Variations in the Black Sea water salinity from its latest salinization to the present state: Estimation based on mathematical modeling

The available published data were used to reveal the principal conditions and factors that control the formation and evolution of the Black Sea water salinity. Formalization of the major processes that contribute to the formation of sea salinity structure enabled, based on the present-day data on water balance, the reproduction of profiles of water salinity and the coefficient of vertical water exchange K _Z after 2, 4, 6, 8, and 10 ka since the beginning of water exchange with the Sea of Marmara through the Bosphorus. The time during which the present-day profile of the Black Sea water salinity had formed was evaluated. The results of simulation for different formation stages of the Black Sea salinity structure were used to determine the major ways of salt input into the sea (with river runoff and waters of the Lower Bosphorus Current) and its removal from the sea (the Upper Bosphorus Current). It was established that the Black Sea water salinity regime has virtually attained a stationary state.Translated from Vodnye Resursy, Vol. 32, No. 2, 2005, pp. 154–164.Original Russian Text Copyright © 2005 by Leonov.     

Some Environmental Consequences of Soil Dumping in the Black Sea as a Result of Dredging Operations in Kerch Strait

The results of monitoring performed by Southern Research Institute of Marine Fisheries and Oceanography (YugNIRO) in 1990–1998 in the course of dredging operations with dumping in the Black Sea of soils dredged in Kerch Strait are analyzed. The study covered the soil physical properties and particle size distribution; the extent of the soil pollution by heavy metals, oil products, and organochlorine compounds; the amounts of such pollutants delivered into the sea with these soils; the extent of pollution of water and bottom sediment in the zone of soil dumping offshore Kerch Strait. The amounts of pollutants entering the Black Sea as a result of soil dumping are compared with those entering the sea from other pollutant sources, and the extent of environmental pollution in the dumping zone is compared with the background level of the sea pollution. The admissible rates of soil dumping are estimated, and potential consequences of this process are predicted.     

Salinity‐induced increase of the hydraulic conductivity in the hyporheic zone of coastal wetlands

In coastal zones globally, salinization is rapidly taking place due to the combined effects of sea level rise, land subsidence, altered hydrology, and climate change. Although increased salinity levels are known to have a great impact on both biogeochemical and hydrological processes in aquatic sediments, only few studies have included both types of processes and their potential interactions. In the present paper, we used a controlled 3‐year experimental mesocosm approach to test salinity induced interactions and discuss mechanisms explaining the observed hydrological changes. Surface water salinity was experimentally increased from 14 to 140 mmol Cl per L (0.9 and 9 PSU) by adding sea salt which increased pore water salinity but also increased sulfate reduction rates, leading to higher sulfide, and lower methane concentrations. By analyzing slug test data with different slug test analysis methods, we were able to show that hydraulic conductivity of the hyporheic zone increased 2.8 times by salinization. Based on our hydrological and biogeochemical measurements, we conclude that the combination of pore dilation and decreased methane production rates were major controls on the observed increase in hydraulic conductivity. The slug test analysis method comparison allowed to conclude that the adjusted Bouwer and Rice method results in the most reliable estimate of the hydraulic conductivity for hyporheic zones. Our work shows that both physical and biogeochemical processes are vital to explain and predict hydrological changes related to the salinization of hyporheic zones in coastal wetlands and provides a robust methodological approach for doing so.     

Biochemical Study of Brackish-Water Marine Ecosystems

The concentrations and the elemental and biochemical composition of dissolved and particulate organic matter (OM) characteristic of southern and Arctic seas are presented. The rate of OM transformation in the production–decomposition cycle and that of the phosphate cycle are estimated from the activity of the redox enzymes of the electron-transport system and that of phosphatase. Carbohydrates and protein are shown to be the main biochemical components in the water of all the seas under study in dissolved and particulate OM, respectively. The contribution of carbohydrates to particulate OM under the conditions of intense primary production is demonstrated to be comparable to that of protein. High concentrations of lipids are shown to be characteristic of the coastal ecosystems in the middle Caspian Sea and northwestern shelf of the Black Sea because of severe pollution in these areas. It is noted that at higher trophic levels, the ecosystem of the Caspian Sea intensely assimilates allochthonous OM, and that the Black Sea ecosystem transfers considerable amounts of OM to the hydrogen sulfide zone.     

