DEVELOPMENT OF AN EMPIRICAL MODEL OF pH LONG-TERM CHANGES IN THE SURFACE WATERS OF THE DEEP-WATER PART OF THE BLACK SEA

The paper analyzes the interannual variability of the pH value in the surface layer of the deep-water part of the Black Sea for the period from 1957 to 1996. For the period from 1977 to 1996, an empirical mod-el of the time series is developed and a retrospective forecast is calculated with an assessment of its quali-ty using data from field studies performed from 2019 to 2021. In the interannual course of pH, two sig-nificant quasi-cyclic components of variability with periods of about 6, 7 years and 2.5 years are distin-guished. The highlighted trend (climate trend) indicates a decrease in the pH value for the period from 1977 to 2021. with an average rate of about 0.01 pH units/10 years. The data of field studies in 2019-2021 confirm the calculations obtained.

Deep-water part of the Middle Caspian Sea as a promising area of operation of the Caspian sprats

The article presents the results of hydroacoustic studies of the deep-water part of the Middle Caspian Sea in the summer period 2019-2020. The spatial distribution in the studied water area and the ratio of biomass in the upper 50-meter layer are presented. Shows typical of echogram the records of sprats.

NUMERICAL SIMULATION AND FIELD STUDIES OF THERMAL BAR IN LAKE TELETSKOE

A computer three-dimensional (3D) hydrothermodynamic model was designed for refined description of intra-annual temperature stratification in deep freezing Lake Teletskoye. The work is aimed at testing this model through simulation of a complex hydrophysical phenomenon, i.e. spring thermobar for real conditions of Lake Teletskoye. In June 2018, while performing field observations of temperature stratification in Lake Teletskoye, a thermobar (stretching from the mouth of the Chulyshman River at the lake’s southern tail up to its deep-water part) was detected and studied. Using the constructed 3D model of thermal regime and actual input data for 2018, the estimate of spring-summer thermobar in the water body as well as the comparative analysis of numerical simulation results and field observation data were made.

Changes in the Oxygen Regime in the Deep Part of the Black Sea in 1980–2019

Purpose. Assessing changes in the oxygen regime of the deep-water part of the Black Sea under the influence of climatic and anthropogenic factors over the past 40 years is the goal of the work. Methods and Results. For the analysis, the expedition data (2015–2019) and those from the Databank of the Marine Hydrophysical Institute, Russian Academy of Sciences, (1980–2013) were used. The data for the deep-water part of the Black Sea (the depths exceeding 200 m) were selected from the array. The data on hydrophysical and hydrochemical parameters were subjected to expert assessment, and those including random errors in the values were excluded from the array. Then the average profiles of temperature, salinity, oxygen concentration, oxygen saturation, and nitrates concentration were plotted in the density scale (σt). Averaging was carried out by the inverse distance method followed by additional smoothing by the low-frequency filtering method. Conclusions. Against the background of the tendency of temperature increase in the upper layers of the water column and decrease of winter convective mixing intensity, the oxygen supply diminishes in all the layers of the Black Sea aerobic zone. Having been analyzed, of the data for the 1980–2019 period showed that at the present stage, a "regime shift" resulting from the joint effect of climate changes and anthropogenic load took place in the ecosystem of the deep-water part of the Black Sea. Decrease in the oxygen saturation of water throughout the entire thickness of the aerobic zone shows that the process of the Black Sea basin eutrophication constitutes a significant factor affecting oxygen dynamics in the Black Sea waters.

