scholarly journals Features of Currents on the Black Sea Northwestern Shelf Based on the Numerical Simulation Results

2021 ◽  
Vol 37 (4) ◽  
Author(s):  
V. L. Dorofeyev ◽  
L. I. Sukhikh ◽  
◽  

Purpose. The work is aimed at studying the features of currents on the Black Sea northwestern shelf based of the reanalysis results, and at analyzing the reasons of these features. Methods and Results. To analyze the currents on the northwestern shelf, applied were the results of physical reanalysis of the Black Sea fields performed by the authors earlier, namely, the arrays of hydrodynamic fields on a regular grid with the 21-year duration (1992–2012). Surface currents on the northwestern shelf of the Black Sea are directed mainly to the southwest. Throughout the whole year (except for the summer months when the wind effect weakens), an intensive compensatory current directed to the south is formed along the western coast. The waters near the western coast are highly horizontally stratified that is caused by fresh water inflowing with the river runoffs. In winter seasons, the stratification is most pronounced, whereas in summer, the horizontal density gradient decreases. The horizontal density stratification leads to the following: starting from the depth ~ 20 m, the pressure gradient changes its sign and the along-coastal jet countercurrent directed to the north, occurs. Conclusions. The performed studies have shown that the water circulation on the Black Sea northwestern shelf is determined mainly by the following factors: the wind-induced water flows across the shelf boundary and strong horizontal water stratification near the western coast resulted from the river runoffs. As the currents on the sea surface are directed mainly to the southwest, the compensatory current directed to the south is formed near the western coast. Due to the strong horizontal stratification resulted from the river runoffs, a countercurrent directed to the north is formed in the subsurface layer near the western coast. In case the seawater flows to the shelf are extremely high, the countercurrent may be absent.

2021 ◽  
Vol 28 (4) ◽  
Author(s):  
V. L. Dorofeyev ◽  
L. I. Sukhikh ◽  
◽  

Purpose. The work is aimed at studying the features of currents on the Black Sea northwestern shelf based of the reanalysis results, and at analyzing the reasons of these features. Methods and Results. To analyze the currents on the northwestern shelf, applied were the results of physical reanalysis of the Black Sea fields performed by the authors earlier, namely, the arrays of hydrodynamic fields on a regular grid with the 21-year duration (1992–2012). Surface currents on the northwestern shelf of the Black Sea are directed mainly to the southwest. Throughout the whole year (except for the summer months when the wind effect weakens), an intensive compensatory current directed to the south is formed along the western coast. The waters near the western coast are highly horizontally stratified that is caused by fresh water inflowing with the river runoffs. In winter seasons, the stratification is most pronounced, whereas in summer, the horizontal density gradient decreases. The horizontal density stratification leads to the following: starting from the depth ~ 20 m, the pressure gradient changes its sign and the along-coastal jet countercurrent directed to the north, occurs. Conclusions. The performed studies have shown that the water circulation on the Black Sea northwestern shelf is determined mainly by the following factors: the wind-induced water flows across the shelf boundary and strong horizontal water stratification near the western coast resulted from the river runoffs. As the currents on the sea surface are directed mainly to the southwest, the compensatory current directed to the south is formed near the western coast. Due to the strong horizontal stratification resulted from the river runoffs, a countercurrent directed to the north is formed in the subsurface layer near the western coast. In case the seawater flows to the shelf are extremely high, the countercurrent may be absent.


2020 ◽  
Vol 19 (1) ◽  
pp. 19-30
Author(s):  
Faize Sarış

AbstractThis paper analyses extreme precipitation characteristics of Turkey based on selected WMO climate change indices. The indices – monthly total rainy days (RDays); monthly maximum 1-day precipitation (Rx1day); simple precipitation intensity index (SDII); and monthly count of days when total precipitation (represented by PRCP) exceeds 10 mm (R10mm) – were calculated for 98 stations for the 38-year overlapping period (1975–2012). Cluster analysis was applied to evaluate the spatial characterisation of the annual precipitation extremes. Four extreme precipitation clusters were detected. Cluster 1 corresponds spatially to Central and Eastern Anatolia and is identified with the lowest values of the indices, except rainy days. Cluster 2 is concentrated mainly on the west and south of Anatolia, and especially the coastal zone, and can be characterised with the lowest rainy days, and high and moderate values of other indices. These two clusters are the most prominent classes throughout the country, and include a total of 82 stations. Cluster 3 is clearly located in the Black Sea coastal zone in the north, and has high and moderate index values. Two stations on the north-east coast of the Black Sea region are identified as Cluster 4, which exhibits the highest values among all indices. The overall results reveal that winter months and October have the highest proportion of precipitation extremes in Turkey. The north-east part of the Black Sea region and Mediterranean coastal area from the south-west to the south-east are prone to frequent extreme precipitation events.


