Based on the analysis of oceanographic survey materials on the standard section S1 and satellite information, important features of the influence of tidal currents on the formation of hydrological conditions in the La Perouse Strait and adjacent waters have been identified. It was revealed that in the warm season, when the seasonal flow is directed from the Sea of Japan to the Sea of Okhotsk (Soya Warm Current), at the high tide in the northern part of S1 section the cold water with low salinity is observed in the surface layer (the temperature may differ from the southern stations by 3 times, and the salinity by 2 psu). At low tide in the northern part of S1 the water is also cold, but with high salinity, which indicates the inflow of water from the West Sakhalin current into the Sea of Okhotsk. The temperature contrasts between the northern and southern parts of the Strait are also confirmed by satellite observations. During the cold season in the northern part of the strait, there is a flow of colder and less salty Okhotsk Sea water into the southeastern part of the Tatar Strait. It is wider and more developed in depth compared to the summer season. At low tide, when the tidal current is directed to the east, this flow narrows noticeably.

Purpose. The paper is aimed at studying the spatial and temporal variability of a latent heat flux - one of the important components of heat balance in the northwestern Pacific Ocean and the Far Eastern seas based on the ERA5 5 reanalysis data. Methods and Results. The ERA5 5 reanalysis data on a latent heat flux in the area limited by the coordinates 42-60 degrees N and 135 -180 degrees E and including the Far Eastern seas and the northwestern part of the Pacific Ocean constituted the material for the study. The array of monthly averages at a quarter-degree spatial resolution was analyzed using the standard statistical methods. The average long-term distributions of latent heat flux values for each month were constructed; the amplitudes and phases of annual and semi-annual harmonics, and the linear trend coefficients were calculated in each spatial cell, and the decomposition was performed using the empirical orthogonal functions. The range of seasonal variations is significant in the zone of warm currents, and it sharply decreases in the northern part of the area under study in the Pacific Ocean as well as in the Okhotsk and Bering seas. The interannual variations are manifested in the quasi-cyclic changes of the envelope based on the maximum values with a period of about 6 years. The unidirectional trends in the interannual latent heat flux variations are weakly shown. Conclusions. . Among the seasonal variations of a latent heat flux, the annual cyclicity is predominant and the most pronounced in the southern part of the northwestern Pacific Ocean (the area influenced by the warm Kuroshio Current) off the Japan Sea coast of the Honshu Island in the Tsushima Current zone. This is conditioned by a significant evaporation increase in these areas during a cold season that, in its turn, is related to a sharper temperature contrast as well as to the impact of a winter monsoon characterized by the strong and stable northwesterly winds bringing dry, cold air from the continent. In a warm period, in some areas of the studied water area, the latent heat flux values are positive that indicates the important role of water vapor condensation in the areas with high cloudiness and in the zones of quasi- stationary upwellings.

Features of spatio-temporal variability of the Bering Sea surface temperature were studied by constructing long-term average distributions for different months and using the method of empirical orthogonal functions based on ERA5 reanalysis data based mainly on satellite information, for the period 1998–2020 (spatial resolution of the data is a quarter of a degree, the time interval is one month). In each spatial cell, for each month, the average long-term values of this parameter were calculated, which showed seasonal changes in thermal conditions in the studied water area. Linear trend coefficients have been determined, which showed a stable tendency to warming of the surface layer of sea waters, most pronounced in summer. Extreme deviations from the average long-term values (anomalies) of the surface temperature of the Bering Sea are considered.

An array of ERA5 reanalysis data on the sensible heat flux on the surface of the Northwestern Pacific Ocean and the Far Eastern seas for 1998–2022 is analyzed. It is shown that the positive values of this flux (directed from the atmosphere to the ocean) were observed in spring and summer, the maximum values in May were about 2 MJ/m2 in the southwestern part of the Sea of Okhotsk, and on the ocean shelf of the southern Kuril Islands and Hokkaido Island. Negative values (backflow) are observed in autumn and winter, they reach –14 MJ/m2 in December. The imbalance between these fluxes is covered by the advection of warm waters by the Tsushima and Kuroshio Currents. The variations of the parameter are dominated by the annual course, interannual variations are expressed in its modulation with periods of about 3 and 11 years, unidirectional trends are weak.

