scholarly journals The Black Sea General Circulation and Climatic Temperature and Salinity Fields

1992 ◽  
Author(s):  
Dimitur I. Trukhchev ◽  
Yurii L. Demin
Keyword(s):  
Black Sea ◽  
General Circulation ◽  
The Black Sea ◽  
Climatic Temperature

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>

NUMERICAL SIMULATION OF THE SEMIDIURNAL TIDAL WAVE IMPACT ON THE BLACK SEA CLIMATIC CIRCULATION

2017 ◽  
Author(s):  
Anna Lukyanova ◽  
Anna Lukyanova ◽  
Andrei Bagaev ◽  
Andrei Bagaev ◽  
Vladimir Zalesny ◽  
...  
Keyword(s):  
Black Sea ◽  
Time Scale ◽  
General Circulation ◽  
Circulation Model ◽  
The Black Sea ◽  
Marine Hydrophysical Institute ◽  
Wave Impact ◽  
Ecological Processes ◽  
Short Period ◽  
The Impact

The Black Sea is an enclosed deep marine basin, where the structure of tidal movements is dominated by the direct influence of the tidal force on the proper water body. We investigated the spatial structure of its climatic circulation under the impact of tides. We developed a program module extending the numerical general circulation model of the Black Sea which was designed in the Institute of numerical mathematics, Moscow. It allows the lunar semidiurnal harmonics (M_2) influence to be taken into account explicitly via the discrete analogues of the differential equations of motion. Our work reflects the main results of the numerical experiment on the 4x4 km horizontal grid and 40 vertical σ-levels. It was a one-year model run using the CORE atmospheric climatology forcing. We compared the first and the last weeks of simulation and found out that the characteristics of a tidal mode M2 were established at a very short period of time (7 days), which is the estimate of the model’s energy redistribution time scale. The coastal areas where the tidal impact is substantial (~10 cm) were located mainly at the shallow-shelf inlets highly influenced by the climate change. Validation of the cotidal maps showed the reliability of our model at the climatological time scale. In future we will focus on the baroclinic tidal movements and validation with the Marine Hydrophysical Institute database in order to shed new light on physical and ecological processes at the frontal zone along the Rim Current.

NUMERICAL SIMULATION OF THE SEMIDIURNAL TIDAL WAVE IMPACT ON THE BLACK SEA CLIMATIC CIRCULATION

2017 ◽  
Author(s):  
Anna Lukyanova ◽  
Anna Lukyanova ◽  
Andrei Bagaev ◽  
Andrei Bagaev ◽  
Vladimir Zalesny ◽  
...  
Keyword(s):  
Black Sea ◽  
Time Scale ◽  
General Circulation ◽  
Circulation Model ◽  
The Black Sea ◽  
Marine Hydrophysical Institute ◽  
Wave Impact ◽  
Ecological Processes ◽  
Short Period ◽  
The Impact

The Black Sea is an enclosed deep marine basin, where the structure of tidal movements is dominated by the direct influence of the tidal force on the proper water body. We investigated the spatial structure of its climatic circulation under the impact of tides. We developed a program module extending the numerical general circulation model of the Black Sea which was designed in the Institute of numerical mathematics, Moscow. It allows the lunar semidiurnal harmonics (M_2) influence to be taken into account explicitly via the discrete analogues of the differential equations of motion. Our work reflects the main results of the numerical experiment on the 4x4 km horizontal grid and 40 vertical σ-levels. It was a one-year model run using the CORE atmospheric climatology forcing. We compared the first and the last weeks of simulation and found out that the characteristics of a tidal mode M2 were established at a very short period of time (7 days), which is the estimate of the model’s energy redistribution time scale. The coastal areas where the tidal impact is substantial (~10 cm) were located mainly at the shallow-shelf inlets highly influenced by the climate change. Validation of the cotidal maps showed the reliability of our model at the climatological time scale. In future we will focus on the baroclinic tidal movements and validation with the Marine Hydrophysical Institute database in order to shed new light on physical and ecological processes at the frontal zone along the Rim Current.

