scholarly journals Warmer winter causes deepening and intensification of summer subsurface bloom in the Black Sea: the role of convection and self-shading mechanism

2020 ◽  
Author(s):  
Elena A. Kubryakova ◽  
Arseny A. Kubryakov
Keyword(s):  
Black Sea ◽  
Mixed Layer Depth ◽  
Light Attenuation ◽  
The Black Sea ◽  
Layer Depth ◽  
Argo Data ◽  
Strong Light ◽  
Subsurface Chlorophyll Maximum ◽  
Winter Convection

Abstract. Large differences in the vertical distribution of chlorophyll-a concentration (Chl) in a year with cold and warm winter are observed in the Black Sea on the base of Bio-Argo data. Stronger winter nutrient flux from deeper isopycnal layer in cold 2017 caused an increase of Chl in the upper 40-meter layer observed throughout the whole year – from February to October, with a maximum exceeding 1.3 mg/m3 in February-May of 2017. In warm 2016 with weaker winter convection maximum of Chl during winter-spring in this layer was only about 0.8–0.9 mg/m3. However, the increase of Chl in 2017 led to strong light attenuation in the upper layer and a decrease of euphotic layer depth due to the self-shading mechanism. In 2016 with weaker bloom irradiance penetrated to a 40–70 m layer, below the maximum winter mixed layer depth (40–50 m) and reached the upper layer of nitroclyne, which was not affected by winter mixing. As a result, in warm 2016 the subsurface chlorophyll maximum deepens and Chl in deeper layers was on 0.2–0.6 mg/m3 higher than in 2017. The maximum difference (0.6 mg/m3) was observed during a summer seasonal peak of irradiance due to the largest increase of light attenuation in 2017. As a result, the column-averaged yearly values of Chl in warm 2016 and cold 2017 were comparable. These results demonstrate that the effect of self-shading largely compensates the role of winter convective entrainment of nutrients and causes the deepening of Chl subsurface maximum in warmer years.

scholarly journals Interannual Variability of the Wind-Wave Regime Parameters in the Black Sea

2020 ◽  
Vol 27 (5) ◽  
Author(s):  
P. N. Lishaev ◽  
V. V. Knysh ◽  
G. K. Korotaev ◽  
◽  
◽  
...  
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Black Sea ◽  
Mixed Layer ◽  
Mixed Layer Depth ◽  
Sea Surface ◽  
Temperature Fields ◽  
The Black Sea ◽  
Layer Depth ◽  
Upper Mixed Layer

Purpose. The investigation is aimed at increasing accuracy of the temperature field reconstruction in the Black Sea upper layer. For this purpose, satellite observations of the sea surface temperature and the three-dimensional fields of temperature (in the 50–500 m layer) and salinity (in the 2.5–500 m layer) pseudo-measurements, previously calculated by the altimetry and the Argo floats data, were jointly assimilated in the Marine Hydrophysical Institute model. Methods and Results. Assimilation of the sea surface temperature satellite observations is the most effective instrument in case the discrepancies between the sea surface and the model temperatures are extrapolated over the upper mixed layer depth up to its lower boundary. Having been analyzed, the temperature profiles resulted from the forecast calculation for 2012 and from the Argo float measurements made it possible to obtain a simple criterion (bound to the model grid) for determining the upper mixed layer depth, namely the horizon on which the temperature gradient was less or equal to ≤ 0.017 °C/m. Within the upper mixed layer depth, the nudging procedure of satellite temperature measurements with the selected relaxation factor and the measurement errors taken into account was used in the heat transfer equation. The temperature and salinity pseudo-measurements were assimilated in the model by the previously proposed adaptive statistics method. To test the results of the sea surface temperature assimilation, the Black Sea hydrophysical fields were reanalyzed for 2012. The winter-spring period (January – April, December) is characterized by the high upper mixed layer depths, well reproducible by the Pacanowski – Philander parameterization, and also by the low values (as compared to the measured ones) of the basin-averaged monthly mean square deviations of the simulated temperature fields. The increased mean square deviations in July – September are explained by absence of the upper mixed layer in the temperature profiles measured by the Argo floats that is not reproduced by the Pacanowski – Philander parameterization. Conclusions. The algorithm for assimilating the sea surface temperature together with the profiles of the temperature and salinity pseudo-measurements reconstructed from the altimetry data was realized. Application of the upper mixed layer depths estimated by the temperature vertical profiles made it possible to correct effectively the model temperature by the satellite-derived sea surface temperature, especially for a winter-spring period. It permitted to reconstruct the temperature fields in the sea upper layer for 2012 with acceptable accuracy.