Seasonal and interannual variability of the demersal fish species composition is considered for the depths of 70–315 m in the eastern Kunashir Strait on the data obtained in 1998–2014. The fish community includes the species belonged to nine zoogeographical complexes and eighth ecological groups. Among them, species diversity is higher for the arctic-boreal, wide-boreal Pacific, wide-boreal Asian, and low-boreal Asian complexes and for the sublittoral, elittoral, and mesobental groups. The species diversity of fish in the surveyed area depends on seasonal migrations of demersal and pelagic fishes, including pacific salmon and some subtropical and tropical species. Interannual variations in the species composition are determined mainly by changes in the depth of netting and water temperature, but do not depend on the timing of samples collection during a season.

Monthly average values of sea surface temperature from January 1998 to August 2020 are analyzed for the region covering the water area of the Far East seas and the northwestern part of the Pacific Ocean. The time function of the first mode, which describes more than 95% of the variance of a parameter under study, has been shown to have significant positive deviations from the average long-term values in January–April 2020 in the southern part of the study area, which covers the traditional feeding grounds of pink salmon. It may have been these abnormally high temperatures that affected the fish survival conditions and obstructed the spawning passage to the Russian Far East shores in the summer of 2020. In spring (May–June), the anomalies in the southern part of the study area became less expressed, but significant positive deviations from the norm appeared in its northern part and near the eastern (including the Karaginsky Bay) and western coasts of Kamchatka. Only very weak uptrends were revealed in time functions of the principal modes, indicating that there are no significant global warming trends in the region. Their envelopes with respect to lower values involve a clear manifestation of an 11-year cycle that is in antiphase with solar activity indices. No regular (for example, cyclical) components are found in variations of summer maxima in the time function of the first mode. In the oscillations of maxima of the time function of the second mode, the main contribution is made by the cyclic component with a period of 22 years.

The aim of the work was to conduct a systematic statistical analysis of the spatial and temporal variability of sea surface temperature (SST) in the waters of the Tatar Strait based on satellite data accumulated in the Sakhalin branch of VNIRO using the TeraScan receiving station for 1998‒2021. It was revealed that in different seasons of the year the SST structure is similar and characterized by the highest values in the southeast and the lowest in the northwest of the strait. An important new result was obtained by expanding of the SST field in terms of the EOF, which is associated with a sharp change in the nature of the time function of the third mode, which occurred in 2013–2014. Such changes can be considered as a climatic shift in the studied area most pronounced in the northwestern part of the strait and near the southwestern coast of Sakhalin Island, where the change was about 1 °C. This circumstance can have a noticeable effect on the state of populations of several species of shrimp and commercial fish.

Purpose. The paper is purposed at proving (based on the data of a special field experiment) the importance of vertical tidal mixing which is conditioned by the diurnal shelf waves, on the one hand, and determines the specific conditions for forming food supply for gray whales in the Marine feeding area near the Sakhalin northeastern coast, on the other hand. Methods and Results. The materials for the research were formed of the data resulted from the instrumental measurements of current velocities, water temperature and salinity (and their variations) in the bottom layer carried out at three diurnal oceanological stations in the Marine feeding area in autumn 2019 as well as the satellite data on the chlorophyll a concentration (2003-2017). Conclusions. The results of the diurnal station measurements showed that in the Marine feeding area of gray whales (on the Sakhalin northeastern shelf), there was a constantly working mechanism which intensified and weakened together with the diurnal tides (cycle was a half a month). It is manifested in the diurnal seawater temperature and salinity variations near the bottom, as well as in the vertical distributions of oceanological parameters. Due to the diurnal shelf waves providing local tidal mixing, the conditions contributing to the sustainable formation of food supply for gray whales arise in this area.

Based on the spatial distributions of sea surface temperature according to satellite observations and observational data on standard oceanographic sections of the southwestern shelf of the Sakhalin Island in summer (August) and autumn (November) shows the existence of seasonal upwelling, which is formed under the influence of northerly and northwesterly winds, typical of the winter monsoon. In this area, it manifests to a lesser extent than in the northern part of the Tatar Strait (Shevchenko et al., 2011) due to the features of the bottom topography (short deep shelf) and the large thickness of the upper heated layer, but quite clearly. At the same time, deep water rises, rich in biogenic elements and mineral phosphorus, which is important for the development of young growth of kelp. In the warm period of the year, under the conditions of the prevailing southerly wind, upwelling is observed in this area sporadically (4 ̶ 5 times per season) in the form of sharp, up to 12 ̶ 15 °C, water temperature drops in the coastal area lasting from 3 to 12 days. Most often they occur during the passage of cyclones over the southern part of Sakhalin or Hokkaido Island, when they enter the southern part of the Sea of Okhotsk or the South Kuril Islands and formed east and northeast blowing winds over the study area.

