scholarly journals Numerical studies on the dynamics of the Northwestern Black Sea shelf

2004 ◽  
Vol 5 (1) ◽  
pp. 133 ◽  
Author(s):  
V. KOURAFALOU ◽  
K. TSIARAS ◽  
J. STANEVA
Keyword(s):  
Numerical Simulations ◽  
Black Sea ◽  
Nutrient Management ◽  
Ocean Model ◽  
The Black Sea ◽  
Topographic Effects ◽  
Danube Basin ◽  
Low Salinity ◽  
Basin Scale ◽  
Shelf Dynamics

The Northwestern Black Sea shelf dynamics are studied with numerical simulations based on the Princeton Ocean Model. The study focus is on buoyancy and wind driven flows and on the transport and fate of low salinity waters that are introduced through riverine sources (the Danube, Dnestr and Dnepr Rivers), under the seasonal changes in atmospheric forcing. The study is part of the DANUBS project (NUtrient management in the DAnube basin and its impact on the Black Sea). The numerical simulations show that the coastal circulation is greatly influenced by river runoff and especially that of the Danube, which is dominant with monthly averaged values ranging from 5,000 m3 to 10,000 m3. The transport of low-salinity waters associated with the Danube runoff is greatly influenced by wind stress, topographic effects and basin-scale circulation patterns, such as changes in the position of the Rim Current.

Mesoscale eddies in the Black Sea: Characteristics and kinematic properties in a high-resolution ocean model

2021 ◽  
pp. 103613
Author(s):  
Ehsan Sadighrad ◽  
Bettina A. Fach ◽  
Sinan S. Arkin ◽  
Baris Salihoğlu ◽  
Sinan Hüsrevoğlu
Keyword(s):  
High Resolution ◽  
Black Sea ◽  
Mesoscale Eddies ◽  
Ocean Model ◽  
The Black Sea ◽  
Kinematic Properties

Basin scale spatiotemporal analysis of shoreline change in the Black Sea

2021 ◽  
Vol 252 ◽  
pp. 107247
Author(s):  
Tahsin Görmüş ◽  
Berna Ayat ◽  
Burak Aydoğan ◽  
Florin Tătui
Keyword(s):  
Black Sea ◽  
Shoreline Change ◽  
Spatiotemporal Analysis ◽  
The Black Sea ◽  
Basin Scale

A New Solar Radiation Penetration Scheme for Use in Ocean Mixed Layer Studies: An Application to the Black Sea Using a Fine-Resolution Hybrid Coordinate Ocean Model (HYCOM)*

2005 ◽  
Vol 35 (1) ◽  
pp. 13-32 ◽  
Author(s):  
A. Birol Kara ◽  
Alan J. Wallcraft ◽  
Harley E. Hurlburt
Keyword(s):  
Solar Radiation ◽  
Optical Depth ◽  
Black Sea ◽  
Ocean Circulation ◽  
Mixed Layer ◽  
Ocean Model ◽  
The Black Sea ◽  
Atmospheric Forcing ◽  
Model Simulations ◽  
Hybrid Coordinate Ocean Model

Abstract A 1/25° × 1/25° cos(lat) (longitude × latitude) (≈3.2-km resolution) eddy-resolving Hybrid Coordinate Ocean Model (HYCOM) is introduced for the Black Sea and used to examine the effects of ocean turbidity on upper-ocean circulation features including sea surface height and mixed layer depth (MLD) on annual mean climatological time scales. The model is a primitive equation model with a K-profile parameterization (KPP) mixed layer submodel. It uses a hybrid vertical coordinate that combines the advantages of isopycnal, σ, and z-level coordinates in optimally simulating coastal and open-ocean circulation features. This model approach is applied to the Black Sea for the first time. HYCOM uses a newly developed time-varying solar penetration scheme that treats attenuation as a continuous quantity. This scheme includes two bands of solar radiation penetration, one that is needed in the top 10 m of the water column and another that penetrates to greater depths depending on the turbidity. Thus, it is suitable for any ocean general circulation model that has fine vertical resolution near the surface. With this scheme, the optical depth–dependent attenuation of subsurface heating in HYCOM is given by monthly mean fields for the attenuation of photosynthetically active radiation (kPAR) during 1997–2001. These satellite-based climatological kPAR fields are derived from Sea-Viewing Wide Field-of-View Sensor (SeaWiFS) data for the spectral diffuse attenuation coefficient at 490 nm (k490) and have been processed to have the smoothly varying and continuous coverage necessary for use in the Black Sea model applications. HYCOM simulations are driven by two sets of high-frequency climatological forcing, but no assimilation of ocean data is then used to demonstrate the importance of including spatial and temporal varying attenuation depths for the annual mean prediction of upper-ocean quantities in the Black Sea, which is very turbid (kPAR > 0.15 m−1, in general). Results are reported from three model simulations driven by each atmospheric forcing set using different values for the kPAR. A constant solar-attenuation optical depth of ≈17 m (clear water assumption), as opposed to using spatially and temporally varying attenuation depths, changes the surface circulation, especially in the eastern Black Sea. Unrealistic sub–mixed layer heating in the former results in weaker stratification at the base of the mixed layer and a deeper MLD than observed. As a result, the deep MLD off Sinop (at around 42.5°N, 35.5°E) weakens the surface currents regardless of the atmospheric forcing used in the model simulations. Using the SeaWiFS-based monthly turbidity climatology gives a shallower MLD with much stronger stratification at the base and much better agreement with observations. Because of the high Black Sea turbidity, the simulation with all solar radiation absorbed at the surface case gives results similar to the simulations using turbidity from SeaWiFS in the annual means, the aspect of the results investigated in this paper.