The use of CMEMS Black Sea Physical Reanalysis (1993-2019) to understand better the Black Sea variability

2021 ◽  
Author(s):  
Elisaveta Peneva ◽  
Leonardo Lima ◽  
Ali Aydogdu ◽  
Simona Masina ◽  
Emil Stanev ◽  
...  
Keyword(s):  
Black Sea ◽  
General Circulation ◽  
Mixed Layer Depth ◽  
Surface Wind ◽  
Reanalysis Data ◽  
Current Speed ◽  
The Black Sea ◽  
Positive Trend ◽  
Dynamic Feature ◽  
Positive Tendency

<p>The recently upgrated CMEMS product Black Sea Physical Reanalysis (BLKSEA_MULTIYEAR_PHY_007_004) covers the period 1993-2019 presenting a base for reliable long-term estimates on different aspects of the Black Sea physical processes. The data archive provides monthly and daily fields for the Black Sea basin including 3D variables (temperature, salinity, zonal and meridional velocity components) and 2D variables (mixed layer depth, bottom temperature and sea surface height). </p><p>The good spatial and temporal resolution of the reanalysis gives possibility to evaluate the trend and variability of the subsurface temperature and salinity, as well as the general circulation changes. In the last two decades significant tendency for warming is observed at the surface and in deeper layers, reaching down ~100 m depth. This trend is associated with a slight positive salinity trend seen down to ~200 m depth, which is present almost in the entire Black Sea except for the north-western shelf close to the Danube and Dnestr river delta. Both temperature and salinity show strong interannual variability.  </p><p>The calculated Ocean Heat Content (OHC) in the Black Sea basin over the last ~30 year period suggests that the Black Sea water had experienced a general heating tendency after 2013. The increase of OHC is mostly due to the layer 0-200 m and the deeper layers are rather conservative in time. Nevertheless, the cold winter conditions in 2006, 2012 and 2017 led to significant surface water cooling and replenishment of the Cold Intermediate Layer. </p><p>The variation in the main dynamic feature of the basin, the Black Sea Rim current, is studied using the reanalysis data. It shows that the surface current speed varies within ~30% in the period 1993-2019 with a slight positive tendency. The main factor which triggers the inter-annual variability of the Rim current is found to be the atmospheric forcing. Comparison with the surface wind curl from the ERA5 reanalysis data shows significant correlation, predominantly positive (cyclonic) curl for both sea and atmosphere circulation and similar positive trend of the wind/current speed. This proves that the Black Sea Rim Current could be considered a Sverdrup balanced flow and thus strongly related to the regional air circulation.</p>

scholarly journals Influence of Dardanelles outflow induced thermal fronts and winds on drifter trajectories in the Aegean Sea

2014 ◽  
Vol 15 (2) ◽  
pp. 239 ◽  
Author(s):  
R. GERIN ◽  
V. KOURAFALOU ◽  
P.-M. POULAIN ◽  
Ş. BESIKTEPE
Keyword(s):  
Black Sea ◽  
General Circulation ◽  
Aegean Sea ◽  
The Black Sea ◽  
Data Set ◽  
Strong Connectivity ◽  
Surface Circulation ◽  
Circulation Patterns ◽  
Modelling Studies

The data provided by 12 drifters deployed in the Northern Aegean Sea in the vicinity of the Dardanelles Strait in August 2008 and February 2009 are used to explore the surface circulation of the basin and the connectivity to the Black Sea. The drifters were deployed within the Dardanelles outflow of waters of Black Sea origin in the Northeastern Aegean. Thanks to the particular choice of the drifter deployment positions, the data set provides a unique opportunity to observe the branching behaviour of the surface currents around Lemnos Island. Such pathways were notpossible to study with previous drifter deployments that were far from the Dardanelles Strait. In addition, the drifter tracks covered the Aegean basin quite thoroughly, mapping major circulation features and supporting the overall general circulation patterns described by previous observational and modelling studies. The collected data display cases in which drifters are driven by winds and thermal fronts. Wind products were used to estimate the influence of the atmospheric forcing on the drifter trajectories. Satellite sea surface temperature images were connected to the drifter tracks, demonstrating a high correlation between the remote and in situ observations. The waters of Black Sea origin were traced all the way to the Southern Aegean, establishing a strong connectivity link between the Aegean and Black Sea basins.

scholarly journals On the vortical motions in the Black Sea obtained by the 3-D hydrothermodynamical numerical model

2008 ◽  
Vol 14 ◽  
pp. 295-299 ◽  
Author(s):  
D. I. Demetrashvili ◽  
D. U. Kvaratskhelia ◽  
A. I. Gvelesiani
Keyword(s):  
Black Sea ◽  
Richardson Number ◽  
General Circulation ◽  
Wind Forcing ◽  
The Black Sea ◽  
Maximal Velocity ◽  
Cyclonic Vortex ◽  
Baroclinic Model ◽  
The Vertical Distribution ◽  
Potential Vortex