Hydrochemical Characteristics of the Aral Sea in 2012–2013

The decrease in Aral Sea area, which started in the 1960s, caused considerable changes in the hydrological, chemical, and biological structure of sea water. Regular observations of Aral water chemistry ceased in the early 1990s. There were no observations of the concentrations of biogenic element compounds in water (the so-called “first-day analyses”). During expeditions of the Institute of Oceanology, RAS, in September 2012 and October 2013, integrated hydrochemical observations were carried out, including measuring the concentrations of biogenic element compounds, dissolved oxygen, hydrogen sulfide, and carbonate equilibrium components. An objective of this study was to develop methods of hydrochemical studies under high water salinity (mineralization). In addition to the standard hydrochemical complex, water samples were taken to determine total water mineralization and the concentration of dissolved and suspended metal forms. The results of these studies are given.     

Formation of fish kills and anaerobic conditions in the Sea of Azov

Results of field observations and numerical modeling of hydrogen sulfide pollution of the Sea of Azov in 2001 are presented.Translated from Vodnye Resursy, Vol. 32, No. 2, 2005, pp. 171–183.Original Russian Text Copyright © 2005 by Debolskaya, Yakushev, Sukhinov.     

Natural Tritium as an Indicator of Changes in the Vertical Structure of Caspian Sea Water Mass with Sea Level Variations

Analysis of changes in the vertical distribution of tritium in the Caspian Sea water mass in 1994–1996 led to a conclusion that the sea level fall that started in 1996 was accompanied by a rearrangement of the water mass steady hydrological structure characteristic of the high sea-level stand.__________Translated from Vodnye Resursy, Vol. 32, No. 4, 2005, pp. 406–409.Original Russian Text Copyright © 2005 by Brezgunov, Ferronskii.     

Global geoenvironmental problems: Black Sea basin

The issue of the geoenvironmental state of Black Sea basin, the final basin receiving the runoff of many large rivers of the European continent (Danube, Dnieper, Don, etc.) and considerable runoff from the nearby watersheds, including Turkish, is considered. The extent and geoenvironmental consequences of the large-scale changes in the hydrology, water balance, and hydrochemistry of the sea basin under the effect hydrotechnical interception and industrial pollution of river runoff are discussed. The genetic role of Black Sea rifting in one of the world’s largest oil-and-gas-bearing basins with its inherent thermal and geochemical processes, geoenvironmental conditions, and risks is emphasized. Improved information is given about the genesis of hydrogen sulfide dissolved in seawater and related to the processes of geochemical sulfate reduction of silt water sulfates under the effect of hydrocarbon gases, which mostly form in zones of deep catagenesis of sedimentary formations and lower crust rock metamorphism. It is emphasized that the ecological stability of a sea basin showing such complex and contradictory relationships with natural and technogenic objects and processes can be ensured only by joint and well coordinated efforts of the countries of the Black Sea and nearby regions aimed on rational nature and water management, including when laying pipelines on Black Sea bed and developing the power resources of the Black Sea oil-and-gas-bearing basin.     

Current Desalination of the Sea of Azov and Its Correlation with Long-Term Variations in Atmospheric Circulation

Correlation is established between the long-term variations in the frequency of the atmospheric circulation forms, water balance elements, and the Sea of Azov water salinity. It is found that the river runoff into the sea and the sea freshwater balance increase and the sea salinity decreases in the periods, when northern and western forms of atmospheric processes develop; in the periods with a greater frequency of the eastern type of atmospheric macroprocesses, the situation is reverse. It is also found that the effect of atmospheric circulation on the sea salinity tends to strengthen, whereas the effect of the human-induced decrease in river runoff tends to diminish. The current desalination of the Sea of Azov down to 10.5 is shown to be mainly due to the development of western and northern forms of atmospheric circulation in the cold season of a year during the last 10–15 years.     

