficients. Examples of the dependence of the indicated signal characteristics on the coefficients of variation of the optical characteristics of water are given. It has been established that fluctuations in the absorption coefficient lead to an increase in the average energy of the received signal, and fluctuations in the scattering coefficient to its slight decrease. A significant decrease in the average echo signal energy can be observed with cross-correlated fluctuations in the absorption and scattering coefficients, i. e. in the case when the attenuation coefficient fluctuates at a constant single scattering albedo. Considerations are made on how algorithms for estimating the average values of the optical characteristics of water and the parameters of their inhomogeneities from the average value and the coefficient of variation of the echo signal energy can be constructed.

The possibility of dolphin’s auditory system to solve the complex problem of identifying and classifying noise-like signals according to certain invariant features is considered under conditions of spatial uncertainty of their simultaneous presentation. There was studied the ability of bottlenose dolphins, which were trained to recognize and classify such signals, to select a certain class of signals from several that sound simultaneously. The dolphin had to recognize a positive class signal with a pair of simultaneously sounding signals: positive-negative (alternative choice) and with simultaneously sounding three signals: positive-negative-negative (multiple choice). It’s shown that the dolphin effectively solves the problem with a simple alternative choice of two signal sources, at the limit of reliability when choosing from three sources and unreliable when choosing from more sources.

A model of the formation of the gradient sea-level field by the space bi-static radar measurements is developed. An interferometer radar with cross-sectional base is used as a receiver. The relatively small antenna 5–10 m of cross-sectional base gives a huge gain in energy when working for quasi-mirror scattering in the range of short wind waves. The efficiency of the system is evaluated by converting the dynamical model of tsunami wave evolution for the case of the Kuril earthquake (October 4, 1994) into a panoramic radar image of the sea level. The panoramic image of the front wave allows predicting the direction, amplitude and, finally, the expected time of tsunami arrival to a given point. The obtained radar image confirms the main feature of the quasi-mirror method: the fluctuation-level sensitivity varies within the radar swath (~2000 km) and is the worst near the mirror point. For the chosen radar parameters, the average sensitivity in the swath is ~5 cm for a site (15 × 15) km. Without accounting the time required to transmit information from the receiver to the tsunami–prone sites, the minimal time interval between the appearance of the wave front and the tsunami alert is determined by the number of sequentially launched small tandem spacecrafts. For a single tandem this time is about 45 min.