scholarly journals The Black Sea Mixed Layer Depth Variability and Its Relation to the Basin Dynamics and Atmospheric Forcing

2019 ◽  
Vol 35 (5) ◽  
Author(s):  
A. A. Kubryakov ◽  
V. N. Belokopytov ◽  
A. G. Zatsepin ◽  
S. V. Stanichny ◽  
V. B. Piotukh ◽  
...  
Keyword(s):  
Black Sea ◽  
Mixed Layer ◽  
Mixed Layer Depth ◽  
The Black Sea ◽  
Atmospheric Forcing ◽  
Layer Depth

scholarly journals Warmer winters causes an increase of chlorophyll-a concentration in deeper layers: the opposite role of convection and self-shading on the example of the Black Sea

2020 ◽  
Author(s):  
Elena A. Kubryakova ◽  
Arseny A. Kubryakov
Keyword(s):  
Chlorophyll A ◽  
Black Sea ◽  
Light Attenuation ◽  
The Self ◽  
Lower Amount ◽  
The Black Sea ◽  
Chlorophyll A Concentration ◽  
Warm Winter ◽  
Chlorophyll Maximum ◽  
Subsurface Chlorophyll Maximum

Abstract. Winter vertical entrainment of deep waters determines not only the amount of nutrients in the upper layers, but also the light conditions in it, through the self-shading mechanism. In this paper, we use Bio-Argo data to demonstrate significant differences in the vertical distribution of chlorophyll-a concentration (Chl) in the Black Sea between a year with cold winter (2017) and a year with warm winter (2016). Stronger vertical entrainment of nutrient-rich waters from deeper isopycnal layers in cold 2017 caused an increase of Chl in winter up to 0.6–0.7 mg/m3 compared to a warm winter of 2016, when Chl was only 0.4–0.5 mg/m3. Further, during almost the whole year from February to October Chl in the upper 0–40 m layer of cold 2017 year was on 0.1–0.2 mg/m3 higher than in 2016. This rise of Chl in 2017 led to an increase in light attenuation due to the self-shading effect. In contrast, in warm 2016 with a lower amount of nutrients light attenuation decreased and the irradiance reached deeper isopycnals layers with a higher amount of nutrients. As a result, in warm 2016 the subsurface chlorophyll maximum deepens and the values of Chl in 40–60 m layers were significantly higher than in 2017. The maximum positive difference in this layer (0.5 mg/m3) was observed during a summer seasonal peak of irradiance due to the largest increase of light attenuation in the summer of 2017. As a result, the column-averaged yearly values of Chl in warm 2016 and cold 2017 were comparable. However, in the year with intense winter mixing upper layers are more productive, while in the year with low winter vertical mixing, subsurface chlorophyll maximum widens and reaches deeper layers. These results show that the observed long-term warming may lead to the continuous deepening of the subsurface chlorophyll maximum in the ocean.

scholarly journals Reconstructing the Black Sea Hydrophysical Fields Including Assimilation of the Sea Surface Temperature, and the Temperature and Salinity Pseudo-Measurements in the Model

2020 ◽  
Vol 36 (5) ◽  
Author(s):  
P. N. Lishaev ◽  
V. V. Knysh ◽  
G. K. Korotaev ◽  
◽  
◽  
...  
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Black Sea ◽  
Mixed Layer ◽  
Mixed Layer Depth ◽  
Sea Surface ◽  
Temperature Fields ◽  
The Black Sea ◽  
Layer Depth ◽  
Upper Mixed Layer