Hydrochemical and Microbiological Features of Lake Mogil'noe

A comprehensive hydrochemical and microbiological study was conducted in Lake Mogil'noe. The vertical hysrochemical structure of the lake was analyzed. Large amounts of mineral compounds containing biogenic elements and their organic forms are shown to accumulate in the anaerobic zone of the lake. An abrupt increase in the concentration of C_org is recorded in the near-bottom layer, where it is almost an order of magnitude higher than that in the anaerobic zone of the Black Sea at a depth of 2000 m. All the processes are found to be most rapid in the boundary layer between the aerobic and anaerobic zones (8.25–9.25 m), where the primary production attains its maximum, the concentration of sulfates abruptly increases relative to the aerobic and anaerobic zones, microorganism population is maximum, as are the rates of sulfate reduction and glucose consumption by heterotrophic organisms.     

Air-sea Coupling During the Tropical Cyclones in the Indian Ocean: A Case Study Using Satellite Observations

In the years 1999 and 2001, three intense tropical cyclones formed over the northern Indian Ocean—two over the Bay of Bengal during 15–19 and 25–29 October, 1999 and one over the Arabian Sea during 21–28 May, 2001. We examined the thermal, salinity and circulation responses at the sea surface due to these severe cyclones in order to understand the air-sea coupling using data from satellite measurements and model simulations. It is found that the Sea Surface Temperature (SST) cooled by about 0.5 °–0.8 °C in the Bay of Bengal and 2 °C in the Arabian Sea. In the Bay of Bengal, this cooling took place beneath the cyclone center whereas in the Arabian Sea, the cooling occurred behind the cyclone only a few days later. This contrasting oceanic response resulted mainly from the salinity stratification in the Bay of Bengal and thermal stratification in the Arabian Sea and the associated mixing processes. In particular, the cyclones moved over the region of low salinity and smaller mixed layer depth with a distinct mixed layer deepening to the left side of the cyclone track. It is envisaged that daily satellite estimates of SST and Sea Surface Salinity (SSS) using Outgoing Longwave Radiation (OLR) and model simulated mixed layer depth would be useful for the study of tropical cyclones and prediction of their path over the northern Indian Ocean.     

Characteristics of the Ecosystems of Water Bodies Separating from Kandalaksha Bay of the White Sea

The coastal water bodies that separate from White Sea water area due to Kandalaksha coast rise are examined. The hydrological and hydrochemical characteristics of these water bodies are found to notably differ from these in the bays and straits connected with them. Extreme values of water temperature and salinity were recorded. High concentrations of oxygen (>20 mg/l) were recorded in the near-surface water layers and high concentrations of hydrogen sulfide (>90 mg/l) in bottom waters. The species composition of phyto- and zooplankton was found to be poor. The characteristics of enzymatic destruction in subsurface waters of lakes are an order of magnitude greater than those in White Sea open areas.     

Surface heat fluxes and thermohaline variability in the Ross Sea and in Terra Nova Bay polynya

The Ross Sea is an important area for the ventilation of the deep layers of the Southern Ocean (e.g. [Jacobs, S.S., Fairbanks, R.G., Horibe, Y., 1985. Origin and evolution of water masses near the Antarctic continental margin: evidence from H218O/H216O ratios in seawater. In: Jacobs, S.S. (Ed.), Oceanology of the Antarctic Continental Shelf. Antarctic Research Series, vol. 43. pp. 59–85; Orsi, A.H., Johnson, G.C., Bullister, J.L., 1999. Circulation, mixing, and the production of Antarctic bottom water. Progress in Oceanography 109, 43–55]). These processes are driven by the atmospheric forcing which, at high latitude, plays a key role in the formation and thickness of sea ice. In order to investigate the effect of the atmospheric forcing variability at different time scales, we analysed the surface heat budget over the Ross Sea continental shelf and in Terra Nova Bay (TNB) polynya, using analyses for the period 1990–2006 provided by European Centre for Medium-range Weather Forecast (ECMWF). This study was also performed using thermohaline data collected within the activities of Climatic Long-term Interaction for the mass-balance in Antarctica project of the Italian National Programme for Antarctic Research for the summer periods from 1994 until 2001.The annual average of the heat budget over the continental shelf of the Ross Sea estimated in the period 1990–2006 shows an interannual variability ranging between −97 and −123 W m⁻². Assuming that the heat loss must be compensated by the sensible heat carried by the Circumpolar Deep Water we estimated its transport (3.1 Sv) and its variability (0.2 Sv). Similarly in the TNB polynya the heat loss reaches its maximum in 2003 (−313 W m⁻²) and its minimum (−58 W m⁻²) in 1996. The related production of sea ice and the High Salinity Shelf Water (HSSW) were also estimated. The HSSW production switched from the lowest values during the first 10 years of the investigated period (1990–2000) to the highest values for the remaining period (2001–2006).The thermohaline characteristics of the water column in TNB show a general decrease in salinity with a superimposed variability. Comparison between the estimated HSSW production and the salinity observed within the TNB water column show similar tendency in the last years after 2002, while during the period 1995–1998 the behaviour is different. Our hypothesis concern a possible role of the CDW inflow in the TNB area and our results could be explained by a different contribution of CDW transport and HSSW production to the salt content within the water column.     