2012 ◽  
pp. 37-60 ◽  
Author(s):  
Nadezda Krstic ◽  
Ljubinko Savic ◽  
Gordana Jovanovic

Palaeogeographic maps of the lacustrine Miocene and Pliocene have been constructed according to all the known geological data. The Lakes of the Balkan Land, depending on the tectonics, migrated due to causes from the deep subsurface. There are several phases of the Miocene lakes: the lowermost Miocene transiting from marine Oligocene, Lower, Middle, Upper Miocene covering, in patches, the main part of the Land. The Pliocene lakes spread mostly to the north of the Balkan Land and covered only its marginal parts. Other lake-like sediments, in fact freshened parts of the Black Sea Kuialnician (Upper Pliocene), stretched along the middle and southern portions of the Balkan Peninsula (to the south of the Balkan Mt.). Subsequently, the Balkan Peninsula was formed.


Author(s):  
Н.P. Ivus ◽  
E.V. Agayar ◽  
L.M. Hurska ◽  
А.В. Semergei-Chumachenko

Introduction. Nowadays the problem of storm winds appears to be a very relevant one in those spheres of human activities related to safety of human living, coastal infrastructure, seafaring, aviation etc. One of the conditions for successful forecasting of strong winds is familiarization with wind characteristics of the study area and with synoptic conditions causing them. The below listed results of research form continuation of previous works for search of a better synoptic classification reflecting completeness of macroscale baric processes causing formation of winds, including strong winds, over the South of Ukraine and also providing an opportunity to forecast winds in a more accurate manner. The purpose of this publication consists in analysis of interaction of large-scale atmospheric circulation with formation of unfavorable weather conditions (strong and very strong winds) on the north-west coast of the Black Sea. Methods and results. The impact of storm winds is significant for functioning of the national economic complex of the North-Western Black Sea region. In order to investigate this effect there were fifty seven cases of wind amplification up to criterion of strong ≥ 15 m·s-1 and very strong ≥ 25 m·s-1 selected within the Odessa region during the period from October to March in 2011 – 2014. Indexes of Katz circulation for isobaric surface of 500 hPa were calculated as per the data of synoptic archive for the cases with wind speed of ≥ 15 m·s-1. A more detailed study of the structure of macrocirculation processes under strong winds, except for Katz indexes, is provided by means of classification and calendar of successive change of elementary circulation mechanisms (ECM) in the Northern hemisphere according to Dzerdzeyevskyi B.L. and typification of synoptic processes developed at the Department of Theoretical Meteorology and Meteorological Forecasts of OSENU. It was determined that strong and very strong winds often occur in southern and central regions, particularly at the stations located on the shores of seas and estuaries (Bilgorod-Dnistrovskyi, Ust-Dunaysk, Pivdennyi port). Meridional type of atmospheric circulation (77.2%) creates favourable conditions for wind amplification in the North-Western part of the Black Sea up to the criterion of strong and very strong one, zonal type of circulation constitutes 22.8% from the total number of cases. Meridional type of circulation is mainly represented by mixed and western forms – (24.6%) and (22.8%) respectively. Main types of synoptic situations (5, 6) of Katz typification that used to cause strong winds were revealed. Most frequently strong wind was observed while moving of cyclonic vortexes from the South (ECM type – 12a, 13z) and in the area of cyclones and anticyclones interaction. Conclusion. It was found that wind speed amplification in the South of Ukraine up to the criteria of strong and very strong one mainly occurs due to the meridional type of atmospheric circulation which is dominated by mixed or western forms of circulation as per Katz typification, ECM type 12a and 13z according to Dzerdzeyevskyi B.L. and types 5 (subtype 5.2) and 6 (all subtypes depending on ECM) as per synoptic typification of OSENU. Directions for further research should include the following. The conclusions have preliminary character and need confirmation on the basis of bigger scope of statistical data.


