Use of a problem-oriented database for statistical analysis of the hydrochemical characteristics of the redox layer of the Black Sea

A problem-oriented database (PODB) was developed for the statistical analysis of the hydrochemical characteristics of the redox layer of the Black Sea. The paper describes the features of the PODB, including the algorithm of interpolation and the location of the levels of the appearance and disappearance of hydrochemical parameters (the so-called onset levels) based on Akima’s spline. The application of the PODB allowed us to obtain a series of biogeochemical estimates, in particular, (1) to reveal the constancy of the vertical gradients of the hydrochemical parameters at selected density levels; (2) to calculate the seasonal variability of the degree of manifestation of the phosphate minimum in the near-shore and open sea areas; and (3) to calculate the interannual variability of the level of the disappearance of the hydrogen sulfide, ammonium, total manganese, and methane, as well as the oxygen content in the cold intermediate layer, and to find out their relations with the climatic variations.     

Seasonal evolution of the mediterranean water propagation in the north Atlantic

The Climatic variability of the seasonal water exchange in the Strait of Gibraltar and the spatial structure of the tongue of the Mediterranean Waters (MW) in the Atlantic Ocean are studied. The analysis is based on the results of a numerical experiment using a 3D ocean circulation model developed at the Institute of Computational Mathematics (ICM RAS) with a resolution of the dataset over the latitude and longitude equal to 0.25 degree. The seasonal evolution of the salinity and density fields is calculated in the North Atlantic (from 20 °S, including the Mediterranean Sea) and in the Arctic Ocean (including the Bering Sea). The comparison of the model estimates with the results of field observations demonstrated good agreement. The transport of the MW into the Atlantic is close to the observed data (during the year, it varies from 1.8 Sv in the winter to 0.9 Sv in the summer). The complex pattern of the currents in the region of the MW spreading is confirmed. The alternating character of the saline MW tongue at the 1000-m level is shown for the first time. It is found that the zones of maximum salinities in the open part of the ocean coincide with the main trajectories of migration of MW lenses and the regions of their decomposition.     

Tortonian-Pleistocenic oceanic features in the Southern Tyrrhenian Sea: magnetic inverse model of the Selli-Vavilov region

We show the magnetic model of the Selli-Vavilov region. The Selli Line is known as the northwestern edge of the southern Tyrrhenian Basin. The tectonic evolution of the Tyrrhenian Basin is dominated by a Tortonian-Quaternary extension through the eastward movement of the Apennine subduction system. This migration has generated a diffuse stretching of the continental crust with the emplacement of new oceanic material. This latter occurred in several localized zones where the eastward retreating of the Ionian subduction system produced a strong depletion of the crust with formation of basins and correlated spreading. Nowadays the presence of oceanic crust is confirmed through direct drilling investigation but a complete mapping of the oceanic crustal distribution is still lacking. The Selli-Vavilov region shows a differentiated crustal setting where seamount structures, the oceanic basement portions and continental crust blocks are superimposed. To this aim, a 2D inversion of the magnetic data of this region was conducted to define buried structures. The magnetic susceptibility pattern was computed by solving the least squares problem of the misfit between the predicted and real data for separated wavebands. This method produced two 2D models of the high and low frequency fields of the Selli-Vavilov region. The two apparent susceptibility maps provide different information for distinct ranges of depth. The results of the inversions were also combined with seismic data of the Selli region highlighting the position of the highly magnetized buried bodies. The results confirm a role for the Selli Line as a deep crustal boundary dividing the Sardinian passive domain from the easternmost active region where different oceanic structures are located. The Selli Line has worked as a detachment fault system which has moved eastward. Finally, the Selli-Vavilov region may be interpreted as a tectonic result due to a passive asymmetrical rift occurred between the Tortonian and Pliocene.     

Isotopic,trace element and nutrient characterization of coastal waters from Ubatuba inner shelf area,south-eastern Brazil

Stable isotopes, tritium, radium isotopes, radon, trace elements and nutrients data were collected during two sampling campaigns in the Ubatuba coastal area (south-eastern Brazil) with the aim of investigating submarine groundwater discharge (SGD) in the region. The isotopic composition (δD, δ¹⁸O, ³H) of submarine waters was characterised by significant variability and heavy isotope enrichment. The stable isotopes and tritium data showed good separation of groundwater and seawater groups. The contribution of groundwater in submarine waters varied from a few % to 17%. Spatial distribution of ²²²Rn activity concentration in surface seawater revealed changes between 50 and 200 Bq m⁻³ which were in opposite relationship with observed salinities. Time series measurements of ²²²Rn activity concentration in Flamengo Bay (from 1 to 5 kBq m⁻³), obtained by in situ underwater gamma-spectrometry showed a negative correlation between the ²²²Rn activity concentration and tide/salinity. This may be caused by sea level changes as tide effects induce variations of hydraulic gradients, which increase ²²²Rn concentration during lower sea level, and opposite, during high tides where the ²²²Rn activity concentration is smaller. The estimated SGD fluxes varied during 22–26 November between 8 and 40 cm d⁻¹, with an average value of 21 cm d⁻¹ (the unit is cm³/cm² per day). The radium isotopes and nutrient data showed scattered distributions with offshore distance and salinity, which implies that in a complex coast with many small bays and islands, the area has been influenced by local currents and groundwater–seawater mixing. SGD in the Ubatuba area is fed by coastal contaminated groundwater and re-circulated seawater (with small admixtures of groundwater), which claims for potential environmental concern with implications on the management of freshwater resources in the region.     

