scholarly journals Radioecological regularities of plutonium alpha-radionuclides redistribution in the Black Sea ecosystem

2016 ◽  
Vol 1 (3) ◽  
pp. 3-13 ◽  
Author(s):  
N. N. Tereshchenko ◽  
S. B. Gulin ◽  
V. Yu. Proskurnin
Keyword(s):  
Surface Water ◽  
Bottom Sediment ◽  
Black Sea ◽  
Surface Waters ◽  
Developed Countries ◽  
Sea Surface ◽  
The Black Sea ◽  
Radiochemical Analysis ◽  
Natural Ecosystems ◽  
High Concentration

The work is devoted to the study of radioecological processes of redistribution of plutonium alpha-radionuclides (239+240Pu) as the main man-maid dose-forming alpha-radionuclides during the period after Chernobyl NPP accident. 239+240Pu are long-lived radioisotopes, the content of which is increasing in natural ecosystems from incident to incident. Radiotoxicity of these radionuclides is high, and we need science-based approaches of assessment and forecast of radioecological condition of the basins being at risk of a radioactive re-contamination, such as the Black Sea as an inland sea located at region close to developed countries using nuclear technologies. The study was performed with modern advanced techniques, the main of them were radiochemical analysis, alpha-spectrometry and radiotracer technologies. As a result of investigation the radiological regularities of plutonium behavior in the Black Sea ecosystem during the post-Chernobyl period were revealed. Quantitative parameters of plutonium migration in the sea were determined: sedimentation rates at different areas of the sea, the 239+240Pu effective half-lives in surface water, the 239+240Pu radiocapacity factor for bottom sediment, the 239+240Pu fluxes, levels of 239+240Pu in the ecosystem components, and the 239+240Pu accumulation factors for biotic and abiotic components. The features of the biogeochemical behavior of plutonium in the Black Sea ecosystem were identified and the conditions and processes causing them were indicated. The increased ability of the Black Sea surface water to self-purification against 239+240Pu, short residence time of plutonium in surface waters, the relatively high rapid of plutonium accumulation in the bottom sediment due to biogeochemical sedimentation of it, the high concentration ability of silt sediment against 239+240Pu and the type of biogeochemical behavior of plutonium in the Black Sea ecosystem has been observed.

scholarly journals CARBON-TO-CHLOROPHYLL-A RATIO IN THE PHYTOPLANKTON OF THE BLACK SEA SURFACE LAYER: VARIABILITY AND REGULATORY FACTORS

2018 ◽  
Vol 17 ◽  
pp. 60-73 ◽  
Author(s):  
Liudmila V. Stelmakh ◽  
Tatiana I. Gorbunova
Keyword(s):  
Surface Layer ◽  
Surface Water ◽  
Black Sea ◽  
Water Layer ◽  
Taxonomic Composition ◽  
Sea Surface ◽  
The Black Sea ◽  
Summer Period ◽  
Upper Mixed Layer ◽  
Main Influence

Based on the research, conducted in the Black Sea during period of time from 2000 to 2011, seasonal dynamic of C:Chl a ratio and its spatial variability in nano- and microphytoplankton of surface water layer (0–0.5 m) had been analyzed. Maximum values of this parameter were observed in summer, and minimum ones – in winter. Intermediate values of C:Chl a were marked in spring and autumn. The main reasons for variability of the ratio between an organic carbon and chlorophyll a are the light, and different size of phytoplankton and its taxonomic composition. In coastal areas of the sea during summer period, when average values of light intensity in the upper mixed layer are above 20 E·m-2·day-1, size and taxonomic composition of phytoplankton provide main influence to C:Chl a ratio.

Structure ofEmiliania huxleyiblooms in the Black Sea surface waters as detected by SeaWIFS imagery

2001 ◽  
Vol 28 (24) ◽  
pp. 4607-4610 ◽  
Author(s):  
Tulay Cokacar ◽  
Nilgun Kubilay ◽  
Temel Oguz
Keyword(s):  
Black Sea ◽  
Surface Waters ◽  
Sea Surface ◽  
The Black Sea

Role of suspended matter in controlling beryllium-7 (7Be) in the Black Sea surface layer

2021 ◽  
pp. 103513
Author(s):  
Dmitrii A. Kremenchutskii ◽  
Gennady F. Batrakov ◽  
Illarion I. Dovhyi ◽  
Yury A. Sapozhnikov
Keyword(s):  
Surface Layer ◽  
Black Sea ◽  
Suspended Matter ◽  
Sea Surface ◽  
The Black Sea

scholarly journals Long term trends in the sea surface temperature of the Black Sea

Ocean Science ◽  
2010 ◽  
Vol 6 (2) ◽  
pp. 491-501 ◽  
Author(s):  
G. I. Shapiro ◽  
D. L. Aleynik ◽  
L. D. Mee
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Black Sea ◽  
Sea Surface ◽  
The Black Sea ◽  
The North ◽  
Sst Variability ◽  
Long Term Trends ◽  
Cooling Trend

