Fine vortex columns on the shelf in the area of bottom convection influence

This paper analyzes the results of investigations into extremely large releases of current velocities registered by an acoustic Doppler profiler during experiments performed on the Hawaii shelf. An integral analysis of the variability of current fields relies on the profile data of current velocities, temperature, and acoustic-scattering layers. Based on these investigations, we proposed a hypothesis stating that the small-scale variability of currents in profiler data is conditioned by the passage of fine vortices emerging in the outflow and rise of freshened waters from a subsurface sink near the shelf edge. To confirm this hypothesis on the emergence mechanism of the observed releases of current velocities, we conducted a mathematical simulation of the response that the Doppler meter has to the passage of fine vortex, which revealed a good agreement between model calculations and experimental data. Similar phenomena were also found in the Gelendzhik Bay of the Black Sea.     

Fine vertical structure of currents and hydrological elements in the Black Sea

Data on the fine vertical structure of currents and hydrological elements in the Black Sea, obtained through the use of a hydrophysical OLT profiler, are examined. Vertical exchange coefficients are evaluated, whose distribution is characterized by the occurrence of minima in the seasonal pycnocline and main halocline, a maximum in the core of the cold intermediate layer (CIL), and relatively steady values within the 300–500 m layer. The vertical exchange coefficient values, are consistent with the data acquired through other techniques, and the profiles of this parameter vertically are more detailed.Translated by Vladimir A. Puchkin.     

Using a lowered acoustic Doppler current profiler for measuring current velocities in the Black Sea

The results obtained with the use of a lowered acoustic Doppler current profiler (LADCP) are presented. The use of the LADCP from a vessel was the first in the history of the study of the Black Sea. The measurements were carried out in the northeastern Black Sea under the auspices of the Black Sea Ecosystem Recovery Program (BSERP) in May 2004. The effect of the computation parameters on the quality and accuracy of the calculations of velocity profiles was studied. It was shown that the use of optimal parameters and reliable navigation data and setting the instrument as close to the bottom as possible could essentially enhance the accuracy of the measurements. The current velocity calculations from the LADCP data were compared with the data on the vessel drift under calm weather. The accuracy of the calculations reached 6–8 cm/s. Recommendations on the choice of the optimal parameters for processing the data on the current velocity are presented.     

Vertical turbulent exchange in the Black Sea pycnocline and its relation to water dynamics

Estimates of vertical turbulent diffusion coefficient (K _t ) in the Black Sea pycnohalocline have been obtained from data of simultaneous observations of seawater temperature, salinity, density, and horizontal current velocity, obtained in the northeastern part of the Black Sea during 2013–2014 with a moored Aqualog profiler. A Munk and Andersson (1948) type parameterization, adapted for the Black Sea environment, is proposed for calculating K _t . Strong short-period (several days) variability of turbulent exchange is revealed, induced by vertical shear variations of the current velocity.     

Possible manifestations of underwater mud volcanoes based on results of sonar investigations in region of Taman Peninsula

This paper presents the results of three-dimensional acoustic seabed mapping in the region of the Taman Peninsula in the Black Sea using an interferometric side-scan sonar and an acoustic profiler. Mapping has revealed underwater objects identified as manifestations of underwater mud volcanism. Detailed analysis of sonar images of the relief and seabed profiles in the region of the objects has confirmed the original hypothesis.     

Methodical aspects of the application of acoustic Doppler current profilers in the Black Sea

For the first time, an acoustic Doppler current profiler (ADCP) produced by the RDI is used in the water area of the Black Sea in the lowered mode. This direction in the application of acoustic Doppler current profilers is now in the stage of development and verification of various procedures of measurements with subsequent data processing and enables one to get the distributions of current velocities down to depths of 1000–6000 m depending on the modification of the instrument. We describe the procedures of measurements performed with the help of the ADCP in the lowered mode in the course of an expedition and the stages of processing of the primary data based on the experience of application of similar acoustic current profilers at the Marine Hydrophysical Institute of the Ukrainian National Academy of Sciences accumulated in the 1980s. We generalize the experience of application of ADCP under the hydrological conditions of the Black Sea, propose the algorithms of data processing, present the profiles of absolute current velocity at several stations, compare these profiles with the geostrophic velocities, and determine the deep-water structure of the field of currents in a shelf-open-sea section made along 31.17°E. __________ Translated from Morskoi Gidrofizicheskii Zhurnal, No. 4, pp. 31–48, July–August, 2006.     