Oceanography of coastal and riverine waters around Timika, West Central Irian Jaya, Arafura Sea

Oceanographic studies have been carried out in coastal and riverine waters of the area around Timika, West Papua in November 1999, March–April, July and November 2000. The temperature of the seawater along the coast is around 28 °C in winter (November 99), rising to 30.0 °C (November 00). In the open sea, 30 miles off the coast at 40 m water depth, the temperature is >30 °C with no stratification. Water temperature near the coast is consistently lower than in the open sea. This is thought to be due the cooling effect of the land, being densely covered by mangrove forest. In the upper parts of the Kamora, West Tipuka, East Tipuka, Ajkwa, Minajerwi, Mawati and Otakwa Rivers, at salinity zero psu, water temperature varies between 24.6 and 26.2 °C, which is as cold as the temperature in the upwelling Banda Sea to the NW. Some of these rivers are fed by glacial melt water from the high mountains to the east. At mid estuary, warm seawater is found under the cooler river water.Salinity near this coast varied between 24 and 30, and offshore salinity was 31–33 with no stratification. Inshore surface waters were turbid (11–14 ntu), and near bottom waters were generally much more turbid from river sediment supply and tidal resuspension. The Ajkwa River estuary has the highest turbidity (750 ntu) at zero salinity. Offshore waters were very clear (5.0–6.0 ntu), and there was no increase in turbidity near the bottom.     

Prediction of water salinity in the Yumaguzinskoe Reservoir under construction

Factors responsible for the formation of water salinity in the Yumaguzinskoe Reservoir, which is under construction in the upper reaches of the Belaya River, are analyzed. Based on the prediction experience and a sufficient amount of initial data on water quality of the Belaya River, the universally accepted algorithm of prediction for years of different water supply levels using the calculation method of running-out has been modified. As revealed, the minimum water salinity at the reservoir spillway is observed in May–August, the maximum water salinity being in January–March. The regularities of a general nature have been found.Translated from Vodnye Resursy, Vol. 32, No. 2, 2005, pp. 214–222.Original Russian Text Copyright © 2005 by Popov, Oboldina.     

Variability of dense water formation in the Ross Sea

This paper presents results from a model study of the interannual variability of high salinity shelf water (HSSW) properties in the Ross Sea. Salinity and potential temperature of HSSW formed in the western Ross Sea show oscillatory behaviour at periods of 5–6 and 9 years superimposed on long-term fluctuations. While the shorter oscillations are induced by wind variability, variability on the scale of decades appears to be related to air temperature fluctuations. At least part of the strong decrease of HSSW salinities deduced from observations for the period 1963–2000 is shown to be an aliasing artefact due to an undersampling of the periodic signal. While sea ice formation is responsible for the yearly salinity increase that triggers the formation of HSSW, interannual variability of net freezing rates hardly affects changes in the properties of the resulting water mass. Instead, results from model experiments indicate that the interannual variability of dense water characteristics is predominantly controlled by variations in the shelf inflow through a sub-surface salinity and a deep temperature signal. The origin of the variability of inflow characteristics to the Ross Sea continental shelf can be traced into the Amundsen and Bellingshausen Seas. The temperature anomalies are induced at the continental shelf break in the western Bellingshausen Sea by fluctuations of the meridional transport of circumpolar deep water with the eastern cell of the Ross Gyre. In the Amundsen Sea, upwelling due to a persistently cyclonic wind field carries the signal into the surface mixed layer, leading to fluctuations of the vertical heat flux, anomalies of brine release near the sea ice edge, and consequently to a sub-surface salinity anomaly. With the westward flowing coastal current, both the sub-surface salinity and deep temperature signals are advected onto the Ross Sea continental shelf. Convection carries the signal of salinity variability into the deep ocean, where it interacts with modified circumpolar deep water upwelled onto the continental shelf as the second source water mass of HSSW. Sea ice formation on the Ross Sea continental shelf thus drives the vertical propagation of the signal rather than determining the signal itself.     

