Effect of finely divided admixtures on the scattering of light in “pure” filtered water

We consider the problem of disagreement between the theoretical and experimental values of the spectral volume scattering function of “pure” filtered water. To explain this disagreement, we advance a hypothesis of existence of two-dimensional space correlations between the locations of a finely divided suspension in the liquid. We deduce analytic relations for the scattering of light in the approximation of statistically equilibrium distribution of particles over the surfaces of spheres randomly arranged in the medium. The experimental data on the volume scattering function of “pure” filtered water (the sizes of particles do not exceed 0.2 μm) are analyzed. The results of numerical analysis according to the model of spherical surface distribution of finely divided particles in water are in qualitative agreement with the spectral volume scattering function of filtered water. __________ Translated from Morskoi Gidrofizicheskii Zhurnal, No. 2, pp. 46–56, March–April, 2008.     

Specific features of the variability of atmospheric processes and hydrophysical fields near the west and southwest coasts of Crimea on time scales from interdiurnal to long-term

We present the results of analysis of the variability of hydrometeorological and hydrophysical fields near the west and southwest coasts of Crimea on scales varying from 1–100 days to 1–11 yr according to the data of long-term routine (4–8 h) observations performed at the coastal marine hydrometeorological stations. New methods of filtration and spectral analysis are used to reveal the characteristic time scales of variability including the quasiperiodic and periodic components and study the physical processes responsible for the indicated variability. Special attention is given to the analysis of correlation between the periodic variability of the fields in the atmosphere and in the coastal zone on different time scales. __________ Translated from Morskoi Gidrofizicheskii Zhurnal, No. 1, pp. 22–36, January–February, 2006.     

Investigation of the fields of concentration of the suspension on the northwest shelf of the Black Sea in the case of roiling of the bottom sediments by a moving cyclone

The processes of roiling of the bottom sediments, diffusion transport of the suspension, and its repeated sedimentation on the northwest shelf of the Black Sea caused by a moving cyclone are studied by using a numerical sigma-coordinate model. It is supposed that bottom sediments are formed by particles of the same type. We determine the regions of the most intense rise of the suspension, directions of its transport by the flows of water, and the vertical profiles of concentration of suspended bottom sediments in different regions. In particular, it is shown that the distribution of suspended substances at a distance of 1 m from the bottom reflects the location of the active and inactive centers of erosion. __________ Translated from Morskoi Gidrofizicheskii Zhurnal, No. 1, pp. 3–20, January–February, 2007.     

Summer dynamics of phytoplankton pigments and its correlation with the optical parameters of shelf waters in the Black Sea (2001–2002)

We study the space and time variations of the concentration of chlorophyll in the Black-Sea coastal zone (near Katsiveli) in summer 2001–2002. Typical vertical profiles of the pigments are presented. The relations between the concentration of chlorophyll and the optical parameters of seawater (including the Secchi depth, sea reflectance, effective wavelength of the upwelling radiation, and the vertical attenuation coefficient of light) are analyzed. The equations for the biological parameters of seawater and its optical characteristics are presented. __________ Translated from Morskoi Gidrofizicheskii Zhurnal, No. 3, pp. 36–51, May–June, 2006.     

Investigation of the biogeochemistry of methane and mechanisms of its transfer in the Black Sea

We demonstrate the importance of investigation of the behavior of methane as a source of energy and an element of the Black-Sea ecosystem affecting the global behavior of the climate. We describe the genesis of methane and the processes of its aerobic and anaerobic oxidation. An especially important biogeochemical and ecological role is played by the anaerobic oxidation of methane guaranteeing the formation of its effective sink inside the anaerobic zone and preventing its penetration into the atmosphere as a greenhouse gas. On the basis of the analysis of the experimental data available from the literature, we also discuss the principal regularities of the distribution of concentration of methane and its flows. It is shown that the formation of methane hydrates at the bottom in the abyssal part of the Black Sea and the events of jet gas release on the periphery of the basin can be regarded as the components of a single global process of gas release from the bottom of the Black Sea. We present estimates of the components of methane budget in the Black Sea. The results of simulation of the dynamics of methane bubbles and the processes of their gas exchange with the medium are analyzed. The data of hydroacoustic measurements are used to evaluate the distribution of methane bubbles in sizes and the mass transfer of methane through the ocean–atmosphere interface. Finally, we consider the methods of mathematical simulation of the distribution of methane in the ecosystem of the Black Sea. Translated from Morskoi Gidrofizicheskii Zhurnal, No. 5, pp. 40–56, September–October, 2008.     