Coupled Hydrodynamic Ecosystem Model of the Black Sea at Basin Scale

1997 ◽  
pp. 487-499 ◽  
Author(s):  
M. Grégoire ◽  
J.-M. Beckers ◽  
J. C. J. Nihoul ◽  
E. Stanev
Keyword(s):  
Black Sea ◽  
Ecosystem Model ◽  
The Black Sea ◽  
Basin Scale

Lessons learned from investigations on case study level for modelling of nutrient emissions in the Danube basin

2005 ◽  
Vol 51 (11) ◽  
pp. 183-191 ◽  
Author(s):  
C. Schilling ◽  
H. Behrendt ◽  
A. Blaschke ◽  
S. Danielescu ◽  
G. Dimova ◽  
...  
Keyword(s):  
Case Studies ◽  
Nutrient Management ◽  
Nutrient Balance ◽  
Lessons Learned ◽  
The Black Sea ◽  
Emission Model ◽  
Nitrogen And Phosphorus ◽  
Danube Basin ◽  
Study Region ◽  
Nutrient Emissions

In the framework of the project daNUbs (Nutrient Management in the Danube Basin and its Impact on the Black Sea) the MONERIS emission model is used for the basin wide calculation of nutrient (nitrogen and phosphorus) emissions in the Danube Basin. The MONERIS model was developed and successfully applied for German river catchments. Based on investigations in selected test regions (case studies) the daNUbs approach is to check the applicability of the MONERIS emission model for the specific conditions of the Danube Basin in more detail than is possible with a basin wide application. Six case studies with areas of 400–3,500 km2 and several subcatchments have been selected in order to represent different conditions along the Danube Basin. In this study region intensive data collection and enhanced monitoring has been performed in order to raise the database significantly above the generally available data. Water balance as well as nutrient balance calculations have been performed with the MONERIS model as well as with other approaches. Results are compared to each other and to data from monitoring. Results up till now showed the applicability and sensitivity of the MONERIS approach in different conditions of the Danube Basin (e.g. emissions via groundwater). They indicated that the nitrogen retention in the catchments is well described with the MONERIS model.

Biogeochemical controls on the Black Sea oxygen dynamics : relevant diagnostics, key processes and adequacy of the monitoring infrastructure.

2020 ◽  
Author(s):  
Arthur Capet ◽  
vandenbulcke Luc ◽  
Grégoire Marilaure
Keyword(s):  
Black Sea ◽  
3D Models ◽  
The Black Sea ◽  
Biogeochemical Model ◽  
Model Parameters ◽  
Biogeochemical Processes ◽  
Low Oxygen ◽  
Future Evolution ◽  
Basin Scale ◽  
Set Up

<p>An important deoxygenation trend has been described in the Black Sea over the five past decades from in-situ observations [1]. While the implications for basin-scale biogeochemistry and possible future trends of this dynamics are unclear, it is important to consolidate our means to resolve the dynamics of the Black Sea oxygen content in order to assess the likelihood of future evolution scenario, and the possible morphology of low-oxygen events. </p><p>Also, it is known that current global models simulate only about half the observed oceanic O2 loss and fail in reproducing its vertical distribution[2]. In parts, unexplained O2 losses could be attributed to illy parameterized biogeochemical processes within 3D models used to integrate those multi-elemental dynamics.</p><p>Biogeochemical processes involved in O2 dynamics are structured vertically and well separated in the stratified Black Sea. O2 sources proceed from air-sea fluxes and photosynthesis in the<br>photic zone. Organic matter (OM) is respired over a depth determined by its composition and<br>sinking, via succeeding redox reactions. Those intricate dynamics leave unknowns as regards the biogeochemical impacts of future deoxygenation on associated cycles, for instance on the oceanic carbon pump. Here we use the Black Sea scene to derive model-observation strategies to best address the global deoxygenation concern.</p><p>First, we decipher components of the O2 dynamics in the open basin, and discuss the way in which O2-based indicators informs on the relative importance of processes involved. Using 1D biogeochemical model set-up, we then conduct a sensitivity analysis to pin-point model parameters, ie. biogeochemical processes, that bears the largest part in the uncertainty of simulated results for those diagnostics. Finally, we identify among the most impacting parameters the ones that can most efficiently be constrained on the basis of modern observational infrastructure, and Bio-Argo in particular. </p><p>The whole procedure aims at orienting the development of observations networks and data assimilation approaches in order to consolidate our means to anticipate the marine deoxygenation challenge. </p><p>[1] Capet A et al., 2016, Biogeoscience, 13:1287-1297<br>[2] Oschlies A et al., 2018, Nature Geosci, 11(7):467–473</p>

scholarly journals Dynamics of the Deep Chlorophyll Maximum in the Black Sea as depicted by BGC-Argo floats

