The performance of the Black Sea Commission as a collaborative governance regime

It is often claimed that the Black Sea is one of the most degraded seas in the world. Management to rehabilitate the Black Sea requires cooperation between the coastal countries to be successful. However, regional cooperation in the Black Sea is poorly coordinated and lack concrete outcomes. This article analyses the performance of the Black Sea Commission in terms of enabling and fostering effective regional collaboration between the Black Sea coastal countries. The results indicate that the measures undertaken by the Black Sea Commission are effective in terms of enabling scientific and project based cooperation between the Black Sea countries. The cooperation around regional and national institutional reforms to tackle the Black Sea environmental problems is found to be weak. Despite the existing mechanisms and willingness of countries to cooperate, the implementation of the established strategic action plan for the environmental protection and rehabilitation of the Black Sea is limited. Most of the limitations of the Black Sea Commission's regime are found in its institutional and legal frameworks, which constrain the effectiveness of collaborative efforts of the Black Sea countries. To be fully functional, the collaborative governance regime of the Black Sea Commission has to be improved. Recommendations as to how these may be addressed to enhance the regime's capacity to ensure effective marine collaborative governance in the region are presented in this article.     

Viscous model of plate tectonics for the Black Sea region (in relation to the problem of the late Cenozoic evolution of the Black Sea basins)

A numerical model of the Black Sea region (Northeastern Mediterranean) is presented in which it is regarded as a part of the mosaic plate ensemble consisting of the fixed East European platform; the active Arabian, Adriatic, and Pannonian plates; and passive East and West Black Sea and Mysian microplates, which are embedded in a plastically deformable regional orogenic matrix. The fields of displacements, stresses, and deformations in the region are calculated by means of the finite element method within the framework of a linear-viscous rheology approach to a system with nonhomogeneous viscosities. The velocity field obtained is in good agreement with published data of direct observations of plate displacements in the region. In the pressure field, areas of low pressure and decompression are established in the western part of Black Sea and in the south of the Mysian microplate. The poles of rotation of the East and West Black Sea microplates and of the Mysian microplate are computed. For the latter two microplates, significant rotational components are suggested. The East Black Sea microplate acts mostly as indenter, which transmits the collisional motion from the Arabian plate to the southern edge of the East European platform including the Crimea. According to the geodynamical model, the rates of the Cenozoic sedimentation in the Black Sea depression at the collision stage (Oligocene-Pliocene) result from the greater compression of the East Black Sea microplate as compared to the West Black Sea microplate, which, probably, experienced a kind of extension.     

Radioactive isotopes of caesium in the waters and near-water atmospheric layer of the Black Sea

The concentrations of¹³⁷Cs and¹³⁴Cs were measured using the sorption method in the waters of the Black Sea during 1986–1987. An inhomogeneous character of the contamination of the surface waters in the Black Sea due to the Chernobyl disaster is shown. The subsequent migration and redistribution of caesium radionuclides in the various seasons of the year were studied. The amount of¹³⁷Cs and¹³⁴Cs in the upper 50 m layer was estimated. The results of measuring the concentration of caesium radionuclides in the near-water atmospheric layer over the Black Sea and Mediterranean Sea in 1986–1987 are also reported.Translated by Mikhail M. Trufanov.     

Satellite monitoring of oil slicks on the Black Sea surface

This paper summarizes the results of perennial combined satellite monitoring of the Black Sea conducted in order to detect sea-surface oil and oil-product pollution, as well as biogenic and anthropogenic surfactant films. A joint analysis of data obtained by various remote sensing techniques has been performed. The large amount of data has resulted in generalizations and reliable statistics on the spatial and temporal variability of different film manifestations in radar images of the sea surface. Regions most severely polluted by petroleum products have been identified. A hypothesis is suggested linking the surface manifestations of certain types of polluting films with natural gas and oil seeps and mud volcanism in the Black Sea. Improvements in the reliability of interpreting satellite data are discussed.     