Abstract. There is growing understanding that recent deterioration of the Black Sea ecosystem was partly due to changes in the marine physical environment. This study uses high resolution 0.25° climatology to analyze sea surface temperature variability over the 20th century in two contrasting regions of the sea. Results show that the deep Black Sea was cooling during the first three quarters of the century and was warming in the last 15–20 years; on aggregate there was a statistically significant cooling trend. The SST variability over the Western shelf was more volatile and it does not show statistically significant trends. The cooling of the deep Black Sea is at variance with the general trend in the North Atlantic and may be related to the decrease of westerly winds over the Black Sea, and a greater influence of the Siberian anticyclone. The timing of the changeover from cooling to warming coincides with the regime shift in the Black Sea ecosystem.

scholarly journals Drivers, mechanisms and long-term variability of seasonal hypoxia on the Black Sea northwestern shelf – is there any recovery after eutrophication?

2013 ◽  
Vol 10 (6) ◽  
pp. 3943-3962 ◽  
Author(s):  
A. Capet ◽  
J.-M. Beckers ◽  
M. Grégoire
Keyword(s):  
Organic Matter ◽  
Spatial Distribution ◽  
Interannual Variability ◽  
Black Sea ◽  
Sea Surface ◽  
The Black Sea ◽  
Northwestern Shelf ◽  
Bottom Waters ◽  
Seasonal Hypoxia ◽  
Bottom Hypoxia

Abstract. The Black Sea northwestern shelf (NWS) is a shallow eutrophic area in which the seasonal stratification of the water column isolates the bottom waters from the atmosphere. This prevents ventilation from counterbalancing the large consumption of oxygen due to respiration in the bottom waters and in the sediments, and sets the stage for the development of seasonal hypoxia. A three-dimensional (3-D) coupled physical–biogeochemical model is used to investigate the dynamics of bottom hypoxia in the Black Sea NWS, first at seasonal and then at interannual scales (1981–2009), and to differentiate its driving factors (climatic versus eutrophication). Model skills are evaluated by a quantitative comparison of the model results to 14 123 in situ oxygen measurements available in the NOAA World Ocean and the Black Sea Commission databases, using different error metrics. This validation exercise shows that the model is able to represent the seasonal and interannual variability of the oxygen concentration and of the occurrence of hypoxia, as well as the spatial distribution of oxygen-depleted waters. During the period 1981–2009, each year exhibits seasonal bottom hypoxia at the end of summer. This phenomenon essentially covers the northern part of the NWS – which receives large inputs of nutrients from the Danube, Dniester and Dnieper rivers – and extends, during the years of severe hypoxia, towards the Romanian bay of Constanta. An index H which merges the aspects of the spatial and temporal extension of the hypoxic event is proposed to quantify, for each year, the intensity of hypoxia as an environmental stressor. In order to explain the interannual variability of H and to disentangle its drivers, we analyze the long time series of model results by means of a stepwise multiple linear regression. This statistical model gives a general relationship that links the intensity of hypoxia to eutrophication and climate-related variables. A total of 82% of the interannual variability of H is explained by the combination of four predictors: the annual riverine nitrate load (N), the sea surface temperature in the month preceding stratification (Ts), the amount of semi-labile organic matter accumulated in the sediments (C) and the sea surface temperature during late summer (Tf). Partial regression indicates that the climatic impact on hypoxia is almost as important as that of eutrophication. Accumulation of organic matter in the sediments introduces an important inertia in the recovery process after eutrophication, with a typical timescale of 9.3 yr. Seasonal fluctuations and the heterogeneous spatial distribution complicate the monitoring of bottom hypoxia, leading to contradictory conclusions when the interpretation is done from different sets of data. In particular, it appears that the recovery reported in the literature after 1995 was overestimated due to the use of observations concentrated in areas and months not typically affected by hypoxia. This stresses the urgent need for a dedicated monitoring effort in the Black Sea NWS focused on the areas and months concerned by recurrent hypoxic events.

scholarly journals An operational implementation of the GHER model for the Black Sea, with SST and CTD data assimilation

2009 ◽  
Vol 6 (2) ◽  
pp. 1895-1911 ◽  
Author(s):  
L. Vandenbulcke ◽  
A. Capet ◽  
J. M. Beckers ◽  
M. Grégoire ◽  
S. Besiktepe
Keyword(s):  
Black Sea ◽  
Initial Conditions ◽  
Sea Surface ◽  
The Black Sea ◽  
Marmara Sea ◽  
Reduced Rank ◽  
Data Transfers ◽  
Time Required ◽  
Assimilation Scheme

Abstract. In this article, we describe the first operational implementation of the GHER hydrodynamic model. This happened onboard the research vessel "Alliance", in the context of the Turkish Straits System 2008 campaign, which aimed at the real-time characterization of the Marmara Sea and (south-western) Black Sea. The model performed badly at first, mainly because of poor initial conditions. Hence, as the model includes a reduced-rank extended Kalman filter assimilation scheme, after a hindcast where sea surface temperature and temperature and salinity profiles were assimilated, the model yielded realistic forecasts. Furthermore, the time required to run a one-day simulation (about 5 min of simulation, or 10 min with pre-processing and data transfers included) is very limited and thus operational use of the model is possible.