2021 ◽  
Author(s):  
Arthur Capet ◽  
florian ricour ◽  
Fabrizio D'Ortenzio ◽  
Bruno Delille ◽  
Marilaure Grégoire
Keyword(s):  
Black Sea ◽  
Global Ocean ◽  
The Black Sea ◽  
Second Phase ◽  
Deep Chlorophyll Maximum ◽  
Phytoplankton Productivity ◽  
Spatial Homogeneity ◽  
Argo Floats ◽  
Chlorophyll Maximum ◽  
Basin Scale

<p>The deep chlorophyll maximum (DCM) is a well known feature of the global ocean. However, its description and the study of its formation are a  challenge, especially in the peculiar environment that is the Black Sea. The retrieval of chlorophyll a (Chla) from fluorescence (Fluo) profiles recorded by biogeochemical-Argo (BGC-Argo) floats is not trivial in the Black Sea, due to the very high content of colored dissolved organic matter (CDOM) which contributes to the fluorescence signal and produces an apparent increase of the Chla concentration with depth.</p><p>Here, we revised Fluo correction protocols for the Black Sea context using co-located in-situ high-performance liquid chromatography (HPLC) and BGC-Argo measurements. The processed set of Chla data (2014–2019) is then used to provide a systematic description of the seasonal DCM dynamics in the Black Sea and to explore different hypotheses concerning the mechanisms underlying its development.</p><p>Our results show that the corrections applied to the Chla profiles are consistent with HPLC data. In the Black Sea, the DCM begins to form in March, throughout the basin, at a density level set by the previous winter mixed layer. During a first phase (April-May), the DCM remains attached to this particular layer. The spatial homogeneity of this feature suggests a hysteresis mechanism, i.e., that the DCM structure locally influences environmental conditions rather than adapting instantaneously to external factors.</p><p>In a second phase (July-September), the DCM migrates upward, where there is higher irradiance, which suggests the interplay of biotic factors. Overall, the DCM concentrates around 45 to 65% of the total chlorophyll content within a 10 m layer centered around a depth of 30 to 40 m, which stresses the importance of considering DCM dynamics when evaluating phytoplankton productivity at basin scale.</p>

Nutrient fluxes from the Danube Basin to the Black Sea

2002 ◽  
Vol 46 (8) ◽  
pp. 9-17 ◽  
Author(s):  
M. Zessner ◽  
J. van Gils
Keyword(s):  
Black Sea ◽  
Surface Waters ◽  
State Of The Art ◽  
The Black Sea ◽  
Quality Model ◽  
Danube Basin ◽  
Quantitative Synthesis ◽  
One Step ◽  
Measured Water ◽  
Model Approach

This paper deals with the state of the art of quantification of sources, pathways and sinks of nutrients in the Danube Basin and their transport from the catchment to the Black Sea. It shows main results of emission estimates to surface waters and the Danube Water Quality Model approach to link these emissions estimates to measured water monitoring data. The current paper provides a quantitative synthesis of available knowledge regarding the fate of nutrients in the Danube Basin. Even though many knowledge gaps existed, our understanding of the system has increased. As such, the paper provides a vehicle to carry the discussion one step beyond just complaining about how much we do not know yet.

Nutrient Balances for Danube Countries: A Strategic Analysis

1999 ◽  
Vol 40 (10) ◽  
pp. 9-16 ◽  
Author(s):  
L. Somlyódy ◽  
P. H. Brunner ◽  
H. Kroiϐ
Keyword(s):  
Water Quality ◽  
Black Sea ◽  
Municipal Wastewater ◽  
Early Recognition ◽  
Water Quality Management ◽  
Strategy Development ◽  
The Black Sea ◽  
Wastewater Management ◽  
Nutrient Balances ◽  
Danube Basin

Issues of nutrient management were studied in ten countries of the Danube Basin in the frame of the Danube Environment Programme. Comprehensive data collection covered socio-economic and natural factors influencing nutrient balances, water quality of the Danube and its tributaries, and major features of wastewater management for municipalities. The innovative methodology of materials accounting was applied to develop nutrient balances for the countries involved and the Danube Basin, and to get insight on causes, temporal changes of stocks and early recognition. The approach was cross-checked against loads estimated from ambient water quality observations. Main dilemmas of water quality management (local problems, and the regional eutrophication of the Danube Delta and the Black Sea) were identified and options of load reductions were evaluated. Agriculture pollution of mostly non-point source origin was found as the key of developing an integrated emission reduction policy for the Basin. Municipal wastewater management strategies were studied in detail. Recommendations were given on strategy development, monitoring, research and improved international cooperation in the Danube/Black Sea Basin.

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