Purpose. The investigation is aimed at increasing accuracy of the temperature field reconstruction in the Black Sea upper layer. For this purpose, satellite observations of the sea surface temperature and the three-dimensional fields of temperature (in the 50–500 m layer) and salinity (in the 2.5–500 m layer) pseudo-measurements, previously calculated by the altimetry and the Argo floats data, were jointly assimilated in the Marine Hydrophysical Institute model. Methods and Results. Assimilation of the sea surface temperature satellite observations is the most effective instrument in case the discrepancies between the sea surface and the model temperatures are extrapolated over the upper mixed layer depth up to its lower boundary. Having been analyzed, the temperature profiles resulted from the forecast calculation for 2012 and from the Argo float measurements made it possible to obtain a simple criterion (bound to the model grid) for determining the upper mixed layer depth, namely the horizon on which the temperature gradient was less or equal to 0.017°C/m. Within the upper mixed layer depth, the nudging procedure of satellite temperature measurements with the selected relaxation factor and the measurement errors taken into account was used in the heat transfer equation. The temperature and salinity pseudo-measurements were assimilated in the model by the previously proposed adaptive statistics method. To test the results of the sea surface temperature assimilation, the Black Sea hydrophysical fields were reanalyzed for 2012. The winterspring period (January – April, December) is characterized by the high upper mixed layer depths, well reproducible by the Pacanowsci – Philander parameterization, and also by the low values (as compared to the measured ones) of the basin-averaged monthly mean square deviations of the simulated temperature fields. The increased mean square deviations in July – September are explained by absence of the upper mixed layer in the temperature profiles measured by the Argo floats that is not reproduced by the Pacanowsci – Philander parameterization. Conclusions. The algorithm for assimilating the sea surface temperature together with the profiles of the temperature and salinity pseudo-measurements reconstructed from the altimetry data was realized. Application of the upper mixed layer depths estimated by the temperature vertical profiles made it possible to correct effectively the model temperature by the satellite-derived sea surface temperature, especially for a winter-spring period. It permitted to reconstruct the temperature fields in the sea upper layer for 2012 with acceptable accuracy.

scholarly journals The Black Sea Mixed Layer Depth Variability and Its Relation to the Basin Dynamics and Atmospheric Forcing

2019 ◽  
Vol 26 (5) ◽  
Author(s):  
A. A. Kubryakov ◽  
V. N. Belokopytov ◽  
A. G. Zatsepin ◽  
S. V. Stanichny ◽  
V. B. Piotukh ◽  
...  
Keyword(s):  
Black Sea ◽  
Mixed Layer ◽  
Mixed Layer Depth ◽  
The Black Sea ◽  
Atmospheric Forcing ◽  
Layer Depth

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

Georgian Historians and the Ideological Confrontation Between East and West

2021 ◽  
Vol 30 (1) ◽  
pp. 153-164
Author(s):  
George Gotsiridze
Keyword(s):  
Soviet Union ◽  
Cultural Values ◽  
Black Sea ◽  
The Black Sea ◽  
Black Sea Region ◽  
The Soviet Union ◽  
Long Time ◽  
Science And Culture ◽  
East And West

The work, on the one hand, highlights the mission of Europe, as an importer of knowledge, which has for centuries been the center of gravity for the whole world, and, on the other hand, the role of the Black Sea Region, as an important part of the Great Silk Road, which had also for a long time been promoting the process of rap-prochement and exchange of cultural values between East and West peoples, until it became the ‘inner lake’ of the Ottoman Empire, and today it reverts the function of rapproching and connecting civilizations. The article shows the importance of the Black Sea countries in maintaining overall European stability and in this context the role of historical science. On the backdrop of the ideological confrontation between Georgian historians being inside and outside the Iron Curtain, which began with the foundation of the Soviet Union, the research sheds light on the merit of the Georgian scholars-in-exile for both popularization of the Georgian culture and science in Eu-rope and for importing advanced (European) scientific knowledge to Georgia. Ex-change of knowledge in science and culture between the Black Sea region and Europe will enrich and complete each other through impact and each of them will have unique, inimitative features.

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