Possibilities of X-band nautical radars for monitoring of wind waves near the coast

We present the results of development and testing of a coastal X-band radar system for monitoring wind waves and currents at the Black Sea (near Gelendzhik) created on the basis of nautical radars. Radar measurements of wave heights were validated by data from a wave buoy and a moored acoustic Doppler current profiler (ADCP). The conditions for successful radar measurements of waves in the coastal environment have been determined. It was shown that a radar with an aperture 1° could successfully measure wave heights at a distance of 1.2 km from the radar, when waves arrive at an angle of ±31° to the main sensing direction. In this case, for wave height measurements, the correlation coefficient between the radar and independent data is 0.82 and the standard deviation is 0.26 m.     

Characteristics of inertial oscillations according to the experimental measurements of currents on the Russian shelf of the Black Sea

The analysis of inertial oscillations on the Gelendzhik shelf of the Black Sea is presented. Spectral characteristics of the current fields are studied based on the measurements taken by the acoustic Doppler current profiler. Strong variability of the inertial oscillation hodographs at variations in the background shear current and diverse forms of inertial oscillations measured at a fixed point at various values of the shear current are revealed. The relation between the passage of the multidirectional jets and the trains of inertial oscillations inside the jets in the studied region are established.     

Hydraulic calculations of postglacial connections between the Mediterranean and the Black Sea

A series of simple hydraulic calculations has been performed to examine some of the questions associated with the reconnection of the Black Sea to the Mediterranean through the Turkish Strait System during the Holocene. Ryan et al.’s catastrophic flood scenario, whereby the erosive power of the marine in-fluxes, initiated after eustatic sea level reached the sill depth, opened up the Bosphorus, allowing saline water to pour into the Black Sea and filling it on a short time scale, is examined. The calculations show that although it might be possible to fill the palaeo-Black Sea within the order of a decade, a 1–2 year filling time scale is not physically possible. A hydraulic model is also used to examine the more traditional connection hypothesis of (near-)continuous freshwater outflow from the Black Sea, with a slowly increasing saline inflow from the Mediterranean beginning around 8–9 kyr BP. The model considers two forms for the structure of the Bosphorus: a shallow sill as seen today and a deep sill associated with no sediments filling the 100 m gorge above the bedrock in the strait. Sensitivity experiments with the hydraulic model show what possible strait geometric configurations may lead to the Black Sea reaching its present-day salinity of 18 psu. Salinity transients within the Black Sea are shown as a function of time, providing for values that can be validated against estimates from cores. To consider a deep, non-sediment-filled Bosphorus (100 m deep), the entry of Mediterranean water into the Sea of Marmara after 12.0 kyr BP is examined. A rapid entry of marine water into the Sea of Marmara is only consistent with small freshwater fluxes flowing through the Turkish Strait System, smaller than those of the present day by a factor of at least 4. Such a small freshwater flux would lead to the salinification of the Black Sea being complete by an early date of 10.2–9.6 kyr BP. Thus the possibility of a deep Bosphorus sill should be discounted.     

Coastal upwelling in the Gelendzhik area of the Black Sea: Effect of wind and dynamics

Long series data of a thermistor chain in the Black Sea coastal zone near Gelendzhik were analyzed. A thermistor chain installed 1 km offshore and at a depth of 22 m. There are full and incomplete upwelling events observed. The study of upwelling genesis based on: wind speed data from the NCEP/CFSR reanalysis and Gelendzhik weather station, velocity and direction of coastal currents measured by ADCP profiler moored on the bottom near the thermistor chain. Over the whole observation period (warm seasons of 2013–2015), more than 40 events of upwelling were registered four of them were full upwellings, when presence of under-thermocline water was observed near the sea surface. For every upwelling event, conditions prior to the changes in thermic structure, were analyzed. It is found that full upwelling generally occur under synergistic wind and current forcing. Fairly strong forcing of one of these factors is sufficient for partial upwelling to occur.     