S, O and Sr isotope systematics of active vent materials from the Mariana backarc basin spreading axis at 18°N

Stable isotope ratios of S, O and Sr have been measured for active vent materials which were first found and sampled in April 1987 from the Mariana backarc spreading axis at 18°N. Chimneys consisted mostly of barite with a lesser proportion of sulfide minerals such as sphalerite, galena, chalcopyrite and pyrite. Theδ³⁴S values of sphalerite and galena taken from several chimneys and various parts of a chimney showed a narrow range from 2.1 to 3.1‰, suggesting uniform conditions of fluid chemistry during chimney growth. The sulfur isotopic results imply a contribution of hydrogen sulfide reduced from seawater sulfate in the deep hydrothermal reaction zone, considering that fresh glasses of the Mariana Trough basalts haveδ³⁴S= −0.6 ± 0.3‰. Sulfur isotopic compositions of hydrogen sulfide in the high temperature vent fluids (δ³⁴S= 3.6–4.8‰) which are higher than those of the sulfide minerals suggest the secondary addition of hydrogen sulfide partially reduced from entrained seawater SO₄²⁻ at a basal part of the chimneys. This interpretation is consistent with theδ³⁴S values of barite (21–22‰) that are higher than those of seawater sulfate. The residence time of the entrained SO₄²⁻ was an order of an hour on a basis of oxygen isotopic disequilibrium of barite. Strontium isotopic variations of barite and vent waters indicated that Sr in barite was mostly derived from the Mariana Trough basalts with a slight contribution from Sr in circulating sea-water, and that 10–20% mixing of seawater with ascending hydrothermal fluids induced precipitation of barite at the sea-floor.     

Hydrological and Morphological Processes in the Kura River Delta

Peculiarities of the development of the Kura Delta over the last 200 years are discussed. As shown, changes in the delta were greatly affected by the Caspian Sea level drop during 1929–1977 and its rise during 1978–1995 as well as by natural and human-induced variations in the water and sediment runoff of the river. It was noted that the delta area decreased by nearly 40% as a result of the sea level rise. The following significant changes in the Kura Delta were revealed in recent years using space images: river water rushed through the right mouth spit and, hence, the main Southeastern Branch was devoid of its flow and a new sea spit began its formation in the branch mouth using wave-cut products.     

Probabilistic Estimates of Water Level in the Ural River Mouth Reach at Interaction between the River Runoff and Positive Setups

A probabilistic technique is developed for assessing water level in the mouth reach of the Ural River in the course of interaction between the river runoff and irregular rises in the Caspian Sea level (positive setups) at the predicted background sea levels of –26.5 and –26.0 m abs.     

Seasonal variations in thermo-, halo-, and pycnocline in the northeastern part of the Black sea (Based on long-term data)

Seasonal evolution of the vertical thermal, halininc, and density structure of water in the phases of warming and heat loss is shown. The annual cycle of variability of seasonal and deep-water thermo-, halo-, and pycnocline is discussed. It is revealed that variations in the seasonal (subsurface) thermo-, halo-, and pycnocline depend on the surface environmental factors (air temperature, river runoff, and precipitation), while variations in the deep-water thermo-, halo-, and pycnocline depend on the dynamic factor impact (seasonal variations in the intensity of the general cyclonic circulation in the Black Sea).Translated from Vodnye Resursy, Vol. 32, No. 1, 2005, pp. 28–34.Original Russian Text Copyright © 2005 by Titov.