Purpose. The work is purposed at studying spatio-temporal variability of the resulting long-wave radiation reflecting the ocean heat loss, on the surface of the northwestern Pacific Ocean and the Far Eastern seas based on the ERA5 reanalysis data for 1998-2021. Methods and Results. The ERA5 reanalysis data on the resulting long-wave radiation in the region limited by 42 & DEG;-60 & DEG;N and 135 & DEG;-180 & DEG;E, and including the Far Eastern seas and the northwestern part of the Pacific Ocean constituted the material for the study. The array of monthly averages with a quarter degree spatial resolution was analyzed using the standard statistical methods. Average long-term distributions of long-wave radiation were constructed for each month and by seasons; the amplitudes and phases of the annual and semi-annual harmonics, and the linear trend coefficients were calculated in each spatial cell, also the empirical orthogonal functions decomposition was performed. The highest values of long-wave radiation were observed in winter, primarily in the Sea of Japan and in the area east of Honshu Island. The heat flux from the ocean to the atmosphere reached its significant values in the same areas in autumn, as well as in the coastal strip along the entire continental coast. The most probable reason for such features in the distribution of long-wave radiation is the atmospheric circulation, namely, the steady northwesterly wind (winter monsoon) characteristic of a cold season. In the open ocean, heat loss is less, especially in summer, which is facilitated by dense clouds. Similar results were obtained by the method of empirical orthogonal functions: the values of the first mode spatial distribution decrease from west to east (in absolute value). Conclusions. It was revealed that heat losses in the studied area occur mainly in autumn and winter in its western part - in the Sea of Japan, east of Honshu Island, and especially in a narrow strip along the entire mainland coast; but in winter in the areas north of 48 & DEG;N (the Tatar Strait, the Sea of Okhotsk), they are damped by the ice cover. Unidirectional trends in the changes of long-wave radiation are pronounced relatively weakly, and differ in the same water areas in different seasons of a year.

The materials of instrumental measurements of the current velocity and water temperature at the horizons of 100 and 10 m near the continental slope of southwestern Sakhalin Island (south of Moneron Island) are considered. At a depth of 100 m, diurnal fluctuations in water temperature with an amplitude of 0.5–1°C were revealed, depending on the intensity of tidal currents (temperature decrease when the flow is oriented southeast, towards the La Perouse Strait), interpreted as tidal upwelling. The materials of hydrological surveys on the T1 oceanological section have been analyzed, vertical distributions of water temperature, chlorophyll-a and biogenic elements have been constructed based on the measurements on April 15, 1999. They are consistent with the concept of tidal mixing.

Using the method of harmonic analysis and EOF decomposition of SST data for the surface of the Sea of Okhotsk and adjacent water areas (42–60° N, 135–160° E, SakhNIRO database and ERA5 reanalysis for 1998–2020), the main features of seasonal variations in thermal conditions were determined. It was revealed that the amplitude of the annual harmonic, which plays a decisive role in the seasonal variations of SST, generally decreases in the direction from west to east throughout the study area, the lowest values are in the zones of quasi- stationary upwellings. The phase increases along the northwest-southeast axis, the total shift is 24–25° (about 3 weeks). In the spatial distribution of the first mode (all values are positive), the water area of the Sea of Japan, the NWPO, and the southwestern part of the Sea of Okhotsk are characterized by high values. Its time function is characterized by a pronounced annual cycle, with a maximum in August–September and a minimum in February–March. The spatial distribution of the second mode has a nodal line running along the Kuril Islands from the Sea of Okhotsk side. The mode values vary along the northwest–southeast axis, with maximum positive values on the northwestern shelf of the Sea of Okhotsk and negative values in the remote part of the NWPO. The time function of the second mode has a positive maximum in July–August and a negative minimum in November–December. This nature of the second mode shows that, against the background of the main SST field described by the first mode, a peculiar seasonal “heat wave” is distinguished, propagating from the northwest to the southeast and passing along this axis in about three weeks, which is an important specific feature of the thermal regime of the study area.