Global surface layer salinity change detected by Argo and its implication for hydrological cycle intensification

We investigated changes in the global distribution of surface-layer salinity by comparing 2003–2007 Argo-float data with annual mean climatological surface-layer salinity data for 1960–1989 from the World Ocean Database 2005. The two datasets showed similar patterns, with low values in subpolar and tropical regions and higher values in the subtropics. The recent Argo data indicate that the contrast between low and high salinity has intensified in all areas except the subpolar North Atlantic. The intensified contrast of the surface layer salinity was maintaining for 2003–2007. Using a simple method, we attempted to estimate evaporation and precipitation changes on the basis of surface-layer salinity changes. The results show a high probability that the global hydrological cycle has increased in the past 30 years.     

Analysis of the Black-Sea climatic fields below the main pycnocline obtained on the basis of assimilation of the archival data on temperature and salinity in the numerical hydrodynamic model

We study model climatic temperature and salinity fields and the fields of currents in the 350–1000-m layer. The following specific features are revealed: Colder waters are observed in the regions with anticyclonic vorticity. At the same time, warmer waters are detected in the regions with cyclonic vorticity. This temperature effect can be explained by the elevation of temperature with depth below the main pycnocline. In the region of the Sevastopol anticyclone, at depths greater than 500 m, we observe a zone of cyclonic rotation of waters. Near the Caucasian coast, in the region of Gelendzhik, we reveal a narrow jet current existing at a depth of 350 m from March till July. Translated from Morskoi Gidrofizicheskii Zhurnal, No. 1, pp.3–15, January–February, 2009.     

Structure of the phytoplankton communities and primary production in the Ob River estuary and over the adjacent Kara Sea shelf

The material was collected in the Ob River estuary and over the adjacent shallow Kara Sea shelf between 71°14′0 and 75°33′0N at the end of September 2007. Latitudinal zoning in the phytoplankton distribution was demonstrated; this zoning was determined by the changes in the salinity and concentration of nutrients. Characteristic of the phytocenosis in the southern desalinated zone composed of freshwater species of diatom and green algae were the high population density (1.5 × 10⁶ cells/l), biomass (210 μgC/l), chlorophyll concentration (4.5 μg/l), and uniform distribution in the water column. High primary production (∼40 μgC/l/day) was recorded in the upper 1.5-m layer. The estuarine frontal zone located to the north contained a halocline at a depth of 3–5 m. Freshwater species with low population density (2.5 × 10⁵ cells/l), biomass (24 μgC/l), and chlorophyll concentration (1.5 μg/l) dominated above the halocline. Marine diatom algae, dinoflagellates, and autotrophic flagellates formed a considerable part of the phytocenosis below the halocline; the community characteristics were twofold lower as compared with the upper layer. The maximal values of the primary production (∼10 μgC/l per day) were recorded in the upper 1.5-m layer. The phytocenosis in the seaward zone was formed by marine alga species and was considerably poorer as compared with the frontal zone. The assimilation numbers at the end of the vegetation season in the overall studied area were low, amounting to 0.4–1.0 μgC/μgChl/h in the upper layer and 0.03–0.1 μgC/μgChl/h under the pycnocline.     

Generation of quasiinertial internal waves in the process of evolution of local perturbations in the ocean

Within the framework of a linear model of long waves in a two-layer ocean, we obtain the analytic solution of the problem of evolution of an axially symmetric initial displacement of the jump of density. In the process of adaptation of the fields, internal waves in the form of a decaying (in time) wave packet are emitted from the zone of initial perturbation. These waves are quasiinertial and their dispersion is conditioned by Earth’s rotation. We study the time evolution of the wave packet and the dependence of its characteristics on the width of the zone of initial perturbation and the depth of the jump of density. __________ Translated from Morskoi Gidrofizicheskii Zhurnal, No. 2, pp. 12–23, March–April, 2006.     