Study of long-term variations in the Black Sea fields using an interdisciplinary physical and biogeochemical model

Using an interdisciplinary three-dimensional physical and biogeochemical model developed for the Black Sea, the long-term evolution of marine dynamics and ecosystem is investigated. The hydrophysical fields were calculated from a model of Black Sea circulation with assimilation of hydrographic survey and satellite measurement data from 1971 to 2001. The circulation model reproduces well processes of various scales in both space and time (particularly the seasonal course and interannual variability of main hydrophysical fields). The resulting flow fields are then used to calculate the long-term evolution of the components of the lower level of the food chain in the Black Sea ecosystem. The biogeochemical model used in the calculations is based on the nitrogen cycle and includes a parameterization of the main biological and chemical interactions and processes in the upper layer of the Black Sea. The numerical experiments indicated that the biogeochemical component of the model rather successfully reproduces the main features and evolution trends in the Black Sea ecosystem for the period under consideration: the growth in the phytoplankton biomass during eutrophication and changes in seasonal cycles of the main ecosystem components. Also, the hydrophysical processes were shown to be important for a reliable reproduction of long-term changes in the ecosystem.     

Thermal evolution of the lithosphere of buried structures of the deep-water basin of the Black Sea

The GALO system for basin modeling is applied for numerical reconstruction of the thermal history of the lithosphere of the Western Basin and the Shatsky and Andrusov rises in the Black Sea. The modeling showed that the variant of the thermal evolution of the lithosphere of the region that was used by us for the Eastern Basin in our previous study is also applicable to the thermal evolution of the lithosphere of various tectonically different structures of the deep-water part of the Black Sea. These structures include both the Western and Eastern basins of the sea characterized by a granite-free crust formed in the course of the back-arc spreading and the Shatsky and Andrusov rises with the continental type of crust. The proposed version of the lithosphere evolution in the deep-water part of the Black Sea implies the initial stage of quasi-rift heating in the Upper Cretaceous and the three-staged thermal activation of the plate in the Cenozoic accompanied by three successive stages of crustal thinning. The latter resulted in the gradual deepening of the sea down to the present-day depth of 2.2 km.     

Analysis of the Black Sea sediments by evaluating DSDP Leg 42B drilling data for gas hydrate potential

Many gas seepages, temperature, pressure, salinity, anoxic environment and high source gas potential of the Black Sea indicates that the Black Sea might have huge potentials for biogenic and thermogenic gas hydrates. However, the last important parameter to consider gas hydrate as an energy source is the type of sediments. Coarse marine sands are considered as good hydrate reservoirs because of high porosity and high permeability. Only very limited data is available related to the types of lithology of the Black Sea sediments. Hence, in this study, the literature data (especially the drilling and coring data of DSDP Leg 42B program) about gas seepages, temperature gradient, pressure gradient, salinity, anoxic environment and high source gas potential, and the types of the sediments in the Black Sea were investigated and analyzed. Although gas seepages, temperature gradient, pressure gradient, salinity, anoxic environment and high source gas potential of the Black Sea are appropriate for producible gas hydrate reservoirs, the sediments of the Black Sea appear to be generally fine grained with high clay content. Sandy-silt and silty sand layers in turbidites of the Black Sea might be potential producible hydrate reservoirs but these sediments are fine. As well as turbidites, separate thin sand layers might be potential gas hydrate reservoirs as an energy source in the Black Sea.     

Fate of the Black Sea Acartia clausi and Acartia tonsa (Copepoda) penetrating into the Marmara Sea through the Bosphorus

In October 2005 spatial distribution of live and dead Acartia clausi and Acartia tonsa was studied in the Black and Marmara Seas and near the Marmara Sea inlet of the Bosphorus, in order to understand their fate upon transportation between two seas. The morphometric characteristics in both species from all studied areas, and the decreased abundance of A. clausi and A. tonsa from the Black Sea towards the Marmara Sea indicate that the Marmara Sea Acartia populations are formed by recruitment from the Black Sea. We observed mass mortality of A. clausi in the Marmara Sea near the Prince Islands. The majority of carcasses (66% of total A. clausi numbers in the Marmara Sea) were found in the salinity gradient layer.     

