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 The Effect of Dust Transport on the Concentration of Chlorophyll-A in the Surface Layer of the Black Sea

2021 ◽  
Vol 11 (10) ◽  
pp. 4692
Author(s):  
Alla V. Varenik ◽  
Darya V. Kalinskaya
Keyword(s):  
Surface Layer ◽  
Chlorophyll A ◽  
Black Sea ◽  
Inorganic Nitrogen ◽  
Atmospheric Precipitation ◽  
The Black Sea ◽  
Background Concentration ◽  
Dust Transport ◽  
Chlorophyll A Concentration ◽  
Atmospheric Depositions

This paper focuses on the atmospheric dust transport effect on the changes in chlorophyll-A concentration in the Black Sea surface layer. In order to assess the input of nutrients with atmospheric precipitations at the Crimean coast of the Black Sea, the collected samples were analyzed for the content of inorganic nitrogen, phosphates, and silicon. The samples were taken into a wet-only sampler and into a permanently open one, to assess the effect of dust on the nutrients concentration in dry depositions. Cases of multi-fold excess of the nutrients content in the open sampler collected precipitation over that in the wet-only sampler were identified. For such high concentration cases, the 7-day back-trajectories analyses was carried out using the model of the international network AERONET and the HYSPLIT model. The results of our research showed that the influx of nutrients with the atmospheric depositions can result in increasing of chlorophyll-A concentration in 11–36% in the surface layer of the Black Sea. After atmospheric depositions, concentration of phosphates in the surface layer can increase more than five times compared with the background concentration. The increase of silicon concentration can reach 30%. The influx of atmospheric precipitation containing significant amounts of nutrients into the bay can shifts the Redfield ratio compared with background value up to three times.

Seasonal variability of the Black Sea chlorophyll-a concentration

2005 ◽  
Vol 56 (3-4) ◽  
pp. 243-261 ◽  
Author(s):  
Peter C. Chu ◽  
Leonid M. Ivanov ◽  
Tatyana M. Margolina
Keyword(s):  
Chlorophyll A ◽  
Black Sea ◽  
Seasonal Variability ◽  
The Black Sea ◽  
Chlorophyll A Concentration

scholarly journals Bio-Optical Characteristics of the Black Sea Coastal Waters near Sevastopol: Assessment of the MODIS and VIIRS Products Accuracy

2021 ◽  
Vol 37 (2) ◽  
Author(s):  
E. Yu. Skorokhod ◽  
T. Ya. Churilova ◽  
T. V. Efimova ◽  
N. A. Moiseeva ◽  
V. V. Suslin ◽  
...  
Keyword(s):  
Chlorophyll A ◽  
Black Sea ◽  
Coastal Waters ◽  
Light Absorption ◽  
Ecological Monitoring ◽  
Optically Active ◽  
The Black Sea ◽  
Active Components ◽  
Chlorophyll A Concentration

Purpose. The purpose of the work is to evaluate accuracy of the satellite products for the coastal waters near Sevastopol, reconstructed by the standard algorithms based on the MODIS and VIIRS (installed at the artificial Earth satellites Aqua and Terra, and at Suomi NPP, respectively) data. Methods and Results. In situ sampling was carried out at the station (44°37'26" N and 33°26'05" E) located at a distance of two miles from the Sevastopol Bay. The chlorophyll a concentration was measured by the spectrophotometric method. The spectral light absorption coefficients by optically active components were measured in accordance with the current NASA protocol. The spectroradiometers MODIS and VIIRS Level 2 data with spatial resolution 1 km in nadir around the in situ station (44°37'26"±0°00'32" N and 33°26'05"±0°00'54" E) were used. The satellite products were processed by the SeaDAS 7.5.3 software developed in NASA. The research showed that the standard NASA algorithms being applied to the MODIS and VIIRS data, yielded incorrect values of the optically active components’ content in the Black Sea coastal waters near Sevastopol as compared to the data of in situ measurements in the same region: the satellite-derived “chlorophyll a concentration” was on average 1.6 times lower in spring, and 1.4 times higher in summer; the contribution of phytoplankton pigments to total light absorption at 443 nm was underestimated in 8.7 times; the light absorption by colored detrital organic matter was overestimated in 2.2 times. Conclusions. The NASA standard algorithms are inapplicable to calculating bio-optical indices in the coastal waters of the Black Sea near Sevastopol since they provide incorrect values of the satellite products (Ca-s, aph-s(443) and aCDM-s(443)). Operative ecological monitoring based on satellite data requires development of a regional algorithm taking into account the seawater optical features in the region and in the coastal zone, in particular.

scholarly journals Comparison of chlorophyll a concentration values retrieved from MODIS-Aqua spectroradiometer with the results of measurements in the coastal waters of the Black Sea near Sevastopol

2019 ◽  
Vol 4 (4) ◽  
pp. 53-61
Author(s):  
E. Yu. Skorokhod ◽  
T. V. Efimova ◽  
N. A. Moiseeva ◽  
E. A. Zemlianskaia ◽  
T. Ya. Churilova
Keyword(s):  
Chlorophyll A ◽  
Black Sea ◽  
Coastal Waters ◽  
Field Measurements ◽  
The Black Sea ◽  
Optical Monitoring ◽  
Chlorophyll A Concentration ◽  
Low Concentrations ◽  
Satellite Product ◽  
Significant Underestimation

The results of the comparison of the values of the standard satellite product “Chlorophyll a Concentration” recovered from MODIS-Aqua satellite with the results of field measurements in the coastal waters of the Black Sea near Sevastopol from 2009 to 2019 as a part of regular bio-optical monitoring have been presented. Differences between seasons in the nature of the error of the standard satellite product “Chlorophyll a Concentration” using the standard NASA algorithm were established: in spring, a significant underestimation of the values of the standard satellite product “Chlorophyll a Concentration” (up to 2.1 times) at high chlorophyll a concentrations was noted according to the results of the full-scale measurements, and in summer a significant overestimation of the values (up to 3.8 times) at low concentrations was noted. Throughout the year, depending on the season, the error in determining the standard satellite product “Chlorophyll a Concentration” on average varied from ±24 % to ±51 %. To increase the accuracy of determining the chlorophyll a concentration with remote sensing, it is necessary to use a regional approach.

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