Intraannual and long-term variations of the carbonate system of the aerobic zone in the black sea

We provide an expert quality assessment of the data for 1932–1993 and used these data to perform the numerical analysis of the carbonate system of the aerobic zone in the Black Sea. The intraannual and long-term variations of the carbonate system are studied in the abyssal part of the sea for 1960–1993. We propose explanations of the intraannual variations of the analyzed system for various layers of the aerobic zone and reveal long-term variations of the pH values, total alkalinity, and the ratios of the components of the carbonate system. We discover and explain the observed increase in the concentrations of TCO₂ and CO₂ and the partial pressure of carbon dioxide pCO₂, as well as a decrease in pH values and the concentration of CO₃²⁻ in waters of the aerobic zone of the Black Sea.     

Investigation of the action of hygroscopic particles on a warm convective cloud from the results of numerical simulation

The results of a numerical simulation of the action of hygroscopic particles on a warm convective cloud with the purpose of obtaining additional precipitation are presented. The one-dimensional numerical model considered in this work describes the evolution of the cloud medium in the central part of an axisymmetric convective cloud at the specified height-variable velocity of the upward air flow which forms the cloud. Our model comprehensively describes microphysical processes in the cloud medium with the use of the kinetic equation for the size distribution of cloud droplets. This model makes it possible to obtain the spatiotemporal pattern of the cloud formation and development and to analyze regular features in the cloud evolution under the action of hygroscopic reagents. The cloud characteristics calculated with the use of this model correspond to the cloud parameters observed in natural conditions of the atmosphere. The process of precipitation stimulation by hygroscopic particles in convective clouds with vertical thicknesses of 2.5–4.5 km was analyzed on the basis of the results of numerical calculations. The results of calculations of the dependence of the intensity and total amount of precipitation on the vertical cloud thickness and parameters of particles introduced into the cloud are presented. It is shown that hygroscopic particles with root-mean-cube radii of 1–1.5 μm are the most effective for acting on warm convective clouds with the purpose of obtaining additional precipitation. In this case, the required reagent expenditure is 100–200 kg/km². The conditions necessary for obtaining the maximal positive effect of the action are elucidated.     

Biogeochemical evidence of large diapycnal diffusivity associated with the subtropical mode water of the North Pacific

A profiling float equipped with a fluorimeter, a dissolved oxygen (DO) sensor, and temperature and salinity sensors was deployed in the subtropical mode water (STMW) formation region of the North Pacific. It acquired quasi-Lagrangian, 5-day-interval time-series records from March to July 2006. The time-series distribution of chlorophyll showed a sustained and sizable subsurface maximum at 50–100 m, just above the upper boundary of the STMW, throughout early summer (May–July). The DO concentration in this lower euphotic zone (50–100 m) was almost constant and supersaturated in the same period, becoming more supersaturated with time. On the other hand, the DO concentration at 100–150 m near the upper boundary of the STMW decreased much more slowly compared with the main layer of STMW below 150 m, even though oxygen consumption by organisms was expected to be larger in the former depth range. The small temporal variations of DO in the lower euphotic zone and near the upper boundary of the STMW were reasonably explained by downward oxygen transport because of large diapycnal diffusion near the top of the STMW. Assuming that the oxygen consumption rate at 100–150 m was the same as that in the main layer of STMW and compensated by the downward oxygen flux, the diapycnal diffusivity was estimated to be 1.7 × 10⁻⁴ m² s⁻¹. Nitrate transport into the euphotic zone by the same large diffusion was estimated to be 0.8 mmol N m⁻² day⁻¹. All of the transported nitrate could have been used for photosynthesis by the phytoplankton; net community production was estimated to be 5.3 mmol C m⁻² day⁻¹.     