Thermal structure of the crust in the Black Sea: comparative analysis of magnetic and heat flow data

This paper presents the first study of mapping of the Curie point depth (CPD) from magnetic data for the Black Sea and a comparison with a classical thermal modeling from heat flow data. The provided relationship between radially averaged power spectrum of the magnetic anomalies and the depths to the magnetic sources of the Black Sea vary from 22 to 36 km. Deepening of CPDs observed in the western and eastern Black Sea basins correspond with the thickest sediment areas, whereas the shallow CPDs are related to the Mid-Black Sea Ridge and thin sediment areas at the costal side of the Black Sea. For comparison, the temperature field was also modeled from heat flow data from the Black Sea along three approximately north–south directed profiles corresponding to known DSS soundings. The Curie isotherm along the profiles occurs at depths of 22–35 km. A comparison of the results of the two independent methods reveals only 8–10 % discrepancy. This discrepancy is equal to an accuracy of temperature determination from heat flow data.     

Data-computing technologies: A new stage in the development of operational oceanography

An analysis is given of the methods of operational oceanography based on measurements derived from satellite data, observations acquired by drifters and passing vessels, and modern simulations of marine and oceanic circulations. In addition, a historical review is conducted of the previous and current research in this field carried out in the Soviet Union, Ukraine, and Russia. A discussion is given of the principles underlying the design of an effective data-computing system (DCS) for solving the problems of operational oceanography and the implementation of the prototype system for the Black Sea within the joint research project of the Russian Academy of Sciences (RAS) and the National Academy of Sciences of Ukraine (NASU) “The Black Sea as an Ocean Simulation Model.” The effectiveness of applying the multicomponent splitting method in the construction of sea circulation models and specialized DCSs with integrated algorithms of variational assimilation of observational data is estimated. The concept of using the Black Sea as a testing site for innovations is developed. The underlying idea of the concept is the similarity of the Black Sea dynamics with processes in the oceans. The numerical Black Sea circulation models used in the project are described, their development areas are discussed, and the requirements to a Black Sea observing system are defined.     

Water circulation and hydrological structure in the active layer of the 50-mile near-shore zone of the Russian sector of the black sea in August 2004

The water dynamics and hydrological structure in the active (oxygen-containing) layer are considered on the basis of the hydrological survey carried out in the 50-mile near-shore zone of the Russian sector of the Black Sea in August 2004 and over the permanent section from Gelendzhik to the central part of the sea. Five mesoscale eddy structures of different signs were observed in the Main Black Sea Current between Sochi and the Kerch Strait. Such a dynamic situation contributed to the intensive horizontal water exchange between the near-shore and open sea waters as well as to the redistribution of water masses over the vertical in the active sea layer, which is indicated by the deepening of the top boundary of the hydrogen sulfide zone in the Russian sector of the sea by 15–20 m.     

Further evidence of abrupt Holocene drowning of the Black Sea shelf

A 1999 survey of the Black Sea continental shelf off the north central Turkish seaport of Sinop using a side-scan sonar, small remotely operated vehicles, and a series of dredge lowerings located, inspected and sampled an exposed high-energy paleoshoreline at a depth of 155 m. Radiocarbon dating of mollusk shells collected from this ancient beach revealed that the marine flooding of the Black Sea took place between 7460 and 6820 yr B.P. (all ages are reported in radiocarbon years, not calendar years, without correction for reservoir age or dendro-calibration) changing it from a lacustrine to marine environment. This relic surface remained in contact with the bottom waters of the Black Sea for a long period of time before being draped by a thin layer of sapropel mud. Wood samples recovered from this same location were very well preserved and yielded dates as old as 3580 yr B.P.     

Peculiarities of oceanographic processes in the north-western Black Sea

The paper examines how various factors affect the intensity of photosynthesis and oxidation reaction in the north-western part of the Black Sea. In the course of the evolution of the basin, natural aspects were widely changing; therefore their role is evaluated by the content of organic matter and diatoms in the bottom sediments. The influence of anthropogenic factors is determined by the current tendencies in the variation of physico-chemical and biological characteristics of the basin. The main factor upsetting steady functioning of the north-western Black Sea ecosystem is the large biogenic influx to the sea. The possible changing of the ecosystem during the nearest few decades is assessed. Translated by Vladimir A. Puchkin.     