2 Институт морской геологии и геофизики ДВО РАН Южно-Сахалинск, 693022, Россия Для Охотского моря и прилегающих акваторий (области, ограниченной координатами 42-60° с. ш. и 135-160° в. д.) выполнено сравнение среднемесячных рядов температуры поверхности океана (ТПО) по данным спутниковых наблюдений (база СахНИРО) и реанализа ERA5 за 1998-2020 гг.Показано, что зимой и летом в изучаемой области ТПО по данным реанализа выше спутниковой ТПО.Осенью и особенно весной на большей части акватории, напротив, ТПО по спутниковым данным выше, чем по данным реанализа

2 Институт морской геологии и геофизики ДВО РАН Южно-

The materials of satellite observations of the sea surface temperature in the study area (1998–2020) were also analyzed by statistical methods and by decomposition according to the EOF. The amplitude of the averaged curve of the annual variation of the ocean surface temperature (SST) as a whole for the region was estimated, which was 7° (the contribution of the semiannual component with an amplitude of 1°С is small), as well as the most significant anomalies that reached 4°С in cold August 2002 and 3°С in warm September 2012. A quasiperiodic course of the envelope of summer maximums with a period of 5–6 years was revealed. It is shown that there is negligible trend in the thermal regime in the study area. Based on the analysis of materials from 10 oceanological surveys, seasonal variations in hydrological conditions in the area of South Kuril Islands were studied. It is shown that the areas of the Kunashirsky and Yuzhno-Kurilsky Straits in the warm season are filled with warm and salty waters of the Soya Current, and in winter and spring - with freshened modified water from the Amur River runoff transported by the East Sakhalin Current. Annual salinity variations exceed 1.5 psu here.

Институт морской геологии и геофизики ДВО РАН Южно-Сахалинск, 693022, Россия На основе материалов многолетних спутниковых наблюдений приземного атмосферного давления рассчитаны средние многолетние показатели (нормы) за период с 1998 по 2019 г.Также для каждого месяца построены карты пространственных распределений аномалий (отклонений фактического атмосферного давления от рассчитанной нормы).Наиболее значимые аномалии, как по величине, так и по масштабу, наблюдались в январе 2007, 2009 гг.и в июле 2003, 2004 гг.В январе 2009 г. это привело к понижению площади ледового покрова в Охотском море.В июле 2003 г. вторжение арктического воздуха и его длительное пребывание над Охотским морем замедлило прогрев поверхностного слоя воды, а в июле 2004 г. вторжение тихоокеанского воздуха привело к значительным положительным аномалиям температуры поверхности океана (ТПО).Помимо оценки аномалий проведён гармонический анализ сезонных вариаций приземного атмосферного давления.При анализе пространственного распределения амплитуды годовой гармоники выявлена узкая область с низкими значениями, разделяющая зоны с различным характером годовых вариаций над материком (максимумзимой, минимум -летом) и Тихим океаном (противоположная динамика).Вблизи восточного побережья Сахалина имеется точка, в окрестности которой фаза этой составляющей изменятся на 360°, -аналог амфидромии в теории приливов.При этом над материком фаза изменяется слабо, а вдоль границы раздела между областями с различным характером годового хода -очень резко.Амплитуда полугодовой гармоники невелика над материком и возрастает над океаном

Институт морской геологии и геофизики ДВО РАН Южно-

Based on the analysis of oceanographic survey materials and sea surface temperature satellite observations, the conditions of formation and characteristics of the anticyclonic eddy located in the region of the South Kuril Islands in the spring of 1999 were studied. It was shown that it separated from the subarctic front as result of its interaction with the Oyashio current stream in the second half of March and ceased to exist in mid-June, which is also confirmed by observations of the concentration of chlorophyll-a. In contrast the eddies formed as a result of meandering of the warm Kuroshio and Tsugaru currents, the eddy core, located at depths of 150–300 m, was characterized by lower values of temperature and salinity (4°–4.6°С and 33.55–33.65 е.п.с.) and low current velocities ( about 10 cm/s). The eddy was rather weakly distinguished in the density field both on horizontal and vertical distributions, as well as according to satellite altimetry data.

As a result of an analysis of the long-term average salinity distributions at four standard sections of the Aniva Bay, it was shown that in the late autumn (November-December) there was an inflow of modified Amur low-salinity water along its eastern shore. According to the results of two oceanographic surveys performed on October 29-31, 2013 and November 29-03, 2013, a large-scale desalination in the northeastern part of the bay occurred in conditions of extreme river flow, much earlier than usual, was revealed. A year earlier, instrumental measurements of temperature and salinity revealed the appearance of this water in the area (salinity decreased to 27.5 psu) at the beginning of December 2012 it retained its influence until mid-March 2013. The revealed feature makes it necessary to consider the ecological habitats of certain species of aquatic organisms in the area in a different way.