The new Black Sea Reanalysis System within CMEMS

2021 ◽  
Author(s):  
Leonardo Lima ◽  
Stefania Angela Ciliberti ◽  
Ali Aydogdu ◽  
Romain Escudier ◽  
Simona Masina ◽  
...  
Keyword(s):  
Data Assimilation ◽  
Sea Level ◽  
Black Sea ◽  
General Circulation ◽  
Circulation Model ◽  
Sea Surface Height ◽  
Sea Surface ◽  
The Black Sea ◽  
Freshwater Flux ◽  
Sea Level Anomaly

<p>Ocean reanalyses are becoming increasingly important to reconstruct and provide an overview of the ocean state from the past to the present-day. These products require advanced scientific methods and techniques to produce a more accurate ocean representation. In the scope of the Copernicus Marine Environment Monitoring Service (CMEMS), a new Black Sea (BS) reanalysis, BS-REA (BSE3R1 system), has been produced by using an advanced variational data assimilation method to combine the best available observations with a state-of-the-art ocean general circulation model. The hydrodynamical model is based on Nucleus for European Modeling of the Ocean (NEMO, v3.6), implemented for the BS domain with horizontal resolution of 1/27° x 1/36°, and 31 unevenly distributed vertical levels. NEMO is forced by atmospheric surface fluxes computed via bulk formulation and forced by ECMWF ERA5 atmospheric reanalysis product. At the surface, the model temperature is relaxed to daily objective analysis fields of sea surface temperature from CMEMS SST TAC. The exchange with Mediterranean Sea is simulated through relaxation of the temperature and salinity near Bosporus toward a monthly climatology computed from a high-resolution multi-year simulation, and the barotropic Bosporus Strait transport is corrected to balance the variations of the freshwater flux and the sea surface height measured by multi-satellite altimetry observations. A 3D-Var ocean data assimilation scheme (OceanVar) is used to assimilate sea level anomaly along-track observations from CMEMS SL TAC and available in situ vertical profiles of temperature and salinity from both SeaDataNet and CMEMS INS TAC products. Comparisons against the previous Black Sea reanalysis (BSE2R2 system) show important improvements for temperature and salinity, such that errors have significantly decreased (about 50%). Temperature fields present a continuous warming in the layer between 25-150 m, within which there is the presence of the Black Sea Cold Intermediate Layer (CIL). SST exhibits a positive bias and relatively higher root mean square error (RMSE) values are present in the summer season. Spatial maps of sea level anomaly reveal the largest RMSE close to the shelf areas, which are related to the mesoscale activity along the Rim current. The BS-REA catalogue includes daily and monthly means for 3D temperature, salinity, and currents and 2D sea surface height, bottom temperature, mixed layer fields, from Jan 1993 to Dec 2019.  The BSE3R1 system has produced very accurate estimates which makes it very suitable for assessing more realistic climate trends and indicators for important ocean properties.</p>

The Black Sea Historical Statistics, 1812-1914: A Short Introduction

2020 ◽  
Vol 32 (2) ◽  
pp. 451-463 ◽  
Author(s):  
Alexandra Papadopoulou
Keyword(s):  
Black Sea ◽  
Global Economy ◽  
Historical Analysis ◽  
Developed Countries ◽  
The Black Sea ◽  
Regional Patterns ◽  
Long Run ◽  
Social And Economic Development ◽  
Economic Collaboration ◽  
Eastern European Countries

This paper is an introduction to the Black Sea Historical Statistics (BSHS), a database system which includes data on the commerce and shipping of the Black Sea from 1812 to 1914. BSHS is one of the main products of a larger interdisciplinary project that brought together researchers from several universities, research centres and institutes in order to examine the social and economic development of the Black Sea, the main grain exporting market in the nineteenth century. Methodologically, BSHS transcends the traditional narrow nation-centred approach by focusing on the Black Sea as the unit of historical analysis. In this way, it fosters cross-regional comparisons and the identification of regional patterns of economic collaboration and competition in the long run. The creation of BSHS involved dealing with several challenges, emerging from the honogenization of data extracted from archival sources of 10 different countries. The main issue was the coexistence of different systems of quantification (measures, weights and currencies) in an era when the process of transition from pre-modern regionalism to the first global economy in the 1870s and 1880s was slow and uneven. While developed countries were involved actively in this process, Eastern European countries were trapped between tradition and modernity. We, therefore, consider that the ways we have dealt with these complexities might provide useful feedback for similar projects in the future.

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