Basic regularities of the formation of “new” and regeneration production in the Black Sea

Based on the experimental data obtained in 1990–1993 by the method of isotopic tracers with the help of a stable isotope of nitrogen (¹⁵N), we establish basic regularities of the formation of “new” and regeneration production in the Black Sea and reveal the factors specifying their combination. It is shown that the rates of nitrate and ammonium uptake by microplankton vary from the minimum values in winter to the maximum values in summer. In the surface layer, the uptake of nitrates corresponding to the amount of “new” production in deep-water layers is equal to ∼ 50% (in winter) and ∼ 30% (in summer) of the total uptake of inorganic nitrogen compounds by microplankton. In the zone of photosynthesis, the average fractions of nitrates are equal to 31 ± 10% in winter and 41 ± 10% in summer. The minimum values of this parameter are attained in the middle of spring and in autumn. The fraction of “new” production (f-ratio) and the integral content of nitrates in the zone of photosynthesis are connected by a hyperbolic dependence. The period of cyclic transformations of nitrates in this zone decreases from several dozens of days at the beginning of winter to 12 h in the mid-spring. In summer, this period is equal, on the average, to one day. The average period of cyclic transformations of ammonium is equal to 15 ± 4 h in winter and 5 ± 3 h in summer. __________ Translated from Morskoi Gidrofizicheskii Zhurnal, No. 6, pp. 29–43, November–December, 2006.     

Loss Processes of Sinking Fecal Pellets of Zooplankton in the Mesopelagic Layers of the Antarctic Marginal Ice Zone

A time-series sediment trap deployment was carried out in the marginal ice zone (MIZ) of the Antarctic Ocean (64°42′ S, 139°58′E; sea depth of 2930 m), during the austral summer. Cylindrical fecal pellets were the predominant sinking particles at 537 m in the middle of January and most of them disappeared below that depth, the loss of which were 25.3 mg C m⁻² day⁻¹ in the depth range of 537–796 m. Small-sized sinking particles other than fecal pellets increased in that depth range. Analyses of fecal pellets for remnant DNA corresponding to 16S mitochondrial RNA and 28S ribosomal RNA suggested that the large cylindrical fecal pellets at 537 m were produced by Antarctic krill (Euphausia superba) and copepods. According to the presence of the DNA associated with sinking particles, E. superba fecal pellets rapidly disappeared below 537 m, while copepod fecal pellets still remained in the mesopelagic and bathypelagic layers. Small-sized amorphous sinking particles at 537 m also contained E. superba- and copepod-derived DNA. The abundance of trap-collected copepods (Oithona spp. and Oncaea spp.) which are known to be coprophagous increased at 796 m where many fecal pellets disappeared. We suggest that those rapidly sinking pellets were fragmented by copepods with intensified coprorhexy activity (fragmentation of fecal pellets) in the mesopelagic layers, reducing their sinking rates. These smaller and slower sinking particles can be important food sources for detritivorus or coprophagous animals in mesopelagic and bathypelagic layers in the MIZ. This revised version was published online in July 2006 with corrections to the Cover Date.     

A spectral model of underwater irradiance in the Black Sea

We develop a semiempirical spectral model of penetrating irradiance taking into account the biooptical characteristics of the Black Sea. The evaluation of the contributions of the principal optically active components to the total absorption of light in the sea shows that, in the short-wave range (400–500 nm), light is mainly absorbed by the dissolved organic matter (41–77%). The contribution of phytoplankton to the total absorption attains its maximum values (26–37%) in the abyssal part of the sea in the period of spring blooming of diatoms. In the coastal waters, the absorption of light by suspended nonalgae particles in summer is almost twice as intense (20–30%) as in the open sea (8–13%). The analysis of the sensitivity of our model shows that the absorption of light by dissolved organic matter is more significant for the estimation of the photosynthetically active radiation in the Black Sea than the concentration of pigments and backscattering of light by suspended particles. The comparison of the results of model computations with the data of measurements of the underwater irradiance reveals high accuracy of the proposed model.     

