Purpose. The purpose of this study is to substantiate and practically apply a new method for fast (0.01 s) recording of capillary wave parameters under natural conditions. Methods and Results. The method is based on recording an image of a thin laser beam incidence on the sea surface. The radiation scattered in the water is refracted at the rough interface and is recorded by a video camera located at the side. The beam image deviations are proportional to the surface slopes at the point of radiation exit. The largest slopes, exceeding 30 degrees, are characteristic of capillary waves; this makes the method particularly effective for recording them. It has become possible to record waves with an amplitude of 30 & micro;m from a distance of 5-8 m. When intense capillary ripples occur below the point of beam incidence on the surface, a light "skirt" is formed, the width of which grows with increasing slope. The distribution of the scattered-light intensity in the cross-section of the light "skirt" makes it possible to calculate the slope distributions for each frame or the probability function for a given time interval. The developed method for the operational determination of the distribution of capillary wave slopes is applied to study the capillary structure of various areas of sea waves, namely the crests and troughs. It is established that the dispersion of capillary slopes in the troughs is significantly lower than that on the crests, which is consistent with previously reported data. Conclusions. A new method for remote measurement of capillary wave slopes on the sea surface is proposed; it permits measurements to be carried out over surface areas of 10 & times; 10 cm in 0.01 s. The given example shows that at a significant wave height (1.1 +/- 0.1) m and a wind speed of (7.4 +/- 0.5) m/s, the average dispersion of the capillary component was 0.0256 on the crests and 0.008 in the troughs. The advantage of the method is that it makes it possible to carry out measurements in a wide range of weather conditions, both during the night and the day.
Purpose. The work is purposed at studying the changes in distribution of water thermohaline characteristics in the main pycnocline and below (100-400 m) in the northern and northeastern parts of the Black Sea. Methods and Results. The data of hydrological measurements (conductivity, temperature and depth) obtained by the scientists of Marine Hydrophysical Institute, RAS in the 20 cruises of R/V "Professor Vodyanitsky" in the northern and northeastern parts of the Black Sea in 2016-2021 were used. A gradual increase in water temperature and salinity below the main pycnocline was revealed; it extended up to the 16.9 kg/m3 (similar to 370 m) isopycne. For the indicated period, the worming constituted 0.14 degrees C for isopycne 16.3 kg/m3 (similar to 150 m), 0.09 degrees C for isopycne 16.5 kg/m3 (similar to 180 m), and 0.02 degrees C for isopycne 16.9 kg/m3 (similar to 370 m). During the same period, the salinity increase within the range of isopycnes 15.9- 16.1 kg/m3 amounted to 0.03 PSU. The changes in temperature and salinity have resulted in the rise of isopycnic surfaces. The 15.8 kg/m3 isopycne rose from the 106 m horizon in 2016 to the 96 m one in 2021, and the 16.1 kg/m3 isopycne - from the 126 m horizon to the 115 m one. The rates of isopycne rises within the range 15.8-16.3 kg/m3 were maximum and amounted to 3-3.5 m/year. Conclusions. In the last decade, the trends in increasing temperature and salinity in the upper 200-300 m layer are typical of the whole Black Sea area. Besides, this phenomenon is observed much deeper, up to the similar to 400 m depth. The intensity of warming decreases with depth. A comparison with the data from earlier measurements has shown that just during the indicated period, significant changes, particularly evident since 2018, took place. In general, the changes observed in the Black Sea thermohaline structure below the main pycnocline can be induced by the climatic changes, as well as by the increased inflow of the Mediterranean Sea waters (also transformed due to general climate warming) through the Bosphorus Strait.
Purpose. The purpose of the study is to obtain quantitative characteristics of the spatial variability of heavy metal concentrations in suspended matter, as well as to assess the relationship between this variability and the hydrological and hydro chemical characteristics of the northern Black Sea waters. Methods and Results. Data on the volume and mass concentrations of heavy metals (Pb, Zn, Ni, Fe, Cr, V, Co) in the Black Sea suspended matter obtained during the 133rd cruise of R/V Professor Vodyanitsky were used. A total of 44 water samples were collected at 33 stations and processed. The data on metal content were obtained using X-ray fluorescence analysis. Conclusions. The volume and mass concentrations of the analyzed metals in suspended matter varied spatially within two orders of magnitude. Elevated volume concentrations of heavy metals were observed in the northeastern part of the study area, whereas lower values were typical in its southwestern part. The spatial variability in mass concentrations of heavy metals exhibited a more complex pattern. Elevated values of Pb, Zn, and Ni were noted in the deep part of the sea, while lower values were observed in the coastal area. Elevated values of Fe and V were typical of the shelf section from Cape Meganom to Cape Chauda, and lower values were typical of the deep-sea part. Higher and lower concentrations of Cr and Co were observed both on the shelf and in the deep-sea part of the study area. In the deep part of the sea, the mass and volume concentrations of metals both increased and declined with depth. In the upper part of the thermocline, the volume (Pb, Ni, Fe, Cr, V, Co) and mass (Fe, Cr, V, Co) concentrations of most heavy metals rose by a factor of 1.1-47.1. On the shelf in the near-bottom layer, the volume (Zn, Fe, Cr, V, Co) and mass (Zn, Fe, V, Co) concentrations of most heavy metals also grew by a factor of 1.1-137. Principal component analysis showed that the spatial variability of volume and mass concentrations of Fe, V, Co, and Cr is related to the impact of the lithogenic factor (coastal abrasion, inflow of the Sea of Azov waters, and atmospheric transport), the variability of Zn and Ni is driven by the influence of the biogenic factor (phytoplankton production, adsorption on organic matter), and the Pb variability is related to the hydrodynamic factor (mixing depth variability).