2018 ◽  
pp. 100-106
Author(s):  
R. V. Gavrilyuk ◽  
N. M. Yuvchenko

The sea level of the Black Sea coastal area is subject to non-periodic wind-induced fluctuations. Such fluctuations affect economic activity of the sea ports, enterprises and businesses located within the coastal area while those may be flooded when the sea level rises and, on the contrary, there is a threat of vessels grounding in case of sea level fall. There are several big sea ports which are located at the north-western part of the Black Sea and affected by wind-induced fluctuations. Therefore, the study of these processes and development of methods allowing their forecast are of great practical interest and this fact proves the topicality of the conducted research. The article's aim is to analyse wind-induced fluctuations within the water area of Yuzhnyi and Chornomorsk sea ports, identify statistical links between such fluctuations and wind characteristics / equations used for calculation of their values. The observations at Chornomorsk (2006-2013) and Yuzhnyi (2000-2011) stations show that within a year there are 1-2 upsurge-downsurge occurrences during an average month, however, the number of those increases up to 3-4 over the autumn-winter period. The average sea level rise at Chornomorsk station is equal to 34 cm, the average sea level fall – 38 cm, maximum values amount to 97 cm and 191 cm, respectively. The average sea level rise at Yuzhnyi station is equal to 30 cm, the average sea level fall – 34 cm, maximum values amount to 91 and 98 cm, respectively. The average duration of wind-induced fluctuations at both stations amount to 34-38 hours. In most cases the sea level rise is observed at Chornomosk station when winds blow from the South and the South-East, at Yuzhnyi station  – when those blow from the South, the South-East and the South-West. The sea level fall is observed at Chornomosk station when winds blow from the North-West and the West, at Yuzhnyi station – when those blow from the North, the North-West and the North-East. Both stations are characterized with effective directions of wind causing occurrence of upsurge-downsurges. Based on the regression analysis equations for calculation of the sea level rise and fall values associated with wind characteristics were defined. The initial value of the sea level and the sum of the wind projections on effective directions for previous 30 hours are used as arguments in the equations. The accuracy of equation-based calculation constitutes 60-90%. The article offers recommendations on the use of equations when forecasting wind-induced fluctuations.


2001 ◽  
Vol 2 (2) ◽  
pp. 33 ◽  
Author(s):  
M. UNSAL

Lead pollution and its sources have been investigated in the south-eastern and south-western Black Sea. Surficial sediments and mussels were collected in different seasons of the year from the south-eastern and south-western Black Sea and analysed for their lead contents.In the south-eastern Black Sea sediments from the easternmost and from the central stations contained the highest lead concentrations. Sediments contained 8 to 10 times the lead concentrations of sediments from the south-west. Samples taken from rivers, streams and effluents had especially high lead concentrations. The highest lead concentrations were found in sediments collected in October and December.Lead concentrations in mussels from the south-eastern coast were comparatively lower compared to those from the south-western coast. The highest average values occurred in December and in October.In the south-western Black Sea, the highest lead concentrations in sediments were obtained in those from Inebolu, followed by those from around Zonguldak. The concentrations increased from the middle to the west of the southern Black Sea coast, possibly due to the effect of the Danube River. Sediments taken in September had the highest lead concentrations, followed by samples taken in December.Very high lead concentrations (> 10 μ g g-1) were observed in mussels from those stations where the sediments also contained high concentrations. Mussels had their highest lead concentrations in January and April.