Influence of the dynamics of currents on the hydrophysical structure of the waters and the vertical exchange in the active layer of the Black Sea

An analysis of the data of measurements of the fine structure and microstructure fluctuations of hydrophysical fields in the upper 200-m layer of the Black Sea carried out using CTD profilers and a Baklan free falling microstructure and turbulence profiler revealed the existence of a positive correlation between the intensity of the fine structure and microstructure fluctuations and the dynamics of the currents. On the other hand, the level of the fine structure and microstructure fluctuations reflects the rate of the vertical turbulent exchange. It was shown that, in the case of the absence of the Black Sea Rim Current (BSRC) jet or clearly manifested mesoscale eddy structures, the vertical turbulent exchange in the pycnocline is weak, while, in the opposite case, it is stronger. The results obtained support the supposition that the interbasin dynamics play an important role in the maintenance of the rate of small-scale mixing in the pycnocline and halocline and provide the vertical transport of dissolved oxygen from the cold intermediate layer into the deeper layers of the sea.     

Effects of fine grain size on distribution of Mn in shallow and deep water Black Sea sediments: A comparison between oxic and anoxic depositional environments

The uppermost 5–6 cm of the sediments (between 8 and 2248 m water depths) were studied to understand the effects of varying redox conditions on the Mn distribution in the recent sediments of the Black Sea. It was found that most Mn concentrations are consistent with the average abundance in crustal and/or sedimentary rocks. There exist no important differences between Mn concentrations in oxic (shallower water; <70 m) and anoxic (deeper water; 120 m) sediments. Previously reported Mn-enrichment above the Black Sea oxic/anoxic interface, due to the peculiar redox cycling, shows no significant contribution of Mn to the bottom sediments. A marked relationship between total Mn concentrations and clay/mud contents at shelf depth along the southern Black Sea margin indicates increased accumulation of Mn in association with the fine-grained particles and eastward water circulation.     

Study of long-term variations in the Black Sea fields using an interdisciplinary physical and biogeochemical model

Using an interdisciplinary three-dimensional physical and biogeochemical model developed for the Black Sea, the long-term evolution of marine dynamics and ecosystem is investigated. The hydrophysical fields were calculated from a model of Black Sea circulation with assimilation of hydrographic survey and satellite measurement data from 1971 to 2001. The circulation model reproduces well processes of various scales in both space and time (particularly the seasonal course and interannual variability of main hydrophysical fields). The resulting flow fields are then used to calculate the long-term evolution of the components of the lower level of the food chain in the Black Sea ecosystem. The biogeochemical model used in the calculations is based on the nitrogen cycle and includes a parameterization of the main biological and chemical interactions and processes in the upper layer of the Black Sea. The numerical experiments indicated that the biogeochemical component of the model rather successfully reproduces the main features and evolution trends in the Black Sea ecosystem for the period under consideration: the growth in the phytoplankton biomass during eutrophication and changes in seasonal cycles of the main ecosystem components. Also, the hydrophysical processes were shown to be important for a reliable reproduction of long-term changes in the ecosystem.     

6000 m电缆传输式CTDC剖面仪

6 000 m电缆传输式CTDC剖面仪是“十五”863计划支持的海洋专用CTD技术项目之一。研制成功的6 000 m电缆传输式CTDC剖面仪可以基本覆盖全部海洋范围,使我国的CTD测量技术跻身世界先进水平。文中介绍了6 000 m电缆传输式CTDC剖面仪的工作原理、实验室和海上试验情况,通过与海鸟SBE 917CTD所获取的数据资料进行对比和分析,找出了存在的问题和今后努力方向。     

The westward intrusion of south Pacific water at the western tip of the New Guinea Island