黑海西北部涡旋与环流对跨陆架水交换的影响

涡旋对海洋中的能量传递和物质交换有重要作用。黑海西北部陆坡边缘是长生命周期涡旋经常发生的海域,但涡旋引起的陆架和海盆之间水交换通量的季节性特征,以及海盆边缘环流对跨陆架水交换的作用等方面的研究还不是很充分。本文对黑海西北部陆架区与深海盆区间的跨陆架水交换进行了研究,利用高分辨率三维原始方程模式模拟的温、盐、流等资料,结合涡旋自动探测方法,统计了黑海西北部海域的涡旋活动,研究了涡致跨陆架水交换的季节性特征,计算对比了2002年到2010年间海盆边缘环流与涡旋对跨陆架水交换通量的各自贡献。结果表明:黑海西北部地区海盆边缘环流强度与跨陆架进、出通量的相关系数分别为0.57和0.67,海盆边缘环流位置与跨陆架交换量的相关系数为0.52;海盆边缘环流强度与位置的季节性变化导致了黑海西北部跨陆架通量的季节性变化。黑海西北部地区表层3月到8月之间涡旋所引起跨陆架交换量约占了跨陆架交换总量的16%~31%;涡致跨陆架通量也具有季节性特征。文中对单个涡旋进行了详细研究:2005年5月5日到2005年7月20日之间在黑海西北部存在一个直径最大值时达到120 km的反气旋式涡旋,涡旋存在期间完成了从陆架区向深海区的水体传输,相当于黑海西北陆架区水体积的30.9%。     

Model of palaeoenvironmental evolution of the Black Sea region during the last glacial maximum—Holocene

A model for the palaeoenvironmental evolution of the Black Sea and its adjacent basins during the past 20.000 years, in which variations in sedimentation, erosion, and hydrologic processes as a result of climatic change are taken into consideration, is developed. The data used include those from five cruises in the Black Sea with the participation of the author, seismo-acoustic data in the possession of the Institute of Oceanology in Varna, and data from the published literature. The most important result is that the water level of the Black Sea is controlled largely by that of the Marmara Sea via the Bosporus sill. The water circulation in the south part of the Bosporus channel as natural regulative mechanism of the Black Sea level during 11800–9000 yr C¹⁴ BP is produced. A succession of climatic and water conditions for the Black Sea by pollen analysis is presented. The linear ridges on the Black Sea shelf as result of the lower Holocene regression are proved by means of a stratigraphic interpretation of the seismo-acoustic profiles. The levels of the Black Sea, Marmara Sea, and Mediterranean at regarded intervals of time are presented. An attempt at explanation of maximum number of facts from the study region with this model is made.     

Hydraulic calculations of postglacial connections between the Mediterranean and the Black Sea

A series of simple hydraulic calculations has been performed to examine some of the questions associated with the reconnection of the Black Sea to the Mediterranean through the Turkish Strait System during the Holocene. Ryan et al.’s catastrophic flood scenario, whereby the erosive power of the marine in-fluxes, initiated after eustatic sea level reached the sill depth, opened up the Bosphorus, allowing saline water to pour into the Black Sea and filling it on a short time scale, is examined. The calculations show that although it might be possible to fill the palaeo-Black Sea within the order of a decade, a 1–2 year filling time scale is not physically possible. A hydraulic model is also used to examine the more traditional connection hypothesis of (near-)continuous freshwater outflow from the Black Sea, with a slowly increasing saline inflow from the Mediterranean beginning around 8–9 kyr BP. The model considers two forms for the structure of the Bosphorus: a shallow sill as seen today and a deep sill associated with no sediments filling the 100 m gorge above the bedrock in the strait. Sensitivity experiments with the hydraulic model show what possible strait geometric configurations may lead to the Black Sea reaching its present-day salinity of 18 psu. Salinity transients within the Black Sea are shown as a function of time, providing for values that can be validated against estimates from cores. To consider a deep, non-sediment-filled Bosphorus (100 m deep), the entry of Mediterranean water into the Sea of Marmara after 12.0 kyr BP is examined. A rapid entry of marine water into the Sea of Marmara is only consistent with small freshwater fluxes flowing through the Turkish Strait System, smaller than those of the present day by a factor of at least 4. Such a small freshwater flux would lead to the salinification of the Black Sea being complete by an early date of 10.2–9.6 kyr BP. Thus the possibility of a deep Bosphorus sill should be discounted.     