Purpose. The purpose of the work is to develop a regional statistical methodology for deriving the Black Sea thermohaline structure based on satellite data on sea surface temperature and sea level. Methods and Results. The study included in-situ temperature and salinity data, daily anomalies of altimetry sea level (0.125 degrees grid) and sea surface temperature (0.05 degrees grid) at the L4 processing level for 1993-2023, as well as a climatic array of the Black Sea thermohaline fields for 1950-2023. To reproduce the hydrological fields, the method of multiple linear regression was used. It made it possible to determine statistical relationships between the physical parameters of the sea surface layer and the values of temperature and salinity at depths up to 300 m. In order to take into account longterm changes, corrections to modern climatic values and linear trends were applied. Validation of the methodology through comparison of the calculated 30-year reanalysis and the in-situ measurement data showed that the total root-mean-square errors of temperature and salinity reconstruction were 0.4 degrees C and 0.2 psu, respectively, which corresponded to an average normalized error of 0.4, indicating a good result for a statistical method. The errors were highest in the seasonal thermocline and permanent halocline layers, where the amplitude of mesoscale noise increases sharply. The best values of calculation accuracy were observed in the cyclonic gyres in the central sea, while the worst ones were found in the sea periphery (Batumi anticyclonic eddy and Rim Current zone), and, as for salinity, on the north-western shelf. A comparison of the error values of several arrays of the Black Sea thermohaline field reanalyses showed that the accuracy of this method is close to that of the CMEMS arrays calculated using modern hydrodynamic models and complex data assimilation methods. Some indicators relating to salinity show that, despite the absence of an in-situ data assimilation algorithm in this version, the regression model even exceeds the accuracy values of the specified reanalyses. Conclusions. A method for operational diagnosis and reanalysis of the Black Sea 3-dimensional thermohaline structure based on satellite data and using regression relationships has been developed. It provides a sufficiently good level of errors in temperature and salinity reconstruction while minimizing computational resources. The methodology implies the application of regular open-source data, requires no high-performance equipment (which is of practical importance), and can be regarded as a quick and effective instrument for assessing the state of the marine environment. The regression algorithm can also be used in operational data assimilation procedures in forecast models when in-situ oceanographic data are absent.
Purpose. The aim of this work is to investigate real cases of upwelling observed off the southern coast of Crimea in late May 2010 using a coupled mesoscale model. Methods and Results. The coupled mesoscale ocean-atmosphere model NEMO-OASIS-WRF (NOW) with a 1 km resolution was used. The three areas of reduced sea surface temperature observed in satellite images near Yalta, near Feodosia, and in the Kerch Strait in late May 2010 were reproduced. It was found that at a depth of 10 m, the decrease in water temperature was not limited to these three areas, but also took place along the whole coast from Sevastopol to Kerch. The modeling results made it possible to examine in detail two upwelling events, namely those in the Yalta and Feodosia areas. The main advantage of dynamic regionalization in coupled modeling has been demonstrated: the atmospheric block of the coupled model reproduces the fine-scale structure of the surface wind field in the Yalta area, in particular, the intensification of coastal wind over the sea up to significant values of 12-15 m/s, which is absent in the atmospheric reanalysis data. Conclusions. It is established that the coastal upwelling near Yalta can be classified as wind-driven, as its development was accompanied by an offshore wind. The Feodosia upwelling is of the Ekman type and is caused by the southwesterly alongshore winds. The vertical structure of both upwelling events on cross sections normal to the coastline is shown. The revealed main difference in the upwelling structures is as follows: in the Yalta upwelling, the water uplift was concentrated in a narrower zone directly adjacent to the coast, whereas in the Feodosia upwelling, the main water uplift took place at some distance from the coast, and the uplift velocity did not reach such high values as in the Yalta case. It is shown that the SST decrease near Yalta and Feodosia occurred precisely due to upwelling, as a decrease in surface water temperature was accompanied by a simultaneous increase in salinity and coincided in time with the intensification of the corresponding coastal wind velocity component directed normal to the coast in the Yalta area and parallel to the coast in the Feodosia region. The obtained results have demonstrated that the application of a modern ocean-atmosphere model in mesoscale modeling makes it possible to reproduce and examine in detail the structure and development of real upwelling events near the southern coast of Crimea, which would be impossible using only observational data.