Abstract. Some results of simulation of the Black Sea circulation with consideration of forcing of different averaged wind types by using 3-D prognostic baroclinic model are presented. The results allow us to consider all depth of the sea basin consisting of some relatively homogeneous sub-layers. Within each of them general circulation processes practically do not change by depth, but essentially change from layer to layer. Such character of changeability interpreted by us as a steepness of the Black Sea general circulation takes place in majority cases of climatic atmospheric wind forcing. In the present paper results are analyzed on an example of forcing of January atmospheric cyclonic vortex with ~250 km diameter. Under such forcing the Ekman surface layer of ~12 m thickness is created. The cyclonic vortex formed in the east part of the Black Sea, which is Taylor-Proudman potential vortex with vertical cylindrical configuration, is described in detail. The vertical distribution of vortex characteristics are given in figures: Brunt-Väisälä frequency and Richardson number taken near the vortex wall with maximal velocity. The viable vortexes are characterized by introduced the universal Reynolds number Re•.

scholarly journals Climate Signals in the Black Sea From a Multidecadal Eddy-Resolving Reanalysis

2021 ◽  
Vol 8 ◽  
Author(s):  
Leonardo Lima ◽  
Stefania Angela Ciliberti ◽  
Ali Aydoğdu ◽  
Simona Masina ◽  
Romain Escudier ◽  
...  
Keyword(s):  
Data Assimilation ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Sea Level ◽  
Black Sea ◽  
General Circulation ◽  
Circulation Model ◽  
Ocean Modeling ◽  
Sea Surface ◽  
The Black Sea

Ocean reanalyses are becoming increasingly important to reconstruct and provide an overview of the ocean state from the past to the present-day. In this article, we present a Black Sea reanalysis covering the whole satellite altimetry era. In the scope of the Copernicus Marine Environment Monitoring Service, the Black Sea reanalysis system is produced 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, implemented for the Black Sea domain with a horizontal resolution of 1/27°× 1/36°, and 31 unevenly distributed vertical levels. The model is forced by the ECMWF ERA5 atmospheric reanalysis and climatological precipitation, whereas the sea surface temperature is relaxed to daily objective analysis fields. The model is online coupled to OceanVar, a 3D-Var ocean data assimilation scheme, to assimilate sea level anomaly along-track observations and in situ vertical profiles of temperature and salinity. Temperature fields present a continuous warming in the layer between 25 and 150 m, where the Black Sea Cold Intermediate Layer resides. This is an important signal of the Black Sea response to climate change. Sea surface temperature shows a basin-wide positive bias and the root mean square difference can reach 0.75°C along the Turkish coast in summer. The overall surface dynamic topography is well reproduced as well as the reanalysis can represent the main Black Sea circulation such as the Rim Current and the quasi-permanent anticyclonic Sevastopol and Batumi eddies. The system produces very accurate estimates of temperature, salinity and sea level which makes it suitable for understanding the Black Sea physical state in the last decades. Nevertheless, in order to improve the quality of the Black Sea reanalysis, new developments in ocean modeling and data assimilation are still important, and sustaining the Black Sea ocean observing system is crucial.

scholarly journals Spatial analysis of salinity distribution patterns in upper layers of the Black Sea

2020 ◽  
Vol 203 ◽  
pp. 03010
Author(s):  
Denis Krivoguz ◽  
Sergei Mal’ko ◽  
Anna Semenova
Keyword(s):  
Spatial Distribution ◽  
Black Sea ◽  
General Circulation ◽  
Saline Water ◽  
World Ocean ◽  
Distribution Patterns ◽  
The Black Sea ◽  
Marine Environment Monitoring ◽  
Monitoring Service ◽  
The Impact

Salinity is one of the most important factors that primarily determines the level of seawater’s density and, consequently, the movement of water masses in the World Ocean. Spatial distribution of the salinity in different layers of the Black Sea are associated with varying levels of water balance seasonal variability and, general circulation of Black Seas waters and in the surface layer has a seasonal structure. To study spatial distribution of salinity in upper layers of the Black Sea we’ve used data from Copernicus Marine Environment Monitoring Service, that were processed and aggregate by seasons and depth. We found that the most fluctuated layer is a top layer (up to 2.8 m) and the highest values Black Sea salinity reaches near the Bosporus Strait, where more saline water from the Sea of Marmara connected with fresher water of the Black Sea. Also we found that the impact of the river flows, mixing of the water, water regime of the sea decreasing with depth, so in the bottom of the upper layer the spatial fluctuation of the salinity is minimal and reaches about ±3‰, while in the depth of 2.8 m its reaches ±12-15‰.The lowest level of salinity through all of the upper layer (0-50 m) lays around the seashore and north-western part of the sea.

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