Peculiarities of the currents field in the north-western part of the Black Sea

On the basis of the results derived by theoretical analysis [1] and laboratory physical modelling [2] of the circulation seawater and stratification, induced by buoyancy fluxes, the suggestion has been made that, possibly, the Black Sea currents system is three-layered. It has been supposed that an anticyclonic current flows in the basin. To verify this deduction, the data from MHI's archived dataset have been treated, and results from twoad hoc expeditions are submitted here. Analysis of the vertical structure of currents, based on thein situ velocity measurements, using various means and calculations of the geostrophic circulation, has confirmed that a flow with the theoretically predicted parameters may exist in the Black Sea. Translated by Vladimir A. Puchkin.     

On the long-term variability of normalized radiance of the Black Sea

Basin-wide distributions of normalized spectral radiances averaged over different time periods were plotted based on the estimates of the average radiance for 20 × 20 km squares in 482 digital images of the Black Sea obtained with a SeaWiFS color scanner in 1998–2004. Significant distinctions of the annual average distributions in the amplitude, localization, and configuration of basin-scale inhomogeneities allowed us to consider these distributions as yearly spectral-radiance portraits of the Black Sea that reflect specific features of the annual behavior of the hydrometeorological conditions over the Black Sea region. Seasonal features of the radiance distributions related to the wind field were discovered. Substantial interannual variability in the errors of the standard atmospheric correction algorithm resulting in an underestimation of the shortwave radiances were revealed. It is shown that the river discharge and the stratification of the layer sensed substantially influence the yearly spectral-radiance portraits of the Black Sea.     

Postglacial floodings of the Marmara Sea: molluscs and sediments tell the story

The early Holocene marine flooding of the Black Sea has been the subject of intense scientific debate since the “Noah’s Flood” hypothesis was proposed in the late 1990s. The chronology of the flooding is not straightforward because the connection between the Black Sea and the Mediterranean Sea involves the intermediate Marmara Sea Basin via two sills (Dardanelles and Bosphorus). This study explores the chronology of late Pleistocene–Holocene flooding by examining sedimentary facies and molluscs from 24 gravity cores spanning shelf to slope settings in the southern Marmara Sea Basin. A late Pleistocene Ponto-Caspian (Neoeuxinian) mollusc association is found in 12 of the cores, comprising 14 mollusc species and dominated by brackish (oligohaline–lower mesohaline) endemic taxa (dreissenids, hydrobiids). The Neoeuxinian association is replaced by a Turritella–Corbula association at the onset of the Holocene. The latter is dominated by marine species, several of which are known to thrive under dysoxic conditions in muddy bottoms. This association is common in early Holocene intervals as well as sapropel intervals in younger Holocene strata. It is an indicator of low-salinity outflows from the Black Sea into the Marmara Sea that drive stratification. A marine Mediterranean association (87 species) represents both soft bottom and hard substrate faunas that lived in well-ventilated conditions and upper mesohaline–polyhaline salinities (ca. 25 psu). Shallower areas were occupied by hard substrate taxa and phytopdetritic communities, whereas deeper areas had soft bottom faunas. The middle shelf part of the northern Gemlik Gulf has intervals with irregular and discontinuous sedimentary structures admixed with worn Neoeuxinian and euryhaline Mediterranean faunas. These intervals represent reworking events (slumping) likely related to seismic activity rooted in the North Anatolian Fault system. The core data and faunas indicate an oscillating postglacial sea-level rise and phases of increased/decreased ventilation in the Marmara Sea during the Holocene, as well as palaeobiogeographic reorganisations of Ponto-Caspian and Mediterranean water bodies since the latest Pleistocene (<30 ka). The findings contribute to arguments against a single catastrophic flooding of the Black Sea at about 7.5 ka (Noah’s Flood).     

Upwelling in the Black Sea by the results of numerical experiments and satellite data

The paper analyses results of the numerical simulation of upwelling events in the north-western part of the Black Sea, mostly near the South Crimea. The calculations were performed using a numerical model based on primitive hydrodynamics equations. Emphasis is laid on the case when a salinity front simulating the Black Sea rim current is prescribed in the initial conditions. The interaction of the Black Sea rim current's stream with the coastline and bottom topography leads to the development of an upwelling near the Crimea's coast, even in the absence of wind forcing. The paper discusses the structure of the three-dimensional circulation of waters in the shelf area of the NW Black Sea. Numerical modelling results are matched up with the satellite data obtained by the HRPT receiving station. Translated by Vladimir A. Puchkin.