Analysis of the possibilities of aGALS-3 hydrophysical towed complex

We describe the characteristics of a towed complex used for measurements in the upper layer of the ocean under the conditions of periodic deepening and lifting (scanning) of a carrier with sensors connected with the ship by a weight-carrying cable of constant lengt. For a maximum scanning range of 0–200 m and a towing speed of up to 12 knots, the measurements were performed every 1.5–2.0 km. The minimum vertical scale of recorded temperature and conductivity inhomogeneities is 0.05–0.08 m. We present the results of measurements carried out by the towed complex in a section of the frontal zone in the north-east part of the Tropical Atlantic. Translated by Peter V. Malyshev and Dmitry V. Malyshev     

Magnetic expression of some major lineaments and Cretaceous quiet zone in the Bay of Bengal

 Magnetic data over the eastern continental margin of India and adjacent Bengal fan demarcate two major lineaments. A high amplitude N–S-trending lineation of the Cauvery offshore Basin corresponds to the offshore fragment of the 80°E lineament recorded onland. A N–S lineation of very high amplitude anomaly off Chilka lake considered as the possible northward extension of the 85°E ridge delineated, hitherto in Bengal Fan. A subdued magnetic anomaly zone is demarcated seaward of the continent–ocean boundary (COB) in the Bengal Fan. Over the northern Bengal Fan this zone is delineated east of 85°E lineation. This quiet zone might have evolved during the Early Cretaceous period of normal magnetic polarity between M0 and 34 (120–84 Ma) anomalies. Received: 6 April 1995 / Revision received: 3 September 1996     

Seasonal variability of geostrophic currents in the Atlantic Ocean according to the altimetry data

The monthly average values of the anomalies of the ocean level (according to the satellite data for 1992–2002) and the annual average dynamic heights (hydrological data) are used to compute the seasonal cycle of geostrophic currents on the surface of the Atlantic Ocean. It is shown that the west and east currents are intensified with a phase difference of several months. At the same time, their latitudinal displacements are quasisynchronous. A delay of the seasonal signal in the east-west direction of about 2–3 months (on the average) is typical of currents in the tropical zone of the Northern Hemisphere. On the contrary, in the South Atlantic, the seasonal signal propagates in the west-east direction and its phase delay can be as large as almost six months. __________ Translated from Morskoi Gidrofizicheskii Zhurnal, No. 3, pp. 60–71, May–June, 2006.     

Mesoscale structure of the fields of vertical velocity and vorticity of winds over the Black Sea

On the basis of a simple stationary linear model and a contemporary nonlinear model, we study the mesoscale characteristics of the fields of vertical velocity and vorticity of winds over the Black Sea. It is shown that, in the idealized case (without taking into account the coastal features), the temperature contrast between the land and the sea in both models leads to the formation of circulation cells in the coastal zone. However, the mountainous features prove to be the main factor affecting the process of circulation for the actual synoptic situations. We present the map of monthly average vorticity of the surface winds constructed according to the nonlinear mesoscale model with a resolution of 30 km for January 1996–2001. __________ Translated from Morskoi Gidrofizicheskii Zhurnal, No. 1, pp. 52–61, January–February, 2005.     

Peculiarities of the deep structure of the lithosphere in the northeastern part of the Indian Ocean

The seismicity of the northeastern part of the Indian Ocean in connection with the general structural peculiarities of the main tectonic structures of the bottom is presented. The three main ranges of higher seismic activity at the depths of 0–17, 20–27, and 32–35 km divided by aseismic layers are revealed. The seismic activity at depths of more than 35 km is almost not detected both for the ocean and for the Indian peninsula. The nature of the distribution of the seismicity as such in the lithosphere is discussed. Using the results of anomalous au]gravitational field transformations, the prolongation of the East Indian Ridge structure is revealed to 19 degrees north, while the relationship of the Afanasy Nikitin Rise and the 85th Degree Ridge is not reflected at the tranforms. In the Cocos Basin, the mutually perpendicular disturbance zones of northeastern and northwestern strike, as well as the point of their crossing, where the maximal number of earthquake foci are concentrated, are distinguished. A conclusion concerning the substantial disturbance of the strength properties of the lithosphere in this zone as a consequence of the geodynamical processes, which are accompanied by fracture tectonics, is reached.