Changes in the Oxygen Regime in the Deep Part of the Black Sea in 1980–2019

Purpose. Assessing changes in the oxygen regime of the deep-water part of the Black Sea under the influence of climatic and anthropogenic factors over the past 40 years is the goal of the work. Methods and Results. For the analysis, the expedition data (2015–2019) and those from the Databank of the Marine Hydrophysical Institute, Russian Academy of Sciences, (1980–2013) were used. The data for the deep-water part of the Black Sea (the depths exceeding 200 m) were selected from the array. The data on hydrophysical and hydrochemical parameters were subjected to expert assessment, and those including random errors in the values were excluded from the array. Then the average profiles of temperature, salinity, oxygen concentration, oxygen saturation, and nitrates concentration were plotted in the density scale (σt). Averaging was carried out by the inverse distance method followed by additional smoothing by the low-frequency filtering method. Conclusions. Against the background of the tendency of temperature increase in the upper layers of the water column and decrease of winter convective mixing intensity, the oxygen supply diminishes in all the layers of the Black Sea aerobic zone. Having been analyzed, the data for the 1980–2019 period showed that at the present stage, a “regime shift” resulting from the joint effect of climate changes and anthropogenic load took place in the ecosystem of the deep-water part of the Black Sea. Decrease in the oxygen saturation of water throughout the entire thickness of the aerobic zone shows that the process of the Black Sea basin eutrophication constitutes a significant factor affecting oxygen dynamics in the Black Sea waters.

About Relations between Natural Gas and Oil in Connection with Forecast of Their Reserves in Azerbaijan

Azerbaijan is one of the oldest oil and gas provinces, where more than 2 bln tons of oil have been extracted over more than a century. At present, the oil production is declining and mainly determined by production from the Azeri-Chirag-Guneshli offshore block (AChG). Compared to oil, the opportunities for further growing natural gas reserves and production are very promising. For the latest years, a number of large gas condensate fields have been discovered in the deep-water part of South Caspian Sea, such as Shakh-Deniz, Apsheron, Umid. There are a number of prospects that have not yet been drilled in this part of the sea basin. The paper assesses their prospectivity, substantiates the priority exploration targets and, on the basis of the statistical analysis of the quantitative gas/oil ratio data for many other Azerbaijanian and world basins, an attempt is made to assess the reserves in the prospects. The total recoverable oil reserves in Azerbaijan are estimated at 3.5 bln tons, of which slightly above 2 bln tons have already been extracted. Based on the statistically estimated ratio between the volumes of gas and oil in various basins of the world, including Azerbaijan, the total possible natural gas reserves in Azerbaijan are estimated at about 4 trillion m3 . This is in agreement with the other available estimates. Of this volume of natural gas, 0.85 trillion m3 has already been extracted, and the approved geological reserves are estimated at 2.55 trillion m3 . Almost 83% of the extracted natural gas belonged to offshore fields. This trend will continue in the future, and, moreover, will be strengthened due to large volumes of gas condensate accumulations in the deepwater part of the basin. In this part of the basin, the most attractive prospects are Mashal, Shafag, and Israfil Huseynov, total reserves of which are expected at 0.6 trillion m3 of natural gas.

Mud-volcanic deposits of methane gas hydrates in the Black Sea

This paper discusses the formation of a special mud-volcanic type of gas hydrate accumulation in the deep-water part of the Black Sea. The main conclusions are based on the results of geological and geophysical studies of mud volcanoes carried out in the course of numerous scientific cruises between 1970-2015. Comparison of the Black Sea submarine mud volcanoes with their on-land analogues indicates the possible use of compensatory depressions, called “recessed synclines”, accompanying mud volcanoes, which is revealed in the course of prospecting and exploration of mineral deposits. In the sea they are represented by ring deposits of methane gas hydrates.

Sedimentary basins of the East Siberian sea and the Chukchi sea region and the adjacent area of Amerasia basin: seismic stratigraphy and stages of geological history

The seismic stratigraphy scheme for the shelf basins of the East Siberian Sea and the Chukchi Sea region and the adjacent deep-water part of the Amerasia basin has been developed, and mega-sequences (or tectonostratigraphic units) with proposed age of 125100, 10080, 8066, 6656, 4645, 4534, 200 Ma are distinguished. Zhokhov foredeep basin of the Late Jurassic‒Neocomian age is distinguished between the New Siberia and De Long islands. Three main phases of rifting are identified on the shelves in the region with ages of 125100, 6656 and 4537 Ma. The main phase of continental rifting occurred in the Podvodnikov and Toll basins 125100 Ma. The typical clinoform accumulation of sediments occurred at the edge of the shelf 6620 Ma. We identified three syntectonic epochs of the formation of clinoform complexes with ages of 6645, 4534 and 3420 Ma. The phase of uplifting and compression in the region of Wrangel Island happened 66 Ma. The relatively monotonous tectonic setting with approximately the same thickness of the sedimentary cover began from 20 Ma.