From the eastern Indonesian cruise from November 14 to 23, 2007, CTD (conductivity, temperature, depth profiler) /ADCP (acoustic Doppler current profiler)casting and seawater sampling were done at 25 stations around Waigeo Island near New Guinea Island. It was found overall westward intrusion of the south Pacific waters into the Seram Sea and southward spreading of the north and south Pacific waters into the Seram Sea. There is westward residual flow along the channel between Waigeo and New Guinea within upper 200 m with the maximum speed up to 50 cm/s, and much weaker eastward flow in the lower layer (< 10 cm/s) due to blocking by the shallow sill at the west of the Dampier Strait. The abrupt change of bottom topography induces active horizontal and vertical mixing which results in a three-layered current system with a major through-flow of -0.99 Sv (Sv = 10 6 m 3 /s) into the Seram Sea; the transports in the upper and the lower layers are -1.14 Sv and -0.24 Sv (westward), respectively, and in the middle there is a return flow with the transport of +0.39 Sv (eastward).     

Climatic investigations of the Black Sea using hydrological observations

Results of numerical experiments on the hydrodynamic diagnosis and adaptation of the Black Sea climatic hydrological fields are briefly summarized. The principal features of the water dynamics for each season are discussed. The intra-annual variability of the Black Sea rim current is indicated, along with the existence of an array of anticyclonic eddies at its periphery and anticyclonic vorticity below the halocline in the central basin where a flow, opposite in direction to the surface flow, is generated at large depths.Translated by Vladimir A. Puchkin.     

Origin and abundance of marine litter along sandy beaches of the Turkish Western Black Sea Coast

Beach debris abundance was estimated from surveys on 10 beaches of the Turkish Western Black Sea Coast. Debris was collected from 20 m long transects during four different seasons; sorted and categorized by type, usage and origin. Litter density varied from 0.085 to 5.058 items m⁻². Debris was mainly composed of unidentifiable small size (2–7 cm) plastic pieces and beverage-related litter such as bottles and bottle caps. About half of the labeled litter was of foreign origin, including 25 different countries, 23% of which are in the Black Sea region.The south-western Black Sea Coast seems to receive foreign litter from two main sources: land-based debris from the neighboring countries and seaborne debris due to international shipping. Standardized methodology and indicators need to be designated all over the Black Sea basin in order to quantify and qualify coastal litter pollution, monitor compliance with MARPOL and develop regionally effective mitigation measures.     

Radioactive isotopes of caesium in the waters and near-water atmospheric layer of the Black Sea

The concentrations of¹³⁷Cs and¹³⁴Cs were measured using the sorption method in the waters of the Black Sea during 1986–1987. An inhomogeneous character of the contamination of the surface waters in the Black Sea due to the Chernobyl disaster is shown. The subsequent migration and redistribution of caesium radionuclides in the various seasons of the year were studied. The amount of¹³⁷Cs and¹³⁴Cs in the upper 50 m layer was estimated. The results of measuring the concentration of caesium radionuclides in the near-water atmospheric layer over the Black Sea and Mediterranean Sea in 1986–1987 are also reported.Translated by Mikhail M. Trufanov.     

Vertical Structure of Currents in Northern Black Sea,October 2016

The paper presents the results of an analysis of hydrological data obtained on cruise 89 of the R/V Professor Vodyanitskii from September 30 through October 19, 2016, in the central area of the northern Black Sea. Currents were measured using a lowered acoustic Doppler current profiler (LADCP) to a depth of 350 m. Examples of the current velocity profiles and conditional density at individual stations are presented. The averaged characteristics of the vertical current structure in the seasonal and permanent pycnoclines are discussed. The isopycnally averaged kinetic energy (KE) demonstrates an almost linear dependence on the conditional density (σ_θ). In the seasonal pycnocline, EK = 0.2–0.013σ_θ; in the permanent pycnocline, EK = 0.12–0.007σ_θ. An interpretation is given for the variability of the kinetic energy with depth. It is shown that the maxima of the averaged vertical shear profile correspond to the occurrence depth of the seasonal and permanent pycnoclines. The mean Richardson number has a value of ~10 in the upper sea layer and decreases with depth, assuming a value of ~3 at the 300 m horizon. The estimate for the vertical turbulent diffusion coefficient from the simplified model shows its increase with depth.