Author(s):  
Т.В. Гиоргобиани

В статье рассмотрены условия формирования складчатой системы Большого Кавказа в альпийскую эпоху. Показано, что главная зональная линейная складчатая структура региона была сформирована на ранне- и среднеальпийской стадиях развития в результате проявления батской и пиренейской фаз складчатости. Установлено, что причиной складкообразования было активное столкновение Черноморско-Закавказского микроконтинента на юго-западе с пассивной окраиной Большого Кавказа. Определено, что позднеальпийская стадия в регионе проходила в условиях субмеридионального тангенциального давления, во время проявления плиоцен-четвертичных фаз складчатости. В это время на Большой Кавказ воздействовал не целостный Черноморско-Закавказский микроконтинент, а слагающие его мелкие плиты и блоки-шоли. Выяснено, что они в процессе тектогенеза перемещались и косо вдвигались в складчатую систему Большого Кавказа, вызывая преобразование первичной структуры и возникновение интерференционной складчатости. В результате повторного деформирования отдельных участков региона в его пределах образовалась неоднородная складчатая структура. Изучена основная особенность складчатой системы Большого Кавказа, выраженная структурной неоднородностью складчатости в поперечном и продольном направлениях. Установлено, что она отражает поэтапную и разноплановую деформацию отдельных участков, возникающую в результате последовательного проявления в регионе локальной и региональной геодинамики микроконтинента, а также связанных с ними общих и частных механизмов его формирования. Структурный анализ морфологии складчатости БК действительно показал неравномерную дислоцированность его – С-З и Ю-В сегментов, сложенных в основном ранне- и среднеальпийскими структурами, выраженную в разной степени осложненности коллизионными деформациями. Так, в пределах мальм-эоценового структурного этажа С-З Кавказа, раннеальпийская структура которого меньше всех остальных сегментов усложнена коллизионными деформациями, четко проявлена латеральная асимметричная зональность его складчатой структуры.  Она выражена в последовательной смене с юго-запада на северо-восток интенсивной линейной сильно сжатой складчатости линейными гребневидными, а затем слабо вытянутыми типичными брахиморфными складками, переходящими, в свою очередь, в полого наклонную на северо-восток моноклиналь The article considers the conditions of formation of folded system of the Greater Caucasus in the Alpine Epoch. It is shown that main zonal linear folded structure of the region was formed at the early and middle Alpine stages of the evolution in the result of manifestation of Bathonian and Pyrenean stages of folding. It was established that the cause of the folding was an active collision of the Black Sea-Transcaucasian microcontinent in the south-west with the passive margin of the Greater Caucasus. It was also determined that the Late Alpine stage in the region took place under the conditions ofsubmeridional tangential stress, during the Pliocene-Quarternary folding phases. During this period the Greater Caucasus was affected not by the whole Black Sea-Transcaucasian microcontinent, but by its smaller plates and blocks. It was found out that during the process of tectogenesis they drifted and obliquely moved into the folded system of the Greater Caucasus, causing the transformation of the initial structure and the occurrence of interferential folding. In the result of repeated deformation of separate areas of the region the heterogeneous folded structure was formed. The main feature of the folded structures of the Greater Caucasus (expressed by a structural heterogeny in transversal and longitudinal directions) was studied. It was determined that it reflects the gradual and diverse deformation of individual sections, resulting from the consistent manifestation of the local and regional geodynamics of the microcontinent, as well as the common and specific mechanisms of its formation associated with them. The structural analysis of the morphology of folding of the Great Caucasus really showed its uneven dislocation, i.e. the N-W and S-E of the segments, composed mainly of early and middle Alpine structures, expressed in varying degrees of complication by collisional deformations. So, within the Malm-Eocene structural floor of the northwestern Caucasus, the Early Alpine structure of which is less than all the other segments, is complicated by collimated deformations, the lateral asymmetric zonality of its folded structure is clearly manifested. It is expressed in a successive change from the south-west to the north-east of intensive linear highly compressed folding with linear ridge-like, and then slightly elongated typical brachymorphic folds, which turn into a hollow sloping to the north-east monocline


The aim of the research is to analyze the problem of anthropogenic influence on the sea coasts, to develop and improve the constructive-geographical foundations of rational nature management for the conservation and possible renewal of natural resources on the north-west coast of the Black Sea. Methods. The main methods used in the preparation process and writing of the article are systematization methods, retrospective, analytical, comparative geographical and historical. Scientific novelty of the article. The fact that the coastal zone of the Black Sea coast is experiencing uncontrolled anthropogenic impacts; this research has improved and developed constructive-geographical foundations for their rational management. Practical value. Developed scientific recommendations are universal. They are very important for the implementation of integrated management of the coastal zone in the country, the optimization of nature management and the preservation of the natural systems on the north-west coast of the Black Sea, in particular, and the entire World Ocean, as a whole. Research results. Intensive development of the coast and consumer economic activity over the past decades has led to the degradation of natural systems. Rational use of natural resources of the coastal zone of the sea assumed the development of foundations that comprehensively take into account the physical-geographical and socio-economic processes, as well as the laws of their development that determine the current state and dynamics of changes in natural systems during their operation. On the basis of a detailed study of domestic and foreign publications related to this topic, the activities of integrated coastal zone management (ICZM) in different countries of the world were analyzed. The foundations and principles for introducing ICZM in Ukraine are highlighted. It has been established that for the development of any projects in the coastal zone of the sea, it is necessary to have a scientific natural rationale from scientists obtained in the process of detailed research. These provisions can be the scientific basis of the relevant legislative framework for the optimization of nature management and spatial planning on the north-west coast of the Black Sea. Well-developed and improved scientific provisions are suitable for correcting the current situation in the direction of higher efficiency on coastаl control. These constructive-geographic foundations can become the basis and the main algorithm for practical implementation of environmental legislation in Ukraine.


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