Experimental estimation of the coefficient of vertical turbulent exchange in a stratified layer of the black sea near the continental slope

On the basis of the data of field measurements, we present the results of numerical analysis of the intensity of vertical turbulent exchange in stratified layers of the Black Sea in the region of the shelf–continental-slope boundary depending on the local stratification. The experiments were carried out within the framework of the GEF/BSERP and Black Sea-2004 international projects. The data were obtained by using a probing version of the Sigma-1 measuring complex. In processing the data of measurements, we apply a procedure of evaluation of the coefficient of vertical turbulent diffusion depending on the external conditions based on the analysis of the spectra of the gradient of temperature fluctuations. For the two studied regions of the shelf, the coefficients of turbulent exchange turn out to be much higher (by about an order of magnitude) than for the open sea under similar conditions. This can be explained by the specific features of the bottom topography affecting the dynamics of quasiinertial waves playing to role of the main causes of small-scale mixing and vertical diffusion. Translated from Morskoi Gidrofizicheskii Zhurnal, No. 6, pp. 14–24, November–December, 2008.     

Statistical structure of the large-scale fields of temperature and salinity in the Black Sea

In order to reconstruct the large-scale temperature and salinity fields by the method of optimal interpolation of the archival data, we compute the correlation functions and analyze the space and time variations of the statistical structure of the fields. On the sea surface, the thermohaline fields are spatially inhomogeneous. Thus, the correlation functions are anisotropic in the region of the northwest shelf and close to isotropic in the inner parts of the sea. The values of correlation length vary from season to season. In the layer of pycnocline, the temperature and salinity fields are anisotropic. In the zonal direction, the correlation length is 2–3 times greater than in the meridional direction. The indicated anisotropy becomes stronger in the winter season and weaker in the summer season as a consequence of the seasonal variability of large-scale circulation. We study the dependence of the error of reconstruction of the fields by the method of optimal interpolation on the form of approximation of the correlation functions with regard for anisotropy. __________ Translated from Morskoi Gidrofizicheskii Zhurnal, No. 1, pp. 51–65, January–February, 2008.     

Modeling of hydrodynamics and transport processes in the Dnieper–Bug Estuary

A numerical model of baroclinic circulation based on the use of a double sigma coordinate system is presented and its application to the simulation of flows and temperature and salinity fields in the Dnieper-Bug Estuary is described. The model reproduces the salinity and temperature fields surveyed in 1998. The results of simulations reveal the existence of a global influence of the relatively narrow and deep ship channel (through which Black-Sea waters can penetrate deep into the estuary) on the transport processes. Translated from Morskoi Gidrofizicheskii Zhurnal, No. 6, pp. 66–77, November–December, 2008.     

Vertical structure of the field of current velocities in the northwest part of the Black Sea based on the <Emphasis Type="Italic">LADCP</Emphasis> data for May 2004

The profiles of absolute current velocity obtained by using a lowered acoustic doppler current profiler (LADCP) are presented. In the course of the BSERP-3 expedition, the measurements were carried out in the regions of the Rim Current, anticyclonic eddy, and northwest shelf. In the core of the Rim Current, a unidirectional motion of waters is traced in layers below the main pycnocline down to depths greater than 500 m. Its characteristic velocity can be as high as 0.08 m/sec. It is shown that the direct action of the eddy is detected in the shelf region at distances larger than 20 km from the outer edge of the shelf in the zone bounded by an isobath of 100 m. The formation of multilayer vertical structures in the field of current velocities is revealed in the region of interaction of the anticyclonic eddy with irregularities of the bottom on the side of the shelf. A two-layer structure of currents with specific features in the layer of formed seasonal pycnocline is observed in the region of the shelf down to an isobath of 100 m. The profiles of the moduli of vertical shears of currents averaged over the casts ensemble are presented for the abyssal and shelf parts of the sea. It is shown that the shears induced by the geostrophic currents and wave processes in the region of the main pycnocline are comparable. Below the pycnocline, the shears are mainly determined by the wave processes. Translated from Morskoi Gidrofizicheskii Zhurnal, No. 6, pp. 25–37, November–December, 2008.     

Population ecology of the endangered Himalayan Yew in Khokhan Wildlife Sanctuary of North Western Himalaya for conservation management

The Himalayan Yew （Taxus baccata subsp, wallichiana） is an endangered native high value medicinal plant of the Himalayan Region. The several medicinal properties of the bark and leaves of this species have increased its risk of extinction due to pressures for utilization. It is also subjected to harvest for fuelwood. The species does not regenerate well from seed and that is another risk factor. The objective of this research was to investigate the population ecology of the species as a foundation for its conservation. Six forest communities in the Khokhan Wildlife Sanctuary where the species is present were sampled. The abundance of the species, impacts of harvesting and its current regeneration patterns indicate that it may soon be extirpated from the Sanctuary. A plan for conserving the remaining sub-populations is presented. It could provide a template for conservation in other locations where the species is at risk.